Description 

A 24-year-old man with autism spectrum disorder presented to accident and emergency complaining of a 1-week history of abdominal pain and diarrhoea. He had a history of chronic constipation with multiple previous admissions stretching 4 years back. On examination, he had a tender, distended abdomen with quiet bowel sounds. His CT scan on admission (figure 1) showed a dilated (up to 18 cm) rectum and sigmoid colon filled with faeces. The patient was managed conservatively with oral laxatives and regular enemas. However, the patient refused the enemas and was maintained on oral laxatives. Two days later, the patient complained of worsening abdominal pain. On examination, he had a peritonitic abdomen and reduced consciousness level. Biochemical investigations revealed worsening renal function and that the patient was now acidotic. A chest X-ray revealed free air beneath the diaphragm. A repeat CT scan (figures 2 and 3) showed a substantial perforation of the dilated sigmoid colon. The patient was sent to intensive care unit before undergoing an emergency laparotomy where a Hartmann procedure was performed.

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Figure 1

Sagittal view of the sigmoid colon filled with faeces.

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Figure 2

Sagittal view of sigmoid colon post-perforation, with free air in the abdomen.

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Figure 3

Transverse view of sigmoid colon post-perforation, with free air and faeces in the abdomen.

Megacolon and/or megarectum are rare conditions defined as dilatation of the colon not caused by mechanical obstruction.1 It is classified by different values depending on the location of the dilatation in the colon. In the rectosigmoid region, a diameter greater than 6.5 cm is used.2 It can be divided up into acute, chronic or toxic megacolon. Chronic megacolon occurs when this dilatation is permanent secondary to a long-standing disorder of colonic motility. This condition can be congenital, acquired or idiopathic. Congenital megacolon may be caused by genetic abnormalities such as those associated with Hirschsprung’s disease or MEN2B.3 Acquired megacolon is associated with neuropathies, myopathies and connective tissue disease. Idiopathic megacolon are cases of megacolon where no organic cause is found. This patient had chronic, idiopathic megacolon and megarectum. Patients with this condition report recurrent episodes of constipation, abdominal pain, distension and bloating starting in childhood or adolescence. Due to increased intraluminal pressures, these patients are at an increased risk of ulceration of the bowel wall. Hence, they are at an increased risk of perforation. The literature on managing these patients is not consistent and, thus, these patients present a serious management challenge to surgeons.

For most patients with chronic megacolon and constipation, a non-surgical approach can be effective. This includes high colonic water enemas, water-soluble contrast enemas and oral polyethylene glycol-based solutions. If these methods succeed, patients can be discharged with dietary advice and a regular colonic regime. However, if these methods fail, it is important to consider early surgical therapy. This includes colectomy with ileoanal anastomosis in those with normal anorectal function and a diverting loop ileostomy in patients with abnormal anorectal function. This is associated with good outcomes in the majority of patients.2

In this case, an earlier appreciation during a previous admission that this was a rare presentation of chronic idiopathic megacolon and megarectum may have prevented the perforation and elective surgery could have been planned.