The aim of this study was to assess the effect of simple renal cysts on extracorporeal shockwave lithotripsy (SWL) in patients with calyceal renal calculi. Patients with simple renal cysts >35？mm and ipsilateral renal calculi <20？mm that were treated with SWL constituted group 1 (cyst + calculi). The control group included patients aged >40 years that had renal calculi <20？mm and no cysts that were treated with SWL. The 2 groups were compared according to age, gender, body mass index, calculi size, localization, and density, the calculi fragmentation rate, and the percentage of stone-free patients. Mean cyst size in group 1 was ？mm. Mean age in group 1 was years versus years in the control group; the difference was significant ( ). There were not any other significant differences between the 2 groups, except for the stone-free rate ( ), which was 33.3% in group 1 and 68.2% in the control group ( ). The presence of renal cysts in a patient with calculi requires that an individualized treatment plan be devised, so as to provide the patient with the most effective treatment. 1. Introduction Simple renal cysts are nonhereditary benign cystic disorders that occur in 50% of patients aged >50 years. The prevalence of the cysts increases with age and the cysts increase in size—on average—by 2.8？mm each year [1]. Although they are benign, they can be symptomatic due to their size. Some anatomical anomalies that hinder urine outflow, such as cystic renal diseases, ureteropelvic stenosis, urethral stenosis, and diverticulum of the calyx, may change the treatment modalities in patients with renal calculi. Currently, extracorporeal shock wave lithotripsy (SWL) is the most common mode of therapy for small renal calculi. Calculi are first disintegrated by shock waves, and then the fragments are spontaneously cleared from the urinary tract [2]. Additional therapy is required if the calculi cannot be spontaneously cleared from the urinary tract, which increases the cost of treatment and causes the renal parenchyma to be exposed to unnecessary shock waves; therefore, it is of the utmost importance to identify which patients will benefit from SWL therapy. Any factor that obstructs the normal outflow of urine may cause urinary calculi formation. SWL is not contraindicated in patients with renal cysts and calculi; however, renal cysts may limit the success of SWL because of the pressure on and distortion of the collecting system they cause [3]. It was reported that SWL may be performed in patients with cysts and calculi without an increase in complications [3]. To the best
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