Diagnostic Imaging and Cytological Analysis Aid the Clinical Investigation of Long Digital Extensor Tendon Subtendinous Bursitis in a Horse.
Authors: Lapjit Chayapol, Charoenchanikran Ponlakrit, Petchkaew Pongsakorn, Sukpipattanamongkol Siriporn, Yodsheewan Rungrueang, Theerapan Wutthiwong, Chanda Metha
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Long Digital Extensor Subtendinous Bursitis in an Adult Horse Subtendinous bursitis affecting the long digital extensor tendon at the fetlock is an uncommon condition that can develop insidiously following routine exercise, yet may present with only localised swelling and no associated lameness—making early diagnosis challenging without appropriate imaging. This case report documents an 8-year-old riding horse with dorsomedial fetlock distension in which radiography revealed cortical thickening on the distal metacarpal bone, whilst ultrasonography demonstrated synovial proliferation, irregular fibrous thickening of the inner bursal lining, and local protuberance within the bursa itself. Cytological analysis of aspirated bursal fluid proved diagnostically valuable, identifying multiple nucleated cell populations (synoviocytes, nondegenerate neutrophils, lymphocytes, and macrophages) consistent with inflammatory bursitis rather than infectious disease. Intrabursal injection of 10 mg triamcinolone acetate with 25 mg hyaluronan, combined with pressure bandaging, resulted in substantial resolution of distension within four weeks, highlighting the effectiveness of anti-inflammatory therapy when correctly targeted. For equine practitioners, this case underscores the importance of multimodal diagnostic investigation—combining imaging with cytological examination—to confirm bursal pathology and guide therapeutic decisions, particularly when clinical lameness is absent and traditional flexion tests prove negative.
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Practical Takeaways
- •Dorsomedial fetlock distension without lameness warrants diagnostic imaging and cytological analysis to rule out subtendinous bursitis, as clinical signs may be subtle.
- •Ultrasonography combined with synovial fluid analysis provides superior diagnostic accuracy for characterizing bursal lesions compared to radiography alone.
- •Intrabursal corticosteroid and hyaluronan therapy with conservative management can effectively resolve subtendinous bursitis; monitor response at 4 weeks post-treatment.
Key Findings
- •An 8-year-old riding horse presented with dorsomedial distension of the left hindlimb fetlock following routine exercise without associated lameness.
- •Ultrasonography revealed synovial thickening, fibrous proliferation with irregular borders, and local protuberance within the bursa beneath the long digital extensor tendon.
- •Cytological analysis identified multiple nucleated cells including synoviocytes, nondegenerate neutrophils, lymphocytes, and macrophages confirming inflammatory response.
- •Intrabursal injection of 10 mg triamcinolone acetate with 25 mg hyaluronan and pressure bandaging resulted in substantial distension reduction within 4 weeks.