Detection of crossing vessels at the ureteropelvic junction with fast MRI

Minimally invasive surgery is an alternative to open surgery in the treatment of ureteropelvic junction obstruction (UPJO) in selected pediatric patients. Anomalous crossing vessels represent a contraindication to endopyelotomy and may also interfere with the videosurgical pyeloplasty. We investigated the usefulness of magnetic resonance imaging (MRI) without contrast in the preoperative evaluation of anomalous crossing vessels in children.

From January 1999 to December 1999, 14 patients with diagnosis of hydronephrosis were prospectively evaluated with the aim of accurately plan the operative approach. The children underwent MRI study with HASTE sequences, heavily T2 weighted. Diagnosis was made without IV contrast material. No sedation was used.

4 out of the 14 patients studied were diagnosed as having anomalous crossing vessels at the ureteropelvic junction. They underwent open dismembered pyeloplasty and the diagnosis was confirmed at the operation. There was 1 false negative.

The fast T2 weighted MRI allows a non invasive preoperative assessment of crossing vessels at the UPJO which is of paramount importance in the choice of the appropriate surgical approach. Nevertheless, the high cost and the low sensitivity (80%, 4/5) make this technique still not routinely applicable in the preoperative work-up of children with UPJO.