General data of patients with biopsy-proven renal diseases
In total, 797 patients with biopsy-proven kidney diseases have been screened for LRV entrapment over the study period. The median age of the patients was 44 years and ranged from 12 to 81 years. The male-to-female ratio was 1.32:1. The median BMI was 25.1 kg/m2, and ranged from 13.9 to 47.8 kg/m2.
Glomerular diseases comprised 98% of the total biopsied cases. The most common idiopathic glomerulonephritis was primary membranous nephropathy (PMN) (43%), which was followed by IgAN at 19%. There were 35 (4%) patients with HSPN enrolled in our study (Table 1).
Table 1
The general data of patients with biopsy-proven renal diseases
Characteristic
|
value
|
Demographic data
|
|
Gender (male/female)
|
453/344
|
Age (median, range) (years)
|
44 (12, 81)
|
BMI (median, range) (kg/m2)
|
25.1 (13.9–47.8)
|
Idiopathic glomerular disease
|
No. (%)
|
IgAN
|
152 (19%)
|
PMN
|
340 (43%)
|
FSGS
|
37 (5%)
|
MCD
|
76 (10%)
|
C3 glomerular nephritis
|
1 (0.1%)
|
Secondary glomerular disease
|
No. (%)
|
HSPN
|
35 (4%)
|
Diabetic kidney disease
|
34 (4%)
|
LN
|
50 (6%)
|
Renal amyloidosis
|
7 (0.9%)
|
HBV-glomerular nephritis
|
3 (0.4%)
|
Others
|
43 (5%)
|
Renal tubulointerstitial disease
|
19 (2%)
|
Abbreviations: BMI: body mass index; IgAN: IgA nephropathy; PMN: primary membranous nephropathy; FSGS: focal segmental glomerular sclerosis; MCD: minimal change disease; HSPN: Henoch-schonlein purpura nephritis; LN: lupus nephritis
Lrv Entrapment In Patients With Biopsy-proven Renal Diseases
LRV entrapment was diagnosed in 47 patients (6%), with 46 anterior types and only 1 posterior type. LRV entrapment was observed to coexist with several kinds of renal diseases, including 10 cases diagnosed with HSPN, 22 cases with IgAN, 10 cases with PMN, 1 case with LN, 1 case with Alport syndrome, 1 case with C3 glomerulonephritis, 1 case with renal tubular interstitial nephritis (TIN) and 1 case with renal amyloidosis. Of the 47 patients, the average age was 32.7 years and ranged from 15 to 67 years, and 33 (70%) were females. The average BMI was 20.5 ± 2.9 kg/m2, which was significantly lower than that of patients without LRV entrapment (20.5 ± 2.9 vs. 25.8 ± 4.1, P < 0.001).
The Prevalence Of Lrv Entrapment In Different Types Of Renal Diseases
As shown in Table 2, the prevalence of LRV entrapment in patients with PMN, which was the most common type of renal disease in our cohort, was 3%. The incidence of LRV entrapment in IgAN and HSPN was 14% (22/152) and 29% (10/35) respectively, either of which was significantly higher than that of in PMN (P < 0.001, P < 0.001, respectively). In patients with other types of renal diseases, the frequency of LRV entrapment was similar to that of in PMN (2% vs. 3%, P = 0.406). Patients with IgAN and HSPN were younger and with lower BMI compared with patients with other kidney diseases with statistical significance (Table 2). To identify whether the difference of the distribution of LRV entrapment was due to the discrepancies in age, gender and shape, we performed the PSM analysis.
Table 2
The prevalence of LRV entrapment in different types of renal diseases
|
LRV entrapment %
|
Age
(mean ± s.d.)
|
Female
No. (%)
|
BMI
(mean ± s.d.)
|
PMN
|
3 (10/340)
|
47.6 ± 12.9
|
129 (38%)
|
26.0 ± 4.2
|
IgAN
|
14 (22/152)*
|
39.0 ± 13.7*
|
70 (46%)*
|
25.0 ± 3.9*
|
HSPN
|
29 (10/35)*
|
35.0 ± 18.2*
|
18 (51%)
|
24.1 ± 4.3*
|
Other types
|
2 (4/220)
|
43.8 ± 14.8*
|
87 (40%)
|
25.8 ± 4.4
|
Abbreviations: LRV: left renal vein; BMI: body mass index; PMN: primary membranous nephropathy; IgAN: IgA nephropathy; HSPN: Henoch-schonlein purpura nephritis. |
Since HSPN is considered to be a systemic form of IgAN (21, 22), we merged patients with IgAN and HSPN into one group (expanded IgAN group). The prevalence of LRV entrapment in expanded IgAN was still significantly higher than that in non-expanded IgAN (17% vs. 2%, P < 0.001). The 1:2 PSM yielded matched pairs of 161 patients with expanded IgAN and 322 patients with non-expanded IgAN, resulting in no differences in age, gender, BMI. In the matched cohort, 21 patients (13%) with expanded IgAN were combined with LRV entrapment compared with 8 patients (2%) with non-expanded IgAN (P < 0.001) (detailed in Table 3).
Table 3
Characteristics of the patients before and after propensity score matching
|
Before matching
|
|
After matching
|
|
Expanded IgAN
(n = 187)
|
Non-expanded IgAN
(n = 610)
|
P-value
|
|
Expanded IgAN
(n = 161)
|
Non-expanded IgAN
(n = 322)
|
P-value
|
Female gender %
|
47 (88/187)
|
42 (256/354)
|
0.238
|
|
48 (78/161)
|
43 (140/322)
|
0.332
|
Age (years)
|
38.3 ± 14.6
|
44.9 ± 14.2
|
< 0.001
|
|
41.6 ± 13.1
|
41.5 ± 13.2
|
0.965
|
BMI (kg/m2)
|
24.7 ± 4.0
|
25.7 ± 4.2
|
0.011
|
|
24.9 ± 3.6
|
25.5 ± 4.1
|
0.128
|
LRV entrapment %
|
17 (32/187)
|
2 (15/610)
|
< 0.001
|
|
13 (21/161)
|
2 (8/322)
|
< 0.001
|
Abbreviations: IgAN: IgA nephropathy; BMI: body mass index; LRV: left renal vein. |
Clinicopathological Features Of Patients With And Without Lrv Entrapment In Igan And Hspn
The detailed data of clinicopathological features of patients with and without LRV entrapment in IgAN and HSPN were listed in supplementary Table 1. The values of BMI in IgAN or HSPN patients with LRV entrapment were significantly much lower than those of patients without LRV entrapment (20.2 ± 3.0 kg/m2 vs. 25.3 ± 3.8 kg/m2, P < 0.05; 19.3 ± 1.5 kg/m2 vs. 26.1 ± 3.3 kg/m2, P < 0.05, respectively). In HSPN patients, patients with LRV entrapment had lower levels of baseline 24-hour urine protein and higher levels of serum albumin compared with patients without LRV entrapment (0.8 ± 0.4 g/d vs. 1.7 ± 1.1 g/d, P < 0.05; 42.5 ± 4.2 g/l vs. 37.6 ± 5.4 g/l, P < 0.05). No obvious difference was found in other clinical and pathological indices.
Association Of Lrv Entrapment With Glomerular Incidental Iga And Gd-iga1 Deposition
Since LRV entrapment was more common in expanded IgAN, we further explored the association of LRV entrapment with glomerular incidental IgA deposition in non-expanded IgAN patients. LN is a disease with “full-house” immunofluorescent staining, and only one LRV entrapment was detected in patients with LN in our cohort, we excluded patients with LN in the analysis either. Removing patients with expanded IgAN and LN, there were 560 patients left in the analytic cohort. Among the 560 patients, 53 (9%) had glomerular incidental IgA deposition, and 14 (3%) had LRV entrapment. As shown in Table 4, in LRV entrapment group, 43% (6/14) of patients had glomerular incidental IgA deposits. While in non-LRV entrapment group, glomerular IgA deposits were observed in only 9% (47/546) of patients, the prevalence of which was significantly lower than that of patients with LRV entrapment (P < 0.001).
Table 4
Association of LRV entrapment with glomerular IgA deposition in patients without expanded-IgAN and LN
|
Glomerular IgA deposits
|
|
|
LRV entrapment group (n = 14)
|
Non-LRV entrapment group (n = 546)
|
P-value
|
Total cases
|
6 (6/14, 43%)
|
47 (47/546, 9%)
|
< 0.001
|
PMN
|
4 (4/10, 60%)
|
31 (31/330, 9%)
|
0.020
|
TIN
|
1 (1/1,100%)
|
0 (0/14, 0%)
|
-
|
C3 GN
|
1 (1/1,100%)
|
0 (0/0, 0%)
|
-
|
Other types
|
0 (0/2, 0%)
|
16 (16/198, 8%)
|
-
|
Abbreviations: LRV: left renal vein; IgAN: IgA nephropathy; LN: lupus nephritis; PMN: primary membranous nephropathy; TIN: tubular interstitial nephritis; C3GN: C3 glomerulonephritis |
Gd-IgA1 has been identified as among the essential effector molecules in the pathogenesis of IgAN. Subsequently we conducted double-immunofluorescence staining of IgA and Gd-IgA1 in patients with glomerular incidental IgA deposition. As shown in Table 4, in LRV entrapment group, 6 patients had incidental IgA deposits, we got kidney specimens from 5 out of the 6 patients (3 from PMN, 1 from TIN and 1 from C3 glomerulonephritis), and Gd-IgA1 deposition was observed in all of the 5 patients (Fig. 1). In non-LRV entrapment group, 47 patients had incidental IgA deposits. In order to match the pathological types with LRV entrapment patients, we randomly chose 17 PMN patients accompanied by IgA deposition to perform KM55 staining, and Gd-IgA1 was only detected in 5 of the 17 patients (Fig. 1). Patients with LRV entrapment were significantly more common to have glomerular incidental Gd-IgA1 deposition (5/5 vs. 5/17, P = 0.01).