Pathophysiology of Vesicoureteral Reflux

Vesicoureteral reflux is the abnormal backflow of urine from the bladder to the ureter and/or kidney. When the affected individual voids, the urinary bladder contracts. The urine is supposed to leave through the urethra, but if the vesicoureteral junction is abnormal some urine will be forced back up into the ureter. How bad is the junction? How much urine goes up rather than down? These are the questions that determine the grading of reflux, established by the International Reflux Grading system.