Intestinal obstruction exists when blockage prevents the normal flow of intestinal contents through the intestinal tract. Two types of processes can impede this flow.
Mechanical obstruction: An intraluminal obstruction or amural obstruction from pressure on the intestinal walls occurs. Examples are intussusception, polypoid tumors and neoplasms, stenosis, strictures, adhesions, hernias, and abscesses.
Functional obstruction: The intestinal musculature cannotpropel the contents along the bowel. Examples are amy-loidosis, muscular dystrophy, endocrine disorders such as diabetes mellitus, or neurologic disorders such as Parkinson’sdisease. The blockage also can be temporary and the result of the manipulation of the bowel during surgery.
The obstruction can be partial or complete. Its severity de-pends on the region of bowel affected, the degree to which the lumen is occluded, and especially the degree to which the vascu-lar supply to the bowel wall is disturbed.
Most bowel obstructions occur in the small intestine. Adhe-sions are the most common cause of small bowel obstruction, followed by hernias and neoplasms. Other causes include intus-susception, volvulus (ie, twisting of the bowel), and paralytic ileus. About 15% of intestinal obstructions occur in the large bowel; most of these are found in the sigmoid colon (Wolfe, 2000). The most common causes are carcinoma, diverticulitis, inflammatory bowel disorders, and benign tumors. Table 38-5 and Figure 38-6 list mechanical causes of obstruction and describe how they occur.
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