Intestinal obstruction presents with acute abdominal pain, abdominal distension, and vomiting.
Abdominal radiographs can demonstrate obstruction, but computed tomography is more sensitive.
Intestinal obstruction is treated with intravenous fluids, nasogastric suctioning, antiemetics, narcotic pain medications, and antibiotics in select cases.
Strangulation is a complication of obstruction that can lead to bowel ischemia, peritonitis, and sepsis.
Intestinal obstruction refers to failure of intestinal contents to pass through the bowel lumen. Mechanical obstruction refers to physical blockage of luminal contents. This occurs in either small bowel (80% of cases) or large bowel (20% of cases). The most common cause of mechanical obstruction is adhesions from prior abdominal surgery (50%), followed by malignancy (20%), hernias (10%), inflammatory bowel disease (5%), and volvulus (3%).
Intestinal obstructions can be either partial or complete. Partial obstructions are often managed nonoperatively. Complete obstructions carry more risk of morbidity and can result in strangulation. As bowel contents are prevented from forward flow, increased secretions result in overdistention, which causes bowel wall edema and reduced lymphatic and venous outflow. This is referred to as strangulation and can progress to bowel ischemia, necrosis, perforation, and peritonitis. Up to 40% of small bowel obstructions become strangulated, most commonly from volvulus, adhesions, and hernias. A closed-loop obstruction occurs when there is mechanical blockage both proximal and distal to a bowel segment. This results in very high risk of strangulation because bowel contents are prevented from both forward and retrograde flow.
Small bowel obstructions represent 15% of hospital admissions for acute abdominal pain. Approximately 300,000 operations are performed every year in the United States for obstruction. Mortality rate overall is approximately 5%, whereas the mortality rate from strangulated obstructions approaches 30%.
In contrast to mechanical obstruction, functional obstruction (eg, adynamic ileus) occurs when intestinal contents fail to pass because of disturbances in gut motility. It most commonly occurs immediately after surgery, but can also be seen in inflammatory conditions, electrolyte abnormalities, and from certain medications (namely, narcotics). Unless noted otherwise, the remainder of this chapter refers to mechanical obstruction.
The most common initial complaint is intermittent colicky abdominal pain. If the obstruction is proximal, the patient may also complain of nausea and vomiting. More distal obstructions can result in delayed onset of vomiting. Although obstipation (lack of flatus and bowel movements) can suggest an obstruction, the presence of flatus or bowel movements should not be used as evidence that an obstruction has not occurred, as these can be seen early in the course of even complete obstructions. The patient history should include questions about prior surgeries, history of hernias, and history of obstruction in the past, as prior intestinal obstructions have up to 50% recurrence rate.