In which part of the colon is distension most prominent in toxic megacolon: cecum, ascending colon, transverse colon, descending colon, or sigmoid colon?

From the Guidelines

The transverse colon is the segment most prominently affected by distension in toxic megacolon. This occurs because the transverse colon has a larger diameter and thinner muscular wall compared to other colonic segments, making it more susceptible to severe dilatation during inflammatory conditions 1. In toxic megacolon, which is a life-threatening complication of inflammatory bowel disease (particularly ulcerative colitis) or infectious colitis, the transverse colon can dilate to more than 6 cm in diameter, as evidenced by radiographic findings 1. The key characteristics of toxic megacolon include:

• Radiographic evidence of total or segmental colonic distention of > 6 cm
• Presence of systemic toxicity
• Inflammatory (or infectious) etiology This condition requires urgent medical attention as it can lead to perforation, sepsis, and significant mortality if not promptly recognized and treated 1. Unlike colonic obstruction, where cecal dilation with perforation is a concern, the transverse colon is the area of greatest concern in toxic megacolon, with perforation associated with a high mortality rate (27–57%) 1.

The management of toxic megacolon involves coordination between medical and surgical services, with aggressive attempts at medical therapy, including steroids, fluids, and transfusions, and early surgical intervention in the absence of improvement, development of complications, or deterioration 1. Frequent reevaluations must be performed until the patient’s condition has clearly improved or until there is evidence of deterioration, in which case urgent surgery is indicated 1. Persistent fever after 48–72 h of steroid therapy should raise the possibility of local perforation or abscess, and indications for an urgent operation include free perforation, massive hemorrhage, increasing transfusion requirements, increasing signs of toxicity, and progression of colonic dilatation 1.

From the Research

Colonic Distension in Toxic Megacolon

• The most prominent colonic distension in toxic megacolon is typically observed in the cecum 2, 3, 4, 5, 6
• According to the study by 2, megacolon refers to cecal dilatation above the dimension of 12 cm
• The cecum is the portion of the colon that is most prone to dilatation in toxic megacolon, as it is the segment with the largest diameter 3, 4
• The other segments of the colon, including the ascending colon, transverse colon, descending colon, and sigmoid colon, may also be affected, but the cecum is the most commonly involved segment 5, 6

Diagnostic Criteria

• The diagnosis of toxic megacolon is typically made based on clinical evaluation and imaging studies, including plain abdominal radiographs 3, 5, 6
• The presence of systemic toxicity and severe colonic distension are the main characteristics of toxic megacolon 4, 5

Management

• The management of toxic megacolon requires an interdisciplinary approach, involving close interaction between gastroenterologists and surgeons 5, 6
• Medical therapy, including fluid and electrolyte replacement, corticosteroids, and broad-spectrum antibiotics, is often the initial treatment approach 3, 4, 5
• Surgical intervention may be necessary in cases where medical therapy fails or in the presence of complications such as perforation or peritonitis 2, 3, 4, 5, 6