Frequency of pulmonary mineralization and hypoxemia in 21 dogs with pituitary-dependent hyperadrenocorticism

The purpose of this study was to determine the frequency of hypoxemia and p ulmonary mineralization using Tc-99m-methylene diphosphonate (Tc-99m-MDP) i n dogs with pituitary-dependent hyperadrenocorticism (PDH). Twenty-one dogs with PDH were prospectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (u sing Tc-99m-macro-aggregated albumin [Tc-99m-MAA]). The radiographs and bon e and perfusion studies were evaluated subjectively. An averaged quantitati ve count density ratio was calculated between the thorax and cranial thorac o-lumbar vertebrae from lateral thoracic Tc-99m-MDP images. Thoracic:verteb ral ratios were calculated using Tc-99m-MDP studies from 21 control dogs. T he thoracic: vertebral ratios were compared between the 2 groups (PDH and c ontrol). The mean age (+/-SD) of the 21 PDH dogs was 10.2 (+/-3) years, whe reas the mean age of the control group was 9.8 (+/-3) years. Seven of the 2 1 dogs with PDH were hypoxemic (defined as an arterial partial pressure of oxygen [PaO2] < 80 mm Hg) with an average PaO2 (+/-SD) of 62 (+/-15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization bas ed on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using Tc-99m-MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic . The average quantitative thoracic:vertebral ratio was not significantly d ifferent between the PDH and control dogs (0.5 +/- 0.4 versus 0.4 +/- 0.1, P =.16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hy poxemia in dogs with PDH.