A preliminary study of natural-fill radiotelemetered ovine fetal cystometry

To determine whether fetal cystometric studies by radiotelemetry are feasible in the fetal lamb, and potentially suitable for chronically monitoring fetal bladder pressures in an experimental fetal model of bladder outlet obstruction (BOO), as in utero BOO (e.g. caused by posterior urethral valves) results in significant postnatal bladder dysfunction but the pathophysiological progression of fetal bladder maldevelopment remains poorly understood.

The procedure required fetal sheep surgery and anaesthesia. Radiotelemetry implants comprised catheters that transmitted pressure fluctuations to an implant body; data were then transmitted using radio frequency to a receiver that passed this information to a computer. Four fetuses were used with different methods of catheter placement to optimize the technique.

Recordings were possible in three of the four sheep; during observation there were: (i) quiet periods with no abdominal or bladder pressure rises; (ii) synchronous activity in the bladder and abdomen; and (iii) discriminate activity, associated with intravesical activity only. Four patterns of discriminate bladder activity were observed, defined as void, immature void, staccato activity and 'unstable' type activity.

Radiotelemetry cystometry for long-term monitoring is feasible in the experimental fetus without causing death or morbidity, or inhibiting growth. The method can discriminate reproducible patterns of detrusor activity. Recorded 'voiding' types were consistent between experiments and as reported in other fetal animal studies.