A 48-year-old man has noted increased thirst and urine output, even getting him up at night, along with mild back pain. On physical examination he is afebrile, but his blood pressure is 160/100 mm Hg. There is right costovertebral angle tenderness. Family history reveals that his father died in his early 50's of "kidney" disease. An intravenous pyelogram (IVP) shows no hydronephrosis or filling defects, but both his kidneys are markedly enlarged.

Questions:

1. What do the historical findings suggest?

There is a possible genetic problem.

2. What laboratory tests would be useful?

Tests for renal function: serum creatinine and BUN, creatinine clearance.

3. If you were to give the patient anti-diuretic hormone (ADH) or if he didn't drink any water for 12 hours, and then the urinalysis was repeated and the specific gravity was still 1.010, what would this suggest?

The kidneys have lost their concentrating ability--renal failure--though this is still a stage at which some function remains, so he has polyuria and nocturia. Rupture or bleeding into a cyst can cause pain.

4. Why do you think the kidneys are enlarged?

Adult polycystic kidney disease leads to massive enlargement of the kidneys with multiple cysts. The liver may also be cystic. These people have an increased incidence of intracranial aneurysms.