Sonographic Diagnosis of Anterior Nutcracker Phenomenon and its Prevalence in Nigerian Males with Varicoceles

Abstract

Background: The nutcracker phenomenon (NCP) is a rare and often unrecognised cause of varicocele, haematuria, and chronic pelvic pain due to the left renal vein (LRV) compression between the aorta and the superior mesenteric artery (anterior nutcracker). Its varied clinical manifestations make the diagnosis difficult and usually delayed. A high index of clinical suspicion, with appropriate imaging studies is crucial for the diagnosis.

Objectives: We used a colour Doppler ultrasound scan to investigate the anatomic and haemodynamic properties of testicular and renal venous drainage. The emphasis was to determine the presence or absence of NCP, its possible effects on varicocele formation and severity, and its relationship with the body mass index (BMI) of the subjects.

Materials and methods: We carried out Doppler scrotal and upper abdominal ultrasound examinations of 100 subjects with male infertility and clinical varicoceles (group A), and 100 controls with male infertility but without varicoceles (group B). The mean peak velocity (PV) and the anteroposterior (AP) diameters of different segments of the renal veins, as well as the diameters of the testicular veins of the subjects in the two groups were measured and compared. The ratios of the PV and the diameters between the hilar portion and the aorto-mesenteric portion of the LRV were also calculated and compared. A PV ratio or anteroposterior diameter ratio between the two portions greater or equal to 5.0 was considered diagnostic of NCP. The diagnosis of varicocele was confirmed by visualising a dilated pampiniform plexus vein measuring greater than 2 mm in diameter using an ultrasound scan.

Results: Six out of 100 subjects in group A had diameter and PV ratios (≥5.0) in the LRV that suggested the presence of NCP, and all participants in group B had neither diameter nor PV ratio suggestive of NCP. The prevalence of NCP seen within the varicocele group in this study was statistically significant (P = 0.038). Five (83.3%) of the six subjects in the NCP-associated varicocele subgroup had microscopic haematuria, orthostatic proteinuria, or both; these qualified them for the diagnosis of nutcracker syndrome (NCS), A significantly lower mean BMI (P = 0.004) was noted among the NCP-associated varicocele subgroup compared to those without NCP.

Conclusion: Our findings indicate that the NCP is a significant finding in patients with varicoceles in our environment, and it is more common with lower BMI.

Keywords: Doppler ultrasonography; nutcracker phenomenon/syndrome; renal haemodynamics; varicoceles.