Postvoid residual urine volume (PVR) can be measured by 2 methods: catheterization or bedside bladder ultrasonography.
The convenience, efficiency, and safety of bladder ultrasound makes its use beneficial in a wide variety of populations, including hospitalized patients, children, and the elderly.
Bladder ultrasound has been used for other procedures, such as suprapubic aspiration, evaluation of intravesical masses, and to determine bladder wall thickness and bladder wall mass.
Lower urinary tract symptoms (LUTS) may be characterized as a storage disorder, voiding disorder, or a combination of both.
Residual volumes of less than 150 mL within 10 minutes of voiding, is generally considered an acceptable amount.
It is not uncommon for abnormalities of the voiding phase to cause problems in the storage phase, such as the occurrence of bladder overactivity with bladder outlet obstruction.
The evaluation of a patient with LUTS consists of medical history, and a genitourinary examination, including a pelvic examination in women or a digital rectal examination in men.
Laboratory tests considered are urinalysis and serum creatinine measurement, to assess for urinary tract infections (UTIs) and renal function, respectively.
Additional tests include urinary cytology to screen for carcinoma in situ of the urothelium.
A prostate-specific antigen measurement, the clinician should take into account the patient’s age, life expectancy, and intent to treat.
Uroflowmetry can serve as a noninvasive screening test for selecting patients who should undergo more sophisticated urodynamic studies.
Uroflowmeters include:: weight transducers (load cells), displaced air transducers, and spinning disc flowmeters.
The load cell is the most widely used system.
Uroflowmetry measures urine voided per unit time, which is usually expressed as milliliters per second.
Flow pattern, Qmax, and volume voided generally are regarded to be the most clinically useful for both screening and following patients.
The Qmax is helpful in distinguishing those who have bladder outlet obstruction from those who do not.
Qmax rates greater than 20 mL/s indicate a low probability of bladder outlet obstruction, ; rates between 15 mL/s and 20 mL/s indicate a low probability of bladder outlet obstruction, rates between 10 mL/s and 15 mL/s are equivocal; and rates less than 10 mL/s are often the result of bladder outlet obstruction or detrusor impairment.
Typical uroflow patterns of common voiding disorders: (A) obstructive, or “breadloaf,” pattern;
(B) detrusor impairment pattern
(C) Valsalva voiding pattern; and (D) superflow pattern.
Voided volumes should be greater than 150 mL
Uroflow is partly dependent on volume voided, uroflowmetry nomograms are useful in distinguishing normal from abnormal flow rates.
The Siroky nomogram is the most widely used, but its specificity and sensitivity in diagnosing bladder outlet obstruction are 30% and 91%, respectively.
Uroflowmetry alone is insufficient to diagnose bladder outlet obstruction , because it cannot distinguish true obstruction from poor bladder contractility.
Uroflow helps to identify patients who need further urodynamic studies to diagnose an underlying problem.
Measurement of postvoid residual urine volume (PVR), the amount of residual urine in the bladder after a voluntary void, is a screening test for evaluating voiding dysfunction.
Like uroflowmetry, PVR measurement helps to identify patients in need of further evaluation and to evaluate treatment effect during follow-up.
PVR are poorly defined, but most urologists agree volumes of 50 mL to 100 mL constitute the lower threshold defining abnormal residual urine volume.
Large PVRs are associated with UTIs, especially in persons at risk, such as children or patients with spinal cord injury or diabetes.
Very large PVRs of > 300 mL, may be associated with an increased risk of upper urinary tract dilation and renal insufficiency.
High PVRs can be caused by bladder outlet obstruction , bladder hypocontractility or acontractility or, in rare cases, a large bladder diverticulum.
Bladder outlet obstruction can stem from prostatic enlargement, poor sphincter relaxation. urethral or meatal blockage, or less common causes, such as a bladder stone.
Poor bladder contractility can result from neurogenic, myogenic, psychogenic, or pharmacologic causes.
There are 2 methods of measuring PVR: sterile catheterization and bladder ultrasound.
Although sterile catheterization provides a urine sample, there are many disadvantages associated with the procedure: patient discomfort, risk of urethral trauma and UTI.
Bladder ultrasound can be performed with a portable device, is noninvasive and time-efficient, minimizes medical waste and supplies, and determines when catheterization is medically appropriate.
Assessment of PVR is helpful in pediatric patients with voiding dysfunction, spinal cord closure abnormalities, UTIs, vesicoureteral reflux, and posterior urethral valves.
Useful for patients with neurologic disease: Voiding dysfunction can result from multiple sclerosis (MS), spinal cord injury, dementia, Parkinson disease, brain injury, cerebrovascular accidents, and diabetic neuropathy.
More than 80% of patients with MS have symptoms of lower urinary tract dysfunction, and more than 96% of MS patients with disease of longer than 10-years duration have urologic findings.
Bladder ultrasound device can aid in other procedures, such as suprapubic aspiration; evaluation of intravesical masses, debris, stones, or diverticula; and evaluation of ureteral jets to rule out ureteral obstruction.
Bladder ultrasound has been used to determine bladder wall thickness and bladder wall mass and is a screening patients for bladder outlet obstruction.
Bladder wall thickness of greater than 5 mm at 150 mL is a good best cutoff point at which to diagnose bladde outlet obstruction.
Uroflowmetry-measures urine voided per unit time, can help to identify patients who have bladder outlet obstruction (BOO).
Uroflowmetry, alone, cannot definitively diagnose BOO, because it cannot distinguish true obstruction from poor bladder contractility.
Uroflowmetry allows to identify patients who need further urodynamic studies.
Postvoid residual urine volume (PVR) is useful in assessing voiding dysfunction and identifying potential bladder outlet obstruction.
Postvoid residual urine volume measurement can be performed by sterile catheterization or by bladder ultrasound.
Portable bladder scanners are noninvasive, accurate, cost-effective, and carry no risk of urethral trauma or urinary tract infection.
Bladder ultrasound device can aid in suprapubic aspiration; evaluation of intravesical masses, debris, stones, or diverticula; and evaluation of ureteral jets to rule out ureteral obstruction.
Can be used to determine bladder wall thickness and bladder wall mass, both of which have been associated with outflow obstruction.
Urinanalysis with or without urine culture should be performed on all patients with incontinence to rule out UTI or microscopic hematuria.