Ulcerative Colitis and Crohn's Disease

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Introduction

I have grouped these two inflammatory bowel diseases together in recognition of the possible similarities in their appearances on abdominal plain film. They are not the same disease process.

Crohn's Disease

Pathology

Crohn's disease is an inflammatory disease of the gastrointestinal tract. The causative agent has not been positively identified

Plain Film Appearances

Crohn's disease (also known as granulomatous colitis when confined to the colon) may be indistinguishable from ulcerative colitis when confined to the colon. The plain film signs of Crohn's disease are as follows:

Abdominal Plain Film Signs	Comment
long gas-filled stricture	can also be seen in other diseases including ulcerative colitis
narrowed small bowel lumen	not seen in ulcerative colitis
small bowel obstruction	indication of marked stenosis causing obstruction
terminal ileum disease	common site for inflammation of bowel in Crohn's disease
skip lesions	Crohn's lesions can be isolated lesions that occur anywhere in the GIT. Multiple isolated areas of inflammation are referred to as skip lesions
bowel wall thickening	sometimes seen in small bowel on plain film
fistula	inflammation affects whole wall thickness nd can lead to breakdown of wall and fistula formation
associated with spinal arthropathy	associated with sacroiliitis and ankylising spondylitis
cobblestone appearance, particularly of terminal ileum	seen on bariun follow-through examination
intra-mural gas	fulminant Crohn's disease can proceed to toxic megacolon with intra-mural gas

Patient's with fulminant Crohn's disease may be subject to daily abdominal radiographs where there is a possibility of toxic megacolon.

Case 1

	The transverse colon is dilated and shows evidence of thumbprinting (black arrow) The descending colon has a thickened featureless wall and pockets of intra-mural gas (white arrow). Bowel wall does not normally exceed 2mm in thickness but may be up to 10mm in thickness with severe inflammatory bowel disease. Patient has known Crohn's disease Long narrowed segment of descending colon Appearances consistent with toxic megacolon

Case 2

	This patient has known Crohn's disease and has had a previous ileo-colic anastamosis. There is evidence of dilation of the small bowel with thickened wall (white arrows) narrowed area of descending colon is probably normal (black arrow)
	Small bowel follow-through on same patient. The small bowel is dilated (black arrow). The anatomy is abnormal because of a previous ileo-colic anastamosis. Note the reduced length of small bowel. There is at least one colonic fistula (white arrow)

Ulcerative Colitis

Pathology

Plain Film Appearances

psedopolyps (acute fulminant stage)	lumpy impressions in bowel gas, islands of lumpy mucosa
absence of faeces	acute and chronic stages of disease
featureless, ribbon-like, lead pipe colon	active and quiescent stages
fine mucosal granular pattern on barium enema	may be faintly visible on plain film
thumbprinting (active stage)	caused by mucoal oedema
loss of haustration of left colon	non-active stage
shortening of colon	? caused by fibrosis, longitudital muscle spasm

Case 1

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