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296
9 US of the Gastrointestinal (GI) Tract
Bezoars and Foreign Bodies
Bezoars usually nicely assessable by US, foreign bodies if stomach fi lled
suffi ciently.
Appearance depends on content, bezoars typically with very echogenic surface
without sound penetration.
Hyperplastic Gastric Mucosa
Similar to gastritis – also potentially diffi cult to see.
May cause gastric outlook obstruction (severe mucosal thickening, young age –
typically neonates under prostaglandin therapy for PDA).
Menetrier’s Disease: Giant Hypertrophy of Gastric Mucosa
Typically affecting older children.
US Findings
• US may exhibit irregular thickened echogenic mucosa, particularly in fundus
and body of stomach.
• Gastric muscle may also be thickened and hyperechoic.
• Secondary fi ndings due to hypoproteinaemia (protein loosing enteropathy), such
as oedema, ascites and pleural effusions.
Eosinophilic Gastr(oenter)itis
Not differentiable from other types of gastritis – thickening of stomach wall including pyloric muscle, elongation of pyloric canal – may mimic pyloric stenosis.
Gastric Perforation
Complex regional fl uid collections at site of perforation.
• Secondary changes such as ascites, peritoneal abscess and
pneumoperitoneum.
• Often underlying focal stomach changes may become visible, e.g. thickened
wall, (“ring-down”) artefact at site of perforation.
Granulomatous Disease
Any granulomatous disease may affect stomach.
• Chronic granulomatous disease of childhood (x-linked disorder) most common
Findings include lymphadenopathy, hepatosplenomegaly, abdominal pain and
potentially pneumonia.
Stomach most commonly involved part of GI tract.
• Seen as circumferential wall thickening and luminal narrowing.
• May appear as benign masses in stomach wall.
Duplication Cysts
Characterised by its wall “gut signature” (see below – bowel), exhibiting typical wall structure of related part of intestine. May have a connection with
lumen.
9.1 Stomach
297
US Findings
• Usually unilocular cystic thick-walled lesions (see Fig. 9.13 ). Have comon blood
supply with organ of origin, move together with organ or its peristalsis.
• Content echogenicity may change secondary to haemorrhage, infection, proteinous debris, epithelial cells and sediment.
• Size variable – if connection with bowel lumen (see Fig. 9.14 ).
Teratoma
Rare. Depending on histological composition may exhibit complex structure or
appear purely cystic with nodular solid components/wall.
There may be calcifi cation, bone, fat, and secondary changes.
Focal Foveolar Hyperplasia
Rare gastric mass due to obstruction or infl ammation of gastric fovea (pits in
mucosa, where gastric glands empty).
US Findings : Echogenic polypoid masses in mucosal location.
Inflammatory Pseudotumour
A benign infl ammatory pseudo-tumorous mass, commonly in greater curvature
(also called plasma cell granuloma or fi broxanthoma).
US Findings
• Often poorly defi ned with mixed echogenicity and secondary haemorrhage or
necrosis.
• Rare diffuse manifestation with diffuse hypervascular wall thickening – with
regionally enlarged nodes.
Other Benign Tumours
Many entities possible, though extremely rare (e.g. myofi broma, polyps, haematoma, neuromyoma, neurofi broma, haemangioma and lipoma).
US Findings : Tumour visible – entity cannot be defi ned/distinguished.
Diagnosis usually requires biopsy.
Malignant Masses
Most commonly lymphoma or gastrointestinal stroma tumours (GIST) – both manifest as single or multifocal masses.
US Findings
US depicts polypoid tumour or focal wall thickening that may mimic any other
space occupying lesion:
• Lymphoma: mass usually hypoechoic to normal gastric wall echogenicity, exhibits changes such as splenomegaly and enlarged lymph nodes, often relatively
large tumour at diagnosis.
• GIST: smaller at diagnosis, often heterogeneous and echogenic masses with
nodular and cystic areas (haemorrhage, necrosis).
Other rare gastric wall tumours: leiomyosarcoma, carcinoma (as familial/inherited
condition).
Diagnosis relies on histology.
298
9 US of the Gastrointestinal (GI) Tract
9.1.7 Role of US
May depict fi ndings, but less reliable for ruling out conditions or specifi c entity
diagnosis – except for GOER, HPS and duplication cysts.
Additional Investigation : Endoscopy, MRI/CT, for some condition fl uoroscopy and
biopsy.
9.2 Bowel
9.2.1 Preparation and Requisites
Indications
Suspected intussusception, volvulus, necrotising enterocolitis, intestinal HenochSchonlein purpura, appendicitis, infl ammatory bowel disease (Crohn’s, ulcerative colitis, etc.), bloody diarrhoea, acute abdomen (e.g. after trauma), other
nonspecifi c queries, familial conditions (intestinal polyposis), during chemotherapy, etc.
Preparation and US Options
• Acute US performed without specifi c preparation, particularly in query intussusception, volvulus and appendicitis.
• Visualisation improved by oral fl uid intake, potentially with some distending
substances (as also used for MR-enteroclysis) – this allows proper distension and
good visualisation of lumen, detection of stenotic areas and intraluminal pathology such as polyps.
• Rectal enema (hydrocolon – “US enema”) with warmed saline solution, improves
assessment of colon, can also be used therapeutically for reduction of intussusception or meconium ileus (see Chap. 2 ).
• Perineal access (after enema) for assessment of defecation and rectal/anal stenosis/atresia/malformation. Sometimes enema improves visualisation of fi stulae in
infl ammatory bowel disease or complex malformations.
• Graded compression technique advised, positioning manoeuvres helpful for
transporting fl uid to area of interest.
Positioning
Usually supine, relaxed abdominal wall musculature helpful (can be achieved by
support to knees).
Transducers
• Linear transducers with highest achievable frequency for optimal resolution
helpful.
• Curved linear arrays allow better overview, or extended view techniques. Sector
transducers rarely helpful.
9.2 Bowel
Fig. 9.5 Schematic drawing of bowel appearance with respective typical pathology. Left side :
schematic drawing to demonstrate typical bowel features that may help to identify the various
bowel segments; this may physiologically not apply to (preterm) neonates due to immaturity (no
typical haustrae). Right side : typical schematic US appearance of common pathology of respective
bowel section
• Frequency depends on patient age and position of targeted bowel segment. The
smaller and the closer to surface, the higher the frequency (e.g. in neonates
15 MHz, in school children for appendiceal assessment 10–5 MHz).
299
9.2.2 Course of Investigation
Approach
• Transabdominal + perineal.
• Also access from fl ank and through full bladder/full stomach.
Orientation
• Helpful to fi rst assess in organo-axial section.
• Identify well-defi ned structures (e.g. pylorus, gastro-oesophageal junction, coecum, rectum).
• Follow respective loops continuously from distal to proximal.
• Assess bowel wall (thickness, structure), size (stenotic part?), peristalsis and
compressibility.
• Assess lumen and content. Bowel structure may help identifi cation (jejuna folds,
colon haustrae, etc., Figs. 9.5 and 9.6 ).
• Add longitudinal sections for documentation of inner contour (folds) and assessment of stenotic segments (extended fi eld of view helpful).
• Always assess surrounding structures (mesentery, lymph nodes, etc.).
300
abc
Fig. 9.6 Contour of different bowel partitions. ( a ) US appearance of normal proximal jejunum
with typical folds (fl uid fi lled). ( b ) Normal fl uid-fi lled ileum: no folds, no haustrae. ( c ) Fluid-fi lled
colon: haustrae can nicely be visualised
9 US of the Gastrointestinal (GI) Tract
• Finally, add CDS for assessing bowel wall vasculature and main feeding vessels;
in some applications (e.g. NEC), assessment of mesenteric artery/vein and coeliac trunk helpful.
• Complete investigation by sampling relevant vessels for spectral analysis of
Doppler fl ow profi le.
NOTE : Modern tools helpful (harmonic imaging, high-resolution imaging, perineal
US, image compounding, graded compression, etc.). High-contrast preset advisable
(to be changed for assessing subtle alterations of wall structure).
9.2.3 Normal US Findings
Typical stratifi ed bowel wall, “gut signature”: at least three, often fi ve layers depictable – echogenic superfi cial mucosa, hypoechoic deep muscular mucosa, echogenic
submucosa, hypoechoic muscle and echogenic serosa (Fig. 9.7 ).
• Bowel wall thickness varies with distension and age; in older children cut-off is
a thickness of 3 mm for small bowel and 4 mm for is colon.
• Inner contour varies with segment: multiple deep folds in jejunum, less and
smaller folds in ileum and haustrae (including outer contour) in colon.
• Peristalsis: regular and propulsive in small bowel, rare in colon, documented by
M-Mode or video clip (Fig. 9.7b ).
• Bowel lumen variable – depends on alimentation, gaseous content, etc., normally
good compressibility.
• Doppler: depends on splanchnic activation – if fasted neonatal normal value of
SMA fl ow in newborns = 40–60 cm/s. RI > 90 %; then gradually changing
towards adult values within fi rst years of life.
9.2.4 Pathology
9.2.4.1 Congenital Anomalies
Most important: various forms of atresia and stenosis, position anomalies by malfi xation and malrotation, enteric duplications and Meckel’s diverticulum.
9.2 Bowel
ab c
Fig. 9.7 US appearance of bowel wall and peristalsis. ( a ) Normal bowel wall stratifi cation seen
non-high magnifi cation: at least three layers recognisable (with modern high-resolution transducers
even fi ve): hypoechoic inner “mucosa”, echogenic “submucosa” and hypoechoic muscle. ( b )
M-Mode used to document the intense and irregular small bowel peristalsis in a child with gastroenteritis and thus fl uid-fi lled loops with some ascites. ( c ) Bauhin’s valve visualised after saline enema
301
Fig. 9.8 Saline enema – hydrocolon for small left colon. Axial section left upper quadrant: fl uid-
fi lled narrow/small left colon (seen as circular thin-walled structure on left upper image corner)
after saline enema; small bowel loops distended and fi lled with echogenic meconium. Some ascites
Usually suspected by prenatal US; postnatally often only plain fi lm is suffi cient,
complemented by US and in some conditions fl uoroscopy (enema, upper GI series,
follow-through).
Atresia
Defi nition
Congenital occlusion or high-grade stenosis of bowel lumen.
US Findings
• Proximal fl uid-fi lled distended bowel loops, sudden change in diameter at
obstruction, collapsed loops in distal parts.
• In high atresia (duodenum, jejunum), meconium may be present in distal parts.
• In distal atresia bowel without meconium and narrow (“unused bowel”) – such a
small colon may be conspicuously visualised after saline enema (Fig.
9.8 ).
NOTE : In stenosis or webs with central perforation, some residual content and
distension of distal bowel loops may be present. US may show these fi ndings – usually not necessary. Annular pancreas diffi cult to prove on US, usually diagnosed
intraoperatively.
302
abc
Fig. 9.9 Perineal US in anal atresia/stenosis. ( a ) Narrow anal canal with dilated rectum. ( b )
Abnormal course and fi stula-like tract form rectal pouch to anal grove in intermediate anal atresia
nicely visualised by sagittal perineal scan. ( c ) Dotted line outlines long atretic anal canal in high
anal atresia – from anal grove (+) to rectal pouch
9 US of the Gastrointestinal (GI) Tract
• In high atresia – after plain fi lm with clinical symptoms – direct surgery without
further imaging performed.
• Sometimes in low atresia or equivocal fi ndings (e.g. stenoses/webs with partial
obstruction and annular pancreas) US or bowel follow-through requested.
Special Application – Anal Atresia :
• Potential fi stulae and length of atretic segment assessed by perineal US applying
measurements (as in radiographs), classifi ed as low (<1 cm), intermediate
(1–2 cm) and high (>2 cm) essential for planning treatment (Fig. 9.9 ). Dynamic
assessment of defecation achievable in stenosis/for DDx Hirschspring disease provided rectum can be fi lled with saline enema (see Fig. 2.2 ).
• Sometimes pelvic fl oor muscles may be appreciated – more easily assessable by
3DUS with reconstructions, if suffi cient access and resolution available.
• US enema combined with US genitography (and ce-VUS) can enable thorough
sonographic work-up of even more complex cloacal malformations (supplemented by fl uoroscopy for some queries, sometimes MRI, or ce-CT).
Malrotation
Defi nition
• Atypical rotation/insuffi cient fi xation of gut – potentially with resulting (intermittent) obstructive symptoms. Based on incomplete fetal rotation of foregut.
US Findings
• Relation of mesenteric vessels at mesenteric root – typically mesenteric vein to
the right of superior mesenteric artery (in front of aorta) (Fig.
9.10 ).
• Duodenum normally crossing retroperitoneally (behind mesenteric vessels).
NOTE : Atypical position of mesenteric vessels not diagnostic, as rotation anoma-
lies may coexist with normal upper vessel position, and normal rotation may be
present in spite of inverse vessel relation.
• Diagnosis: Demonstration of abnormal position of duodeno-jejunal fl exure (after
fi lling stomach/duodenum) by US or fl uoroscopy (upper GI study).
• Malposition of colon most easily seen after hydrocolon – inverse position of
descending colon, wrong position of (mobile?) coecum. Cannot be used for diagnosing malrotation.
9.2 Bowel
abc
Fig. 9.10 Mesenteric vessels/malrotation. ( a ) Normal position of superior mesenteric vein ( left , in
front of IVC) and artery ( right , surrounded by a small collar of echogenic fat). ( b , c ) Inverse posi-
tion of mesenteric vessels in malrotation on gray scale ( b ) and CDS ( c , artery on patient right/
image left side encoded in red , vein encoded in blue )
ab
303
Fig. 9.11 Whirlpool sign – volvulus. ( a ) Gray scale appearance of volvulus: central vessel
(artery), circular swirling tissue and vascular structures. ( b ) CDS of same patient: whirlpool-like
spiral vessels coursing around central superior mesenteric artery more clearly depictable and convincingly obvious
NOTE : Physiologically elongated, right-sided sigmoid loop (particularly in preterm babies) does not indicate malrotation; normal position of colon does not
exclude small bowel malrotation.
Most important complication – volvulus.
Volvulus
Defi nition
• Cork screw-like torsion of upper small bowel around mesenteric root, leading to
vascular compromise and bowel ischemia/haemorrhagic infarction.
• Commonly presents in fi rst weeks/months of life as surgical emergency.
US Findings
• Prestenotic dilated, fl uid-fi lled duodenum with abrupt disruption by pseudotumorous structure, formed by clockwise twisted dilated superior mesenteric vein
curling around more centrally positioned superior mesenteric artery – whirlpool
sign (Fig. 9.11 ). More or less echogenic mesentery and bowel.
304
ab
Fig. 9.12 Hirschsprung and constipation. ( a ) Dilated colon with echogenic content in infant with
Hirschsprung. Some ascites. ( b ) Child with severe constipation: very echogenic colon content with
shadowing – consistent with huge coprolith (similar appearance seen with bezoars)
9 US of the Gastrointestinal (GI) Tract
• Depending on severity and duration: peritoneal fl uid, thickened echogenic bowel
wall with haemorrhage and oedema.
NOTE : US diagnostic, once whirlpool sign seen – do not waste time with further
imaging. In equivocal situations emergency fl uoroscopy should be performed to
establishing the diagnosis. US less reliable for ruling out (partial, intermittent,
chronic) volvulus/malrotation – only if course of duodenum and position of duonojejunal junction clearly visible US diagnostically valid (see above).
Hirschsprung Disease/Neuronal Intestinal Dysplasia (NID)
Defi nition
• Lack of colonic ganglion innervation with consequent lack of peristalsis, leading
to constipation and dilatation; length of aganglionic segment varies.
• NID : milder innervation anomaly of colon – some transition in preterms due to
immaturity.
US Findings
• Impressive dilatation of stool-fi lled colon (megacolon) (Fig. 9.12 ), coprolith
(also with other severe constipation); sometimes transition zone with change in
calibre depictable.
• US enema improves depiction of and assessment of length of affected
segment.
• Complete investigation by perineal access.
NOTE : The aganglionic segment may be diffi cult to depict, very short segments
or very long segments may be missed (latter misinterpreted for chronic
constipation).
Diagnosis made by suction biopsy/histology; often manometry/defecography
performed preoperatively.
Duplication/Diverticula
Defi nition
• Double lumen with or without connection – wide connection may cause diffi culties in differentiating real enteric duplication from diverticula.
9.2 Bowel
ab c
Fig. 9.13 Bowel duplication. ( a ) Bowel duplication cyst – cystic structure with thick wall that
exhibits bowel stratifi cation (“gut signature”). ( b ) Child with gastric duplication cyst: fl uid-fi lled
structure adjacent to stomach at pre-pyloric area with bowel wall appearance, moves with stomach
during peristalsis. ( c ) Large simple cyst with thick multilayered wall adjacent to fl uid-fi lled duode-
nal loop coursing below which is compressed by the duplication cyst explaining the clinical symptoms of intermittent upper obstruction
• DDx: Any other abdominal cyst (mesenteric/ovarian cyst, meconium pseudocyst, pancreas pseudocyst), ascites, seroma, Meckel’s diverticulum, cystic lymphatic malformation/teratoma, covert perforation, etc.) – often differentiation
achievable by typical US features of enteric duplication’s wall structure.
US Findings
• Most common in stomach, duodenum and colon. Oesophageal/small bowel
duplications less common.
• Exhibit thick wall around cyst with typical gut wall structure (“gut signature”)
(Fig. 9.13 ).
• Usually adherent to adjacent (potentially compressed) bowel loop with common
vascular supply.
• Move concordant to intestinal peristalsis of respective bowel loop.
• May have sedimented internal echoes.
• If connection between duplication and bowel lumen, size may vary depending on
bowel content and fi lling – use peroral or rectal fi lling by tea/formula/saline
enema to enable diagnosis, air content possible (Fig. 9.14 ).
NOTE : Solid duplications with only minimal lumen rare, more diffi cult to depict.
305
Meckel’s Diverticulum
Defi nition
• Remnant of omphalo-enetric duct. May present as acute abdomen (query appendicitis), particularly after haemorrhage.
US Findings
• Cyst-like formation with gut-like thick wall (Fig. 9.15 ). Size may vary; shape/
content depends on size, potential haemorrhage (from ectopic gastric mucosa)
and potential connection to bowel lumen – otherwise similar to duplication cyst,
only commonly wall much thicker.
• Typically located right lower quadrant or situated along omphalo-enteric duct
tract.
• Commonly does not change position with bowel peristalsis, not compressible.