Colectasia, also called toxic megacolon, is an acute dilation of the colon caused by the presence of excess gas or fluid. Because it can lead to perforation of the intestinal wall, this is a medical emergency.

The colon, the longest part of the large intestine, can dilate with gas or intestinal fluids that cannot be evacuated, causing a feeling of bloating. This can happen during episodes of constipation. 

But if it swells to the point that its diameter exceeds 6 cm, the pain becomes sharp. Above all, the distended, thinned wall may perforate and release its contents (partially digested food, digestive juices, bacteria and feces) into the abdomen. Urgent care is therefore required immediately to prevent such a complication from occurring.

Toxic megacolon results from a bowel obstruction that prevents the contents of the intestine from being evacuated. Its causes can be:

• intestinal obstruction with obstacle : a tumor for example can obstruct intestinal transit. If this obstruction occurs in the colon, the contents of the intestine eventually accumulate there, causing it to dilate;
• chronic inflammatory bowel disease (IBD), such as ulcerative colitis (also called ulcerative colitis) or Crohn’s disease. Colectasia is a serious complication of these conditions. It can occur in patients who know they are already sick, but it can also appear during the inaugural crisis revealing the pathology. In IBD, colectasia is accompanied by other symptoms of acute colitis (bloody diarrhea and fever in particular);
• infectious colitis may also be complicated by severe acute colitis, with colectasia, bloody diarrhea and fever. It is often caused by the bacterium Clostridium difficile, which can proliferate during antibiotic therapy in fragile patients. People with Crohn’s disease are particularly at risk;
• ischemic colitis : a problem of vascularization of the intestine, linked to a clogging or to a thrombosis in a digestive artery, can cause a suffering of the tissues of the intestinal wall, even a necrosis of these tissues. This then leads to intestinal obstruction and toxic megacolon;
• certain neuromuscular conditions or certain drug treatments which affect the muscle tone of the intestine : neuroleptics or morphine for example induce gastrointestinal hypomobility. However, acute and persistent constipation is a factor favoring colectasia. 
• a postoperative ileus : Motor skills in the digestive tract may take a little time to recover after surgery or childbirth. If this postoperative ileus lasts longer than 72 hours, it must be managed to prevent colectasia.

If you have acute and persistent abdominal pain, or if you have sudden, severe abdominal pain, call 15. This is even more true if the pain is associated with distension of the abdomen, bloody diarrhea, fever and severe weight loss, typical signs of an outbreak of chronic inflammatory bowel disease.

If the medical regulator of the Samu directs you towards an emergency service, a medical imaging examination will be carried out upon your arrival, for diagnosis. This will be an abdomino-pelvic CT scan or an x-ray of the abdomen without preparation, that is, an x-ray without a contrast medium. A biological assessment will also be necessary to clarify this diagnosis. 

In case of colectasia, the risk of perforation of the colon wall is important. It will therefore be necessary to act as quickly as possible to prevent the contents of the intestine from spilling into the abdominal cavity and causing there an infection of the membrane surrounding the digestive organs (peritonitis), which is liable to spread into the blood and lead to an infection. general infection (septic shock, or sepsis). When this happens, the vital prognosis is strongly involved. Urgent treatment is needed.

Colectasia is a medical and surgical emergency. As soon as its cause and severity are established, rapid and appropriate management is required. 

If it is still possible to do so, drug treatment may be attempted, sometimes combined with exsufflation of intestinal gas by colonoscopy (colonic emptying). But these treatment options are only possible if they do not delay life-saving surgical treatment. In the absence of a rapid response, or if signs of colonic perforation are already visible, it will be necessary to operate. 

In many cases, especially with a complication of ulcerative colitis or Crohn’s disease, removal of all or part of the colon (colectomy) is necessary to save the patient. It is then associated with the installation of an appliance (ileostomy or colostomy, formerly called artificial anus). The rest of the treatment then depends on the cause of the toxic megacolon.