Diagnostic aspects, functional significance and therapy of simple renal cysts. A clinical, radiologic and experimental study.

Simple renal cysts and renal cell carcinomas constitute the majority of the renal masses disclosed by radiologic methods. The reliability of radiologic diagnosis was studied in patients with different renal mass lesions. Based on the experiences from the study, ultrasonography is recommended when a renal mass is discovered at urography. Computerized tomography and rarely angiography and percutaneous puncture for cytologic examination are necessary when all criteria of a simple renal cyst have not been fulfilled. Forty-one patients with renal cell carcinoma and additional renal masses in the same or contralateral kidney were studied. In 3 patients the radiologic methods were insufficient to establish a definite diagnosis of the additional renal mass occurring in the kidney contra-lateral to the renal cell carcinoma. Only explorative surgery established the true diagnosis. A method for estimating single kidney glomerular filtration rate by gamma camera renography using 99mTc-DTPA was studied. The accuracy and reproducibility was satisfactory when compared to the 51Cr-EDTA clearance reference method. The functional consequences of simple renal cysts and percutaneous puncture were studied by gamma camera renography before as well as after puncture and evacuation of the cysts. Signs of obstruction of the renal outflow were rarely seen. No other effect on renal function was found and percutaneous puncture with evacuation of the cysts did not improve renal function significantly. The therapeutic efficacy of percutaneous puncture and instillation of bismuth-phosphate was compared to percutaneous puncture alone and to the natural course of simple renal cysts. After 24 months there were no significant difference in size between cysts that were only punctured and those that had no intervention. The cysts that were treated with bismuth-phosphate disappeared or diminished with few exceptions. The effects of bismuth-phosphate on the renal parenchyma and renal outflow tract were investigated by microangiography and histopathology in an experimental study. A zone of connective tissue around the deposited bismuth-phosphate was seen and no effects on glomeruli or renal vessels were disclosed. It is concluded that the radiologic diagnosis of simple renal cysts is definite when all diagnostic criteria are fulfilled by ultrasonography or computerized tomography. Simple renal cysts have no effect on renal function. Therapeutic interventions because of simple renal cysts are not indicated in patients without outflow obstruction.