Path 48: GI - Small Intestine and Large Intestine (Non-Neoplastic)
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29 terms
Terms | Definitions |
|---|---|
 Meckel's Diverticulum | incomplete involution of vitelline duct -> rule of 2s -> 2% of normal population, within 2 feet of Ileocecal valve, average length is 2 inches -> on anti-mesenteric border, all layers of GIT (true diverticulum) -> sometimes lined by gastric mucosa or pancreatic tissue |
| Meckel's clinical | commonly asymptomatic, complications: hemorrhage and peptic ulceration, intestinal obstruction, diverticulitis, perforation, fistula |
| Malabsorption syndrome | defective absorption of fats, fat soluble and other vitamins, proteins, carbohydrates, electrolytes, minerals and water -> clinically present with chronic diarrhea -> typically fatty feces (steatorrhea) -> impaired digestion, absorption, delivery |
| Celiac disease (gluten sensitive enteropathy) | common in whites 1-10 years (typically genetically sensitive to gluten), changes more marked in proximal part of intestine (marked atrophy and loss of villi -> reduced area for absorption, increased intraepithelial lymphocytes, elongated and hyperplastic crypts, increased number of lymphocytes, plasma cells in lamina propria) -> reversal of changes after gluten free diet |
| Pathogenesis of celiac disease | HLA-B8, HLA-DR3-DQw2 mutations -> adenovirus and gluten -> causes immunologic response -> patients almost always express MHC class II antigens HLA-DQ2, HLA-DQ8 |
| Diagnosis of celiac disease | documentation of malabsorption (iron deficiency anemia), small intestine biopsy, reversal of changes after gluten free diet, serologic tests (anti-gliadin and anti-endomysial antibodies, anti-tissue transglutaminase tTG antibodies -> best test but may be false negative without serum IgA levels), long term risk of intestinal lymphomas (T cell type) |
| Tropical sprue (post infectious sprue) | in people living or visiting tropics (pay attention to history) -> symptoms appear months or years later -> pathogenesis is related to bacterial infection superimposed on pre-existing small intestine injury -> all parts of SI are involved equally -> difficult to differentiate from celiac disease -> responds to antibiotics |
| Whipple's Disease | Systemic disease involving mainly intestine, joints and CNS -> caused by gram positive sickle shaped actinomycetes- Trepophyrema whippelii -> more common in males (10:1), mucosa laden with distended macrophages (villi loaded with foamy macrophages) in lamina propria contain PAS positive granules -> rod shaped bacilli can be seen on EM -> treat with antibiotics |
| Hirschsprung's Disease (Congenital megacolon) | most common cause of congenital intestinal obstruction -> males more common (4:1), in 10% of Down syndrome patients -> absence of ganglion cells in Meissner's and Auerbach's plexus (defect in migration and survival of neuroblasts) -> rectum is always affected -> dilation and hypertrophy proximal to aganglionic segment -> delayed meconium, constipation, abdominal distension, diagnosed by rectal biopsy (rat tail pattern on barium X ray); complications: enterocolitis, perforation and peritonitis |
| Diverticular disease (diverticulosis and diverticulitis -> not true diverticuli) | common in western world, 50% in older than 60 years -> flask like structures (95% sigmoid colon) extending from lumen through muscular layer -> lack of dietary fiber leads to sustained bowel contractions and increased intraluminal pressure -> herniation of colonic wall at sites of focal defects |
| Diverticulosis | usually asymptomatic but sometimes painless bleeding |
| Diverticulitis | lower abdominal pain, constipation, diarrhea, flatulence, fever -> can lead to perforation |
| Colitis | caused by infections (bacterial, viral, protozoal - amebic), necrotizing enterocolitis, antibiotic associated (pseudomembranous), ischemic, idiopathic inflammatory bowel disease (IBS) -> causes diarrhea (mucoid/bloody), abdominal pain (usually below umbilicus), abdominal cramps, tenesmus (painful defecation) |
| Pseudomembranous colitis (C. difficile) | associated with broad spectrum antibiotic use -> toxin mediated damage -> rectosigmoid colon exhibits raised yellow plaques -> fibrinopurulent necrotic debris (pseudomembranes -> surface epithelium denuded, superficially damaged crypts distended by mucopurulent exudate which erupts to form a mushrooming cloud -> coalescence of these clouds leads to pseudomembrane formation) |
| Amebic colitis (entamoeba histolytica) | fecal oral route, may resemble IBD, gradual dysentery caused by parasite, chronic destructive colitis with flask shaped ulcers with organisms engulfing red cells -> treat with anti-parasitics |
| Ulcerative lesions of the intestines | IBS (includes Crohn and ulcerative colitis), peptic ulcers (duodenal), infectious etiology (bacterial - salmonella, TB, CMV in immunosuppressed), ischemic colitis, drugs (NSAIDs - stricture formation is common), tumors |
| Ulcerative colitis | intermittent rectal bleeding, bloody diarrhea and abdominal pain -> typically continuous colonic involvement |
| Crohn disease | more variable symptoms than UC that include abdominal pain, fatigue, weight loss and fever -> typically patchy transmural involvement |
| TB | Langhan's type giant cells, chronic abdominal pain, multifocal involvement (jejunum to ileum, TI most common) -> anular circular or oval ulcers, lying transversely -> single ulcers are large, multiple ulcers smaller -> granulomatous inflammation, often necrotizing |
| Typhoid | fever, headache, abdominal pain, rash, diarrhea -> longitudinal ulcers, typically over Peyer patches |
| Idiopathic inflammatory bowel disease | includes Crohn's disease and ulcerative colitis -> chronic relapsing inflammatory disorders of obscure origin -> |
| Ulcerative colitis | non-granulomatous inflammation limited to colon -> intense lamina infiltrate -> pseudopolyp formation -> affects mucosa and submucosa -> extends in continuous fashion -> starts in rectum, more common in whites 20-25, associated with primary sclerosing cholangitis (PSC) -> HLA-DRB1 association |
| Ulcerative colitis | 10% of cases back wash ileitis, serosa usually normal, mucosa red granular and friable, broad based ulcers, isolated islands of regenerating mucosa bulge in between to create pseudopolyps |
| Crohn's disease (terminal ileitis, regional ileitis, granulomatous colitis) | granulomatous inflammation that can affect any part of GIT from mouth to anus -> common in US, females more than males, common in Jews -> sharply delimited and transmural involvement by an inflammatory process -> presence of non caseating granulomas -> mucosal fissuring with formation of fistulas |
| Crohn's disease | small intestine alone 30%, small intestine and colon 40%, colon alone 30% -> creeping up of mesenteric fat because of fibrosis -> mesentery is thickened and fibrotic -> wall is thickened (because of edema, hypertrophy, fibrosis and inflammation) -> long narrow thickened segments of small intestine (radiographically - string sign) -> cobble-stoning of mucosa |
| Clinical features of IBD | relapsing disorder, attacks of bloody mucoid diarrhea, lower abdominal pain, abdominal cramps, tenesmus -> flare ups with physical and mental stress, fever and weight loss in severe cases, features of malabsorption -> small intestine has features of subacute intestinal obstruction |
| Extra intestinal manifestations of IBD | seen in both CD and UC (More common in UC) -> can develop even before GI symptoms -> migratory polyarthritis, sacroileitis, ankylosing spondylitis, erythema nodosum, clubbing of finger tips, sclerosing cholangitis -> increased risk of developing malignancy |
| Ischemic bowel disease | common in elderly, mild features in only mucosal involvement (nausea, vomiting and bloody stools), transmural involvement (severe abdominal pain and tenderness, gangrene, perforation, peritonitis, shock and vascular collapse, mortality high - 50-75%) -> venous vs. arterial insufficiency -> occlusive (arterial thrombosis, arterial embolism, venous thrombosis) or non-occlusive (cardiac failure, shock, dehydration) or miscellaneous (radiation, volvulus, herniation) |
| Chronic ischemic colitis | insidious, chronic inflammation and fibrosis, stricture formation, common at water shed areas (splenic flexure most common) -> intermittent attacks of pain (intestinal angina) -> can mimic inflammatory bowel disease |
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