History

Obstruction can be characterized as either partial or complete versus simple or strangulated. No single accurate clinical picture exists to detect early strangulation of obstruction, although signs of peritonitis, elevated lactate levels, leukocytosis, and the presence of free air and pneumatosis coli are known complications.

Abdominal pain associated with SBO is often described as crampy and intermittent. Without treatment, the abdominal pain can increase as a result of bowel perforation and ischemia; therefore, having a clinical suspicion for the condition is paramount to early identification and intervention. Furthermore, the clinical presentation of the patients varies and no one clinical symptom on its own identifies the majority of patients with SBO. Some studies have suggested that the absence of passage of flatus and/or feces and vomiting are the most common presenting symptoms, with abdominal discomfort/distention the most frequent physical examination findings.^[3]Other studies have shown that abdominal pain is present in the majority of patients found to have SBO.

Changes in the character of the pain may indicate the development of a more serious complication (ie, constant pain of a strangulated or ischemic bowel).

Patients presenting with SBO often report the following:

Previous abdominal or pelvic surgery, previous radiation therapy, or both
History of malignancy: Particularly ovarian and colonic malignancy
Inflammatory bowel disease
Nausea/vomiting (60-80%): The vomitus can often be bilious in nature
Constipation/absence of flatus (80-90%): Typically a later finding of SBO
Abdominal distention (60%)
Fever and tachycardia: Late findings; may be associated with strangulation

Physical Examination

Abdominal distention is present in about 60% of patients with small-bowel obstruction (SBO).^[3]The duodenal or proximal small bowel has less distention when obstructed than the distal bowel has when obstructed. Hyperactive bowel sounds occur early as gastrointestinal (GI) contents attempt to overcome the obstruction; hypoactive bowel sounds occur later in the disease process.

Physical examination can help exclude incarcerated umbilical, inguinal, femoral triangle, and obturator foramina hernias. Proper abdominal, genitourinary, and pelvic examinations are essential in identifying possible causes of incarceration as well as helping to exclude causes from the differential diagnosis. Look for the following features during rectal examination:

Gross or occult blood, which suggests late strangulation or malignancy
Masses, which suggest obturator hernia

Check for signs commonly believed to be more diagnostic of intestinal ischemia, including the following:

Fever (temperature >100°F)
Tachycardia (>100 beats/min)
Peritoneal signs (guarding, rigid abdomen, rebound tenderness, pain out of proportion to the examination)

No reliable physical examination method exists to differentiate simple from early strangulated obstruction. Serial abdominal examinations are important and may detect changes early.

Differential Diagnoses

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