OVERVIEW

What is Nutcracker Syndrome?

Nutcracker syndrome, also known as left renal vein entrapment syndrome, occurs when the left renal vein is compressed as it passes between other abdominal blood vessels (the abdominal aorta and superior mesenteric artery), forming an angle resembling a nutcracker, leading to clinical symptoms.

Common manifestations include hematuria (reddish urine), usually without other discomfort, though left flank pain may occasionally occur.

It primarily affects children and is rare in adults. Mild cases in children may resolve spontaneously as the body develops.

How does Nutcracker Syndrome differ from the normal structure of the left renal vein?

Under normal circumstances, the angle between the superior mesenteric artery and the abdominal aorta is filled with mesentery, fat, lymph nodes, and peritoneum, preventing compression of the left renal vein.

When the left renal vein has an abnormal anatomical position, the angle formed as it passes between other abdominal vessels (the abdominal aorta and superior mesenteric artery) becomes too narrow, compressing the left renal vein and causing symptoms such as hematuria—this is Nutcracker Syndrome.

Is Nutcracker Syndrome common?

It is not very common but is prone to being missed or misdiagnosed.

SYMPTOMS

What are the symptoms of Nutcracker Syndrome?

• May cause hematuria (red-colored urine), usually without other symptoms, sometimes accompanied by left flank pain;
• Males may experience left testicular pain, while females may have lower left abdominal pain (due to the left gonadal vein draining into the left renal vein, affected by left renal vein hypertension);
• Can lead to proteinuria;
• Less common manifestations, such as varicocele or lower limb varicose veins.

CAUSES

What are the causes of Nutcracker Syndrome?

The exact cause is unknown.

Who is commonly affected by Nutcracker Syndrome?

It mainly occurs in children and thin individuals.

DIAGNOSIS

What tests are needed to diagnose nutcracker syndrome?

Abdominal ultrasound, CT, Doppler ultrasound, and renal venography can aid in diagnosis. Sometimes diagnosis is challenging, and invasive tests may be required, depending on the specific situation.

Which diseases can nutcracker syndrome be easily confused with?

Kidney stones, urogenital tumors, pelvic congestion syndrome, and superior mesenteric artery syndrome.

TREATMENT

Which department should I visit for Nutcracker Syndrome?

Generally, you should visit the Nephrology Department. For surgical treatment, consult the Urology Department.

How is Nutcracker Syndrome treated?

Treatment options depend on the severity of symptoms.

• Patients with mild symptoms can undergo conservative treatment, especially children, as the condition may resolve with physical development. The focus of this therapy is weight gain to increase retroperitoneal fat, thereby decompressing the left renal vein by altering the position of the left kidney.
• If significant left flank pain persists, along with persistent hematuria leading to anemia, renal impairment, or renal hypertension, treatments such as left renal vein stenting, superior mesenteric artery or left renal vein transposition, or left kidney autotransplantation may be considered.

How often should Nutcracker Syndrome patients undergo follow-up examinations?

Regular follow-ups are necessary, at least once a year, including ultrasound, renal function tests, and urinalysis.

DIET & LIFESTYLE

What should patients with Nutcracker Syndrome pay attention to in their daily life and diet?

They should avoid lumbar trauma and rapid weight loss. If there is obvious hematuria, bed rest is necessary, and anti-inflammatory or hemostatic treatment may be required when needed.

PREVENTION

Can Nutcracker Syndrome Be Prevented?

Since the cause is unknown, there are currently no effective preventive measures.