UROFLOWMETRY

• Electronic recording of the urinary flow rate throughout the course of micturition.
• Simple, diagnostic screening procedure used to calculate the flow rate of urine over time.
• Common, non-invasive urodynamic test used in the diagnostic evaluation of patients presenting with symptoms of Bladder Outflow Obstruction (BOO).
• Results from the test can suggest if the flow is normal or abnormal. Abnormal results are nonspecific for the cause of the disease.
• Abnormally low flow rate may be caused by obstruction or detrusor hypocontractility.

• Flow rate – volume of urine through urethra per unit time, expressed in ml/sec.
• Peak flow rate (Q Max) – maximum measured flow rate.
• Voided volume – total volume expelled through urethra.
• Flow time – Total time over which measurable flow occurs.
• Average flow rate – voided volume / flow time.
• Time to maximum flow – elapsed time from onset of flow to maximum flow.
• Intermittent flow – flow time should be measured carefully. The time intervals between the flow episodes are disregarded.

• Possible bladder outlet obstruction / symptoms of outlet obstruction.
• Women subjected to undergo surgery for stress incontinence.
• Elderly women to exclude residual urine, a cause of recurrent UTI.
• Pre-operative workup and post-operative follow up in case of urethral stricture, Benign Prostatic Hyperplasia (BPH) bladder neck obstruction.

• A variety of normograms has been produced by various authorities, such as Von Garrelts (1958), Backman (1965), Gierup (1965), Siroky et al (1979), Kadow et al (1985) and Haylen (1990).
• The shape of the curve is unimodal i.e. monotonic increase, stable period, monotonic decrease.
• “Bell shaped”.
• Maximum flow is reached in first 30% of any trace and within 5 seconds (3-10 S) from the start of the flow.
• The flow rate may vary with amount of urine voided.
• The final phase of a normal flow trace shows a rapid fall from high flow, with a sharp cut off at the termination of the flow.
• The trace appearance may vary with paper speed. A paper speed of 25 cm/s is recommended.
• Urine flow rate is highly dependent on the volume voided.
• Flow rates are highest and more predictable with 200-400 ml urine volume.
• Detrusor muscle when stretched achieves an optimal performance, but when stretched further it becomes inefficient (> 400ml).
• Uroflow in an adult male is considered to be normal if it is bell shaped with a peak flow of 15 ml/sec or more on more than one occasion.
• Normally Uroflow in an adult female should be bell shaped with a peak flow rate of 25ml/sec

• Flow rate measurements are inaccurate if the voided volume is less than 125 to 150 ml.
• Flow rate recording is the single best noninvasive urodynamic test to detect lower urinary tract obstruction. However there is no recommended "cut-off" value.
• The peak flow rate (PFR; Qmax) more specifically identifies patients with BPH than does the average flow rate (Qave).
• Although Qmax decreases with advancing age and decreasing voided volume, no age or volume correction is currently recommended for clinical practice.
• Patients with a Qmax > 15 ml/sec appear to have somewhat poorer treatment outcomes after prostatectomy than patients with a Qmax < 15 ml/sec.
• A Qmax of less than 15 ml/sec does not differentiate between obstruction and bladder decompensation.
• Age: 4 to 7
• The average flow rate for both males and females is 10 mL/sec.
• Age: 8 to 13
• The average flow rate for males is 12 mL/sec.
• The average flow rate for females is 15 mL/sec.
• Age: 14 to 45
• The average flow rate for males is 21 mL/sec.
• The average flow rate for females is 18 mL/sec.
• Age: 46 to 65
• The average flow rate for males is 12 mL/sec.
• The average flow rate for females is 15 mL/sec.
• Age: 66 to 80
• The average flow rate for males is 9 mL/sec.
• The average flow rate for females is 10 mL/sec.
• Artifacts can occur from abdominal straining or "waggling" of the stream.

• Supra-normal pattern. Very high maximum flow rate may be achieved with an abnormally short time of 1-3 secs.
• The detrusor contraction may have already opened the bladder neck widely thus reducing the urethral resistance. Hence he/she is required only to relax the distal sphincter.

• The flow curve has low maximum flow and also reduced average flow rates, with the Qave being more than half the Qmax.
• Maximum flow may be obtained quickly (3-10S) but the final phase decreases slowly.
• The obstruction may be compressive (BPH) or constrictive (urethral stricture).

• Shows a compressive pattern, the first third of the curve may appear normal, Qmax may be reduced.
• The final phase is elongated into a pronounced “tail” of reducing flow rate.

• The later produces a “plateau” - shaped curve, with very meagre difference between Qmax and Qave.

• Produces low maximum flow rate.
• The time to reach the maximum flow is variable and usually occurs in the second half of the curve.
• The traces of both obstruction and detrusor under-activity may look similar, making it difficult to distinguish between the conditions.
• Requires urodynamic pressure flow study.