Pain in the small pelvis is one of the most frequent reasons for consulting a general practitioner. An estimated 12% of women worldwide suffer from chronic pain in the lower abdomen. In men, lower abdominal pain usually occurs as a consequence of pelvic surgery (such as total prostate resection).
Definition of pain
Pain is defined as an excitation of specific nerve fibres that is transmitted to the brain as an electrical signal. Among different causes, endometriosis, hardening of connective tissue (fibrosis) or the presence of scar tissue may all stimulate neighbouring nerves and cause pain. The pain signal is transmitted to the brain in the form of an electrical current. There is an infinite variety of pathways for the transmission of a pain signal and the actual site where the signal originates may not necessarily correspond to the site where it is felt by the patient. A good example can be found in phantom pains following amputation: a patient may complain of pain in a given limb even though this limb has been removed. At the same time, pain may also be caused by pathological damage or mechanical trauma inflicted directly to a nerve.
Selective nerve lesions may cause three types of pain:
The structure of a nerve fibre resembles that of an electrical cable. It contains a conducting inner part, the axon, which is the equivalent of a copper wire in a cable, and an isolating sheath, myelin. If a nerve is impaired or sectioned, the axon may continue to grow without its protective myelin sheath and be stimulated at the site of the lesion. As a rule, pain begins to be felt 6 weeks after the lesion occurred. Such pain, often described as «electric pain» by patients, may be triggered or amplified by different stimuli, such as mechanical pressure.
- Neuropathic pain
Neuropathic pain is not felt at the site of the lesion, but in the region that is innervated by the corresponding nerve. This type of pain is usually burning and dull, and may appear, for example, in cutaneous regions.
- Phantom pain
This type of pain may appear after a limb is amputated, after removal of an organ or following damage to nerves that are attached to an organ. An example is pelvic phantom pain that may be felt after the removal of the uterus following endometriosis. In such cases, patients who underwent surgery report lower abdominal pain which is identical to, or even stronger than, the pain felt before the intervention.