Chronic kidney disease of unknown aetiology: a real-world study

Background Diagnosis of rare chronic kidney disease (CKD) can be difficult with conventional diagnostic workup. When no diagnosis is identified, this is termed CKD of unknown aetiology (CKDUA). There are multiple benefits in obtaining a diagnosis in these cases. The advent and increasing availability of genetic testing in recent years has been a welcome additional diagnostic tool. In this study we aimed to determine the demographics, kidney related outcomes and predisposing factors for a cohort of patients with CKDUA within the Salford Kidney Study (SKS). Methods The SKS is a single-centre, ongoing, prospective, observational cohort study of adult patients referred to the renal service at Salford Royal Hospital, UK. Within the SKS there are 398 patients with CKDUA. A group with diabetic kidney disease (DKD) was used as a comparator. An analysis was performed comparing these two groups with a particular focus on their demographics and kidney related outcomes. Results median age of the CKDUA cohort was 71.4 years, with 60.1% male and 96.2% White. There was advanced CKD at presentation (median eGFR 30ml/min/1.73m ² ), with a 5-year mortality of 27.6%. When compared with the DKD cohort, the CKDUA cohort were older (71.4 years vs 67.3 years, p < 0.001), had more equal sex distribution (male 60.1% vs 68%, p < 0.009), had less advanced renal disease at presentation (eGFR 30ml/min/1.73m ² vs 26ml/min/1.73m ² ,p < 0.001), and were less likely to progress to renal replacement therapy (14.1% vs 28.2%, p < 0.001). Conclusions CKDUA is difficult to manage: other than general supportive measures there is little else that can be offered. This study reports on a real-world cohort of patients with CKDUA and identifies that in comparison to a DKD cohort their outcomes are improved.