The vesicoureteral reflux (VUR) after the insertion of a JJ stent is a pathological entity characterized by the impossibility of the vesicoureteric junction (VUJ) to exhibit its sphincterian functioning that allows the unidirectional flow of urine from the ureter to the bladder. This happens as long as the catheter is in place, and after its suppression due to traumatization of the ureterovesical junction, which loses its tonicity and ability to ensure urinary unidirectional flow. Reflux acute pyelonephritis is the acute inflammation of the renal tract and parenchyma resulting from stagnation of infected urine for long periods of time due to vesicoureteral reflux. We have noted multiple cases which, after the insertion of a JJ stent, presented reflux acute pyelonephritis due VUR, we considered the causes favoring these aspects. We focused on the frequency of reflux acute pyelonephritis and identified factors that could be used to advise patients with JJ stents.