Path 17 S790-815

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most common site for GI neoplasia in Western populations

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colon

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internal herniation

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fibrous bridges create closed loops through which other viscera may slide and become entrapped

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volvulus

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complete twisting of a loop of bowel about its mesenteric base of attachment - luminal and vascular compromise

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why is volvulus often missed clinically

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rare

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intussusception

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segment of intestine telescopes into immediately distal segment

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mucosal infarction depth

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no deeper than muscularis mucosae

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mural infarction involvement

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mucosa and submucosa

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transmural infarction

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all 3 layers

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what generally causes mucosal and mural infarctions

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secondary to acute or chronic hypoperfusion

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transmural infarction is generally caused by

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acute vascular obstruction

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epithelial lining of the intestine is relatively resistant to

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transient hypoxia

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common watershed zones in GI

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splenic flexure, somewhat the sigmoid colon and rectum

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microscopic examination of ischemic intestine

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atrophy or sloughing of surface epithelium; crypts may be hyperproliferative

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when does ischemic bowl dissease tend to occur

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older individuals with coexisting cardiac or vascular disease

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what can chronic ischemia masquerade as

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inflammatory bowel disease with episodes of bloody diarrhea interspersed with periods of healing

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CMV infection causing ischemic GI disease

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due to viral tropism infection of endothlial cells; can be complication of immunosuppresive therapy

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most common acquired GI emergency of neonates

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necrotizing enterocolitis (NEC)

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angiodysplasia

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malformed submucosal and mucosal blood vessels most often in cecum or right colon after 6th decade of life

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lesions of angiodysplasia

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ectatic nests of tortuous veins, venules, and capillaries

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steatorrhea

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excessive fecal fat and bulky, frothy, greasy, yellow, or clay colored stools

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most common malabsorptive disorders in US

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pancreatic insufficiency, celiac disease, and Crohn disease

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malabsorption can occur in what four phases of nutrient absorption

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1) inttraluminal digestion 2) terminal digestion 3) transepithelial transport 4) lymphatic transport

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dysentery

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painful, bloody, small-volume diarrhea

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4 major categories of diarrhea

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1) secretory 2) osmotic 3) malabsorptive 4) exudative

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secretory diarrhea

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isotonic stool and persists during fasting

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osmotic diarrhea

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excessive osmotic forces exerted by unabsorbed luminal solutes (lactose intolerance); abates with fasting

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malabsorptive diarrhea

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follows generalized failures of nutrient absorption and is associated with steatorrhea and is relieved by fasting

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exudative diarrhea

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due to inflammatory disease and characterized by purulent, bloody stools that continue during fasting

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what phase of digestion is mostly involved with cystic fibrosis

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intraluminal phase

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celiac disease alternative names

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celiac sprue or gluten-sensitive enteropathy

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what is celiac disease

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immune-mediated enteropathy triggered by ingestion of gluten-containing cereal such as wheat, rye, or barley

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celiac disease prevalence in caucasian or europeans

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0.5-1%

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what is gluten

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major storage protein of wheat and other grains

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where do you take a biopsy to diagnose celiac disease

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second part of duodenum or proximal jejunum (exposed to the highest concentrations of dietary gluten)

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histopathology of celiac disease

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increased numbers of intraepithelial CD8+ T lymphocytes (intraepithelial lymphocytosis), crypt hyperplasia, and villous atrophy

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what is a marked for less advanced celiac disease

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increased intraepitheliam lymphocytes especially within villus

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what else can present with intraepithelial lymphocytosis and villous atrophy

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viral enteritis; need histology anf serology for specific diagnosis

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symptomatic adult celiac disease manifestations

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anemia, chronic diarrhea, bloating, chronic fatigue

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common extra-intestinal complaints of celiac disease in older pediatric patients

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arthritis or joint pain, seizure disorders, aphthous stomatits, iron deficiency anemia, pubertal delay, and short stature

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most sensitive serology tests for celiac disease

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IgA or IgG antibodies to deamidated gliadin; anti-endomysial antibodies specific but less sensitive

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what should be measeured if IgA deficiency present with suspected celiac disease

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titers of IgG to tissue transglutaminase and deaminated gliadin measured

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most common celiac related cancer

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enteropathy-associated T-cell lymphoma then small intestinal adenocarcinoma

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what does tropical spruae tend to involve

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distal small bowel; antibiotics generally cause rapid recovery

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autoimmune enteropathy

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X-linked disorder with severe diarrhea and autoimmune disease most often in young children

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IPEX

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immune dysregulation, polyendocrinopathy, enteropathy, and X-linkage; describe autoimmune enteropathy

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what gene causes autoimmune enteropathy

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FOXP3 gene - transcription faactor expressed in CD4+ regulatory T cells

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congenital lactase deficiency

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mutation in gene encoding lactase; autosomal recessive; rare

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acquired lactase deficiency

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down-regulation of lactase gene

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abetalipoproteinemia

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rare autosomal recessive; inability to secrete triglyceride-rich lipoproteins, accumulate in epithelial cells

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mutation in abetalipoproteinemia

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microsomal triglyceride transfer protein (MTP) that catalyzes transport of triglycerides, cholesterol esters, and phospholipids

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cholera specs

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comma-shaped, gram-negative bacteria

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main mode of transmision of cholera

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contaminated drinking water, can be in food (seafood associated)

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animal reservoirs of cholera

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shellfish and plankton

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what causes disease in cholera

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preformed enterotoxin encoded by a phage released by the Vibrio organism

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cholera toxin specs

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five B subunits and single A subunit

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how does the toxin cause disease step 1

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B binds GM1 ganglioside on surface of intestinal epithelial cells, endocytosis to ER

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how does the toxin cause disease step 2

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fragment of A released and refolds and interacts with cytosolic ADP ribosylation factors (ARFs)

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how does the toxin cause disease step 3

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activates stimulatory G protein Gsalpha increasing cAMP

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how does the toxin cause disease step 4

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CFTR channels open and release chloride ions into lumen

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how does the toxin cause disease step 5

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causes secretion of bicarb, Na+, and water leading to massive diarrhea

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campylobacter enterocolitis

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most common enteric pathogen in developed countries; associated with improperly cooked chicken

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enteric fever occurs when

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bacteria proliferate within lamina propria and mesenteric lymph nodes

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campylobacter specs

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comma-shaped, gram-negative bacteria; diagnosed by stool culture

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shigellosis

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gram-negative bacilli; unencapsulated, nonmotile, facultative anaerobes; one of most common causes of bloody diarrhea

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pathogenesis of shigellosis

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resistant to harsh acidic environment of stomach, taken up by M cells, proliferates intracellularly, escape to lamina propria

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where is shigellosis most prominent

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left colon, sometimes ileum

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what can confirm diagnosis og shigellosis

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stool culture; antibiotics can shorten course; antidiarrheal meds prolong symptoms and prolong clearance

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reiter syndrome

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triad of sterile arthritis, urethritis, and conjuntivitis

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salmonellosis

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gram-neg bacilli; two divisions - salmonella typhi and salmonella; transmision via contaminated food

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how does salmonella infect

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virulence genes that encode type III secretion system capable of transferring bacterial proteins into M cells and enterocytes

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what do transferred proteins from salmonella do

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activate host cell Rho GTPases and trigger actin rearrangement and bacterial uptake that allow bacterial growth within phagosomes

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what is essential for diagnosis of salmonella

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stool culture

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antibiotics and salmonella

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not recommended in most cases - prolongs carrier state or even cause relapse and doesn't shorten course

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typhoid fever aka enteric fever pathogeneis

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survive in gastric acid and once in small intestine are taken up by and invade M cells

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morphology of typhoid fever

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peyer patches enlarge in terminal ileum; draining mesenteric lymph node enlargement; mucosal shedding creates oval ulcers oriented along axis of ileum; spleen enlarged and soft

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presenting symptoms of typhoid fever

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anorexia, abdominal pain, nausea, vomiting, bloody diarrhea, followed by short asymmptomatic phase that gives way to bacteremia and fever with flu-like symptoms

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what can diagnosis thphoid fever

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90% have positive blood cultures in febrile phase

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what occurs if patients aren't treated in early phases of typhoid fever

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2 weeks sustained high fevers and abdominal tenderness; rose spots on chest and abdomen

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yersinia affecting GI pathogenesis

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invade M cells and use bacterial adhesion proteins to bind to host cell integrins; iron enhances virulence

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what do yersinia infections preferentially involve

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ileum, appendix, and right colon

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where do yersinia organisms divide

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extracellularly in lymphoid tissue - causes regional lymph node and Peyer patch hyperplasia

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what can yersinia infections be confused with

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Crohns disease

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postinfectious complications of yersinia

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sterile arthritis, reiter syndrome, myocarditis, glomerulonephritis, and thyroiditis

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E coli

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gram neg bacilli that colonize healty GI tract

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what do enterotoxigenic E coli produce

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heat-liable toxin (LT) and heat-stable toxin (ST) - induce chloride and water secretion while inhibiting intestinal fluid absorption

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what does LT toxin cause

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similar to cholera toxin; activates adenylate cyclase increasing cAMP

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what does ST toxin cause

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bind guanylate cyclase and increase intracellular cGMP causing similar affects as LT toxin

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clinical symptoms of enterotoxigenic e coli

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secretory, noninflammatory diarrhea, dehydration, and sometimes shock

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enterohemorrhagic e coli

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shiga-like toxins; two categories: O157:H7 and non-O157:H7

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enteroinvasive e coli

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similar to shigella; do not produce toxins, invade epithelial cells and cause non-specific features of acute self limiting colitis

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enteroaggregative e coli

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unique pattern of adherence to epithelial cells - adgerence fimbriae via dispersin on bacterial surface

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pseudomembranous colitis

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generally caused by clostridium difficile aka antibiotic-associated colitis

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how is c difficile diagnosed

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usually via toxin instead of culture

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whipple disease

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rare, multivisceral chonic disease; malabsorption, lymphadenopathy, and arthritis of undefined origin

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what is responsible for whipple disease

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gram positive actinomycete - tropheryma whippelii; rod shaped

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why do symptoms occur in whipple disease

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organisms accumulate in small intestine lamina propria and mesenteric lymph nodes causing lymph obstruction

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morphology of whipple disease

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dense accumulation of distended, foamy macrophages in small intestine lamina propria

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triad of symptoms in whipple disease

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diarrhea, weight loss, and malabsorption; extraintestinal symptoms include arthritis, arthralgia, fever, lymphadenopathy, neurologic, cardiac, or pulmonary disease

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viral gastroenteritis common groups

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norovirus, rotavirus, adenovirus

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norovirus

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small icosahedral viruses with single stranded RNA genome; causes half all gastroenteritis outbreaks worldwide

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rotavirus

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encapsulated with segmented double-stranded RNA genome; most common cause of diarrheal mortality worldwide

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what does rotavirus destroy

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mature enterocytes in small intestine and villus surface is repopulated by immature secretory cells

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ascaris lumbricoides

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nematode infecting over 1 million individuals; ingest eggs and larvae penetrate intestinal mucosa

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symptoms ascaris lumbricoides cause

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adult worm masses induce eosinophil-rich inflammatory rxn that can physically obstruct intestine or biliary tree

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strongyloides

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penetrate unbroken skin and migrate through lungs and then reside in intestine while maturing into adults

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necator duodenale and ancylostoma duodenale

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hookworms infect over 1 billion; larval penetration through skin, dvlp in lungs, go to duodenum and attach to mucosa to suck blood and reproduce

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enterobius vermicularis

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pinworms; rarely cause serious illness; live entire life within intestineal lumen

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trichuris trichura

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whipworms; does not penetrate mucosa

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schistosomiasis

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disease in intestines involves adult worms residing in mesenteric veins

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intestinal cestodes

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tapeworms; reside exclusively in intestinal lumen; grow large

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entamoeba histolytica

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protozoan; cysts have chitin wall and are resistant to gastric acid; colonize surface of colon and release trophozoites that reproduce

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giardia lamblia

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most common pathogenic parasitic infection in humans; cysts resistant to chlorine; flagellated protozoans

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what do giardia cause

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decreased expression of brush-border enzymes, microvillous damage, and apoptosis of small intestinal epithelail cells

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what is important for clearance of giardia

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secretory IgA and mucosal IL-6

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histological appearance of giardia

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pear shape with 2 nuclei of equal size

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cryptosporidium

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cause of acute, self-limited disease in immunologically normal hosts; chlorine resistant

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Irritable Bowel Syndrome

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chronic, relapsing abdominal pain, bloating, and changes in bowel habits

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diagnosing criteria for IBS

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occurance of abdominal pain or discomfort at least 3 days per month over 3 months, improvement with defecation, change in stool frequency or form

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inflammatory bowel disease (IBD)

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chronic condition resulting from inappropriate mucosal immune activation; Crohn disease and ulcerative colitis

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ulcerative colitis

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severe ulcerating inflammation limited to colon and rectum and extends only to mucosa and submucosa

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Crohn disease involvement

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regional enteritis (infrequent ileal involvement); may involve any area of GI tract and is typically transmural

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what are crohn's and ulcerative colitis thought to be caused by

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not autoimmune; combination of defects in host interactions with intestinal microbiota, intestinal epithelial dysfunction, and aberrant mucosal immune responses

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potential genetic defect in crohns

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NOD2 - protein binds intracellular bacterial peptidoglycans and activates NF-kB

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2 theories of why NOD2 increases suscepability to crohns

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; regulate immune responses to prevent excessive action by luminal microbes

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two other genes noteworthy for Crohn's involvement

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ATG16L1 and IRGM

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ATG16L1 fxn (autophagy-related 16-like)

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part of autophagosome pathway that is critical to host cell responses to intracellulat bacterial and perhaps epithelial homeostasis

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IRGM fxn (immunity-related GTPase M)

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autophagy and clearance of intracellular bacteria

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what is IL-23 involved in that makes it protective against Crohns and ulcerative colitis

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dvlp and maintenance of Th17 cells, may attenuate pro-inflammatory Th17 responses

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critical component of IBD pathogenesis

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deranged epithelial fxn (transepithelial transport, paneth anti-microbial products, etc)

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most common sites of Crohn disease involvement

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terminal ileum, ileocecal valve, cecum; skip lesions; strictures common

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intestinal wall in crohns

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thickened and rubbery as a consequence of edema, inflammation, submucosal fibrosis, and hypertrophy of muscularis propria

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halmark of crohns seen in 35% of cases

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noncaseating granulomas

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pancolitis

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disease of entire colon in ulcerative colitis

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what percent of crohns and ulcerative colitis test positive for perinuclear anti-neutrophil cytoplasmic antibodies

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11% crohns and 75%

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crohns or ulcerative colitis tend to lack Saccharomyces cerevisiae

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ulcerative colitis

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NOD2 polymorphisms

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barrier dysfunction association

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ECM1

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inhibits matrix metalloporteinase 9; associated with ulcerative colitis; inhibition reduces severity

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extra-intestinal manifestations of Crohns

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uveitis, migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum, and clubbing of fingertips

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major differences in ulcerative colitis vs Crohns

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mural thickening NOT present, serosal surface normal, and strictures do not occur

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diversion colitis

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mucosal erthema and friability, dvlp numerous mucosal lymphoid follicles; due to changes in luminal microbiota

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microscopic colitis (collagenous and lymphocytic types)

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present with chronic, nonbloody, watery diarrhea without weight loss

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diverticulitis

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outpouchings of colonic mucosa and submucosa

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why doesn't diverticulitis occur outside of colon

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other parts of intestine is reinforced by external longitudinal layer of muscularis propria, colon has this muscle gathered into 3 bands (taeniae coli)