A Chronic, Conscious Large Animal Platform to Quantify Therapeutic Effects of Sacral Neuromodulation on Bladder Function

Purpose: Sacral neuromodulation is a Food and Drug Administration approved therapy for urinary urge incontinence, urgency-frequency and fecal incontinence. Most preclinical studies have used anesthetized preparations in small animals. To expand the testing capabilities of sacral neuromodulation stimulation parameters and novel concepts we created a large animal model in fully conscious sheep. Materials and Methods: Six adult female sheep were tested weekly using 10 trials of single fill cystometry, similar to clinical urodynamics. Maximal bladder capacity was measured without (trials 1 to 5) and with (trials 6 to 10) sacral neuromodulation. A mixed effects regression model was used to analyze the effect of sacral neuromodulation on bladder capacity. Results: Acute sacral neuromodulation significantly increased bladder capacity in conscious female sheep from 75.2 to 118.7 ml, an almost 60% increase. This was not simply an effect of repeat cystometric trials since testing without sacral neuromodulation was not associated with an increase in bladder capacity. Conclusions: These data demonstrate the effects of acute sacral neuromodulation on bladder capacity in the conscious sheep. This model represents a useful testing platform for novel sacral neuromodulation concepts such as alternate methods and parameters of therapy delivery.