Radiographic aspects of nutritional hyperparathyroidism in a cougar (Puma concolor).

Background: Secondary nutritional hyperparathyroidism (SNH) is a metabolic disease related to calcium and phosphorus homeostasis and causes generalized bone dystrophy. It occurs especially when animals are fed diets which contain proportionally high levels of phosphorus. SNH has been diagnosed in various large feline species such as jaguars, tigers, lions and leopards by means of biochemical and radiographic exams. Even though the feeding habits of these animals are well known, mistakes regarding administration of diets to animals in captivity are common, the most frequent being feeding them exclusively meat. The aim of this study was to describe the clinical and radiographic fi ndings of SNH in a cougar kept in captivity. Case: An approximately 9-month-old cougar (Puma concolor) which had been fed an exclusive meat diet was referred to the UFMT Veterinary Hospital after a period of diet correction and oral supplementation with calcium. The animal exhibited hind limb ambulation problems, poor nutritional condition and constipation. Radiographic examination revealed a slight skeletal density reduction, severe angular deformities of the hind limb bones, thickening of the femoral diaphysis, abnormal curvatures of the tibiae and calcanei, lateral displacement of the patellae and narrowing of the pelvic canal. Additionally to the skeletal alterations, there was intense colonic impaction caused by exacerbated accumulation of segmented, highly radiopaque feces. Discussion: In their natural habitat, wild carnivores eat not only meat but also organs like liver, intestines and bones, which suffi ce the body’s needs for essential minerals and vitamins. A meat exclusive diet with no calcium and vitamin D supplementation results in imbalance of calcium and phosphorus levels as well as an increase in the parathyroid hormone levels in the serum. Increased levels of this hormone cause bone resorption and generalized decrease in skeletal density and resistance which can be identifi ed by means of radiographic exams. In this report, the animal exhibited history, clinical signs and radiographic fi ndings similar to cases of SNH in other large felines. Prolonged meat exclusive diet administration caused marked deformities of the pelvis and hind limb bones which were refl ected by severe problems in locomotion and defecation. Radiographs showed the existence of angular deformities in several long bones, alterations in shape and of the cortical and medullary portions of the bones, and also the presence of numerous radiopaque lines indicative of fracture consolidation. However, contrary to fi ndings described in other reports, there was only a focal reduction in bone density, probably owing to the balanced diet and treatment employed before the radiographs were taken. Furthermore, in this case constipation occurred simultaneously to the skeletal problems. As reported for domestic animals, the most plausible explanation for the fecal retention observed is mechanical compression of the rectum by the deformed pelvic bones. The present report demonstrates that nutritional hyperparathyroidism can occur in cougars, with characteristics similar to those observed in domestic cats and other large felines. Additionally, it can be diagnosed based on epidemiological data, clinical fi ndings and radiographic imaging.