small bowel obstruction
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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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