Two decades of chronic kidney disease of unknown aetiology (CKDu) research: Existing evidence and persistent gaps from epidemiological studies in Sri Lanka

A critical review of a hidden epidemic: examining the occupational and environmental risk factors of chronic kidney disease of unknown etiology (CKDu)

A form of chronic kidney disease has been described in people without any known risk factors. These cases are referred to as chronic kidney disease of an unknown etiology (CKDu).

Unraveling the enigma: chronic kidney disease of unknown etiology and its causative factors with a specific focus on dissolved organic compounds in groundwater-reviews and future prospects

Chronic kidney disease is globally recognized as a highly impactful non-communicable disease. The inability of early identification contributes to its high mortality rate and financial burden on affected individuals. Chronic kidney disease of uncertain etiology (CKDu) constitutes a significant global public health concern. This condition does not arise from traditional risk factors such as diabetes, hypertension, or glomerulonephritis. More than 150 articles were analysed to understand risk factors of CKDu. This study aimed to investigate the potential association between dissolved organic compounds, such as Polycyclic Aromatic Hydrocarbons and Humic Acid, and the incidence of CKDu. Through a comprehensive literature review, we identified CKDu clusters worldwide, including notable nephropathies, and explored their potential links with organic compounds. Our analysis revealed that organic compounds can leach from sediments and low-rank lignite deposits into groundwater, subsequently contaminating water supplies and food. These compounds have been implicated in the development of diabetes and increased heavy metal mobility, both of which are risk factors for kidney disease. Our findings suggest that exposure to organic compounds may contribute to the etiology of CKDu, underscoring the need for regular monitoring and establishment of baseline and threshold values in water and soil. We also emphasize the importance of analyzing organic compounds in groundwater in CKDu hotspots and establishing distinct registries for CKD and CKDu implementation.

Chemometric assessment of bioaccumulation and contamination pathways for toxic metals in diet and environment: implications for chronic kidney disease of unknown etiology (CKDu) in Sri Lankan agricultural regions

Prolonged consumption of foods containing toxic metals can elevate the risk of noncommunicable diseases, including chronic kidney disease of uncertain etiology (CKDu). Despite the increasing number of CKDu cases in Maradankulama and Mahakanadrawa Grama Niladhari Divisions (GN) in Sri Lanka, no prior studies have examined the accumulation of heavy metal(loid)s and their potential association with CKDu prevalence. Furthermore, there is an absence of comprehensive analyses using chemometric techniques such as PCA and hierarchical studies regarding CKDu and heavy metal contamination in Sri Lanka. This study aims to provide initial insights into the accumulation and potential pathways of toxic metals in staple foods within local diets and their subsequent presence in the agricultural environment of examined GNs. Cr, Cd, As, and Ni concentrations in analyzed foods were within permissible limits (MPLs), whereas Pb levels exceeded MPLs in rice (Oryza sativa), gotukola (Centella asiatica), lime (Citrus crenatifolia), and inland fish (Etroplus suratensis). High target hazard quotient (THQt) values in polished rice suggest possible health risks with prolonged intake. Hierarchical analysis suggested a common source of Pb accumulation. PCA and hierarchical clustering revealed the intricate connection between As and Cd, with their concurrent clustering in samples suggesting a potential common origin. This indicates that while individual concentrations comply with acceptable standards, the potential synergistic effects of Cd and As accumulation might pose elevated health risks. Further, the gut tissues of inland fish exhibited pronounced metal concentrations and significant (p < 0.05) positive correlations with toxic metals in the tank sediments suggesting a diet-based bioaccumulation pathway through sediments.

Tubulointerstitial nephropathy is the predominant finding in men in a review of more than 3000 renal biopsies over a 10-year period from Sri Lanka

BACKGROUND

Chronic kidney disease (CKD) is a significant clinical challenge in Sri Lanka. The present study presents histopathological diagnoses from native renal biopsies in Kandy District, 2011-2020.

METHODS

Reports of 5,014 renal biopsies principally performed at Kandy Teaching Hospital over 2011-2020 were reviewed. After exclusions for post-kidney transplant biopsies (1,572) and those without evident pathology (347), 3,095 biopsies were included. The predominant histopathological entities were grouped and categorised according to diagnosis and stratified by age and sex.

RESULTS

The main histopathological entities (all biopsies) were tubulointerstitial nephropathy (TIN) 25% (n = 760), glomerulonephritis (GN) 15% (467), lupus nephropathy 14% (429), focal segmental glomerular sclerosis (FSGS) 10% (297), and IgA nephropathy (IgAN) 8% (242). For adult women ≥ 15 years, the main histopathological entities were lupus nephropathy 24% (325), TIN 17% (228), and GN 16% (217). For adult men ≥ 15 years, the main histopathological entities were TIN 34% (449), GN 14% (180), and IgAN 10% (125). The proportion of TIN in the present study was higher than international studies of a similar size.

CONCLUSION

This is the largest study of renal biopsies reported from Sri Lanka to date. TIN was the most common diagnosis in adults ≥ 15 years at 25%. Notable sex differences showed TIN was the most common histopathology in men (34%) but not in women (17%). No previously published similar study of this size has found TIN as the predominant diagnosis amongst renal biopsies in men. Further research is required into the possible causes of these observations in Sri Lanka.

CLINICAL TRIAL NUMBER

Not applicable.

Burden of Chronic Kidney Disease of Undetermined Aetiology (CKDu) in a Tertiary Care Public Hospital in North India

INTRODUCTION

Chronic kidney disease of undetermined aetiology (CKDu) is an important public health problem. Indian data are mostly based on studies from rural regions in south and east India. We examined the burden and profile of CKDu in patients attending a tertiary care hospital in north India.

METHODS

We assessed records of consecutive new CKD patients registered in a nephrology clinic from January 2015 to June 2022. Patients were classified as having CKDu based on predefined inclusion and exclusion criteria. Clinical and laboratory parameters at presentation and kidney biopsy when done were noted.

RESULTS

Records of 32,369 patients with CKD were screened, and 29,663 were included (2,706 excluded due to inadequate data). A total of 370 (1.2%) patients were categorized as CKDu. Mean age was 41 ± 14.7 years, 58.1% being male. Of them, 158 (42.7%) patients were in CKD stage 3, 89 (24.1%) in stage 4, 84 (22.7%) in stage 5, and 39 (10.5%) were dialysis dependent at presentation; 232 (62.7%) patients had proteinuria <0.5 gm/day and 138 (37.3%) between 0.5 and 1 gm/day. Renal histology was available for 65 CKDu patients: 62 had chronic tubulointerstitial nephritis (CTIN) and 3 had non-specific changes.

CONCLUSION

When defined using strict criteria with intensive diagnostic workup, burden of CKDu is low in our hospital-based cohort of CKD patients. CTIN is the predominant histopathological finding in kidney biopsy.

Health burden of sugarcane burning on agricultural workers and nearby communities

Sugarcane is the most widely cultivated crop in the world, with equatorial developing nations performing most of this agriculture. Burning sugarcane is a common practice to facilitate harvest, producing extremely high volumes of respirable particulate matter in the process. These emissions are known to have deleterious effects on agricultural workers and nearby communities, but the extent of this exposure and potential toxicity remain poorly characterized. As the epidemicof chronic kidney disease of an unknown etiology (CKDu) and its associated mortality continue to increase along with respiratory distress, there is an urgent need to investigate the causes, determine viable interventions to mitigate disease andimprove outcomes for groups experiencing disproportionate impact. The goal of this review is to establish the state of available literature, summarize what is known in terms of human health risk, and provide recommendations for what areas should be prioritized in research.

Occupational risks associated with chronic kidney disease of non-traditional origin (CKDnt) in Brazil: it is time to dig deeper into a neglected problem

In the past decades, an epidemic of chronic kidney disease (CKD) has been associated with environmental and occupational factors (heat stress from high workloads in hot temperatures and exposure to chemicals, such as pesticides and metals), which has been termed CKD of non-traditional origin (CKDnt). This descriptive review aims to present recent evidence about heat stress, pesticides, and metals as possible causes of CKDnt and provide an overview of the related Brazilian regulation, enforcement, and health surveillance strategies. Brazilian workers are commonly exposed to extreme heat conditions and other CKDnt risk factors, including increasing exposure to pesticides and metals. Furthermore, there is a lack of adequate regulation (and enforcement), public policies, and strategies to protect the kidney health of workers, considering the main risk factors. CKDnt is likely to be a significant cause of CKD in Brazil, since CKD's etiology is unknown in many patients and several conditions for its development are present in the country. Further epidemiological studies may be conducted to explore causal associations and estimate the impact of heat, pesticides, and metals on CKDnt in Brazil. Moreover, public policies should prioritize reducing workers´ exposure and promoting their health and safety.

Chronic kidney disease of unknown aetiology in Africa: A review of the literature

During the last two decades, an epidemic of a severe form of chronic kidney disease (CKD) unrelated to traditional risk factors (diabetes and hypertension) has been recognized in low- to middle-income countries. CKD of unknown aetiology (CKDu) mainly affects young working-age adults, and has become as an important and devastating public health issue. CKDu is a multifactorial disease with associated genetic and environmental risk factors. This review summarizes the current epidemiological evidence on the burden of CKDu and its probable environmental risk factors contributing to CKD in Africa. PubMed/Medline and the African Journals Online databases were searched to identify relevant population-based studies published in the last two decades. In the general population, the burden of CKD attributable to CKDu varied from 19.4% to 79%. Epidemiologic studies have established that environmental factors, including genetics, infectious agents, rural residence, low socioeconomic status, malnutrition, agricultural practise and exposure to agrochemicals, heavy metals, use of traditional herbs, and contaminated water sources or food contribute to the burden of CKD in the region. There is a great need for epidemiological studies exploring the true burden of CKDu and unique geographical distribution, and the role of environmental factors in the development of CKD/CKDu.

Metabolome evidence of CKDu risks after chronic exposure to simulated Sri Lanka drinking water in zebrafish

It is still a serious public health issue that chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka poses challenges in identification, prevention, and treatment. What environmental factors in drinking water cause kidney damage remains unclear. This study aimed to investigate the risks of various environmental factors that may induce CKDu, including water hardness, fluoride (HF), heavy metals (HM), microcystin-LR (MC-LR), and their combined exposure (HFMM). The research focused on comprehensive metabolome analysis, and correlation with transcriptomic and gut microbiota changes. Results revealed that chronic exposure led to kidney damage and pancreatic toxicity in adult zebrafish. Metabolomics profiling showed significant alterations in biochemical processes, with enriched metabolic pathways of oxidative phosphorylation, folate biosynthesis, arachidonic acid metabolism, FoxO signaling pathway, lysosome, pyruvate metabolism, and purine metabolism. The network analysis revealed significant changes in metabolites associated with renal function and diseases, including 20-Hydroxy-LTE4, PS(18:0/22:2(13Z,16Z)), Neuromedin N, 20-Oxo-Leukotriene E4, and phenol sulfate, which are involved in the fatty acyls and glycerophospholipids class. These metabolites were closely associated with the disrupted gut bacteria of g_ZOR0006, g_Pseudomonas, g_Tsukamurella, g_Cetobacterium, g_Flavobacterium, which belonged to dominant phyla of Firmicutes and Proteobacteria, etc., and differentially expressed genes (DEGs) such as egln3, ca2, jun, slc2a1b, and gls2b in zebrafish. Exploratory omics analyses revealed the shared significantly changed pathways in transcriptome and metabolome like calcium signaling and necroptosis, suggesting potential biomarkers for assessing kidney disease.

Kidney Disease and Proteomics: A Recent Overview of a Useful Tool for Improving Early Diagnosis

Kidney disease is a critical and potentially life-threatening degenerative condition that poses a significant global public health challenge due to its elevated rates of morbidity and mortality. It manifests primarily in two distinct clinical forms: acute kidney injury (AKI) and chronic kidney disease (CKD). The development of these conditions hinges on a multitude of factors, including the etiological agents and the presence of coexisting medical conditions. Despite disparities in their underlying pathogenic mechanisms, both AKI and CKD can progress to end-stage kidney disease (ESKD). This advanced stage is characterized by organ failure and its associated complications, greatly increasing the risk of mortality. There is an urgent need to delve into the pathogenic mechanisms underlying these diseases and to identify novel biomarkers that can facilitate earlier diagnosis. Such early detection is crucial for enhancing the efficacy of therapy and impeding disease progression. In this context, proteomic approaches have emerged as invaluable tools for uncovering potential new markers of different pathological conditions, including kidney diseases. In this chapter, we overview the recent discoveries achieved through diverse proteomic techniques aimed at identifying novel molecules that may play a pivotal role in kidney diseases such as diabetic kidney disease (DKD), IgA nephropathy (IgAN), CKD of unknown origin (CKDu), autosomal dominant polycystic kidney disease (ADPKD), lupus nephritis (LN), hypertensive nephropathy (HN), and COVID-19-associated acute kidney injury (COVID-AKI).

The politics of glyphosate regulation: lessons from Sri Lanka's short-lived ban

BACKGROUND

Glyphosate is the world's most used herbicide and a central component of modern industrial agriculture. It has also been linked to a variety of negative health and environmental effects. For instance, the International Agency for Research on Cancer classified glyphosate as "probably carcinogenic to humans" in 2015. This has motivated widespread political demands for stricter glyphosate regulation but so far few governments have followed through.

METHODS

We conduct a case study of Sri Lanka, which in 2015 became the first and so far only country in the world to adopt and implement a complete glyphosate ban. But this ban proved to be short-lived, as it was partially reversed in 2018 (and later fully revoked in 2022). To explain the political causes of Sri Lanka's pioneering glyphosate ban and its subsequent reversal, we employ process tracing methods drawing on publicly available documents. Our analysis is theoretically guided by the multiple streams framework and the concept of self-undermining policy feedback.

RESULTS

Glyphosate regulation rose to the top of the Sri Lankan political agenda in 2014 when a local scientist linked glyphosate exposure to an epidemic of Chronic Kidney Disease of Unknown Origin (CKDu). A glyphosate ban was eventually adopted in June 2015 by the newly elected government of Maithripala Sirisena. The ban was a political commitment made to the Buddhist monk Rathana Thero and his party, which had supported Sirisena during his presidential campaign. The ban's partial reversal in 2018, implemented through sectoral exceptions, was the result of continued lobbying by export-oriented plantation industries and increased political concerns about potential negative effects on the large and structurally powerful tea sector. The reversal was further aided by the scientific community's failure to corroborate the hypothesized link between glyphosate and CKDu.

CONCLUSIONS

The case of Sri Lanka suggests that strict glyphosate regulation becomes more likely when coupled with locally salient health risks and when decision-making authority is de-delegated from regulatory agencies back to the political executive. Meanwhile, the short-lived nature of the Sri Lankan ban suggests that strict glyphosate regulation faces political sustainability threats, as the apparent lack of cost-effective alternative herbicides motivates persistent business lobbying for regulatory reversal.

Food-mediated exposure of Hofmeister ions in Oryza sativa (Rice) from selected CKDu endemic regions in Sri Lanka

The objectives of this study were to determine selected Hofmeister anions and cations that are important for kidney health, in raw rice samples from selected Chronic Kidney Disease of unknown etiology (CKDu) endemic and non-endemic areas in Sri Lanka and their intake. The anions and cations were analyzed by Ion Chromatography and Microwave Plasma Atomic Emission Spectrometry (MP-AES), respectively, after alkaline and acid digestion in thirty raw rice samples each from CKDu endemic and non-endemic areas, and the dietary intake was estimated. The mean concentrations of fluoride (F-), chloride (Cl-), phosphate (PO43-), sulfate (SO42-), sodium (Na+), magnesium (Mg2+), potassium (K+), and calcium (Ca2+) in raw rice in CKDu endemic areas were 53.317, 1515.3, 2799.6, 2704.9, 30.603, 300.76, 1001.3, and 90.075 mg/kg, respectively. The mean concentration of the anions and cations in raw rice from CKDu non-endemic areas were 22.850, 947.52, 4418.7, 6080.2, 23.862, 364.45, 955.78, and 96.780 mg/kg, respectively. Significantly higher differences (p < 0.05) were reported in the mean concentration of F-, Cl-, and Na+ in raw rice from CKDu endemic areas in comparison with the samples from non-endemic areas. The aggregated estimated daily intake (EDI) and cumulative EDI of F- via consumption of cooked non-traditional samba rice from CKDu endemic areas for adults were the highest (0.155 and 0.172 mg/kg bw/d, respectively), which were higher than the recommended tolerable upper intake value (0.15-0.2 mg/kg bw/d). In contrast, the traditional rice from CKDu non-endemic areas for adolescents, reported the lowest values (0.0210 and 0.0470 mg/kg bw/d, respectively). Adults who consume non-traditional samba rice from CKDu endemic areas were at health risk, while children were the most vulnerable group due to their low body weight. These results indicate that the consumption of rice rich in Hofmeister ions may contribute to the total intake and act as risk factors to negatively affect weak kidneys in CKDu endemic areas. Further research to analyze Hofmeister ions in cooked rice and rice from different countries is recommended.

Sugarcane ash and sugarcane ash-derived silica nanoparticles alter cellular metabolism in human proximal tubular kidney cells

Multiple epidemics of chronic kidney disease of an unknown etiology (CKDu) have emerged in agricultural communities around the world. Many factors have been posited as potential contributors, but a primary cause has yet to be identified and the disease is considered likely multifactorial. Sugarcane workers are largely impacted by disease leading to the hypothesis that exposure to sugarcane ash produced during the burning and harvest of sugarcane could contribute to CKDu. Estimated exposure levels of particles under 10 μm (PM10) have been found to be exceptionally high during this process, exceeding 100 μg/m3 during sugarcane cutting and averaging ∼1800 μg/m3 during pre-harvest burns. Sugarcane stalks consist of ∼80% amorphous silica and generate nano-sized silica particles (∼200 nm) following burning. A human proximal convoluted tubule (PCT) cell line was subjected to treatments ranging in concentration from 0.025 μg/mL to 25 μg/mL of sugarcane ash, desilicated sugarcane ash, sugarcane ash-derived silica nanoparticles (SAD SiNPs) or manufactured pristine 200 nm silica nanoparticles. The combination of heat stress and sugarcane ash exposure on PCT cell responses was also assessed. Following 6-48 h of exposure, mitochondrial activity and viability were found to be significantly reduced when exposed to SAD SiNPs at concentrations 2.5 μg/mL or higher. Oxygen consumption rate (OCR) and pH changes suggested significant alteration to cellular metabolism across treatments as early as 6 h following exposure. SAD SiNPs were found to inhibit mitochondrial function, reduce ATP generation, increase reliance on glycolysis, and reduce glycolytic reserve. Metabolomic analysis revealed several cellular energetics pathways (e.g., fatty acid metabolism, glycolysis, and TCA cycle) are significantly altered across ash-based treatments. Heat stress did not influence these responses. Such changes indicate that exposure to sugarcane ash and its derivatives can promote mitochondrial dysfunction and disrupt metabolic activity of human PCT cells.

Elucidating environmental factors and their combined effects on CKDu in Sri Lanka using zebrafish

Chronic kidney disease with uncertain etiology (CKDu) in Sri Lanka has attracted much attention as a global health issue. However, how environmental factors in local drinking water induce kidney damage in organisms is still elusive. We investigated multiple environmental factors including water hardness and fluoride (HF), heavy metals (HM), microcystin-LR (MC-LR), and their combined exposure (HFMM) to elucidate their toxic effects on CKDu risk in zebrafish. Acute exposure affected renal development and inhibited the fluorescence of Na, K-ATPase alpha1A4:GFP zebrafish kidney. Chronic exposure influenced the body weight of both genders of adult fish and induced kidney damage by histopathological analyses. Furthermore, the exposure significantly disturbed differential expression genes (DEGs), diversity and richness of gut microbiota, and critical metabolites related to renal functions. The transcriptomic analysis revealed that kidney-related DEGs were linked with renal cell carcinoma, proximal tubule bicarbonate reclamation, calcium signaling pathway, and HIF-1 signaling pathway. The significantly disrupted intestinal microbiota was closely related to the environmental factors and H&E score, which demonstrated the mechanisms of kidney risks. Notably, the Spearman correlation analysis indicated that the changed bacteria such as Pseudomonas, Paracoccus, and ZOR0006, etc were significantly connected to the DEGs and metabolites. Therefore, the assessment of multiple environmental factors provided new insights on "bio-markers" as potential therapies of the target signaling pathways, metabolites, and gut bacteria to monitor or protect residents from CKDu.

Chronic kidney disease with unknown cause across the global spectrum

PURPOSE OF REVIEW

In the 1990s, a type of chronic kidney disease with unknown cause (CKDu) was identified in Central America and Sri Lanka. Patients lacked hypertension, diabetes, glomerulonephritis, or other usual causes of kidney failure. Affected patients are predominantly male agricultural workers aged 20-60 years, living in economically disadvantaged areas with poor access to medical care. Patients typically present late and progress to end-stage kidney disease within 5 years, resulting in social and economic hardship for families, regions, and countries. This review covers the current state of knowledge for this disease.

RECENT FINDINGS

The prevalence of CKDu is increasing in known endemic regions and across the globe, reaching epidemic proportions. There is primary tubulointerstitial injury with secondary glomerular and vascular sclerosis. No definitive etiologic factors have been identified, and these may vary or overlap in different geographic locations. The leading hypotheses include exposure to agrochemicals, heavy metals and trace elements, and kidney injury from dehydration/heat stress. Infections and lifestyle factors may play a role, but are likely not key. Genetic and epigenetic factors are beginning to be explored.

SUMMARY

CKDu is a leading cause of premature death in young-to-middle-aged adults in endemic regions and has become a public health crisis. Studies are underway to investigate clinical, exposome, and omics factors, and hopefully will provide insights into pathogenetic mechanisms resulting in biomarker discovery, preventive measures, and therapeutics.

Kidney Health and Care: Current Status, Challenges, and Developments

The concept of chronic kidney disease (CKD) originated in the 2000s, and an estimated 850 million patients are currently suffering from health threats from different degrees of CKD. However, it is unclear whether the existing CKD care systems are optimal for improving patient prognosis and outcomes, so this review summarizes the burden, existing care models, effectiveness, challenges, and developments of CKD care. Even under the general care principles, there are still significant gaps in our understanding of the causes of CKD, prevention or care resources, and care burdens between countries worldwide. Receiving care from multidisciplinary teams rather than only a nephrologist shows potential profits in comprehensive and preferable outcomes. In addition, we propose a novel CKD care structure that combines modern technologies, biosensors, longitudinal data visualization, machine learning algorithms, and mobile care. The novel care structure could simultaneously change the care process, significantly reduce human contact, and make the vulnerable population less likely to be exposed to infectious diseases such as COVID-19. The information offered should be beneficial, allowing us to rethink future CKD care models and applications to reach the goals of health equality and sustainability.

Early Ultrastructural Changes in Biopsies From Patients With Symptomatic CKD of Uncertain Etiology

Introduction

Although the investigation of chronic kidney disease of uncertain etiology (CKDu) has identified many possible influencing factors in recent years, the exact pathomechanism of this disease remains unclear.

Methods

In this study, we collected 13 renal biopsies from patients with symptomatic CKDu (Sym-CKDu) from Sri Lanka with well-documented clinical and socioeconomic factors. We performed light microscopy and electron microscopic evaluation for ultrastructural analysis, which was compared with 100 biopsies from German patients with 20 different kidney diseases.

Results

Of the 13 Sri Lankan patients, 12 were men (92.3%), frequently employed in agriculture (50%), and experienced symptoms such as feeling feverish (83.3%), dysuria (83.3%), and arthralgia (66.6%). Light microscopic evaluation using activity and chronicity score revealed that cases represented early stages of CKDu except for 2 biopsies, which showed additional signs of diabetes. Most glomeruli showed only mild changes, such as podocyte foot process effacement on electron microscopy. We found a spectrum of early tubulointerstitial changes including partial loss of brush border in proximal tubules, detachment of tubular cells, enlarged vacuoles, and mitochondrial swelling associated with loss of cristae and dysmorphic lysosomes with electron-dense aggregates. None of these changes occurred exclusively in Sym-CKDu; however, they were significantly more frequent in these cases than in the control cohort.

Conclusion

In conclusion, our findings confirm the predominant and early alterations of tubular structure in CKDu that can occur without significant glomerular changes. The ultrastructural changes do not provide concrete evidence of the cause of CKDu but were significantly more frequent in Sym-CKDu than in the controls.