Intrarenal pressure (IRP) increases during ureteroscopy because of irrigation and scope manipulation and typically exceeds physiological levels. Elevated IRP can cause intrarenal backflow (IRB), whereby irrigation fluid and urine flow backwards into the kidney structures, increasing the risk of infectious complications and sepsis. The irrigation rate, outflow, and tool size are important variables that can affect IRP and the risk of IRB, but IRB thresholds vary based on papillary morphology indicating pressure compliance differences among patients. Recent research has shed light on IRP and the potential clinical consequences of elevated IRP. A greater focus on reducing IRP during ureteroscopy is recommended. PATIENT SUMMARY: When a small telescope is used to inspect the urinary tract up to the kidney, pressure inside the kidney increases because irrigation fluid is used. High pressure can cause fluid and urine to flow backwards into the kidney, which could lead to infection. The irrigation flow rate, drainage efficiency, size of the tools used, and the structure of a patient's kidney tissue can influence the pressure and the risk of backflow. Studies have shown the importance of controlling this pressure to reduce complications.