Renal Ultrasound to Aid in Diagnosis of Lithium-Induced Nephrotoxicity: A Case Report

Introduction/Background:

Lithium has long been used for treatment of bipolar disorder. However, its long-term use has been associated with renal toxicity. Most well documented is arginine vasopressin resistance, which often is self-limiting. While most patients on lithium do not have chronic kidney disease (CKD), studies demonstrate a positive association between lithium use and CKD. Unfortunately, the risk of developing CKD remains increased even once patients discontinue lithium use. Renal damage typically can be observed histologically, requiring renal biopsy. However, radiographic findings may also be present, and an astute clinician may consider less-invasive imaging instead. This case highlights the diagnostic utility of ultrasound in suspected lithium-induced nephrotoxicity.

Description:

A 68-year-old male with bipolar disorder on lithium and ziprasidone and hypertension on lisinopril and amlodipine presented for annual follow-up. He was taking 600 mg lithium nightly for over 10 years and was tolerating his medications well. Baseline creatinine for the prior 2 years was in the 1.2 to 1.4 range. His creatinine worsened to 1.50, and a referral to nephrology was placed, who saw him 2 months later. Urinalysis was unrevealing and the patient denied any symptoms nor significant renal history. Given lithium use, bilateral renal ultrasound was obtained, demonstrating innumerable echogenic foci with small cysts bilaterally. These findings suggested lithium-induced renal injury, and the nephrologist attributed his CKD to longstanding hypertension and lithium use. Lithium was not discontinued, with management focused on blood pressure control instead. Follow-up ultrasound 6 months later demonstrated persistence of multifocal cysts and echogenic foci, with a plan to discuss lithium alternatives with psychiatry should CKD worsen.

Discussion:

This case demonstrates the use of renal ultrasound in patients suspected to have CKD from long-term lithium use. While lithium therapy was not discontinued for this patient, future therapeutic decisions may be guided by a known diagnosis of lithium-induced nephrotoxicity. In patients with this diagnosis, ultrasound often demonstrates numerous uniform microcysts with punctate echogenic foci. These findings may also be observed on abdominal CT or with T2-weighted MRI. As such, in patients on long-term lithium therapy with new or worsened CKD, a renal ultrasound may aid in the diagnosis of lithium-induced nephrotoxicity.