Egilmez et al. ing a perirenal hematoma or renal hemorrhage. Patients with bleeding tendencies, including those who were taking anticoagulants, did not undergo sclerotherapy until their clotting parameters were brought within normal limits, when possible. A pigtail catheter 5.4-Fr (PBN Medicals, Denmark) was inserted with using a trocar-catheter system under CT guidance (Figs. 1A, B). The cyst fluid was aspirated as completely as possible and it was sent to the laboratory for cytologic and biochemical examination. The total amount of the aspirated fluid was measured to record the cyst’s volume. The cyst was then filled with a half-and- half mixture of water-soluble contrast medium (Telebrix 35 [350 mg iodine/ml], Guerbet Laboratories, Aulnay- sous-Bois, France) with normal saline. For patients who were undergoing sclerotherapy, contrast medium was instilled into the cyst to ensure that there was no communi- cation with the pelvicalyceal collecting system, to exclude any leakage from the puncture site into the retroperitoneal cavity and to determine the presence of extravasation (Fig. 1C). The patients were then randomized into the ethanol and hypertonic saline groups; 95% ethanol or 20% hypertonic saline, respectively, which corresponded to 75% of the aspiration volume, was injected through the catheter into the cyst and this was left in place for 20 minutes. However, for a large cyst greater than 400 ml, the amount of sclerosants was limited to 100 ml to avoid A B C D Fig. 1. Representative CT images of a 53-year-old male patient with a simple renal cyst. A. The simple renal cyst before aspiration. B. A 5.4-Fr pigtail catheter was inserted into the cyst. C. Contrast medium is instilled into the cyst to ensure that there was no communication with the pelvicalyceal collecting system, to exclude any leakage from the puncture site into the retroperitoneal cavity and to determine the presence of extravasation. D. The cyst disappeared after successful ethanol sclerotherapy. 514 Korean J Radiol 8(6), December 2007