Morphological and clinical findings in Sri Lankan patients with chronic kidney disease of unknown cause (CKDu): Similarities and differences with Mesoamerican Nephropathy

<div><p>In Sri Lanka, an endemic of chronic kidney disease of unknown origin (CKDu) is affecting rural communities. The endemic has similarities with Mesoamerican Nephropathy (MeN) in Central America, however it has not yet been clarified if the endemics are related diagnostic entities. We designed this study of kidney biopsies from patients with CKDu in Sri Lanka to compare with MeN morphology. Eleven patients with CKDu were recruited at the General Hospital, Polonnaruwa, using similar inclusion and exclusion criteria as our previous MeN studies. Inclusion criteria were 20–65 years of age and plasma creatinine 100–220 μmol/L. Exclusion criteria were diabetes mellitus, uncontrolled hypertension and albuminuria >1g/24h. Kidney biopsies, blood and urine samples were collected, and participants answered a questionnaire. Included participants were between 27–61 years of age and had a mean eGFR of 38±14 ml/min/1.73m². Main findings in the biopsies were chronic glomerular and tubulointerstitial damage with glomerulosclerosis (8–75%), glomerular hypertrophy and mild to moderate tubulointerstitial changes. The morphology was more heterogeneous and interstitial inflammation and vascular changes were more common compared to our previous studies of MeN. In two patients the biopsies showed morphological signs of acute pyelonephritis but urine cultures were negative. Electrolyte disturbances with low levels of serum sodium, potassium, and/or magnesium were common. In the urine, only four patients displayed albuminuria, but many patients exhibited elevated α-1-microglobulin and magnesium levels. This is the first study reporting detailed biochemical and clinical data together with renal morphology, including electron microscopy, from Sri Lankan patients with CKDu. Our data show that there are many similarities in the biochemical and morphological profile of the CKDu endemics in Central America and Sri Lanka, supporting a common etiology. However, there are differences, such as a more mixed morphology, more interstitial inflammation and vascular changes in Sri Lankan patients.</p></div

Light microscopy images of tubulointerstitial pathology in patients with CKDu in Sri Lanka.

<p>Mild to moderate interstitial fibrosis was found in most patients (black arrow heads in A). Tubular atrophy was mostly mild (black arrows in B). Interstitial inflammation was of varying degree ranging from none to severe (B, A, D and C). Signs of pyelonephritis with interstitial inflammation and neutrophil granulocytes in tubules were found in two patients (white arrow heads in D). [Fig A: Ladewig from Patient 7, bar = 200μm. Fig B: periodic acid Schiff from Patient 4, bar = 100μm. Fig C: hematoxylin-eosin from Patient 3, bar = 100μm. Fig D: hematoxylin-eosin from Patient 11, bar = 100μm.].</p

Urine test results including urine heavy metals, n = 11.

<p>Urine test results including urine heavy metals, n = 11.</p

Patient characteristics and questionnaire results of working history, n = 11.

<p>Patient characteristics and questionnaire results of working history, n = 11.</p

Serum test results, n = 11.

<p>Serum test results, n = 11.</p

Questionnaire results of chronic diseases and medicine use.

<p>Questionnaire results of chronic diseases and medicine use.</p

Transmission electron microscopy findings.

<p>Segmental podocytic foot process effacement was observed in two patients (A, Patient 4). Podocytic cytoplasm inclusions of vacuoles or lipofuscin-like-bodies (arrows in B, Patient 6) were found in the majority of the patients. c = capillary, pc = podocyte. Bars = (A) 2μm, (B) 5 μm.</p

Light microscopy images of vascular pathology in Sri Lankan patients with CKDu.

<p>Most of the biopsies showed no or mild intimal fibrosis in arteries (arrow head in A). Three patients showed moderate intimal fibrosis (B). [Fig A: hematoxylin-eosin from Patient 6, bar = 100μm. Fig B: hematoxylin-eosin from Patient 3, bar = 100μm.].</p

Summary of renal morphology findings by light and electron microscopy.

<p>Summary of renal morphology findings by light and electron microscopy.</p