To study the structural features of fetal rat duodenal mucosa associated with histogenesis of villi, duodena from 15-to 19-day fetuses were examined by light and electron microscopy. The duodenal epithelium of 15-to 18-day fetuses was stratified. Distinctive junctional complexes associated with membrane-bounded vesicles and cilia-like structures were seen i n the deeper epithelial layers at 15 and 16 days. Small lumina, designated "secondary lumina," lined with a variable number of microvilli developed between epithelial cells a t these junctional complexes during the sixteenth through eighteenth days. Degenerative changes and exfoliation of superficial epithelial cells were obvious in 17-and 18-day fetuses. In 18-day fetuses, aggregates of mesenchyme had invaginated the basal aspect of the stratified epithelium. Concomitantly, the number of epithelial layers overlying these mesenchymal projections was decreased. In 19-day fetuses, well formed, short duodenal villi lined by a simple columnar epithelium which included goblet and endocrine cells were evident. Injection of ferritin into the main duodenal lumen of 17-day fetuses failed to reveal continuity between the main lumen and the secondary lumina. However, continuity between many secondary lumina and the main lumen was demonstrated in 18-day fetuses. Thus, major morphological features associated with villus formation in fetal rat duodenum include : ( 1 ) formation of many secondary lumina in primitive stratified epithelium, ( 2 ) eventual fusion of these lumina with the main duodenal lumen, by their continued growth coupled with exfoliation of degenerating superficial layers and ( 3 ) upward growth of mesenchyme towards the lumen as cell exfoliation and expansion of secondary lumina take place.

Fifty patients with colonic tuberculosis are reported in whom a colonoscopic diagnosis confirmed by histological examination was possible in 40. Bacteriological studies did not increase the diagnostic yield. Abdominal pain was the most common symptom (90%) and an abdominal mass the most common abnormal physical finding (58%) Results Colonic tuberculosis was diagnosed in 50 patients during this 10 year study period. Sixteen had disease confined to the ileocaecal region, 14 had ileocaecal and contiguous involvement of variable lengths of the ascending colon, 13 had segmental colonic tuberculosis with involvement of the ascending colon in five, transverse colon in six, and descending colon in two. Five had ileocaecal and non-confluent involvement of another part of the colon, and in two the entire colon was affected.Abdominal pain occurred in 90%, weight loss in 74%, anorexia in 60% and fever and diarrhoea in 56% of all patients. None had pulmonary symptoms.A firm, usually tender abdominal mass of variable size (58%), and ascites (10%) were the only abnormal physical findings. The erythrocyte sedimentation rate was raised (>30 mm/h) in 38 of the 50 patients.Chest radiographs showed evidence of healed tuberculosis (fibrosis and/or calcification) in nine patients and active pulmonary tuberculosis (presence of acid fast bacilli in the sputum and/or gastric juice) in seven patients with ileocaecal disease and in both patients with pancolitis. COLONOSCOPYUlcerated areas a few millimetres up to 2 cm long, and a nodular friable mucosa were the most common lesions. These were often present in the same patient. The areas of ulceration were superficial and generally had sharply defined but irregular margins. The ulcer base was not friable and was covered with slough which was difficult to wash away. The surrounding mucosa was nodular and hyperaemic and blended imperceptibly with normal mucosa. In two patients numerous pale, polypoidal mucosal lesions of variable size arising from a slightly hyperemic mucosa were seen, and in one patient a solitary linear ulcer in the caecum was present. When the ileocaecal valve was involved it was oedematous and deformed and usually had areas of superficial ulceration. In the two patients with diffuse involvement of the colon, the mucosa from the rectum to the caecum was hyperaemic and friable 347 on 9 May 2018 by guest. Protected by copyright.

Background/aims-Impaired colonocyte metabolism of butyrate has been implicated in the aetiopathogenesis of ulcerative colitis. Colonocyte butyrate metabolism was investigated in experimental colitis in mice. (Gut 2000;46:493-499) Methods-Colitis was induced in

Conclusions-The type and frequency of granulomas, presence or absence of ulcers lined by epithelioid histiocytes and microgranulomas, and the distribution of chronic inflammation have been identified as histological parameters that can be used to diVerentiate tuberculosis and Crohn's disease in mucosal biopsy specimens obtained at colonoscopy. (Gut 1999;45:537-541)