Micro- and macroscopic hematuria caused by renal vein entrapment: systematic review of the literature

Background: Hematuria secondary to renal vein entrapment is mentioned only passing in textbooks and reviews. Methods: We performed a search of the National Library of Medicine database for peer-reviewed publications using the terms “renal vein” or “nutcracker” and “hematuria”. Results: We identified 187 published reports/studies that covered 736 patients, of whom 288 had microscopic hematuria and 448 had macroscopic hematuria. The patient cohort comprised 159 patients aged ≤17 years. Abdominal pain was absent in approximately 65 % of all patients, and a clinically relevant left-sided varicocele was observed in 29 % of the male patients. A normal pre-aortic left renal vein and an anomalous anatomy were noted in 680 and 56 patients, respectively. The body mass index (BMI) was lower in patients with renal vein entrapment than in the controls, with a regression of hematuria correlating with an increase in BMI. A surgical procedure was attempted in 34 % of the patients, of which the most common were endovascular stenting and transposition of the renal vein distally into the vena cava. Conclusions: In cases of unexplained hematuria with or without abdominal pain, clinicians should consider the diagnosis of renal vein congestion, especially in males with varicocele. Ultrasonic Doppler flow scanning is the recommended initial diagnostic modality in these patients. Expectation management is advised in the great majority of cases.