ULTRASONOGRAPHIC EVALUATION OF ADRENAL GLAND SIZE COMPARED TO BODY WEIGHT IN NORMAL DOGS

The accepted cut‐off value for adrenal gland maximum diameter of 0.74 cm to distinguish adrenal gland enlargement in dogs regardless of body weight may not be appropriate for small to medium breed dogs. The purpose of the current retrospective study was to examine adrenal gland dimensions as a function of body weight in healthy dogs in three weight categories (< 10 kg, 10–30 kg, and > 30 kg) representing small, medium, and large breeds, respectively, to establish greater confidence in determining if adrenal gland size is abnormal. The measurements of length (sagittal plane), cranial and caudal pole thickness (sagittal and transverse planes), and caudal pole width (transverse plane) of both adrenal glands were obtained ultrasonographically in clinically healthy dogs (n = 45) with 15 dogs in each weight group. Findings support our hypothesis that adrenal gland size correlates with body weight in normal dogs, and more precise reference intervals should be created for adrenal gland size by categorizing dogs as small, medium, or large breed. The caudal pole thickness of either adrenal gland in a sagittal plane was the best dimension for evaluating adrenal gland size based on low variability, ease, and reliability in measurement.     

Ultrasonographic visualization of the adrenal glands of healthy ferrets and ferrets with hyperadrenocorticism

A protocol was developed to compare the ultrasonographic characteristics of the adrenal glands of 21 healthy ferrets and 37 ferrets with hyperadrenocorticism. By using specific landmarks, the adrenal glands were imaged in 97% of the cases. The adrenal glands of ferrets with hyperadrenocorticism had a significantly increased thickness, with changes in shape, structure, and echogenicity compared to the adrenal glands of healthy ferrets. Based on the findings of the study, adrenal glands may be classified as abnormal when they have a rounded appearance, increased size of the cranial/caudal pole (thickness >3.9 mm), a heterogeneous structure, increased echogenicity, and/or signs of mineralization.     

Ultrasonographic evaluation of the adrenal glands in six dogs with hypoadrenocorticism.

The purpose of this study was to determine the value of ultrasonographic characterization of the adrenal glands in dogs with hypoadrenocorticism. Measurements of adrenal glands were obtained in six dogs with hypoadrenocorticism. The adrenal glands on both sides were shorter (range: left adrenal gland length, 10.0 to 19.7 mm; right adrenal gland length, 9.5 to 18.8 mm) and thinner (range: left adrenal gland thickness, 2.2 to 3.0 mm; right adrenal gland thickness, 2.2 to 3.4 mm) than in normal dogs (range: left adrenal gland length, 13.2 to 26.3 mm; right adrenal gland length, 12.4 to 22.6 mm; left adrenal gland thickness, 3.0 to 5.2 mm; right adrenal gland thickness, 3.1 to 6.0 mm). Statistical analysis revealed a significant reduction in size of the left adrenal gland (p less than 0.05) in dogs with hypoadrenocorticism compared to the left adrenal gland in normal dogs. The results of this study show that atrophy of the adrenal glands in dogs with hypoadrenocorticism seems to lead to an ultrasonographic-measurable reduction in size of the adrenal glands.     

MAGNETIC RESONANCE IMAGING OF THE PRESUMED NORMAL CANINE ADRENAL GLANDS

Forty-three dogs without evidence of endocrine disease that underwent spinal or abdominal magnetic resonance imaging (MRI) for clinical reasons were studied. Because the procedures were not optimized for inclusion of the adrenal glands, they were not always visible in all planes. Eighty-five of the 86 adrenal glands were seen and only the left gland in a 6-month-old Irish wolfhound could not be found. The right adrenal gland lay cranial to the left in all of the animals in which both glands were seen. The best landmarks for localization of the glands were vascular; both adrenal glands were always cranial to the ipsilateral renal vessels and in the region of the celiac and cranial mesenteric arteries. Various measurements were made on all the available scan planes. In some dogs the whole adrenal gland was difficult to visualize clearly, and this hindered the measuring process, especially when the right adrenal gland was in close contact with the caudal vena cava. The adrenal glands were mainly linear in shape but also had a variable degree of modification of their poles, especially the cranial pole of the right adrenal gland, which tended to be consistently wider and to present different shapes (rounded, arrowhead, inverted P, hook-shaped, triangular, or dome-shaped). Two main patterns of signal intensity were seen on fast spin echo (FSE) sequences (T2-weighted, T1-weighted, and T1-weighted after administration of a paramagnetic contrast medium): homogeneous and hypointense to surroundings or a corticomedullary type pattern with a hyperintense central area surrounded by a hypointense rim of tissue. The outline of the left adrenal gland was always very clear. The clarity of outline of the right adrenal gland was more variable, especially if it was in contact with the liver or the caudal vena cava. It was felt that the amount of retroperitoneal fat was not as important as stated in the human literature for visualization of the adrenal glands and that with an appropriate selection of scan planes and pulse sequences good assessment of the adrenal glands can be performed with MRI in canine patients.     

INTRA‐ AND INTEROBSERVER VARIABILITY OF ULTRASONOGRAPHIC MEASUREMENTS OF THE ADRENAL GLANDS IN HEALTHY BEAGLES

The aim of the present study was to establish which adrenal gland measurement was characterized by the least variations. To do this, we quantified the variability of seven different size measurements of the canine adrenal gland (maximal length, maximal height at the cranial and caudal poles on longitudinal and transverse images, and maximal width of the cranial and caudal poles) within observer, between observer, and between dogs based on three different measurements made by each of the three observers in six healthy Beagle dogs. The height of the caudal pole of both adrenal glands measured on longitudinal images had the lowest intra‐ and interobserver variability, while measurements of the length had the highest intra‐ and interobserver variability. Other measurements that were characterized by low intra‐ and interobserver variability were: height and width of the caudal pole on transverse images and height of the cranial pole on longitudinal images only. These results provide a basis for further study of the changes in adrenal gland size in dogs with pituitary‐dependent hyperadrenocorticism.     

Effects of mitotane therapy in dogs with pituitary dependent Cushing syndrome on the adrenal gland size--an ultrasonographic study]

The effect of mitotane therapy on adrenal gland size was evaluated in 13 dogs with pituitary dependent hyperadrenocorticism. Ultrasonographic measurements were obtained before and during mitotane therapy. During therapy both adrenal glands were shorter and thinner (median during therapy: left adrenal gland 19.4 mm long, 5.4 mm thick, right adrenal gland 18.1 mm long, 6.1 mm thick) than before mitotane therapy (median before therapy: left adrenal gland 23.6 mm long, 8.3 mm thick, right adrenal gland 21.6 mm long, 8.1 mm thick). Statistical evaluation showed a significant reduction in size. But ultrasonographic measurement of adrenal gland size is not useful in the evaluation of adrenal reserve during mitotane therapy. Inadequate adrenal reserve was not identified and adrenal size measurement by ultrasonography was not helpful to differentiate adequate and inadequate control of adrenal cortisol secretion during mitotane therapy.     

Ultrasonographic evaluation of the size of the adrenal glands of 24 diseased cats without endocrinopathies

The ultrasonographic measurements of the adrenal glands of 24 diseased cats without a clinically or laboratory identifiable endocrinopathy were evaluated retrospectively. The mean (sd) thickness of the left adrenal glands was 3.8 (0.8) mm and their mean length was 11.3 (2.8) mm; the thickness of the right glands was 4.5 (1.0) mm and their length was 9.8 (2.4) mm. The products of thickness and length were 43.9 (20.2) mm(2) for the left gland and 45.7 (19.7) mm(2) for the right gland. There were no significant correlations between the bodyweight, body surface area or body condition scores of the cats and the thickness, length or the product of thickness and length of either gland.     

CHANGES IN ULTRASONOGRAPHIC APPEARANCE OF ADRENAL GLANDS IN DOGS WITH PITUITARY-DEPENDENT HYPERADRENOCORTICISM TREATED WITH TRILOSTANE

Trilostane, a 3beta-hydroxysteroid dehydrogenase inhibitor, has been used successfully over the last few years for the treatment of canine pituitary-dependent hyperadrenocorticism. In a prospective study of 19 dogs with pituitary-dependent hyperadrenocorticism, the adrenal glands were measured before and at least 6 months after initiation of trilostane therapy. Right adrenal gland length and caudal pole thickness and left adrenal gland caudal pole thickness increased significantly (p < or = 0.05); there was no significant change in left adrenal gland length. Enlargement of adrenal glands during trilostane therapy may occur as a result of suppression of the negative feedback mechanism affecting cortisol production.     

TRANSRECTAL ULTRASONOGRAPHY OF THE LEFT ADRENAL GLAND IN HEALTHY HORSES

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±0.15 cm (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.     

Effect of glucocorticoid administration on adrenal gland size and sonographic appearance in beagle dogs

Our aim was to evaluate the influence of glucocorticoids on the adrenal gland using ultrasonography. Eleven healthy beagles were used in a prospective placebo-controlled study. All dogs received hydrocortisone at 10 mg/kg twice a day per os for 4 months or a gelatin capsule twice a day per os as a placebo. Clinical and endocrinologic examination of the dogs and ultrasonographic evaluation of adrenal echogenicity, shape, and measurement of the length and height of the cranial and caudal pole were performed at baseline (TO), at 1 (T1) and 4 months (T4) after the beginning of treatment, and 2 months after the end of the treatment including 1 month of tapering and 1 month without treatment (T6). The dogs were assigned randomly to the glucocorticoid (n = 6) and placebo groups (n = 5). At T1, the difference between the two groups for the height of the cranial and caudal pole was not ultrasonographically remarkable despite a statistically significant difference (P = 0.0165 and P = 0.0206). Decreased height and length of entire gland were observed at T4 (P < 0.0001, P = 0.0015, and P = 0.0035, respectively). Percentages of atrophy were variable between dogs. Both adrenal glands regained normal size and shape 1 month after cessation of glucocorticoid administration. As not all dogs developed marked adrenal gland atrophy and the degree of atrophy varied widely between individuals, ultrasonography cannot be the technique of choice to detect iatrogenic hypercortisolism. Ultrasonographic changes are reversible within 1 month after the end of glucocorticoid administration.     

Ultrasonographic Adrenal Gland Measurements in Healthy Yorkshire Terriers and Labrador Retrievers

An upper threshold of 7.4 mm for maximal adrenal gland diameter is commonly used to detect pituitary‐dependent hyperadrenocorticism ultrasonographically in dogs. There is a substantial overlap between adrenal gland diameter of healthy dogs and of those with pituitary‐dependent hyperadrenocorticism. The aim of this study is to determine the measurements of both adrenal glands, in particular, of the height at the caudal glandular pole in a longitudinal plane, in the Labrador retriever and Yorkshire terrier, two breeds widely represented in the population suspected of hyperadrenocorticism. Seventeen Labrador retrievers and 24 Yorkshire terriers considered healthy were included in the study. Adrenal gland measurements were taken on static images and comprised in measurements of the length in a longitudinal plane (L), of the height at the cranial (CrHLG) and caudal pole (CdHLG) in a longitudinal plane and in a transverse plane (CrHTR and CdHTR, respectively), and of the width at the cranial and caudal poles in a transverse plane (CrWTR and CdWTR, respectively). This study established new upper thresholds for the left and right height at the caudal pole measured in a longitudinal plane: 7.9 mm (left) and 9.5 mm (right) for the Labrador retrievers and 5.4 mm (left) and 6.7 mm (right) for the Yorkshire terriers. All the measurements were significantly different between the two breeds. There was a significant relationship between CdHTR and CdHLG, and the age of the dogs for both breeds.     

Evaluating the correlation between adrenal gland dimensions and aortic diameter in healthy dogs

In the present study, the relationship of normal adrenal dimensions with weight, aortic diameter, age and sex was evaluated. Moreover, a formula for estimating the normal dimensions of adrenal gland was provided. Thirty‐two intact adult dogs that were considered healthy based on history, physical examination, routine blood works and specific adrenal tests as well as absence of any abnormal ultrasonographic findings were included. Adrenal glands and abdominal aorta were imaged in the sagittal plane by ultrasound. Length, maximal height of the cranial and caudal poles, area and circumference of the left and right adrenal glands and also the internal diameter of the abdominal aorta were measured. Analysis showed that there is a positive correlation between the adrenal gland dimensions and weight and aortic diameter. The ratio of adrenal gland dimensions and the aortic diameter was calculated, but this ratio showed a great amount of variability in tandem with a significant correlation to the weight; Meaning that the ratio of the adrenal gland dimensions to the aortic diameter was not a reliable index for evaluating the size of the normal adrenal gland in animals with different weights. Therefore, we used the weight along with adrenal measurements in a linear regression model, and then, we were able to estimate the adrenal gland dimensions in different weights. Knowing the relationship of normal adrenal dimensions with the indices such as weight, age, sex and diameter of abdominal aorta can help the clinicians to diagnose the adrenal gland diseases.     

Ultrasonographic measurements of adrenal glands in cats with hyperthyroidism

Feline hyperthyroidism is potentially associated with exaggerated responsiveness of the adrenal gland cortex. The adrenal glands of 23 hyperthyroid cats were examined ultrasonographically and compared to the adrenal glands of 30 control cats. Ten hyperthyroid cats had received antithyroid drugs until 2 weeks before sonography, the other 13 were untreated. There was no difference in adrenal gland shape between healthy and hyperthyroid cats: bean-shaped, well-defined, hypoechoic structures surrounded by a hyperechoic halo in 43/60 (71.6%) healthy cats and 34/46 (73.9%) hyperthyroid cats; more ovoid in 13/60 (21.6%) healthy cats and 9/46 (19.6%) hyperthyroid cats while more elongated in 4/60 (6.7%) healthy cats, 3/46 (6.5%) hyperthyroid cats. Hyperechoic foci were present in 9/23 (39.1%) hyperthyroid cats and 2/30 (6.7%) healthy cats. The adrenal glands were significantly larger in hyperthyroid cats, although there was overlap in size range. The mean difference between hyperthyroid cats and healthy cats was 1.6 and 1.7 mm in left and right adrenal gland length, 0.8 and 0.9 mm in left and right cranial adrenal gland height, and 0.4 and 0.9 mm in left and right caudal adrenal gland height. There was no significant difference between the adrenal gland measurements in treated and untreated hyperthyroid cats. The adrenomegaly was most likely associated with the hypersecretion of the adrenal cortex documented in hyperthyroid cats. Hyperthyroidism should be an alternative to hyperadrenocorticism, hyperaldosteronism, and acromegaly in cats with bilateral moderate adrenomegaly.     

ULTRASONOGRAPHIC PARAMETERS OF NORMAL CANINE ADRENAL GLANDS: COMPARISON TO NECROPSY FINDINGS

Ultrasonographic evaluation of the adrenal glands was performed in 14 fasted healthy adult dogs. Frequency of visualization was 100% for both the left and right adrenal glands. Moderate correlation was present between Ultrasonographic and gross measurements of thickness for both left (r_s= 0.727; p < .005) and right (r_s= 0.537; p < .05) adrenal glands. However, no correlation was found between Ultrasonographic and gross measurements for length or width of either adrenal gland. Differentiation of adrenal cortex and medulla was possible in 79% of left adrenal glands and 64% of right adrenal glands. The echogenicity of the adrenal glands was less than that of the renal cortex in all dogs. Factors which made evaluation of the adrenal glands more difficult included pyloric gas, intestinal gas, and deep-chested body conformation.     

Arterial Vascularization and Morphological Characteristics of Adrenal Glands in the Pampas Deer (Ozotoceros bezoarticus,Linnaeus 1758)

This research presents morphological characteristics of adrenal glands and a demonstration of arterial vascularization in the Pampas deer, which is considered to be in extreme danger of extinction. A total of ten deer constituted the material of the study. Vascularization of organs was investigated by using latex injection technique. Left adrenal glands were basically supplied by coeliac, cranial mesenteric, renal and lumbal arteries. The arterial vascularization of the left adrenal glands was very complex in comparison with right adrenal glands. In two examples, branch of the lumbal artery was divided into phrenic caudal artery and cranial adrenal artery. In six examples, it was observed that the caudomedial and ventral regions of the left adrenal glands were also supplied by thinner branches that stemmed from second left lumbal artery. Besides, coeliac and cranial mesenteric arteries also gave off shorter branches supplying the cranial region of the left adrenal glands in five examples. It was determined that two branches originated from abdominal aorta directly for supplying left adrenal glands in only two examples. In four examples, two caudal adrenal arteries stemmed separately from left renal artery in a short distance. Arterial vascularization of right adrenal glands was more constant and supplied by lumbal and renal arteries. The adrenal glands were generally oval or round shaped. In only two examples, left adrenal glands were ‘V‐’ or heart‐shaped. There was no significant difference (P > 0.05) in sizes between right and left adrenal glands.     

ADRENAL ULTRASONOGRAPHY IN THE DOG

The ultrasonographic appearance of the normal canine adrenal gland has not been described. This is due to the small size and shape of the canine adrenal glands, overlying abdominal viscera, similar acoustic texture to that of the surrounding tissue, frequent abundant perirenal fat, and the lack of patient compliance. Adrenal enlargement in association with hyperadrenocorticism, secondary to hyperplasia or neoplasia, can sometimes be identified by finding a distinct structure cranial and/or medial to the cranial pole of either kidney. Case history reports are used to characterize the appearance of adrenal enlargement from hyperplasia and adrenocortical adenocarcinoma. Additional case history reports are included to illustrate possible interpretation problems. Lack of ultrasonographic visualization of the adrenal gland does not rule out the possibility of enlargement, particularly if the enlargement in mild.     

ULTRASONOGRAPHY OF ADRENAL GLANDS IN NORMAL FERRETS

The adrenal glands of 20 normal ferrets were imaged with ultrasound. Of the forty glands, only 4 (three right and one left) could not be clearly identified. Mean (±standard deviation) dimensions of the right (7.6 ± 1.8 mm length by 2.6 ± 0.4 mm width) and left (7.2 ± 1.8 mm length by 2.8 ± 0.5 mm width) glands were similar. Both adrenal glands were wider (p<0.05) sonographically in males than females. Measured length and width of the right gland positively correlated (p<0.05) with body weight. The glands had a hypoechoic outer zone and hyperechoic central region, were elongate to avoid in shape and located medial and, variably, at the level of the cranial pole of the ipsilateral kidney. This study demonstrates that normal adrenal glands can be imaged in ferrets.     

Ultrasonographic measurement of the adrenal gland-to-abdominal aortic ratio as a valuable method of estimating normal adrenal size in rabbits

A wide range has been reported for the ultrasonographic measurements of the normal adrenal gland in rabbits. Therefore, having sufficient information about the normal measurements of the adrenal gland and their relationship with indicators such as weight, sex and the diameter of the internal abdominal aorta will be of great help in diagnosing diseases of the adrenal gland. In the present study, 21 healthy adult intact rabbits were selected. The abdominal cavity of the animals was examined using ultrasound; adrenal gland parameters such as length, width, height, circumference and area on the right and left sides were measured in both sagittal and transverse planes. Additionally, the diameter of the abdominal aorta in the sagittal plane was imaged. After statistical analysis, the parameters of the adrenal glands on the right and left showed a positive significant correlation with the weight and the diameter of the abdominal aorta, although no significant correlation was found between these parameters and sex. The ratio of adrenal gland parameters to abdominal aortic diameter was calculated and the statistical analysis of the values showed that, except for the ratio of left adrenal area to aortic diameter, the other ratio of adrenal gland parameters to abdominal aortic diameter was not significantly related to weight. Therefore, these ratios can be used as suitable indicators for assessing the change in size of the adrenal gland of rabbits of different sizes. Knowing the relationship between normal adrenal measurements and the indices such as weight, sex and diameter of the abdominal aorta can help clinicians and researchers evaluate the changes in the size of the adrenal gland.     

Dimensional ultrasonographic relationship of the right lobe of pancreas with associated anatomic landmarks in clinically normal dogs

The purpose of this prospective study was to establish the ultrasonographic characteristics of the dimension of the right pancreatic lobe with that of the associated anatomic landmarks in healthy dogs. Ultrasonographic examinations were performed on 25 dogs. The thickness of the right pancreatic lobe was compared with that of mural thickness of duodenum, diameter of duodenum, pancreatic duct, abdominal aorta, portal vein, caudal vena cava, and length and width of the right kidney and right adrenal gland. The correlation between each pancreatic parameter and the dimensions of the anatomical landmarks were assessed using linear regression analysis and Pearson’s correlation coefficient (r) test. Significant, but weak linear correlations were observed between thickness of right pancreatic lobe with that of duodenum mural thickness (r=0.605, R²=0.339, P=0.001); duodenum diameter (r=0.573, R²=0.299, P=0.003); and right adrenal gland length (r=0.508, R²=0.052, P=0.01). There was no significant dimensional relationship with other selected anatomic landmarks. The ratio between the thickness of right pancreatic lobe and the mural thickness of duodenum, diameter of duodenum and length of right adrenal gland were 2.88 ± 0.53, 1.27 ± 0.27 and 0.81 ± 0.15, respectively. Calculating the ratio of thickness of the right pancreatic lobe with the dimension of significantly correlated anatomic landmarks is a useful and simple method for evaluating the size of the right pancreatic lobe in dogs in clinical practice.