Suspected infection, anemia, or inflammation

Elevated WBC suggests infection; low Hb suggests chronic blood loss or malabsorption

Suspected inflammation or infection

Elevated in infection, IBD, appendicitis. Normal CRP helps exclude organic disease

Chronic inflammation assessment

Elevated in IBD, chronic infection, malignancy

RUQ pain, jaundice, hepatomegaly

Elevated in hepatitis, cholecystitis, biliary disease

Suspected pancreatitis

Lipase >3x upper limit strongly suggests pancreatitis

Vomiting, diarrhea, dehydration

Derangements guide fluid resuscitation

Altered consciousness, DKA suspicion

Elevated in DKA; low in metabolic crisis

Chronic abdominal pain, diarrhea, growth failure

Positive suggests celiac disease; confirm with biopsy if equivocal

Dysuria, frequency, suprapubic pain

Positive suggests UTI; hematuria may indicate nephrolithiasis

Positive urinalysis or suspected UTI

Confirms UTI and guides antibiotic selection

Suspected GI bleeding, IBD, polyps

Positive suggests mucosal disease - needs further investigation

Infectious diarrhea, bloody stool

Identifies bacterial, viral, or parasitic causes

Differentiating IBD from functional pain

Elevated (>200) strongly suggests intestinal inflammation (IBD)

Epigastric pain, family history of H. pylori

Positive indicates active H. pylori infection

H. pylori testing (children ≥3 years)

Sensitivity 95%, Specificity 95% for active H. pylori. False positives in children <6 years

Suspected obstruction, constipation, foreign body

Air-fluid levels suggest obstruction; free air suggests perforation

First-line imaging for undifferentiated abdominal pain

Can identify appendicitis, intussusception, pyloric stenosis, ovarian pathology

Equivocal ultrasound, trauma, suspected abscess

Higher radiation - use when US insufficient. Good for appendicitis, abscess, trauma