A study on onabotulinumtoxinA (Botox) injection into the trigone in Interstitial cystitis/bladder pain syndrome patients threw some doubt on whether Hunner's lesions themselves are the major pain generators, even though the study was not designed for that purpose.
Atlanta-Interstitial cystitis/bladder pain syndrome (IC/BPS) patients with Hunner's lesions often have the worst symptoms, and treating the lesions themselves with cauterization or steroid injection often offers great relief. But a study presented at the AUA annual meeting in Atlanta on onabotulinumtoxinA (Botox) injection into the trigone in these patients threw some doubt on whether the lesions themselves are the major pain generators, even though the study was not designed for that purpose.
It was designed to compare the results of hydrodistention and trigonal onabotulinumtoxinA injection in these patients. The controlled, randomized trial of 32 patients was conducted by urologists at Moscow State Medical Stomatological University and presented by co-author Dmitry Pushkar, MD, professor and chair of urology at the university. The authors used 10 injections of 10 U of onabotulinumtoxinA in 10 mL of normal saline into the trigone only, based on studies by Rui Pinto, MD, and colleagues at the Hospital de São João in Porto, Portugal, who pioneered the technique in IC/BPS patients.
What the Russian researchers found was that O'Leary-Sant Symptom and Problem Index scores, pain scores on a 10-point visual analog scale, and quality of life scores all improved significantly from baseline in both groups and that the improvement was about the same at 3 months.
Botulinum patients fare better at 1 month
The patients who received the onabotulinumtoxinA trigonal injections fared much better than the hydrodistention patients at this earlier date. For example, in answer to the question on the O'Leary-Sant Symptom Index regarding pain or burning in the bladder during the past month, the hydrodistention patients had their scores drop from a mean of about 3.5 to about 2.5 at that time, whereas the onabotulinumtoxinA patients' scores dropped to almost 0.5. On the Problem Index question on whether burning, pain, discomfort, or pressure in the bladder had been a problem in the last month, the hydrodistention patients' scores dropped modestly from about 3.5 to 2.5, whereas the onabotulinumtoxinA patients' scores dropped to an average of about 1.5 after 1 month.
Urinary retention has been a concern with onabotulinumtoxinA injection, but in the patients who were treated by the intratrigonal technique in this study, there were no increases in the amount of residual urine, no decrease in uroflow rates, and no significant upper urinary tract retention evidenced by renal ultrasound.
The technique provoked some reaction from a Danish urologist who wondered why the Russian team chose the trigone while the pain generator was in the bladder. But Francisco Cruz, MD, a member of the Portuguese team that did the first study of intratrigonal injection in IC patients, rose to the microphone to say that the answer was simple.
"The majority of nociceptive fibers in the bladder are located in the trigone, so, from a logical point of view, there is no good reason to spread botulinum toxin throughout the entire bladder if most of the nociceptive fibers are located in the trigone. Doing that, we can also decrease the risk of urinary retention, which is a problem," Dr. Cruz said.
Dr. Cruz, as a Taiwanese urologist pointed out, did have a study published on intratrigonal onabotulinumtoxinA injection in more typical IC patients and wondered why the Russian team selected Hunner's lesion patients, but Dr. Pushkar pointed out that one of their study aims was to test the idea that the trigone was the major nociceptive area in IC patients.
For urologists who might try this technique, Dr. Pushkar pointed out that both techniques must be performed under general anesthesia and further explained that the team tried to avoid any kind of distention in the injection group because it prompts bleeding, making injection difficult.
"Anything we can do to keep these therapies as noninvasive as possible will probably benefit the patient," pointed out session co-chair Robert Moldwin, MD, associate professor of urology at the Hofstra North Shore Long Island Jewish School of Medicine, New Hyde Park, NY.