Hydronephrosis following ureteral reimplantation: when is it concerning?

Hydronephrosis without obstruction is common prior to ureteral reimplant, especially in patients with high-grade VUR. Consequently, when hydronephrosis is present post-operatively, it is unclear when it should be concerning. We evaluated the finding of hydronephrosis in children undergoing reimplantation and its evolution following surgery.

After obtaining IRB approval, we identified 938 children who underwent reimplantation at our institution from 1998 to 2006. Their pre- and post-operative US and clinical course were analyzed.

Hydronephrosis was observed in 24% pre-operatively and 21% post-operatively. 52% with pre-operative hydronephrosis had it post-operatively, while 12% without pre-operative hydronephrosis had it post-operatively. 71% of post-operative hydronephrosis resolved on average in 1.36 years. 19% didn't resolve and 0.1% had ureteral obstruction. Risk factors for post-operative hydronephrosis included increasing severity of VUR, and high degree of pre-operative hydronephrosis.

Hydronephrosis following ureteral reimplantation is not rare, and correlated to pre-operative evaluations. Post-operative hydronephrosis is frequently transient and benign, and usually resolves within the first 2 years. These patients do not require follow-up ultrasounds or further imaging, and can be followed clinically. Patients with high-grade VUR and hydronephrosis pre-operatively, however, are at risk for developing worsened hydronephrosis and should be followed with a 3-month post-operative ultrasound.