Ultrasound-guided interventional procedures for patients with chronic pelvic pain - a description of techniques and review of literature.

Chronic pelvic pain can present in various pain syndromes. In particular, interventional procedure plays an important diagnostic and therapeutic role in 3 types of pelvic pain syndromes: pudendal neuralgia, piriformis syndrome, and "border nerve" syndrome (ilioinguinal, iliohypogastric, and genitofemoral nerve neuropathy). The objective of this review is to discuss the ultrasound-guided approach of the interventional procedures commonly used for these 3 specific chronic pelvic pain syndromes. Piriformis syndrome is an uncommon cause of buttock and leg pain. Some treatment options include the injection of the piriformis muscle with local anesthetic and steroids or the injection of botulinum toxin. Various techniques for piriformis muscle injection have been described. CT scan and EMG-guidance are not widely available to interventional physicians, while fluoroscopy exposes the performers to radiation risk. Ultrasound allows direct visualization and real-time injection of the piriformis muscle. Chronic neuropathic pain arising from the lesion or dysfunction of the ilioinguinal nerve, iliohypograstric nerve, and genitofemoral nerve can be diagnosed and treated by injection to the invloved nerves. However, the existing techniques are confusing and contradictory. Ultrasonography allows visualization of the nerves or the structures important in the identification of the nerves and provides the opportunities for real-time injections. Pudendal neuralgia commonly presents as chronic debilitating pain in the penis, scrotum, labia, perineum, or anorectal region. A pudendal nerve block is crucial for the diagnosis and treatment of pudendal neuralgia. The pudendal nerve is located between the sacrospinous and sacrotuberous ligaments at the level of ischial spine. Ultrasonography, but not the conventional fluoroscopy, allows visualization of the nerve and the surrounding landmark structures. Ultrasound-guided techniques offer many advantages over the conventional techniques. The ultrasound machine is portable and is more readily available to the pain specialist. It prevents patients and healthcare professionals from the exposure to radiation during the procedure. Because it allows the visualization of a wide variety of tissues, it potentially improves the accuracy of the needle placement, as exemplified by various interventional procedures in the pelvic regions aforementioned.