Nutcracker Syndrome

What is nutcracker syndrome?

Nutcracker syndrome is a condition that affects your left renal vein. This is the vein that carries blood away from your left kidney and back to your heart. Nutcracker syndrome is a type of extrinsic vein compression syndrome. In these syndromes, the structure of your blood vessels puts pressure on one of your veins.

If you have nutcracker syndrome, two arteries in your belly compress part of your left renal vein. This compression raises the blood pressure in your renal vein and forces some blood to flow in the wrong direction. As a result, nearby veins swell, causing symptoms and potentially leading to complications.

Anatomy of your left renal vein

To understand nutcracker syndrome, it’s helpful to know where your left renal vein travels through your body. This vein leaves your left kidney and travels toward your inferior vena cava. Your inferior vena cava is a large vein that collects oxygen-poor blood from the veins in your lower body and returns it to your heart.

In order to reach your inferior vena cava, your left renal vein has to pass between two major arteries in your belly. These are your abdominal aorta and your superior mesenteric artery. Normally, there’s enough space for your vein to pass between these two arteries.

But if you have nutcracker syndrome, there’s not enough space. Most often, your abdominal aorta and superior mesenteric artery press into and squeeze your left renal vein. This is known as anterior nutcracker syndrome because the compression happens in front of your aorta. Anterior nutcracker syndrome is the most common form of the condition.

Less often, the compression occurs behind your aorta, as your renal vein travels between your aorta and your spine. This is called posterior nutcracker syndrome. Researchers have also identified other anatomical variations, but they’re rare.

Nutcracker phenomenon vs. nutcracker syndrome

Nutcracker phenomenon refers to the compression of your renal vein. Some people have this happen yet experience no symptoms. They may not even know they have nutcracker phenomenon until their healthcare provider sees their anatomy on an imaging test.

Nutcracker syndrome refers to the phenomenon when it occurs with symptoms. In this case, the compression of your renal vein causes symptoms you notice, which may greatly disrupt your daily life. People with nutcracker syndrome may need treatment to help blood flow better through their renal veins.

Why is this condition called nutcracker syndrome?

Your abdominal aorta and superior mesenteric artery look like the two levers of a nutcracker, squeezing on your renal vein. That’s what a researcher noticed back in 1937. In describing the anatomy, he said the left renal vein looked like “a nut between the jaws of a nutcracker.”

The condition’s more formal name is left renal vein entrapment syndrome.

Who does nutcracker syndrome affect?

Nutcracker syndrome affects children and adults up through their 60s. Some research shows it’s more common among people in their teens, 20s and 30s. It’s also more common among people who have a lower body mass index (BMI).

How rare is nutcracker syndrome?

Researchers consider nutcracker syndrome a rare condition, but they don’t know exactly how many people have it.

What are the dangers of nutcracker syndrome?

Nutcracker syndrome may cause mild or no symptoms, and it may resolve on its own (especially in children). However, it can sometimes harm your body over time if untreated. Possible complications of unmanaged nutcracker syndrome include:

• Blood clots in your renal vein.
• Kidney damage caused by increased pressure in your renal veins over time.
• Male infertility or female infertility.
• Severe pain that interferes with your quality of life.

What are the signs and symptoms of nutcracker syndrome?

Symptoms of nutcracker syndrome that you may notice include:

• Blood in your pee (hematuria). This is the most common symptom.
• Feeling dizzy when you stand up (caused by orthostatic hypotension).
• Flank pain on your left side.

Symptoms can also vary based on your sex. Men and people assigned male at birth (AMAB) may experience swollen veins in their scrotum (varicocele).

Women and people assigned female at birth (AFAB) may experience symptoms of pelvic congestion syndrome. These include:

• Pain during sex (dyspareunia).
• Pain when you pee (dysuria).
• Pelvic pain.

There are also signs your healthcare provider can see through testing. You can’t see these signs on your own. Clinical signs of nutcracker syndrome include:

• Low levels of red blood cells (anemia).
• Microscopic amounts of blood in your pee (microhematuria).
• Too much protein in your pee (proteinuria).

What causes nutcracker syndrome?

Changes in your blood vessel anatomy cause nutcracker syndrome. Sometimes these changes happen in the womb as your blood vessels are forming. Other times, they happen due to growth spurts during adolescence or weight loss during adulthood. In some cases, there’s no known cause.

How is nutcracker syndrome diagnosed?

Diagnosis of nutcracker syndrome can take a while since providers need to rule out many other possible problems. Generally, the diagnosis begins with a physical exam. Your provider will talk with you about your medical history and your symptoms. Your provider may then recommend one or more tests to investigate further.

Tests that diagnose nutcracker syndrome

Tests you may need include:

• Blood tests.
• Computed tomography (CT) scan.
• Doppler ultrasound.
• Intravascular ultrasound (IVUS).
• Magnetic resonance imaging (MRI).
• Venogram.
• Urinalysis.

What is the treatment for nutcracker syndrome?

Treatment depends on your age and the severity of your symptoms. Based on your situation, your provider may begin with a conservative approach. If your symptoms don’t go away or get worse, you may need surgery.

Conservative management

For many people, especially children under the age of 18, a conservative approach is appropriate. If your child has nutcracker syndrome, their provider may recommend a conservative approach for up to two years. This involves keeping an eye on the situation and helping your child gain weight. Weight gain in your child’s belly area relieves pressure on their renal vein. For adults, providers generally recommend trying a conservative approach for six months.

A conservative approach may involve medications to help kidney function, including:

• ACE inhibitors.
• Aspirin.

Surgical intervention

If you have severe symptoms and a conservative approach doesn’t help, you may need surgery or a minimally invasive procedure. Your provider will discuss your options with you and explain the benefits and risks of each one. Your provider will also discuss if you’re a candidate for minimally invasive methods.

The goal of surgical intervention is to provide an open, smooth pathway for blood to flow from your kidney toward your heart.

Nutcracker syndrome surgeries and procedures include:

• Renal vein transposition: Moves your left renal vein so it attaches to your inferior vena cava at a different location. This allows your renal vein to avoid traveling between your superior mesenteric artery and your aorta. Laparoscopic methods are an alternative to traditional open surgery.
• Stent insertion: Uses percutaneous (minimally invasive) methods to insert a stent into your left renal vein. This small tube helps open up your vein so blood can flow through it.
• Renal autotransplantation surgery: Removes your kidney and re-implants it in a new location near your hip bone.

Is nutcracker syndrome surgery serious?

Surgeries to treat nutcracker syndrome each carry its own risks. Talk with your provider about the risks of your specific procedure.

Renal autotransplantation is the most invasive surgery. The most common complications are kidney failure and bleeding. Seeking care at a high-volume hospital with experienced surgeons can help lower your risk of complications.

How can I reduce my risk of developing nutcracker syndrome?

There’s no known way to reduce your risk. Nutcracker syndrome occurs unpredictably and doesn’t run in families.

However, healthcare providers often diagnose nutcracker phenomenon through tests run for other reasons. So, keeping up with your medical appointments and screenings is important. It can help your provider identify compression of your renal vein that isn’t yet causing you any symptoms. You’ll then be more aware of possible signs and symptoms that could signal you need treatment.

What is the outlook for people with nutcracker syndrome?

The outlook for children is usually excellent. Most children feel better without invasive treatment. In adults, the outlook varies based on the severity of your symptoms and when you receive treatment. Talk with your provider about your specific prognosis.

When should I see my healthcare provider?

Call your provider if you have symptoms of nutcracker syndrome, or if your symptoms get worse.

If you have surgery, closely follow your provider’s instructions on how to care for yourself at home. Be sure to keep all your follow-up appointments.

What questions should I ask my provider?

If your provider diagnosed you with nutcracker syndrome, you probably have lots of questions. It’s important to learn as much as you can about your treatment options and the best timing for treatment. Some questions to ask include:

• How is this condition affecting my body?
• How serious is my condition?
• Do I need treatment? If so, when?
• What’s the best treatment option for me?
• What’s the success rate for this treatment?
• What are the risks of treatment?
• What’s the recovery like?

Some people with nutcracker syndrome also have other vein problems. Talk with your provider about other conditions you may have and how to manage them.

A note from Cleveland Clinic

If you’ve felt symptoms for a while but didn’t know the cause, finally having a diagnosis may feel like a relief. But you may also feel nervous about treatment options and whether you need surgery. The good news is that researchers continue to learn more about the condition and how to manage it through minimally invasive methods. Talk with your provider about the best treatment plan for you and what you can expect going forward.