Bleeding is a serious complication of percutaneous nephrolithotomy (PCNL). A rare cause of gross hematuria is a calico-venous fistula. A clinical case of successful intraoperative diagnosis and treatment of calico-venous fistula during PCNL is presented in the article.
Description of a clinical case. A patient J., 53 years old, underwent examination and treatment at the Institute of Urology and Reproductive Health, FGAOU VO I.M. Sechenov First Moscow State Medical University with a diagnosis of staghorn stone of the right kidney, a stone of the left kidney, chronic right-side pyelonephritis. On June 15, 2021, mini-PCNL was performed for the staghorn stone of the right kidney. The procedure seemed to be unremarkable, but during intraoperative antegrade pyelography, the inflow of contrast agent from the lower calyxes into the posterior segmental vein of the right kidney was detected, which was managed by creating sufficient traction of the nephrostomy drainage.
Communication of the collecting and venous systems of the kidney is associated with a risk of both severe gross hematuria and urine flow into the venous bed. The urine flow into the bloodstream may result in hemodynamic disturbances, up to collapse followed by cardiac arrest. In order to prevent complications of PCNL it is necessary to analyze the kidney anatomy based on three-dimensional modeling of contrast- enhanced computed tomography.
A calicovenous fistula can be a source of risk of bleeding and severe complications. To minimize intraoperative damage to parenchymal structures, an analysis of three-dimensional modeling of a kidney in patients with staghorn calculus based on computed tomography is required, which allows rational planning of surgical tactics.

Keywords: calico- venous fistulae, surgical complications, percutaneous nephrolithotomy, urolithiasis