Management Status of Patients with Chronic Kidney Disease Across Medical Specialties in Japan: A Real-World Data Analysis

Chronic kidney disease (CKD) is a global health challenge leading to adverse renal and cardiovascular outcomes. Early identification is crucial to prevent disease progression and reduce mortality, but in clinical practice, CKD management approaches vary by medical specialty. Robust real-world investigations are needed to establish optimal strategies for early detection and intervention. This study assesses variability in CKD management across medical specialties in Japan, focusing on nephrology involvement, using large-scale electronic health record data.

This retrospective observational study analyzed electronic health records of 788,059 adults from approximately 200 hospitals in Japan between 2004 and 2021. Patients aged ≥18 years with at least two eGFR measurements below 90 mL/min/1.73 m², spaced 90–360 days apart, were included. We evaluated medical specialties, nephrology involvement, urine protein measurement (semi-quantitative/quantitative), eGFR and albuminuria stages, CKD diagnosis proportions, and proportions of comorbid heart failure and hypertension. Sensitivity analyses restricted to facilities with nephrology departments were performed to assess consistency of the results.

Nephrology was involved in care for only 9,104 patients (1.2%). Among other medical specialties, nephrology co-management proportions ranged from 0.7% to 1.0%. The highest proportion of male patients was seen in urology (75.1%), and the lowest in rheumatology (27.2%). Heart failure was common in cardiology (52.2%) and nephrology (37.7%), with a prevalence of 76.3% among those co-managed by both; hypertension was present in 65.2% of nephrology and 67.4% of cardiology patients (34.3% overall).
Semi-quantitative urine protein testing was performed in 63.2% of patients overall and 85.2% in nephrology. Nephrology involvement substantially increased testing proportions: cardiology (49.1% to 76.3%), rheumatology (78.2% to 96.9%), and endocrinology/metabolism (82.7% to 95.2%). Quantitative urine protein testing was carried out in 63.9% of nephrology patients with positive results, versus 7.3% to 20.0% in other specialties without nephrology, and 47.4% to 70.9% with nephrology involvement. CKD diagnosis proportions were 81.5% in nephrology and over 90% in advanced cases. Without nephrology involvement, CKD diagnosis proportions ranged from 10.0% to 25.6% among specialties, but increased to 87.2%–100% with nephrology involvement. Most patients (82.6%) were in G2, with nephrology co-management at 0.7%, rising to 15.6% in G4. Sensitivity analyses restricted to facilities with nephrology departments confirmed the consistency of these findings across specialties.

CKD management practices in Japan exhibit marked variability by specialty, with nephrology involvement associated with a higher proportion of urine protein assessment and greater frequency of CKD diagnosis, especially in early CKD. Most CKD patients are managed outside nephrology, where proportions of quantitative assessment and diagnosis are lower. Facility-specific strategies, including interdepartmental collaboration and standardized CKD protocols, are essential to improve early detection and intervention. As SGLT2 inhibitors become widely used for CKD, the importance of early diagnosis will continue to grow.