Objective evaluation of the outcome of endopyelotomy using Whitaker's test and diuretic renography

To assess the role of Whitaker's test (WT) and 99mTc-diethylene triamine penta-acetic acid diuretic renography (DRG) in determining objectively the outcome of endopyelotomy, and to rationalize the frequency and timing of such evaluation after endopyelotomy.

Thirty-one patients (age > 15 years) were prospectively evaluated after percutaneous endopyelotomy. WT was performed at 4-6 weeks via the nephrostomy maintained for external drainage, 24 h after removing the splint. DRG was performed at 3, 6 and 12 months, and then annually.

WT performed 24 h after removing the splint diagnosed pelvic pressures in the unobstructed range (< 15 cmH2O) in 21 of the 24 patients were also evaluated with DRG at 3 months. An intra-pelvic pressure of > 15 cmH2O was correlated with a pattern of obstruction on DRG in all three units. Despite an unobstructed WT in 18 patients, categorization of DRG drainage showed disparity in six cases. All six renal units had a large pelvic area (> 15.0 cm2 in two and > 20.0 cm2 in four) and/or a poor renal function (separate glomerular filtration rate [GFR] of < or = 25 ml/min in four of the six units). The drainage pattern on DRG was unevaluable in two renal units as the function was poor (separate GFR < 15 ml/min). During the first year, the drainage pattern on DRG improved in four cases. When followed beyond one year, the drainage pattern deteriorated at 2 years in only one of 14 evaluated renal units with an initial unobstructed WT.

Using objective methods of evaluation, endopyelotomy was successful in relieving obstruction in 87% of cases. If inaccuracies in the interpretation of DRG, i.e. a large pelvic capacity and poor renal function, are accounted for, the results of WT as early as 24 h after removal of the splint correlated with DRG. Drainage patterns on DRG did not deteriorate during the first year. An early post-operative evaluation with WT or DRG, as appropriate, is thus sufficient evidence of the success of the procedure. Evaluations repeated during the first year after endopyelotomy may be unnecessary.