Stone formation after augmentation cystoplasty: the role of intestinal mucus

We evaluated the role of mucus in urine after bladder augmentation and hypothesize that mucus acts as a possible etiological factor in stone formation.

Mucus was collected via centrifugation from the 24-hour urine specimens of 8 stone forming and 10 nonstone forming patients who were randomly selected from our augmentation population. The mucus and stones were lyophilized, and then analyzed via scanning electron microscopy and energy dispersive x-ray spectrometry for calcium, phosphate, magnesium and sodium. The 24-hour urine collections were also analyzed to determine any metabolic differences between the 2 groups.

Scanning electron microscopy and energy dispersive x-ray spectrometry spectra showed increased calcium, phosphate, and magnesium, and significantly higher (p < 0.05) calcium-to-phosphate ratios in the mucus of stone versus nonstone forming patients. Of the 8 stones examined all had viscous fluid (mucus) centers rich in calcium, phosphate and magnesium. Calcium-to-phosphate ratios in the corresponding mucus recovered from stone centers were similarly high. Urinary citrate levels were low in both groups, and calcium, phosphate and magnesium were within normal ranges.

Mucus appears to have an important role in the genesis of bladder stones after augmentation, possibly acting as a nidus. Metabolic changes following augmentation were similar in stone and nonstone forming populations. Our data suggest that mucous calcium-to-phosphate ratios may be predictive of future stone formation. Furthermore, there may be a benefit in instituting more aggressive measures aimed at clearing mucus from the bladder.