Introduction:
The lower urinary tract of the human body consists of the urinary bladder and urethra. These organs help in the storage of urine and provide voluntary control during urination. Abnormalities in these organs lead to abnormal urinary flow. That is why functional assessment of the lower urinary tract is important.
What Are Urodynamic Studies?
The first definition of urodynamic studies was put forward in the year of 1988. It is nothing but the functional assessment of the lower urinary tract. Urodynamic studies assess the efficiency of the urinary bladder and urethra. In these measurements, the filling and voiding parameters are evaluated.
What Are the Indications of Urodynamic Studies?
As discussed, urodynamic studies help to determine the abnormality in the process of urination. These abnormalities lead to sudden leakage of urine. This is known as urinary incontinence. Different types of urinary inconsistency are seen based on several situations and pathological conditions. The causative factors for urinary incontinence are:
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Stress Urinary Incontinence: This type of urinary inconsistency occurs due to a sudden increase in intra-abdominal pressure. Such things usually occur during coughing, sneezing, and exertion. This is also seen in sports persons during sports activity or in pregnant women. Persons can predict the leakage of urine. Urethral sphincter or pelvic floor weakness is the root cause of this type of urinary incontinence.
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Urge Urinary Incontinence: This type of urinary leakage is related to urinary urgency. Bladder dysfunctions are the root cause of this type of urinary incontinence. Increased bladder activity, bladder hypersensitivity, and poor detrusor compliance are responsible for such situations. Such type of incontinence is seen in elderly people.
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Mixed Urinary Incontinence: This type of urinary inconstancy occurs due to stress and urgency.
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Overflow Urinary Incontinence: This type of urinary inconsistency occurs due to an over-distended bladder or due to chronic urinary retention. Overproduction of urine in diseases like diabetes is one of the main reasons for this type of urinary incontinence. Over-distension of the bladder is another reason behind it. Bladder outlet obstruction is responsible for over-distension of the bladder. Such type of bladder outlet obstruction happens due to pathological factors like Skene's gland cyst (cyst in the Skene's gland which is located at the lower end of the urethra), presence of the Mullerian duct remnants, urethral diverticulum (presence of unwanted sac in the urethra), and ectopic ureterocele (presence of extra tube in the urinary system). Cervical carcinoma, vaginal cancer, and urethral carcinoma are also associated with bladder obstruction. One of the most common causes of this urinary incontinence is benign prostatic hyperplasia in males (overgrowth of prostate tissues) and pelvic prolapse (abnormal position of pelvic organs) in females.
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Functional Urinary Incontinence: Environmental factors or physical barriers to toileting are responsible for this type of urinary inconsistency. In such cases, the urinary tract functions normally, but physical or cognitive impairment causes urine leakage. Functional conditions like dysfunctional voiding and external sphincter pseudo dyssynergia (unusual sphincter contraction during voiding) are also related. Neurological disorders like spinal cord injury, multiple sclerosis (a disorder in which the brain and spinal cord is destroyed by the immune system), degenerative changes in the pelvic floor muscles, and Parkinson's disease(a type of nerve disorder) may also cause bladder obstruction.
What Are the Components of Urodynamic Studies?
The component of the urodynamic studies is the following tests:
1. Uroflowmetry:
Urinary flowmetry is one of the first lines of test for obtaining objective and quantitative information. It is a simple, non-invasive, and inexpensive test. In this test, the patients sit on a commode and pass urine without straining over a rotating disc flow meter or weight-transducer flowmeter. The volume of urine passed per unit of time can be assessed in milliliters per second. Also, the measurement of total volume voided and maximum flow rate is evaluated. The post-residual volume of urine can be evaluated through ultrasound measurements or using a catheter.
In ideal cases, it forms a bell-shaped graph. The parts of the bell-shaped curve are a rapid upstroke at the beginning, a curve with continuous flow, a clear maximum flow rate or Qmax, and a quick decline at the end. The normal maximum flow rate of urine is 20 to 36 milliliters per second. Non-pathological factors like low urinary volume (less than 150 millimeters) and overfilling of the urinary bladder (more than 550 millimeters) are associated with alteration in the maximal flow rate. Suprapubic tapping of the urinary graph is caused by neurological complications that lead to poor contraction of the urinary bladder.
2. Cystometry:
The bladder storage ability is determined by this test. This test determines pressure within the bladder or intravesical pressure. The normal pressure within the bladder should be 5 to 50 centimeters of water. Single-lumen or double-lumen catheter helps to fill up the bladder artificially and continuously for measuring intravesical pressure. Fluid-filled open or punctured balloon catheters, which are inserted through the rectal and vaginal route, determine abdominal pressure. Subtraction of the abdominal pressure from the intravesical pressure helps to determine the detrusor muscle pressure. The competence of the urinary bladder sphincter muscle is also determined by this test. In normal conditions, the detrusor pressure remains the same throughout the filling period and even after provocations. Raised abdominal pressure after provocation causes leakage of urine in cases of stress incontinence. Involuntary contraction of detrusor muscles during filling phases suggests detrusor overactivity.
3. Pressure Flow Study:
After finishing the cystometric test, this test is done. This test measures the required pressure for urination and its association with the quick flow of urine. A manometer is used for this purpose. Poor pressure flow result denotes impaired detrusor contractility or outflow obstruction.
4. Video Cystometry:
Radiographic or ultrasound imaging of the lower urinary tract is done with the help of an iodine-based contrast medium. It helps to determine the urethral length and its competence. This test can identify vesicoureteral reflux (reverse flow of urine) during filling. Conditions like neurogenic bladder, urethral diverticula (presence of sac in the urethra), and urethral duplication (presence of accessory urethra) can be diagnosed through this process.
5. Pad Test:
This test is helpful in determining the occurrence of urinary incontinence. For short-term tests, the patient wears a pre-weighted pad for one hour. After performing physical activity, the weight of the pad is measured. A weight gain of more than 1 gram signifies a positive result and leakage of urine. For long-term tests, patients wear this for 24 to 48 hours. Pad is changed after every four to six hours, and measurement of weight is done. Weight gain of more than 1.3 grams signifies a positive result.
Conclusion:
The lower urinary tract provides the functional ability to control urination. The pathological condition leads to abnormal leakage of urine. Several pathological conditions like hyperactive bladder, detrusor overactivity, and neurogenic bladder are associated with this. Such conditions can be identified with the help of urodynamic studies.
