The Trigone of the Bladder: A High-Risk Site for Bladder Cancer
The inner surface of the bladder is lined by mucosa. When the bladder wall contracts, the mucosa gathers into folds called bladder rugae. On the internal surface of the bladder base, between the ureteric orifices on both sides and the internal urethral orifice, there is a triangular area where the mucosa is tightly attached to the muscular layer and lacks a submucosal layer. Regardless of whether the bladder is distended or contracted, this area remains smooth and is called the trigone of the bladder. The trigone is a predilection site for tumors, tuberculosis and inflammation.
If painless gross hematuria occurs, cystoscopy should be performed with special attention to the trigone. Painless gross hematuria is a typical symptom of bladder cancer; about 80-90% of bladder cancer patients present with painless hematuria as the first symptom, with urine looking like wash water, tea-colored or bright red. This symptom may appear suddenly and then disappear on its own. As a result, patients often neglect it and miss the opportunity for early detection.
Besides painless gross hematuria, bladder cancer may be accompanied by urinary frequency, urgency and dysuria; these symptoms are more common when the tumor invades the trigone or when infection is present. Advanced bladder cancer may also cause lower abdominal pain, progressive weight loss and anemia; obstruction of the ureter by the tumor can lead to hydronephrosis and renal colic.
Why is the trigone a high-risk site for tumors, inflammation and tuberculosis? It is related to its unique anatomy, urine stasis and chronic irritation. The trigonal mucosa is thin and lacks a submucosal layer, directly contacting the muscular layer, which makes it easily irritated by carcinogens or inflammatory substances in urine. In addition, the trigone is the final storage area before urine is expelled; urine flows slowly here and stays for a long time, and this region has a rich nerve supply, all of which predispose it to abnormal hyperplasia.
To prevent bladder cancer, avoid holding urine. The longer urine stays in the trigone, the more easily carcinogens such as nitrosamines and aromatic amines become trapped and concentrated there; long-term exposure can damage the DNA of trigonal epithelial cells and lead to carcinogenesis. Of course, bladder cancer has complex causes and is not solely caused by urinary retention. Smoking and prolonged sitting are also high-risk factors, and bladder cancer has some genetic component. We can reduce the incidence of bladder cancer by improving lifestyle.