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 pulmonary mineralization using 99m Tc‐methylene diphosphonate ( 99m Tc‐MDP) in dogs with pituitary‐dependent hyperadrenocorticism (PDH). Twenty‐one dogs with PDH were pro‐spectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using 99m Tc‐macro‐aggregated albumin [ 99m Tc‐MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco‐lumbar vertebrae from lateral thoracic 99m Tc‐MDP images. Thoracic: vertebral ratios were calculated using 99m Tc‐MDP studies from 21 control dogs. The thoracic: vertebral ratios were compared between the 2 groups (PDH and control). The mean age (±SD) of the 21 PDH dogs was 10.2 (±3) years, whereas the mean age of the control group was 9.8 (±3) years. Seven of the 21 dogs with PDH were hypoxemic (denned as an arterial partial pressure of oxygen [PaO 2 ] <80 mm Hg) with an average PaO 2 (±SD) of 62 (±15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using 99m Tc‐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 different 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 hypoxemia in dogs with PDH.