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Glenn A. Olah Smith Veterinary Hospital, 600 Alta Vista Ave, Santa Fe, NM 87505.

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 DVM, PhD

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History

A 12-year-old spayed female domestic shorthair cat was evaluated for dyspnea of approximately 12 hours' duration. Three years earlier, hyperthyroidism, hypertension, mild hypertrophic cardiomyopathy, and bilateral detached retinas had been diagnosed in the cat. At that time, the cat was treated with methimazole, atenolol, and amlodipine and it had gained and maintained weight. Ten months earlier, the hyperthyroidism was no longer adequately regulated with methimazole as evident by weight loss and increased serum total thyroxine concentration. The cat was then treated with sodium iodide I-131 at a referral clinic. Months after receiving 131I treatment, the cat developed stage IV renal failure and was being treated at home by the owner with fluids administered SC, benazapril, atenolol, famotidine, vitamin B complex, cobalamin, and supplemental potassium.

On physical examination, the cat had a body condition score of 3/9 (with a score of 1 being emaciated and a score of 9 being obese) and a heart rate of 156 beats/min (reference range, 130 to 180 beats/min) with occasional gallop rhythms detected during auscultation of the thorax. The cat was tachypneic (approx 60 breaths/min; reference range, 15 to 40 breaths/min) with inspiratory and expiratory dyspnea. Radiography of the thorax revealed a perihilar interstitial pattern and moderate pleural effusion. Increased radiopacity obscured the cardiac silhouette. Abnormalities detected on a CBC included nonregenerative anemia (Hct, 24% [reference range, 30% to 45%]; reticulocyte count, 42,000 cells/mL [reference range, < 60,000 mL]) and mild neutrophilia with a left shift. Abnormalities detected on serum biochemical analyses included high concentrations of phosphorus (8.1 mg/dL; reference range, 3.1 to 7.5 mg/dL), urea nitrogen (63 mg/dL; reference range, 16 to 36 mg/dL), and creatinine (3.9 mg/dL; reference range, 0.8 to 2.4 mg/dL). A fluid sample obtained via ultrasound-guided thoracocentesis was submitted for analysis; a modified transudate compatible with cardiomyopathy, a poorly exfoliating intrathoracic tumor, lung lobe torsion, or diaphragmatic hernia, was detected. Echocardiography revealed restrictive cardiomyopathy. After the cat's condition was stabilized, treatment for hypertension and renal failure was continued, except the volume of fluid administered SC was decreased from 100 to 50 mL/d. Treatment with spironolactone and aluminum hydroxide was initiated, and the owner was instructed to feed a diet formulated for the nutritional management of cats with heart and kidney disease.a Fourteen days after evaluation, radiographs of the thorax were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 12-year-old female cat obtained 2 weeks after being treated for dyspnea.

Citation: Journal of the American Veterinary Medical Association 229, 12; 10.2460/javma.229.12.1887

Radiographic Findings and Interpretation

Increased radiopacity of the aortic valve, ascending aorta, and descending aorta is evident (Figure 2). This increase was not apparent on the initial radiographs obtained 2 weeks earlier because of superimposition of the heart, perihilar pulmonary edema, and pleural effusion. The radiographic findings were compatible with aortic mineralization. Differential diagnoses for arterial mineralization include calcinogenic plant toxicosis, vitamin D toxicosis, primary or secondary hyper-parathyroidism, renal insufficiency, or paraneoplastic syndrome leading to metastatic mineralization.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. Notice increased radiopacity of the ascending and descending aorta (arrows) attributable to mineralization.

Citation: Journal of the American Veterinary Medical Association 229, 12; 10.2460/javma.229.12.1887

Comments

In the cat reported here, renal disease with secondary hyper-parathyroidism causing high phosphorous and calcium concentrations could have resulted in aortic metastatic mineralization. Aortic mineralization secondary to hypertension-induced arteriosclerosis could not be ruled out.1 Restrictive cardiomyopathy may lead to blood turbulence and aortic endothelial damage, resulting in arteriosclerotic plaque formation, or poor blood perfusion and oxygenation of the aortic tunica layers, contributing to dystrophic mineralization of the aorta.2

Metastatic mineralization can develop when the calcium-phosphorus product is greater than approximately 70.3 Calcium-salt depositions can occur throughout soft tissues, especially in the kidneys, gastrointestinal tract, cardiac and skeletal muscle, vasculature, tendons, and ligaments.3 Mineral depositions may lead to structural and functional abnormalities of affected tissue, including exacerbation of renal disease and decreased cardiac function. Schwarz et al4 reported no evidence of aortic mineralization in 786 thoracic radiographs, suggesting that aortic mineralization is rare in cats. Aortic mineralization has been reported in only a few cats with various diseases, including chronic renal failure, suspected hypertension, and heart disease.4 The cat of this report had severe chronic renal failure, a history of systemic hypertension and hyperthyroidism, and restrictive cardiomyopathy; all of these diseases may have contributed to aortic mineralization. Histologic examination of the aorta was not performed; therefore, arteriosclerosis or dystrophic mineralization could not be ruled out.

Options for treatment of hyperthyroidism include administration of methimazole, thyroidectomy, and 131I treatment.5 Evaluation of renal function is important before considering curative treatments such as surgery or administration of 131I. Evaluation involves administration of methimazole for a short period and assessment of renal function after determining that a cat is euthyroid. One month prior to treatment with 131I, renal function in the cat reported here was considered adequate. The cat was treated medically for severe chronic renal disease, hypertension, and heart disease for 7 months following evaluation for dyspnea, after which its condition deteriorated, and the owner chose to euthanize the cat; necropsy was not performed.

a.

Prescription diet g/d feline, Hill's Pet Nutrition Inc, Topeka, Kan.

  • 1.

    Lefbom BK, Adams WH, Weddle DL. Mineralized arteriosclerosis in a cat. Vet Radiol Ultrasound 1996;37:420423.

  • 2.

    Van Vleet JF, Ferrans VJ. Pathology of the cardiovascular system. In: Carlton WW, McGavin MD, eds. Thomson's special veterinary pathology. 2nd ed. St Louis: CV Mosby Co, 1995;199202.

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  • 3.

    Morrow CK, Volmer PA. Hypercalcemia, hyperphosphatemia, and soft-tissue mineralization. Compend Contin Educ Pract Vet 2002;24:380388.

  • 4.

    Schwarz T, Sullivan M, Stork CK, et al. Aortic and cardiac mineralization in the dog. Vet Radiol Ultrasound 2002;43:419427.

  • 5.

    Feldman EC, Nelson RW. Feline hyperthyroidism. In: Canine and feline endocrinology and reproduction. 3rd ed. St Louis: WB Saunders Co, 2004;152218.

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