Early‐stage crystalluria‐associated cystitis in a horse: Diagnostic value of serial urine sediment examination

Summary Calcium carbonate crystals are commonly observed in equine urine; however, crystalluria without urolith formation rarely results in clinically significant disease. A 4‐year‐old Japanese Sport Horse developed recurrent haematuria accompanied by the presence of numerous angular calcium carbonate crystals. Discontinuing the calcium supplementation and increasing dietary salt to promote water intake resulted in a reduction in crystal size and a change to a more rounded morphology after 3 months, although haematuria recurred. Ultrasonography revealed accumulation of sand‐like material within the bladder and subjective thickening of the bladder and urethra walls. Urine culture yielded Gram‐negative coccobacilli and 16S rRNA gene sequencing identified the organism as Acinetobacter pseudolwoffi . Further dietary management resulted in further reduction of crystal size and morphology comparable to those of a healthy control horse, with complete resolution of haematuria. No recurrence has been observed over 3 years. This case highlights the value of serial urine sediment examination for detecting changes in crystalluria and guiding noninvasive management of equine lower urinary tract disease.