Ultrasound evaluation of adrenal gland size in clinically healthy dogs and in dogs with hyperadrenocorticism

Background: Precise reference intervals of adrenal gland thickness are required for detection of adrenomegaly in dogs with hyperadrenocorticism (HAC). Methods: Eighty‐six clinically healthy dogs were prospectively included, and 91 dogs with untreated HAC were retrospectively evaluated. Dorso‐ventral adrenal gland thickness was ultrasonographically measured on the sagittal plane. Dogs were classified into four body weight categories, and those with HAC were also ultrasonographically classified as consistent with pituitary‐dependent HAC (PDH), adrenal‐dependent HAC (FAT), equivocal adrenal asymmetry (EAA), or normal adrenal thickness. Results: The upper limits for left adrenal gland in clinically healthy dogs were 5.1 mm (≥2.5–5 kg), 5.5 mm (>5–10 kg), 6.4 mm (>10–20 kg), and 7.3 mm (>20–40 kg), and for right adrenal gland the upper limits were 5.3 mm (≥2.5–5 kg), 6.8 mm (>5–10 kg), 7.5 mm (>10–20 kg), and 8.7 mm (>20–40 kg). The sensitivity of ultrasound to detect adrenomegaly in dogs with HAC was 95.6%. Most dogs with HAC (56.0%) had ultrasound findings consistent with either PDH or FAT; however, EAA was commonly occurring in 39.6% of dogs with HAC. Conclusions: The sensitivity of ultrasonography to detect adrenomegaly in dogs with HAC is high when using four weight categories. EAA is common in dogs with HAC.