Plasma and urinary metanephrine and normetanephrine concentrations using liquid chromatography with tandem mass spectrometry in healthy cats and in a cat with pheochromocytoma

Abstract

Background Pheochromocytoma (PCC) is rare in cats and plasma (PL) and urinary (U) metanephrines (metanephrine [MN]; normetanephrine [NMN]) measurement is rarely described in cats. Objectives We evaluated the utility of PL and U MNs measurement in 10 healthy cats and a cat with a confirmed diagnosis of pheochromocytoma (PheoCat), using liquid chromatography with tandem mass spectrometry (LC‐MS‐MS). Methods Urine and EDTA PL samples collected from each of the 10 cats and the PheoCat were promptly stored at −80°C and remained frozen until analysis. To evaluate U MNs stability, an additional urine sample collected from the healthy cats was refrigerated for 24 hours before freezing. Urinary creatinine concentration (Creat) was assessed using the same spot urine samples to calculate U MNs‐to‐creatinine ratios. Results The PL‐MN and PL‐NMN median concentrations of the healthy cats were 2.73 and 7.02 nmol/L, respectively. The median U‐MN/Creat and U‐NMN/Creat ratios were 70 and 139 μg/g, respectively. The PheoCat had a PL‐MN of 3.68 nmol/L, PL‐NMN of 66.27 nmol/L, U‐MN/Creat of 179 μg/g, and U‐NMN/Creat of 1262 μg/g. The PheoCat had markedly increased concentrations of both PL and U MNs when compared to the healthy cats. No significant difference was found between U MNs measured in urine samples that underwent 24 hours of refrigeration in comparison to those that were frozen immediately. Conclusions We report preliminary reference intervals for PL and U MNs in cats using LC‐MS‐MS and the potential clinical applicability of these biomarkers for the diagnosis of PCC in cats.

Adrenalectomy for the treatment of hypotension in a cat with phaeochromocytoma associated with caudal vena cava syndrome

“…Accordingly, its exact correlation with the blood pressure could not be determined. However, according to a recent study, cats with pheochromocytoma can indeed have reliably elevated levels of plasma and urinary catecholamines compared to healthy cats, indicating the potential clinical applicability of these biomarkers for the diagnosis of pheochromocytoma in cats in the future (Prego et al, 2023).…”

“…Phaeochromocytoma is an extremely rare tumour in cats, and few cases have been described (Calsyn et al, 2010;Chun et al, 1997;Henry et al, 1993;Patnaik et al, 1990;Prego et al, 2023). Most of the clinical signs associated with phaeochromocytoma result from excessive amounts of catecholamine secretion or the space-occupying nature of the tumour (Maher Jr & McNiel, 1997).…”