An enlarged bladder, also referred to as bladder hypertrophy, is a medical condition in which the bladder becomes larger than normal, stretches too much, or develops thicker walls. Some people also are born with an enlarged bladder. In other cases, the condition may develop as the result of an obstruction of some sort. Sometimes, a person may even develop an enlarged bladder because of an abnormally high volume of urine output or failure to empty the bladder fully on a regular basis.

A person may be born with an enlarged bladder. Since the bladder is larger than normal, it may stick out past the point it should instead of being held in place by the surrounding body tissues. A bladder that extends in this manner may impair the normal function of other organs, such as the kidneys, even though the bladder itself may function normally. Sometimes this causes the patient's urine flow to become blocked, making it difficult or even impossible for the patient to empty his bladder fully. In such a case, he may undergo surgery to correct this problem.

Often, a case of an enlarged bladder occurs when something blocks the urinary tract. The cause of the obstruction may gradually impact the walls of the patient’s bladder, stimulating bladder wall thickening over a period of time. After a significant time period, the walls of the bladder may thicken enough to make the whole organ larger than normal. In some cases, the obstruction is caused by a tumor, which may be benign, meaning not cancerous, or malignant, which means cancerous; sometimes bladder stones cause this issue as well. Surgery is often used to remove the obstruction in such a case, and the bladder often returns to its normal size after the surgical procedure is complete.

An individual may be diagnosed with an enlarged bladder after the organ becomes stretched due to urine retention or an abnormally large volume of urine output. For example, a person may have trouble emptying his bladder fully and may constantly retain a bit of urine. Likewise, some people have medical conditions that cause their bodies to produce more urine than normal. Both of these situations can lead to the stretching of the bladder, and correcting the underlying cause of these conditions may allow the bladder to return to a more normal size. If stretching is severe, however, the bladder may not regain its normal tone.