A 21-year-old male presents to his physician after noticing that his urine had a "frothy" appearance. He also complains of easy fatigability and anorexia. His past medical history is significant only for an upper respiratory infection several weeks ago. Physical examination reveals symmetric pitting edema of the ankles. Which of the following is most likely decreased in this patient?

Question

A 21-year-old male presents to his physician after noticing that his urine had a "frothy" appearance.  He also complains of easy fatigability and anorexia.  His past medical history is significant only for an upper respiratory infection several weeks ago.  Physical examination reveals symmetric pitting edema of the ankles.  Which of the following is most likely decreased in this patient?

Quizplus · Accepted Answer

Frothy, foamy urine may be caused by proteinuria or bile salts in the urine. This patient's history of a recent upper respiratory infection and ankle edema on physical exam suggest a diagnosis of nephrotic syndrome with associated low serum albumin. Hypoalbuminemia lowers the plasma oncotic pressure and causes interstitial edema formation due to net plasma filtration. Minimal change disease (MCD) is the most common cause of nephrosis in children, and can occur in adults as well. (Choice A) A decrease in capillary hydrostatic pressure would tend to decrease net plasma filtration and interstitial edema formation. (Choice B) This patient's ankle edema is the result of a transudate of plasma into the interstitial tissues of the ankle. We would therefore expect an increase in the steady state interstitial fluid pressure in the ankles. (Choice D) While a primary decrease in lymphatic drainage can cause interstitial edema, the rate of lymphatic drainage would be increased in this particular patient because of the accumulation of ankle interstitial fluid. (Choice E) In nephrotic syndrome, the plasma oncotic pressure is decreased, which causes net plasma filtration into the interstitium, thus decreasing the effective circulating intravascular volume. This reduction of the intravascular volume stimulates a compensatory increase in the activity of the renin-angiotensin-aldosterone system. Patients with nephrotic syndrome tend to have elevated circulating aldosterone levels. Educational Objective: Frothy or foamy urine may be caused by proteinuria. Heavy proteinuria, as in nephrotic syndrome, can cause regional or generalized interstitial edema because the decrease in serum albumin and total protein concentrations lowers the plasma oncotic pressure and increases net plasma filtration in capillary beds.

A 21-Year-Old Male Presents to His Physician After Noticing That