LAUSR

Background: Little is known of the risks involved for patients who, at the start of lithium treatment, already have compromised renal function. Aims: To assess the risk of developing severe renal impairment (chronic kidney disease (CKD) 4–5) among those patients and to explore predictors for the progression. Methods: A retrospective longitudinal cohort study using data from Sahlgrenska University Hospital’s laboratory database 1981–2017. We compared the risk of developing CKD 4–5 in two patient cohorts: an exposed cohort of 83 patients who had high serum creatinine prior to start of lithium and a reference cohort of 83 patients with normal serum creatinine, matched by gender, duration of lithium treatment and age at the start of lithium treatment. The patients’ medical charts were reviewed and the Swedish Renal Registry was used to identify patients with renal replacement therapy. Results: There were no significant differences between the exposed and reference cohorts with respect to our matching criteria. Almost half the patients in the exposed cohort versus only 10% of the reference patients progressed to CKD 4–5 (HR 6.7, 95%CI 3.1–14.3, p < 0.001) during a mean observation time of more than 10 years. The progressors were older at the start of lithium treatment and were characterised by a higher burden of comorbid somatic diseases, in particular cardiovascular diseases. Conclusions: Compromised renal function prior to initiating lithium treatment increases the risk of developing severe renal impairment. Monitoring of renal function should include somatic comorbidity among older patients.