Etiology	Diagnosis	Treatment
Heart failure	Clinical (e.g., jugular venous distention, edema), elevated B-type natriuretic peptide level, echocardiography, urinary sodium < 20 mEq per L	Diuretics, angiotensin-converting enzyme inhibitors, beta blockers
Kidney failure (acute or chronic)	Blood urea nitrogen to creatinine ratio, glomerular filtration rate, proteinuria, urinary sodium > 20 mEq per L Serum osmoles can be normal or high due to elevated blood urea nitrogen level To correct: tonicity = measured serum osmolality − (blood urea nitrogen ÷ 2.8)	Treat kidney failure; correct the underlying disease when possible
Liver failure/cirrhosis	Elevated liver function test results, ascites, elevated ammonia level, biopsy, urinary sodium < 20 mEq per L	Furosemide, spironolactone, transplant
Nephrotic syndrome	Urinary protein, urinary sodium < 20 mEq per L	Treat underlying cause