Review Question - QID 214442

A 27-year-old man presents to the clinic for a well-check. The patient denies any concerns with his health and has no significant past medical history. He had an appendectomy 5 years ago but has no other surgeries. He denies any fever, chest pain, shortness of breath, weight changes, fatigue, or recent illness. The patient reports eating fast food about 3-4 times a week but has otherwise a healthy diet consisting of carbohydrates, protein, and vegetables. He drinks 4-5 times a week, about 1-2 beers every time. He denies any drug or cigarette use. He works as a construction manager and enjoys his job. A physical examination was unremarkable except for the findings in Figure A. Basic laboratory testing is shown below.

Serum:
Na+: 137 mEq/L
Cl-: 101 mEq/L
K+: 3.7 mEq/L
HCO3-: 23 mEq/L
Urea nitrogen: 10 mg/dL
Glucose: 87 mg/dL
Creatinine: 0.8 mg/dL
Alkaline phosphatase: 34 U/L
Aspartate aminotransferase (AST, GOT): 8 U/L
Alanine aminotransferase (ALT, GPT): 10 U/L
Total bilirubin: 3.4 mg/dL
Direct bilirubin 2.9 mg/dL

What is the most likely explanation for this patient’s findings?