Visualization of the renal vein during pyelography after nephrostomy: a case report

INTRODUCTION: We present a case of pyelovenous backflow after nephrostomy. To the best of our knowledge, this is the first documented case of renal vein visualization after a nephrostomic placement. CASE PRESENTATION: A 55-year-old Caucasian man presented with symptoms of pyelonephritis with an obstructing ureteral stone. A nephrostomy was performed. During an injection of contrast agent in his left caliceal system, his left renal vein was visualized. A repeat pyelography with an injection contrast material at low pressure failed to show the same finding. This radiological finding is due to the occurrence of "pyelovenous backflow". CONCLUSION: This phenomenon is usually described in the setting of renal vein thrombosis, renal vein hypertension due to the "nutcracker phenomenon", or a reduced renal blood flow. Examination by microscopy shows the presence of tears in the fornix of the pelvic cavity that extend into the kidney parenchyma. Five types of renal backflow are described in the literature: pyelovenous, pyelolymphatic, pyelotubular, pyelointerstitia and pyelosinus. Injection of contrast material at high pressure may cause a fornix to flow into the tubules, or cause its rupture and flow into the venous system.