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INTRODUCTION

Intestinal obstruction is the inability of the intestinal tract to allow for regular passage of food and bowel contents secondary to mechanical obstruction or adynamic ileus.

Mechanical obstruction is caused by either intrinsic or extrinsic factors. It requires identification of the cause and definitive intervention in a relatively short period of time to minimize morbidity and mortality (Tables 83-1 and 83-2). Adynamic ileus (paralytic ileus) is usually self-limiting and does not require surgical intervention.

TABLE 83-1Common Causes of Intestinal Obstruction
TABLE 83-2Key Features of Ileus and Mechanical Bowel Obstruction

Both large and small intestines may be obstructed by various pathologic processes (Table 83-1). Extrinsic, intrinsic, or intraluminal processes precipitate mechanical obstruction. Differentiating small bowel obstruction from large bowel obstruction is important, because the incidence, clinical presentation, evaluation, and treatment vary depending on the anatomic site of obstruction. Intestinal pseudo-obstruction (Ogilvie’s syndrome) may mimic bowel obstruction.1

PATHOPHYSIOLOGY

Normal bowel contains gas as well as gastric secretions and food. Intraluminal accumulation of gastric, biliary, and pancreatic secretions continues even if there is no oral intake. As obstruction develops, the bowel becomes congested and intestinal contents fail to be absorbed. Vomiting and decreased oral intake follow. The combination of decreased absorption, vomiting, and reduced intake leads to volume depletion with hemoconcentration and electrolyte imbalance and may lead to renal failure or shock.

Bowel distention often accompanies mechanical obstruction. Distention is due to the accumulation of fluids in the bowel lumen, an increase in intraluminal pressure with enhanced peristaltic contractions, and air swallowing. When intraluminal pressure exceeds capillary and venous pressure in the bowel wall, absorption and lymphatic drainage decrease, the bowel becomes ischemic, and septicemia and bowel necrosis can develop. Shock ensues rapidly. Mortality is high if bowel obstruction has progressed to this degree. This sequence of events may occur more rapidly in a closed-loop obstruction with no proximal escape for bowel contents. Examples of closed-loop obstruction include an incarcerated hernia and complete colon obstruction in the presence of a closed ileocecal valve.

SMALL BOWEL OBSTRUCTION

Small bowel obstruction accounts for most ...

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