左侧为正常小肠黏膜，右侧为脂肪痢黏膜。脂痢病肠绒毛变扁平，严重病例黏膜扁平、绒毛缺失，如右图所示。脂肪痢在白种人中的发病率为1：2000，但很少发生在别的种族。大于95%的感染人群有组织相溶性抗原DQw2的表达，提示有遗传基础。

Normal small intestinal mucosa is seen at the left, and mucosa involved by celiac sprue at the right. There is blunting and flattening of villi with celiac disease, and in severe cases a loss of villi with flattening of the mucosa as seen here. Celiac sprue has a prevalence of about 1:2000 Caucasians, but is rarely seen in other races. Over 95% of affected patients will express the DQw2 histocompatibility antigen, which suggests a genetic basis.

在高倍镜下，小肠黏膜显示脂肪痢有有明显的慢性炎症。并对麸质过敏，因麸质中含有麦胶蛋白，此蛋白在小麦谷物中，燕麦、大麦和黑麦中存在。从饮食中去除包含这些谷物的食品，将使得麦质过敏性肠病减少。这里显示这种肠病缺乏腺管、有丝分裂活跃、刷状缘消失，伴有淋巴细胞和浆细胞浸润（B细胞对麦胶敏感）。

The small intestinal mucosa at high magnification shows marked chronic inflammation in celiac sprue. There is sensitivity to gluten, which contains the protein gliaden, found in cereal grains wheat, oats, barley, and rye. Removing foods containing these grains from the diet will cause this gluten-sensitive enteropathy to subside. The enteropathy shown here has loss of crypts, increased mitotic activity, loss of brush border, and infiltration with lymphocytes and plasma cells (B-cells sensitized to gliaden).

由贾第虫感染小肠引起感染性腹泻的例子。小的梨形滋养体在十二指肠内，变成有感染性的包囊后释放出来。它会产生水样腹泻。感染性腹泻诊断的检查是大便检查寻找卵和寄生虫。

This is an example of infectious diarrhea due to Giardia lamblia infection of the small intestine. The small pear-shaped trophozoites live in the duodenum and become infective cysts that are excreted. They produce a watery diarrhea. A useful test for diagnosis of infectious diarrheas is stool examination for ova and parasites.

另一感染性因素，更常发生于免疫缺陷病人，特别是有获得性免疫缺陷综合症（艾滋病）的病人。在内腔边界的小圆兰色的生物体是隐孢子虫。隐孢子虫病会引起大量的水样便。

This is another infectious agent that is becoming more frequent in immunocompromised patients, particularly those with AIDS. The small round blue organisms at the lumenal border are cryptosporidia. Cryptosporidiosis produces a copious watery diarrhea.

在左边是正常的结肠的结肠镜检图。

normal appearances of the colon with colonoscopy.

盲肠镜检图。

Cecum

升结肠镜检。

Ascending colon

横结肠镜检。

Transverse colon

结肠脾曲镜检。

Splenic flexure

乙状结肠镜检。

Sigmoid colon