Muscle loss is common in animals with chronic diseases (eg, chronic kidney disease, congestive heart failure, and cancer) or an acute injury or illness and during aging. Muscle loss associated with disease is called cachexia, whereas muscle loss associated with aging in the absence of disease is called sarcopenia.1 Because older animals are more likely to develop chronic diseases, sarcopenia and cachexia can occur concurrently. Given that there is a lack of reserve for endogenous protein, cachexia and sarcopenia result in loss of functional tissue, which impacts strength, immune function, wound healing, and mortality rates.1
Identifying cachexia and sarcopenia at their earliest stages is important to enable the most effective treatment. In humans, most definitions for cachexia rely on weight loss. However, weight loss occurs later than muscle loss, so identifying muscle loss is important. Muscle mass can be estimated in humans by measurements of lean body mass obtained with DEXA. This works well in healthy humans, although adjustments for age, sex, and race are important for accurate results.2 However, there are inherent assumptions with DEXA that negatively impact its accuracy for ill people and companion animals. An additional challenge is that DEXA requires that companion animals be anesthetized.3 Computed tomography has been used as a more direct method to measure muscle mass in humans and dogs, but CT still requires that companion animals be anesthetized or sedated and exposes subjects to some radiation. Therefore, more clinically relevant measures of muscle mass are desirable.
Accuracy of the MCS has been validated in cats,4 and MCS is recommended by the American Animal Hospital Association5 and World Small Animal Veterinary Association6 as part of a nutritional assessment that should be performed on all dogs and cats at every veterinary visit. An MCS system has been developed for cats and dogs,7 but it has not yet been validated for use in dogs.
Quantitative magnetic resonance is a technique that does not require that dogs and cats be anesthetized, and results of QMR are significantly correlated with DEXA results and total body water (determined by use of deuterium) in healthy Beagles.8 However, even in a healthy population of dogs, QMR and DEXA both underestimated lean body mass by 13.4% and 7.3%, respectively, compared with the value determined by use of total body water.8 Precision and accuracy of QMR and DEXA for ill animals have not been determined.
Recently, ultrasonography of muscle has been used to assess muscle loss in humans with cachexia and sarcopenia.9,10 An ultrasonographic method for assessment of epaxial muscles has been validated for use on healthy dogs11 and cats.12 However, to be of clinical use for dogs, this method must be evaluated in dogs with cachexia and sarcopenia.
Therefore, the objectives of the study reported here were to evaluate the repeatability and reproducibility of a 4-point MCS system for use in dogs; to assess the convergent validity between the MCS, ultrasonographic images, and QMR images in dogs; and to identify cutoff values for ultrasonographic measurements of muscle that could be used to identify dogs with cachexia and sarcopenia.
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 or provided sponsored lectures or consulting services for Royal Canin, Nestlé Purina PetCare, Aratana Therapeutics, and Hill's Pet Nutrition. Dr. Freeman also serves on an Advisory Council for Aratana Therapeutics. 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.
The authors thank Jim Ambrose, Dr. Melanie Barnes, Kacie Dahms, and Laura Hart for technical assistance.
Body condition score
Dual-energy x-ray absorptiometry
Forelimb epaxial muscle score
Muscle condition score
Receiver operator characteristic
Vertebral epaxial muscle score
Nestlé Purina PetCare Co, St Louis, Mo.
Random integer generator, Randomness Integrity Services Ltd. Dublin, Ireland.
Sonoscape S8 Expert, National Ultrasound, Duluth, Ga.
L752 5- to 12-MHz linear probe, National Ultrasound, Duluth, Ga.
Systat, version 13.0, Systat Inc, San Jose, Calif.
SPSS, version 24.0, IBM Corp, Armonk, NY.
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5. Baldwin K, Bartges J, Buffington T, et al. AAHA nutritional assessment guidelines for dogs and cats. J Am Anim Hosp Assoc 2010;46:285–296.
7. World Small Animal Veterinary Association Global Nutrition Committee. Muscle condition score charts for dogs and cats. Available at: www.wsava.org/Guidelines/Global-Nutrition-Guidelines. Accessed Nov 24, 2018.
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