Both acute injury or illness and chronic conditions (eg, chronic kidney disease, congestive heart failure, or cancer) are commonly associated with weight loss in dogs and cats.1 However, weight loss in these conditions is unlike weight loss in healthy animals. In healthy animals, weight loss is primarily attributable to loss of fat tissue, whereas lean body mass is the primary body compartment affected during weight loss associated with illness or injury. Muscle loss associated with disease is termed cachexia, whereas sarcopenia is a related condition involving muscle loss associated with aging in the absence of disease.1 Because muscle is functional tissue, cachexia and sarcopenia can adversely impact strength, immune function, wound healing, and mortality rates.1,2
One of the biggest challenges in addressing cachexia and sarcopenia is recognition and early diagnosis of the conditions. An MCS system has been validated for use in cats and dogs, and it is recommended by national and international organizations as a component of nutritional assessment for dogs and cats.3–5 Muscle condition scoring is ideal for clinical use in dogs and cats because it can be quickly and easily performed. However, it may not be precise enough as an outcome measure for research studies wherein quantification of muscle mass over time is needed, particularly when the changes in muscle mass are small.
Quantitative methods for assessment of lean body mass or muscle mass in humans include dual-energy x-ray absorptiometry and bioelectrical impedance,6 but inherent assumptions for each of these methods reduce their accuracy. Computed tomography is another method for measurement of muscle mass; however, companion animals must be sedated or anesthetized for both dual-energy x-ray absorptiometry and CT.7,8 Therefore, research on cachexia and sarcopenia in companion animals would benefit from more clinically relevant measures of muscle mass.
Ultrasonography is a method for quantification of muscle mass in dogs and cats that does not typically require that animals be sedated or anesthetized. Ultrasonographic measurement of muscle has been used to assess muscle loss in humans,9,10 healthy dogs,7,11 cats,12 and dogs with various degrees of cachexia and sarcopenia.13 However, ultrasonographic techniques have not been validated for assessment of muscle mass in cats with cachexia and sarcopenia. Therefore, the objectives of the study reported here were to assess the convergent validity between MCS and ultrasonographic measurements in cats with various degrees of muscle loss as well as to evaluate the repeatability and reproducibility of MCS assessment in this population of cats.
Supported by Nestlé Purina PetCare Co.
Drs. Freeman, Michel, and Fages received reimbursement of travel expenses associated with conducting this study. Dr. Freeman has received research funding from or provided sponsored lectures or consulting services for Royal Canin, Nestlé Purina PetCare, Aratana Therapeutics, and Hill's Pet Nutrition Inc. Dr. Michel has received research funding from Royal Canin and Nestlé Purina PetCare Co and serves on an Advisory Council for Nestlé Purina PetCare Co. Drs. Zanghi and Vester Boler are employees of Nestlé Purina Research.
Presented in part at the 2019 American College of Veterinary Internal Medicine Forum, Phoenix, June 2019.
The authors thank Jim Ambrose, Dr. Melanie Barnes, Hallie Barnett, Brandy Panning, and Sarah Dionne for technical assistance and Dr. James Sutherland-Smith for assistance with development of the ultrasonographic method for measuring muscle mass and for valuable input on its use in cats.
Body condition score
Epaxial muscle height
Forelimb epaxial muscle score
Muscle condition score
Vertebral epaxial muscle score
Sonoscape S8 Expert, National Ultrasound, Duluth, Ga.
L752 5–12 MHz linear probe, National Ultrasound, Duluth, Ga.
Systat, version 13.0, Systat Inc, San Jose, Calif.
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