Abdominal Pain: Laboratory Test Pearls and Pitfalls

1. Abdominal Pain: Laboratory Test Pearls and Pitfalls Joe Lex, MD, FAAEM Temple University Hospital Philadelphia, PA – USA Education Chair, American Academy of Emergency Medicine

2. Abdominal Pain 10% of Emergency Department visits 40% diagnosed as “nonspecific” 50% of those admitted discharged with change in diagnosis

3. Differential Includes… Diabetic ketoacidosis Alcoholic ketoacidosis Uremia Sickle cell disease Porphyria Systemic lupus Vasculitis Glaucoma Hypertension Scorpion sting Methanol poisoning Black widow spider bite

4. Differential Includes… Heavy metal toxicity Acute coronary syndrome Pneumonia Pulmonary embolism Testicular torsion Herniated thoracic disc Streptococcal pharyngitis Rocky Mountain spotted fever Mononucleosis Etc.

5. Differential Includes… …and those are just the extraabdominal causes of abdominal pain I’d be happy with a test that could tell me that the source of pain was really the abdomen.

6. Literature Suggests We Get… White blood cells Electrolytes Glucose Renal functions Liver functions Amylase / lipase Pregnancy test Urinalysis C-reactive protein Procalcitonin Lactate Phosphorus Leukocyte elastase Others??

7. Literature Suggests We Get…

8. First and Foremost… Female + ovaries = pregnancy When patients said… “My last period was on time.” “I don’t think I’m pregnant.” “I can’t possibly be pregnant.” …10% were pregnant.

9. Abdominal Pain

10. Right Upper Quadrant

11. Gall Bladder

12. Gall Stones / Colic No pathognomonic study Lab studies should all be normal ? ALT / AST: think hepatitis ? alkaline phosphatase / bilirubin: think common bile duct obstruction ? amylase / lipase: think pancreatitis

13. Common Duct Stones ? serum bilirubin in 32% ? aminotransferases in 34% ? alkaline phosphatase in 22% Common duct stones in 17.4% Best predictive value for duct stone: ? alkaline phosphatase (46%)

14. Common Duct Stones ? bilirubin and alkaline phosphatase associated with common duct stones Combination of bilirubin level > 3.0 and alkaline phosphatase >250: >75% chance of common duct stone ? serum or urine amylase: little, if any, value

15. Cholecystitis 40 patients: pathologically confirmed acute cholecystitis Fever at presentation: 10% Leukocytosis at presentation: 60% No single / combination of clinical / laboratory findings at time of presentation identified all patients

16. Cholecystitis Acute cholecystitis – nongangrene: 71% lack fever 32% lack leukocytosis 28% lack fever and leukocytosis Acute cholecystitis – gangrene: 59% lack fever 27% lack leukocytosis 6% lack fever and leukocytosis

17. Hepatitis

18. Hepatitis ALT usually >AST Both 10 – 100 times normal ? prothrombin time first sign of complicated course WBC / differential not helpful

19. Spot Urine Dipstick 70 – 74% sensitive for serum bilirubin 43 – 53% sensitive for other liver enzyme abnormalities 77 – 87% specific for hepatitis

20. Spot Urine Dipstick 83 – 86% positive predictive values for detecting at least one LFT abnormality 85% negative predictive value for serum bilirubin elevations, but lower for other LFTs

21. Typical AST / ALT Values

22. Abdominal Pain

23. Right Lower Quadrant

24. Appendix

25. White Cells and Appendicitis Typical range: 12,000–18,000 / mm3 Leukocytosis in 75 – 80% Immature white cells in 75 – 80% Same as in gastroenteritis, pelvic inflammatory disease, ruptured ovarian cyst, ectopic pregnancy, etc.

26. White Cells and Appendicitis Progressive increase in white cell count over time: unreliable Elderly (>60!) with appendicitis: normal white cell count 45% of time

27. Proportion of patients with elevated white cell count and perforation equal to proportion perforated with normal white cell count White Cells and Appendicitis

28. White Cells and Appendicitis White cell count does not effect surgeon’s decision to operate

29. White Cells and Appendicitis White cell count and differential normal in 4 – 11% of patients with appendicitis

30. Other Laboratory Studies C-reactive protein and leukocyte elastase: not consistently reliable to rule in or rule out appendicitis BUT…

31. Triple Test …if white cell count <9000 / mm3 AND …if neutrophils <75% of total white cells AND …C-reactive protein <0.6 mg/dL, THEN Negative predictive value approaches 100%

32. Urine and Appendicitis Proven appendicitis: 20 – 30% have blood, white cells, or bacteria in urine Retrocecal appendicitis: abnormal urine in 50%

33. Abdominal Pain

34. Epigastrium

35. Pancreas

36. Amylase Elevated in… Pancreatitis Exctopic pregnancy Macroamylasemia Parotitis Renal failure Bowel obstruction or infarct Perforated ulcer Acute peritonitis Mesenteric ischemia Other causes

37. Amylase Not Very Sensitive Rises within 6 to 24 hours Peaks in 48 hours Normalizes in 5 to 7 days Sensitivity decreases after first 24 to 48 hours

38. Amylase Not Very Specific Amylase normal in 25 % of patients with acute pancreatitis Highly specific if elevated 5 times above upper limit of normal

39. Lipase Sensitivity / Specificity Elevated in pancreatitis, bowel obstruction, perforated ulcer Just as sensitive as amylase Probably more specific than amylase (80 – 99%) At five times upper limit of normal: 60% sensitive, 100% specific

40. Biliary Pancreatitis: Labs

41. Other Possible Markers Phospholipase A2 C-reactive protein Interleukin-6 Interleukin-8 Trypsinogen Trypsin activation peptide Procarboxy-peptidase B activation peptide Serum amyloid A Procalcitonin Leukocyte elastase

42. Ulcer Disease

43. Helicobacter pylori

44. Abdominal Pain

45. Diffuse

46. Diffuse

47. Small Bowel Obstruction WBC: not sensitive, not specific Hemoglobin: high if dry, low if bleeding Amylase, lactate, creatine phosphokinase: elevated late Electrolytes, renal function: if prolonged volume loss

48. Small Bowel Obstruction History, physical, temperature, x-ray, white blood count, serum amylase: cannot differentiate simple bowel obstruction from strangulated bowel

49. Small Bowel Ischemia Leukocytosis: common, nonspecific Hemoconcentration, metabolic acidosis with base deficit, hyperamylasemia: nonspecific, present in >50% Lactate: ~100% sensitive, 42 – 87% specific

50. “Nonspecific” Abdominal Pain Most common in young Low social class Psychiatric disorders BUT… …If older than 50 years, 10% shown to have intra-abdominal cancer within next year

51. Other Causes Pain Diverticulitis Ruptured abdominal aortic aneurysm Perforated viscus Regional enteritis Psoas abscess Endometriosis Mittelschmerz Splenic rupture / infarct Cecal volvulus Gastric volvulus Sigmoid volvulus Rectus hematoma Etc.

52. No Magic Bullet History and physical exam still most important Lab studies helpful if interpreted properly