Small Bowel ObstructionSCHWARTZ'S PRINCIPLES OF SURGERY; 9TH EDITION

Epidemiology

Most frequent surgical disorder of the small intestine Etiologies according to their relationship to intestinal

wall: 1. Intraluminal (e.g., foreign bodies, gallstones, or meconium)

2. Intramural (e.g., tumors, Crohn's disease–associated inflammatory strictures)

3. Extrinsic (e.g., adhesions, hernias, or carcinomatosis)

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75% of cases is caused by intra-abdominal adhesions related to prior abdominal surgery

Less prevalent etiologies include: hernias malignant bowel obstruction (extrinsic compression or invasion from neoplasms

arising in organs other than the intestine) and Crohn's disease

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Congenital abnormalities Usually become evident during childhood intestinal malrotation and midgut volvulus should not

be forgotten in adult patients especially in those without history of prior abdominal

surgery

Pathophysiology

In the onset, gas and fluid accumulate within the intestinal lumen proximal to the site of obstruction

Intestinal activity increases Colicky pain & Diahrrea

Where does the gas & fluid come from? Bowel distends and intraluminal and intramural pressures

rise Impair of intestinal microvascular perfusion Ischemia

Necrosis strangulated bowel obstruction

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partial small bowel obstruction only a portion of the intestinal lumen is occluded pathophysiologic events occur more slowly & strangulation

is less likely closed loop obstruction accumulating gas and fluid cannot escape Leading to a rapid rise in luminal pressure, and a rapid

progression to strangulation

Clinical Presentation

colicky abdominal pain, nausea, vomiting, and obstipation

Vomiting is more seen with proximal obstructions than distal In established obstructions you see vomitus more feculent Continued passage beyond 6 to 12 hours after onset of

symptoms is characteristic of partial obstruction Abdominal Distention is another sign, esp. if the

obstruction is in distal ileum, absent if in proximal small intestine

Bowel sounds

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Laboratory findings intravascular volume depletion consist of:

hemoconcentration and electrolyte abnormalities Mild leukocytosis is common Features of strangulated obstruction include: Odd abdominal pain, suggestive of intestinal ischemia tachycardia, localized abdominal tenderness, fever,

marked leukocytosis, and acidosis

Any of these findings must alert you to the possibility of strangulation Surgery

example

Chronic partial small bowel obstruction

several months' history of chronic abdominal pain, and intermittent vomiting

dilated segment shows evidence of fecalization

Diagnosis

Focus on the following goals:

(a) distinguish mechanical obstruction from ileus

(b) determine the etiology of the obstruction

(c) discriminate partial from complete obstruction

(d) discriminate simple from strangulating obstruction

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Important elements to obtain on history: prior abdominal operations (suggesting the presence of

adhesions) abdominal disorders (e.g., intra-abdominal cancer or

inflammatory bowel disease) hernias (esp. in inguinal & femoral regions) Blood in Stool (Strangulation)

Radiographic Examination

Abdominal series in X-ray:

(1) Abdomen Supine,

(2) Abdomen Upright,

(3) Chest Upright.

most specific triad for small bowel obstruction:

dilated small bowel loops (>3 cm in diameter)

air-fluid levels

a paucity of air in the colon

Specificity of plain Radiography is low (ileus and colonic obstruction)

False-negative (proximal of small intestine OR filled with fluid but no gas)

CT-Scan

a discrete transition zone with: dilation of bowel proximally, decompression of bowel

distally, intraluminal contrast that does not pass beyond the

transition zone, and a colon containing little gas or fluid Closed-loop obstruction U-shaped or C-shaped dilated bowel loop mesenteric vessels converging toward a torsion point Strangulation (thickening of the bowel wall, pneumatosis

intestinalis)

Therapy

marked depletion of intravascular volume decreased oral intake, vomiting, and sequestration of fluid in bowel lumen and wall

IV fluid and bladder catheter(urine output) Broad-spectrum antibiotics NG tube (decreases nausea, distention, and the risk of

vomiting & aspiration)

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