Analysis of Prevalence and Trends in the Biopsy-Proven Native Kidney Diseases in Iranian Population: A 12-year Survey from a Referral Center.

Background & Objective: The prevalence of glomerular diseases, as the leading cause of chronic kidney disease, is increasing. Renal biopsy is still the gold standard for diagnosis of the most kidney disorders. Data on prevalence of the biopsy-proven kidney diseases in Iran is limited and none of the previously reported studies used electron microscopic (EM) evaluation for the diagnosis. This study was conducted to analyze the prevalence of biopsy-proven kidney diseases in a referral center in Iran. Methods: The reports of kidney biopsy samples from 2006 to 2018 referred to a pathology center, affiliated with Tehran University of Medical Sciences were reviewed. The prevalence of different disorders was assessed based on the clinical presentation in 3 age categories, including childhood, adulthood, and elderly. Results: Among 3455 samples, 2975 were analyzed after excluding transplant-related specimens, suboptimal specimens, and those with uncertain diagnoses. Nephrotic syndrome (NS) (39%) was the most common cause of biopsy followed by subnephrotic proteinuria (18%), hematuria in association with proteinuria (15%), renal failure (9%), isolated hematuria (6%), lupus (4%) and the other non-specific manifestations such as hypertetion or malaise (each one less than 2%). The most common diagnoses included membranous nephropathy (MGN) (17.9%), focal segmental glomerulosclerosis (FSGS) (15.9%), lupus nephritis (LN) (13.7%), minimal histopathological findings (unsampled FSGS versus Minimal Change Disease, 12.1%), Immunoglobulin-A (IgA) nephropathy (6.5%) and Alport syndrome (6.1%). MGN was the most frequent disease before 2013, but FSGS became more frequent after that. Conclusion: NS and proteinuria were the most indications for kidney biopsy. Although MGN was the most common disease, the prevalence of FSGS has been increasing in recent years and making it the most common disease after 2013. LN and IgA nephropathy are the most common causes of secondary and primary GN presenting with proteinuria and hematuria, respectively.