Morbidity and mortality from acute intestinal obstruction have been decreasing over the past several decades. Nevertheless, the diagnosis can still be challenging, and the type of complications that patients suffer has not changed significantly. The extent of mechanical obstruction is typically described as partial, high-grade, or complete—generally correlating with the risk of complications and the urgency with which the underlying disease process must be addressed. Obstruction is also commonly described as being either “simple” or, alternatively, “strangulated” if vascular insufficiency and intestinal ischemia are evident.
Acute intestinal obstruction occurs either mechanically from blockage or from intestinal dysmotility when there is no blockage. In the latter instance, the abnormality is described as being functional. Mechanical bowel obstruction may be caused by extrinsic processes, intrinsic abnormalities of the bowel wall, or intraluminal abnormalities (Table 323-1). Within each of these broad categories are many diseases that can impede intestinal propulsion. Intrinsic diseases that can cause intestinal obstruction are usually congenital, inflammatory, neoplastic, or traumatic in origin, although intussusception and radiation injury can also be etiologic.
TABLE 323-1Most Common Causes of Acute Intestinal Obstruction |Favorite Table|Download (.pdf) TABLE 323-1 Most Common Causes of Acute Intestinal Obstruction
|Extrinsic Disease |
|Adhesions (especially due to previous abdominal surgery), internal or external hernias, neoplasms (including carcinomatosis and extraintestinal malignancies, mostly commonly ovarian), endometriosis or intraperitoneal abscesses, and idiopathic sclerosis |
|Intrinsic Disease |
|Congenital (e.g., malrotation, atresia, stenosis, intestinal duplication, cyst formation, and congenital bands—the latter rarely in adults) |
|Inflammation (e.g., inflammatory bowel disease, especially Crohn’s disease, but also diverticulitis, radiation, tuberculosis, lymphogranuloma venereum, and schistosomiasis) |
|Neoplasia (note: primary small-bowel cancer is rare; obstructive colon cancer may mimic small-bowel obstruction if the ileocecal valve is incompetent) |
|Traumatic (e.g., hematoma formation, anastomotic strictures) |
|Other, including intussusception (where the lead point is typically a polyp or tumor in adults), volvulus, obstruction of duodenum by superior mesenteric artery, radiation or ischemic injury, and aganglionosis, which is Hirschsprung’s disease |
|Intraluminal Abnormalities |
|Bezoars, feces, foreign bodies including inspissated barium, gallstones (entering the lumen via a cholecystoenteric fistula), enteroliths |
Acute intestinal obstruction accounts for ~1–3% of all hospitalizations and a quarter of all urgent or emergent general surgery admissions. Approximately 80% of cases involve the small bowel, and about one-third of these patients show evidence of significant ischemia. The mortality rate for patients with strangulation who are operated on within 24–30 h of the onset of symptoms is ~8% but triples shortly thereafter.
Extrinsic diseases most commonly cause mechanical obstruction of the small intestine. In the United States and Europe, almost all cases are caused by postoperative adhesions, carcinomatosis, or herniation of the anterior abdominal wall. Carcinomatosis most often originates from the ovary, pancreas, stomach, or colon, although rarely, metastasis from distant organs like the breast and skin can occur. Adhesions are responsible for the majority of cases of early postoperative obstruction that require intervention. ...