Rutherford's 165: Nutcracker Syndrome

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This video explores Nutcracker Syndrome (NCS), a relatively rare and somewhat controversial vascular condition. It is named for the compression of the left renal vein (LRV), typically as it passes between the aorta and the superior mesenteric artery (SMA), resembling a nut in a nutcracker's jaws. This is known as anterior NCS. Compression can also occur in a retro-aortic position between the aorta and spine (posterior NCS) or in atypical forms.

A crucial distinction is made between Nutcracker Phenomenon (NCP) and NCS. NCP is the presence of LRV compression on imaging without symptoms. Many people have this anatomical finding asymptomatically. NCS, however, occurs when compression leads to a range of symptoms. There is debate if NCS is a distinct syndrome, as LRV compression is sometimes seen as normal or managed without major issues.

While initially thought more common in young women, recent studies suggest NCS might be equally prevalent in men and women and can occur in older patients. A lower body mass index (BMI) seems associated with developing symptomatic NCS. Genetics is not considered a link. Other factors potentially contributing to compression include a sharper aorta-SMA angle (often less than 16 degrees vs. normal 35-40 degrees), lack of retroperitoneal fat, weight loss, and left kidney ptosis.

Symptoms arise from two main issues: high pressure in the LRV (hypertension) and resulting gonadal vein reflux leading to pelvic venous disorders/pelvic congestion syndrome (PCS). Classic symptoms are left flank pain and hematuria (blood in urine), which can be microscopic or visible. The high LRV pressure is thought to cause leakage of blood cells/proteins into urine or rupture of fragile veins in the kidney. Pelvic symptoms like painful intercourse, urination, or periods (dyspareunia, dysuria, dysmenorrhea) can occur due to pelvic vein congestion. Varicose veins, including left-sided varicoceles in men or vulvar varices in women, may be present. Symptoms are highly variable, contributing to diagnostic delays.

Diagnosis relies on clinical history and imaging. Ruling out other compression causes (e.g., tumors) is key. Historically, venography with pressure gradient measurement was confirmatory. Today, non-invasive cross-sectional imaging (CT/MRI) are initial tools, showing anatomical compression ("beak sign") and collateral veins. Duplex ultrasound (DUS) is a non-invasive screening tool assessing flow and ratios. No single test is gold standard.

Treatment is considered for patients with significant symptoms (pain, anemia from hematuria, debilitating pelvic issues). For children, conservative management (observation) may be an option, hoping they outgrow it. For adults or severe cases, intervention aims to relieve LRV hypertension.

Open surgical options for anterior NCS include LRV transposition (moving the vein), often with a vein patch, gonadal vein transposition (using a tributary as outflow), or bypass grafts. Gonadal vein transposition is favoured at the authors' institution when anatomy allows. Open surgery is generally effective in relieving symptoms but carries surgical risks and potential for needing further procedures. Open surgery for posterior NCS is more technically challenging.

Endovascular treatment, primarily LRV stenting, is less invasive but has limitations. While studies report technical success and symptom improvement, significant concerns exist regarding long-term durability and complications like stent migration (potentially to the heart/lungs), in-stent thrombosis, and fracture. Many stents used were not designed for veins. The development of dedicated venous stents offers hope for improved safety and outcomes in the future. Hybrid approaches combining open and endovascular techniques are emerging but have limited data.

Management of NCS is complex, requires multidisciplinary input, and lacks universal consensus. Research continues to refine diagnosis, patient selection for treatment, and optimal intervention strategies. The exact factors determining why some with anatomical compression develop symptoms remain an area of inquiry.

Source: Excerpts from the transcript of the YouTube video "Rutherford's 165: Nutcracker Syndrome". The video provides summaries of chapters from Rutherford's Vascular and Endovascular Therapy textbook.