Metaplasia of the nonkeratinizing squamous epithelium in the bladder trigone is known as trigonitis, which is assumed to develop under the influence of estrogen and inflammation. These epithelial changes can produce symptoms such as increased frequency of micturition and urgency. Cystoscopy with biopsy and subsequent histopathological examination is necessary to make the diagnosis.
Trigonitis is a term denoting metaplastic changes in the bladder epithelium (conversion of transitional to squamous nonkeratinizing), and since its description at the beginning of the 20th century, very few reports exist in the literature   . Inflammatory events occurring in the bladder were initially assumed to be the main pathogenic stimulus for this epithelial change, and bacterial infections of the lower urinary tract (eg. cystitis) are considered as a possible risk factor for trigonitis . It was subsequently confirmed, however, that the effect of estrogens on the bladder epithelium is the principal mechanism of this change  . Consequently, trigonitis is almost always diagnosed in females of childbearing age, as only six male cases have been reported   so far. The main symptoms are frequent micturition and a sense of urgency  . Moreover, studies have identified that the presence of pelvic and/or urethral pain is strongly associated with trigonitis, as well as dysuria  .
Given the nonspecific clinical presentation of lower urinary tract symptoms, the diagnosis is difficult. Firstly, it is necessary to rule out more common causes of such complaints, such as infections, which is why a thorough patient history that will assess the course and progression of symptoms, and a detailed physical examination that focuses on abdominal palpation and observation of vital signs and other systems, are necessary steps in the workup. Pharmacologic administration of estrogen was reported in males to be a precipitating event, thus male patients could be asked about recent medication . Urinalysis in the setting of trigonitis reveals a sterile urine culture and normal findings . As the diagnosis is not yet confirmed, more advanced urological procedures should be employed. Ultrasonography (US) is of limited use (although it may show thickening of the bladder neck) , while cystoscopy is the gold standard for diagnosis. A grayish mucosa with a hyperemic margin in the trigone area is considered highly specific for trigonitis . In presence of clinical suspicion, a biopsy sample for histological examination is recommended. The diagnosis is confirmed when the non-keratinizing squamous epithelium is seen instead of the standard transitional epithelium of the bladder on light microscopy  .