"ULCERATIVE COLITIS (UC)"

This is three-times more common than Crohn disease . The peak is between 15 and 25 years of age. After 10 years of UC, there is an increased...

This is three-times more common than Crohn disease. The peak is between 15 and 25 years of age. After 10 years of UC, there is an increased risk of malignancy (though most UC strictures are still benign). 

The hallmark of fulminant colitis is toxic megacolon (it can also occur in Crohn disease, ischaemic or infective colitis). 

Toxic megacolon arises due to deep ulceration causing bowel denervation and hence massive dilatation.

BARIUM ENEMA

•  Tends to affect the rectum first and extend proximally.
•  May cause a pancolitis.
•  Granular pattern.
•  Shallow ulceration—deeper ulceration may cause the ‘collar button’ appearance as the submucosa is eroded.
•  Reflux ileitis—typical of UC and resolves after colectomy.
•  Severe ulceration causes multiple ‘mucosal islands’.

PLAIN FILM

•  Ahaustral, thickened and dilated large bowel (tendency to affect the transverse colon) suggests toxic megacolon (dilatation >5.5 cm is worrying).
•  Toxic megacolon commonly perforates.

CT

•  Non-specific bowel wall thickening and fat stranding.
•  Look for lymph node enlargement in acute cases.
•  In chronic UC, there is submucosal fat proliferation.
•  Note: In the acute phase, the diagnosis may be masked; if it is not clear whether it is Crohn disease or UC, then the diagnosis is most likely Crohn disease 

 

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