Adrenal gland ultrasonography is primarily useful in the diagnosis of hyperadrenocorticism, hyperaldosteronism, hypoadrenocorticism, and adrenal neuroendocrine tumors. However, studies have reported variable ultrasonographic values in adrenal gland measurement, and there is little knowledge substantiating the reliability of such measurements. Measurement errors can be classified as either systematic (operator or machine-dependent) or random. This study assessed which adrenal gland measurements were characterized by the smallest amount of variation by evaluating intraobserver/interobserver variability of ultrasonographic adrenal gland measurements. Healthy beagle dogs (n = 6) were used in the study, and each adrenal gland was scanned 3 times by 3 individuals trained in abdominal ultrasonography. A total of 7 different size measurements were evaluated (maximal length, maximal height at the cranial and caudal poles on longitudinal and transverse images, and maximal width of the cranial and caudal poles) by observers, between observers, and between dogs. Longitudinal image measurements of the caudal adrenal gland pole height demonstrated the lowest intraobserver/interobserver variability. Length measurements demonstrated the highest intraobserver/interobserver variability. Measurements of the caudal pole height and width measurements on transverse images and height of the cranial pole on longitudinal images were characterized by low intraobserver/interobserver variability.
Commentary: This publication scientifically demonstrates that normal, healthy dogs of similar size and conformation will demonstrate variation in ultrasonographic measurements of adrenal glands. The adrenal glands are often difficult to find ultrasonographically and to measure accurately, partially due to their shape. The left gland is “peanut” shaped with 2 distinct lobes and an often longitudinal curve. The right gland is “arrowhead” shaped and can be more difficult to locate due to its more cranial location; it is also frequently obscured by the colon. I often tell referring veterinarians and clients that ultrasonography alone should not be the sole diagnostic modality for diagnosing adrenal disease. While statistical calculations are important in scientific evaluations, some readers may find the information presented somewhat difficult to decipher because of the statistical calculation, but the overall contents are important to review and understand.—Jean Reichle, DVM, MS, Diplomate ACVR
Intra- and interobserver variability of ultrasonographic measurements of the adrenal glands in healthy beagles. Barberet V, Pey P, Duchateau L, et al. VET RADIOL ULTRASOUND 51:656-660, 2010.