Background: Chronic kidney disease (CKD) affects up to 40% of individuals with diabetes mellitus. Given the fact that CKD in diabetics may result from various non-diabetic renal disorders, kidney biopsy remains essential in cases with atypical clinical presentation. The aim of this study was to assess the prevalence of diabetic nephropathy (DN) and other non-diabetic kidney diseases (NDKD) among diabetic patients who underwent renal biopsy. We also tried to find clinical and laboratory markers predicting the presence of DN in renal tissue. Methods: A retrospective analysis of all native renal biopsies in diabetic patients performed between 2010 and 2024 in one European nephrology center. Results: The cohort included 115 diabetic patients. DN was diagnosed in 43.5% individuals. Among NDKD cases, vasculitis (8.7%), membranous nephropathy (7.8%), and amyloidosis (7.8%) were most frequent. Compared with the NDKD group, patients with DN were younger, had a longer duration of DM, more often required insulin therapy, more frequently demonstrated diabetic retinopathy (DR) and nephrotic syndrome, and exhibited higher HbA1c levels. In multivariable logistic regression, younger age, need for insulin therapy, and presence of DR were the strongest predictors of DN. Conclusions: NDKD is common among DM patients. Patient’s younger age, the need for insulin therapy, and the presence of DR are strong predictive markers for diabetic nephropathy. Renal biopsy remains the most accurate method for diagnosis and should be considered in every case of suspected NDKD.

Background: In recent years, Poland has observed fluctuations in kidney biopsy frequency and shifts in diagnostic patterns. These trends likely reflect evolving clinical practice, diagnostic advancements, and changing disease epidemiology. This study aimed to analyse these changes, assess biopsy-based diagnoses across age groups, and examine sex-related variability. Methods: We conducted a single-centre, retrospective study at a university hospital in southwestern Poland, covering 2010–2024. Data from 1969 kidney biopsies were collected, within 1291 native kidney cases analysed after excluding transplant recipients. Diagnoses were correlated with patients’ age, sex, presence of diabetes, and temporal trends, and compared with previous studies. Results: Biopsy numbers increased over time, peaking in 2021 (154 procedures). Most were performed in patients aged 40–64 years (46.1%), followed by 18–39 years (39.1%) and ≥65 years (14.8%), with a rising proportion of elderly patients. Repeated biopsies occurred in 7.7% (second) and 0.6% (third biopsy). The most frequent diagnoses were IgAN (16.9%), FSGS (14.7%), and lupus nephritis (11.4%). In patients ≥65 years, amyloidosis (13.6%), FSGS (13.1%), vasculitis (13.1%), and membranous nephropathy (12%) predominated. The most marked sex-related difference involved lupus nephritis, accounting for 20.3% of diagnoses in women, who made up 82.3% of lupus nephritis cases. While most diseases showed male predominance, this was not evident for several, including IgAN and diabetic nephropathy. Conclusions: Given CKD’s underdiagnosis and frequent late detection in Poland, updated multicentre studies are needed to better recognise disease patterns and raise public awareness.

Lupus nephritis is one of the most severe manifestations of systemic lupus erythematosus and remains a major cause of chronic kidney damage and progression to end-stage renal disease. Although kidney biopsy is considered the diagnostic gold standard, its invasive nature, risk of complications, sampling limitations, and limited suitability for repeated monitoring highlight the need for reliable non-invasive biomarkers. Urinary exosomes have emerged as a promising source of renal molecular information because they are easily accessible and contain stable bioactive molecules, including microRNAs, transfer RNA-derived fragments, messenger RNAs, long non-coding RNAs, and proteins. This review summarizes available evidence on urinary exosomal biomarkers in lupus nephritis, with particular emphasis on their potential utility in diagnosis, assessment of disease activity, monitoring of treatment response, and prognosis. The literature search was conducted in PubMed and Embase using the keywords “lupus nephritis” and “urinary exosomes”. Studies were included if they investigated urinary exosomes in lupus nephritis and evaluated their relevance to disease diagnosis, activity, therapeutic response, histopathological findings, or renal outcomes. Among the analyzed biomarkers, urinary exosomal miR-146a appears to be the most consistently reported diagnostic marker, showing increased expression in active lupus nephritis and the ability to distinguish patients with renal involvement from those without nephritis. Other molecules, including selected miRNAs, tsRNAs, long RNAs, and proteins, have also shown potential clinical relevance, although their validation remains limited. Current evidence suggests that urinary exosomes may provide a non-invasive platform for improving the clinical assessment of lupus nephritis. However, most available studies are limited by small sample sizes, single-center designs, heterogeneous methodologies, and insufficient external validation. Further large-scale prospective studies are required to standardize exosome isolation and biomarker quantification and to determine whether urinary exosomal biomarker panels can complement kidney biopsy in clinical practice.

The endothelin system is critical in chronic kidney disease (CKD) pathogenesis. However, the relative contribution of circulating endothelin-related biomarkers versus genetic variability remains unclear, particularly in diabetic nephropathy (DN) and after kidney transplantation (KTx). This study evaluated plasma concentrations of endothelin-1 (ET-1), endothelin A receptor (ETAR), and anti-ETAR antibodies (ETAR-Ab) in healthy controls, diabetic nephropathy (DN) patients, and DN patients after kidney transplantation (post-KTx). The influence of polymorphisms rs5370 (EDN1) and rs5333 (EDNRA) on endothelin-related parameters was analyzed. Polymorphisms were genotyped via PCR-RFLP, and endothelial-related parameters were determined by ELISA. Significant endothelin system activation was observed in both DN and post-KTx patients. ET-1 and ETAR concentrations were markedly elevated compared to controls, with the highest ET-1 levels detected in the post-KTx group, whereas ETAR-Ab levels were reduced. A sex-specific association for rs5370 was observed in male patients with the TG genotype (a nearly 4.5-fold higher risk of renal replacement therapy than in female patients). In proteinuric DN patients, the TC genotype (rs5333) was associated with elevated ETAR and ETAR-Ab. Endothelin system dysregulation is a prominent and persistent feature of CKD, noted after kidney transplantation. The endothelin activation, observed in transplant patients particularly, highlights the potential clinical relevance of endothelin-related biomarkers and supports the rationale for therapeutic strategies targeting the endothelin pathway, including endothelin receptor antagonists.