Small Bowel Obstruction (SBO)

The small bowel is markedly dilated. The colon, however, is collapsed. Small bowel obstruction is suspected.
Upper GI (UGI) with small bowel follow through
- confirms small bowel obstruction.
- Establishes the level of the obstruction.
- demonstrates irregularity in the antral region along
- the greater curvature of the stomach.
  - A history of prior "pancreatic disease" was elicited.
The radiographic appearance is classic for small bowel obstruction.

Discussion:

Although the differential diagnosis of bowel dilatation is wide, one must try to distinguish between ileus, whose treatment is usually medical and mechanical obstruction, whose treatment may be surgical.
Adynamic ileus may be
- Focal or diffuse.
- Associated with a variety of conditions including:
  - Trauma, surgery, electrolyte imbalance, drugs, medications, infection, pain.
  - Often with aging (pseudo-obstruction).
Mechanical Obstruction may be associated with
- Prior surgery (adhesions), primary and secondary carcinoma, hernias, intersusception, volvulus, inflammatory masses, "filling defects," external (e.g., ingested objects) vs. internal (incl. bezoars, polyps, gallstones, parasites), congenital abnormalities (incl. atresias, webs, septa, duplications, Hirschprung's).
Although it is often difficult to distinguish between ileus and mechanical obstruction, certain findings suggest mechanical obstruction including:
- Selective diation of a region of bowel, e.g., small bowel.
- Air-fluid levels at different heights in the same loop. (Implies bowel trying to "force past" an obstructing point.)
- "String of pearls," or stair-case of air in contiguous bowel. Sign may be equivalent to above.
- An appropriate clinical history.
- Follow-up films are useful.
Barium studies establish the diagnosis.
- Lower GI should be performed first to exclude colonic obstruction. If a colonic obstruction is present
  - UGI can obscure and delay the diagnosis.
  - Barium can harden in the colon proximal to the obstruction.
  - A tumor in the colon involve the small bowel extrinsically and cause obstruction.
CT scan can be useful in evaluating the area outside the bowel including lymph nodes and abdominal and pelvic viscera.

Ref:Eisenberg, Ronald L., Gastrointestinal Radiology, 2nd ed., Lippincott, Philadelphia, PA., 1990, pp. 281-290, 411-429, 722-740.

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