Human urine is often saturated to the limit with uric acid, phosphates, and calcium oxalate. These substances may crystallize and the crystals may begin to clump together, eventually forming stones large enough to restrict urinary flow. Symptoms of kidney stones include pain radiating from upper back to the lower abdomen and groin, fre quent urination, pus and blood in the urine, absence of urine formation, and sometimes chills and fever.
Stones can range in size from microscopic specks to the size of a fingertip.
About 80 percent of all stones are calcium stones. High blood calcium levels causes extra calcium to be excreted in the urine. This concentrates the urine, increasing the likelihood of stone formation. There are infections on the urinary tract. The stone shifts may cause injury, thus sometimes the urine mix with blood.