Nutcracker syndrome: A rare cause of left flank pain that can also manifest as unexplained pelvic pain.

Nutcracker syndrome (NCS) is symptomatic unilateral renal venous hypertension due to compression of the left renal vein between the superior mesenteric artery and aorta (anterior NCS) or between the aorta and spine (posterior NCS). The left ovarian or spermatic vein empties into the left renal vein and is an additional site of venostasis in about half the cases of NCS. The presenting symptom of NCS in about half the cases is atypical left flank pain suggesting a disorder of the lower ribs or thoracolumbar spinal junction, particularly as the pain worsens with standing and increased lumbar lordosis. NCS may be suggested by any combination of the following manifestations: hematuria, which is often only microscopic; orthostatic proteinuria; varicocele and infertility; dyspareunia and other gynecological symptoms; varicose veins in the pelvis, buttocks, or upper thighs; orthostatic hypotension and fatigue; and abdominal pain. Narrowing of the left renal vein on imaging studies is required but far from sufficient to establish the diagnosis. Several converging clinical findings and a marked pressure gradient between the left renal vein and inferior vena cava must be present also. Urological procedures and vascular surgery are being superseded by endovascular stenting with or without simultaneous treatment of the acquired gonadal vein insufficiency by embolization.