Urine sediment, 400x

 Ammonium biurate crystals are large, amber, rounded crystals with pointed protuberances along their surface. They are typically seen in cases of portal-systemic shunts, but may be seen with urate uroliths, or normally in Dalmatians or English Bulldogs. With urate uroliths, or physiological crystalluria in Dalmatians or English Bulldogs, the crystals tend to be of the ammonium urate type which have a smooth surface.