Evaluation of posterior nutcracker phenomenon using multisection spiral CT.

AIM: To prospectively evaluate the epidemiological, anatomical classification, clinical importance, and radiological features of posterior nutcracker phenomenon (PNP) in patients examined with multisection spiral computed tomography (MSCT).

MATERIAL AND METHODS: Patients who underwent abdominal enhanced MSCT from January 2012 to July 2016 were evaluated retrospectively. Combined with the blood, normal biochemistry, and urine tests, patients were assessed retrospectively for renal vein diameter measurements, the compression ratio of blood vessels, gender differences, anatomical classification, percentage of proteinuria and haematuria, and clinical symptoms.

RESULTS: The study included 6,225 consecutive patients, PNP was observed in 2.06% involving the CLRV in 1.22% and retro-aortic left renal vein in 0.84%. The proportion of posterior nutcracker syndrome (PNS) was lower in PNP (17.2%). There was no difference by sex and age in the prevalence of PNP (p>0.05). In patients with urological symptoms, the number of type II abnormalities was more frequent than type Ia and type Ib abnormalities. Meanwhile, the number of type II abnormalities was frequent than the other two types. There was a significant difference between PNS and asymptomatic PNP (aPNP) in all measured values (p<0.001), the ratio was >4, especially in type II abnormalities (ratio >5.0).

CONCLUSIONS: PNP is a type of left renal vein entrapment. It is exceptionally rare and might be underdiagnosed. MSCT and measured values can be useful in diagnosis and recognition.