Refractory Hyperkalemia With Type 4 Renal Tubular Acidosis Associated With Tubulointerstitial Nephritis and Renal...

To describe type 4 renal tubular acidosis (RTA) and acquired pseudohypoaldosteronism in a cat with acute kidney injury (AKI) presumably associated with lipid infusion therapy for permethrin toxicosis.

A 1-year-old neutered male cat presented with acute weakness, ataxia, fasciculations, tremors, hyperthermia, and seizures resulting from permethrin toxicosis. Upon admission, IV diazepam and 20% IV lipid emulsion were administered. Forty-eight hours after discharge, the patient was readmitted for lethargy, anorexia, polyuria, and vomiting. Upon admission, the patient exhibited signs of depression, dehydration, and moderate hypoperfusion. Initial assessments included CBC, serum biochemistry profile, and urinalysis. Further diagnostic workup and abdominal point-of-care ultrasound revealed clinical findings compatible with AKI. Laboratory analysis confirmed severe hyperkalemia, hyperchloremic normal anion gap metabolic acidosis, decreased fractional excretion of potassium, and decreased transtubular potassium gradient in the urine, all consistent with a diagnosis of secondary or acquired pseudohypoaldosteronism and type 4 RTA. Emergency medical treatment for hyperkalemia was initiated, but control of serum potassium concentration was unsuccessful. Peritoneal dialysis (PD) and general supportive care were initiated 24 h after admission. Mineralocorticoid support (continuous rate infusion of hydrocortisone) was initiated 4 days after admission due to suspected deficiency/resistance to aldosterone at the distal nephron. Unfortunately, despite PD, refractory hyperkalemia persisted, and the cat died 16 days after admission. Histopathological examination confirmed an acute and severe renal papillary necrosis.

To the authors' knowledge, this is the first description of type 4 RTA in a cat. Furthermore, we hypothesize that, according to the histopathological findings, this presentation of AKI may be secondary to the use of IV lipid emulsion for permethrin toxicosis, a complication not previously reported in the veterinary literature.