The inside of the bladder has been exposed by removal of the dome. Note that there are many small pebbles and much gravel in it. Stones, pebbles and gravel originate in the kidney and travel to the bladder. Renal stones, urolithiasis, are of four distinct chemical types:
1) 77% are contain calcium, either as calcium phosphate or calcium oxalate. 2) 15% are struvite stones composed of magnesium ammonium phosphate. 3) 6% are uric acid stones. 4) 2% are composed of cystine.