Effect of patient positioning on retrieval of cystoliths by percutaneous cystolithotomy in dogs

Percutaneous cystolithotomy (PCCL) is a minimally-invasive technique for removal of cystoliths. There is currently no information regarding optimum patient positioning during PCCL. The objective of this study was to assess whether patient positioning affected ease of cystolith retrieval via PCCL. PCCL was performed to retrieve artificial "cystoliths" in three canine cadavers weighing between 15-35kg, using a threaded cannula and a rigid 30^o 2.7mm cystoscope. "Cystolith" retrieval was performed by retrograde flushing and use of a flexible stone basket, with the dog in 10^o Trendelenburg, 10^o reverse Trendelenburg, or neutral position. The location of the "cystoliths", number retrieved during flushing, and total time for retrieval were recorded and compared between different positions. The mean total time for "cystolith" retrieval was 392 ±131s, with 162 ±20s for flushing and 221 ±123s for basket-retrieval. The mean number of "cystoliths" retrieved during flushing was 3 ±2. No significant differences were detected when comparing retrieval times between different positions. The predominant location of the "cystoliths" within the bladder varied depending on the position of the dog. In neutral, 93% were located adjacent to the ureteric openings, whereas in 10^o reverse Trendelenburg, 100% were located by the urethral orifice. In 10^o Trendelenburg, 60% "cystoliths" were located at the tip of the cannula. Cystolith retrieval during PCCL can be performed in either neutral, Trendelenburg or reverse Trendelenburg position. Changing the dog's position may be useful in cases where cystolith retrieval is challenging, to move the cystoliths and enable different techniques to be employed using the stone basket.