23.1 : 慢性肠道疾病：简介

Chronic bowel disorders are long-term medical conditions affecting the digestive tract, including disorders such as irritable bowel syndrome or IBS and inflammatory bowel disease or IBD.

IBS entails chronic abdominal pain and altered bowel habits.

It manifests either as constipation-predominant IBS-C with reduced bowel movement frequency or as diarrhea-predominant IBS-D characterized by recurrent abdominal discomfort and frequent loose stools.

IBD involves recurrent chronic intestinal inflammation due to immune attacks by an over-responsive immune system on gut-resident bacteria.

This triggers diarrhea, abdominal pain, and intestinal bleeding. The primary IBD subtypes are ulcerative colitis and Crohn's disease.

Ulcerative colitis predominantly affects the rectum and colon with continuous inflammation of the rectal mucosal layer.

In contrast, Crohn's disease affects the entire digestive tract, with the terminal ileum being the most commonly affected. It causes discontinuous transmural inflammation throughout the GI tract, leading to fibrosis, strictures, or fistula.