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 urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

when

voiding Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

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

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 part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidne ...

s, multiple sclerosis, stroke,

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

injury,

urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...

l obstruction, and

overactive bladder Overactive bladder (OAB) is a 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. If there is loss ...

, 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 (/ˈkæθətər/) 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 surgi ...

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 A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured in ...

is the volume of liquid and the

y-axis A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured i ...

is the intraluminal pressure of the bladder. In normal patients, the plot is a series of spikes whose local minimums form a non-linear 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 *Expo ...

growth curve. The spikes correspond to the bladder contractions associated with the

micturition reflex Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

. 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 (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...

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 w ...

(blood in the urine).

References

{{Urologic surgical and other procedures Urologic procedures Medical tests