Department of Vascular and Endovascular Surgery, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, São Paulo, Brazil.
Department of Vascular and Endovascular Surgery, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, São Paulo, Brazil.
J Vasc Surg Venous Lymphat Disord. 2020 Nov;8(6):1058-1065. doi: 10.1016/j.jvsv.2020.04.005. Epub 2020 Apr 23.
We evaluated the frequency of significant left renal vein (LRV) compression, also called the nutcracker phenomenon (NCP), in a normal asymptomatic population.
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.
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.
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.
评估正常无症状人群中左肾静脉（LRV）受压（又称胡桃夹现象（NCP））的频率。
本回顾性描述性解剖学研究分析了活体供肾者高分辨率肾 CT 血管造影的数据。共评估了 324 例 LRV 受压的 CT 检查，包括喙征、主动脉肠系膜夹角<41°、LRV 直径比≥4.9 和喙角≥32°。还评估了骨盆静脉曲张和左精索静脉在近端和中段的存在（如果>0.5cm 则认为扩张）。从病历中收集了人体测量和实验室（尿红细胞计数）数据。使用 Fisher 确切检验和 Student t 检验进行统计推断。
女性的平均主动脉肠系膜夹角为 53.1°，男性为 58.7°（P=0.044）。喙征和喙角的发生率分别为 15.3%和 9.8%，且女性的发生率更高（P=0.01）。30.5%存在主动脉肠系膜夹角<41°，女性更为常见（P<0.01）。直径比阳性率为 0.7%，男女之间无差异。左精索静脉>0.5cm 在近端和中段更为常见（P<0.01）。虽然根据阳性标准（3 或 4）进行分层分析显示男女之间无差异，但与年龄较小呈正相关（P<0.01）。局限性包括没有胡桃夹综合征（NCS）人群；由于需要干预，缺乏肾静脉压力梯度；缺乏其他类型的影像学研究，如双功超声扫描；以及缺乏女性产次数据。
健康个体中 NCP 和 NCS CT 标准的存在频率较高。女性和年轻个体在主动脉肠系膜轴的受压表现更为常见。建议对当前的 NCP 和 NCS 标准进行修订，根据性别、年龄和体重指数进行明确分类，以更好地评估 LRV 压迫事件。
