Which syndrome involves compression of the left renal vein resulting in flank pain?

Nutcracker syndrome refers to the compression of the left renal vein, often between the aorta and the superior mesenteric artery, which can lead to various symptoms, including flank pain and hematuria. This compression occurs due to the anatomical position of the left renal vein in comparison to the surrounding structures, and it is aptly named for the way the vein is pinched or "crushed," similar to a nutcracker. The clinical presentation may also include venous congestion and secondary renal problems, as the compromised blood flow can lead to increased pressure and discomfort in the area.

Other conditions listed, such as May-Thurner syndrome, primarily involve compression of the left common iliac vein by the right common iliac artery, leading to leg swelling and venous insufficiency. Paget-Schroetter syndrome is associated with thrombosis of the axillary-subclavian vein, typically from upper extremity effort, and post-thrombotic syndrome emerges as a complication from previous deep vein thrombosis, characterized by long-term symptoms in the affected limb. These conditions do not directly involve the left renal vein or cause flank pain as a primary symptom of their pathophysiology.