Associations of left renal vein entrapment with IgA nephropathy and glomerular galactose-deficient-IgA1 deposition

Objectives: To identify whether left renal vein (LRV) entrapment was more prevalent in IgA nephropathy (IgAN) and Henoch-Schönlein purpura (HSPN) compared with other types of renal diseases, and the association of LRV entrapment with glomerular incidental IgA and galactose-deficient-IgA1 (Gd-IgA1) deposition. Methods: 797 patients with biopsy-proven kidney diseases have been screened for LRV entrapment by color Doppler ultrasound, and the prevalence of LRV entrapment in different types of renal diseases were then analyzed. Propensity score matching analysis was used to adjust for age, gender and body mass index. Immunostaining of Gd-IgA1 with KM55 was performed in paraffin-embedded sections of renal biopsy specimens. Results: LRV entrapment was diagnosed in 47 patients (6%) with several kinds of renal diseases in our cohort. 32 (68%) LRV entrapments were combined with expanded IgAN (idiopathic IgAN and HSPN). The prevalence of LRV entrapment in expanded IgAN was significantly higher than that in non-expanded IgAN (17% vs. 2%, P <0.001), even after adjustment for age, gender and body mass index by propensity score matching analysis (13% vs. 2%, P <0.001). Removing expanded IgAN and LN, glomerular incidental IgA deposition was observed to be significantly more common in patients with LRV entrapment compared with patients without it (43% vs. 9%, P <0.001). Furthermore, in glomerular diseases with incidental IgA deposits, significantly much larger proportion of patients with LRV entrapment were positive for glomerular Gd-IgA1 in contrast to patients without LRV entrapment (5/5 vs. 5/17, P =0.01). Conclusion: LRV entrapment might be associated with glomerular Gd-IgA1 deposition and the development of IgAN.