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Q1: What does the plain abdominal radiograph (fig 1; see p 432) show? What was the subsequent investigation (fig 2; see p 432) and what does this show?
Pneumoperitoneum and small bowel fluid levels are shown. The subsequent investigation is a small bowel barium meal, and this shows jejunal diverticulosis. The presence of small bowel fluid levels on the plain abdominal radiograph suggests that jejunal diverticulosis is the most likely underlying cause.
Q2: How would you manage this patient?
Exploratory laparotomy is mandatory if the patient presents with clinical stigmata of peritonitis. However, spontaneous pneumoperitoneum can occur without peritonitis or perforation of a viscus. Jejunal diverticulosis and pneumatosis cystoides intestinalis are the most common gastrointestinal causes of this condition. Where a non-surgical cause of pneumoperitoneum can be discerned and there are no associated findings to suggest peritonitis or a perforated viscus, then continued observation should avoid an unnecessary laparotomy. This was the case in our patient whose distention improved with conservative management. In instances where aetiology of the pneumoperitoneum remains unclear, a diagnostic peritoneal lavage may obviate the need for laparotomy.
Q3: What mechanism results in the development of the radiological abnormality shown in fig 1 (see p 432)
The mechanism of pneumoperitoneum in jejunal diverticulosis is relatively unclear. It is thought to result from the passage of intraluminal gas, without gross faecal contamination, into the peritoneal cavity through perforations in the wall of the thin walled diverticula. Hyperactive peristaltic activity and fermentation in the diverticula may also contribute. Our patient subsequently developed diarrhoea and underwent a hydrogen breath test, which was markedly abnormal, indicating bacterial overgrowth in the small bowel.
Diverticulosis of small intestine is a relatively unusual finding and the cause of significant symptoms in less than 50% of patients in whom diverticula are found.1 The most frequent symptoms are a result of low grade intestinal obstruction. These consist of upper abdominal discomfort, and fullness and vomiting after meals. Other presentations include acute obstruction, inflammation, bleeding, perforation, inspissation with enterolith formation, and macrocytic anaemia. Spontaneous pneumoperitoneum unassociated with signs or symptoms of peritoneal irritation is an uncommon presentation of small intestinal diverticulosis. Since the vast majority of these patients are asymptomatic and remain so, conservative management is indicated.
Recognition of this entity is important if unnecessary surgery for a suspected perforation of the gastrointestinal tract is to be avoided.2
Pneumoperitoneum is usually the result of hollow viscus perforation with associated peritonitis.3 Common causes are perforated duodenal or gastric ulcers, perforation of colon diverticula or appendix, and perforated ulcerative colitis or amoebic colitis.4 Spontaneous pneumoperitoneum consequent upon intrathoracic, intra-abdominal, gynaecological, iatrogenic, and other miscellaneous conditions not associated with perforated viscus have been documented in the literature. In some instances no cause for pneumoperitoneum is evident.
Spontaneous pneumoperitoneum secondary to jejunal diverticulosis.