Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic condition characterized by persistent pelvic pain related to the urinary bladder, often accompanied by increased urinary frequency and urgency. IC/BPS is a spectrum of clinical presentations, but a distinct and more severe subtype is defined by the presence of specific patches of inflammation known as Hunner lesions. Patients with Hunner lesions are clinically and pathologically different from those without them, representing a clear inflammatory entity often referred to as Classic IC. This phenotype is found in a minority of IC/BPS patients, estimated at between 5% and 10% of the overall population with the condition.
Identifying Characteristics and Pathology
A Hunner lesion presents as a circumscribed, reddened area on the bladder’s mucosal lining. These areas are fragile and often bleed easily when touched or stretched, leading to the historical term “Hunner’s ulcers,” though they are not true ulcers. The lesion frequently appears to have small blood vessels radiating toward a central, pale scar or fibrin deposit. This visual characteristic makes the lesion highly distinctive during an endoscopic examination.
The underlying pathology involves a pronounced, full-thickness inflammatory process within the bladder wall. Histological analysis reveals the infiltration of various inflammatory cells, distinguishing this subtype from non-lesion IC/BPS. There is an increase in immune cells, such as mast cells and lymphoplasmacytic cells, found within the lining and deeper layers of the bladder tissue. These lesions also exhibit significant epithelial denudation, meaning the protective glycosaminoglycan (GAG) layer has been stripped away or damaged in that localized area.
The loss of this protective layer exposes the underlying tissue to irritating substances in the urine, driving the cycle of inflammation and pain. This chronic inflammation and tissue damage cause the bladder wall to become less flexible and more sensitive. The severe inflammation and subsequent scarring can lead to a reduced functional bladder capacity, which directly contributes to the urinary urgency and frequency experienced by patients. This concentrated, immunologically-driven damage makes the Hunner lesion a localized source of symptoms.
Specific Diagnostic Procedures
The presence of a Hunner lesion must be confirmed through a specialized procedure called cystoscopy with hydrodistention, performed under general or spinal anesthesia. Cystoscopy alone, performed in an office setting, is often inadequate because the lesions may not be visible when the bladder is not fully distended. Anesthesia is required because stretching the bladder wall to its capacity can cause intense pain in patients with IC/BPS.
During the procedure, the bladder is slowly filled with fluid, a process known as hydrodistention, which stretches the tissue. This distention allows for a comprehensive inspection of the entire bladder wall, making the lesions visible. The classic findings include a reddened mucosal area that splits or cracks upon full distention. Upon draining the fluid, the hallmark sign is the distinct “waterfall” effect, where blood oozes from the cracked mucosal area.
The procedure may also reveal petechial hemorrhages, or tiny bleeding spots, referred to as glomerulations. While glomerulations can be found in other forms of IC/BPS, the Hunner lesion is the specific marker defining this subtype. A biopsy of the lesion site may be taken to confirm the diagnosis and exclude other serious conditions like carcinoma in situ, as the visual appearance can sometimes be similar. The biopsy confirms the chronic inflammatory changes and the presence of inflammatory cells.
Targeted Treatment Strategies
Treatment for Hunner lesions focuses specifically on the localized destruction or modification of the lesion itself, differing from general treatments used for non-lesion IC/BPS. One effective intervention is fulguration, also known as cauterization, which uses electricity or a laser to burn away the lesion. This procedure aims to eradicate the damaged tissue, and patients frequently experience significant symptom improvement, sometimes up to 90%. However, this method carries a risk of causing scarring, which could potentially reduce the bladder’s capacity over time.
Another targeted surgical approach is transurethral resection, where a specialized instrument is used to surgically cut out the lesion. Resection is typically reserved for larger lesions and is sometimes preferred over fulguration to minimize thermal damage to the surrounding healthy bladder tissue. The goal of both fulguration and resection is the complete removal of the diseased tissue to promote healing and alleviate the source of localized inflammation and pain. These procedures are typically performed during the same anesthetic session as the diagnostic hydrodistention.
A less invasive, yet highly targeted, strategy involves local injections of medication directly into the lesion site. Corticosteroids, such as triamcinolone, are injected into the lesion’s center and periphery to reduce intense local inflammation. This approach is sometimes used as a first-line targeted treatment to avoid the scarring associated with fulguration. The efficacy of steroid injections is comparable to fulguration in terms of symptom improvement, offering substantial relief from pain and urinary urgency.
While these localized treatments are effective at providing immediate symptom relief, the lesions have a high tendency to recur. Approximately 50% of patients require a repeat procedure within a few years as the inflammation returns to the area. Therefore, managing Hunner lesions often requires ongoing monitoring and repeated treatments to maintain long-term symptom control and quality of life. The recurrence highlights the chronic, persistent nature of the underlying inflammatory process in this specific type of IC/BPS.