Renal function in lithium-treated patients: a survey of case notes

Impey, M, McCrea, P
Psychiatry Department, Rotherham General Hospital
PROBLEM: Treatment with lithium in psychiatric patients can last for many years, increasing the
risk of renal injury through nephrogenic diabetes insipidus and direct tissue damage. Renal function
monitoring during lithium treatment is now routine, and can be performed with serum creatinine or
estimated glomerular filtration rate (eGFR). The interpretation and utility of eGFR may not be clear to
psychiatrists. Is this a valuable measure to be using? Would it demonstrate different results to using
serum creatinine? And is the renal function of local lithium-treated patients impaired enough for us to
worry anyway?
PURPOSE: Firstly, to establish the degree of renal impairment in the local lithium-treated
population, in order to estimate the impact that changes in monitoring policy are likely to have.
Secondly, to compare the use of EGFR to the standard creatinine values which are usually produced
by laboratories, in order to find whether one is superior at detecting renal impairment in this
DESIGN: Sample group: All identifiable lithium-treated patients under secondary care mental health
services in the Rotherham area. Lists provided by individual consultant teams.
Data collection: Demographic and prescription data sampled directly from case notes. Creatinine and
eGFR results obtained from computerised lab records.
Analysis: descriptive by whole group and sub-groups for age and length of treatment. Descriptive
comparison made to previously published results.
1. 207 patients identified, 196 with appropriate notes available.
2. 171 patients (87%) had an eGFR below 90
41 (21%) had an eGFR in the stage 3a-5 chronic kidney disease (CKD) range.
3. Results compared to NEOERICA study, which has estimated the proportion of stage 3a-5
CKD in general adult population. Our study showed almost double the rate for women and
over double the rate for men in lithium-treated patients.
4. Increasing age related to higher proportion of CKD. Particular rise in 60+ age group.
5. Length of treatment had a roughly inverse relationship with eGFR.
6. CKD levels in our study for all age ranges were considerably lower than those found in a
previous study by Bassilos et. al., by a factor of 12 for the 20-39 age group
7. When renal function measures are compared, the proportion of patients with an EGFR below
60 is higher than the proportion with a creatinine level outside the reference range.
CONCLUSION: Lithium-treated patients were shown to have a higher proportion of chronic kidney
disease than would be expected in the general population, though a lower level than in other studies.
Age is likely to have been a major confounding factor. EGFR was shown to be more sensitive for
detecting reduced renal function than serum creatinine alone. The study suggests that eGFRs should
be made routine and evaluated as regularly by clinicians as other measures of renal function. This
information has been incorporated into local guidance for lithium monitoring, and should be
accompanied by clear instructions on how and when to refer for a specialist renal opinion.
RELEVANCE: Lithium remains a popular and effective medication in mental health. Regular
monitoring is now a standard practice but the most appropriate measures need to be used. EGFR is a
useful and sensitive estimation of renal function, which is more likely to be reduced in lithium treated
patients. EGFR is easy to incorporate into local practice, though more help is needed in interpretation
and onward referral.