A 64-year-old man is admitted with a 5-day history of lethargy and mild confusion. He is known to have alcoholic cirrhosis, nonbleeding esophageal varices, and ascites. There is no history of recent alcohol consumption, melena, or hematemesis. He has no abdominal pain and had not fallen. He takes a 2-g sodium diet and multivitamins daily. On examination, the patient is lethargic and confused to time and place but not date. Blood pressure is 110/70 mm Hg, pulse rate 87/min, temperature 36 °C (96.8 °F). Icteric sclerae and spiderangiomata are present. The neck veins are not distended. The lungs are clear, with decreased breath sounds at both bases. Cardiac examination reveals regular sinus rhythm and no gallop or rub. The abdomen is protuberant but nontender, with a shifting dullness; the liver is not palpable. The lower extremities have 1 + ankle edema. Asterixis is present, but the patient has no focal neurologic signs.
Laboratory studies:
Hemoglobin 11.5 g/dL
Hematocrit 32%
Leukocyte count 5400/µL
Platelet count 84,000/µL
Blood urea nitrogen 20 mg/dL
Serum creatinine 1.2 mg/dL
Serum sodium 114 meq/L
Serum potassium 4.1 meq/L
Serum chloride 80 meq/L
Serum bicarbonate 28 meq/L
Serum total protein 6.9 g/dL
Serum albumin 2.5 g/dL
Cholesterol 186 mg/dL
Serum osmolality 241 mosmol/kg H2O
Urine osmolality 200 mosmol/kg H2O
Spot urine sodium 10 meq/L
What is the cause of this patients hyponatremia?
A. Nonosmotic stimulation of antidiuretic hormone
B. Hepatorenal syndrome
C. Low-sodium diet
D. Reset osmostat
E. Pseudohyponatremia
