Prevalence of left renal vein compression (nutcracker phenomenon) signs on computed tomography angiography of healthy individuals.
OBJECTIVE
We evaluated the frequency of significant left renal vein (LRV) compression, also called the nutcracker phenomenon (NCP), in a normal asymptomatic population.


METHODS
The present retrospective descriptive anatomic study analyzed the data from high-definition renal computed tomography (CT) angiography of living kidney donors. A total of 324 CT examinations were evaluated for signs of LRV compression, including the beak sign, aortomesenteric angle <41°, LRV diameter ratio ≥4.9, and beak angle ≥32°. The presence of pelvic varicose veins and the left gonadal vein in the proximal and mid-portion (considered dilated if >0.5 cm) were also evaluated. Anthropometric and laboratory (urine erythrocyte count) data were collected from the medical records. Statistical inference was calculated using Fisher's exact test and Student's t test.


RESULTS
The mean aortomesenteric angle was 53.1° in women and 58.7° in men (P = .044). The beak sign and beak angle were present in 15.3% and 9.8%, respectively, and both had a greater prevalence in the women (P = .01). An aortomesenteric angle <41° was identified in 30.5%, with a greater prevalence in women (P < .01). The diameter ratio was positive in 0.7% of the cases, with no difference between the sexes. A left gonadal vein >0.5 cm was more prevalent in women in both the proximal and the mid-portions (P < .01). Although analysis stratified by positive criteria (3 or 4) showed no difference between the sexes, a positive correlation was found with younger age (P < .01). The limitations included the absence of a nutcracker syndrome (NCS) population; the lack of a renocaval pressure gradient, because of the need for intervention; the absence of other types of imaging studies, such as duplex ultrasound scan; and the absence of female parity data.


CONCLUSIONS
The NCP and NCS CT criteria were 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 NCP and NCS criteria with a distinct categorization between sex, age, and body mass index is recommended to better evaluate LRV compressive events.
['Ribeiro|Felipe S|FS|', 'Puech-Leão|Pedro|P|', 'Zerati|Antonio E|AE|', 'Nahas|William C|WC|', 'David-Neto|Elias|E|', 'De Luccia|Nelson|N|']
D000328:Adult D000367:Age Factors D001938:Brazil D000072226:Computed Tomography Angiography D003251:Constriction, Pathologic D005260:Female D006801:Humans D016030:Kidney Transplantation D019520:Living Donors D008297:Male D008875:Middle Aged D061330:Multidetector Computed Tomography D010690:Phlebography D011237:Predictive Value of Tests D015995:Prevalence D059228:Renal Nutcracker Syndrome D012082:Renal Veins D012189:Retrospective Studies D012737:Sex Factors
Nutcracker phenomenon Nutcracker syndrome Kidney transplantation Renal vein entrapment syndrome