An Enigmatic Route to the Contralateral Pelvicalyceal System on Antegrade Pyelogram.

Introduction: The authors present the rare yet enigmatic phenomenon of 'pyelo-renal' backflow.

Case Presentation: An eight-month-old boy with multiple congenital anomalies underwent left Anderson-Hynes Pyeloplasty for pelvi-ureteric junction obstruction. Antegrade dye-study done through the nephrostomy revealed obstruction at the level of the pelvi-ureteric junction, yet the contrast was visualized in the pelvis of contralateral kidney and urinary bladder (pyelo-venous backflow) masquerading as vesicoureteric reflux. The phenomenon of 'pyelo-renal' backflow along with pyelo-tubular, pyelo-interstitial, pyelo-sinusal and pyelo-lymphatic backflow have been described and the respective mechanisms discussed.

Conclusion: The phenomenon is known to happen in the presence of obstruction to outflow from renal pelvis thereby creating a closed compartment. Injection of contrast at a pressure above the critical limit may result in forniceal tears and back-flow of contrast into the renal tubules and beyond.