Crystalluria in marathon runners. II. Ultra-marathon--males and females.

Particle-volume size distribution curves for the urines of a group of male ultra-marathon runners have been recorded and show the same features as those reported in an earlier study involving standard marathon runners. It is again suggested that these features indicate risk of urinary stone formation although this does not appear to be increased by the more stressful ultra-marathon. Distribution curves obtained for female runners closely resemble those recorded for controls, thus rendering it impossible to assess their risk profile. A commonly observed feature of both the male and female urines was the presence of various urinary salts. Profuse calcium oxalate dihydrate crystals were detected in some samples 11 days after the race. It is suggested that entrapment sites within the urinary tract have a selective specificity for these crystals while urinary salts pass through unhindered.