Amr Gharib1 and Christopher R. Carpenter2 1 Department of Emergency Medicine, University of Pittsburgh Medical Center, Harrisburg, PA, USA 2 Department of Emergency Medicine, Washington University School of Medicine, St. Louis, MO, USA Mechanical small bowel obstruction (SBO) is a surgical disorder of the small intestine responsible for 2% of emergency department (ED) visits for abdominal pain and represents 15% of all surgery admissions from the ED.1,2 Approximately 75% of SBO cases result from intra‐abdominal adhesions.3 Bowel strangulation, which occurs when bowel wall edema compromises perfusion to the intestine and necrosis ensues, is the most severe complication of SBO and occurs in up to 10%.4 The rate of nonviable bowel with strangulation increases with patient age and treatment delays.5 If untreated, strangulated bowel may perforate, leading to peritonitis with a high rate of mortality. Over 300,000 patients undergo surgery every year in the United States for adhesion‐induced SBO; however, SBOs also occur for other reasons including hernias, malignancies, volvulus, inflammatory conditions, foreign bodies, gallstones, pancreatitis, and intussusceptions.3 SBO typically presents as abdominal pain, distension, vomiting, and sometimes constipation.6 What elements of the history and physical examination are best predictors of SBO? A diagnostic meta‐analysis in 2013 quantified the accuracy of history and physical examination for the diagnosis of SBO based on two publications meeting their inclusion criteria.6–8 The criterion standard for SBO included surgical findings, X‐ray, or diagnosis at the time of discharge. The meta‐analysis identified the most accurate predictors of SBO to be history of abdominal surgery (+LR range = 2.7–3.9 and −LR range = 0.19–0.42) and a history of constipation (+LR range = 3.7–8.8 and −LR range = 0.59–0.70). The most accurate physical exam findings were abdominal distension (+LR range = 5.6–16.8 and −LR range = 0.34–0.43) and abnormal bowel sounds (+LR = 6.33 and −LR = 0.27).6 Table 38.1 summarizes the accuracy of history and Table 38.2 summarizes the accuracy of physical exam. Table 38.1 Diagnostic accuracy of history for SBO Source: Data from [6]. Table 38.2 Diagnostic accuracy of physical exam for SBO Source: Data from [6]. Which diagnostic imaging modality is most sensitive in diagnosing SBO?
Chapter 38
Small Bowel Obstruction
Background
Clinical question
Finding
+LR
−LR
Age > 50
2.2
0.55
Constipation
3.7–8.8
0.59–0.70
Intermittent pain
1.6–2.8
0.35–0.85
Intolerable pain
1.2
0.57
Nausea
1.4
0.35
No appetite
1.3
0.25
No aggravating factor
1.4
0.85
Pain duration > 6 hours
1.4
0.79
Pain increased with eating
2.8
0.88
Pain worsening
1.2
0.65
Previous abdominal surgery
2.6–3.9
0.19–0.42
Previous similar pain
1.2
0.91
Relieved with vomiting
2.7–4.5
0.78–0.87
Vomiting
2.1
0.38
Finding
+LR
−LR
Abnormal bowel sounds
6.3
0.27
Abdominal mass
2.1
0.89
Abdominal scar
3.7
0.19
Abnormal abdominal movement
3.0–3.7
0.80–0.87
Decreased bowel sounds
3.3
0.83
Distention
5.6–16.8
0.34–0.43
Increased bowel sounds
3.6
0.67
No rebound
1.1
0.85
Rigidity
3.0
0.89
Temperature < 37.1 °C
1.4
0.45
Tenderness (generalized)
2.6–5.0
0.42–0.70
Visible peristalsis
∞
0.94
Clinical question
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