Prevalence of renal vein compression (nutcracker phenomenon) signs in computed tomography angiography of healthy individuals.

OBJETIVE: to evaluate the frequency of significant LRV compression, also called nutcracker phenomenon (NCP), in a normal asymptomatic population. MATERIAL AND METHODS: This retrospective descriptive anatomical study was based on the analysis of high-definition renal computed tomography (CT) angiography of living kidney donors. A total of 324 CT exams were evaluated for signs of LRV compression, including beak sign, aortomesenteric angle 4.9, beak angle>32 masculine. The presence of pelvic varicose veins and the left gonadal vein (LGV) in the proximal and mid portion (dilated when >0.5cm) was also evaluated. Anthropometric and laboratory (urine erythrocyte count) data were collected from medical records. Statistical inference was calculated using Fisher's exact test and Student's t-test. RESULTS: Mean aortomesenteric angle was 53.1 degrees in women and 58.7 degrees in men (p=0.044). Beak sign and beak angle were present in 15.3% and 9.8%, respectively, both with a higher prevalence among women (p=0.01). Aortomesenteric angle 0.5 cm was more prevalent among women in both the proximal and mid portions (p<0.01). Although analysis by the group of positive criteria (three or four) showed no difference between sexes, there was a positive correlation with younger age (p<0.01). Limitations include the absence of a nutcracker syndrome (NCS) population; the lack of renocaval pressure gradient, because of the need for an intervention; the abscence of other types of imagins, such as duplex scan; the absense of woman parity data. CONCLUSION: The NCP and NCS tomographic criteria are present with a high frequency in healthy individuals. Women and younger individuals showed a greater prevalence of compression findings in the aortomesenteric axis. Revision of the current nutcracker phenomenon criteria with a distinct categorization between sex and age is recommended to better evaluate LRV compressive events.