Aortic mineralization in a dog
History: A 19.09kg, 10 year old canine, male Aussie was euthanized due to chronic kidney disease with azotemia and hyperphosphatemia with anemia (PCV 15-18 %). The owner is concerned about 2,4 D Herbicide toxicity.
Gross Lesions: (sorry no gross pictures; see below for histo)
The conus of the aorta had multifocal 1mm white mineralized nodules protruding into the aortic lumen distal to the aortic sinuses. The left coronary artery was dilated to about 2-3 times its normal size.
The liver had multifocal well circumscribed white nodules measuring up to 4 cm in diameter and protruding from the capsular surface. The liver had rounded margins diffusely.
The kidneys were small with irregular surfaces and mottled brown, red and grey. The cortex was pale and thin and had multifocal white streaks. The cortex of the adrenal glands was tan and soft with irregular borders. The serosal surface of the descending duodenum had a 1.5 mm white hard nodules.
Kidney: There are multifocal to coalescing areas of interstitial fibrosis and loss of cortical tubules with scattered foci of lymphocytes in the interstitium. Most of the glomeruli have thickened Bowman’s capsules and are surrounded by multiple layers of collagen and large numbers of glomeruli are replaced by eosinophilic material. Multifocal tubules are filled with homogenous eosinophilic material and multifocal tubules are lined by attenuated epithelium. There is multifocal mineralization of tubular and glomerular epithelium.
Liver: The liver contains an unencapsulated, well demarcated, invasive neoplasm composed of sheets of pleomorphic round cells with scant eosinophilic cytoplasm, round to pleomorphic eccentrically located nuclei with coarse chromatin and single nucleoli. There is severe anisocytosis and anisokaryosis. There are large numbers of binucleate and some multinucleated cells with 3-5 nuclei. Similar cells are present in the lymph node examined and replace much of the normal architecture. One central vein is filled with neoplastic cells. There are no mitotic figures seen.
Aorta: Within the tunica media of the aorta are multifocal areas of mineralization bordered by cartilaginous and osteoid matrix with cells located in discrete lacunae. There is multifocal disruption of the tunica intima.
Bone marrow: The bone marrow is hypocellular consisting of mostly adipocytes with low numbers of mature erythroid and myeloid cells and low numbers of immature hematopoietic cells. There are no significant microscopic lesions in the spleen, lung, adrenal glands, skeletal muscle, pancreas, small intestine, stomach, thyroid gland, urinary bladder.
1. Kidney: Glomerulonephritis and interstitial nephritis, chronic, lymphoplasmacytic with interstitial fibrosis, loss of tubules, tubular necrosis, and glomerular sclerosis.
2. Aorta: Multifocal mineralization of the tunica media with chondroid and osteoid material
3. Liver: Multifocal well differentiated B cell lymphoma, metastatic
4. Bone marrow: Bone marrow hypoplasia
The primary problem in this dog was chronic renal disease. This will lead to hyperphosphatemia and cause metastatic mineralization in soft tissues. The underlying cause of the renal disease could not be determined, however it is not likely due to 2,4 D herbicide exposure. The cellular features of the liver neoplasm look similar to plasma cells however immunohistochemistry would be needed to further characterize the tumor.
Mineralization of the aorta has been reported in many species but generally has little significance of its own. It can be seen in cases of hypercalcemia, hyperphosphatemia, Vitamin D toxicity, or renal failure. In this case it is likely secondary to chronic renal failure. A recent study of arterial calcification in horses described similar chondroid changes as those found in this dog. The pathogenesis is still unknown, but it was speculated to be an active process rather than a degenerative change as it is in humans.
The presence of lymphoma in this dog was incidental since we did not find it in any other tissues besides the liver. The lymphocytes in the neoplasm were morphologically distinct from the lymphoplasmacytic inflammation in the kidneys.
Causes of chronic glomerulonephritis and interstitial nephritis in adult dogs include:
Leptospirosis, Lyme disease, Ehrlichiosis, Chronic pyelonephritis, protothecosis, immune mediated glomerulonephritis and amyloidosis
Vet Pathol 45:617–625 (2008). Arterial Calcification in Race Horses L. G. ARROYO, M. A. HAYES, J. DELAY, C. RAO, B. DUNCAN, AND L. VIEL
J Vet Diagn Invest 19:518–524 (2007). Osteocartilaginous metaplasia in the right atrial myocardium of healthy adult sheep. Gopakumar Gopalakrishnan, William E. Blevins, William G. Van Alstine