Atypical Posterior Nutcracker Syndrome in a 17-Year-Old Male Without Hematuria

Retro-aortic left renal vein (RLRV) is an anatomical variation, where the left renal vein (LRV) courses posterior to the aorta and anterior to the vertebrae before it eventually drains into the inferior vena cava (IVC). RLRV is a rare finding, with a prevalence of around 1%-2%, and only a small minority of RLRVs cause symptoms. RLRV symptoms occur secondary to compression of the LRV between the abdominal aorta and vertebrae, otherwise known as posterior nutcracker syndrome (PNCS). The most common symptoms of PNCS are hematuria and flank pain. We present a 17-year-old male, who came in with recurring left flank pain without hematuria, initially thought to be renal colic secondary to nephrolithiasis. On further investigations, an aberrant posterior renal vein was seen on CT suggestive of PNCS. The patient was treated successfully with RLRV vascular stent placement by interventional radiology. This case report adds to the limited number of PNCS cases observed in children and to the even rarer cases of PNCS without hematuria. This case also acts as a reminder for pediatricians to keep a wide scope of differentials in patients presenting with flank pain and provides an outline of both diagnostic and treatment modalities available for these patients.