What is the recommended diameter of the colon when it is diagnosed as toxic megacolon?

From the Guidelines

Toxic megacolon is defined as a colonic diameter of ≥ 5.5 cm, associated with systemic toxicity, as stated in the most recent and highest quality study 1. This severe complication is characterized by significant colonic distention along with systemic toxicity. The diagnosis requires both radiographic evidence of colonic dilation and signs of systemic illness such as fever, tachycardia, leukocytosis, or hypotension. Key features of toxic megacolon include:

• Colonic diameter of ≥ 5.5 cm on abdominal X-ray
• Systemic toxicity
• Risk factors such as hypokalaemia, hypomagnesaemia, bowel preparation, and the use of anti-diarrhoeal therapy Toxic megacolon most commonly occurs as a complication of inflammatory bowel disease (particularly ulcerative colitis), but can also develop in infectious colitis (like C. difficile infection), ischemic colitis, or obstruction. The importance of prompt recognition of toxic megacolon cannot be overstated, as it represents a medical emergency requiring immediate intervention to prevent perforation, which carries high mortality rates, as highlighted in 1 and further supported by 1.

From the Research

Definition of Toxic Megacolon

Toxic megacolon is defined as a dilatation of the colon in combination with signs of systemic toxicity. The recommended diameter for diagnosis varies across studies:

• A diameter of the colon > 6 cm is considered toxic megacolon in the absence of distal obstruction, as stated in 2.
• A cecal dilatation above 12 cm and a sigmoid colon dilatation above 6.5 cm are considered megacolon, as mentioned in 3.
• A colonic distension exceeding 60 mm is considered toxic megacolon, as stated in 4.

Key Characteristics

Key characteristics of toxic megacolon include:

• Toxemia
• Sepsis
• Distension of the colon due to diminished muscular tone, loss of motor activity, and increased amount of colonic gas, as mentioned in 4
• Systemic toxicity, including fever, tachycardia, leukocytosis, and anaemia, as stated in 2

Diagnostic Procedures

Diagnostic procedures for toxic megacolon include:

• Abdominal X-ray, as mentioned in 4 and 2
• Clinical examination
• Routine laboratory parameters
• Sigmoidoscopy, as mentioned in 5