Bladder – Tissue and Systems

This article describes the basic anatomy and function of the human urinary bladder.  By having a better understanding of the bladder’s form and function, one might better interpret the symptoms that can occur with bladder cancer.  Bladder cancer is among the top ten most common causes of cancer in men as well as a leading cause of death from cancer in the United States.

In 2007, about 50,000 men and 17,000 women were found to have bladder cancer.  During this same time period there were about 14,000 deaths caused by bladder cancer.  Bladder cancer tends to occur in older adults and about 80% of newly found bladder cancer occurs in persons older than 60 years.  More than 2/3 of people with bladder cancer are men.  Bladder tumors occur more frequently in people of European descent.

There are a few different “bladders” in the body which have distinct functions.  The urinary bladder (or just bladder) is a hollow muscle that functions to store urine made by the kidneys.  Urine is made from filtering the blood and is mostly water with different types of nitrogen based waste products.  The average adult bladder holds about 500 mL.  The bladder normally has three “holes” or valves in it.  Each kidney normally sends one drainage tube or conduit to the bladder.  It is possible to have multiple ureters also.  The bladder has several layers of muscle that contribute to its flexibility and volume holding capacity.  The bladder sits in the pelvis.  In women the bladder is just below and in front of the uterus.  In men the bladder is just above the prostate gland.

The bladder has a robust blood supply with branches from the same arteries that supply the pelvis (i.e. the internal iliac arteries).  The bladder has lymph vessels that drain to the groin lymph nodes as well as the deep pelvic lymph nodes (i.e. external and internal iliac nodal basins).

The bladder has several distinct layers.  There is a transitional epithelial mucosa (the innermost layer that actually interfaces with urine), the lamina propria (a bundle of fibrous connective tissue), and a thick muscle layer.  The main muscle layer of the bladder is also known as the detrusor muscle.

The transitional epithelial layer is important because this is where the most common type of bladder cancer grows.  Understanding the different layers of the bladder is important as it helps explain the different types of bladder cancer that can occur.

Some different types of bladder tumors that occur include:

  • Urothelial transitional cell (most common, >90%)
  • Papillomas
  • Papillary urothelial cancer
  • Invasive urothelial cancer
  • Squamous Cell cancer
  • Adenocaricinoma
  • Many others possible types 

The relationship of the bladder to neighboring structures helps explain the occurrence of many different types of symptoms.  Normally the urine and bladder are entirely free of germs or sterile.  Infection in the kidneys, urine, or bladder can cause fever, pain with urination as well as tenderness in the area of the bladder.  Inflammation of the bladder is known as cystitis.  The uterus in women sits just on top and slightly behind the bladder.  Normally this is inconsequential, but with pregnancy it becomes quite obvious.  As the fetus (and the uterus) grows during pregnancy it places pressure on the bladder causing the holding capacity to decrease.  This explains why pregnant women have to urinate frequently and often in small amounts.  The functional capacity of the bladder is greatly diminished during pregnancy and particularly so during the third trimester.

The prostate sits around the outlet valve of the bladder.  As a man ages it is possible for the prostate to enlarge to some degree.  If the prostate enlarges greatly, it can interfere with emptying of the bladder causing pain or pressure with urination and many other associated problems.  The drainage ducts of the kidneys are called the ureters.  The ureters tunnel themselves into the bladder in a special way in order to help prevent reflux or “backwash” of urine from the bladder back towards the kidneys.  If this valve mechanism is dysfunctional (also known as vesicoureteral reflux) it can cause problems with infection or even kidney failure.

Other structures nearby include the colon and sometimes the small intestine.  When the colon becomes inflamed it is possible for an abnormal connection between the colon and bladder to occur.  This is known as a colovesical fistula.  This usually causes infection in the bladder as well as passage of stool and air in the urine which is unsettling to say the least.

As mentioned, the bladder has a very vigorous blood supply and most bladder tumors that disrupt the surface of the bladder will cause some bleeding into the urine.  This is why bloody urine is one of the most common symptoms of bladder cancer.

Certain lifestyle habits and risk factors are associated with bladder cancer.  The most common one is cigarette smoking.  Other risk factors include certain chemotherapy drugs (such as cyclophosphamide), bladder stones, multiple bladder infections, and certain types of occupational chemical exposures such as aromatic amines used in manufacturing dyes.

REFERENCES:

  1. www.cancer.gov/cancertopics/pdq/treatment/bladder/Patient/page1
  2. www.nlm.nih.gov/medlineplus/bladdercancer.html
  3. Diagnosis and treatment of bladder cancer.  Sharma S, Ksheersagar P, Sharma P.  Am Fam Physician. 2009 Oct 1;80(7):717-23. Review.  PMID:19817342
  4. Townsend Jr, CM; Beauchamp RD; Evers BM; Mattox KL. (2008) Townsend: Sabiston Textbook of Surgery, 18th ed.  Chapter 77.  New York, NY: Saunders.
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.