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Which blood tests may be useful in the evaluation of abdominal pain?
Patients who have experienced persistent vomiting and appear dehydrated may have electrolyte abnormalities.
In young infants, patients who will undergo surgery, or patients who are more severely ill, it may be more important to obtain blood studies to evaluate abdominal pain.
The benefit of the complete blood count (CBC) remains controversial. Although an elevated white blood cell count is common in appendicitis, this finding is neither sensitive nor specific. The absolute neutrophil count (ANC) and C-reactive protein test (CRP) may also be helpful in diagnosing appendicitis.
The erythrocyte sedimentation rate (ESR) may be helpful in the diagnosis of inflammatory bowel disease.
Measurement of liver aminotransferase values is useful in patients with scleral icterus or right-upper-quadrant tenderness.
An elevation of one or both of serum amylase and lipase in the appropriate clinical context supports the diagnosis of pancreatitis.
What other laboratory testing may be helpful in certain patients?
A urinalysis can be helpful in diagnosing urinary tract infections and renal calculi but can be misleading if pyuria is due to cervicitis or bladder/ureteral irritation from an adjacent inflamed appendix. A urine pregnancy test is indicated in postpubertal females with abdominal pain. Additionally, include diagnostic testing for gonorrhea and chlamydia infection when indicated.
Kwan KY, Nager AL: Diagnosing pediatric appendicitis: Usefulness of laboratory markers. Am J Emerg Med 2010;28:1009-1015.
Marin JR, Alpern ER: Abdominal pain in children. Emerg Med Clin North Am 2011;29(2):401-428.