Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (150 page)

   Dermatitis herpetiformis

   Intestinal lymphangiectasia

   Allergy

   Idiopathic

OTHER GASTROINTESTINAL CONDITIONS ASSOCIATED WITH CHRONIC DIARRHEA

DIVERTICULOSIS, COLON

   Laboratory Findings

Core laboratory
: Hypochromic microcytic anemia, increased WBCs. Increased ESR. Positive occult blood.

ENTEROCOLITIS, NECROTIZING, IN INFANCY

   Definition

Syndrome of acute intestinal necrosis of unknown cause. It is especially associated with prematurity and exchange transfusions.

   Laboratory Findings

There may be oliguria, neutropenia, and anemia. Persistent metabolic acidosis, severe hyponatremia, and DIC are a common triad in infants. Bloody stools feature no characteristic organisms; significant organisms are often found by frequent repeated cultures of blood, urine, and stool.

INFLAMMATORY BOWEL DISEASE

   Definition

IBD refers to a chronic relapsing spectrum of disorders of unknown cause with destructive mucosal immune reaction in a genetically susceptible host. It is caused by an aberrant immune response and loss of tolerance to normal intestinal flora, leading to chronic inflammation of the gut.

REGIONAL ENTERITIS (CROHN DISEASE)

   Definition

Systemic inflammatory disease with predominantly GI tract involvement. There are no pathognomonic findings for Crohn disease or to distinguish it from ulcerative colitis.

   Laboratory Findings

Histology
: Endoscopic biopsy may show granulomas in >60% of cases of Crohn disease but in only 6% of cases of UC.

Serology
: Atypical perinuclear-staining antineutrophil cytoplasmic antibodies (P-ANCA) are found in <15% of cases of Crohn disease but in ≤70% of ulcerative colitis patients. Anti-
S. cerevisiae
(baker’s or brewers’ yeast) antibodies (ASCA) are found in approximately 60% of Crohn disease cases but in only approximately 10% of cases in ulcerative colitis.

Lactoferrin and calprotectin high sensitivity and specificity distinguishing between IBD and noninflammatory IBS.

Hematology
: Increased WBC, ESR, CRP, and other acute-phase reactants correlate with disease activity. Mild increase of WBC indicates activity, but a marked increase suggests suppuration (e.g., abscess). ESR tends to be higher in disease of the colon than of the ileum. Anemia due to iron deficiency or vitamin B
₁₂
or folate deficiency or chronic disease.

Core laboratory
: Decreased serum albumin, increased γ-globulins. Hyperchloremic metabolic acidosis, dehydration, decreased sodium, potassium, magnesium. Mild liver function test changes due to pericholangitis (especially increased serum ALP). Laboratory changes due to complications or sequelae (e.g., malabsorption, perforation and fistula formation, abscess formation, arthritis, sclerosing cholangitis, iritis, uveitis).

ULCERATIVE COLITIS, CHRONIC NONSPECIFIC

   Definition