Symptoms and Diagnosis of Small Bowel Obstruction

Small bowel obstructions can be complete, in which there is no passage of intestinal contents beyond the blockage, or partial, in which an inadequately small amount of intestinal contents and gases are able to pass beyond the obstruction.

Symptoms of small bowel obstruction can include:
-Obstipation (no bowel movements or passage of gas)
-Nausea and vomiting (more severe in proximal obstruction vs. distal)
-Abdominal pain, usually periumbilical, paroxysmal and crampy
-Abdominal distension (more severe in distal obstruction vs proximal)

Small bowel obstructions are serious medical problems that require prompt medical or surgical management. If left untreated, the small intestine dilates and the blood flow becomes compromised. Without adequate blood flow the intestine can begin to necrose (undergo tissue death). Additionally, the bowel may strangulate entirely and or cause sepsis. Strangulated intestine occurs more often in complete SBO's that are the result of a closed-loop obstruction. A closed-loop obstruction occurs when a short segment of intestine is blocked on both ends.

The diagnosis of small bowel obstruction starts with the physical exam. Surgical scars (adhesions), abdominal masses (abscess, volvulus, tumor), hernias (inguinal, femoral, incisional), a mass in the rectal vault and/or gross or occult blood on digital rectal exam (cancer, ischemia, intussusception) can suggest the cause of the obstruction. The abdomen is often tympanic on percussion.

Labs are less helpful in diagnosing a small bowel obstruction, but are important in determining dehydration and electrolyte status. Patients who have been vomiting frequently will often have a hypokalemic hypochloremic metabolic alkalosis. On the other hand, patients with ischemic bowel may have a metabolic acidosis, an elevated white count, and an elevated lactate if checked.

A plain abdominal x-ray can confirm the diagnosis of small bowel obstruction when clinically suspected. An upright abdominal x-ray will show dilated loops of bowel with air-fluid levels. A left lateral decubitus x-ray can be used to show air fluid levels if the patient cannot sit up. In addition, an upright chest x-ray can be used to rule out the presence of free air.

A CT is the most useful form of imaging when detecting a closed-loop obstruction or ischemic bowel. CT is also useful in small bowel obstructions when the diagnosis is unsure and the plain (x-ray) films are unhelpful. A small bowel obstruction is suggested on CT when there is a transition point causing a large difference in the size or caliber of the proximal and distal aspects of the small bowel. The small bowel obstruction is considered a complete, rather than partial, obstruction when there is no air or fluid noted in the small bowel or colon distal to the transition point.

Small bowel obstructions are potentially dangerous medical conditions. Individuals with the symptoms discussed above should seek medical care.