Step 1 - GI 2

denniskwinn's version from 2015-04-25 16:01


Question Answer
AppendicitisAll age groups; most common indication for emergent abdominal surgery in children. Initial diffuse periumbilical pain ---? locali zcd pain at McBurney's point (X the distance from iliac crest to umbilicus). Nausea, fever; may perforate → peritonitis.
Differential for appendicitisdiverticulitis (elderly), ectopic pregnancy (use p-hCG to rule out).
DiverticulumBlind pouch protruding from the alimentary tract that communicates with the lumen of the gut. Most are acquired and are termed "false" in that they lack or have an attenuated muscularis externa. Most often in sigmoid colon. True involves all 3 gut wall layers outpouching - false = only mucosa and submucosa (happens often where vasa recta perforate muscularis externa
DiverticulosisMany diverticula, Common in 50% of people> 60y. Caused by ↑ intraluminal pressure and focal weakness in colonic wall. Associated with low-fiber diets. Most often in sigmoid colon. - often asymptomatic or associated with vague discomfort and/or painless rectal bleeding
DiverticulitisInflammation of diverticula classically causing LLQ pain, fever, leukocytosis. may perforate → peritonitis, abscess formation, or bowel stenosis. May cause bright red rectal bleeding, may also cause colovesical fistula→pneumaturia - Treat with antibiotics
Zenker’s diverticulumFalse diverticulum. Herniation of mucosal tissue at junction of pharynx and esophagus. Presenting symptom: halitosis (due to trapped food particles), dysphagia, obstruction.
Meckel’s diverticulumPersistence of the vitelline duct or yolk stalk. May contain ectopic acid-secreting gastric mucosa and/or pancreatic tissue. Most common congenital anomaly of the GT tract. Can cause bleeding, intussusception, volvulus, or obstruction near the terminal ileum. Contrast with omphalomesenteric cyst = cystic dilatation of vitelline duct - five 2’s - 2 inches long, 2 feet from ileocecal valve, 2% population, presents in first 2 years of life, may have two types of epithelia
Intussusception"telescoping" of 1 bowel segment into distal segment; can compromise blood supply. Unusual in adults (associated with intra luminal mass or tumor). Majority of cases occur in children (usually idiopathic; may be viral [adenovirus]) . Abdominal emergency in earl y childhood.
Volvulustwisting of portion of bowel around its mesentery; can lead to obstruction and infarction. May occur at cecum and sigmoid colon, where there is redundant mesentery. Usually in elderly.
Hirschsprung’s diseaseCongenital megacolon characterized by lack of ganglion cells/enteric nervous plexuses (Auerbach's and Meissner's plexuses) in segment on intestinal biopsy. Due to Failure of neural crest cell migration. Presents as chronic constipation early in life. Dilated portion of the colon proximal to the aganglionic segment, resulting in a "transition zone." Involves rectum. Usually failure to pass meconium. Increased risk with down’s syndrome
Duodenal atresiaCauses early bilious vomiting with proximal stomach distention ("double bubble") due to Failure of recanalization of small bowel. Associated with Down syndrome.
Meconium ileusin cystic fibrosis, meconium plug obstructs intestine, preventing stool passage at birth.
Necrotizing enterocolitisNecrosis of intestinal mucosa and possible perforation. Colon is usually involved, but can involve entire Gl tract. in neonates, more common in preemie (↓ immunity).
Ischemic colitisReduction in intestinal blood flow causes ischemia. Pain after eating → weight loss. -Commonly occurs at splenic flexure and distal colon. Typically affects elderly.
AdhesionAcute bowel obstruction , commonly from a recent surgery. Can have well-demarcated necrotic zones.
AngiodysplasiaTortuous dilation of vessels ~ bleeding. Most often found in cecum. terminal ileum, and ascending colon . More common in older patient . Confirmed by angiography.
Colonic PolypsMasses protruding into gut lumen ~ sawtooth appearance. 90% are non-neoplastic. Often rectosigmoid .
Adenomatous polyps precancerous. Malignant risk is associated with ↑ size, villous Histology, ↑ epithelial dysplasia. Precursor to colorectal cancer (CRC). The more villous the polyp , the more likely it is to be malignant
Hyperplastic polypMost common non-neoplastic polyp in colon (> 50% found in rectosigmoid colon).
Juvenile PolypMostly sporadic lesion in children < 5 years of age. 80% in rectum. If single, no malignant potential. - Juvenile polyposis syndrome-multiple juvenile polyps in GI tract, ↑ risk of adenocarcinoma
Peutz-Jegher syndromeSingle polyps are not malignant. - autosomal-dominant syndrome featuring multiple non malignant hamartomas throughout Gl tract, along with hyperpigmented mouth, lips, hands, genitalia. Associated with ↑ risk of CRC and other visceral malignancies
Colorectal carcinoma epidemiology3rd most common cancer; 3rd most deadly in United States. Most patients are > 50 years of age. - 25% have a family history
Familial adenomatous polyposis (FAP) autosomal-dominant mutation of APC gene on chromosome 5q. Two-hit hypothesis - 100% progress to CRC. Thousands of polyps; pancolonic; always involves rectum.
Gardner's syndrome FAP + osseous and soft tissue tumors, retinal hyperplasia.
Turcot's syndromeFAP + malignant CNS tumor. TURcot = TURban.
Hereditary nonpolyposis colorectal cancer (HNPCC/Lynch syndrome)-autosomal dominant mutation of DNA mismatch repair genes. - 80% progress to CRC. Proximal colon is always involved.
Colorectal cancer risk factorsIBD, Streptococcus bovis bacteremia, tobacco use, large villous adenomas, juvenile polyposis syndrome, Peutz-Jeghers syndrome
Colorectal cancer presentation in distal colonObstruction, Colicky pain, Hematochezia
Colorectal cancer presentation in proximal colon dull pain, iron deficiency anemia, fatigue
Colorectal cancer diagnosisIron deficiency in older mailes, Screen patients > 50y with stool occult blood test and colonoscopy, CEA tumor marker, “Apple Core” lesion seen on barium enema x-ray
Molecular pathogenesis of CRC2 pathways: 1. Microsatellite instability pathway (15%) - DNA mismatch repair gene mutations→sporadic and HNPCC syndrome, mutations accumulate, but no defined morphologic correlates 2. APC/B-catenin pathway (chromosomal instability)(85%)
CRC mutation progressionloss of APC (decreased intercellular adhesion and increased proliferation) then loss of KRAS (unregulated intracellular signal transduction) then loss of p53 (increases tumorigenesis)
Carcinoid tumorTumor of endocrine cells. Comprise 50% of small bowel tumors. Most common site of malignancy is in small intestine. "Dense core bodies" seen on EM. Often produce 5-HT, which can lead to carcinoid syndrome. Classic symptoms: wheezing, right-sided heart murmurs.diarrhea, flushing. If tumor is confined to GI system, no carcinoid syndrome is observed, since liver metabolizes 5-HT. If tumor or metastases ( usually to liver) exist outside Gl system, carcinoid syndrome is observed. Thus, tumor location determines whether or not the syndrome appears. Most common sites of tumor are appendix, ileum and rectum.
Micronodular cirrhosisnodules < 3 mm, uniform size. Due to metabolic insult (e.g., alcohol, hemochromatosis, wilson's disease).
Macronodular cirrhosisnodules > 3 mm, varied size. Usually due to significant liver injury leading to hepatic necrosis. (e.g., postinfectious or drug induced hepatitis). ↑ risk of hepatocellular carcinoma.
Effects of portal hypertensionEso varices (hematemesis), Peptic ulcer (Melena), Splenomegaly, Caput medusae, Gastropathy, Hemorrhoids
Effects of liver cell failureBASIC FAST JAG - Bleeding, Anemia, Scleral Icterus, Coma, Fetor hepaticus(stinky breath), Ankle adema, Spider nevi, Testicular atrophy, Jaundice, Asterixis, Gynecomastia
Viral hepatitis aminotransferase levelsALT > AST
Alcoholic hepatitis aminotransferase levelsAST>ALT
Myocardial Infarction aminotransferase levels AST
GGTincreased with heavy alcohol consumption
Alkaline phosphataseuseful in diagnosis of obstructive liver disease ( hepatocellular carcinoma), bone disease, bile duct disease
Serum amylase diagnostic useAcute pancreatitis, Mumps
Serum Lipase diagnostic useAcute pancreatitis
Serum Ceruloplasmin major diagnostic use↓ in Wilson’s disease
Reye’s syndromeRare, often fatal childhood hepatoencephalopathy. Findings: mitochondrial abnormalities, fatty liver (microvesicular fatty change), hypoglycemia, coma. Associated with viral infection (especially VZV and in Auenza B) that has been treated with salicylates. Reye's syndrome Mechanism: aspirin metabolites ,↓ Beta oxidation by reversible inhibition of mitochondrial enzyme. Aspirin is not recommended for children (use acetaminophen, with caution).