Concentration of antibiotics in simple renal cysts.

Patients with infected renal cysts are known to respond poorly to antibiotic therapy. We evaluated the serum, cyst fluid and urine levels of 3 antibiotics in 4 patients with simple renal cysts. Despite excellent urine and serum concentrations gentamicin was detected in the cyst of only 1 of the 3 patients studied. Neither sulfamethoxazole nor trimethoprim was detected in the cyst of 1 patient despite adequate plasma levels. These data help explain the poor medical response of such patients and support the concept of early surgical intervention.