Which laboratory tests should be obtained in patients with acute abdominal pain?
Although laboratory tests are helpful in confirming the evolution of a disease process, they are frequently not helpful in localizing the cause of abdominal pain.
• Obtain a complete blood count. Elevation of the white blood cell count suggests inflammation; however, absence of leukocytosis may be misleading early in the course of disease. A low hematocrit with a normal mean corpuscular volume (MCV) suggests acute blood loss, whereas a low hematocrit with a low MCV suggests iron deficiency from chronic gastrointestinal (GI) blood loss or malabsorption.
• Amylase and lipase elevations may suggest pancreatitis, but amylase can come from various other sources, including salivary glands, lung, intestine, and ovary.
• Liver enzyme elevations may be suggestive of hepatobiliary causes of pain. Elevations of aspartate or alanine aminotransferase suggest hepatocyte injury. Alkaline phosphatase or γ-glutamine transferase elevations suggest canalicular or biliary injury. Total bilirubin elevations greater than 3 mg/dL suggest common bile duct obstruction or associated intrahepatic cholestasis, but if bilirubin elevation is predominantly unconjugated and not associated with liver enzyme elevations, it may be due to Gilbert’s disease.
• Evidence of pyuria on urinalysis suggests urinary tract infection but also may be seen in nephrolithiasis prostatitis or even pelvic appendicitis.
• Chemistry analysis can be helpful in the global assessment of patient health, hyperglycemia, acidosis, and electrolyte disturbances.
• Pregnancy tests (beta human chorionic gonadotropin) should be ordered for all premenopausal women.
• Stool examination for occult blood may be useful.
• Electrocardiography is performed for all patients with possible myocardial infarction or older than 50 years.
