Sonographically Determined Renal Size and Echogenicity as a Predictor of Chronic Irreversible Renal Parenchymal Disease in Glomerulonephritis Patients: Comparison with Histopathology

Author(s): Dr. Md. Tamim Aziz, Prof. Dr. Md. Nizamuddin Chowdhury, Dr. Md Abdul Hakim, Dr. Md. Safayet Hossain Pramanik, Dr. Md. Saeed Hossain, Dr. Md. Shoriful Islam

Background:

Renal biopsy remains the gold standard investigation for evaluation of glomerular disease but causes complications in small kidneys and shows chronic changes at histopathology, which are usually non-responsive to treatment. On the other hand, renal sonography is frequently used to judge irreversible renal parenchymal disease, but clinically valuable thresholds have never been established. Specific pathologic changes in renal histopathology that increased cortical echogenicity at sonography have not been defined. Our objective is to correlate renal sonographic parameters with the histopathology of glomerulonephritis and to establish thresholds for renal size and echogenicity that could be useful in making clinical decisions about irreversible renal parenchymal disease in tertiary care hospitals.

Aim of the study:

To assess the correlation between sonographic findings and renal histopathology of glomerulonephritis.

Methods:

This cross-sectional study was done in the Department of Nephrology of Dhaka Medical College and Hospital (DMCH) over 18 months. As per the inclusion and exclusion criteria, 94 fulfilled the criteria for inclusion. Later, a radiologist did renal sonography, and a biopsy was done. One renal histopathologist evaluated the pathologic findings; 92 patients had completed histopathological diagnosis,1 had only histopathological diagnosis, and one patient’s biopsy sample was inadequate. Then, sonographic parameters (length, echogenicity, and cortical thickness) were compared to biopsy findings of glomerular sclerosis, tubular atrophy, interstitial fibrosis, and interstitial inflammation, and data analysis was done by SPSS version 22.

Result:

Renal cortical echogenicity showed the best correlation with all histopathological parameters, and the r values for glomerular sclerosis, tubular atrophy, interstitial fibrosis, and interstitial inflammation were 0.380,0.741,0.761 and 0.320, respectively(p<0.05). Multivariate analysis showed that only interstitial inflammation (acute and reversible condition) was a significant independent contributor to echogenicity(p<0.05). Kidney length significantly correlated negatively with glomerular sclerosis, tubular atrophy, and interstitial fibrosis; their r values were -0.638, -0.401, and -0.385, respectively (p<0.05). Cortical thickness significantly correlated negatively with glomerular sclerosis, tubular atrophy, and interstitial fibrosis; r values were -0.356, -0.245, and -0.230, respectively (p<0.05). Severe chronic kidney disease (>50% sclerosed glomeruli or a score of 3 out of 5 or greater for tubular atrophy or interstitial fibrosis at enal histopathology) was present in 62.5% and 8.8% of cases when kidney length <9cm and ≥9cm respectively (p<0.001). When cortical echogenicity ≤ liver and >liver severe disease was present in 2.1% and 44.4% cases, respectively (p<0.001). When kidney length ≥9 cm, echogenicity ≤ liver severe chronic kidney disease was present in 0% of cases (p <0.001). However, together, kidney length <9 cm and echogenicity > liver can predict severe chronic kidney disease in 82.4% of cases (p <0.001) with 77% sensitivity, 95% specificity, a PPV 82%, NPV 94.66% with 92% accuracy.

Conclusion:

Cortical echogenicity correlates with histopathology, increasing in acute and chronic conditions. Renal size or echogenicity alone are poor predictors but good predictors of chronic irreversible renal parenchymal disease.