A urinary catheter is needed whenever your bladder can’t empty on its own, when doctors need precise measurements of urine output, or when surgery requires one. The most common reason is urinary retention, where urine stays trapped in the bladder. Catheters are also used during certain surgeries, for people with nerve damage affecting bladder control, and in some cases to protect healing wounds or provide comfort during end-of-life care.
Urinary Retention
The single most common reason for catheterization is urinary retention, meaning your bladder fills but you can’t fully empty it. This can come on suddenly (acute) or develop gradually over time (chronic). An enlarged prostate is the most frequent cause overall. Kidney stones, scar tissue narrowing the urethra, or tumors pressing on the bladder can also block urine flow. Acute urinary retention from an enlarged prostate is one of the most painful urological emergencies, and the immediate treatment is draining the bladder with a catheter.
Retention doesn’t always come from a physical blockage. Certain medications, particularly those with anticholinergic effects (found in some allergy, depression, and overactive bladder drugs), can suppress the bladder’s ability to contract. Infections like prostatitis in men or severe urinary tract inflammation can also temporarily prevent normal voiding. Once the underlying cause is treated, the catheter is typically removed to see if you can urinate on your own again.
Doctors use a specific measurement called post-void residual volume to determine how well your bladder empties. If more than 200 mL of urine remains after you’ve tried to urinate, that signals inadequate emptying. Anything over 400 mL is generally diagnostic of urinary retention and typically calls for catheterization.
Before, During, and After Surgery
Catheters are placed for most surgeries involving the abdomen or pelvis, including urological and gynecological procedures. Even for surgeries that don’t directly involve the urinary tract, a catheter may be inserted if the operation is expected to last a long time, if you’ll receive large volumes of IV fluids or diuretics, or if the surgical team needs to closely track how much urine your kidneys are producing during the procedure.
If the catheter was placed solely because of a long surgery, CDC guidelines recommend it be removed in the recovery room. For routine abdominal surgeries like standard colon resections, removal on the first day after surgery is typical. Surgeries deeper in the pelvis, such as operations on the lower rectum, carry a higher risk of temporary bladder dysfunction, so the catheter often stays in for three to six days. Anesthesia itself, especially epidural pain management, can temporarily impair your ability to urinate, which is another reason a catheter may remain in place until the epidural wears off.
Neurological Conditions
When the nerves connecting your brain to your bladder are damaged, the bladder may lose the ability to contract or to sense when it’s full. This is called neurogenic bladder, and it occurs in people with spinal cord injuries, multiple sclerosis, Parkinson’s disease, stroke, spina bifida, and some forms of dementia. The result is either an inability to urinate or uncontrolled leaking, and often both at different times.
For most people with neurogenic bladder, intermittent catheterization is preferred over leaving a catheter in permanently. This means inserting a thin tube several times a day to drain the bladder, then removing it. CDC guidelines specifically recommend this approach for spinal cord injury patients and for children with spina bifida, because it lowers the risk of urinary tract infections and long-term kidney damage compared to an indwelling catheter. Some people learn to do this themselves at home. In cases where intermittent catheterization isn’t practical, a catheter may be placed through the abdominal wall directly into the bladder for continuous drainage.
Critically Ill or Immobilized Patients
In intensive care settings, knowing exactly how much urine a patient produces each hour is one of the key ways doctors track kidney function and fluid balance. A catheter connected to a collection bag makes this possible. For patients who are too sick to get out of bed or use a bedpan reliably, continuous drainage also prevents the bladder from becoming dangerously distended.
People who must stay completely still for extended periods, such as those with unstable spinal fractures or multiple pelvic fractures, also need catheterization simply because they cannot safely get to a toilet or use a bedpan. The catheter remains in place until the patient can mobilize enough to urinate independently.
Wound Healing and Incontinence
If you have open wounds on your lower back (sacral area) or between your legs (perineal area) and you’re also incontinent, urine exposure can prevent those wounds from healing and increase infection risk. In these cases, a catheter keeps urine contained and diverted away from the skin, giving wounds a chance to close. This is one of the recognized appropriate uses in CDC guidelines. Using a catheter purely as a convenience measure for managing incontinence when no wound is present, however, is considered inappropriate.
End-of-Life Comfort
For patients in the final stages of a terminal illness, a catheter can relieve significant distress. The physical discomfort of frequent clothing and bedding changes, the psychological burden of incontinence, and pain from a full bladder that the patient can no longer empty on their own are all valid reasons for catheterization in palliative care. The goal shifts from treating an underlying condition to simply reducing suffering.
Diagnostic Purposes
Catheters are sometimes used for testing rather than treatment. Urodynamic studies, which measure how well your bladder stores and releases urine, require a catheter to monitor pressure inside the bladder. A catheter may also be used to collect a sterile urine sample when a clean-catch specimen isn’t possible, or during imaging studies like a cystogram, where contrast dye is injected directly into the bladder through a catheter so it shows up on X-rays.
Indwelling vs. Intermittent Catheters
Not all catheterization looks the same. An indwelling catheter (sometimes called a Foley catheter) stays in your bladder continuously, held in place by a small inflated balloon, and drains into a bag. This type is used for acute retention, surgery, critical illness, and situations where continuous drainage is essential. The general principle is to remove it as soon as the reason for placing it no longer applies, because infection risk increases every day it remains.
Intermittent catheterization involves inserting and removing a catheter multiple times a day, each time just long enough to empty the bladder. This approach is preferred for chronic bladder emptying problems, including neurogenic bladder from spinal cord injuries, multiple sclerosis, or spina bifida. It carries a lower infection risk than leaving a catheter in permanently and better preserves normal bladder function over time. For men without retention or obstruction who simply need help managing incontinence, an external catheter (a sheath worn over the penis) is another option that avoids entering the urinary tract entirely.
When a Catheter Is Not Appropriate
CDC guidelines are explicit about situations where catheters should not be used. A catheter should never serve as a substitute for helping someone get to the bathroom or changing incontinence products. It should not be used to collect urine for testing when a patient can urinate on their own. And it should not be left in after surgery longer than the clinical situation requires. Each unnecessary day with a catheter in place raises the chance of a urinary tract infection, which is the most common hospital-acquired infection in the United States.