A cystic calculus from a wild western spiny softshell turtle (Apalone [Trionyx] spiniferus hartwegi).

During a postmortem examination of a western spiny softshell turtle (Apalone [Trionyx] spiniferus hartwegi), a calculus (24 x 21 x 12-mm) with a dry weight of approximately 5 g was discovered in the urinary bladder. Chemically, the calculus was a mixture of apatite (basic calcium phosphate), struvite (magnesium ammonium phosphate hexahydrate), and unidentifiable crystals. This is the first report of a cystic calculus in a wild chelonian.