Intestinal obstruction results from mechanical blockage or the loss of normal peristalsis. Adynamic or paralytic ileus is more common and usually self-limiting. Common causes of mechanical small bowel obstruction (SBO) are adhesions due to previous surgery, incarcerated hernias, or inflammatory diseases. Other causes to consider are inflammatory bowel diseases, congenital anomalies, and foreign bodies. The most frequent causes of large bowel obstructions are cancer, diverticulitis with stricture, sigmoid volvulus, and fecal impaction. Consider intussusception in children. Sigmoid volvulus is more common in the elderly taking anticholinergic medications while cecal volvulus is more common in gravid patients. Intestinal pseudoobstruction (Ogilvie syndrome) may mimic large bowel obstruction. The elderly and bedridden and patients taking anticholinergic medications or tricyclic antidepressants are at increased risk for pseudoobstruction.
Crampy, intermittent, progressive abdominal pain and inability to have a bowel movement or to pass flatus are common presenting complaints. Vomiting, bilious in proximal obstructions and feculent in distal obstruction, is usually present. Patients with partial SBO can still pass flatus. Physical signs vary from abdominal distention, localized or general tenderness, to obvious signs of peritonitis. Localization of pain and the presence of abdominal surgical scars, hernia, or masses may provide clues to the site of obstruction. The abdomen may be tympanitic to percussion. Active, high-pitched bowel sounds can be heard in mechanical SBO. Bowel sounds may be diminished or absent if the obstruction has been present for many hours. Rectal examination may demonstrate fecal impaction, rectal carcinoma, or occult blood. Key features of ileus and mechanical bowel obstruction are described in Table 45-1. The presence of stool in the rectum does not exclude obstruction. Consider a pelvic examination in women. Systemic symptoms and signs depend on the extent of dehydration and the presence of bowel necrosis or infection.
DIAGNOSIS AND DIFFERENTIAL
Suspect intestinal obstruction in any patient with abdominal pain, distention, and vomiting, especially in patients with previous abdominal surgery, abdominal/pelvic radiotherapy, or groin hernias.
Flat and upright abdominal radiographs and an upright chest x-ray can screen for obstruction (see Fig. 45-1), confirm severe constipation, or diagnose hollow viscous perforation with free air. The diagnostic procedure of choice in the ED is CT scanning using IV and oral contrast when possible. CT scanning can delineate partial versus complete bowel obstruction, partial SBO versus ileus, and strangulated versus simple SBO.
Sigmoid volvulus. Note that the open portion of the “C” formed by the twisted large bowel points toward the left side in the case of sigmoid volvulus. Reproduced with permission from Wikiradiography.com.
Laboratory tests may include a complete blood count, electrolytes, blood urea nitrogen, creatinine, lactate levels, coagulation profile, and type and cross-match. Suspect abscess, gangrene, or peritonitis if leukocytosis > 20,000 or left shift is noted. An elevated hematocrit ...