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The bladder is an organ located in the pelvic cavity that stores and discharges urine. Urine is produced by the kidneys, carried to the bladder by the ureters, and discharged from the bladder through the urethra. Bladder cancer accounts for approximately 90% of cancers of the urinary tract (renal pelvis, ureters, bladder, urethra).
Bladder cancer usually originates in the bladder lining, which consists of a mucous layer of surface cells that expand and deflate (transitional epithelial cells), smooth muscle, and a fibrous layer. Tumors are categorized as low-stage (superficial) or high-stage (muscle invasive). In industrialized countries (e.g., United States, Canada, France), more than 90% of cases originate in the transitional epithelial cells (called transitional cell carcinoma; TCC). In developing countries, 75% of cases are squamous cell carcinomas caused by Schistosoma haematobium (parasitic organism) infection. Rare types of bladder cancer include small cell carcinoma, carcinosarcoma, primary lymphoma, and sarcoma.
Incidence & Prevalence
According to the National Cancer Institute, the highest incidence of bladder cancer occurs in industrialized countries such as the United States, Canada, and France. Incidence is lowest in Asia and South America, where it is about 70% lower than in the United States. Incidence of bladder cancer increases with age. People over the age of 70 develop the disease 2 to 3 times more often than those aged 55–69 and 15 to 20 times more often than those aged 30–54. Bladder cancer is 2 to 3 times more common in men. In the United States, approximately 38,000 men and 15,000 women are diagnosed with the disease each year. Bladder cancer is the fourth most common type of cancer in men and the eighth most common type in women. The disease is more prevalent in Caucasians than in African Americans and Hispanics.
Causes & Risk Factors
Cancer-causing agents (carcinogens) in the urine may lead to the development of bladder cancer. Cigarette smoking contributes to more than 50% of cases, and smoking cigars or pipes also increases the risk. Other risk factors include the following:
- Chronic bladder inflammation (recurrent urinary tract infections, urinary stones)
- Consumption of Aristolochia fangchi (herb used in some weight-loss formulas)
- Diet high in saturated fat
- Exposure to second-hand smoke
- External beam radiation
- Family history of bladder cancer (several genetic risk factors identified)
- Gender (male)
- Infection with Schistosoma haematobium (parasite found in many developing countries)
- Personal history of bladder cancer
- Race (Caucasian)
- Treatment with certain drugs (e.g., cyclophosfamide—used to treat cancer)
Exposure to carcinogens in the workplace also increases the risk for bladder cancer. Medical workers exposed during the preparation, storage, administration, or disposal of antineoplastic drugs (used in chemotherapy) are at increased risk. Occupational risk factors include recurrent and early exposure to hair dye, and exposure to dye containing aniline, a chemical used in medical and industrial dyes. Workers at increased risk include the following:
- Truck drivers
- Workers in rubber, chemical, textile, metal, and leather industries
Signs and Symptoms -The primary symptom of bladder cancer is blood in the urine (hematuria). Hematuria may be visible to the naked eye (gross) or visible only under a microscope (microscopic) and is usually painless. Other symptoms include frequent urination and pain upon urination (dysuria).
Diagnosis -Diagnosis of bladder cancer includes urological tests and imaging tests. A complete medical history is used to identify potential risk factors (e.g., smoking, exposure to dyes). Laboratory tests may include the following:
- Urinalysis (to detect microscopic hematuria)
- Urine cytology (to detect cancer cells by examining cells flushed from the bladder during urination)
- Urine culture (to rule out urinary tract infection)
Various imaging tests may also be performed. Intravenous pyelogram (IVP) is the standard imaging test for bladder cancer. In this procedure, a contrast agent (radiopaque dye) is administered through a vein (intravenously) and x-rays are taken as the dye moves through the urinary tract. IVP provides information about the structure and function of the kidneys, ureters, and bladder. Other imaging tests include CT scan, MRI scan, bone scan, and ultrasound.
If bladder cancer is suspected, cystoscopy and biopsy are performed. Local anesthesia is administered and a cystoscope (thin, telescope-like tube with a tiny camera attached) is inserted into the bladder through the urethra to allow the physician to detect abnormalities. In biopsy, tissue samples are taken from the
lesion(s) and examined for cancer cells. If the sample is positive, the cancer is staged using the tumor, node, metastases (TNM) system.