Imaging Case of the Week 94

This supine abdominal x-ray is from a 68 year old patient who has presented with central abdominal pain and vomiting. There appears to be evidence of small bowel obstruction on the x-ray. Can you determine the cause? (It is very subtle).

supine abdominal x-ray

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[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

The supine x-ray shows dilated small bowel loops in the central abdomen; these are jejunal loops with the typical ‘stack of coins’ appearance. There is air lucency projected over the left obturator foramen, which is suspicious for a bowel loop. There is also non-specific dilatation of the transverse and sigmoid colon.

Obturator hernia x-ray

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A CT scan confirmed the presence of left sided obturator hernia with a loop of the small bowel. Thus, this patient has small bowel obstruction secondary to obturator hernia.

The abnormal presence of the bowel loop below the inguinal ligament should be carefully inspected for in a patient presenting with bowel obstruction.

Obturator hernia:

  • A rare cause of intestinal obstruction; has high mortality. Very difficult to diagnose clinically.
  • Accounts for 0.2-1.6% of all causes of mechanical bowel obstruction.
  • Advanced age and malnutrition are strong risk factors (loss of fat layer covering the obturator foramen).
  • Conditions causing raised abdominal pressure (such as chronic constipation, ascites, and chronic airway disease) are predisposing factors.
  • Compression of the obturator nerve by the hernia sac produces the Howship-Romberg sign: pain along the medial aspect of the thigh to the knee. This pain can be relieved by hip flexion and is exacerbated by hip abduction, extension and medial rotation.
  • A palpable inguinal mass on the upper medial thigh is a rare finding. A rectal or pelvic examination will reveal a tender mass in the region of the obturator foramen.
  • CT scan is the investigation modality of choice.