Trigonitis

Overview

Trigonitis refers to inflammation of the trigone, a triangular area at the base of the bladder bounded by the two ureteric openings and the internal urethral opening. This region has a different embryological origin than the rest of the bladder, contains estrogen receptors, and represents the most sensitive area within the bladder wall.

The term trigonitis most commonly describes pseudomembranous trigonitis, also called vaginal metaplasia of the trigone. In this condition, the normal bladder lining in the trigone area transforms to resemble vaginal tissue. Cystoscopy reveals white or pale opaque patches with a slightly raised, irregular surface localized to the trigone. This finding occurs in approximately 40% of women undergoing cystoscopy and increases with age. It is rarely found in men.

The clinical significance of pseudomembranous trigonitis remains debated. Many women with this finding on cystoscopy have no symptoms at all—it is discovered incidentally during investigation for other concerns. When symptoms do occur, distinguishing whether trigonitis is the actual cause or simply an accompanying finding requires careful evaluation to exclude other conditions.

True inflammatory trigonitis, where the trigone appears red and inflamed rather than showing metaplastic changes, may indicate infection or another underlying condition and typically warrants further investigation.

Symptoms

Many women with trigonitis on cystoscopy experience no symptoms whatsoever. When symptoms do occur, they closely mimic urinary tract infection despite negative urine cultures.

Irritative urinary symptoms predominate, including urinary frequency, urgency, and dysuria or burning with urination. Suprapubic discomfort or pressure is common, often worsening as the bladder fills and improving after voiding. Some women experience lower abdominal pain or pain during intercourse.

The symptom pattern creates significant diagnostic confusion. Women may undergo repeated courses of antibiotics for presumed UTI despite persistently negative cultures. This pattern of UTI-like symptoms without documented infection should prompt consideration of trigonitis, interstitial cystitis, or painful bladder syndrome.

Causes

The exact cause of pseudomembranous trigonitis remains unknown. The trigone’s unique embryological origin and its concentration of estrogen receptors suggest hormonal influences play a role. Some researchers consider these changes a normal variant in women rather than a true pathological process.

Chronic irritation from recurrent urinary infections may contribute to trigone changes in some cases. The metaplastic tissue appears similar to vaginal epithelium, supporting the theory of estrogen-driven transformation.

True inflammatory trigonitis may result from ongoing infection, sexually transmitted infections affecting the lower urinary tract, chemical irritation, foreign bodies such as bladder stones or catheters, or radiation exposure. Rarely, inflammatory changes in the trigone may indicate carcinoma in situ, making biopsy important when the appearance is atypical or concerning.

Diagnosis

Cystoscopy provides the definitive diagnosis. Pseudomembranous trigonitis appears as white or pale opaque patches with defined borders, localized specifically to the trigone area. True inflammatory trigonitis shows a red, edematous mucosa that may have petechiae or small bleeding spots and can extend beyond the trigone.

Biopsy may be performed to confirm the diagnosis and rule out carcinoma in situ, particularly when the appearance is unusual. Histologically, pseudomembranous trigonitis shows squamous metaplasia—vaginal-type cells replacing the normal bladder urothelium.

Urinalysis is typically normal in trigonitis, and urine culture is negative for bacterial growth. Cytology may be performed if there is concern for malignancy.

Before attributing symptoms to trigonitis, other conditions must be excluded. Urinary tract infection requires culture confirmation. Interstitial cystitis/bladder pain syndrome presents with similar symptoms and may coexist with trigonitis. Overactive bladder focuses primarily on urgency and frequency. Carcinoma in situ, though rare, must be excluded through biopsy. Postmenopausal atrophic changes affecting the bladder can cause similar symptoms and respond to estrogen therapy.

Treatment

Asymptomatic trigonitis discovered incidentally requires no treatment. Reassurance that this is a benign finding is appropriate. The condition is not premalignant and does not require regular surveillance beyond routine care.

For symptomatic cases, treatment remains largely empirical with variable results. No single approach works consistently, and management often requires trial of multiple strategies.

Hormonal therapy represents a first-line option for many women. Vaginal estrogen in cream, tablet, or ring form may reduce symptoms, particularly in postmenopausal women with estrogen deficiency. Some clinicians trial vaginal estrogen even in premenopausal women given the trigone’s estrogen responsiveness.

Antibiotics have no role in treating uncomplicated pseudomembranous trigonitis unless active infection is documented. Empirical antibiotic courses are sometimes tried but lack supporting evidence for this specific indication.

Bladder instillations using agents similar to those employed for interstitial cystitis—such as dimethyl sulfoxide, heparin, or lidocaine—may provide relief for some patients. These treatments are typically reserved for cases that fail more conservative measures.

Lifestyle modifications often help manage symptoms. Reducing bladder irritants such as caffeine, alcohol, acidic foods, and artificial sweeteners can decrease symptom severity. Adequate hydration, regular voiding before the bladder becomes overly full, and pelvic floor relaxation techniques may provide additional benefit.

Cystoscopy with fulguration—burning the affected tissue—has been used historically but remains controversial. Evidence supporting this approach is limited, and symptoms may recur.

When to See a Doctor

Women experiencing persistent UTI-like symptoms despite negative urine cultures should seek evaluation for possible trigonitis or related conditions. Symptoms that significantly impact quality of life warrant specialist referral to a urologist or urogynecologist.

Seek prompt evaluation if symptoms worsen significantly, blood appears in the urine, fever develops, or new symptoms arise. These may indicate a different or additional condition requiring investigation.

If initial treatments prove ineffective, a multidisciplinary approach involving urology, gynecology, and potentially pelvic floor physical therapy may be beneficial. Trigonitis often overlaps with or accompanies conditions like interstitial cystitis and pelvic floor dysfunction, and addressing contributing factors from multiple angles improves outcomes for some patients.