Nutcracker syndrome
The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein (LRV) between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist.[1][2] The name derives from the fact that, in the sagittal plane and/or transverse plane, the SMA and AA (with some imagination) appear to be a nutcracker crushing a nut (the renal vein).
Nutcracker syndrome
Nutcracker phenomenon, renal vein entrapment syndrome, mesoaortic compression of the left renal vein
There is a wide spectrum of clinical presentations and diagnostic criteria are not well defined, which frequently results in delayed or incorrect diagnosis.[1] The first clinical report of Nutcracker phenomenon appeared in 1950.[3]
This condition is not to be confused with superior mesenteric artery syndrome, which is the compression of the third portion of the duodenum by the SMA and the AA.
Signs and symptoms[edit]
The signs and symptoms of NCS are all derived from the outflow obstruction of the left renal vein. The compression causes renal vein hypertension, leading to hematuria (which can lead to anemia)[4] and abdominal pain (classically left flank or pelvic pain).[5] The abdominal pain may improve or worsen depending on positioning.[5] Patients may also have orthostatic proteinuria, or the presence of protein in their urine depending on how they sit or stand.[6]
Since the left gonadal vein drains via the left renal vein, it can also result in left testicular pain[7] in men or left lower quadrant pain in women, especially during intercourse and during menstruation.[8] Occasionally, the gonadal vein swelling may lead to ovarian vein syndrome in women. Nausea and vomiting can result due to compression of the splanchnic veins.[7] An unusual manifestation of NCS includes varicocele formation and varicose veins in the lower limbs.[9] Another clinical study has shown that nutcracker syndrome is a frequent finding in varicocele-affected patients and possibly, nutcracker syndrome should be routinely excluded as a possible cause of varicocele and pelvic congestion.[10] In women, the hypertension in the left gonadal vein can also cause increased pain during menses.[10]
Cause[edit]
In normal anatomy, the LRV travels between the SMA and the AA.[8] Occasionally, the LRV travels behind the AA and in front of the spinal column. NCS is divided based on how the LRV travels, with anterior NCS being entrapment by the SMA and AA and posterior NCS being compression by the AA and spinal column.[8] NCS can also be due to other causes such as compression by pancreatic cancer, retroperitoneal tumors, and abdominal aortic aneurysms.[8] Although other subtypes exist, these causes are more uncommon in comparison to entrapment by the SMA and the AA.[8] Patients with NCS have a tendency to have a tall and lean stature, as this can lead to a narrower gap between the SMA and the AA for the LRV. [11]
Compression of the left renal vein (marked by the arrow) between the superior mesenteric artery (above) and the aorta (below) due to nutcracker syndrome
A nutcracker. The legs of this nutcracker, with some imagination, could represent the two arteries, squeezing whatever is stuck between them.
