Electrolyte Disorders USMLE Step 1 Practice Question
A 62-year-old man with COPD on no diuretics presents with acute confusion and generalized seizures. Vital signs: BP 128/82 mmHg, HR 92/min, RR 18/min, temp 37.2°C, SpO2 96%. Physical examination reveals euvolemia without edema. Serum sodium is 118 mEq/L with normal renal function (creatinine 0.9 mg/dL). Urine osmolality is 450 mOsm/kg and urine sodium is 60 mEq/L. Which of the following is the most likely diagnosis?
Answer choices
- ANephrotic syndrome
- BCentral diabetes insipidus
- CPrimary polydipsia
- DSyndrome of inappropriate antidiuretic hormone secretionCorrect answer
- EAdrenal insufficiency
- FHypothyroidism with myxedema coma
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