These are uric acid crystals in the microscopy of the urinary sediment. In physiological cases, uric acid crystals may appear after eating meals and strong sweat. In pathological cases, these crystals are observed when exposed to leukosis, pneumonia, and X-rays. At the same time the formation of ammonia which ensures the acid reaction of the urine is disrupted. And that's why we can see the uric crystals in the microscopy.