Role of MR renography in the evaluation of acute upper urinary tract obstruction

Purpose

To present the role of MR renography in diagnosis of upper urinary tract obstruction (UTO) with evaluation of diagnostic criteria for acute obstruction.

Material and methods

Thirty consecutive patients with obstructive anuria were included in our study. For identification of the cause of obstruction, all patients were subjected to plain abdominal X-ray (KUB), gray scale ultrasonography, non-contrast CT for the abdomen and pelvis (NCCT). There were five patients with bilateral obstruction and 25 with obstructed solitary functioning kidney, so the study included 35 units. All patients were subjected to radioisotope diuretic renography and magnetic resonance renography (MRR) before relief of obstruction and 3 days after drainage. Of the 30 patients included, 20 were men and 10 women.

Results

Among our patients the mean serum creatinine at time of presentation was 7 ± 4.5 mg/dl (range 2.4–12) and GFR ranged from 33 to 48 ml/min (mean ± SD; 38 ± 4.2). All the renal units have hydronephrosis. The mean pre drainage SI values 133 ± 22 (range 120–180). The mean time to peak (TP) for each unit was 171.6 ± 78 s and at isotope renography it was 320 ± 66 s. There was good corticomedullary differentiation (CMD) in 31 units and the remaining 4 showed loss of CMD differentiation. The CMD crossing time was 163.6 ± 70.4 s. Post kidney drainage the parenchymal SI was increased in 30 units, in 3 units there was drop and no change in 2 (r = 0.29). There is relative reduction in the time to peak, it becomes 67 ± 79 s after drainage (r = 0.76).

Conclusion

MR renography is a clinically valuable technique that provides diagnostic criteria to diagnose the acute urinary obstruction and allows follow up of renal function.