Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (151 page)

There are no pathognomonic findings for this disease, nor are there findings that distinguish it from Crohn disease.

   Laboratory Findings

Serology
: P-ANCA are found in 70% of ulcerative colitis patients but only occasionally in cases of Crohn disease. Stools are negative for usual enteric pathogens and parasites.

Hematology
: With diarrhea and fever, hemoglobin <7.5 g/dL, increased neutrophil count, and ESR >30 mm/hour indicate severe disease.

Core laboratory
: Serum ALP often increased slightly. Other liver function tests are usually normal. Stools are positive for blood.

   Other Considerations

   Laboratory changes due to complications or sequelae (e.g., hemorrhage, carcinoma, electrolyte disorders, toxic megacolon with perforation).

   The lower sensitivity of combined serologic tests only modestly influences pretest and posttest probability in IBD but is very useful in distinguishing Crohn disease from UC. Serial measurements are not useful and do not correlate with disease activity; titers are stable over time.

Suggested Reading

Bossuyt X. Serologic markers in inflammatory bowel disease.
Clin Chem.
2006;52:171–181.

MALABSORPTION

   Definition

Malabsorption is defective nutrient absorption by the small intestine.

   Causes

   Inadequate mixing of food with bile salts and lipase (e.g., pyloroplasty, subtotal or total gastrectomy, gastrojejunostomy)

   Inadequate lipolysis due to lack of lipase (e.g., CF of the pancreas, chronic pancreatitis, cancer of the pancreas or ampulla of Vater, pancreatic fistula, vagotomy)

   Inadequate emulsification of fat due to lack of bile salts (e.g., obstructive jaundice, severe liver disease, bacterial overgrowth of the small intestine, disorders of the terminal ileum)

   Primary absorptive defect in the small bowel

   Inadequate absorptive surface due to extensive mucosal disease (e.g., regional enteritis, tumors, amyloid disease, scleroderma, irradiation)

   Biochemical dysfunction of mucosal cells (e.g., celiac sprue syndrome, severe starvation, or administration of drugs such as neomycin sulfate, colchicine, or PAS)