Transrectal Ultrasonography of the Left Adrenal Gland in Healthy Horses

Abstract

Little information is available on medical imaging of the adrenal glands in horses. We investigated the feasibility of transrectal ultrasonography to characterize the normal equine adrenal gland. Transrectal ultrasonography was performed in 25 healthy horses using a 7.5 MHz linear array probe at a displayed depth of 8 cm. Transrectal ultrasonography of the right adrenal gland was not feasible. For the left adrenal gland, the left kidney, the abdominal aorta, the left renal artery, the left renal vein, and the cranial mesenteric artery were used as landmarks. The size of the left adrenal gland was variable, but it generally appeared as a long, flat structure with a hyperechoic medulla surrounded by a hypoechoic cortex. The most cranial part of the gland could not be delineated appropriately in 11 horses (44%). The mean (+/-SD) thickness of the gland and medulla was 0.66 +/- 0.15cm (n = 25) and 0.28 +/- 0.09 cm (n = 25) near the caudal pole, 0.87 +/- 0.25 cm (n = 14) and 0.40 +/- 0.18 cm (n = 12) near the cranial pole, and 0.89 +/- 0.18 cm (n = 25) and 0.36 +/- 0.13 cm (n = 25) in the middle of the gland, respectively. The mean (+/-SD) length of the entire adrenal gland and of the medulla was 6.22 +/- 0.77 cm (n = 14) and 5.45 +/- 0.71 cm (n = 6), respectively. Transrectal ultrasonography allowed adequate visualization of the left adrenal gland in horses.

Feochromocytoma bij een paard met polymorfe ventriculaire tachycardie

“…Unfortunately, the normal right adrenal gland cannot be visualized by rectal ultrasonography in most horses. The deep abdominal location of the adrenal glands in adult horses makes it hard to use transabdominal ultrasonography for diagnostic imaging (Durie et al, 2010). By a rectal approach, the left adrenal gland potentially can be rectally palpated and visualized by ultrasound.…”

“…As in the present case, the tumor is often missed (Buckingham, 1970;Froscher, 1982;Johnson, et al, 1995;Yovich, 1983), due to the cranial position or an inappropriate inspection or palpation of this abdominal region, especially in an instable patient. If a presumptive diagnosis of an abdominal mass is made by rectal examination, rectal ultrasound can be used to examine the morphology of the mass (Durie et al, 2010;Johnson et al, 1995). A normal equine adrenal gland has a length of 7-8 cm, a mean thickness of 0.6-1.6 cm and a width of 2.4-4.5 cm (Durie et al, 2010).…”

“…A hemorrhagic mass (5 x 3 cm) was found at the craniomedial aspect of the left kidney. The neoplastic adrenal gland was not enlarged (reference length: 7-8 cm, width: 2.4-4.5 cm, thickness: 0.6-1.6 cm) (Durie et al, 2010). Multiple petechiae were found on the pleura, spleen, mesentery and coronary vessels.…”

“…The sudden onset of the severe, non-specific clinical signs makes it difficult to make the diagnosis before necropsy (Luethy et al, 2016). Ante mortem diagnosis can sometimes be made by the combination of the clinical signs, including especially profuse sweating with tachycardia in absence of colic, enteritis or septicemia, coccygeal blood pressure measurement, abdominocentesis, determination of circulating serum catecholamines and their urinary metabolites, rectal examination or transrectal ultrasonography (Durie et al, 2010;Johnson et al, 1995;Luethy et al, 2016;Wilson et al, 1986). In this case report, a twenty-fouryear-old horse with acute polymorphic ventricular tachycardia due to a functional pheochromocytoma is described.…”

Sonografische Topografie abdominaler Organe und Strukturen beim equinen Neonaten

“…Die transabdominale Sonografie der Nebenniere ist beim adulten Pferd aufgrund der dazu erforderlichen Eindringtiefe der Schallwellen nicht möglich. Transrektal lässt sich die linke Nebenniere gut darstellen, die rechte aufgrund ihrer weiter kranialen Lokalisation nicht [13]. Beim Fohlen wird die Nebenniere nicht standardmäßig dargestellt.…”