Endemic chronic kidney disease of unknown etiology in Sri Lanka: Correlation of pathology with clinical stages

Abstract

Chronic kidney disease of unknown etiology (CKDU) is endemic among the rural farming communities in several localities in and around the North Central region of Sri Lanka. This is an interstitial type renal disease and typically has an insidious onset and slow progression. This study was conducted to identify the pathological features in the different clinical stages of CKDU. This is a retrospective study of 251 renal biopsies identified to have a primary interstitial disease from regions endemic for CKDU. Pathological features were assessed and graded in relation to the clinical stage. The mean age of those affected by endemic CKDU was 37.3 ± 12.5 years and the male to female ratio was 3.3:1. The predominant feature of stage I disease was mild and moderate interstitial fibrosis; most did not have interstitial inflammation. The typical stage II disease had moderate interstitial fibrosis with or without mild interstitial inflammation. Stage III disease had moderate and severe interstitial fibrosis, moderate interstitial inflammation, tubular atrophy and some glomerulosclerosis. Stage IV disease typically had severe interstitial fibrosis and inflammation, tubular atrophy and glomerulosclerosis. The mean age of patients with stage I disease (27 ± 10.8 years) was significantly lower than those of the other stages. About 79.2%, 55%, 49.1% and 50% in stage I, II, III and IV disease respectively were asymptomatic at the time of biopsy.

Keywords: Endemic chronic kidney disease of unknown etiology in Sri Lanka; interstitial fibrosis; interstitial renal disease.

Figure 1

A map of Sri Lanka showing areas known to be endemic for chronic kidney disease of unknown etiology. The shaded area is the North Central Province

Figure 2

Pathological features of the endemic chronic kidney disease in Sri Lanka: (a) Stage I disease (Masson trichrome stain), areas of fibrosis stained in blue (10 × 10); (b) stage I disease (H and E): interstitial fibrosis with a few atrophic tubules. There is minimal inflammation (10 × 10); (c) stage III disease: interstitial fibrosis, multifocal tubular atrophy and multifocal infiltrations of mononuclear inflammatory cells (10 × 10), (d) stage IV disease: extensive interstitial fibrosis, tubular atrophy, diffuse mononuclear inflammatory cell infiltration and glomerular sclerosis (10 × 10). (Clinical staging is according to clinical practice guidelines of the National Kidney foundation. The clinical stages are as follows: stage I, glomerular filtration rate (GFR) >90 ml/min; stage II, GFR 60–89 ml/min, stage III, GFR 30–59 ml/min, stage IV, GFR 15–29 ml/min and stage V, GFR <15 ml/min)

Figure 3

Mean age against the clinical stage of the disease (clinical staging is according to clinical practice guidelines of the National Kidney foundation)