Increased radiopharmaceutical uptake in skeletal muscle in 26 flat racing and endurance horses (2017–2021)

Abstract

SummaryBackgroundIncreased radiopharmaceutical uptake (IRU) in skeletal muscle in horses has been previously reported but only a few authors describe its location in detail.ObjectivesTo describe and document the distribution of IRU in skeletal muscle in a population of flat racing and endurance horses.Study designRetrospective descriptive study.MethodsBone phase nuclear skeletal scintigraphy studies of 17 endurance and 9 racehorses with IRU in skeletal muscle were reviewed. The affected muscles were described and differences between endurance and flat racing horses were analysed. Ultrasonographic appearance of the muscles with IRU was also described when available.ResultsA total of 22 hindlimb scans (14 endurance horses, 8 racehorses) and 7 forelimbs scans (5 endurance horses, 2 racehorses) were analysed. In the hindlimbs, IRU was most frequently observed in the semitendinosus muscle in endurance horses (7/14, 50%) and in the gluteus medius muscle in racehorses (4/8, 50%). Bilateral IRU in the same muscle was often observed (11/22, 50%) in the hindlimbs. In 87.5% of the studies with IRU in the biceps femoris (7/8) or the semitendinosus muscles (7/8), the IRU was bilateral. In the forelimbs, IRU was most frequently observed in the triceps brachii (2/5, 40%) and latissimus dorsi (2/5, 40%) muscles in endurance horses and in the brachiocephalicus muscle in racehorses (2/2, 100%). The distribution of the skeletal muscles with IRU was more varied in endurance than in flat racehorses. No statistically significant difference was found in the distribution of the skeletal muscles with IRU between endurance and racehorses.ConclusionsEven though no statistical differences between groups could be demonstrated, this study describes the frequent location of IRU in muscle in the semitendinosus of endurance horses and in the gluteus medius of flat racehorses included in this study. The distribution of muscles with IRU was more variable in endurance horses.