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Small Intestine

  1. Small Bowel Obstruction
    1. Mechanical small bowel obstruction normally causes small bowel dilatation, with an accumulation of both gas and fluid and a reduction in caliber of the large bowel.
    2. Diagnosis of small-bowel obstruction can be made on plain abdominal radiographs in 60–70% of patients. The distal ileum is the site of small bowel obstruction in most patients with normal or equivocal plain abdominal radiographs.


Small bowel

Large bowel

1.       Haustra



2.       Valvulae conniventes

Present in jejunum


3.       Number of loops



4.       Distribution of loops



5.       Diameter of loop



6.       Radius of curvature of loop


50 mm

7.       Solid faeces (only reliable sign)


May be +

  1. Dilated fluid-filled loops of small bowel may be seen as ‘sausage shaped’ soft tissue densities. “String of beads sign” (gas trapped between valvulae conniventes only when very dilated small bowel is almost completely fluid filled and it is virtually diagnostic of small bowel obstruction), “step-ladder” appearance in low obstruction (the greater the number of dilated bowel loops, more distal is the site obstruction) and the “concertina effect” in Jejunal obstruction are known features. Single/multiple loops of >2.5–3cm in diameter with three air fluid levels in erect film (candy-cone appearance) is a helpful feature.
  2. Enteroclysis is proving to be reliable for investigating suspected small bowel obstruction and can differentiate postoperative obstruction from ileus.
  3. small intestine proximal to the site of obstruction and collapsed loops of small intestine or colon distal to the site of obstruction.
  1. Although Enteroclysis is more reliable in patients with partial, incomplete and intermittent obstruction, CT is now recommended as the technique of choice for the investigation of suspected intestinal obstruction. Small intestinal obstruction is differentiated from paralytic ileus on CT by demonstrating a transitional zone between dilated loops of small intestine proximal to the site of obstruction and collapsed loops of small intestine or colon distal to the site of obstruction.
  2. Sigmoid Volvulus: The Plain radiographic features :
    1. Inverted U shaped massively distended colonic loop.
    2. Liver overlap sign (ahaustral margin overlapping lower border of liver
    3. shadow)
    4. Left flank overlap sign (ahaustral margin overlapping haustrated,
    5. dilated descending colon)
    6. Pelvic overlap sign (ahaustral margin overlapping the left side of pelvis)
    7. D10 overlap sign (apex of volvulus lying very high in abdomen, above D10 level on left side)
    8. Apex under left hemidiaphragm
    9. Inferior convergence sign on left side of pelvis (inferiorly, where the two limbs of loop converge, three white tines meet, representing the two outer walls and the contiguous inner walls of twisted loop).
    10. A fluid ratio greater than 2%.


Extra Edge

The strangulated loop may contain gas, and arms of loop, separated only by the thickened intestinal walls, resembling a large coffee-bean (Coffee-bean sign).


QCT scan signs of strangulated obstruction include:
- Wall thickening of affected loop         
- High attenuation in bowel wall (due to hemorrhage)
- Gas in bowel wall                                    
- Mesenteric congestion
- Mesenteric hemorrhage
  1. Malabsorption
    There are 4 Radiologic groups of findings in Small Intestinal Malabsorption, related to alteration in:
    1. Peristalsis → variable peristalsis is hallmark with hypo and hypertonic segments, overall leading to increased transit time and segmentation of barium.
      1. However transit time may be long/short/normal.
      2. Painless transient intussusception may be seen on fluoroscopy.
    2. Caliber → dilatation of segments of bowel coils in 80% cases (>3 cm).
    3. Secretions → increased secretions cause dilution of barium and later clumping, segmentation and flocculation of barium.
    4. Mucosa → Edematous mucosa with thickened valvulae conniventes giving ‘Cog-wheel’ pattern (colonization of jejunum), instead of their normal ‘Feathery’ pattern; later atrophy occurs and mucosal folds disappear with thinning of bowel wall.
      1. Absence of valvulae: “Moulage sign” characteristic of sprue
      2. Valvulae conniventes may exhibit five types of appearances:
        1. Normal
        2. Squared ends
        3. Thickening of valvulae
        4. Reversed jejunoileal pattern
        5. Absence of valvulae conniventes: “moulage sign” characteristic of sprue
  2. Hirschsprung’s disease
    It is a form of functional bowel obstruction, which is due to failure of caudal migration of neuroblasts in the developing bowel causing the distal large bowel from the point of neuronal arrest to the anus, aganglionic.
    1. Four forms:
      1. Ultra-short segment disease (rare) affects only anal canal at the level of internal sphincter
      2. QShort segment disease (75% cases) affects only rectosigmoid region
      3. Long segment disease affects variable portion of colon proximal to sigmoid
      4. Total aganglionosis coli affects entire colon and part of terminal ileum.
Neonates of Hirshprung’s disease present with abdominal distension, vomiting and failure to pass meconium. Children who present in childhood later have history of constipation and failure to thrive.
  1. Imaging Features:
    1. Abdominal radiograph:
      1. Typically shows a low bowel obstruction commonly with colonic dilatation out of proportion to small bowel.
      2. Absence of rectal gas may be seen.
      3. Pneumoperitonium may be seen in 5% cases.
      4. Intraluminal small bowel calcifications (enteroliths) in long segment disease.
    2. Water-soluble contrast medium/Barium enema:
      1. Most vital film is a lateral view of the rectum during slow filling.
      2. Cone-shaped transition zone, abnormal i.e. reversal of rectosigmoid ratio (normal is >1) and irregular/tertiary rectal contractions are diagnostic features. Q
      3. The radiological transition zone is commonly found distal to pathological zone.
    3. QRectal biopsy: A section or full thickness rectal biopsy is required for the definitive diagnosis of Hirschsprung's disease.
  1. Necrotizing enterocolitis (NEC)
    1. Most common life threatening emergences of GIT in newborns
    2. QPreterm infants particularly susceptible (Greatest Risk Factor)
    3. Etiology: Triad of intestinal ischemia, oral feedings and pathogenic organisms has been linked to NEC.
    4. Onset of NEC occurs usually in first 2 weeks but as late as 3 month of age in VLBW babies.
    5. QFirst signs are gaseous abdominal distention and gastric retention.
    6. QPersistent loop sign may be seen
    7. QPneumatosis intestinal → diagnostic of NEC (Most common in R)
    8. Gas in portal vein is a sign of severe disease
    9. Gross pneumoperitoneum can occur if perforation occurs
    10. Post NEC strictures may occur, in splenic flexure in less severe cases
    11. Risk of NEC is significantly low in infants on exclusive breastfeeding
    12. Treatment includes Cessation of feeding, nasogastric decompression, IV fluids, antibiotic, removal of umbilical catheter if any.
  2. Ischemic colitis:
    Q'Thumb-printing' appearance of the submucosal thickening due to edema and hemorrhage with its crescentic margins has been used to describe ischemic colitis,
    Ischemic colitis most often affects splenic flexure and proximal descending colon.
    It is of three types → transient, stricturing, and gangrenous.
    1. Features of acute mesenteric ischemia or mesenteric thrombosis causing small bowel infarction include:
      1. Gas-filled, slightly dilated loops of small bowel with multiple air-fluid levels
      2. Thickened walls of small bowel loops due to submucosal hemorrhage and edema
      3. Linear gas streaks (if gangrenous)
      4. Free gas (if perforated)
Extra Edge

If bowel ischemia is suspected on CT, one should assess the patency of the celiac artery, superior mesenteric artery, inferior mesenteric artery, portal vein, superior mesenteric vein, and inferior mesenteric vein. When the central superior mesenteric vessels are affected, the entire small bowel, along with the large bowel proximal to the distal third of the transverse colon, tend to be affected. When the central inferior mesenteric vessels are affected, the distal third of the transverse colon, the descending colon, and the sigmoid colon are generally involved. 

  1. Crohn’s Disease (RegionalIleitis)
    1. Occurs any where along gut from mouth to anus
    2. Terminal ileum is most commonly affected
    3. Aphthoid/longitudinal/fissuring/rose-thorn ulcersQ
    4. Skip lesions
    5. Transmural involvement (distinguishing feature) Q
    6. Perianal fissure and fistulae
    7. Noncaseating granulomasQ
    8. Cobblestone mucosaQ
    9. “String sign” of Kantor on Barium enemaQ
    10. Multiple stricturesQ
    11. Enteroenteric, enterovesical fistulae
    12. Mesenteric inflammation, phlegmon, fibrofatty proliferation (Omega sign on Barium enema) Q
    13. Extracolonic manifestations and changes into carcinoma are less common as compare to UC
  2. Ulcerative colitis
    1. Inflammatory bowel disease.
    2. Rectum is always involved.
    3. Bloody diarrhea is the most common presentation. Q
    4. Double Contrast Barium Enema (DCBE) is the radiological examination of choice to show disease extent and severity
QInstant enema → In UC the large bowel is inflammed and contain no fecal matter, and hence enema study can be done without bowel preparation.
  1. Acute changes:
    1. Earliest radiological change on Double contrast barium enema is blurring of mucosal lining and a finemucosal granularity (ENFACE) due to EDEMA.
    2. Colorectal narrowing and incomplete filling due to spasm and irritability
    3. Scalloping of the edges of colon, especially the sigmoid colon
    4. Mucosal stippling due to crypt abscesses (continuous; not transmural)
    5. ‘Collar button’ ulcers
    6. Toxic megacolon
    7. Pseudopolyps
  2. Chronic changes:
    1. Shortening and narrowing of colon         
    2. ‘Lead pipe’ colon
    3. Loss of haustrations                                    
    4. Backwash ileitis
    5. Thickened rectal valve                               
    6. Widening of presacral space (normally 1.5 cm at s4 vertebral level)
    7. Benign stricture                                          
    8. Carcinoma of colon/rectum
  • Distinguishing Features Between Ulcerative and Crohn's Colitis
Radiographic feature Ulcerative colitis Crohn's disease
SB involvement Reflux ileitis only +++
Rectal involvement Always 50%
Multiple anal fistula - +
Aphthoid ulceration - +++
Fissuring ulceration - ++
Granularity +++ +
Transverse symmetry Symmetric Asymmetric
Longitudinal extent In continuity Discontinuous
Free perforation + -
Toxic megacolon + -/+
Cancer risk + -/+
Entero-enteric fistula - +
Submucosal fat ++ in chronic disease -
Mesenteric inflammation -/+ ++
Enlarged lymph nodes - +
Fibrofatty proliferation Mesorectal only ++
  1. Diverticulosis of colon
    1. It is characterized by herniation of mucosa and submucosa through the muscle layers of colonic wall.
    2. Most common after 7th decade of life.
    3. 80% occur in sigmoid colon.
    4. Barium Enema study may show:
      1. Q1.“Saw-tooth” sign (crowding and thickening of haustral fold)
      2. Bubbly appearance of air containing diverticulae.
      3. En face view may show circular line/ring shadow/meniscus with sharp outer edge and fuzzy/blurred inner margin or a fluid-barium level or barium pool and is extramural in location with absent QBowler’s hat sign as seen in polyps in oblique view.
  2. Anorectal malformations
    1. Early in its development, the cloaca is divided by a urogenital fold that causes separation of the urinary and gastrointestinal tracts. 1 It is abnormalities of this process that result in anal atresia and resultant fistulas between the proximal rectum and genitourinary tract.
    2. QThe traditional radiological approach for imperforate anus/anal atresia is inverted lateral radiograph (invertogram) of which a false interpretation film is obtained when the film is taken within first 6-24 hours of life, when there has been insufficient time for gas to reach the rectum or if infant had not been held prone for sufficient time to allow gas to reach tip of rectal pouch or there is impacted meconium. 
    3. MRI is the current choice for evaluating the cases of ARM.
Extra Edge

Air reaches in stomach within seconds after birth, enters small bowel within 1 hour, reaches caecum 3-4 hours after birth, and appears in sigmoid colon by 10-11 hours of birth.


Barium enema features of Ileocaecale tuberculosis
  1. Early involvement of the ileocaecal region manifesting as spasm and edema of the ileocaecal valve. Thickening of the lips of the ileocaecal valve and/or wide gaping of the valve with narrowing of the terminal ileum ("Fleischner" or "inverted umbrella sign") are characteristic.
  2. Fold thickening and contour irregularity of the terminal ileum, better appreciated on double contrast study.
  3. Conical caecum or "Amputed caecum" shrunken in size and pulled out of the iliac fossa due to contraction and fibrosis of the mesocolon. The hepatic flexure may also be pulled down.
  4. Loss of normal ileocaecal angle and dilated terminal ileum, appearing suspended from a retracted, fibrosed caecum ("goose neck deformity").
  5. Purse string stenosis-localized stenosis opposite the ileocaecal valve with a rounded off smooth caecum and a dilated terminal ileum.
  6. Stierlin's sign is amanifestation of acute inflammation superimposed on a chronically involved segment and is characterized by lack of barium retention in the inflamed segments of the ileum, caecum and variable length of the ascending colon, with a normal configured column of barium on either side. It appears as a narrowing of the terminal ileum with rapid emptying into a shortened, rigid or obliterated caecum.
  7. String sign-persistent narrow stream of barium indicating stenosis.
  8. Widening of IC angle is also a common feature.
    Enteroclysis followed by a barium enema may be the best protocol for evaluation of intestinal tuberculosis.
    String sign is also a Barium study feature of CHPS characterized by passing of small barium streak through pyloric canal seen as a string of barium.
The 'string of beads' sign on abdominal film, due to bubbles of gas trapped between the valvulae conniventes is seen only when very dilated small bowel is almost completely filled with fluid, and is virtually diagnostic of small bowel obstruction. It is not seen in normal people, after cathartics or following cleansing enemas.

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