N utcracker phenomenon (NCP), also known as left renal vein entrapment,1-3 is characterized by impeded outflow from the left renal vein (LRV) into the inferior vena cava (IVC) due to extrinsic LRV compression, often accompanied by demonstrable lateral (hilar) dilatation and medial (mesoaortic) narrowing (schematic representation of NCP/ nutcracker syndrome [NCS] in Figure 1). Although the terms nutcracker syndrome and nutcracker phenomenon are sometimes used interchangeably in the literature, Shin and Lee 4 emphasize that the nutcracker anatomy is not always associated with clinical symptoms and that some of the anatomic findings suggestive of nutcracker may represent a normal variant or be accounted for by other conditions. Therefore, the term nutcracker syndrome should be reserved for patients with characteristic clinical symptoms associated with demonstrable nutcracker morphologic features. No consensus exists on what symptoms are severe enough to warrant the designation of a clinical syndrome or to what extent various findings may simply reflect different evolutionary stages of the process. Because of these uncertainties, some authors focus on the characteristic anatomic and hemodynamic findings, referring to them as NCP rather than NCS.
5Nutcracker phenomenon refers to compression of the left renal vein, most commonly between the aorta and the superior mesenteric artery, with impaired blood outflow often accompanied by distention of the distal portion of the vein. The nutcracker syndrome (NCS) is the clinical equivalent of nutcracker phenomenon characterized by a complex of symptoms with substantial variations. Depending on specific manifestations, NCS may be encountered by different medical specialists. Although it may be associated with substantial morbidity, the diagnosis of NCS is often difficult and is commonly delayed. Diagnostic and treatment criteria are not well established, and the natural history of NCS is not well understood. We performed an initial review of the literature through MEDLINE, searching from 1950 to date and using the keywords nutcracker syndrome, nutcracker phenomenon, and renal vein entrapment. We performed additional reviews based on the literature citations of the identified articles. We attempted to elucidate clinical relevance of these conditions and their prominent features and to summarize professional experience.
Mayo Clin