The relationship between the presence of pyuria and clinical and histopathological findings in primary glomerular diseases

Background: It is well known that leukocyturia can be seen in patients with primary glomerular diseases (PGD) without urinary tract infections. However, there is not enough data in the literature about the frequency of pyuria and associated clinical or pathological findings in different PGD. The clinical presentations of glomerular diseases are nephrotic syndrome (NS), nephritic syndrome, mixed NS (nephrotic and nephritic syndrome) or asymptomatic urinary abnormalities. The aims of this study are to determine the presence of pyuria in different PGD and any potential relationships between pyuria and clinical or histopathological findings of PGD. Methods: The study included 3875 patients with PGD in the database of the Turkish Nephrology Association Glomerular Diseases Working Group. Among these patients, we included 3383 patients that we have the results of urine analysis (in terms of the presence of leukocyturia). At baseline, having 5 or more leukocytes per high power field (HPF) in urine microscopy was considered pyuria. In urine microscopy, 5 or more erythrocytes per HPF was considered as hematuria. The patients were divided into groups according to the presence or absence of pyuria and hematuria. Sociodemographic and clinical characteristics, laboratory data, and renal histopathological results were examined. Results: Six hundred forty five (19%) of 3383 patients (1925 male, 1458 female) had pyuria, whereas 2738 (81%) patients did not have pyuria. The frequency of pyuria was significantly lower in men (42% vs 58%, p <0.05). Glomerular filtration rate (GFR), albumin and hemoglobin values were significantly lower in those with pyuria. Low serum C3 was more frequent in patients with pyuria. The incidence of NS was significantly lower in patients with pyuria (44.5% vs. 53.9%, p <0.05). The frequency of nephritic syndrome in those with pyuria was significantly higher than those without pyuria (28.9% vs. 15.9%, p <0.05, respectively). Mix NS was similarly more frequent in patients with pyuria (7.1% vs. 4.9%, p <0.05). While the frequency of pyuria was 28.6% in membranoproliferative glomerulonephritis (MPGN) patients with NS, it was found to be 42.4% in MPGN patients without NS. Among the patients with IgA nephropathy, the frequency of pyuria were 11.7% and 23.5% in those with NS and without NS, respectively. The numbers of cellular and fibrocellular crescent were significantly higher in patients with pyuria. The frequency of mesangial and endocapillary proliferation, glomerular exudative changes, and the interstitial inflammation were significantly higher in those with pyuria. C3 (3+) staining frequency was higher in patients with pyuria (19.1% vs. 15.1%, p <0.05). Patients with pyuria and hematuria had lower GFR and proteinuria values, whereas low serum C3 and histopathological inflammation were more frequent in these patients. Conclusion: Pyuria is more frequent in patients with active inflammatory changes such as crescent, endocapillary proliferation or mesengial proliferation in kidney biopsy. The frequency of pyuria has increased in PGDs with nephritic syndrome in which glomerular inflammation is prominent. In contrast, the frequency of pyuria is lower in patients with isolated NS. These findings suggest that the presence of pyuria can reflect active glomerular inflammation in patients with PGD.