home > diseases, conditions and tests a-z list > bladder cancer article

Bladder Cancer
(Cancer of the Urinary Bladder)

Medical Author:

Kevin C. Zorn, MD, FRCSC, FACS

Medical Author:

Gagan Gautam, MD, MCh

Medical Editor:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

View Full Profile

What is the bladder?

The urinary bladder, or the bladder, is a hollow organ present in the pelvis. Most of it lies behind the pubic bone of the pelvis but when full it can extend up into the lower part of the abdomen. Its primary function is to store urine that drains into it from the kidney through tube-like structures called the ureters. The ureters from both the kidneys open into the urinary bladder. The bladder forms a low-pressure reservoir which gradually stretches out as urine fills into it. In males, the prostate gland is located adjacent to the base of the bladder where urethra joins the bladder. From time to time, the muscular wall of the bladder contracts to expel urine through the urinary passage (urethra) into the outside world.

What are the layers of the bladder?

The bladder consists of three layers of tissue. The innermost layer of the bladder which comes into contact with the urine stored inside the bladder is called the "mucosa" and consists of several layers of specialized cells called "transitional cells," which are almost exclusively found in the urinary system of the body. These same cells also form the inner lining of the ureters, kidneys, and a part of the urethra. These cells form a waterproof lining within these organs to prevent the urine from going into the deeper tissue layers.

The middle layer is a thin lining known as the "lamina propria" and forms the boundary between the inner "mucosa" and the outer muscular layer. This layer has a network of blood vessels and nerves and is an important landmark in terms of the staging of bladder cancer (described in detail below in the bladder cancer staging section).

The outer layer of the bladder comprises of the "detrusor" muscle and is called the "muscularis." This is the thickest layer of the bladder wall. Its main function is to relax slowly as the bladder fills up to provide low-pressure urine storage and then to contract to compress the bladder and expel the urine out during the act of passing urine. Outside these three layers is a variable amount of fat which lines and protects the bladder like a soft cushion and separates it from the surrounding organs such as the rectum and the muscles and bones of the pelvis.

Picture of the urinary system: kidneys, ureters, and bladder

What is bladder cancer?

Bladder cancer is an uncontrolled abnormal growth and multiplication of cells in the urinary bladder which have broken free from the normal control mechanisms of the body. Bladder cancer (like cancers of other organs) has the ability to spread (metastasize) to other body parts including the lungs, bones, and liver.

Bladder cancer invariably starts from the innermost layer of the bladder (for example, the mucosa) and may invade into the deeper layers as it grows. Alternately, it may remain confined to the mucosa for a prolonged period of time. Visually, it may appear in various forms. Most common is a shrub-like appearance (papillary) but it may also appear as a nodule, an irregular solid growth or a flat, barely perceptible thickening of the inner bladder wall (details in subsequent sections).