**8. Nocturia**

Many patients with vaginal vault or uterine prolapse – even if of a minor degree – complain about nocturia. Figure 6 explains the mechanism that leads to nocturia.. When the patient is asleep, the force of gravity pulls down the bladder base. Normally, with firm uterosacral ligaments, the bladder is held high (dotted line in Figure 6). When the patient is asleep and the uterosacral ligaments are loose, the pelvic floor muscles are relaxed, the bladder descends posteriorly, the bladder base is stretched and the stretch receptors "N" are stimulated.

Fig. 6. Mechanism of nocturia- schematic view- patient asleep. The pelvic muscles (arrows) are relaxed. As the bladder fills, it is pulled downwards by the force of gravity 'G'. In the normal patient, bladder descent is limited by the uterosacral ligaments "USL". If "USLs" are loose, the bladder descends more, the stretch receptors "N" are stimulated, the micturition reflex is activated at a low bladder volume, "nocturia". (from P Petros 2010, by permission)
