Evaluation of Pulsed Radiofrequency Ablation of the Superior Hypogastric Plexus for Treatment of Bladder Pain Syndrome: A Randomized, Placebo-Controlled Pilot Study

Interstitial cystitis / bladder pain syndrome (IC/BPS) is a complex chronic pain syndrome characterized by bladder pain, pressure, and discomfort with urinary urgency and frequency, without signs of infectious or alternative cause. It disproportionately affects women, with an estimated 3-7% prevalence among women in the United States, and with a prevalence of 61% among women with chronic pelvic pain. Pathophysiology is currently poorly understood and the cause is unknown. It is widely accepted that IC/BPS may be broken into Hunner-type and non-Hunner type variants; however, beyond this histopathologic distinction, there remains a wide variety of proposed inflammatory, structural, autoimmune, infectious, functional, and neurogenic contributors to the overall picture of disease.

Current treatment of IC/BPS in the United States is guided by recommendations from the American Urological Association (AUA) and the American Urogynecologic Society (AUGS). In 2022, the AUA released updated guidance for treatment of IC/BPS. They outline a graded approach to uncomplicated IC/BPS, including non-pharmacologic and behavioral treatments (diet, education, stress management, physical therapy), oral medications, intravesical instillations, or procedures such as cystoscopy with hydrodistension, onabotulinumtoxinA injections, or neuromodulation. Rather than presenting these therapies in a "step-up" fashion, the AUA notes that initial treatment type should depend on symptom severity and patient preference, and multiple simultaneous therapies may be considered. Surgery with cystectomy or bladder augmentation are considered last-resort therapies. Of note, many of these established treatment options may come with undesirable side effects, intolerable complications, risks associated with general anesthesia, or shorter-than-optimal duration of action.

Some authors note that there is no one consistently effective treatment for IC/BPS, and one estimate states that 10% of patients with IC/BPS are refractory to conservative, non-surgical treatments. There is also a substantial psychosocial burden of IC/BPS; most patients with the disease have seen numerous providers before being appropriately diagnosed, and have tried multiple therapies unsuccessfully. These patients frequently experience concomitant voiding and bowel dysfunction, sexual dysfunction, mood disorders, social isolation, and greater unemployment.

One important contributor to the constellation of findings in IC/BPS is a shift towards sympathetically-mediated pain sensation in the setting of chronic pain. Central sensitization is hypothesized to occur in IC/BPS as well as other chronic pelvic pain syndromes. Williams et al found that subjects with IC/BPS had diminished vagal activity and a shift towards sympathetic nervous system dominance as reflected by decreased high-frequency heart rate variability on tilt table testing. Charrua et al had similar findings, showing significantly lower mean variation of the standard deviation of the P wave interval (a marker of sympathetic overactivity) on tilt table testing as well as significantly higher twenty-four hour urinary noradrenaline in patients with IC/BPS. These studies implicate autonomic nervous system aberrancy as a key factor in IC/BPS. Neuromodulation is the intervention of choice for managing hyperalgesic autonomic nervous system dysfunction. While neuromodulation using implantable stimulators has been extensively studied in IC/BPS, little research has been done on chemical neurolysis, radiofrequency ablation, or other nerve interruption strategies for pain management in IC/BPS.

Superior hypogastric plexus block (SHPB) is an interventional strategy used in chronic pain management initially investigated for the management of chronic cancer-related pelvic pain. The procedure targets the superior hypogastric nerve plexus, which is a bilateral retroperitoneal structure at the approximate level of L5/S1. The structure provides innervation to pelvic viscera including the bladder, urethra, vagina, vulva, ovaries, uterus, and pelvic floor. A study conducted by Plancarte et al investigated the first use of SHPB for chronic pelvic pain related to cancer in 28 patients. By injecting aqueous phenol in the retroperitoneal space overlying the superior hypogastric plexus, their team demonstrated a mean pain reduction of 70% in those treated with the block, with 3 patients experiencing durable pain relief for over two years.