Deep endometriosis can affect the sacral plexus, particularly when it spreads to the space to the side of the vagina and rectum, also known as the parametrium. The sacral plexus is located in the lateral, external and deep part of the parametrium, in contact with the pelvic wall. Endometriosis of the parametrium often infiltrates not only the sacral plexus, but also the vagina, rectum, ureters or even the bladder.
Deep endometriosis nodules of the parametrium may compress, envelop or infiltrate large diameter nerve structures such as the sacral roots, the sciatic nerve, the obturator nerve or the pudendal nerve, as well as smaller nerve structures such as the splanchnic nerves, the hypogastric nerves, the inferior and superior hypogastric plexus.
There are 2 types of parametrial nodules:
Deep endometriosis nodules of the sacral plexus can cause several specific symptoms, particularly during a woman’s periods.
This type of clinical presentation of endometriosis is rare and GP’s are often unaware of it. Consequently, in general symptoms are not initially considered to be due to endometriosis, but rather to rheumatological, osteoarticular or muscular causes.
The sacral plexus is composed of sensory and motor nerves. Some motor nerves are called “somatic” since they manage the voluntary motor response of the skeletal muscle fibres of the lower limbs, buttocks or pelvis. Others are called “vegetative” because they are involved in involuntary contraction of the organs of the pelvis and abdomen (rectum, colon, bladder), the erectile organs, the genital and skin glands or the blood vessels.
Somatic innervation (Fig 4) of the pelvis comes from nerves or roots originating from the spinal cord, either from the lumbar area (noted by L, from 1 to 5) or from the sacral area (S, from 1 to 4 or 5). The roots come out from the spine through the vertebral holes and interconnect in branchlike structures, also called the lumbar and sacral plexus.
The sacral plexus (Fig. 5) is formed by the root of the last lumbar (L5) and the roots S1, S2, S3 and S4 or S5. These nerve roots include afferent (information gathered in the periphery is directed to the spinal cord and to the brain) and efferent (information is sent to the muscles) fibres involved in sensory perception and voluntary movements of the lower limbs.
The sacral roots are located in the posterior part of the pelvis, between the sacrum and the lateral wall of the pelvis, in front of the piriformis muscle (fig 6). They converge and give rise to larger nerves (4 mm to 1 cm):
Finally, mainly small calibre (approx.1-2 mm) vegetative fibres, originating from S2, S3 and S4, interconnect to form a weblike network, located deep in the parametrium, to the side of the rectum and below the ureter: the inferior hypogastric plexus. Very fine nerves coming from the web reach the bladder, the bottom of the vagina and the rectum: the splanchnic nerves. The splanchnic nerves control voluntary emptying of the bladder, the working of the internal sphincter of the urethra and also influence rectal mobility and sexual functions.
The inferior hypogastric plexus also receives the hypogastric nerves, which are about 1-2 mm in diameter and are involved, among other things, in the sensation of bladder fullness.
Close to the sciatic nerve is the obturator nerve, which originates from the lumbar plexus (L2, L3 and L4), allows the movement of the thigh adductor muscles and the thigh to move towards the midline of the body (bringing the thighs together), and provides sensitivity to the middle of the thigh.
The anatomy of the pelvic nerves explains the location of pain and disorders concerning motility and pelvic organ function when there is damage to the sacral plexus or to the sciatic, obturator and pudendal nerves.
Surgery for endometriosis nodules of the sacral plexus can only be considered following detailed preoperative assessment.
MRI is a standard, essential and obligatory test, which provides the surgeon a 3D image of the location, dimensions, edges and volume of the endometriosis nodule. It provides details of involvement of neighbouring organs (rectum, ureter, bladder, vagina, piriformis muscle) and enables a surgical intervention to be planned with a multidisciplinary team.
A urodynamic test allows us to assess bladder function and to identify signs of nerve damage to the bladder. This examination is reserved for patients with clear symptoms of impaired bladder function, where suspected incomplete emptying of the bladder would justify use of a self-catheterisation programme before surgery.
Anorectal manometry investigates rectal function. In practice it is never performed before surgery and is reserved for patients with persistent defecatory problems after surgery.
You can find out more about the surgical techniques used in removing endometriosis nodules of the sacral plexus and sciatic nerves, in an article published in 2020 by our team and available at no cost.
The time taken for surgery depends on the complexity of the deep lesionsand particularly the time required for additional procedures involving the rectum, ureter, vagina or bladder. During one operation for endometriosis of the sacral plexuses, several procedures are performed, each one being highly complex.
The time taken for this type of surgery varies from 2 to 8 hours.
It is important to note that it is sometimes impossible to preserve certain nerves during the removal of large endometriosis nodules from the parametrium, this is particularly true for finer nerves. The sacrifice of these small nerves can lead to, albeit temporary, bladder and rectal function disturbances.
In some cases, where endometriosis concerns both parametria, we need to carry out complete resection on the side where the disease seems the most aggressive and a minimal procedure on the less affected side so as to avoid completely removing nerves from the bladder, rectum or vagina. While the sacrifice of small pelvic nerves can be considered on one side, surgery on large nerves such as the sciatic or obturator nerve should be as conservative as possible to avoid the occurence of major motor or sensory disorders.
Hospital stay varies from 3 to 7 days, depending on the type of surgery performed and post-operative effects. Recovery is faster if the surgery does not involve sutu the rectum or ureters.
After the operation patients can experience several immediate complications, which should be clearly presented before surgery:
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.
These kinds of pain are the result of irritation, nerve-related water retention or neuropraxia of the somatic nerves, and are characterised by electrical discharges, tingling, or painful sensations triggered by minimal stimulation (e.g. contact with clothing).
These symptoms require specific treatment with drugs that affect nerve transmission, such as pregabalin, amitriptyline and gabapentin, and which are administered over several weeks or months.
The symptoms are present in about 17% of cases at one year after surgery.
Long-term findings are encouraging, both in terms of clinical improvement and fertility. It is important to note that women with deep endometriosis involving the sacral plexus or sciatic nerve only rarely have associated ovarian or tubal involvement. This may explain the very high pregnancy (77%) and postoperative birth rates, with spontaneous conceptions in half of the cases.
This information should encourage patients to undergo surgery, even if they are trying to get pregnant. Scientific findings do not support the use of in vitro fertilisation in this situation, which can delay surgery and result in technically more complex surgery due to the continued growth of the lesions.
20-25
patients with sacral plexus involvement operated on every year
82,7%
of patients with sacral plexus involvement also have severe rectal injury
47%
of patients with sacral plexus involvement also have bladder injury
Bibliography
Roman, Merlot et al. JMIG 2020
IFEM Endo, a centre specialising in the management of endometriosis and complex forms of the disease, will accompany you on your care journey for endometriosis of the sacral plexuses.
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