What Is an Inability to Urinate?
Urinary retention is the inability to completely empty your bladder. Urinary retention may be sudden in onset (acute) or gradual in onset and chronic (long-standing). When you cannot empty your bladder completely, or at all, despite an urge to urinate, you have urinary retention. To understand how urinary retention occurs, it is important to understand the basics of how urine is stored in and released from the body.
The bladder is a hollow balloon-like organ in the lower part of the belly (pelvis) that stores and eliminates (expels) urine.
- Urine is composed of waste chemicals and water filtered from the blood by the kidneys.
- It travels down two thin tubes called ureters (one from each kidney) to empty into the bladder.
- When about 1 cup (200 ml-300 ml) of urine has collected in the bladder, a signal is produced from nerves within the bladder wall in response to filling and stretching of the bladder. This signal is sent to the nerves in the spinal cord and ultimately to the brain. The brain controls the bladder and when it is appropriate to urinate, the brain returns a signal that starts contractions in the bladder wall. Prior to the contraction of the bladder, the muscles surrounding the outlet of the bladder, bladder neck, as well as the muscles surrounding the urethra, relax. This is coordinated (synergistic) urination.
- Urine leaving the bladder passes through the urethra, a hollow tube that is surrounding by muscles.
- Control of urination is for the most part voluntary. One can suppress an urge to urinate by contracting one's pelvic muscles. However, if one tries to hold it too long, urinary incontinence often results. Overactivity of the bladder muscle can also cause incontinence.
Urinary retention is often subdivided into different categories. Urinary retention may be complete in that one is unable to urinate at all, despite having a full bladder. Partial urinary retention is the ability to urinate in small amounts but leaving a large amount in the bladder after each urination. Urinary retention may be acute, occurring suddenly; one feels the need to urinate and cannot urinate at all even despite having a full bladder, or chronic, when one does not empty one's bladder completely. Acute urinary retention is often uncomfortable. Chronic urinary retention is typically not painful (asymptomatic). The amount of urine left behind to be considered chronic urinary retention is not well defined; some state that it is 300 cc (a little over an 8 ounce cupful), yet others state that it is >400 cc. Urinary retention may be due to an obstruction to the outflow of urine or nonobstructive. Lastly, urinary retention can be associated with high bladder pressures or low bladder pressures. The International Continence Society defines chronic urinary retention as a non-painful bladder, which remains palpable or percussable (tapping on the lower abdomen elicits a hollow sound) after the individual has urinated.
Urinary retention may cause harm to the function of the bladder and the kidneys, incontinence, and may increase the risk of urinary tract infections. Thus, it requires urgent medical attention for evaluation and management. In some cases, hospitalization is required.
Urinary retention is not an unusual medical condition, and it is more common in men than in women.