A 32-year-old man comes to the office for a routine preemployment physical. He has been feeling well. Ten years ago, his father died suddenly at age 54. Blood pressure is 175/103 mm Hg in the right arm and 180/105 mm Hg in the left, and pulse is 82/min. BMI is 22.1 kg/m². The lungs are clear bilaterally and heart sounds are normal. Bilateral, nontender, upper abdominal masses are palpated on examination. Hemoglobin level is 15.2 g/dL and creatinine concentration is 0.8 mg/dL. Which of the following is the most appropriate next step in evaluating this patient's condition?

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11ec25c8_d2f2_b135_bc81_2d8f939e5fe1_MD0003_00 This patient with early-onset hypertension and bilateral upper abdominal masses likely has autosomal dominant polycystic kidney disease (ADPKD), which is the most common genetic cause of chronic kidney disease. Mutation of the PKD1 or PKD2 gene disrupts the function of polycystin proteins and leads to cystic degeneration of the renal parenchyma that begins early in life. Most patients are asymptomatic until age 30-40, when cysts have become large and numerous. Hypertension is a common early disease manifestation and is typically present before any significant decline in renal function. Other early disease findings can include hematuria, nephrolithiasis, flank pain, and urinary tract infections. Some patients have an elevated hemoglobin concentration due to increased erythropoietin production (possibly from local ischemia around the renal cysts). As cystic degeneration progresses with age, patients experience progressive renal dysfunction that eventually leads to end-stage renal disease. Extrarenal complications of ADPKD include cerebral aneurysms, hepatic or pancreatic cysts, cardiac valvular abnormalities (ie, mitral valve prolapse, aortic regurgitation), colonic diverticula, and ventral or inguinal hernias. The sudden death of this patient's father suggests rupture of a cerebral aneurysm in the setting of ADPKD. The diagnosis of ADPKD is based mainly on abdominal ultrasound or CT showing enlarged kidneys with numerous cysts. (Choice A) Elevated 24-hour urine cortisol excretion is seen in Cushing syndrome. Although Cushing syndrome can cause secondary hypertension, it is unlikely in this patient who is not overweight and is feeling well, without suggestive symptoms (eg, fatigue, irritability). Cushing syndrome may be due to adrenal tumors but is unlikely to cause palpable abdominal masses. (Choice C) Captopril-enhanced radionuclide renal scan is used occasionally to diagnose suspected renovascular disease or renal artery stenosis as a cause of refractory hypertension. However, these conditions are not associated with palpable renal enlargement. (Choice D) A high plasma aldosterone/renin ratio is seen in patients with primary aldosteronism (Conn syndrome), which is a common cause of secondary hypertension. However, it usually involves a unilateral adrenal adenoma that is not easily palpable; bilateral palpable adenomas would be highly unusual. (Choice E) Urinary excretion of metanephrines is increased in patients with pheochromocytoma. These patients usually have a paroxysmal elevation in blood pressure accompanied by headaches, palpitations, and/or diaphoresis. Educational objective: Most patients with autosomal dominant polycystic kidney disease are asymptomatic until age 30-40, when renal cysts become large and numerous. Bilateral upper abdominal masses are typically palpable on physical examination, and hypertension is an early disease manifestation that typically precedes a progressive decline in renal function. References: Autosomal dominant polycystic kidney disease. (http://www.ncbi.nlm.nih.gov/pubmed/17434405) Hypertension in autosomal dominant polycystic kidney disease. (http://www.ncbi.nlm.nih.gov/pubmed/20219618)

A 32-Year-Old Man Comes to the Office for a Routine