Giant bladder stone in a natural mummy of the early 19th century.

We present a case of a giant bladder stone, 7.5 cm in diameter, found in the pelvis of a 19th-century natural mummy from Borgo Cerreto (central Italy). We used microchemical energy-dispersive x-ray spectroscopy analysis and x-ray diffraction to define the mineral composition of the stone and obtain information about its internal structure. Chemical analysis showed a mixed composition. The internal layers contained mostly ammonium acid urate, whereas the external layers were composed of magnesium ammonium phosphate (struvite). Our research suggests a metabolic origin for the calculosis, with superimposed infection.