Transrectal ultrasonography of the adrenal glands in donkeys (Equus asinus)

Little information is available for medical imaging in donkeys and no report about adrenal glands ultrasonography can be found in scientific literature. The feasibility of transrectal ultrasonography of the adrenal glands was tested on 30 healthy donkeys using a 10 MHz linear transducer. Mean age of animals was 10.7 ±4.8 years, mean weight 275.0 ±62.9 Kg and mean height 126.7 ±7.1 cm. The left adrenal gland was visualized in all donkeys. The right gland ultrasonography was not feasible in seven animals with a height less than 116 cm. The left gland was visualized as a linear or slightly curved structure, the right gland was most often S-shaped. In both glands, an hypechoic peripheral zone was identified as the cortex with an inner, hyperechoic medulla. The length was 5.49 ±1.90 cm and 5.15 ±1.10 cm for right and left gland, respectively. Right gland whole and medullary thickness were 0.71 ±0.11 cm and 0.24 ±0.09 cm, 0.65 ±0.13 cm and 0.21 ±0.07 cm, 0.56 ±0.17 cm and 0.25 ±0.07 cm for cranial pole, middle point and caudal pole respectively. Left gland whole and medullary thickness were 0.69 ±0.13 cm and 0.25 ±0.09 cm, 0.66 ±0.13 cm and 0.23 ±0.09 cm, 0.57 ±0.15 cm and 0.26 ±0.09 cm for cranial pole, middle point and caudal pole respectively. There was a significant correlation between height and the entire length of the left gland. Ultrasonography of the adrenal glands is a suitable tool for evaluation of both adrenal glands in most of the donkey. The size is a limiting factor for proper visualization of the right gland.