**3.4 Which endoscopic treatment, transurethral resection or coagulation, can further reduce recurrence?**

Prominent ulcerations are observed in the histology of Hunner lesion, which may be covered by fibrin mixed with inflammatory cells, in particular neutrophils. The lesions are often wedge-shaped and involve the superficial part of the lamina propria, often extending into the muscularis mucosae. Thus, deep biopsies including bladder muscle are required, since the disease process involves superficial as well as deeper layers of the bladder wall [4]. Many symptoms and findings in IC/BPS with Hunner lesion may be ascribed to the release of mast cell–derived factors. Mast cells are often observed near nerves, and functional evidence suggests innervation of these cells. As a hypothesis that has been accepted so far, transurethral ablation might be the removal of intramural nerve endings engaged in the inflammatory process [21–23].

Whether transurethral resection of Hunner lesion is capable of disease control compared with coagulation/fulguration and prevents recurrence of Hunner lesion is an important question. A randomized controlled study was conducted to compare the therapeutic effect between transurethral resection and coagulation of Hunner lesion in 126 patients with IC/BPS [24]. The primary endpoint was the difference in recurrence-free time between the two surgical methods, and the secondary outcomes were voiding symptoms, pain level, and risk factors for recurrence. The median duration of follow-up was 11.0 months. There were no differences in the recurrence-free time between the treatment groups: 12.2 months (95% confidence interval [CI], 11.1–17.6) for the transurethral resection group and 11.5 months (95% CI, 9.03–16.1; p = 0.735) for the transurethral coagulation group. In addition, after both procedures, the mean daytime frequency, nocturia, urgency episodes, ICSI, ICPI, PUF symptom scale, and VAS for pain all improved significantly compared with baseline; however, there were no differences between the groups over 12 months. The type of surgery, age, number of Hunner lesions, and maximal cystomteric capacity were not associated with the risk of recurrence. In safety analysis, in cases treated with transurethral resection, the incidence of bladder injury was 7.9%, which was slightly higher than that among patients treated with coagulation, which was 3.4%. Our findings did not suggest that one procedure was

superior to the other with regard to delaying recurrence. The choice of treatment did not affect the recurrence rate and produced comparable results, which may be because the ultimate peripheral denervation acted as the same thermal effect in both treatments.
