Page 583 - Textbook of Pathology, 6th Edition

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Figure 20.25 Crohn’s disease of the terminal ileum. A, The lesions
are characteristically segmental with intervening uninvolved ‘skip areas’.
The bowel wall is thickened and the lumen narrowed, giving hose-pipe
appearance. Serpiginous ulcers, some deep fissures and swollen
intervening surviving mucosa giving ‘cobblestone appearance’, are present.
B, The specimen of small intestine is shown in longitudinal section along
with a segment in cross section. External surface shows increased
mesenteric fat, thickened wall and narrow lumen. Luminal surface of
longitudinal cut section shows segment of thickened wall with narrow lumen
which is better appreciated in cross section (arrow) while intervening areas
of the bowel are uninvolved or skipped.

suspect but without definite evidence: Mycobacterium commonly 15-25 cm of the terminal ileum which may extend CHAPTER 20
paratuberculosis, Salmonella, Shigella, Helicobacter, Clostridia, into the caecum and sometimes into the ascending colon:
bacteroides, Escherichia, Measles virus etc.
ii) Psychosocial factors: It has been observed that individuals Grossly, characteristic feature is the multiple, well-
who are unduly sensitive, dependent on others and unable demarcated segmental bowel involvement with
to express themselves, or some major life events such as intervening uninvolved ‘skip areas’. The wall of the
illness or death in the family, divorce, interpersonal conflicts affected bowel segment is thick and hard, resembling a
etc, suffer from irritable colon or have exacerbation of ‘hose pipe’. Serosa may be studded with minute granu-
symptoms. Patients of IBD in the West have been found to lomas. The lumen of the affected segment is markedly
suffer from greater functional impairment than the general narrowed. The mucosa shows ‘serpiginous ulcers’, while
population, as assessed by sickness impact profile which is a intervening surviving mucosa is swollen giving The Gastrointestinal Tract
measure of overall psychological and physical functioning. ‘cobblestone appearance’. There may be deep fissuring
iii) Smoking: Role of smoking in causation of Crohn’s disease into the bowel wall (Fig. 20.25).
has been reported. Histologically, the characteristic features are as follows
iv) Oral contraceptives: An increased risk to develop Crohn’s (Fig. 20.26):
disease with long-term use of oral contraceptives has been 1. Transmural inflammatory cell infiltrate consisting of
found in some studies but there is no such increased risk for chronic inflammatory cells (lymphocytes, plasma cells and
ulcerative colitis. macrophages) is the classical microscopic feature.
Consensus hypothesis in pathogenesis of IBD combines 2. Non-caseating, sarcoid-like granulomas are present in all
the role of above three major groups of etiologic factors: i.e. the layers of the affected bowel wall in 60% of cases and
in a genetically predisposed individual, the effects of exogenous may even be seen in the regional lymph nodes.
and endogenous host factors result in dysregulation of 3. There is patchy ulceration of the mucosa which may take
mucosal immune function, which gets further modified by the form of deep fissures, accompanied by inflammatory
certain environmental factors. infiltrate of lymphocytes and plasma cells.
4. There is widening of the submucosa due to oedema and
MORPHOLOGIC FEATURES. The morphologic features foci of lymphoid aggregates.
of Crohn’s disease and ulcerative colitis are sufficiently 5. In more chronic cases, fibrosis becomes increasingly
distinctive so as to be classified separately. These features prominent in all the layers disrupting muscular layer.
are presented below; the distinguishing features of the
two conditions are summarised in Table 20.6. ULCERATIVE COLITIS. Classically, ulcerative colitis
begins in the rectum, and in continuity extends upwards into
CROHN’S DISEASE. Crohn’s disease may involve any the sigmoid colon, descending colon, transverse colon, and
portion of the gastrointestinal tract but affects most sometimes may involve the entire colon. The colonic contents