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Radiographic features of canine hyperadrenocorticism caused by autonomously functioning adrenocortical tumors: 23 cases (1978-1986)
Dominique G. Penninck, DVM; Edward C. Feldman, DVM; Thomas G. Nyland, DVM
Summary: Radiographic features of 23 dogs with functioning adrenocortical tumors are described. In 56% of the dogs, radiographic detection of adrenomegaly, with or without calcification, was an aid in the diagnosis of adrenocortical neoplasia. Adrenal gland calcification did not distinguish adrenocortical adenoma from carci- noma.
H yperadrenocorticism is a commonly diagnosed endocrinologic disorder in dogs. Hyperadre- nocorticism usually is suspected on the basis of results of initial laboratory evaluation of affected dogs.1.2 This suspicion can be confirmed by obtaining abnormal results of adrenocorticotropin (ACTH) stimulation or dexamethasone screening tests.3.4 Choice of treatment is aided by knowing whether an affected dog has pituitary-dependent hyperad- renocorticism or functioning adrenocortical tumor. Adrenocortical tumors should be excised,5,6 unless metastasis has preceded treatment. Dogs with pitu- itary-dependent hyperadrenocorticism most often are treated with mitotane (o,p-DDD)2,7 or, less commonly, by hypophysectomy.
Various diagnostic tools can be used to distin- guish between pituitary-dependent hyperadreno- corticism and hyperadrenocorticism caused by ad- renocortical tumor. Measurement of plasma ACTH concentration is reliable in differentiating between these 2 forms of the disease, but this test is not widely available.8 The high-dose dexamethasone suppression test commonly is used, but results of this test are not reliable in identifying dogs with adrenocortical tumors.8 In dogs, adrenal gland ultra- sonography is a useful technique to evaluate adre- nomegaly, and may be of help in differentiating adrenocortical neoplasia from adrenocortical hyper- plasia.9 Computed tomography and gamma camera
imaging also have been used to study the adrenal glands of dogs and appear to be reliable methods. 10-12 However, these 3 noninvasive imaging techniques are not yet widely available to practitioners; conse- quently, they will not be discussed.
Radiographically detectable adrenomegaly and/ or adrenal gland mineralization have been reported in dogs with adrenocortical carcinoma.13-16 Of 22 dogs with hyperadrenocorticism attributable to ad- renocortical tumor(s), 9 had unilateral adrenal gland calcification. The number of dogs with mineralized adenoma vs those with mineralized carcinoma was not reported.16
Results of abdominal radiography from 23 dogs with functioning adrenocortical tumor(s) were re- viewed. To determine whether radiography was a potential aid for diagnosing adrenocortical neoplasia, a careful search for adrenal gland mineralization was conducted.
Criteria for selection of cases
Twenty-three dogs with clinical signs of hyper- adrenocorticism caused by adrenocortical tumor(s) were radiographed at the teaching hospital between January 1978 and July 1986, and adrenocortical tumor(s) was ultimately diagnosed in each. Hyper- adrenocorticism initially was suspected from history and results of physical examination, hemogram, urinalysis, and serum biochemical analysis. The diagnosis of hyperadrenocorticism was made on the basis of results of ACTH stimulation and/or dexa- methasone screening studies.3
Adrenocortical tumor was suspected in each dog because of suppressed endogenous ACTH con- centration.6,8 The diagnosis of adrenocortical tumor was confirmed in each dog by histologic evaluation of tissue obtained during surgery from 13 dogs and at necropsy from 10 dogs.
Abdominal radiography, including lateral and ventrodorsal views, was performed on all dogs. Radiographs were evaluated for adrenal gland visu- alization, size, and calcification. Additionally, these radiographs were evaluated for liver size, calcinosis cutis and/or other ectopic soft tissue calcification, osteoporosis, and pendulous abdomen. The retro-
From the Veterinary Medical Teaching Hospital (Penninck) and the Departments of Reproduction (Feldman) and Radiological Sciences (Nyland), School of Veterinary Medicine, University of California, Davis, CA 95616.
Address reprint requests to Dr. Nyland.
peritoneal space was scrutinized for possible adreno- megaly with or without calcification. Adrenomegaly was identified by recognizing a discrete soft tissue opacity cranial and medial to the kidneys. The retroperitoneal space may be difficult to evaluate because of fluid-filled intestinal loops and/or super- imposition of soft tissue opacities, such as spleen and kidney shadows. Adrenomegaly and/or calcifi- cation were strongly suspected only if visualization of overlying structures could be eliminated by use of additional radiography, which was performed after enema administration or accompanied by ab- dominal compression using a radiolucent paddle. To determine the prevalence of adrenal gland calci- fication, comparative abdominal radiography was performed in a clinically normal canine population of the same mean age.
Generalized hepatomegaly17 was evaluated by the degree of caudal gastric displacement and/or the
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rounded appearance of the ventral hepatic silhouette (Fig 1). Hepatomegaly was classified subjectively as mild, moderate, or severe on the basis of appearance on the lateral view of the abdominal radiograph. Mild hepatomegaly was defined as slight caudal displacement of the pyloric antrum and mildly increased cranial-to-caudal dimension of the ventral portion of the liver. Moderate hepatomegaly was characterized by obvious caudodorsal displacement of the antrum, with overall increased size of the ventral portion of the liver. Severe hepatomegaly was defined as a massively large ventral portion of the liver, resulting in a horizontal position of the stomach on the lateral view of the abdominal radiograph.
Osteoporosis was identified subjectively when the radiopacity of the vertebral bodies contrasted obviously with the sclerotic endplates (Fig 1). Dys- trophic (ectopic) calcification was observed as cal- cified opacities in the subcutaneous tissue (calcinosis cutis; Fig 2). Pendulous abdomen was identified when marked distention of the abdominal cavity was observed (Fig 2).
Thoracic radiographs, obtained from 18 of the 23 dogs, were studied to identify bronchial calcifi- cation (Fig 3). For this finding, 3 categories were assigned: lack of calcification, calcification in the hilar area only, and calcification in the hilar and peripheral areas. To assess the prevalence of bron- chial calcification attributable to aging, comparative radiography was performed in a clinically normal canine population of the same mean age.
Results
Twenty-three dogs with hyperadrenocorticism caused by adrenocortical neoplasia were evaluated. The mean age was 11 years (range, 6 to 16 years).
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JAVMA, Vol 192, No. 11, June 1, 1988
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Of the 23 dogs, 13 were female, and a variety of breeds was represented. Thirteen of these dogs had radiographic evidence of adrenocortical calcification, which was confirmed histologically. Calcification was not identified histologically in any adrenocorti- cal tumor that did not appear calcified radiographi- cally. Of the 23 dogs, 10 had adrenocortical adenoma and 13 had adrenocortical carcinoma diagnosed histologically. Of the 10 dogs with adenoma, 6 (60%) had radiographically visible calcification of the adrenal gland mass (Fig 4), and 7 of the 13 with carcinoma (54%) had visibly calcified adrenal gland mass (Fig 5). As with any subjective study, some findings were subtle. In 2 dogs, calcified carcinoma was identified radiographically with some reserva- tion. Ultimately, radiographically subtle areas were diagnosed histologically as calcified adrenocortical
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neoplasia. Three dogs with calcified carcinoma also had swollen soft tissue detected radiographically. One dog with adenoma had radiographically visible swollen soft tissue without calcification, which was detected during intravenous pyelography.
In 4 dogs with adenoma, the right adrenal cortex was involved and in 5, the left was involved; 1 dog had bilateral adrenocortical adenomas. In addition to 1 dog with bilaterally calcified adenomas, 2 dogs had calcified right and 3 had calcified left adrenocortical adenoma (Fig 6 and 7). Carcinoma involved the right adrenal cortex in 5 dogs and the left in 8 dogs. Adrenal gland calcification was identified in 6 dogs with carcinoma of the left adrenal cortex and in 1 dog with carcinoma of the right adrenal cortex. In 3 dogs, adrenocortical carcinomas that were identified as suspicious for calcification included 2 involving the left adrenal gland and 1 involving the right.
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Of the 23 dogs, 21 (91%) had hepatomegaly, which was classified as mild in 6 dogs (26%), moderate in 12 (52%), and severe in 3 (13%). Osteoporosis was apparent in 3 dogs (13%), and pendulous abdomen was observed in 14 (60%). Calcinosis cutis (without any particular pattern) was seen in 4 dogs (17%) in the ventral abdominal and lumbar areas. Bronchial calcification was detected in
83% of the population, with 33% classified as having hilar calcification only, and 50% classified as having hilar and peripheral calcification; 17% did not have calcification. A comparative study of similarly aged dogs indicated that 85% had bronchial calcification, with 65% classified as hilar only and 20% classified as hilar and peripheral; 15% did not have calcifica- tion.
Discussion
The necessity to distinguish between causes of hyperadrenocorticism, ie, pituitary-dependent vs autonomously functioning adrenocortical tumor, was the stimulus for this study. A practical, reliable, cost-effective, and readily available diagnostic aid would benefit small animal practitioners. Abdominal radiography meets these criteria. Functioning adre- nocortical tumor is found in 10 to 20% of dogs with noniatrogenic hyperadrenocorticism.4,8,18 A dog with history and results of physical examination, CBC, serum biochemical analysis, and urinalysis that are consistent with this diagnosis should be studied further using screening tests for hyperadrenocorti- cism (ACTH stimulation and low-dose dexametha- sone tests).19 Abdominal radiography should be performed on dogs with abnormal screening test results. Such radiographs would identify the 50% of adrenocortical tumors that have calcified in all dogs with hyperadrenocorticism (15 to 20% of which have autonomously functioning adrenocortical tu- mors). This is a practical, available, cost-effective, and reliable diagnostic approach for use in affected dogs and should aid in developing a treatment plan.
On the basis of the authors’ experience and findings in dogs of comparable ages, adrenal gland calcification is uncommon in clinically normal dogs and in those with pituitary-dependent hyperadre-
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| of adrenal gland calcification in 23 dogs | ||
|---|---|---|
| Histopathologic diagnosis | Size (cm) and/or weight of adrenal gland mass | Radiographic calcification of adrenal gland |
| Adrenocortical adenoma, right | NA | Yes |
| Adenoma, right | NA | Yes |
| Adenoma, right | NA | No |
| Adenoma, right | 2.0×2.0×2.0 | No |
| Adenoma, left | NA | Yes |
| Adenoma, left | 5.0×2.0×2.0 | Yes |
| Adenoma, left | 3.5×2.5×2.5 | Yes |
| Adenoma, left | 3.3×2.2×2.2 (7.2 g) | No |
| Adenoma, left | 2.0×1.5×1.5 | No |
| Carcinoma, right | NA | Yes* |
| Carcinoma, right | 2.0×2.0×2.0 (5.6 g) | No |
| Carcinoma, right | 4.0× 3.5×1.2 | No |
| Carcinoma, right | 3.3 g | Na |
| Undifferentiated adrenocortical carcinoma, right | NA | No |
| Carcinoma, left | 4.0×5.0×2.5 | Yes |
| Carcinoma, left | NA | Yes |
| Carcinoma, left | NA | Yes |
| Carcinoma, left | 4.0×3.0×2.5 | Yes |
| Carcinoma, left | NA | Yes |
| Carcinoma, left | NA | Yes* |
| Carcinoma, left | 5.0×2.0×2.0 | No |
| Carcinoma, left | 10.0× 10.0 × 10.0 | No |
| Bilateral adenomas | NA | Yes |
| *Subtle. NA = not available. | ||
nocorticism. Therefore, the radiographic finding of calcification in the area of one or both adrenal glands in a dog with confirmed hyperadrenocorticism is highly suggestive of adrenocortical tumor. Exact measurement of adrenal gland size was available for 11 adrenocortical tumors (Table 1). Significant cor- relation could not be made between tumor size and malignant potential of the adrenal mass; however, the 5 large masses (≥4 cm) were carcinoma. Adenoma and carcinoma may calcify, and either adrenal gland can be identified radiographically. Abdominal radiography assisted with the diagnosis in approximately 50% (13/23) of dogs with adre- nocortical tumor(s).
Dogs with hyperadrenocorticism caused by functioning adrenocortical tumor(s) had many of the radiographic abnormalities generally described in association with the more common form, pitui- tary-dependent hyperadrenocorticism. In this study, prevalences of hepatomegaly (91%), calcinosis cutis (17%), and osteoporosis (13%) were in close agree- ment with those of a previous report.16 However, only 3 of the 48 dogs described in the earlier study had adrenocortical tumors (carcinoma). In our study, bronchial calcification was a nonspecific finding in clinically normal aging dogs and was not helpful in identifying hyperadrenocorticism. Pendulous abdo- men was better evaluated during physical examina- tion than by use of radiography.
Adrenomegaly without calcification was diffi-
cult to assess on survey radiographs, although it was suspected in one dog and then was identified in 2 dogs during intravenous pyelography to evaluate chronic urinary tract infection (Fig 7). In those 2 dogs, intravenous pyelography unexpectedly as- sisted in visualization of each adrenocortical neo- plasm, perhaps as a result of increased vasculariza- tion of the neoplasm. Because of the retrospective nature of this study, definitive conclusion was not established regarding the usefulness of radiography as a diagnostic aid for identifying adrenocortical tumors. Application of this technique to dogs with suspected adrenocortical mass warrants further study.
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