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GI Lab Studies
Gastroenterology
| Question | Answer |
|---|---|
| Zollinger Ellison labs | elevated acid (gastric pH); serum gastrin; imaging study to locate primary tumor |
| Carcinoid syndrome | Tumors of argentaffin (secretory) cells; assoc w/carcinoid tumor of sm bowel mets to liver; sx flushing & diarrhea |
| Amylase (panc disorders): specimens: | serum, urine, pleural fluid, peritoneal fluid; Lipase: serum |
| Amylase: pronounced elevation in: | acute pancreatitis, pancreatic pseudocyst |
| Amylase: Moderate elevation in: | panc ca, mumps, salivary gland inflam, perforated peptic ulcer |
| Lipase | breaks down TGs; very specific for panc dz (> amylase); pronounced elevation in acute pancreatitis, pancreatic pseudocyst; mod elev in panc ca |
| Pancreas enzymes | Amylase, Lipase |
| Liver enzymes | AST, ALT, GGT, Alk phos |
| Biliary enzymes | Alk phos; GGT, (bilirubin) |
| Hepatic function panel | Na, K, Cl, CO2, glucose, BUN, Cr, Ca, albumin, phosphorus |
| Albumin | part of total protein formed in liver; 14-20 d half life; in liver damage, levels drop slowly; prealbumin more sensitive to rapid damage |
| ALT & AST: where found | ALT: high in liver (mod in kidney, heart, sk mx); ALT more specific for liver damage than AST or alk phos; AST: high in liver, heart, brain, sk mx |
| ALT/AST: abnml labs | ALT: liver injury > cirrhosis/obstruction; AST: cell necrosis |
| Biliary colic | GS: transient cystic duct obstruction; confirm dx with US or CT |
| Cholecystitis | stone in cystic duct; inc WBC w/left shift; inc amylase/lipase; mild inc AST, ALT, bili, Alk phos |
| Choledocholithiasis | stone in CBD; mild inc bili; mod inc alk phos |
| Cholangitis | infxn biliary tree; inc LFT & WBC |
| GGT | highest in liver/biliary tract; asses cholestasis & biliary obstruction (d/t mets?); elevated d/t EtOH |
| Alk phos | rapidly div/metab active cells; high in PG, bone formation, intestinal dz |
| Hyperbili: conj vs unconj | unconj 15-20% of TBil (accelerated RBC hemolysis, hepatitis, drugs); conj >50% TBil (intrahepatic cholestasis: biliary cirrhosis, drugs; hepatocellular damage: drugs, sepsis, inflam, scarring; obstruction: GS) |
| LFTs: hepatitis pattern | A/G ratio >1; ALT >1000; ALT > AST; GGT high if EtOH hep; Bili D>I |
| LFTs: cirrhosis pattern | A/G ratio <1; AST > ALT; GGT high if EtOH/biliary cirrhosis; Bili I > D |
| ALT/AST elevation: defns | mild elev <5x ULN; mod elev 5-10 x nml; marked elev >10 x nml |
| If alk phos high out of proportion to ALT/AST: | evaluate cholestasis with US/CT |
| UC labs | Anemia; Low serum alb; Elevated ESR; Neg stool cx |
| Normal peritoneal fluid: | 50 ml vol; straw-colored & clear; < 100,000 RBCs/microL; <300 WBCs/microL |
| Paracentesis: testing | Cell counts, cytology, Gram stain, chem testing (glucose, amylase, ammonia, alk phos) |
| Diagnostic Peritoneal Lavage: indications | Eval of abd trauma, intraperitoneal hemorrhage, ruptured intestine or other organs |
| Normal D-xylose tests suggests: | pancreatic insufficiency, reduced bile salts, lymphatic obstruction (all may be related to malabsorption) |
| Hydrogen breath test is used to diagnose: | lactase deficiency |
| Amylase: false negative may be related to: | Acute on chronic pancreatitis (eg, EtOH). Elevated TG (associated decreased amylase activity) |
| Amylase: false positive may be related to: | Other abdominal/salivary gland process. Acidemia. Renal failure. Macroamylasemia. |
| Lipase: false positive may be related to: | Renal failure. Other abdominal process. DKA. HIV. Macrolipasemia. |
| Causes of elevated bilirubin | choledocholithiasis (most common); liver disease; hemolysis (indirect bili); recent transfusion; gram-negative sepsis; TPN; obstruction (tumor, mass, stone); Gilbert |
| Causes of elevated LDH | COVID-19; heart dz; tissue infarct (renal, pulmonary); hemolysis; liver dz (hepatitis, cirrhosis, cholangitis); malignancy (lymphoma, myeloma, leukemia) |
| Elevated haptoglobin may be due to: | Inflammation; Infection; Malignancy; Surgery; Trauma; Corticosteroids |
| Decreased haptoglobin may be due to: | Hemolysis; Liver disease; Malnutrition; Estrogens; Pregnancy |
| Biliary dz: dx test | US is definitive for GS; US or HIDA for cholecystitis; xray/CT for porcelain; US or ERCP for choledocho |
| CEA to dx: | Colon Carcinoma |
| AFP to dx: | Hepatocellular carcinoma (also high alk phos), testicular seminoma (germ cell tumor) |
| CA 19-9 to dx: | Pancreatic Ca |
| CA-125 to dx: | Ovarian Carcinoma |
| Gastric ca: histo | 95% adenocarcinoma; other: lymphoma, SSC |
| Conjugated bilirubin = | direct; bound to glucuronic acid; water soluble; caused by obstruction of outflow tract or in the liver |
| Unconjugated bilirubin = | indirect; water insoluble; caused by hemolysis |
| Chronic pancreatitis: dx tests | fecal fat/elastase; secretin stimulation test |
| Pancreatic cancer: labs | Alk Phos; Bilirubin, CA 19-9 |
| Dx giardiasis with: | giardia antigen stool assay |
| Liver disease lab workup | Hep A, B, C; ANA; ASMA; IgG; Anti-mito Ab (primary biliary cirrhosis) |
| ALT & AST >1000 may be due to: | hepatitis, shock, toxins (acetaminophen). Hepatocellular injury: correlates w/degree of cell death |
| Abnormal AST/ALT | ALT: liver injury > cirrhosis/obstruction; AST: cell necrosis; ALT:AST >1.0 = infxs hep; AST:ALT >2:1 = alcoholic hep; <500: EtOH; poss normal in cirrhosis |
| Albumin = | part of total protein formed in liver; 14-20 d half life; in liver damage, levels drop slowly; prealbumin more sensitive to rapid damage |
| ALT: where found | ALT: high in liver (mod in kidney, heart, sk mx) |
| ALT is more specific than AST or alk phos for: | Liver damage |
| Alk phos | liver, bone, intestinal tract, placenta, kidney; elevated in liver damage/obstruction; if elevated more than AST/ALT, more likely biliary disorder |
| Hep C dx labs | ELISA (pos in 8-10 wks; good screen for chronic); HCV RNA; HCV genotype |
| Serum ascites albumin gradient | paracentesis; if gradient >1.1: portal HTN |
| IBD labs | often anemic (Fe def & chronic dz), leukocytosis, elevated CRP (CD); DO NOT ORDER serologies (ASCA, Cbir, OmpC & Crohns; p-ANCA & UC) |
| Amylase: pronounced elevation in: | acute pancreatitis, pancreatic pseudocyst |
| Amylase: Moderate elevation in: | panc ca, mumps, salivary gland inflam, perforated peptic ulcer |
| Lipase: fn & dx utility | breaks down TGs; very specific for panc dz (> amylase); pronounced elevation in acute pancreatitis, pancreatic pseudocyst; moderately elevated in panc cancer |
| Liver enzymes | AST, ALT, GGT, Alk phos |
| Biliary enzymes | Alk phos; GGT, (bilirubin) |
| GGT | highest in liver/biliary tract; assess cholestasis & biliary obstruction (d/t mets?); elevated d/t EtOH |
| Alk phos: where found: | rapidly div/metab active cells; high in PG, bone formation, intestinal dz |
| LFTs: hepatitis pattern | A/G ratio >1; ALT >1000; ALT > AST; GGT high if EtOH hep; Bili D>I |
| LFTs: cirrhosis pattern | A/G ratio <1; AST > ALT; GGT high if EtOH/biliary cirrhosis; Bili I > D |
| ALT/AST elevation: defns | mild elev <5x ULN; mod elev 5-10 x nml; marked elev >10 x nml |
| If alk phos high out of proportion to ALT/AST: | evaluate cholestasis with US/CT |
| UC labs | Anemia; Low serum alb; Elevated ESR; Neg stool cx |
| Normal peritoneal fluid: | 50 ml vol; straw-colored & clear; < 100,000 RBCs/microL; <300 WBCs/microL |
| FOBT guidelines | CLIA waived; 3 serial stools; avoid red meat & >250 mg vitamin C x 3 days; avoid ASA >325 mg x 7 days |
| FOBT other sources of false pos | EtOH, anticoag, steroids, CTx, iodine prep |
| C diff toxin assay specimen criteria | specimen >5 ml (fridge if >1 hr); pt 5 soft/liquid stools /24 hr; submit 3 specimens on 3 different days |
| Gold std for pseudomembranous colitis | tissue cx (rarely done; usu do toxin assays); if done, need bx and anaerobic cx |
| Hyperbilirubinemia: conjugated vs unconjugated | unconjugated 15-20% of Total bili (accelerated RBC hemolysis, hepatitis, drugs). Conjugated >50% of TBil (intrahepatic cholestasis: biliary cirrhosis, drugs; hepatocellular damage: drugs, sepsis, inflam, scarring; obstruction: GS) |
| Serologic tests for celiac: | anti-endomysial Ab (Most specific); TOC (cheaper, less tech difficult): anti-tGA (total IgA & genetic tests may also be indicated) |
| AST: where found: | AST:high in liver, heart, brain, sk mx |
| Biliary labs | bilirubin, alk phos, ALT, AST |
| Cholestatic vs hepatitis: labs | cholestasis: bili/alk phos high; hep: ALT/AST high |
| jaundice labs | Bilirubin (total & direct), ALT, AST, alk phos |
| Lab pattern in pt with icterus | Bilirubin >3mg/dl; indirect bili high = hemolysis; Direct bili high = liver dz. |
| Elevated unconjugated (indirect) bilirubin indicates: | hemolysis |
| Elevated conjugated (direct) bilirubin indicates: | liver disease |
| Elevated AST & ALT indicates: | hepatocellular disease |
| Elevated alk phos indicates: | cholestatis or obstruction |
| IBD labs | CBC, ESR/CRP, albumin, stool C&S, O&P, WBC, fecal fat; CD also p-ANCA & ASCA |
| Celiac dz labs | CBC, ESR, PT, Fe, B12, folate; Ca, alk phos, albumin, beta-carotene; anti-endomysial IgA (most specific); anti-tTGA (tissue transglutaminase; TOC); Total IgA |
| Zollinger Ellison testing | fasting gastrin level (>1000 is dx); secretin stim test (normal pt: no fx on gastrin; ZE pt: dramatic increase) |
| Primary sclerosing cholangitis (PSC) labs: | Elevated alk phos; LFT, anti-mito Ab; ERCP/MRCP |
Created by:
Abarnard
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