Prognosis

Look for ^c  

• abdominal distension 
• localised or generalised peritonitis 
• fever ≥38°C 
• tachycardia > 120 beats/minute 
• leucocytosis > 11x 10⁹/l 
• small bowel distension on plain abdominal X-ray ^c  

Why?

• 10% of patients with acute ulcerative colitis develop toxic dilatation (95% CI: 7.6% to 12%), compared with 2% of patients with acute Crohn's disease ^c
• 16% die (95% CI: 7.7% to 24%) ^c

Small bowel distension increases the risk of toxic megacolon

Outcome c	Risk Factor	PEER	OR (95% CI)	NNH (95% CI)
toxic megacolon	increased small-bowel gas on supine plain abdominal film (> 74 cm²) not independent	39%	2.58 (1.89 to 3.53)	2 (1 to 3)