Cystitis: Inflammation of the bladder. Cystitis can be due for example to infection from bacteria that ascend the urethra (the canal from the outside) to the bladder.

Symptoms include a frequent need to urinate, often accompanied by a burning sensation. As cystitis progresses, blood may be observed in the urine and the patient may suffer cramps after urination. In young children, attempts to avoid the pain of cystitis can be a cause for daytime wetting (enuresis). Treatment includes avoiding irritants, such as perfumed soaps, near the urethral opening; increased fluid intake; and antibiotics. Untreated cystitis can lead to scarring and the formation of stones when urine is retained for long periods of time to avoid painful urination.