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A 50-year-old man complained of periumbilical and left lower quadrant abdominal pain that began earlier in the day. The pain was intermittent, “crampy” in character, and accompanied by anorexia and vomiting. He had a normal bowel movement the previous day. He had not experienced similar pain in the past. There was no history of prior abdominal surgery.

On examination, the patient was afebrile and in moderate distress due to his abdominal pain. Bowel sounds were present, and the abdomen was mildly distended with periumbilical tenderness, but no rebound tenderness.

Abdominal radiographs (Figure 1) and chest radiographs were obtained.

The abdominal radiographs were interpreted as showing a “nonspecific bowel gas pattern.”

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Although not immediately obvious, this patient’s radiographs have findings suggestive of mechanical small bowel obstruction (SBO). Detection of SBO is the primary role for abdominal radiography in patients presenting to the ED with abdominal pain. However, radiographs are diagnostic of obstruction in only 50% of cases; in 30% of cases, they are suggestive, but not diagnostic; and in 20%, they are negative (Mucha 1987). Interpretation of bowel gas patterns can be difficult, and there is considerable interobserver variability, even among radiologists (Suh et al. 1995, Markus et al. 1989).

Clinical Features of Small Bowel Obstruction

There is a wide range of clinicial presentations of mechanical SBO. The classical clinical presentation includes intermittent, crampy, periumbilical abdominal pain accompanied by vomiting, and nonpassage of feces or flatus. On examination, the patient’s abdomen is distended and tympanitic, and the bowel sounds are typically high-pitched and hyperactive. The abdomen may be mildly tender, but there should be no rigidity or rebound tenderness, unless the obstructed bowel is ischemic. Most patients have had prior abdominal surgery causing postoperative adhesions.

In patients with classical clinical presentations, the diagnosis is usually obvious on clinical examination. Radiographic studies serve mainly to confirm the clinical impression.

Many patients with SBO have atypical clinical presentations. Pain may be constant, mild, and even localized. Abdominal distention and vomiting may be minimal, and passage of feces and flatus may continue until bowel distal to the obstruction has evacuated its contents which can take 1–3 days or more. Muted clinical presentations are common in elderly and debilitated patients.

SBO should be considered as a cause of abdominal pain in all patients with prior abdominal surgery. However, obstruction can have etiologies other than postoperative adhesions (Table 1).

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