What is bladder cancer?
Bladder cancers are malignant tumors arising from the urinary bladder, the hollow reservoir that holds urine exiting the kidney. The most common form of bladder cancer are those that arise from the urothelial lining of the bladder and are known urothelial tumors or transitional cell carcinomas. This urothelial lining is present in the entire urinary tract, including the renal pelvis, ureters, bladder and urethra, but most urothelial malignancies occur in the bladder.
There are other types of malignant bladder tumors like squamous cell carcinomas, adenocarcinomas and small-cell carcinomas and giant cell carcinomas but these types of cancer are fairly uncommon. Sarcoma, melanoma and lymphomas of bladder are extremely rare. Bladder cancer is more common in men and the risk of of developing bladder cancer increases with age.
Symptoms of Bladder Cancer
The first and most common symptom of bladder cancer is painless hematuria, which is present in the early stages of the diseases. Painless hematuria is the passing of blood in the urine without any pain. There are various other causes of painless hematuria and the presence of blood needs to be confirmed with a urine dipstick as certain foods and beverages can also discolor the urine. Hematuria may be microscopic where no changes can be seen in the urine with the naked eye or it may color the urine dark yellow, to red or dark brown.
Although painless hematuria can occur on its own before the onset of other symptoms, other urinary complaints may also arise with time. These symptoms closely resemble a urinary tract infection and include frequent urination, painful urination (dysuria) and an urgency to urinate. A person with bladder cancer is also more prone to urinary tract infections. Patients may also complain of a weak bladder as the bladder capacity may be reduced.
Some patients do present with bladder pain at an early stage, while in other cases, pelvic and abdominal pain may only emerge later in the disease. The pain may refer to the lower back and also cause rectal discomfort. If the opening of the ureter in the bladder is affected, then patients may report flank pain and reduced kidney function. Refer to kidney pain location.
In advanced bladder cancer, patients may report a loss of appetite and malaise. Unintentional weight loss is often present in these stages and with metastases to the bone, bone pain and fractures may also be seen.
Causes of Bladder Cancer
The exact cause of bladder cancer, like many other diseases, cannot always be conclusively identified. Although various people may be exposed to the same risk factors, bladder cancer will not arise in every person. However, bladder cancer is associated with three broad categories of risk factors :
- chemical agents
- chronic irritation
- gene abnormalities
Bladder Cancer : Chemicals
The chemical agents believed to increase the risk of bladder cancer usually come in contact with the bladder directly or in the form of its metabolites. Cigarette smoking is considered to be the most important risk factor for bladder cancer. An aromatic amine, 2-naphthylamine, found in cigarette smoke is believed to be responsible for the carcinogenic effects in bladder. It is believed to be responsible for almost 50% of the bladder cancers in men and about 25% of bladder cancer in women. Long term exposure to smoking increases the risk to greater degree than heavy smoking for shorter period. Chronic smokers have a two to three-fold risk of developing bladder cancer compared to non-smokers.
Chemicals associated with increased bladder cancer risk are polycyclic aromatic amines, arylamines, aniline dyes, nitrites and nitrates. Bladder cancer has been associated with certain occupations that increase exposure to some of these chemical carcinogens. This may include workers in the following industries – aluminum, dye, rubber, plastics, leather, coal and tar workers, dry cleaning, manufacturing of certain preservatives and polychlorinated biphenyls which is used in various products.
Cyclophosphamide administration over long term can increase the risk of bladder cancer, particularly in patients who have difficulty in emptying bladder (bladder-outlet obstruction).
Bladder Cancer : Chronic Inflammation
Chronic irritants that can lead to bladder cancer are bladder worm (Schistosoma haematobium) infection, indwelling catheters, chronic bladder stones and radiation.
Schistosoma infestation can increase the risk of squamous cell carcinoma in addition to transitional cell carcinoma (TCC) in the bladder. The infection results in enhanced formation of N-nitroso compounds which are known carcinogens.
Patients with indwelling catheters or chronic bladder stones are often associated chronic irritation of bladder that increases the risk for the development of squamous cell carcinoma of bladder.
Radiation of the pelvis also increases the risk of squamous cell carcinoma of bladder.
Bladder Cancer : Genetic Factors
The risk factors for bladder cancer that involves genetic abnormalities include mutations of tumor suppressor genes (like p21, p27, p53, and retinoblastoma gene), expression of protooncogenes (like Ras p21 proteins) and abnormalities of certain genes involving regulatory proteins of the cell cycle (like cyclin D1 and Ki-67). Chromosome 9 deletions are the most frequent chromosomal change observed in association with bladder cancer.