About NCS

NCS, or renal nutcracker syndrome, is one of the major abdominal vascular compression syndromes. NCS occurs when the left renal vein is compressed or stretched causing the vein to narrow and restrict blood flow. There are multiple causes of NCS. The most common cause after severe weight loss when the fat pad around the superior mesenteric artery is lost, causing the left renal vein to become compressed by the superior mesenteric artery and the abdominal aorta. However, NCS can also be caused by abnormal anatomy where the left renal vein is compressed by the duodenum or part of the pancreas. Regardless of the cause, when the left renal vein becomes narrowed, the pressure in the vein increases and nearby veins called collaterals may also swell leading to symptoms.

The symptoms of NCS include left flank and back pain, macroscopic or microscopic hematuria (blood in urine), proteinuria (protein in urine), pelvic pain, and dizziness upon standing. NCS can also cause pelvic congestion syndrome where veins in the pelvis become enlarged.

NCS can be difficult to diagnose due to its rarity and lack of recognition. NCS can be diagnosed through a CT scan, an ultrasound, a venogram, or an intravascular ultrasound. NCS is most commonly diagnosed through a CT scan when the narrowing of the left renal vein can be visible. The scan can also identify which structures are causing the compression. Ultrasound can also capture imaging of the narrowing, and a special kind of ultrasound called a doppler ultrasound can measure the blood flow to find if there is abnormal blood flow due to narrowing. A venogram is a slightly invasive diagnostic tool that can diagnose NCS. During this test, a small needle inserted through the neck or groin and then dye is injected to allow x-ray to capture images of the vein. Lastly, an IVUS, or intravascular ultrasound, can be used to capture images of the veins from the inside. The diagnosis can also be confirmed through urinalysis and blood work when protein or blood is found in the urine, and iron levels are low in the blood.

NCS can be treated with either weight gain or surgery. When the cause of NCS is compression from the superior mesenteric artery due to the loss of fat pad, it is possible that with weight gain, NCS can be reversed. However, surgery is most often the treatment as it is unlikely that the fat pad will be regained properly to reposition the superior mesenteric artery.  In cases of NCS not caused by the superior mesenteric artery, NCS will be unaffected by weight gain. There are multiple surgical options to treat NCS. The first option is an LRVT, or left renal vein transposition, where the left renal vein is moved slightly to move away from the cause of the compression. There is also a procedure called a hybrid auto transplant where the kidney is moved down slightly to move the left renal vein away from the compression. A common surgical option is known as an auto transplant where the left kidney is moved to the right side of the pelvis, leaving the patient with two kidneys on one side. The last option, which comes with the most risk by far, is a nephrectomy, where the left kidney is removed all together.