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Sixteen male Yucatan minipigs underwent balloon dilation of the right ureterovesical junction (UVJ) and lower ureter to twice its normal caliber. With the bladder open, bilateral upper tract dynamics measurements under different perfusion rates (0.5, 2, and 4 ml/min) were recorded predilation, immediately after dilation, and 1, 2, 3, 4, and 6 weeks after dilation. Immediate and late antegrade nephrostograms, suprapubic cystograms, and right antegrade nephrostograms (oblique view) were taken. In the chronic experiment, no difference in renal pelvic pressure (Ppvs) was detectable between the control and dilated sides immediately after dilation. Only at 4 ml/min was there a statistically significant increase in the Ppvs of the dilated ureter 1 week after dilation when compared with the controls. At 2 weeks, this obstructive change had disappeared. At 3, 4, and 6 weeks, Ppvs of the dilated ureter declined progressively in comparison with the control side, but the difference was not statistically significant. At 6 weeks, Ppvs of the dilated ureter decreased significantly compared with predilation readings only at 4 ml/min. Immediate antegrade radiologic evaluation revealed that 69% of the experimental animals had no extravasation, while 31% showed variable degrees of extravasation, which disappeared completely on late antegrade nephrostograms (6 weeks). Grade 2 reflux occurred in 33% of the experimental animals at 1 week and had disappeared at 6 weeks. Histologic examinations at 1, 2, and 3 weeks revealed a nonhomogeneous pattern of ureteral damage, ranging from total rupture to much less dramatic injury.(ABSTRACT TRUNCATED AT 250 WORDS)

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Balloon dilation of the right ureterovesical junction (UVJ) and distal ureter to three times its normal caliber was performed in 12 pigs. A right double-J (D-J) stent was inserted after dilation in 6 pigs. Bilateral upper tract dynamics with different perfusion rates (0.5, 2 and 4 ml. per minute) were recorded before dilation, immediately after dilation, and then 4 and 7 weeks after dilation. Immediate and late antegrade nephrostograms as well as suprapubic cystograms were taken. Grade 3 reflux occurred in 100% of animals at 7 weeks on the dilated, stented ureter and no reflux on the dilated, nonstented ureter. At 7 weeks on the dilated, stented side, significant growth (> 100,000, colonies) of Pseudomonas species was noted in all animals. Creatinine clearance was significantly reduced on the dilated, stented side when compared to the dilated, nonstented side at 7 weeks. Histologic examination of the dilated, stented and dilated, nonstented ureters at 4 weeks revealed a segmental muscular defect with muscular regeneration starting from the edge of the defect, particularly in the innermost region. At 7 weeks, there was a more advanced, but similar, pattern of muscular regeneration in both groups. However, at 7 weeks, metaplastic changes of the ureter and chronic pyelonephritis were evident on the dilated, stented ureter. Electron microscopy showed that myofibroblasts played a major role in the healing process with new muscle formation. At 4 weeks, no significant morphologic difference was found between the dilated, stented and dilated, nonstented ureters. At 7 weeks, however, it appeared that the ureteric stent resulted in damage and deterioration of renal function without affecting muscular regeneration of the ureter. We conclude that the changes observed could be entirely due to the infection associated with the stent rather the stent itself.

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Background: Prenatally diagnosed, hydronehprosis does not mean presence of decompensated obstruction and spontaneously improvement or resolution can occur postnatally. If obstruction persists, the split renal function (SRF) of the diseased kidney will dramatically decrease, and surgical intervention will be necessary.Objective: Evaluation of outcome of pyeloplasty in children with ureteropelvic junction obstruction (UPJO) in renal unit with split function less than 20% and to asses renal function recoverability.Patients and Methods: Cohort (historical and concurrent) study included 88 patients with UPJO with split renal function (SRF) < 20%. Preoperative patient was investigated by abdominopelvic ultrasound, magnetic resonance urography (MRU) or computerized tomography and renal isotope scan. Split renal function and T 1/2 .Preoperative and postoperative were compared. Results of the procedure were evaluated by clinical examination, abdomino-pelvic ultrasound after one month. Urine analysis with culture and sensitivity and renal isotope scan after 6 months.Results: Our study included 88 patients divided into two groups according to SRF (group 1, SRF >20% and group 2, SRF < 20%). Mean preoperative SRF was 31.34 ± 15.27%in all cases, 41.79 ± 7.03% in group 1 and 13.06 ± 4.90% in group 2, which increased postoperatively to 38.35 ± 15.61%, 46.86 ± 8.43% and 20.81 ± 7.67% respectively and this improvement was highly significant. Group 2 included 9 patient with SRF < 10%, mean preoperative SRF was 6.21 ± 2.26% which increased preoperatively to 15.04 ± 7.09% , also in the remaining 23 cases, mean preoperative SRF was 15.74 ± 2.30% increased postoperatively to 23.07 ± 6.75% . Conclusion:Poorly functioning renal unit with SRF < 20%, can show functional improvement and recoverability, so in these renal units, we should not have to rush to nephrectomy and instead of that we can proceed to pyeloplasty.

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