Abstract: FR-PO0903
A Dangerous Drop: Hypokalemia in a Patient on Pembrolizumab
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 1
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Collins-Ham, Claire, Henry Ford St John Hospital, Detroit, Michigan, United States
- Topf, Joel M., Oakland University William Beaumont School of Medicine, Rochester, Michigan, United States
Introduction
Immune checkpoint inhibitors (ICI) are used in the treatment of cancer. Hypokalemia is a known adverse effect of pembrolizumab and is often attributed to diarrhea. We report a case of hypokalemia due renal potassium wasting.
Case Description
A 50 year old male with a history of esophageal cancer presented to the hospital with generalized weakness for 10 days. He was on chemotherapy with leucovorin, fluorouracil, and oxaliplatin for 5 months prior to initiation of pembrolizumab. Within a month of starting pembrolizumab he developed hypokalemia.
Initial labs showed a potassium of 1.8 mEq/L, CO2 of 11 mEq/L, anion gap of 20 mEq/L, magnesium of 1.8 mg/dL. He was given 80 mg of potassium chloride and 2 g of magnesium sulfate. The repeat potassium was less than 1.5 mEq/L and the anion gap was 14 mEq/L. The fractional excretion of potassium was 19% and the potassium to creatinine ratio was 5.4 both consistent with increased renal potassium wasting. A VBG showed metabolic acidosis with respiratory compensation. He had a positive urinary anion gap (21.6 mmol/L), low urinary osmolar gap (47.2 mOsm/kg), and a urinalysis pH of 7.5 consistent with distal renal tubular acidosis (dRTA). He was admitted to the ICU, given potassium replacement with oral and IV potassium chloride, and started on prednisone.
Discussion
ICI have transformed care in oncology however they are associated with multiple immune related adverse events. While acute interstitial nephritis is the most commonly reported renal manifestation, dRTA has been reported.
The underlying mechanism of dRTA from ICI is thought to be due to immune mediated T cell infiltration that directly disrupts distal tubular acid secretion. Hallmark features of dRTA are non-anion gap metabolic acidosis, alkaline urine pH (> 5.5), hypokalemia, and nephrocalcinosis/nephrolithiasis.
Recommended management of ICI renal adverse events is to discontinue the medication, start corticosteroids, potassium and alkali supplementation. If there is no improvement in the electrolyte derangements after 5-7 days on corticosteroids, a renal biopsy should be pursued.
Hypokalemia in oncological patients is typically attributed to GI losses when present. Clinicians should be aware that hypokalemia in patients receiving new chemotherapy agents may not solely be due to GI losses but rather a direct effect on renal physiology.