Gastrointestinal tract
Oesophagus, stomach, small and large bowel, appendix and anus.
55 pages
Lesion
- Achalasia and other motor disorders: loss of the inhibitory neuronsThe valve at the lower oesophagus fails to open and the oesophagus stops squeezing, so food and…
- Acute appendicitisWhen the appendix gets blocked and its pressure rises, bacteria and lack of blood inflame it; if…
- Acute gastritis and stress ulcersPainkillers, alcohol, bile and severe illness can strip the stomach's protective layer, leading…
- AngiodysplasiaTangles of thin, widened blood vessels in the right colon can bleed slowly or heavily in older…
- Autoimmune atrophic gastritisThe immune system attacks the acid-making cells of the stomach body, so acid and intrinsic…
- Barrett oesophagusLong-standing reflux turns the lower oesophageal lining into a gut-like lining; this new lining…
- Chemical and infectious oesophagitisCaustic liquids, stuck tablets, radiation and germs can all inflame the oesophagus; each leaves…
- Coeliac diseaseIn genetically prone people, gluten from wheat, rye and barley triggers an immune attack that…
- Colonic adenomas and serrated lesionsAdenomas are benign gland tumours of the colon that can become cancer; the bigger and more…
- Colorectal adenocarcinomaColon cancer grows from polyps over years; right-sided ones bleed silently and cause anaemia…
- Congenital anomalies of the gutSome babies are born with a gut that is closed off, narrowed, joined to the airway, outside the…
- Crohn diseaseCrohn disease can inflame any part of the gut, in separate patches and through the whole wall…
- Diseases of the peritoneumThe lining of the abdomen can be inflamed by germs or leaking juices, scarred by fibrosis, or…
- Eosinophilic oesophagitis, and how it differs from refluxAn allergy-type inflammation fills the oesophagus with eosinophils, stiffens it and makes food…
- Gastric adenocarcinoma: intestinal vs diffuseStomach cancer comes in two forms: one forms bulky gland masses after long gastritis; the other…
- Gastric polypsMost stomach polyps are harmless overgrowths from gastritis or acid-lowering drugs; gastric…
- Gastrointestinal lymphomaThe stomach is the commonest place outside the lymph nodes for lymphoma; many arise from…
- Gastrointestinal neuroendocrine (carcinoid) tumoursTumours of the gut's hormone cells grow slowly as firm yellow nodules; some release substances…
- Gastrointestinal stromal tumour (GIST)The most common sarcoma-type tumour of the gut grows from the gut's pacemaker cells and is…
- Helicobacter pylori gastritisA spiral bacterium caught in childhood lives in the stomach mucus for life, inflaming it and…
- Hirschsprung diseaseNerve cells never reach the end of the colon, so that segment cannot relax; stool backs up and…
- Hypertrophic gastropathies: Ménétrier, Zollinger–EllisonIn these rare diseases the stomach folds become giant because growth signals make the lining…
- Intestinal helminthsWorms living in the gut can block it, bleed it, cause anaemia or itching, and some invade the…
- Intestinal obstructionThe bowel can be blocked by being trapped in a hernia, tied by scar bands, twisted on itself or…
- Intestinal protozoa: amoebic flask ulcers, Giardia and CryptosporidiumSingle-celled parasites from dirty water either burrow into the colon (amoeba) or cling to the…
- Invasive bacterial enterocolitisSome bacteria get inside the bowel lining, often through the immune sampling cells, inflaming it…
- Ischaemic bowel diseaseWhen blood flow to the bowel drops, the lining dies first; a sudden block of a major artery can…
- Meckel diverticulum, and true vs false diverticulaA small pouch left over from the yolk-sac duct sits on the ileum; it can bleed, block the bowel…
- Non-neoplastic colonic polypsMany colon polyps are not tumours: some are piled-up normal cells, some come from injury, and…
- Oesophageal adenocarcinoma: from Barrett to invasive cancerA gland-forming cancer of the lower oesophagus that grows out of Barrett mucosa, linked to…
- Oesophageal lacerations: Mallory–Weiss tear and Boerhaave ruptureViolent retching can split the lining near the stomach (and bleed) or, rarely, burst the whole…
- Oesophageal obstruction: stenosis, webs, rings, diverticulaScars, thin shelves of lining, rings and pouches can narrow the oesophagus and make food stick
- Oesophageal squamous cell carcinomaA cancer of the flat lining cells of the mid oesophagus, linked to tobacco, alcohol, hot drinks…
- Oesophageal varices: portosystemic collaterals and why they bleedWhen blood cannot pass easily through the liver, it detours through veins in the lower…
- Other colitis: microscopic, diversion, GVHD, drugSeveral kinds of colitis cause diarrhoea with a normal-looking colon; only the biopsy reveals…
- Other enteropathiesPoor sanitation, faulty immune control, missing enzymes and broken cell machinery can all stop…
- Peptic ulcerA peptic ulcer is a deep crater in the stomach or duodenum, usually from H
- Pseudomembranous colitis: C. difficile toxins and the volcano lesionAfter antibiotics disturb the normal gut bacteria, C
- Pyloric stenosis: infantile hypertrophic and acquiredIn some infants the muscle of the stomach outlet grows too thick and blocks it; in adults…
- Reflux oesophagitis: what acid does to the squamous liningWhen stomach acid repeatedly flows back up, the lining of the lower oesophagus thickens, gets…
- Sigmoid diverticular diseaseHigh pressure inside the colon pushes its lining out through weak spots in the muscle, forming…
- The anal canal: haemorrhoids, condyloma and anal carcinomaSwollen anal veins cause bright red bleeding; HPV can cause warts and, with high-risk types…
- Tumours of the appendixThe commonest appendix tumour is a small harmless neuroendocrine nodule at its tip; mucus-making…
- Typhoid fever: Peyer patch ulcers and typhoid nodulesA Salmonella that only infects humans enters through the small bowel, spreads through the body…
- Ulcerative colitis vs Crohn diseaseUlcerative colitis inflames only the inner lining of the colon, always starting at the rectum…
- Uncommon gastritis: eosinophilic, lymphocytic and granulomatousSome gastritis is caused by allergy, by lymphocytes linked to coeliac disease, or by granulomas…
- Viral gastroenteritis: norovirus, rotavirus, adenovirus and SARS-CoV-2Viruses kill the absorbing cells at the tips of the villi, causing short bouts of vomiting and…
- Whipple disease: foamy PAS-positive macrophages in the villiA rare bacterial infection fills the small-bowel lining with swollen macrophages that block fat…
Process
- Colitis-associated neoplasia: dysplasia in long-standing IBDYears of colitis raise the risk of colon cancer, which often starts in flat abnormal lining that…
- Gastric atrophy, intestinal metaplasia and dysplasiaYears of gastritis can thin the stomach lining, turn it gut-like and then produce abnormal cells…
Topic
- Hereditary colorectal cancer: FAP and Lynch syndromeTwo inherited conditions explain much about colon cancer: one fills the colon with hundreds of…
- Infectious enterocolitisGerms cause diarrhoea either by making toxins that pump water out, or by invading and inflaming…
- Malabsorption and diarrhoeaDiarrhoea can come from water being pulled in, pumped out, food not being absorbed, or an…
Mechanism
- Inflammatory bowel disease: pathogenesisCrohn disease and ulcerative colitis arise when a gut with a weak barrier and inherited risk…
- Toxin-mediated diarrhoea: cholera and E. coliCholera toxin switches intestinal cells into constant salt-and-water pumps; different E
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Representative model, for educational purposes only.