Approach Considerations
Cystoscopy is necessary to make the diagnosis of trigonitis. Urinalysis and urine culture can be performed to exclude infection, as is often done prior to cystoscopy. Imaging studies are not necessary to confirm the diagnosis. However, in one study of transabdominal ultrasonography, women with asymptomatic, cystoscopically-confirmed trigonitis had thickening of the mucosa around the bladder neck, compared with women who had cystoscopically normal bladders. [17]
Procedures
Cystoscopy is necessary to make the diagnosis. Grossly, the lesion appears as a glistening, fluffy white patch of bladder mucosa with well-defined borders. See the image below.
Cystoscopic appearance of trigonitis as a well-defined white area overlying the trigone.
Biopsy of suspected trigonitis can usually be deferred, as trigonitis has a distinct gross appearance under cystoscopy. However, a lower threshold for biopsy is warranted when there is a higher likelihood that the lesions are leukoplakia, such as in the following cases:
-
Male patients
-
Females with hematuria
-
Pediatric patients
-
Patients with a similar appearing lesion outside of the confines of the trigone
Histologic Findings
Nonkeratinizing squamous metaplasia of the trigone is composed of stratified squamous epithelium that often contains abundant glycogen. The basal cell layer has prominent nuclei with condensed chromatin and nucleoli. The surface cells are linked by desmosomes and are longitudinally oriented. Jost et al found the mitotic index within these lesions to be 0.17%, higher than the expected value of 0%. [18] See the image below.
Nonkeratinizing squamous metaplasia. Stratified squamous metaplasia is usually seen in the bladder neck and trigone. Note the lack of densely eosinophilic layer, representing keratin, at the luminal side.
-
Keratinizing squamous metaplasia of the bladder.
-
Cystoscopic appearance of trigonitis as a well-defined white area overlying the trigone.
-
Nonkeratinizing squamous metaplasia. Stratified squamous metaplasia is usually seen in the bladder neck and trigone. Note the lack of densely eosinophilic layer, representing keratin, at the luminal side.
