Pseudoaneurysm (PA) is a false lumen that arises from a defect in the layers of the arterial wall, around which a hematoma forms, and reactive fibrosis leads to the development of a saccular structure connected to the arterial lumen by a neck; renal arteriovenous fistula results from injury to the wall of the main or segmental renal arteries, and the injury may be traumatic (most commonly penetrating), iatrogenic, or sometimes secondary to an inflammatory or neoplastic process. The main iatrogenic causes include percutaneous nephrolithotomy (PCNL), percutaneous renal biopsy, percutaneous nephrostomy, and renal resection; diagnosis is primarily based on color Doppler ultrasound, contrast-enhanced computed tomographic angiography (CTA), or angiography, and treatment options depend on the site of injury, with endovascular embolization being the first-line therapy. The aim of this study is to identify, within a multicenter retrospective study, the incidence and risk factors for the development of renal artery pseudoaneurysm in patients following percutaneous nephrolithotomy, and to determine the clinical features and effectiveness of treatment methods. The objectives of the study are: to assess the incidence of this complication; to evaluate the clinical presentation and severity of the complication; to determine the nature and effectiveness of treatment methods; to assess treatment outcomes; to identify risk factors for the development of the complication; and to develop a risk assessment scale for pseudoaneurysm after PCNL based on the identified risk factors. The study type and design is a retrospective multicenter cohort study. Inclusion criteria are: age ≥18 years, patients who underwent PCNL, pseudoaneurysm confirmed by CTA or angiography, and a follow-up period of at least 30 days after the procedure. Exclusion criteria are: known pre-existing vascular anomalies or abnormalities in the kidney, and absence of key data required for analysis (incomplete medical records). Outcomes assessed include: development of renal artery branch pseudoaneurysm after PCNL; time to detection of PA after PCNL; development of bleeding from the pseudoaneurysm; effectiveness of conservative methods; effectiveness of endovascular intervention; and effectiveness of renal exploration and nephrectomy. Materials and methods: the study will analyze medical record data from patients who underwent PCNL and developed the complication of renal artery pseudoaneurysm; data will be provided by different centers that perform such procedures. Sample size calculation was performed accounting for clustering of data across centers: with an expected embolization rate of 80%, precision of ±10%, confidence level of 95%, intraclass correlation coefficient of 0.03, and an average cluster size of 8 patients, the design effect was 1.21, and the adjusted sample size is 75 patients with pseudoaneurysm.
