Retroperitoneoscopy in the horse: Anatomical study of the retroperitoneal perirenal space and description of a surgical approach

Background Surgical approaches to the kidneys and perirenal structures are uncommonly performed in horses and several complications have been described with the current procedures. Objective To describe the anatomy of the retroperitoneal perirenal space and investigate a retroperitoneal minimally invasive approach to access the kidney and perirenal structures in horses. Study design Descriptive, cadaveric study. Methods Anatomical description of the retroperitoneal space was performed on three equine cadavers and the surgical approach was developed based on these dissections. Ten cadaveric horses underwent a retroperitoneoscopy. Five horses were placed in a right lateral recumbency position to explore the left retroperitoneal space and five horses were placed in a standing position to explore both left and right sides. Anatomical landmarks, working space and access to the renal hilus and perirenal structures were evaluated. Results Dissections revealed that kidneys are surrounded by a renal fascia which delimits two spaces: a perirenal space between the kidney and the renal fascia, and a pararenal space between the renal fascia and psoas muscles or peritoneum. The retroperitoneoscopic portal was placed at the level of the dorsal aspect of the tuber coxae, 3 cm caudal to the last rib for the left side and 2 cm caudal to the last rib for the right side. Retroperitoneal access and working space were successfully established in all horses. The standing position allowed an easier dissection than lateral recumbency. Division of the perirenal fat allowed access to the kidney and adrenal glands as well as individualisation of renal vessels and ureter in the renal hilus. Main limitations Study of cadavers precluded appreciation of haemorrhage or use the pulsating vessels as landmarks. Conclusions This study provides a description of the retroperitoneal perirenal space and describes a new surgical approach to access kidneys and perirenal structures in horses.