[Medical Q&A] Is there a "Nutcracker" in the human body?

Planner: Chinese Medical Association

Reviewer: Zhuang Jintao, deputy chief physician, First Affiliated Hospital of Sun Yat-sen University

The nutcracker is a V-shaped tool commonly used by families to crack walnuts. There is also a special "nutcracker" in the human body, but it is a medical image of a special pathological state, the so-called "nutcracker phenomenon."

Since it is like a nutcracker, then from an anatomical structure, there are two "long sides" of the "V"-shaped "nutcracker" in the human body, which are the abdominal aorta and the superior mesenteric artery. Under normal circumstances, the angle between the abdominal aorta and the superior mesenteric artery is 45° to 60°, and the left renal vein passes through this angle and merges into the inferior vena cava. If this angle becomes smaller, in other words, the distance between the abdominal aorta and the superior mesenteric artery is very close, it will compress the left renal vein, just like using a nutcracker to clamp a walnut, and the blood return of the left renal vein will be blocked after being compressed. This "nutcracker phenomenon" may cause a series of symptoms, namely "nutcracker syndrome", such as left-side waist pain (persistent dull pain or severe pain, especially after standing for a long time or physical activity), pelvic congestion, lower limb edema, fatigue and discomfort, etc. The diagnosis of the nutcracker phenomenon requires a combination of the patient's clinical symptoms and signs (such as the presence or absence of low back pain, hematuria, proteinuria, etc.) and imaging examinations (such as color Doppler ultrasound, CT angiography or magnetic resonance angiography, etc.). If confirmed, the doctor will choose different treatment options based on the severity of the patient's symptoms and the results of various examinations, such as conservative treatment (drug therapy, lifestyle adjustment, etc.) or surgical treatment (angioplasty, vascular reconstruction, etc.).