Paediatric Abdomen

Techniques and Applications


Standard two view supine + erect/cross-table lat or L decubitus. Don’t tend to do erect for younger pts. SB dificult to differentiated from LB due to less developed hastra/valvulae conniventes, impossible to tell in neonates. Additional prone view gas moves into more posterior structures (from transverse and sigmoid colon -> ascending and descending colon, rectum).

Micturating Cysto-Urethrogram (MCU)

(Voiding cystourethrogram, VCUG). Urograffin 76% 50mL/Saline 200mL. 8Fr or 5Fr feeding tube catheterisation (if labial adhesions give dioestral cream beforehand), urine specimen. AP plain, AP early filling (to exclude ureterocoele) and filled bladder, oblique R&L filled bladder (VUJ, VUR 1), micturating x 3 (boys oblique, girls AP), post AP incliding kidneys. PU bleed almost always due to recent/current infection. If dilatation or risk of VUR give ABs prior. If study shows VUR give stat dose (if not already given), double dose 3/7 then prophylactic daily (<6/12 0.25mL/kg cotrimoxazole Trisul/Deprim). Oral midazolam 0.5mg/kg max 12mg if required.

Nuclear/scintigraphic cystogram has less radiation and is more sensitive, but less anatomical detail.

Barium Swallow/Meal

Performed to exclude anatomical reason for excessive reflux rather than exclusion of GOR, hence provokation not required. Barium Poliber liquid (diluted 1/2 with water, older 2/3) except risk of perforation/leak (Visipaque 1/3 tastes better), or risk of obstipation/neurological impt (Poliber 1/4). NBM 4-8hrs prior (depending on age). Supine if <16yo (less movement). GOR, pain, vomiting – AP & lat distended oesophagus (esp GOJ), AP&lat DJ flexure (esp pain/vomiting, need 1st pass), supine AP stomach. Stridor/vascular ring/fistula – R&L lat distended oesophagus, AP. Haematemasis/melena – >7yo as per adult. Contrast tubogram – tip in oesophagus, patient prone, to check for TOF.

Small Bowel Follow Through (SBFT)

(Upper GI series, UGI). Oral or NG contrast while supine (easier to suck). AP then R lat oesophagus. Wait until contrast pools in antrum > pylorus > D1 and D2, demonstrate pylorux and duodenum coursing posteriorly. Supine, image as contrast -> DJ and proximal jejunum. If turned too early, not enough contrast to pass to jejunum (so turn R lat again), but if to late then contrast may -> distal jejunum obscuring visualisation of DJJ. L oblique, imaging gas-filled antrum and bulb. Spot views of nondilated jejunum, GOR.

Contrast Enema

Water soluble (<6/12 Omnipaque 1/3, >6/12 Urografin 50mL/water 300mL) via non-balloon-tip catheter. Barium not used as can make evacuation of meconium pugs/meconium ileus more difficult, water-soluble enema may be therapeutic. Ba may be used for polyps. Contraindications include perforation, meconium peritonitis.

Renal Ultrasound

Prone renal length more accurate than supine.



0-1 month

  • Duodenal atresia/stenosis/web, annular pancreas
  • Midgut malrotation/volvulus, Ladd bands
  • Ileal atresia
  • Meconium ileus
  • Small left colon syndrome
  • Hirshuprung disease

1-5 months

  • Hernias

5/12 to 3yrs

  • Intussusception


  • Perforated appendicitis
  • Adhesions
  • Crohn’s disease

Hypopharyngeal/upper oesophageal obstruction is uncommon. Includes cricopharyngeal spasm from neurologic dysfunction (eg Chiari malformation, cerebral palsy) or inflammation from reflux.

Oesophageal obstruction:

  • Congenital atresia/stenosis – faulty tracheal-oesophageal separation, with cartilage remnants in oesophageal wall. Small diverticula at stenosis.
  • Oesophageal web/diverticulum
  • Foreign body
  • ‘Congenitally’ short oesophagus with intrathoracic stomach from chronic foetal hiatus hernia with GOR and oesophageal stricture -> shortening.
  • Extrinsic compression (cysts, neoplasms, vascular)
  • Achalasia (uncommon)
  • Epidermolysis bullosa – hereditary, inflammatory skin and mucosal lesions healing with fibrosis

Gastric obstruction (NB large gas filled stomach commonly normal in infants, also seen with prostaglandins). Spilling/regurgitation/spitting up common and normal, occasionally GOR; pathology suggested by failure to thrive, respiratory problems.

  • Atresia/antral diaphragm – Gastric atresia usually at level of pyloris, thought from vascular insult in utero. May be diaphragm/membrane (web if incomplete). Secondary to inflammatory sticture in congenital epidermolysis bullosa.
  • Duplication cyst – best seen on USS as sonolucent with walls of mucosal and muscular layers
  • Pylorospasm – reactive to insult to mucosa or muscle contraction from other stress eg milk allergy, PUD. US persistent contraction of antropyloric region, poor emptying of liquids. Mild muscular thickening (<3mm), greater than this is only transient.
  • Hypertrophic pyloric stenosis
  • Volvulus – uncommon; idiopathic or associated with hernia, eventeration or asplenia syndrome. Organoaxial (around long axis) or mesoaxial (around line perpendicular to cardiopyloric line. May be acute emergency or chronic.
  • Microgastria – associated with other GI atresias, VACTERL syndrome, polysplenia/asplenia syndromes.
  • Gastric tumours – uncommon, include neonatal gastric teratoma
  • Gastric bezoar, lactobezoar

Duodenal obstruction. Gas passes from stomach to SB in first hrs. If stomach and duodenal bulb distended with none distal -> ‘double bubble’ sign (atresia or annular pancreas). Rarely small amount of gas distally if web/stenosis or anomalous Y configuration of hepatopancreatic duct (upper limb > pre-atretic, lower limb > post-atretic duodenum). Obstruction at D3/4 from diaphragm, malrotation/volvulus or band.

  • Atresia/stenosis/diaphragm
  • Annular pancreas
  • Duodenal band
  • Midgut volvulus
  • Haematoma
  • Duplication cyst
  • Neoplasm – duodenal (rare), pancreatic, liver
  • Peptic ulcer disease (rare)

Small bowel obstruction – usually congenital in neonate/infant, acquired in older. Neonate most common ileal atresia and meconium ileus; difficult to determine SBO from LBO on AXR, enema better for localisation. In older children, take AAIIMM against SBO.

  • Meconium ileus
  • Atresia/stenosis
  • Adhesions
  • Appendicitis (perforated)
  • Incarcerated inguinal hernia
  • Intussusception
  • (Malrotation with volvulus)
  • Meckel diverticulum
  • Crohns disease – thickened involved SB wall. Chronic appendiceal abscess, Tb, lymphoma, Yersinia.
  • Posttraumatic haematoma/stricture

Colonic obstruction. Congenital more common than acquired.

  • Meconium plug syndrome
  • Hirschsprung disease
  • Functional megacolon
  • Ectopic/imperforate anus
  • Colon atresia/stenosis
  • Inflammation – Perforated appendicitis, Crohn disease. Strictures from UC and necrotizing enterocolitis smooth, single or multiple; strictures also in CF.
  • Volvulus – uncommon, more in bedridden and neurologically impaired.
  • Trauma – battered child syndrome or MVA
  • Neoplasm (uncommon)

Gastrointestinal Bleeding

  • Peptic ulcer disease
  • Enterocolitis – necorotising enterocolitis, milk allergy, Hirschsprung disease, Crohn’s disease, ulcerative colitis
  • Haemorrhagic gastritis of the newborn
  • Anal fissures
  • Bleeding disorders
  • Henoch-Schonlein purpura – vasculitis of unknown aetiology affecting skin, GIT, joints, kidneys. 1/2 have crampy abdo pain ± PR bleed. Multifocal transmural thickening, incraesed vascularity.
  • Haemolytic uraemic syndrome
  • Juvenile inflammatory polyps – commonly sigmoid and rectum.
  • Meckel diveticulum – ~80cm proximal to ileocaecal valve. Ectopic gastric/pancreatic tissue in 20-30% causing ulceration, haemorrhage, perforation. Tc-99m localises to gastric mucosa. May also cause intussusception
  • Intussusception
  • Portal vein thrombosis
  • Duplication cysts
  • Colonic vascular malformations

Upper Gastrointestinal Tract

Oesophageal Atresia and Tracheo-Oesophageal Fistula (TOF)

Atresia is faulty separation of foregut in early gestation, usually at junction of proximal amd middle 1/3 oesophgus with a noncanalised cord. Usually associated with VACTERL syndrome (Vertebral anomalies, Anal atresia, Cardiovascular anomalies, Tracheoesophageal fistula, Esophageal atresia, Renal, Limb defects/radial array) or trisomy 21. Distended gas-filled pharyngeal/oesophageal pouch, may put pressure on trachea -> focal tracheomalacia. Associated with tracheo-oesophageal fistula (fibrous band or diverticula), usually extending from just above carina to distal pouch, allowing air to enter GIT (occ large volumes). TOF uncommonly from trachea to proximal pouch, or both proximal and distal segments; rarely without associated atresia (H-type fistula). May have oesophagael-spine communication from fibrous band, neurenteric cyst, fistula. Diagnosed with CXR, or if required contrast swallow/tubogram, occasionally echo. Tx thoracotomy contralateral to arch. Complications of repair include stricture (40%), leak (20%, suggested by large extrapleural fluid collection) and recurrent fistula (5-10%), oesophageal dysmotility, GOR.

Gastro-Oesophageal Reflux (GOR) and Hiatus Hernia (HH)

GOR is primary (chalasia, lax GO spincter) or secondary to gastric outlet obstruction (more severe; eg pylorospasm, pyloric stenosis, gastric diaphragm, gastric ulcer). Diagnosed with 24h oesophageal PH monitoring (indirect, cumbersome), nuclear reflux study (sensitive) Ba swallow (anatomic info), or US. Peptic oesophagitis associated with GOR ± HH.

Oesophagitis and Stricture

Herpes and Candida are uncommon, more in immunocomprimised.

  • Peptic (GOR) – usually lower 1/3, more if severe/Barretts. Wall thickening, lack of normal peristalsis, tertiary contractions, ulcers (deep or superficial), incomplete relaxation of cricopharyngeus. Strictures uncommon Cx, usually short, irregular or smooth, may mimic achalasia.
  • Caustic ingestion – extensive burns, possible perforation. Contrast usually not indicated acutely, later for ?stricture. Acids usually cause more superficial injury (stricure uncommon). Lodged disc battery leaks alkaline -> burns to mucosa and submucosa. Caustic stricture from ingested alkaline (eg NaOH, KOH/lye – long, irregular) or lodged batteries/medication (eg aspirin, tetracycline – focal).
  • Viral eg Herpes – small superficial ulcers (best seen with double contrast), diffuse or focal, may cause intense spasm with severe dysphagia.
  • Monilial/Candida – mucosal irregularity with intesnse spasm causing pseudodiverticula.
  • Eosinophilic – associated with asthma.

Hypertrophic Pyloric Stenosis

Muscle depleted of various components -> uninhibited contraction, increased blood flow (muscle and mucosa). Projectile, bile-free emesis, usually 1/52-3/12, M:F 3-4:1, 1:300-900. Palpable RUQ ‘olive’. Higher risk with FHx, Turner syndrome, trisomy 18. Acquired pyloric stenosis in adults from antral gastritis or peptic ulcers close to the pylorus. If pyloric stenosis is highly suspected then USS; if not classic Hx/Ex then UGI for ?stenosis or other pathology. Hypertrophied pyloric muscle in fixed spasm more than stomach wall; >3mm thick, elongated pyloric canal >15mm long. Little fluid passes, should be monitored during study. Tangentially 6:00 and 12:00 more echogenic than 3:00 and 9:00 (more muscle fibre interfaces). Atypical only 2-3mm thick with persistent spasm (normal 1.5mm), may be treated medically. Gastric distension with peristaltic waves (caterpillar sign) and mottled retained contents. On UGI delayed gastric emptying, if passes into duodenum -> string sign (elongated narrowed channel) or double-track sign (puckered, more than one apparent lumen), shoulder sign (indenting contrast-filled antrum), mushroom sign (indenting base of duodenal bulb), beak sign (beaked entrance of pylorus). Barium should be aspirated from stomach via NG to avoid lung aspiration.

Duodenal Atresia, Stenosis, Web/Diaphragm and Annular Pancreas

Spectrum of disease, complete or partial obstruction <3/7, many have combination. Many duodenal atresias have component of annular pancreas. Annular pancreas almost always associated with intrisnic duodenal stenosis.

Duodenum most commonly intestinal atresia/stenosis, at ampulla of Vater. Associated with Down syndrome (30%), other intestinal atresias, biliary anomalies, CHD, VACTERL. ‘Double-bubble’ sign of stomach and proximal duodenum with no gas distally is diagnostic of atresia. Stenosis is associated with distal gas.

Duodenal web/diaphragm/intraluminal diverticulum obstructing membrane with pin-sized hole in centre, may stretch downstream with a wind-sock configuration on UGI with rounded tip and thin surrounding radiolucent halo (mucosa). 20% associated with malrotation.

Gastritis, Duodenitis, Enteritis

  • Gastritis – peptic disease, Helicobacter or Campylobacter causing superficial ulcerations, delicate oedematous cobblestone mucosa. Milk allergy, vomiting and bleeding cause antropyloric muscle spasm. Prominent inflammation/thickening may cause gastric outlet obstruction.
  • Duodenitis – usually peptic disease-ith ulcer crater occasionally seen. Bleeding more common than adults.
  • Viral gastroenteritis – fluid-fillled loops, mildly thickenined mucosa, may cause extensive gaseous distension.
  • Crohn’s disease (regional enteritis) – usually terminal ileum, rarely proximal SB, stomach or oesophagus. Variable length narrowed, irregular TI ± linear ulcers, sinus tracts. Transmural thickening. Increased vascularity.

Ingested Foreign Bodies and Bezoar

Gastric bezoar – retained solid contents which may be hair (trichobezoar), milk products (lactobezoar), vegetable material (phytobezoar) or cloth that is chronically swallowed (esp developmentally delayed). Outlining of air or barium, echogenic arc over bezoar (layer of air betw bezoar and gastric wall), CT air-containing mass.

If initial XRs show swallowed foreign body in stomach or more distal, follow-up not indicated unless there are Sx of obstruction, peritonitis. Oesophageal lodgement most common at proximal oesophagus at level of thoracic inlet. Usually initially asymptomatic. May be passed with fluoro guided foley balloon catheter via nose, inflated distal to coin/FB and pulled retrograde. Long-term complications include tracheo-oesophageal fistula, inflammatory mass -> compression of trachea. May have underlying oesophageal stricture or vascular ring.

  • Zinc pennies – if retained in stomach corrode and react with stomach acid -> gastric ulceration. Iregular coin margins with holes. Tx endoscopic removal.
  • Multiple magnets – attract across SB loops -> iscahemia, necrosis, obstruction, perforation. Surgical emergency.
  • Button batteries – cause caustic injury to mucosa esp oesophgus. Have bevelled edge, centrally thicker, double outline.

Malrotation and Midgut Volvulus

Normal embryonic rotation: duodenojejunal and ileocolic bowel rotate 270deg anticlockwise about SMA -> DJJ (duodeno-jejunal junction, ligament of Treitz) @ LUQ, caecum at RLQ with long fixed SB mesenteric base preventing twisting.

  • Malrotation – abnormal short mesenteric base. Complete nonrotation of intestine (colon on left and SB on right) has narrow mesenteric pedicle. Diagnosed by DJJ in abnormal position (normally to left of spine and at same level or sup to pylorus/duodenal bulb at L1); must have true AP film (symmetrical rib ends at mediastinum). In borderline-positioned DJJ follow contrast through to SB; if jejunum LUQ and ileum/caecmu RLQ then patient probably not at risk of volvulus. High medial caecum (normal caecum in infants can be mobile in RUQ or medial but never LUQ). Reversed SMA and SMV (normal SMV right, abnormal if anterior or left), but this is not sensitive or specific; SMA smaller, rounder and surrounded by echogenic fat cf SMV. DJJ is mobile in children, may be ‘factitiously’ moved into abnormal posn by SOL or NJ tube.
  • Volvulus – narrow base twists with peristalsis (poor fixation); surgical emergency (may -> obstruction, ischaemia, infarction). May ocur at any age, but >90% in 1st 3/12, rarely >1yo. Proximal obstruction usually as duodenum crosses midline. AXR may be normal, show prominent duodenal bulb, gassless abdomen or SBO. Contrast study mandatory. Beak-like deformity at obstruction. Spiral ‘whirlpool’ appearance of SB. CECT – venous stasis oedema, bowel infarction.
  • Ladd Band – abnormal fibrous peritoneal band connecting caecum to abdo wall, associated with rotation abnormality. Oblique indentation at D3/4. May cause obstruction seprate to volvulus.

Small and Large Bowel

Microcolon – narrow colon <10mm from disuse (meconium not passed normally into colon in utero). Usually ileal pathology including meconium ileus, ileal atresia, colonic atresia, total colonic Hirshprung (uncommon).

Faeces should not be seen in a neonate. This appearances suggests meconium ileus/plug or NEC.

Ileal Atresia/Stenosis

Jejunal and ileal atresia from interruption of blood supply in utero. Variably dilated proximal loops with absent distal gas, collapsed distal bowel, microcolon. Occasionally get very dilated loop of bowel just proximal to the atresia. Apple peel small bowel – inherited diffuse SB atresia with multiple severe stenoses and spiral atretic segment, segmental volvulus.

Meconium Ileus

Exclusively in CF and is earliest manifestation in 10%. Multiple dilated SB loops, bubbly ‘soap-bubble’ contents (retained meconium pellets) in the distal ileum/proximal colon, generalised microcolon. Air fluid levels more likely ileal atresia. Ix/Tx water-soluble contrast enema, should reflux to terminal ileum outlining and lubricating inspissated tenacious meconium filling defects (otherwise may need surgery). May cause volvulus of involved segment, increased risk of perforation. Peritoneal calcifications with meconium peritonitis.

Meconium Plug Syndrome

(Misnomer; small left colon syndrome, functional immaturity of the colon). Functional immaturity of ganglion cells and abnormal peristalsis of distal colon; meconium and ganglion cells are otherwise normal. Normal/dilated proximal colon with meconium filling defects in the mid/distal colon, empty distal colon. Rectosigmoid ratio tends to be normal. More common in large infants, diabetic mothers, maternal magnesium sulfate for eclampsia. Transient, Tx rectal stimulation or saline enema, Gastrograffin enema (Tween/polysorbate 80) to irritate colon and stimulate defecation.

Hirschsprung’s Disease

(Congenital aganglionic megacolon). Absent ganglion cells in myenteric/Auerbach plexus of distal colon -> abnormal peristalsis. 1:5,000. 90% present with failure to pass meconium, others constipation in later life. M:F 4:1, 10% have Down syndrome, 5% serious neurologic abnormality. Involves sigmoid and variable more proximal colon with no skip lesions. Most limited to rectum and sigmoid. Well-defined zone of transition in older infants with proximal colonic dilatation (may become massive = megacolon). May cause mucosal inflammation with shallow ulcers in the proximal colon. May present with colitis, hence if diagnosis is suspected avoid enema if unwell (risk of perforation). Necrotizing enterocolitis uncommon complication, from stasis colitis.

Fasciculations/saw-toothed/corrugated tortuous irregular narrowed aganglionic segment from spasm. If whole colon is involved (rare), mimics microcolon. Barium evacuation delayed usually >24h. Similar appearances to meconium plug syndrome. In contrast enema, must obtain early filling views collimated to rectum and sigmoid in lat then frontal. Reversed rectosigmoid ratio with sigmoid diameter > rectum (normal rectum largest of descending colon). Radiographic transition zone not accurate for histological ganglion cell transition. Dx confirmed with rectal biopsy. Tx surgical resection.

Meconium Peritonitis

Intrauterine intestinal perforation from obstruction (atresia, in utero volvulus, meconium ileus) or ischaemia, occasionally active postnatal perforation -> peritonitis. Usually perforation heals in utero with extruded meconium forming a mass (wwith meconium cysts), occasionally calcifies with scattered amorphous/curviliniar calc throughout peritoneum, may -> scrotum via patent processus vaginalis. Multiple scattered calcifications with ‘snowstorm’ of bright echoes. Calcifications slowly resolve, occasionally adhesional BO.

Functional Megacolon

Common, from spasm of puborectalis, idiopathic/multifactorial or secondary to anal fissures. Prominent puborectalis sling. Normal-large rectum, large stool capacity.

Inguinal Hernia

Common 1-6/12. Unilateral prominent inguinal or scrotal loops.

Necrotising Enterocolitis (NEC)

Almost exclusively premature infants in NICU, usually 1-3/52, 10% of those <1500g, most are enterally fed. Multifactorial with hypoxia of gut, infection, prematurity; reduced risk with maternal breast milk. PR bleeding, distention, feeding intolerance, increased NG aspirates. Commonly ileum and right colon. Dilated bowel (fixed dilated = ischaemic nonviable), featureless unfolded loops, separation of loops (bowel wall thickening), increased or absent perfusion/colour doppler flow, thumbprinting, spasm, mucosal irregularity. US thickened and echogenic. Pneumatosis intestinalis with linear/curvilinear, bubbly/granular intramural gas (appears like stool, which is not seen in sick premature NICU babies). PV gas with branching linear lucencies overlying the liver. Large amount of free fluid or free gas poor prognosis. May lead to strictures. Mortality 20-30%. Rx NBM, ABs, serial AXR (AP supine + cross-table lat or L lat decub), surgery if perforated/peritonitis.

Typhlitis/neutropaenic colitis – localised necrotising colitis, usually caecum in leukaemia or other neutropenic patients.

Imperforate Anus

(Ectopic anus, anal atresia). Ranging from membranous anal atresia to arrest of colon at puborectalis sling with fistula from blind-ending rectal pouch to genital/urinary tract or perineum. Associated with sacral anomoly (if present check for tethering or masses, most have neurogenic bladder dysfunction), urinary tract anomalies, hydrometrocolpos, persistent cloaca. Distal pouch seen with US. Fistula seen with direct injection, retrograde voiding cystourethrography, or flush retrograde vaginography. If above puborectalis sling then is the sling assumed hypoplastic and continence will be difficult; if below puborectalis usually better developed. ‘M’ line of Cremin mid/lower third junction of ischium perpendicular to long axis on lateral = approximate location of puborectalis; above = high, at = indeterminate (usually same problems as high), below = low.

Colonic Atresia

Rare, evident in neonatal period. Masssive distension of colon proximal to atresia/stenosis, as the gas is trapped between the competent ielocaecal valve and atretic segment, appears similar to volvulus.

Enteric Duplication Cyst

From SB (44% esp TI), distal oesophagus, colon (15%). Most asymptomatic. Anechoic, round/oval mass, two-layered wall (inner echogenic mucosa, peripheral hypoechoic muscle). Uncommonly tubular, can communicate with lumen. Seen on Tc-99m if contains gastric mucosa. Cx ulceration/haemorrhage if contains ectopic gastric/pancreatic tissue, lead point for intussusception/volvulus.

DDx Mesenteric and omental Cysts – 1st decade of life, ?benign lymphatic malformations. Single layer thin wall, unilocular, may have internal septations.

DDx Pseudocysts – acquired, loculated. Most common pancreatic pseudocysts from pancreatitis, blunt trauma; true pancreatic cysts are rare (may be seen with ADPKD, vHL). CSF pseudocyst Cx of ventriculoperitoneal shunt, adhesions trap draining fluid.


>2yo. Obstructed appendiceal lumen -> distention, infection, ischaemia, perforation. Clinical Sx nonspecific in 1/3, temporarily improve with perforation. AXR normal or reduced gas (some in RLQ), perf -> SB dilatation from reduced peristalsis, partial obstruction in region of abscess. Scoliosis concave to the right (spasm). Indistinct lat right psoas edge. Flank stripe sign – right paracolic exudate/inflammation displaces bowel gas medially. Faecolith seen in 5-10%. Free gas rarely seen on AXR due to intense inflammatory response. USS has low negative predictive value, easier in girls, thin; graded compression, more difficult if perforated (decompressed). Appendix >6mm diameter, lack of compresssibility, tender, thickened, shadowing echogenic appendicolith, surounding echogenic fat. Abscess -> RLQ mass, anechoic to solid appearances on US. DDx omental infarction – heterogeneous mass betw ant abdo wall and colon. Bacterial peritonitis can be from from appendicitis or sepsis (incr risk nephrotic syndrome).


3/12-1yo, almost all <3yo (older suggests pathologic lead point). Forward peristalsis invaginates proximal bowel (intussuseptum) into lumen or distal bowel (intussuscipiens). May travel length of entire colon. Idiopathic ileocolic (90%, ?viral lymphoid hypertrophy of TI), secondary to pathologic lead point, or incidental SB-SB. Lead point from tumour (lymphoma), diverticula (incl Meckel), duplication cyst, Henoch-Schonlein purpura polyp, tumour. Transient spontaneously reducing SB-SB intussusceptions are typically short (<35mm), slightly echogenic, smaller diameter. AXR normal or obstructed, meniscus of head of intussusceptum visible in 1/2 (soft tissue mass along course of colon, fat may be seen), absence of asc/transverse colon gas. Air-fluid levels distally make intussusception unlikely (more likely gastroenteritis). US cylindric mass of outer hypoechoic ring surrounding variable echoic concentric rings (oedematous intestine and mesentery, transverse donut, longitudinal pseudokidney), central anechoic fluid, surrounding echogenic mesentery fat-standoff or adenopathy. Colour doppler to asses viability.

Non-surgical reduction with air/contrast enema if no free gas or peritonitis; reduced success if obstruction >24h duration, lethargy. Air enema reduction greater pressures and faster reduction time and rate than contrast, must not exceed 120mmHg. Contrast reduction (1:5 GG) elevated to ~1.5m. Hydrostatic reduction can be done under ultrasound guidance. Criteria for success include resolution of mass and free reflux into SB. Often gets stuck at ileocaecal valve, may help to repeat after rest to help reduce oedema. Reduction rate 80-90%, still helpful in refractory cases (recommended up to 3x). Improved without sedation (patient can increase pressure via Valsalva). Risk of perforation <0.5%. Recurrent in 5-10%, increased chance of fixed lead point being present, hence consider surgery.

Meckel Diverticulum

Omphalomesenteric/Vitelline duct connects cord to ileum. Persistence -> cysts, sinuses, fistula or Meckel diverticulum. Meckel may cause bleeding (from ectopic gastric/pancreatic mucosa), inflammation, perforation or intussusception.

Tumours of the GI Tract

Uncommon. SB most likely non-hodgkin lymphoma. Colon polyps usually inflammatory or colonic polyposis syndrome. Colonic tumours include leiomyoma, leiomyosarcoma, lymphoma. Mesenteric/omental tumours include primary Burkitt lymphoma, mets, neurogenic tumours, inflammatory pseudotumour, haemangioma, teratoma.

Bowel Disease in the Immunocomprimised

  • Intraabdominal collections uncommon, usually from systemic fungal infection (Candida albicans, Aspergillus) with multiple small hypodense lesions in liver, spleen or kidneys.
  • Pseudomembranous colitis – overgrowth of Clostridium difficile in patients receiving antibiotics. Discrete yellow plaques/psedomembranes of mucosal surface, separated by normal mucosa. Diffuse pancolitis, marked hypodense wall thickening (average 15mm), accordian sign (contrast betw pseudomembranes and swollen haustra). Disproportionately litle pericolic stranding (process localised to mucosa/submucosa).
  • Neutropenic colitis (typhlitis, necrosing enteropathy) – life-threatening necrosing inflammation of caecum and ascending colon ± TI with ischaemia, secondary bacterial invasion. Mural thickening, adventitial enhancement, pericolic stranding/fluid.
  • CMV colitis – caecum/ascending colon and TI with mural thickening, stranding.
  • Mucositis – chemotherapeutic damage to mucosa with impaired regenerative ability. Small and large bowel, fluid-filled dilated loops (ileus), thin enhancing wall, absent/minimal wall thickening or stranding. Tx supportive.
  • Acute graft-vs-host disease – bone marrow transplant with donor T lymphocytes -> epithelial damage, extensive crypt cell necrosis, diffuse mucosal destruction of small and large bowel. Diffuse involvement duodenom to rectum with mucosal enhancement (thin layer of vascular granulation replacing destroyed mucosa), fluid-filled dilated loops, mild mural thickening in SB, prominent stranding.
  • Lymphoproliferative disease – lymphoma-like uncontrolled proliferation of cells infected by EBV esp post solid-organ transplant. Focal usually SB mass/marked wall thickening, aneurysmal dilatation, liver lesions, lymphadenopathy and mesenteric masses. Distribution tends to vicinity of transplant organ. DDx NHL.

Cystic Fibrosis (CF)

Neonates present with meconium ileus. Distal intestinal obstruction syndrome (meconium ileus equivalent) in older children/adults with inspissated, tenacious intenstinal stool in right colon and distal SB with proximal obstruction. May resolve with gastrografin enema. Iatrogenic strictures may form from pancreatic enzyme replacement. Other problems include cirrhosis, portal hypertension, varices, gallstones, pancreatic atrophy with fatty replacement.

Pancreas and Adrenal Gland

Normal adrenal inverted V, echogenic centre, hypoechoic peripheral zone.

Adrenal Haemorrhage

Most common newborn adrenal enlargement. Mostly right, occasionally bilat. Increased risk in large babies, obstetric trauma, neonatal sepsis, hypoxia. Mass, jaundice, hypotension, anaemia. In older children from trauma, meningococcaemia, anticoagulant therapy. Enlarged, loss of V-shape, predominantly cystic hypoechoic mass, resolving over time. Occ calcifies from rim -> small completely calcified gland -> rarely adrenal insufficiency. MRI low T2. Cx renal compression, renal vein thrombosis, infection.


Neuroblastic tumours range from benign ganglioneuroma, ganglioneuroblastoma to malignant neuroblastoma by degree of cellular maturation. <5yo but most <2yo, most present late with large mass. 40% arise from adrenal medulla, others anywhere along the sympathietic chain including paravertebral abdomen (25%), posterior mediastinum (15%), pelvis, neck, brain (cerebral neuroblastoma). 90-95% have elevated urine catecholamines (venillylmandelic acid). Range from insitu small nodules (most silent and spontanesouly regress leaving a focus of fibrosis/calcification), to large masses. Histological Homer-Wright pseudorosettes, better differentiated lesions (eg ganglioneuroma) have Schwann cells. Poorly marginated, echogenic, heterogeneous, occasionally characteristic echogenic central nodule, frequently extends across midline (post to aorta) and into chest, may invade kidney, stippled calcification in 85%, encases blood vesels without vascular invasion. Mets to liver, LN, bone marrow, intraspinal extension, skin, periorbital region. Mets to lungs uncommon (cf Wilms). MRI slightly better than CT for tumour extension into neural foramina. High T2, heterogeneous. I-131-meta-iodobenzylguanide MIBG (resembles norepinephrine metabolised by neuroblastoma, pheo) and octreotide scans for primary and mets.

International neuroblastoma staging: Most are stage 3/4. More favourable prognosis with stage 1/2/4S, <18/12 old.

  • Stage I – Complete gross excision
  • Stage 2A – Incomplete gross resection
  • Stage 2B – Ipsilateral nonadherent LN positive for tumour
  • Stage 3 – Unresectable unilateral, infiltrating across midline
  • Stage 4 – Distant LN, or mets
  • Stage 4S (special) – localised 1/2A/2B with limited spread to skin, liver or bone marrow. Must be <1yo.

Adrenocortical Carcinoma

Rare. Highly malignant, locally invasive. Mets to lungs, liver, LN. Frequent virilisation, Cushings (hypercortisolism causes increased retroperitoneal fat).

Wolman Disease

Very rare lipidosis. Enlarged, densely calcified adrenals with normal triangular configuration. Plain films diagnostic. Hepatomegaly, splenomegaly. Fatal at early age.


Uncommon, from virus, blunt trauma, functional stenosis from anomoly, vasculitides, sepsis, haemolytic uraemic syndrome, steroids, metabolic disease (hyperlipidaemia, hypercalcaemia), gallstones. Pancreats divisum – abnormal fusion of Santorini/accessory and Wirsung ducts. US pancreas may be normal or enlarged and hypoechoic, occasionally enlarged duct. Severe, peripancreatic extravasation of lipase -> lipolysis (echogenic). Pseudocyst most common cystic pancreatic lesion, usually spontaneously resolves. Chronic pancreatitis and pancreatic insufficiency in CF, with fatty replacement.

Pancreatic Neoplasm

Rare. Most common benign islet cell adenoma (insulinoma, small difficult to see); solid-cystic papillary tumour, adenocarcinoma, hamartoma, lymphangioma, pancreatoblastoma, cystadenoma.

Hepatobiliary System

Biliary Atresia and Neonatal Hepatitis

Physiologic jaundice/hyperbilirubinaemia common, from physiological destruction of RBC in polycythaemic newborn. Persistence beyond 4/52 suggests biliary atresia, neonatal hepatitis. Hepatitis from infection (Hep B, CMV), familial or metabolic conditions with cholestatic jaundice (a1-antitrypsin, PFIC).

Progressive familial intrahepatic cholestasis (PFIC, Byler’s disease) – AR inherited cholestasis from defect in canalicular bile transport -> retention of bile salts -> hepatitis, cirrhosis. Distended GB. No benefit from surgery.

Biliary atresia – Congenital complete or partial obstruction of the extrahepatic biliary tree within 3/12, with intrahepatic duct proliferation -> rapidly progressing inflammation and fibrosis, secondary biliary cirrhosis (within 3-6/12). 1/3 of infants present with neonatal cholestasis. Associated with abdominal heterotaxy, trisomy 18. Perinatal form (most common) from destruction of normally developed ducts (?virus, autoimmune). Fetal form (20%) from atresia, and is associated with malrotation, interrupted IVC, polysplenia, CHD. Absent visualised GB (but small/barely visible GB is normal in 20%), intrahepatic periductal inflammation, marked ductal proliferation. . Triangular cord sign – echogenic focus representing atretic biliary plate (ant R PV >4mm thick).

Hepatobiliary scintigraphy (Tc99m-HIDA) with phenobarbital to enhance excretion, normally visualised in biliary tree and intestines by 15min. Neonatal hepatitis -> delayed uptake, slow clerance of blood pool but eventual excretion. Biliary atresia -> adequate hepatocyte uptake but absent excretion into GIT despite 24h delayed imaging. Dx with biopsy and IOC. DDx obstructive jaundice, choledochal cyst, inspissated bile syndrome, mass, gallstones.

Biliary Tree Anomalies

Altered architexture of the intrahepatic biliary tree.

  • Von Meyeburg complexes (bile duct hamartomas) – common, small clusters of dilated bile ducts embedded in fibrous stroma, adjacent or within portal tracts. No clinical significance. Associated with PKD.
  • Polycystic liver disease – multiple cystic lesions (few to hundreds) lined by cuboidal biliary epithelium. Associated with PKD
  • Congenital hepatic fibrosis – enlarged irregular portal tracts with septae of collagen dividing the liver into irregular islands. From persistence of the embryonic biliary tree which fibroses over time. Rarely develops cirrhosis, but still develops portal hypertension. Associated with PKD.
  • Caroli disease – Uncommon, congenital, most autosomal recessive, most present in childhood. Saccular ectasia of IHBDs without obstruction (mimicing cysts), enhancing fibrovascular bundles centrally within ducts (central dot sign). Segmental with some unaffected liver segments, focal biliary narrowings and saccular dilatations. Dilated CBD (10-30mm) in 50%. Usually associated with congenital hepatic fibrosis. May be associated with medullary sponge kidney, ARPCKD. Cx pyogenic cholangitis, liver abscess, biliary stones, increasd risk of cholangiocarcinoma.
  • Alagille syndrome (syndromatic paucity of bile ducts, arteriohepatic dysplasia) – rare AD multiorgan, mutation in Jagged1 gene. Absence of bile ducts in portal tracts causing chronic cholestasis, peripheral stenosis of the PA, butterfly vertebrae, eye defect (posterior embryotoxon), hypertelic facies. Risk of hepatic failure and HCC.

Choledochal Cyst

Uncommon, most present in infancy/childhood, occasionally antenatally, F:M 3-4:1. Pain, RUQ mass, jaundice. Cystic dilatation of ducts of unkown aetiology. Most cause abnormal pancreatobiliary junction (APBJ) -> reflux of pancreatic enzymes to CBD -> inflammation and weak duct wall. Dilated intrahepatic ducts, free communication with ducts on scintigraphy. Increased risk of gallstones, stenosis and strictures, pancreastitis, biliary obstruction, cholangiocarcinoma. Todani classification:

  • Type I (80-90%) – fusiform/saccular dilatations of CBD below cystic duct
  • Type II – isolated diverticulum of CBD with narrow stalk
  • Type III (choledochocoeles) – focal dilatations of intraduodenal CBD
  • Type IV – multiple focal dilatations of IHBDs and EHBDs ± cystic dilatation of CBD
  • Type V (Caroli disease) – not a true choledochal cyst. Multiple dilatations limited to intrahepatic ducts.

Liver Masses

Difficult to differentiate between lesions, major role of imaging for extent and response to treatment. <5yo – hepatoblastoma, haemangioendothelioma, mesenchymal hamartoma, mets (Wilms, neuroblastoma). >5yo – HCC, undifferentiated/embryonal sarcoma, hepatic adenoma, haemangioma, mets. Immunocomprimised – lymphoproliferative disorder, fungal infection. Elevated alpha-fetoprotein in hepatoblastoma and HCC, occasionally haemangioendothelioma. Multiple lesions favours mets, abscesses, cat scratch disease, lymphoproliferative, hepatic adenomas with syndrome.

  • Hepatoblastoma – <3yo, most common primary liver tumour of childhood, painless mass, elevated AFP in >90%. Most without associated conditions, common in Beckwith-Wiedemann syndrome, FAP, hemihypertrophy, Gardner syndrome, Wilms tumour, biliary atresia. Well-defined, displaces rather than invades, may be heterogeneous from necrosis/haemorrhage. Treated 5-yr survival 80%.
  • Infantile haemangioendothelioma – Most common symptomatic vascular liver lesion, most <6/12. Common Cx high output cardiac failure, haemorrhage, jaundice, haemolytic anaemia, thrombocytopaenia. Associated with cutaneous haemangiomas in most. Solitary or multiple. Well-defined solid/complex/heterogeneous mass or difuse. Large feeding and draining vessels. Hypodense, peripheral enhancement, high T2 with flow voids. Dilated irregular vascular lakes with stain persisting beyond venous phase, dilated feeding vessels. AV shunting with early venous filling. Enlarged descending aorta proximal to hepatic branches. Tend to spontaneously involute over months-years. Tx if symptomatic with steroids, embolisation, or surgery. DDx multiple haemangiomas.
  • Mesenchymal hamartoma – Very rare, benign, <2yo. Developmental anomaly rather than true neoplasm. Usually solitary. Mostly cystic with multiple thin septations and intervening solid nodules. May have more solid component with multiple small cysts giving ‘Swiss cheese’ appearance.
  • Hepatic Adenomas – Rare. Associated with Fanconi anaemia, glycogen storage disease type 1, Gaucher disease, Hurler disease, severe combined immunodeficiency. No sulfur colloid uptake.
  • Focal Nodular Hyperplasia – Likely hyperplastic response to congenital AVM. Mass-like. Early enhancement, isodense on delayed. Enhancing central scar. Normal/increased sulfur colloid uptake (cf adenomas).
  • Metastases – from neuroblastoma, lymphoma, leukaemia, Wilms tumour.
  • Hepatocellular carcinoma (HCC) – more common in older children/adolescents. Single or multiple. Hyperechoic with hypo/an-echoic regions of haemorrhage/necrosis. Invasion of hepatic/portal veins. Variable enhancement. MRA to evaluate tumour blood supply for surgery. PET most sensitive.
  • Undifferentiated/embryonal sarcoma
  • Embryonal rhabdomyosarcoma of the biliary ducts – 2-5yo. Jaundice (if major duct).

Bile Plug Syndrome

Impacted/inspssated bile in extrahepatic ducts causing obstruction. Associated with CF, severe erythroblastis fetalis, altered biliary dynamics with TPN. Intra- and extra-hepatic duct dilation, distended GB, echogenic material/sludge filling defects in CBD and GB.

Cholecystitis and Cholelithiasis

Cholecystitis distened, thickened wall with surrounding oedema. In otherwise healthy or HIV. Cholelithiasis in sickle cell, congenital obstruction of biliary tract, TPN, frusemide, dehydration, haemolytic anaemia, short gut syndrome.

Acute Hydrops of the Gallbladder

Transient obstruction of cystic duct. Neonate esp prem. Associated with Kawasaki disease, prolonged TPN, sepsis. Markedly enlarged tender GB with thin wall.

Hepatic Cysts

Less common than adults. Thin walls, anechoic fluid, some large and pedunculated. Multiple cysts in autosomal dominant polycystic disease.


Spleen low T2 in neonate until development of white pulp at several weeks old. Splenomegaly from haematologic disease, infection, portal hypertension, infiltrative disease (mucopolysaccharidosis, reticuloendotheliosis, leukaemia, lymphoma).

  • Infection in newborn/infant, usually bacterial sepsis/infection with hepatomegaly. Older children usually infectious mononucleosis, typhoid fever, catscratch fever (Bartonella). Multiple small ill-defined hypoechoic lesions in catscrath disease, TB or fungal. Splenic abscess uncommon, usually in impaired immunity.
  • Cystic masses include congenital epidermoid cyst, posttraumatic pseudocyst, echinococcal cyst. Cystic lymphangiomatosis – benign lymphatic malformation. Multiloculated cystic ± calc and enhancment.
  • Primary neoplasms (haemangioma, hamartoma, angiosarcoma) are rare.
  • Lymphoma, leukaemia may not cause enlargement; enlargment doesn’t mean involvement.
  • Haemophagocytic lymphohistiocytosis (HLH) – rare, overactive histiocytes and macropahges, phagocytose normal cellular blood, not truely malignant, <1yo. Hepatosplenomegaly, ascites, GB thickening, lymphadenopathy, pleural effusion.
  • Splenic infarction from sickle cell anaemia, leukaemia, Gaucher disease, cardiac valvular disease, rarely torsion of poorly fixed/wandering spleen. Reduced echogenicity, diminished/mottled enhancement.

Kidneys and Collecting System

Normal neonatal kidneys proportionately large, lobulated (fetal lobulation = inter-renicular septum), echogenic cortex, prominent hypoechoic pyramids. Renal size normally within 10mm of each other.

Hydronephrosis from obstruction or VUR. High-output hydronephrosis is rare, in Bartter syndrome (thick ascending loop of Henle, similar to Frusemide), diabetes insipidus, psychogenic water drinking.

Unilateral enlargement from hydronephrosis, MCDK, renal vein thrombosis, tumour; bilat in hydronephrosis, PCKD, storage diseaseses, glomerulonephropathies, nephrotic syndrome, leukaemia/lymphoma mets.

Followup of antenatal renal dilatation should be 1st 24hrs or >7days to reduce underestimation of hydronephrosis from normal relative state of dehydration.

Urinary Tract Infection (UTI), Pyelonephritis and Renal Abscess

Ascending infection from chronic reflux, scarring, growth impairment. Neonatal UTI usually leads to urosepsis. Cystitis bacterial or viral, thickened mucosa. Renal scarring most commonly from pyelonephritis, independent to VUR.

  • Acute pyelonephritis – altered/reduced vascularity, enlarged kidney, altered/increased echogenicity, may be mass-like. DMSA most sensitive test, with single/multiple triangular peripheral areas of reduced uptake. CT may show striated nephrogram.
  • Chronic pyelonephritis (scarring) – loss of renal parenchyma from previous bacterial infection .Cortical indentations tend to overlie renal calyces (cf fetal lobulations between calyces). Normal cortical thickness should be symmetric and equal throughout kidney.
  • Renal abscess (uncommon) – round/oval cysti,c may have debris, peripheral enhancement.
  • Fungal infection (premature and immunocomprimised) – echogenic hyphae clusters, may involve collecting system causing hydronephrosis.

UTI atypical if unwell/septic/HTN, poor stream, mass, raised Cr. If <6/12 and uncomplicated UTI -> USS; atypical/recurrent -> USS + DMSA + MCU. If 6/12-3y uncomplicated -> nil Tx; atypical/recurrent -> USS + DMSA. If >3y uncomplicated -> nil; atypical -> USS; recurrent -> USS + DMSA. Aim is to reduce renal damage leading to chronic renal disease and HTN.

Congenital Abnormalities of the Kidney and Urinary Tract (CAKUT)

Renal ectopia from abnormal migration from fetal pelvis -> renal fossa, most lie in the pelvis and malrotated.

Renal fusion from failed separation of primitive nephrogenic cell masses into L and R blastemas. Increased risk of other renal anomalies, infection, injury from mild trauma, renal vascualar HTN, calculi, hydronephrosis, slight increased risk of Wilms tumour and RCC.

  • Horseshoe kidney (most common, 1:600 births) – fused LPs across midline (10% fused at UPs), connecting isthmus may be functional tissue or fibrous tissue ant to aorta and IVC. Usually more inf than N; ureters exit ant (cf normal ant-med). Variable arterial supply, may have multiple bilateral RAs, origin from iliac arteries.
  • Crossed fused ectopia – both kidneys on one side, with ectopic kidney’s ureter crossing midline and entering bladder in expected location.

Renal agenesis – AD or isolated. Lack of induction by ureteral bud. Bilateral agenesis (BRA) -> oligohydramnios, Potter sequence, foetal demise or stillbirth. Unilateral (URA) associated with reproductive anomoly. Absent renal tissue -> enlarged elongated adrenals. In females associated with genital tract anomalies. Ipsilateral adrenal agenesis in 10%. Contralateral renal compensatory hypertrophy.

  • Potter sequence/syndrome – oligohydramnios (BRA, atresia/obstruction of ureter/urethra, PCKD, renal hypoplasia, amniotic rupture, placental insufficiency) -> compression of foetus -> abnormal facial features, skeletal abnormal, severe pulmonary hypoplasia, refractory pneumothoraces.

Renal hypoplasia – usually unilateral; bilateral may cause early childhood renal failure. Most are probably acquired scarring (vascular, infectious or other parenchymal disease). True developmental failure is extremely rare, has no scars, reduced renal lobes and pyramids (<6).

Renal Calcifications

  • Nephrolithiasis (collecting systems) rare.
  • Nephrocalcinosis (renal tubules/parenchyma) – usually in medulla/pyramids, increased punctate/diffuse echogenicity. Renal tubular acidosis, medullary sponge kidney, hyperparathyroidism, drugs (frusemide, steroids, vit D), prolonged immobilisation, Bartter syndrome (thick ascending loop of Henle), Williams syndrome (neurodevelopmental disorder with transient hypercalcaemia).
  • Echogenic renal pyramids also seen in a normal neonate, Tamm-Horsfall proteinuria (transient increased uromodulin protein that inhibits calcs, self-limiting), sickle-cell, autosomal recessive PKD, storage diseases (glycogen storage 1A, hurler mucopolysaccharidosis, Lech-Nyhan syndrome, Oxalosis)

Ureteropelvic Duplication and Ureterocoele

Premature division/duplication of ureteral bud, bilateral in 20%. Duplication/duplex kidney common.

  • Bifid renal pelvis (10% of population) – ‘renal cortex’ separating renal fat into sup and inf components.
  • Incomplete duplication – two ureters joining at midureter or just prior to bladder; not at increased risk of disease.
  • Complete ureteral duplication – higher risk of UTI, obstruction, VUR, scarring. Weigert-Meyer rule: UP ureter is ectopic usually more medially and inf to bladder neck or urethra; more prone to obstruction from a ureterocoele, may be hydronephrotic or atrophic; LP more prone to VUR (drooping lily sign on MCU with inf displacement, may have reflux nephropathy, due to distortion by adjacent ureterocoele) and PUJ obstruction.

Ureterocoele – saccular/round/oval dilated distal ureter between mucosal and muscular layers from stenotic/obstructed orifice. Invaginating into bladder lumen, impeding urine flow. May be simple/orthotopic (tend to be small) or ectopic (almost always duplicated collecting system, 10% bilat, F>M). On cystography filling defect best seen on early filling, as can be compressed from a filled bladder. May invert and appear as diverticula.

Renal Cystic Disease

See Kidneys

Multicystic Dysplastic Kidney (MCDK)

In-utero persistance of abnormal/disorganised tissue in the kidney (islands of undifferentiated mesenchyme with cartilage and immature collecting ducts), most asociated with PUJ obstruction, ureteral agenesis/atresia or other anomalies. Unilateral or bilateral, always cystic. Grapelike variably sized cysts that do not communicate, absent dominant central cyst/hydronephrosis; but if obstruction at proximal ureter -> hydronephrotic form of MCDK. No tracer accumulation on scintigraphy. Rarely isolated to upper/lower pole. Most involute over time with residual dysplastic tissue not visible on imaging, but often calcifies. Risk of HTN -> Tx nephrectomy if develops. Possible increased risk of malignancy.

Vesicoureteric Reflux (VUR)

Retrograde flow, in <0.5% of asymptomatic, up to 50% of children with UTIs, in almost all with severe renal scarring. Associated with ascending infection, renal growth impairment, scarring. Secondary VUR from bladder outlet obstruction, neurogenic bladder. Primary VUR from short submucosal tunnel at VUJ. Scarring from infection (not sterile reflux). Risks include FHx siblings/parents, structural VUJ abnormal (eg Hutch diverticulum), dysfunctional voiding (bladder contraction against contracted external sphincter). Reflux nephropathy = VUR with associated small scarred kidneys.

Grade I -> ureter; II -> pelvis and calyces; III mild/mod ureteric/pelvic dilatation/tortuosity but no/slight blunting fornices; IV complete blunting of fornices; V gross dilatation and loss of papillary impressions in most calyces. Low grade (I-III) resolves spontaneously by 5-6yo, may be treated with prophylactic AB. High grade (IV-V), presence of renal scarring or breakthroguh UTIs, may need surgical reimplantation or synthetic material injection at VUJ. High grade associated with intrarenal reflux.

Antenatal renal dilatation >10mm in 3rd T, parent/sibling with VUR, single kidney, MCDK should have prophylactic ABs and MCU + US at 6-8/52. Grade I-II VUR with normal US stop fu; grade III-V continue ABs with US and DMSA at 4-6/12. Severe PUJ or VUJ then MAG3 scan. Renal pelvis >/=10mm or other significant abnormal then US at 6/12.

Pelvi-Ureteric Junction (PUJ) Obstruction

(Uteropelvic junction/UPJ obstruction). Most common congenital urinary tract obstruction. From inadequate recanalisation during development, kinking or extrinsic bands or aberrant vessels (15-20%), but most unknown. Bilateral in 30%. Associated with VUR, renal duplication, VUJ obstruction. Pelvicaliectasis with sharp transition at PUJ. Severity best evaluated with MAG3. Predisposed to renal injury by minor trauma. May go undiagnosed until adulthood.

Vesicoureteric Junction (VUJ) Obstruction

Primary/Congenital Megaureter

Urether is enlarged >7mm. More common on L, M>F. May be associated with other congenital anomalies (MSK, horseshoe, duplex). Renal parenchyma preserved and functioning normally, 30% improve over time.

  • Obstructive primary megaureter – congenital abnormal muscular layers -> aperistalsis of the distal ureteric segment -> functional obstruction (analagous to achalasia or Hirshsprungs). Contracted juxtavesical ureter (cf widely patent VUJ in refluxing megaureter). May be associated with megacalyces, faceted with no papillary impressions.
  • Refluxing primary megaureter – secondary to VUR, from short itnramural segment, diverticulum, ureterocoele, raised intravesical pressure (neurogenic bladder, urethral obstruction).
  • Non-refluxing nonobstructed primary megaureter (most common) – no evidence of reflux or obstruction, but ureter enlarge. No/minor hydronephrosis, unless associated with congenital megacalyces. Unknown cause.

Renal Masses

Wilms Tumour

(Nephroblastoma). Most common renal neoplasm of childhood (cf mesoblastic nephroma in neonate), mean age 3yo with most 1-5yo, from primitive metanephric epithelium. Rapidly growing unilateral mass. 5-10% bilateral/multicentric at time of presentation, either synchronous or metachronous. May be associated with Beckwith-Wiedemann syndrome (BWS with organomegaly, macroglossia, hemihypertrophy, omphalocoele, adrenal cytomegaly), nephroblastomatosis, WAGR syndrome (aniridia, genital anomalies, mental retardation), Denys-Drash syndrome (gonatal dysgenesis, early nepphropathy). Precursor nephrogenic rests seen in adjacent renal parenchyma in 25-40% unilateral, 100% of bilateral tumours, so presence indicates high risk of contralateral Wilms tumour. Well-defined, mostly solid, echogenic with hypoechoic/anechoic necrotic/haemorrhagic areas. Hydronephrosis is common. Calcification uncommon. Claw sign – stretching of renal parenchyma at margin (indicating intrarenal mass). Tends to grow in a ball, displacing blood vessels rather than engulfing. If crosses midline tends to pass anterior to the aorta. Commonly extends into renal vein, IVC and RA. Mets to lungs in 20%. May rupture into peritoneum. Prognosis dependent on histology, most are cured. Increased risk of developing second primary tumours including bone/soft-tissue sarcomas, leukemia, lymphomas, breast cancers; may be due to germline mutation in cancer predisposition gene or consequence of therapy (radiation).


Islands of primitive metanephric blastema/nephrogenic rests (precursor of Wilms tumour), usually regress by 4/12. Vary from expansile masses to fibrous tissue. Nephroblastomatosis is rare persistence of the blastema with diffuse, plaquelike, peripheral, nonenhacing lesions. May become confluent with complete replacement of cortex with thickening, bilateral lobulated enlarged kidneys, compression/stretching/distortion of pelvicaliceal structures, low echogenicity HU and T1 signal. When a lesion becomes spherical, increased in size or progressive increased heterogeneous enhancement, Wilms tumour suggested.

Mesoblastic Nephroma

(Foetal renal hamartoma). Most common renal tumour of neonate, average 3/12, from metanephric blastema, spindle-type cells. Considered benign, infiltrative; occasionally mets. Mixed echogenic intrarenal mass, variable enhancement, indistinguishable from Wilms tumour.

Multilocular Cystic Nephroma

Rare cystic mass with multiple septa. Bimodal young boys (3/12-2yo) and adult women (40-50yo). Benign. Well-circumscribed, multiseptated masses. Cannot be distinguised from Wilms or other malignancy at imaging, hence surgical resection.


Predisposed in tuberous sclerosis (also associated with ADPKD, renal cysts). Start as small echogenic foci in kidneys during early childhood > large infiltrative masses. Fatty components, spontaneous haemorrhage (leading cause of death in tuberous sclerosis). Tx prophylactic embolisation if >40mm (dysplastic aa and aneurysms bleed).

Other Renal Tumours

  • Renal cell carcinoma – rare, most common in older children/adolescents. Nonspecific solid renal mass. Calcifies in 25%.
  • Clear-cell sarcoma and rhabdoid tumour – poor prognosis, identical appearance to Wilms tumour apart from mets; clear cell -> bone, rhabdoid -> brain mets and secondary primaries.
  • Infiltration from leukaemia or lymphoma.

Bladder and Urethra

Expected bladder capacity in mL = [2 + (age in yrs)] x 30.

Neurogenic Bladder

From myelodysplasia/spinal dysraphism, hydrocephalus, cerebral infarct, brain or spinal cord neoplasma. Spinal cord and upper motor neuron abnormalities -> spastic bladder and detrusor hyperreflexia. Disorder betw cord and peripheral nerves -> overdistended bladder from lack of contraction (detrusor areflexia). Detrusor-sphincter dyssynergy – abnormal external sphincter contraction during detrusor contraction (esp myelodysplasia), small markedly trabeculated bladder, may cause VUR

Bladder Diverticula

Solitary usually congenital eg Hutch diverticulum adj to VUJ, associated with VUR. Multiple diverticula from neurogenic bladder, chronic outlet obstruction, Ehlers-Danlos syndrome, Williams syndrome (multiple deleted genes causing neurodevelopmental disorder with elfin face, cheerful demeanor, development delay, supravalvular AS, transient hyperCa, diverticulosis), Menkes syndrome (X-liked recessive copper deficiency with hypotonia, retardation, brittle hair, metaphyseal widening), prune belly syndrome.


  • Prune belly/Eagle-Barrett syndrome – rare, almost exclusively males with absent/deficient abdominal musculature (bulging flanks), cryptorchidism and urinary tract abnormalities including large vertical trabeculated hypertrophied bladder, severe hydronephrosis and hydroureter, urachal diverticulum, cone-shaped post urethra/bladder neck region -> outlet obstruction. Incomplete/pseudo-prune belly syndrome in girls, without cryptorchidism. Can ocur unilaterally.
  • Megacystitis-microcolon-hypoperistalsis (MMH) syndrome – almost exclusively girls with disorder of GI/GU smooth muscle, insufficient abdo musculature, large dysfunctional bladder, decreased intestinal peristalsis (poor evacuation), bladder exstrophy (large ant abdo wall defect), marked symphysis pubis widening, splayed pelvic bones.

Bladder Exstrophy

Congenital lower anterior abdominal wall defect with bladder open, mucosa continuous with skin. Associated with epispadias, symphysis pubis diastasis, ureteral obstruction, umbilical/inguinal hernias. Tx urinary diversion, bladder augmentation, skin graft. May undergo colonic metaplasia, increased risk of adenocarcinoma.

Urachal Abnormalities

Vestigial remnant of urogenital sinus and allantois, usually forming median umbilical ligament.

  • Urachal remnant/rests/cyst (30%) – from dome of bladder midline where both ends closed. May become infected and cause wall calcification.
  • Vesico-urachal divertucula (5%) – asymptomatic, from ant-sup dome of bladder. Stasis may cause infection, stones, increased risk of carcinoma in diverticulum.
  • Urachal sinus (15%) – patent only at umbilical end. May cause persistent umbilical discharge.
  • Patent urachus (50%) – persistent patent urachus from bladder to umbilicus. Urine leak at umbilicus which may not be apparent until lower urinary obstruction develops.

Cloacal Anomalies

Persistent primative common channel for rectum, vagina, urethra. Variable anatomy requiring injection via all orifices. Cloacal exstrophy from failed lower abdominal wall closure -> severe bladder exstrophy.

Posterior Urethral Valve

High back pressure -> reflux, renal damage and reflux.

  • Type I – Abnormal migration/regression of urethrovaginal folds -> flaps of tissue at base of prostatic urethra below verumontanum -> obstructed antegrade flow -> post urethral dilatation, bladder wall thickening/trabeculation, VUR.
  • Type II – nonobstructing mucosal fold ‘valve’.
  • Type III – Incomplete canalisation at urogenital diphragm with persistent cloacal membrane. Thin diaphragm characteristic.

Anterior urethral valves rare, uncertain aetiology.

Reproductive System

Neonatal uterus prominent (maternal oestrogen stimulation), involutes after 2-3/12 until puberty. Epidydymis proportionally larger.

Ambiguous Genitalia


  • Congenital adrenal hyperplasia (60%) – (adrenogenital syndrome) usually genotypical female with ovaries. Enlarged, undulating, ‘cerebriform adrenal’ glands.
  • Virilisation – usually 21-hydroxylase deficiency -> increased androgens.
  • Androgen insensitivity/male pseudohermaphrodism – underdeveloped gonads, absent Mullerian structures.
  • Gonadal dysgenesis (loss of gonadal primordial germ cells -> fibrous streak) – mixed (1 testis, 1 gonadal streak) or pure (bilat streak).
  • True hermaphrodism has both ovarian and testicular tissues.

On urethrography may have enlarged utricle in boys or urogenital sinus (confluence of vagina and urethra) in girls. Imaging used to detect presents of uterus and vagina for gender assignment

Testicular Neoplasm

Testicular neoplasms uncommon in childhood. 90% germ cell, <10% leukaemia/lymhpoma mets. Often associated with hydrocoele. US can only tell solid lesion. If extratesticular scrotal mass most likely rhabdomyosarcoma from spermatic cord or epididymis.

  • Pure yolk sac tumour (endodermal sinus tumour; cf mixed YST in adults) – most common <3yo. Raised AFP. May involve testis, ovary or other sites eg mediastinum.
  • Leydig cell tumour 4-5yo.
  • Sertoli cell tumour <6/12.
  • Gonadoblastoma in intersex pts, from gonadal streaks or intra-abdominal testes.

Acute Scrotum

  • Testicular torsion – decreased/absent testicular blood flow, asymetrical enlargement, slightly reduced echogenicity, hyrocoele, spiral configuration of spermatic cord, heterogeneity or focal hypoechoic areas suggest haemorrahge and necrosis (late). Preservation of the testis only possible in 6-10hrs.
  • Epididymoorchitis – increased colour flow, enlarged and hypoechoic testicle and epidymitis. Reactive hydrocoele common. Usually no identifiable cause.
  • Torsion of the testicular appendage – echogenic mass >5mm between superior pole of testis and epididymis. Periappendiceal hyperaemia, normal testicular flow. Self-limited.
  • Testicular haematoma from trauma – avascular mass with abnormal echogenicity. Haematocoeles common.


Congenital hydrocoele from patent processus vaginalis, usually closes spontaneously with resolution of hydrocoele by 2yo. Acquired hydrocoele from testicular inflammation, trauma or torsion.

Undescended Testis

Common (3-4% term boys), most spontanteously descend by 1yo leaving ~1% with cryptorchidism. In 3-5% testis congenitally absent. Descent after 1yo unlikely. Most sporadic, some associated with other GUT anomalies eg hypospadias. Bilateral in 25%. Most (70-80%) in inguinal region (from arrested inguinoscrotal phase) seen on US. Only 5-10% are abdominal, from arrested transabdominal phase, best seen with MRI; may be anywhere from lower pole kidney to superficial inguinal ring. Most are atrophic from progressive tubular atrophy starting from 2yo (down to 10mm), relatively hypoechoic. DDx bulbous termination of gubernaculum (=pars infravaginalis gubernaculi); gubernaculum (cordline guide to descent) atrophies after normal descent, persists as fibrous/gelatinous mass when incomplete. Tx orchidopexy by 2yo to preserve fertility. Long-term cryporchidism increases risk of testicular cancer esp seminoma, also increased risk in the normally descendedg contralateral testis. Associated with inguinal hernia in 10-20%.

Ovarian Neoplasm

Ovarian dermoid (mature teratoma) – cystic or solid with internal cystic components, fluid-fluid levels, fat, calcifications. Tooth pathognomonic. Malignant teratomas associated with ascites, intraperitoneal spread, liver mets, larger solid component.

Less common ovarian neoplasms incl dysgerminoma, cystadenoma, cystadenocarcinoma, granulosa cell tumour.

DDx infection and abscess from pelvic inflammatory disease, ectopic pregnancy.

Ovarian Cysts

Follicular or corpus luteum cysts common (maternal stimulation), most asymptomatic and resolve. Round/oval, anechoic, thin rim. Cx haemorrhage (echogenic, complex), torsion (esp large >50mm).

Congenital Vaginal Obstruction

Vagina and uterus dilate with fluid in response to hormonal stimulation in inflancy 20 to maternal hormones or puberty. Hydrometrocolpos – fluid distension of uterus and vagina. Haematometrocolpos – after menarche. Tubular/elliptical midline mass. Markedly dilated vagina represents bulk of mass.

Pelvic Rhabdomyosarcoma

Often from bladder trigone, prostate, anterior vaginal wall, spermatic cord, paratesticular tissues, uterus or perineum. May also arise from head and neck. Usually large at presentation, highly malignant, <3yo. Infiltrates pelvic floor and surrounding tissues. Polypoid/grapelike mass -> bladder elevation and bladder neck obstruction, may -> hydronephrosis.



Range from mature (benign, well-defferentiated cystic), immature teratomas (indeterminate potential), malignant teratomas (usually mixed with another germ cell tumour eg endodermal sinus tumour). Peaks at 2yo (congenital lesions) then late adolescence/early adulthood.

  • Sacrococcygeal teratoma (most common) – 10% associated with anomalies of hindgut and cloacae, other midline defects (meningocoel). 75% mature, 12% unequivocally malignant. Most <4/12 old, older tend to be more malignant. Grade I mostly externally; II external with intrapelvic mass (dumbell-shaped); III mostly internal with pelvic and abdominal mass; IV only in presacral space. Polyhydramnios and haemorrhage, fatal hydrops. Usually large extending from coccyx, deformity of sacrococcyx. Variable cystic, solid and fatty components. Amorphous or formed calcs (eg teeth).
  • Testis
  • Ovaries
  • Other midline locations including mediastinum, retroperitoneum, H&N (suprasellar, pineal region).


Rare primary presacral tumour. Better prognosis than upper abdominal. Amorphous calc.

Sacral Chordoma

Rare, from remnants of primitive notocord. Destruction and expansion of sacrum. Flocculant calc. Heterogeneous enhancement.

Anterior Sacral Meningocoele

Thecal sac protruding into presacral space via sacral defect, associated with cresent-shaped deformity of sacrum (scimitar sacrum). Uni/multi-locular. Associated with cord tethering. Currarino triad = partial sacral agenesis, anorectal stenosis, presacral mass. Associated with neurofibromatosis.

Anterior Abdominal Wall Abnormalities

  • Omphalocolele – midline defect with failed fusion of lateral folds. Herniated contents (bowel, liver) covered by sac of peritoneum. 2/3 associated with other anomalies esp cardiac, chromosomal.
  • Gastroschisis – defect lateral to midline. Herniated content (usually bowel) not covered by membrane, exposed to amniotic fluid which is toxic to bowel -> severe dysmotiilty problems, intermittent pseudoobstruction. Not associated with other anomalies.
  • Cloacal exstrophy – bladder extrophy and omphalocole, diastasis of pubic bones, spinal dysraphism, ± hydrometrocolpos. Compression on distal ureters may -> renal failure.


Solid organ injuries in liver, splen, kidney, adrenals and pancreas; multiple organs in 21%. Surgery reserved for unstable pts; size and appearances of injury inaccurate predictors (except active extravasation).

  • Pancreatic injury – most sensitive finding fluid betw splenic ven and pancreas. Linear hypodensity.

Bowel injury – focal wall thickening with prominent enhancement, mesenteric stranding, unexplained free fluid. More specific findings less common incudingl free gas (esp in vicinity of injury), active extravasation of enteric contrast.

  • Intramural duodenal haematoma – most common acquired duodenal obstruction. From blunt abdo trauma, haemophillia, Henoch-Schonlein purpura. Asymmetric/concentric wall thickening esp D3. Confirmed with contrast duodenography. Laceration -> retroperitoneal gas/fluid.
  • Hypoperfusion complex (‘shock bowel’) – from hypovolaemic shock, masked in children for longer due to more pronounced peripheral vasospasm and tachycardia. Intense enhancement or bowel wall mesentery, adrenals, liver, kidneys and pancreas. Intense enhancement with reduced calibre of IVC and aorta. Diffusely dilated fluid-filled bowel. May be seen before clinical shock.

Mesenteric Abnormalities

Mesenteric processes cause partial/complete envelopment of SMA/SMV, peripherally displaced bowel loops, extension from superocentral to inferoperipheral in cone-like manner.

  • Mesenteric rotational abnormalities
  • Diffuse mesenteric process – oedema, haemorrhage, inflammation. Normal fat replaced with soft tissue, loss of vascular definition.
  • Focal mass – lymphoma, mesenteric cysts (lymphatic malformation failing connections with central lymphatics, can be multiseptated and large), desmoid, teratoma, lipoma.
  • Multifocal mass – lymphadenopathy (>5mm), malignant (lymphoma esp NHL, lymphoproliferative disorder, mets) or inflammatory (infection eg Tb, cat scratch, fungal; favoured if central low attenuation with peripheral enhancement).
  • Mesenteric adenitis – Self-limiting benign inflammed mesenteric nodes ± enteritis, usually viral. Cluster enlarged LN in RLQ (ant to R psoas or SB mesentery) with normal appendix, increased vascularity, occasionally mild mucosal thickening distal ileum and caecum. Giant mesenteric adenitis -> masslike RLQ. Prominent nodes <5mm in inferior mesenteric and RLQ are no clinical significance.