Venous compression syndromes

What is May Thurner Syndrome (MTS)?

May Thurner Syndrome (MTS), also known as Iliac Vein Compression Syndrome, is a congenital condition in which the left iliac vein (a major vein in the lower body responsible for returning blood from the legs to the heart) is compressed by the overlying right iliac artery (the major artery that supplies blood to the right leg). This compression prevents drainage of blood from the left leg, increasing the risk of blood clots, known as deep vein thrombosis (DVT). Due to blood being unable to properly drain from the leg and pelvis and return to the heart, MTS can also lead to other complications, including chronic pelvic pain (pelvic congestion syndrome), which can further affect your quality of life.

MTS was first described in 1957 by Dr. May and Dr. Thurner, and it is believed to be underdiagnosed due to the range of symptoms and the overlap with other conditions.

Incidence of May Thurner Syndrome

MTS is relatively rare, occurring in about 2-5% of the general population, though many cases go undiagnosed. It is more commonly found in women, especially those aged 20-40 years, but both men and women can be affected. MTS is also more prevalent in individuals who have experienced blood clots or other venous issues. The condition is often missed in people who do not display clear symptoms, or whose symptoms are attributed to other conditions

Is MTS Congenital or Hereditary?

While May Thurner Syndrome is primarily considered an anatomical variation, its exact origin is still not fully understood. MTS is often not classified as a congenital or hereditary condition. The compression of the iliac vein caused by the right iliac artery is typically considered an anatomical variation, and while it is not inherited in a straightforward manner, certain factors such as pelvic abnormalities or venous insufficiency can increase the likelihood of its development. Though it may be present from birth in some individuals, it doesn’t follow a clear hereditary pattern. Genetic predispositions to venous issues, such as a family history of blood clots or vein problems, could increase the risk of developing MTS, but the condition itself is not directly inherited.

Risk Factors for May Thurner Syndrome

Risk factors that may increase the likelihood of developing MTS include:

  1. Female Sex: Women are at a higher risk due to anatomical differences in the pelvis and hormonal effects on veins.
  2. Age: The condition typically presents in people aged 20 to 40 but can occur at any age.
  3. Pelvic & Spine Abnormalities: Variations or anatomical issues in the pelvis or spine (e.g. scoliosis) may lead to increased pressure on the iliac vein.
  4. Pregnancy: During pregnancy (especially the 3rd trimester), changes in blood volume and pelvic pressure can increase the likelihood of MTS.
  5. Obesity: Increased body weight can lead to more pressure on the veins, contributing to the development and/or worsening of MTS.

Diagnosis of May Thurner Syndrome

If your doctor suspects MTS based on clinical signs and symptoms, they may perform diagnostic tests to confirm the condition. These may include:

  1. Ultrasound
  2. CT or MRI
  3. Catheter Venogram — A specialized imaging procedure where contrast dye is injected into the veins under fluoroscopy (live x-ray), allowing visualization of the compression and blood flow.
  4. Intravascular Ultrasound (IVUS) — This is a high-resolution ultrasound probe that goes inside the blood vessel and can provide information such as the amount of compression and if there is other vascular disease in the vessel. IVUS is typically done at the same time as a venogram.

Your doctor may also take a detailed medical history and conduct a physical examination to rule out other potential causes of your symptoms.

May Thurner Physiology vs. May Thurner Syndrome

May Thurner Physiology refers to the natural anatomical variation where the right iliac artery crosses over and compresses the left iliac vein. This is common in the population and often doesn’t cause any problems. However, May Thurner Syndrome occurs when this compression leads to symptoms like swelling, blood clots, pelvic pain, or pelvic congestion syndrome. While May Thurner Physiology is harmless in many people, May Thurner Syndrome is the symptomatic condition that requires medical attention and treatment. This is why May Thurner Syndrome is a clinical diagnosis and NOT an imaging diagnosis.

Signs and Symptoms of May Thurner Syndrome

The signs and symptoms of MTS can vary greatly. Some individuals may experience no symptoms, while others may present with a range of issues. Common symptoms include:

  • Unexplained Left Leg Swelling
  • Iliofemoral DVT — a blood clot that extends from the pelvic down to the calf/ankle.
  • Increased Urinary Frequency
  • Low Back Pain
  • Hemorrhoids
  • Pelvic Congestion Syndrome (PCS)
  • Scrotal/Testicular Pain

Treatment Options for May Thurner Syndrome

Treatment for MTS depends on the severity of symptoms and whether complications, such as blood clots, have occurred. Treatment options may include:

Conservative Treatment

  1. Compression Stockings: Help reduce swelling in the affected leg and improve circulation.
  2. Lifestyle Modifications: Engaging in regular physical activity and avoiding prolonged periods of sitting or standing can help improve symptoms.
  3. Weight Loss: Is crucial in patients who are overweight or obese. As intraabdominal fat increases, the pressure and compression on the pelvic veins increases, leading to worsening of MTS symptoms.
  4. Blood Thinners (Anticoagulants): If a blood clot has developed, blood thinners may be prescribed to prevent further clotting and reduce the risk of complications.
  5. Pelvic Floor Physical Therapy

Endovascular Procedures

  1. Balloon Angioplasty: A catheter with a balloon is inserted into the iliac vein and inflated to open up the compressed area, improving blood flow. Angioplasty has a low success rate and may only be used in cases when scar tissue has developed inside the iliac vein.
  2. Stenting: A mesh tube (stent) may be placed in the vein to keep it open and restore normal blood circulation. This is the main treatment of MTS.

Importance of Seeing a Vascular Specialist

If you suspect that you have MTS or have been diagnosed with the condition, it’s essential to consult with a vascular specialist. These experts focus on the diagnosis, management, and treatment of diseases of the circulatory system. A vascular specialist can:

  • Provide an accurate diagnosis through appropriate imaging and testing.
  • Offer a tailored treatment plan to manage symptoms and prevent complications.
  • Monitor the progress of your condition and adjust treatments as needed.
  • Help address complications like DVT or pelvic congestion syndrome, which may be linked to MTS.
  • Ensure proper long-term care and management to maintain the best possible circulation and quality of life.

Early diagnosis and intervention can help reduce the risks of complications and improve your overall health.

What is Nutcracker Syndrome?

Nutcracker Syndrome (NCS) is a rare vascular condition that occurs when the left renal vein (the vein that drains blood from the left kidney) is compressed between the abdominal aorta and the superior mesenteric artery. This compression can lead to various symptoms, including pain, hematuria (blood in the urine), and other kidney-related issues.

What Causes Nutcracker Syndrome?

The main cause of Nutcracker Syndrome is the compression of the left renal vein. This compression can occur due to an anatomical variation, where the angle between the aorta and the superior mesenteric artery (SMA) is unusually narrow, creating pressure on the left renal vein. Other contributing factors can include:

  • Abnormal anatomy: In some people, the position of the veins and arteries can lead to compression.
  • Weight loss or weight gain: These changes can change the angle between the aorta and the SMA and/or alter the space in the abdominal area and increase pressure on the renal vein.
  • Pregnancy: During pregnancy, the uterus can grow and exert pressure on the renal vein.

Symptoms of Nutcracker Syndrome

Symptoms can vary from person to person and may be mild or severe. Common symptoms include:

  1. Flank or Abdominal Pain: A dull or sharp pain in the left side, which may worsen with physical activity or certain positions.
  2. Hematuria (Blood in the Urine): This is one of the most common signs of Nutcracker Syndrome. Blood may be visible in the urine, or it may only be detected under a microscope.
  3. Proteinuria: Presence of excess protein in the urine, which may indicate kidney problems.
  4. Varicocele: Swelling of veins in the scrotum, similar to varicose veins, often found in men with Nutcracker Syndrome.
  5. Nausea, Vomiting, or Fatigue: Some individuals experience digestive issues or feel generally unwell.
  6. Pelvic Congestion: In women, Nutcracker Syndrome can cause chronic pelvic pain, especially during menstruation, and may be associated with varicose veins in the pelvic area.

How is Nutcracker Syndrome Diagnosed?

Your vascular specialist may perform imaging tests to diagnose Nutcracker Syndrome, including:

  1. Ultrasound
  2. CT Scan or MRI
  3. Cahteter Venography
  4. Intravascular Ultrasound (IVUS)

Treatment Options for Nutcracker Syndrome

The goal of treatment is to relieve symptoms and prevent further kidney damage. Treatment options depend on the severity of the condition and the patient’s symptoms.

  1. Conservative Management: In mild cases, Nutcracker Syndrome may be managed with lifestyle changes and monitoring. Patients may be advised to:
    • Avoid heavy physical activity that could exacerbate symptoms.
    • Stay hydrated to reduce the risk of kidney stones and blood clots.
    • Manage pain with medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) or other prescribed pain relievers.
  2. Endovascular Procedures: If symptoms are more severe or if there is significant damage to the kidney, minimally invasive procedures may be used. These include:
    • Stenting: A stent may be placed in the renal vein to relieve the compression and improve blood flow. However, this procedure carries risk and is not performed by all endovascular specialists.
    • Balloon Angioplasty: This procedure involves inflating a balloon inside the compressed vein to widen it and restore normal blood flow.
  3. Surgical Treatment: In rare cases where other treatments are ineffective, surgery may be considered. This may involve repositioning the arteries to relieve pressure on the renal vein or even removing part of the renal vein if necessary.

When to See a Vascular Specialist

If you experience any of the following symptoms, it may be time to consult with a vascular specialist:

  • Persistent or worsening pain in the flank or abdomen that does not improve with rest or medication.
  • Blood in your urine (hematuria), whether visible or detected through a lab test.
  • Swelling in the scrotum (for men) or pelvic area (for women), which may be associated with varicose veins or discomfort.
  • Unexplained fatigue, nausea, or digestive issues that affect your quality of life.
  • Suspected varicocele or other symptoms suggestive of vascular issues related to the kidneys or pelvic area.

A vascular specialist can perform specialized tests, such as imaging studies, to confirm whether Nutcracker Syndrome is the underlying cause of your symptoms. Early consultation can help determine the most appropriate treatment and prevent complications.

Learn More About Vein Compression

Read more in the Patient Education Library, where Dr. Sudi explains May Thurner syndrome, Nutcracker syndrome, stents, and what to ask before treatment.

Visit the Patient Education Library
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