To critically review the literature addressing the definition, epidemiology, aetiology and pathophysiology of acute colonic pseudo-obstruction (ACPO).

A systematic search was performed to identify articles investigating the aetiology and pathophysiology of ACPO. A narrative synthesis of the evidence was undertaken.

No consistent approach to the definition or reporting of ACPO has been developed, which has led to overlapping investigation with other conditions. A vast array of risk factors has been identified, supporting a multifactorial aetiology. The pathophysiological mechanisms remain unclear, but are likely related to altered autonomic regulation of colonic motility, in the setting of other predisposing factors.

Future research should aim to establish a clear and consistent definition of ACPO, and elucidate the pathophysiological mechanisms leading to altered colonic function. An improved understanding of the aetiology of ACPO may facilitate the development of targeted strategies for its prevention and treatment.

The case of a patient with primary mesenteric venous thrombosis presenting with massive dilatation of almost the entire colon is described. The differential diagnosis suggested by this presentation is briefly discussed with special attention to the diagnosis of acute colonic pseudoobstruction. Possible reasons for the atypical presentation of acute mesenteric venous thrombosis should, therefore, be considered in the differential diagnosis of all patients presenting with colonic distention and pseudoobstruction.

Four additional cases of Ogilvie's syndrome (acute colonic pseudo-obstruction), representing the first cases described in Italy, are reported. The medical literature concerning the subject is also thoroughly reviewed. Ogilvie's syndrome is an acute massive dilatation of the large bowel without organic obstruction of the distal colon. Three hundred and fifty-one cases have been described in the literature to date. Eighty-eight per cent of the cases were associated with various extracolonic affections (metabolic and organ dysfunctions, postoperative and posttraumatic states, etc.). Twelve per cent of cases were not associated with known disorders and were defined as idiopathic. The pathophysiology of the syndrome is still unknown. Ogilvie, who first described the syndrome in 1948, suggested an imbalance between the sympathetic and parasympathetic innervation of the colon: this neurogenic hypothesis has been shared by other authors, although explanations may differ slightly. The clinical and radiologic picture closely resembles mechanical obstruction of the large bowel. The most marked dilatation usually takes place in the right colon and cecum: if the distended cecum reaches a diameter larger than 9 to 12 cm, perforation is likely to occur; if perforation occurs, the mortality rate increases from 25 to 31 per cent to about 43 to 46 per cent. If conservative management fails to control the dilatation and cecal rupture is impending or suspected emergency surgery is indicated, the surgical procedure of choice is dictated by the general conditions of the patient as well as by the intestinal findings: operation may consist of cecostomy, colostomy, or right hemicolectomy or simply emptying the bowel.

Two patients with intestinal obstruction in pregnancy are presented and discussed. In neither case was there any obvious cause for the intestianl obstruction. Pseudo-obstruction of the bowel has not previously been described as a complication of pregnancy.