Bladder distension can be caused by a variety of reasons, as follows: 1, inflammatory stimulation: such as acute and chronic cystitis, adenoidal cystitis, etc., mostly in female patients, often accompanied by different degrees of urinary frequency, urinary urgency, urinary pain, etc. 2, prostatitis: obstruction of the bladder outlet, resulting in different degrees of urinary retention, can cause bladder distension, such as the most common cause is prostatic hyperplasia in middle-aged and elderly men, appearing progressive difficulty in urination, forming different degrees of chronic urinary retention, it can cause bladder distension. 3, factors of other diseases: long-term diabetes, cerebrovascular disease, complications caused by trauma to the cerebral spinal cord, can occur in different degrees of urinary retention, can also occur bladder distension. 4, holding urine: if you have the habit of holding urine, a long time will also appear bladder distension. 5, bladder stones, bladder tumors: sometimes can also cause bladder distension and pain.