What Is a Cystometric Study?

A cystometric study is done to determine the size of your bladder and how well it functions. Cystometric studies are also called cystometrograms or CMGs. The procedure measures how much fluid your bladder can hold, how full it is when you begin to feel the need to urinate, and the pressure of your urinary flow.

Your doctor may want you to have this procedure if you have trouble completely emptying or controlling your bladder.

Bladder dysfunction can have a significant impact on your quality of life. Cystometric studies help to measure bladder capacity and function. This can help your doctor identify specific problems and recommend treatments that will improve your ability to carry on with normal daily activities.

Bladder problems, including overactive bladder, reduced bladder capacity, and incomplete emptying, or an inability to empty the bladder completely, can occur with pregnancy. They can also occur with a variety of conditions, such as:

  • a urinary tract infection (UTI)
  • a spinal cord injury
  • bacterial prostatitis
  • an enlarged prostate, such as from benign prostatic hyperplasia
  • a neurological disease, such as multiple sclerosis
  • a stroke

Your doctor may prescribe antibiotics before or after the procedure to help prevent infection. The exact procedure for your cystometric study will vary slightly based on the doctor, the facility, and your medical condition. Your doctor will provide you with details specific to your procedure.

You can have a cystometric study in your doctor’s office, an outpatient clinic, or a hospital. General anesthesia isn’t necessary. You shouldn’t have a cystometric study if you have an active UTI because this procedure may cause your infection to spread to the bladder.

Your doctor may ask you to empty your bladder so that the technician can record the following measurements:

  • how long it takes you to start urinating
  • the size and strength of your urine stream
  • how long it takes to empty your bladder
  • the amount of urine you produce

They will record any difficulties or abnormalities you experience.

The following steps will take place while you’re lying on your back on a bed or examination table.

  1. Your doctor will clean the skin around your urethra and give you local anesthesia.
  2. Your doctor will then insert a thin tube called a “catheter” into your urethra and up into your bladder. This sometimes causes a slight burning sensation. The catheter will measure how much urine is still in your bladder.
  3. They will then insert a second catheter into your rectum, with electrodes placed in the surrounding area. A tube attached to the catheter called a “cystometer” measures the pressure.
  4. Your doctor will fill your bladder with a saline solution and water. They’ll ask if you feel any of the following:
  • fullness
  • pressure
  • pain
  • an urge to urinate
  1. You may also feel the sensation of coolness or warmth from the liquid. It’s possible that your bladder may leak a little during the procedure. This is normal.
  2. As your bladder fills, your doctor will ask you to report when you begin to feel an urge to urinate.
  3. After your bladder is full, you’ll urinate. Your doctor will record the pressure of your urine stream.
  4. They’ll then drain any fluid still in your bladder and remove the catheters.

The entire procedure will take about 20 to 30 minutes to complete if there are no complications.

During the Procedure

Depending on your medical condition, you may experience some pain during the procedure. Most people report that inserting the catheter and filling the bladder causes some discomfort. Other potential side effects include:

  • an urgent need to urinate
  • nausea
  • sweating
  • flushing

For people who have a high spinal cord injury, there’s a risk of autonomic dysreflexia. This is an abnormal response to the pressure of a full bladder. Tell your doctor immediately if you begin to have some of these symptoms during the test:

  • sweating
  • feeling flushed
  • a headache
  • high blood pressure

This is a dangerous condition that can cause a seizure, stroke, or even death.

After the Procedure

You may have some discomfort during urination for a few days, and your urine might contain small amounts of blood. Some people also report getting UTIs. If you have any of the following symptoms, you should contact your doctor immediately:

  • a fever
  • chills
  • excessive bleeding
  • increasing pain

These symptoms may indicate that you have an infection.