Your kidneys are two bean-shaped organs that regulate important functions in your body, such as:

  • removing waste from your blood
  • balancing bodily fluids
  • forming urine

Each kidney typically has one vein that carries blood filtered by the kidney into the circulatory system. These are called the renal veins. Usually there’s one on the right and one on the left. However, there can be variations.

In nutcracker syndrome, symptoms are most often caused when the left renal vein coming from the left kidney becomes compressed and blood can’t flow normally through it. Instead, blood flows backwards into other veins and causes them to swell. This can also increase pressure in your kidney and cause symptoms such as blood in your urine and pain.

There are two main types of nutcracker syndrome: anterior and posterior. There are also several subtypes. Some experts put these subtypes into a third category known as “mixed.”

In anterior nutcracker syndrome, the left renal vein is compressed between the aorta and another abdominal artery. This is the most common type of nutcracker syndrome.

In posterior nutcracker syndrome, the left renal vein is typically compressed between the aorta and the spine. In the mixed type, there’s a wide range of blood vessel changes that can cause symptoms.

Nutcracker syndrome got its name because the compression of the renal vein is like a nutcracker cracking a nut.

When the condition shows no symptoms, it’s usually known as nutcracker phenomenon. Once symptoms occur it’s called nutcracker syndrome. Common signs and symptoms include:

  • blood in your urine
  • pelvic pain
  • pain in your side or abdomen
  • protein in your urine, which can be determined by a doctor
  • pain during intercourse
  • enlarged veins in testicles
  • lightheadedness while standing, but not while sitting

The specific causes of nutcracker syndrome can vary. Some people are born with certain blood vessel variations that can lead to symptoms of nutcracker syndrome. Others can develop the syndrome due to changes within the abdomen. Symptoms are more common in females in their 20s and 30s, but it can affect anyone of any age.

Some conditions that may increase the chance of developing nutcracker syndrome include:

  • pancreatic tumors
  • tumors in the tissue lining your abdominal wall
  • a severe lower spine curve
  • nephroptosis, when your kidney drops into your pelvis when you stand up
  • an aneurysm in your abdominal aorta
  • rapid changes in height or weight
  • low body mass index
  • enlarged lymph nodes in your abdomen
  • pregnancy

In children, rapid growth during puberty can lead to nutcracker syndrome. As body proportions change, the renal vein can become compressed. Children are more likely to have fewer symptoms compared with adults. Nutcracker syndrome isn’t inherited.

First, your doctor will perform a physical exam. Next, they’ll take a medical history and ask about your symptoms to help them narrow down a possible diagnosis.

If they suspect nutcracker syndrome, your doctor will take urine samples to look for blood, protein, and bacteria. Blood samples can be used to check blood cell counts and kidney function. This will help them narrow down your diagnosis even further.

Next, your doctor may recommend a Doppler ultrasound of your kidney area to see if you have abnormal blood flow through your veins and arteries.

Depending on your anatomy and symptoms, your doctor also may recommend a CT scan or MRI to look more closely at your kidney, blood vessels, and other organs to see exactly where and why the vein is compressed. They might also recommend a kidney biopsy to help rule out other conditions that can cause similar symptoms.

In many cases, if your symptoms are mild, your doctor will likely recommend observation of your nutcracker syndrome. This is because it can sometimes go away on its own, particularly in children. In children under 18, studies show that the symptoms of nutcracker syndrome may resolve themselves approximately 75 percent of the time.

If your doctor does recommend observation, they’ll do regular urine tests to track your condition’s progression.

If your symptoms are more severe or don’t improve after an observation period of 18 to 24 months, you might need treatment. There are a variety of options.


A stent is a small mesh tube that holds the compressed vein open and allows blood to flow normally. This procedure has been used for nearly 20 years for the treatment of this condition.

Your doctor can insert it by cutting a small slit in your leg and using a catheter to move the stent into the proper position inside your vein. However, like any procedure, there are risks.

About 7 percent of people experience movement of the stent. This can lead to complications such as:

  • blood clots
  • blood vessel injury
  • severe tears in the blood vessel wall

Stent placement requires an overnight hospital stay and full recovery can take several months. You and your doctor should discuss the risks and benefits of this procedure, as well as other treatment options.

Blood vessel surgery

If you have more severe symptoms, blood vessel surgery may be a better option for you. Your doctor might recommend a variety of surgical procedures to relieve pressure on the vein. Options can include moving the vein and reattaching it, so it’s no longer in an area where it would be compressed.

Another option is bypass surgery, in which a vein taken from elsewhere in your body is attached to replace the compressed vein.

Recovery from surgery depends on the type of surgery and your overall health. It generally takes several months.

Nutcracker syndrome can be hard for doctors to diagnose, but once it’s diagnosed, the outlook is often good. Correcting the condition depends upon the cause.

In many cases in children, nutcracker syndrome with mild symptoms will resolve itself within two years. If you have more severe symptoms, a variety of options may be available to correct the affected vein and have good results for short- and long-term relief.

In those with nutcracker syndrome due to certain medical conditions or tumors, correcting the blood flow problem requires correcting or treating the underlying cause.