What is Nutcracker Syndrome?

The nutcracker syndrome or phenomenon is a rare disease. It is a cause of hematuria secondary to compression of the left renal vein between the superior mesenteric artery and the aorta.

It can appear in both sexes; its prevalence is not known since it is normally asymptomatic.

Nutcracker Renal Syndrome is a rare or low-prevalence disease, included as such in the national list of Rare Diseases, and is caused by entrapment of the left renal vein as it passes through the aorto-mesenteric clamp. 

This compression translates into renal suffering, a risk for the kidney, a painful and limiting process for the patient who suffers it. In such a case, high pressure of the left renal venous system is a consequence of the whole process, with the subsequent development of collateral varicose veins. At the level of the renal pelvis and ureter, which can communicate with the excretory pathway and lead to episodes of macro or microhematuria and proteinuria.

Although it is more common in women between the second and fourth decade of life, men and children can also suffer. Its causes can be congenital, that is; birth, as well as it can be caused by renal ptosis, by a significant loss of weight and perirenal fat, by lumbar hyperlordosis, or by strong trauma. 

It can also occur as a consequence of the abnormally high course of the left renal vein, or a branch, also abnormal, of the superior mesenteric artery as it emerges from the aorta. Similarly, it can occur during pregnancy and worsen during the third trimester.

It is worth distinguishing between two different entities: the Nutcracker Phenomenon, where we find this anatomical peculiarity without it producing any signs, symptoms, or pain, and the Nutcracker Syndrome, which is what concerns us here, and which presents with signs and symptoms such as micro or macro hematuria.

That consists of mild to highly incapacitating pain. Which develops as a result of abnormal pressure and excessive in the circulatory system, and that causes the creation of varicose veins throughout the pelvic area, genito-urinary system, and legs.

Causes of Nutcracker Syndrome

The cause of the nutcracker renal syndrome is an alteration in the renal vessels’ anatomy and the arteries located at the level of the left renal vein. Due to their placement, they form a clamp (like a nutcracker) in which the left renal vein is compressed between the superior mesenteric artery and the abdominal aorta.

Symptoms of Nutcracker Syndrome

Clinically, it can remain asymptomatic, which is the most common or manifest as episodes of hematuria (blood in the urine), which can be accompanied by pain in the left renal fossa and abdominal pain. Characteristically, hematuria (and pain if present) is more severe with orthostasis and with exercise.

Diagnosis of Nutcracker Syndrome

It is a difficult pathology to diagnose because, most of the time, it does not give symptoms and because routine methods do not diagnose it. Therefore, the diagnosis should be made in a patient with low back pain and haematuria. Initially, a hematuria study should be performed to rule out other more frequent causes. Diagnostic tests should include urinalysis, ultrasound, and/or intravenous urography, and other imaging tests such as CT, CT angiography, or MRI.

Treatment for Nutcracker Syndrome

The treatment of nutcracker syndrome depends on the severity of the bleeding. Those patients who present intermittent bleeding without anemia will not require any type of treatment, except oral iron supplements if necessary. 

Those cases accompanied by incapacitating left flank pain, frequent macroscopic hematuria, or anemia may require more aggressive treatment that includes surgical techniques. The implantation of an intravascular stent is the best treatment option to keep the left renal vein open. As it is a benign disease, the general prognosis is excellent.