inflammatory bowel diseases show primary inflammation of the intestinal wall
The idiopathic inflammatory
bowel diseases, of which there are two main members, have no known cause.
In Crohn's disease there
is a granulomatous inflammatory pattern of disease that affects the full
thickness of the bowel wall.
It is most common in the
terminal ileum, but may affect any part of the gastrointestinal tract in a
With ulcerative colitis, a chronic
inflammatory disease of the rectal mucosa, inflammation may extend to involve
the whole of the colon in continuity.
types of inflammatory bowel disease are associated with systemic manifestations
outside of the intestine.
In diagnosing idiopathic
inflammatory bowel disease, infective causes of inflammation have first to be
is by imaging and biopsy.
is more common in women than in men, patients
usually being 20-60 years old.
It particularly affects the terminal ileum (synonym: regional ileitis), but can
occur anywhere in the gut, especially in the mouth, colon, and anus.
The macroscopic appearance
of the bowel in Crohn's disease varies according to the stage of the disease.
in early disease affected
bowel shows marked swelling of submucosa and mucosa, mainly due to
severe submucosal oedema.
This leads to loss of the pattern of normal transverse
folds, and small superficial areas of haemorrhagic ulceration arise which,
over time, develop into fissures.
In established chronic
disease the bowel mucosa shows a cobblestone pattern due to a combination of
submucosal oedema and
interconnecting deep fissured ulcers.
The bowel wall is thickened by oedema and fibrosis and, commonly, there is
stricture formation. Regional lymph
nodes usually become enlarged.
Disease is not continuous and areas of normal
bowel may be present between the diseased segments (skip lesions).The normal
bowel proximal to a segment of Crohn's disease is often dilated due to partial
Direct complications of
Crohn's disease shows
transmural inflammation with deep fissured ulcers Crohn's disease is
characterized by inflammation of all layers, submucosal oedema, ulcers that
extend deepinto the bowel wall and form fissures, and
Non-caseating granulomas may be present.
Inflammation in Crohn's
disease is transmural, and serosal involvement leads to inflammatory adhesion to
other loops of bowel, to the parietal peritoneum of the anterior abdominal wall,
or to the bladder.
Deep penetration of fissured ulcers, which may extend through
the full thickness of the bowel wall into the adherent viscus, causes fistulae
(tracks between two cavities) and sinuses
(a track from a viscus to an outside surface).
This is particularly seen in the perianal region.
The inflammation in the wall
is composed of lymphoid cells, macrophages and plasma cells.
Small non-caseating granulomas, which occur in about 70% of cases, may be seen
in any layer of the bowel, e.g. mucosa.
Ulcerative colitis affects the rectum and
variable amounts of colon
Ulcerative colitis starts at
the rectum (proctitis) and may extend for a variable distance around the colon.
There are three clinical
patterns of disease:
1 In active acute disease
the mucosa in the rectum and affected colon shows areas of shallow ulceration;
inflammation is limited to the mucosa and lamina propria.
2 In chronic quiescen or
treated disease ulceration is not prominent and the mucosa appears red, granular
3 In fulminant active
disease the colon shows extensive confluent mucosal ulceration.The colon
progressively dilates (toxic dilatation - 'acute toxic megacolon').
The direct local
complications of ulcerative colitis include blood and fluid loss from extensive
ulceration. Acute disease may progress
rapidly to toxic dilatation and perforation and, in long-standing disease,
dysplasia and neoplastic change may occur.
In the most
extensive disease the whole colonic mucosa is affected.
develop diarrhoea, the faeces being mixed with blood, mucus and pus. The natural
history of ulcerative colitis can be divided into three main patterns:
• 10% of patients develop
severe disease requiring early surgery.
• 10% of patients have
persistent active disease despite treatment.
• 80% of patients have
chronic quiescent colitis with infrequent episodes of relapse.