The female pelvis contains diverse, multiple, and intricately innervated structures that are potential sources of pain. As an example, when the etiologic process is gynecologic cancer, which tends to spread locally either by direct invasion or by spread of metastases to regional lymph notes, pain can be present at multiple sites simultaneously.
Pelvic pain is particularly difficult to manage because it is often vague, poorly localized, and tends to be bilateral or to cross the midline. Thus, a systematic approach to pelvic pain is the best approach. A careful review of history and physical examination may give a clue about the source and type of pain. Cooperation with a specialist in gynecology, urology, or colorectal surgery is helpful in identifying the most likely location of the painful stimulus during a directed pelvic examination.
Two types of diagnostic blocks are typically performed to try to ascertain the source of the pain and hence devise a treatment plan:
1. Differential spinal block - to differentiate between psychological, central, sympathetically medicated, or somatic pain
2. Sympathetic block - to impact nerves directly supplying the pelvic structures
A. Superior hypogastric plexus block: Specifically useful for pelvic pain arising from the uterus and upper vagina, bladder, prostate, urethra, seminal vesicles, testes, and ovaries; pelvic pain secondary to radiation; sympathetically maintained pain (e.g., after rectal anastomosis, abdominoperineal resection, etc.); and chronic pelvic inflammatory processes.1
B. Inferior hypogastric block: Primarily useful for perineal pain either malignant or sympathetically mediated, and superficial hyperesthesia including sensation of severe burning and urgency.
Both blocks are done initially with a local anesthetic, as diagnostic/therapeutic blocks. Local anesthetic blocks are therapeutic if done multiple times in patients with sympa thetically mediated pain. Patients with malignancy, who get good relief although short-lived, might benefit from neu-rolytic blocks.
Neurolytic blocks are done using the same technique. However, instead of using a local anesthetic, a neurolytic agent is used, such as alcohol (because it is hypobaric and the patient is in a prone position) or 6% phenol (occasionally used, if a hyperbaric solution is needed). The patient must be made aware of the risks and side effects of the neurolytic block before proceeding.
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