Value of “Active” Urine Sediment Examination in Predicting Proliferative Glomerular Pathology on Kidney Biopsy

Key Points A good urine sediment examination corelated with clinical history can predict whether the patient has a glomerular or tubular pathology. Increase in dysmorphic red blood cells and other formed elements in urine sediment correlates with degree of proliferation in kidney biopsy. Active urine sediments are indicative of a proliferative glomerular pathology and inactive urine sediments are indicative of a non-proliferative glomerular pathology. Background Urine sediment examination is an important preliminary investigation for the nephrologist and helps them decide whether the patient has a proliferative or nonproliferative glomerular pathology. Recently, there is an increasing trend of using easier, nonspecific dipstick method for urine examination leading to a decline in the importance of urine sediment examination. Here, we attempt to define guidelines for biochemical and microscopic parameters to develop a uniform and clinically relevant reporting system for urine sediment examination. Methods Urine samples were reported as inactive or active sediment. A tiered system of reporting urine sediments was developed including inactive sediment, inactive sediment with moderate/significant proteinuria, glomerular hematuria, and active sediment, active sediment with significant proteinuria/features of proliferative activity. The urine sediment was compared with kidney biopsies of these patients, which were grouped into nonproliferative and proliferative glomerulopathy. Results Seven hundred and ninety-five paired samples of urine sediment and kidney biopsies were examined and compared. Patients of nonproliferative glomerulopathy (minimal change disease, FSGS, amyloid and membranous nephropathy) showed features of inactive sediment. Patients with proliferative glomerulopathy (focal proliferative GN, diffuse proliferative GN, membranoproliferative GN, mesangio-proliferative GN, and crescentic GN) predominantly showed active sediment, with increase in percentage of dysmorphic red blood cells and formed elements. The sensitivity of this urine reporting system was 82.0%, specificity 74.4% with P value <0.001. Conclusions This system of reporting urine sediment is a sensitive and efficient method for predicting the severity of underlying kidney disease and need for performing renal biopsy.