Cystometry, also known as flow cystometry, is a clinical diagnostic procedure used to evaluate bladder function. Specifically, it measures contractile force of the

bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the bladder is a distens ...

when

voiding Urination is the release of urine from the bladder through the urethra in placental mammals, or through the cloaca in other vertebrates. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, ures ...

. The resulting chart generated from cystometric analysis is known as a cystometrogram (CMG), which plots intravesical pressure against the volume of fluid in the bladder.

Use

Cystometric analysis is used to evaluate the bladder's capacity to contract and expel urine. It helps determine the source of urinary problems. A normal CMG effectively rules out primary vesical dysfunction. It is used as a component for diagnosis of various disorders including

urinary tract infection A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower urinary tract infections may involve the bladder (cystitis) or urethra (urethritis) while upper urinary tract infections affect the kidney (pyel ...

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

injury,

urethra The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated ...

l obstruction, and

overactive bladder Overactive bladder (OAB) is a common condition where there is a frequent feeling of needing to urinate to a degree that it negatively affects a person's life. The frequent need to urinate may occur during the day, at night, or both. Loss of bl ...

, among others.

Procedure

The procedure is relatively short, ranging from fifteen minutes to an hour in duration. It involves the insertion of one or two

catheter In medicine, a catheter ( ) is a thin tubing (material), tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. ...

s into an emptied bladder through the urethra. In the two catheter method, one catheter transfers liquid while the other is a

manometer Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressu ...

(pressure sensor). In the single catheter method, a specialized catheter performs both functions. An additional rectal catheter may also be placed for additional data. The bladder will then be filled with saline and the patient's awareness of the event will be queried. The patient will often be asked to note when presence of liquid is felt, when the bladder feels full, and when the urgency to void is felt. The patient is then asked to void, and both flow and pressure are recorded. These are plotted against each other to create the cystometrogram.

Results

The primary results of cystometric analysis is the cystometrogram. The

x-axis In geometry, a Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of real numbers called ''coordinates'', which are the signed distances to the point from two fixed perpendicular o ...

is the volume of liquid and the

y-axis In geometry, a Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of real numbers called ''coordinates'', which are the signed distances to the point from two fixed perpendicular o ...

is the intraluminal pressure of the bladder. In normal patients, the plot is a series of spikes whose local minimums form a

non-linear In mathematics and science, a nonlinear system (or a non-linear system) is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathe ...

curve resembling an

exponential Exponential may refer to any of several mathematical topics related to exponentiation, including: * Exponential function, also: **Matrix exponential, the matrix analogue to the above *Exponential decay, decrease at a rate proportional to value * Ex ...

growth curve. The spikes correspond to the bladder contractions associated with the micturition reflex. The curve formed by the bottom of the plot reflects the level of pressure necessary to void. In normal patients, the first couple hundred

milliliter The litre (Commonwealth English, Commonwealth spelling) or liter (American English, American spelling) (SI symbols L and l, other symbol used: ℓ) is a metric units, metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic c ...

s of urine flow with minimal applied pressure. Increasing pressure is necessary to void 200 to 300 milliliters of urine. Beyond that, the pressure necessary to void additional urine rises sharply.

Risks and contraindications

As with any catheterization, the primary risk is of urinary tract infection. As a result, the procedure is contraindicated in any patient with an active UTI because the results may be skewed and the infection may spread . There is also the potential for trauma to the bladder and urethra, which may result in

hematuria Hematuria or haematuria is defined as the presence of blood or red blood cells in the urine. "Gross hematuria" occurs when urine appears red, brown, or tea-colored due to the presence of blood. Hematuria may also be subtle and only detectable with ...

(blood in the urine).

References

{{Urologic surgical and other procedures Urologic procedures Medical tests