Voluntary emptying of the bladder follows a command transmitted to the bladder by the splanchnic nerves. Although the splanchnic nerves are bilateral, their participation (dominance) may be unbalanced. They can be affected both by the endometriosis nodule (infiltration, compression, irritation- in this case the symptoms precede surgery) and by the surgical procedure. During surgery, these very fragile splanchnic nerves, may be removed en bloc with the nodule or cut.
Splanchnic nerves even if not removed, may be affected by the diffusion of heat used to coagulate the vessels or stretched during dissection, which may lead to neuropraxia. This term is used to describe moderate nerve damage resulting in temporary impairment of nerve function. It involves temporary loss of the nerve’s myelin sheath without any associated axonal damage, resulting in a slower speed of conduction of the electrical impulse within the nerve and therefore impaired transmission of information.
The prognosis of these impairments is favourable with complete recovery usually requiring a few weeks or months, the time required for the reformation of the myelin sheath. After surgery patients experience difficulty in emptying the bladder which retains a variable amount of urine at all times. If the volume of urine remaining in the bladder after urination (post-void residue or PVR) exceeds 100ml, patients require small catheters to empty the bladder several times a day (usually 5 or 6 times), at fixed times, and after attempting to urinate. Bladder function improves gradually, over 4-6 weeks after surgery, and self-catheterisation can be stopped when the PVR consistently falls below 100 ml.
Self-catheterisation, if required, is taught prior to discharge from the clinic. Patients are encouraged to regularly record urine volumes (voiding calendar) and to report them to the surgeon.
The frequency of bladder weakness requiring systematic self-catheterisation is approximately 25% at the time of discharge from the clinic and decreases to approximately 5% one year after surgery. Recovery of bladder function occurs with reduction in neuropraxia, water retention and localised inflammation due to surgery.