Reference intervals of urinary metanephrines: creatinine ratios in dogs: comparison of acidified and non-acidified samples collected by cystocentesis

Canine pheochromocytomas remain difficult to diagnose, and reports of RIs for urinary metanephrines (metanephrine and normetanephrine) are scarce. Prior urinary metanephrines:creatinine (uMNs:Cr) ratio RIs are reported with free metanephrines and apply only to voided urine samples. We recruited 40 subclinical client-owned and staff-owned dogs from a veterinary hospital. Among those, 38 dogs were considered healthy based on normal bloodwork and adrenal glands of normal size on ultrasonographic examination. uMNs:Cr ratios were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) on urine samples collected by ultrasound-guided cystocentesis. We found no statistical difference between acidified and non-acidified urine samples. The RIs were 17-117 for the total metanephrine:Cr ratio and 37-223 nmol/mmol for the normetanephrine:Cr ratio. We confirmed that acidification of urine is not necessary. uMNs:Cr ratios can be measured in urine collected by cystocentesis. Metanephrines measurements should be included when investigating a suspicion of pheochromocytoma in dogs and can be requested easily by veterinarians in general practice.