A Spectrum of Biopsy - Proven Renal Disorders and Their Clinicopathological Correlation in Elderly Population From a Tertiary Care Center in South India

Abstract

Introduction Chronic kidney disease (CKD) has become a health concern with an extensive burden on incidence and prognosis. While the increasing lifespan contributes to a higher incidence of CKD among the elderly, the diagnostic picture in this age group is complicated by senescence-related changes. A better understanding of the etiology and progression of the disease warrants renal biopsy in such patients. This study aims to explore the histopathological spectrum of native renal biopsies leading to CKD in elderly patients in a tertiary care hospital. Methods Among the list of patients who had undergone renal biopsy at our institute from January 2015 to March 2020, elderly patients aged ≥ 60years were chosen for this study. Their demographic details, lab investigations and histopathological reports were collected. The sex distribution and prevalence of different renal diseases was calculated. The subjects were classified into four broad diagnostic groups - primary glomerular disease, diabetic nephropathy, hypertensive nephropathy, and tubulointerstitial disease. The estimated glomerular filtration rate (eGFR) values were calculated and used to stage chronic kidney disease in these patients. Statistical analysis was carried out to find a correlation between diagnostic groups and CKD presence and between serum C3 values and immunofluorescence for the same on biopsy. Results One hundred thirty-two patients formed the study sample with a male to female ratio of 1.28:1, showing a slight male predominance. The most common diagnostic group was primary glomerular disease (46%), among which focal segmental glomerulosclerosis (FSGS) was the most common entity (12%). 47.7% and 66.6% of patients in the study sample showed elevated serum blood urea nitrogen (BUN) and creatinine values, respectively. 86% of our study sample had low eGFR values, and the majority (35%) of the patients were classified under CKD stage 3. CKD incidence was high among patients with primary glomerular diseases, but no significant statistical correlation was found. 43.5% of all IF positive cases showed low serum C3 values and established a positive correlation between IF and serum C3 values. Conclusion There is no statistically significant correlation of the four diagnostic groups to the CKD. CKD in the elderly may be multifactorial, and a collaborative study across the nations may be needed to further evaluate the etiology.

Keywords: chronic kidney disease; egfr; elderly; glomerular diseases; renal biopsy.

Figure 1. Gender distribution of the study sample showing a slight male predominance

M- Male; F- Female

Figure 2. Categorization of study subjects into four diagnostic groups.

PGD- Primary glomerular disease, DN- Diabetic nephropathy, HTN- Hypertensive nephropathy, TID- Tubulo-interstitial disease

Figure 3. H&E images of the most commonly encountered histopathology diagnoses in the study sample

IRGN- Infection-related glomerulonephritis, MGN- Membranous glomerulonephritis, DN- Diabetic nephropathy, HTN- Hypertensive nephropathy, TID- Tubulo-interstitial disease

Figure 4. Sub-categorization of tubulointerstitial diseases seen in the study sample

Figure 5. eGFR values (calculated using the MDRD equation) plotted on a graph.

The values highlighted in orange indicate the cases with low eGFR, implicating the burden of CKD in the study population. The MDRD equation image is downloaded from Google. eGFR- estimated glomerular filtration rate; MDRD- Modification of Renal Diet; CKD- Chronic Renal Disease; GFR- Glomerular filtration rate

Figure 6. Graph showing the distribution of grades of CKD among the cases in study sample.

Grading has been done according to the above-mentioned criteria, using eGFR values calculated on application of the MDRD equation. Majority of the cases in the study sample fall under CKD grade 3. eGFR- estimated glomerular filtration rate; MDRD- Modification of Renal Diet; CKD- Chronic Renal Disease; GFR- Glomerular filtration rate

Figure 7. Graph comparing the incidence and grades of CKD amongst the 4 diagnostic groups.

The highest incidence of CKD is noted in cases of primary glomerulopathy, amongst whom CKD grade 4 is the most common. DN- Diabetic nephropathy; HTN- Hypertensive nephropathy; TID- Tubulo-interstitial disease; PGD- Primary glomerular disease; CKD- Chronic kidney disease

Figure 8. Graph showing the distribution of serum C3 and C4 values among cases which show positive immunofluorescence

Serum C3 values highlighted in orange depict the cases showing a clinical correlation between low serum C3 values and positive immunofluorescence for C3 in renal biopsy.