**3.6 Technique of transurethral coagulation and resection of Hunner lesion**

To coagulate or resect the Hunner lesion, the most important first step is to demarcate the lesion with the cautery before full bladder distension. Complete coagulation of the inside Hunner lesion of the boundary should then be performed. If starting from the inside of the lesion and working outward, reactive erythema spreads outward and obscures the original boundary of the lesion. In the case of transurethral resection, it is effective to use a bipolar loop. During the resection, resection should be performed as deeply as possible to the muscle layer using a cutting current. However, bladder damage can easily occur because the bladder wall of Hunner lesion is thin and friable. To prevent bladder injury, the quantity of irrigation fluid should be kept constant through suction attached to the outer sheath. Using this approach, the risk of bladder damage can be reduced by preventing the overdistension of bladder. Nevertheless, when it is difficult to complete resect the Hunner lesion or when the surgeon does not have extensive experience for transurethral resection, transurethral coagulation alone may be enough to control Hunner lesions.
