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
Abdominal radiographs (Figure 1) and chest radiographs were obtained.
A. Supine view. B. Upright view.
The abdominal radiographs were interpreted as showing a “nonspecific
bowel gas pattern.”
- Do you agree with this interpretation?
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).
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
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).