Health Questions and Answers

Question: Which are the most useful preliminary laboratory tests to order?

Answer: A complete blood count with differential WBC count and urinalysis generally are recommended. The initial hematocrit helps to define antecedent anemia, and serial measurements may reveal ongoing hemorrhage. An elevated WBC count suggests significant pathology but is nonspecific. Elevated urinary specific gravity reflects dehydration, and an increased urinary bilirubin in the absence of urobilinogen points toward total obstruction of the common bile duct. Pyuria, hematuria, and a positive dipstick for glucose and ketones may reveal nonsurgical causes for abdominal pain. For patients with epigastric or right upper quadrant pain, lipase and liver function studies are advised. Amylase may be added but is nonspecific. In addition to indicating pancreatitis, amylase may be elevated with biliary obstruction, cholecystitis, posterior perforation of a peptic ulcer, bowel obstruction or inflammation, and salpingitis. Any woman with childbearing capability should receive a pregnancy test. Serum electrolytes, glucose, blood urea nitrogen, and creatinine are indicated if there is clinical hypovolemia resulting from copious vomiting or diarrhea, tense abdominal distention, or delay of several days after onset of symptoms and especially if the patient is likely to require emergency general anesthesia.

  • An ECG should be obtained if the patient is older than age 40.

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