Postoperative renal and urinary complications are common and clinically significant in cardiac surgical patients, particularly those undergoing cardiopulmonary bypass. This chapter provides a comprehensive overview of the incidence, mechanisms, and management of acute kidney injury (AKI), catheter-associated urinary tract infections (CAUTI), and hematuria in the postoperative cardiac setting. It explores the multifactorial pathogenesis of cardiac surgery–associated AKI (CSA-AKI), including ischemia-reperfusion injury, inflammation, nephrotoxic exposure, and genetic susceptibility. Strategies for prevention and management are detailed across the perioperative timeline, with evidence-based guidance on fluid therapy, hemodynamic targets, nephroprotective pharmacologic agents, and enhanced recovery protocols. Furthermore, the chapter highlights the role of proper catheter use and early recognition of urological complications to minimize morbidity and healthcare costs. By integrating current guidelines and emerging data, this chapter aims to improve renal outcomes and overall patient care following cardiac surgery.