Diagnosis of Nutcracker Syndrome Using Positional Renal Vein Doppler Ultrasound: A Case Report

Nutcracker syndrome (NCS) is an underrecognized cause of intermittent hematuria and flank pain, resulting from compression of the left renal vein (LRV) between the aorta and superior mesenteric artery (SMA), causing venous hypertension. NCS can be missed on recumbent imaging, which cannot detect dynamic changes in renal blood flow associated with positional changes. We present a 37-year-old African-American male with over six months of recurrent macroscopic hematuria and activity-associated left flank pain. CT scan and cystoscopy did not reveal structural abnormalities in the genitourinary tract, renal vasculature, or blood flow. Urinalysis showed >1000/hpf, non-dysmorphic RBCs and subnephrotic-range proteinuria, preserved kidney function, and serologic evaluation for glomerulonephritis was unremarkable. In contrast to the unremarkable recumbent imaging, positional Doppler interrogation identified two left renal veins (LRVs), both of which showed increased compression in the standing position, supporting probable NCS. The patient was offered referral for invasive confirmation and possible intervention, but elected conservative measures, which included weight gain and avoiding symptom-exacerbating activities. In patients with unexplained intermittent hematuria and positional- or activity-associated flank pain, NCS should be considered. This case highlights the importance of dynamic positional Doppler ultrasound as a provocative, non-invasive test for suspected NCS when initial conventional imaging is unrevealing.