This document describes uroflowmetry - a noninvasive test used to evaluate urine flow. It discusses the normal and abnormal flow patterns seen in uroflowmetry and their clinical significance. Uroflowmetry provides parameters like maximum flow rate, average flow rate and voided volume. It can detect bladder outlet obstruction, detrusor underactivity or overactivity. However, pressure-flow studies are needed to precisely define lower urinary tract function. Uroflowmetry is useful for screening and monitoring treatment response, though invasive therapy should not be based on uroflowmetry alone per AUA guidelines.

1. Uroflowmetry
Dept of Urology
Govt Royapettah Hospital and Kilpauk Medical College
Chennai

2. Moderators:
Professors:
➢ Prof. Dr. G. Sivasankar, M.S., M.Ch.,
➢ Prof. Dr. A. Senthilvel, M.S., M.Ch.,
Asst Professors:
➢ Dr. J. Sivabalan, M.S., M.Ch.,
➢ Dr. R. Bhargavi, M.S., M.Ch.,
➢ Dr. S. Raju, M.S., M.Ch.,
➢ Dr. K. Muthurathinam, M.S., M.Ch.,
➢ Dr. D. Tamilselvan, M.S., M.Ch.,
➢ Dr. K. Senthilkumar, M.S., M.Ch.
Dept of Urology, GRH and KMC,
Chennai. 2

3. ➢ Urine flow studies are the simplest of
urodynamic techniques – noninvasive
➢ Equipment is simple and relatively
inexpensive
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Dept of Urology, GRH and KMC,
Chennai.

4. Definitions
➢ Urine flow - described in terms of flow rate
and flow pattern (continuous or
intermittent)
➢ Flow rate - volume of fluid expelled via the
urethra per unit time and is expressed
in ml/s
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Dept of Urology, GRH and KMC,
Chennai.

5. ➢ Maximum flow rate (Qmax) - Maximum measured value
of the flow rate
➢ Voided volume (VV) - Total volume expelled via the
urethra
➢ Flow time - Time over which measurable flow occurs
➢ Average flow rate (Qave) - Voided volume divided by
flow time
➢ Time to maximum flow - Elapsed time from onset of flow
to maximum flow
➢ Voiding time - total duration of micturition, including the
interruptions
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Dept of Urology, GRH and KMC,
Chennai.

6. Intermittent flow - same measurements
are used as for continuous flow curve
➢ However, flow time must be measured
carefully, as the time intervals between
flow episodes are disregarded
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Dept of Urology, GRH and KMC,
Chennai.

7. NORMAL CURVE
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Dept of Urology, GRH and KMC,
Chennai.

8. INTERMITTENT PATTERN
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Dept of Urology, GRH and KMC,
Chennai.

9. Equipment
➢ Weight Transducer Flowmeter
➢ Rotating Disc Flowmeter
➢ Capacitance Flowmeter
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Dept of Urology, GRH and KMC,
Chennai.

10. Weight transducer flowmeter involves
weighing the urine voided
➢ Calculates the urine flow rate by
differentiation with respect to time
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Dept of Urology, GRH and KMC,
Chennai.

11. Rotating-disc flow meter
➢ Spinning disc on which the urine falls
➢ The disc is kept rotating at the same speed by a
servomotor, in spite of changes in the urine flow rate
(weight of the urine tends to slow the rotation of the disc)
➢ The differing power needed to keep disc rotation
constant is proportional to the urine flow rate
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Dept of Urology, GRH and KMC,
Chennai.

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Dept of Urology, GRH and KMC,
Chennai.

13. Normal Flow Patterns
➢ When considering the normal flow rates
⚫ Age and Sex
⚫ Voided volume
should be taken into account
➢ In addition to numerical data , shape of
the trace - important
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Dept of Urology, GRH and KMC,
Chennai.

14. Normal flow
➢ “Bell” shape
➢ Maximum flow is reached in the first 30% of any trace
and within 5 seconds from the start of flow
➢ Flow rate varies according to the volume voided
➢ The final phase of a normal flow trace shows a rapid fall
from high flow, sharp cutoff at the termination of flow
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Dept of Urology, GRH and KMC,
Chennai.

15. ➢ Urine flow rate is highly dependent on the volume voided
➢ Detrusor muscle when stretched achieves an optimal
performance, but if stretched further it becomes
inefficient
➢ At more than 400 ml, the efficiency of the detrusor
begins to decrease and Qmax is lower
➢ Flow rates are highest and most predictable in the
volume range between 200 ml and 400 ml
➢ Minimum voided volume of 150 ml is necessary for
accurate assesment
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Dept of Urology, GRH and KMC,
Chennai.

16. Qmax Vs Voided Volume
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Dept of Urology, GRH and KMC,
Chennai.

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Dept of Urology, GRH and KMC,
Chennai.

18. Flow rate nomograms
➢ nomograms have been developed to
define normal flow rates for a specified
population and correct flow rate for voided
volume
1.Siroky nomogram for men
2.Liverpool nomogram for men and women
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Dept of Urology, GRH and KMC,
Chennai.

19. Abnormal Flow Patterns
➢ Urine flow results from the interaction
between the detrusor contraction /
abdominal straining and urethral
resistance
➢ urine flow rates have limitations
which must be appreciated
19
Dept of Urology, GRH and KMC,
Chennai.

20. ➢ Information from urine flow traces, without simultaneous
pressure recording must be interpreted with care
Misleading situations
➢ Patients showing normal flow can have bladder outlet
obstruction when a normal Q max is maintained by
abnormally high voiding pressures
➢ Patients whose low flow rates are due to detrusor
underactivity rather than to bladder outlet obstruction
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Dept of Urology, GRH and KMC,
Chennai.

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Dept of Urology, GRH and KMC,
Chennai.

22. Bladder Outlet Obstruction (BOO)
➢ Low Qmax and reduced average flow, with the
average flow greater than half the Qmax
➢ Qmax- obtained quickly (3–10 secs), but the flow
rate then decreases slowly
➢ Terminal dribble
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Dept of Urology, GRH and KMC,
Chennai.

23. ➢ Obstruction may be
⚫ Compressive - Benign Prostatic Obstruction
⚫ Constrictive - Urethral Stricture
➢ Constrictive obstruction - “plateau”-shaped trace with
little change in flow rate and little difference between
Qmax and Qave
➢ Compressive obstruction - first third of the flow trace
may appear relatively normal, Qmax will be reduced,
latter part is elongated into a pronounced “tail” of
reducing flow rate
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Dept of Urology, GRH and KMC,
Chennai.

24. URETHRAL STRICTURE
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Dept of Urology, GRH and KMC,
Chennai.

25. BENIGN PROSTATIC OBSTRUCTION
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Dept of Urology, GRH and KMC,
Chennai.

26. Detrusor Underactivity (DUA)
➢ Symmetrical trace with a low maximum flow
rate is seen
➢ Time to reach Qmax is variable , may occur in the
second half of the trace
➢ Considerable overlap between - obstructed and
underactive detrusor group – proof comes from a
pressure-flow study
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Dept of Urology, GRH and KMC,
Chennai.

27. DETRUSOR UNDERACTIVITY
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Dept of Urology, GRH and KMC,
Chennai.

28. Detrusor Overactivity
➢ Very high maximum flow rates in abnormally short time
(1 s - 3 s)
➢ Reduction in time to Qmax is achieved because the
detrusor contraction has already opened the bladder
neck widely, hence reducing the urethral resistance.
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Dept of Urology, GRH and KMC,
Chennai.

29. DETRUSOR OVERACTIVITY
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Dept of Urology, GRH and KMC,
Chennai.

30. Interrupted Flow Patterns
➢ Irregular Trace
Secondary to
Straining
⚫ Habitual
⚫ Obstruction
⚫ Detrussor over activity
⚫ Urethral overactivity
⚫ Artefacts
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Dept of Urology, GRH and KMC,
Chennai.

31. Artefacts
“Cruising”
➢ Caused by men moving their stream in relation to the
central exit from the collecting funnel
➢ “Peaks” occur when the point of impact of the stream is
moving down the side of the funnel towards the central
exit
➢ “Valleys” occur when the impact point is moving
away from the exit
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Dept of Urology, GRH and KMC,
Chennai.

32. CRUISE ARTEFACT
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Dept of Urology, GRH and KMC,
Chennai.

33. “Squeezing”
➢ In an effort to deny the onset of age (and reducing urine
flow), some men have the habit of squeezing the tip of
their penis or foreskin during voiding
➢ This leads to a series of peaks
➢ When the patient is asked to stop this , the flow trace
usually becomes classically obstructed, and the flow rate
is no longer within the normal range
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Dept of Urology, GRH and KMC,
Chennai.

34. SQUEEZE ARTIFACT
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Dept of Urology, GRH and KMC,
Chennai.

35. Indications
➢ Urine flow studies are an excellent screening study in a
wide variety of patients
➢ But they must be followed by pressure-flow studies -
precise definition of bladder and urethral function
➢ Uroflow is used to investigate possible bladder
outlet obstruction and can also give a guide to detrusor
contractility
➢ It can be used for patients of all ages and both sexes
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Dept of Urology, GRH and KMC,
Chennai.

36. Indications
➢ Uroflow is the screening test of choice in men of
all ages with symptoms suggestive of outlet
obstruction
➢ Uroflow should be measured before and after
any procedure designed to modify the function
of the outflow tract
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Dept of Urology, GRH and KMC,
Chennai.

37. QMAX
➢ Qmax is below 10 ml/s then the chance of the
patient having BOO is 90%
➢ If the Qmax is 10 ml/s to 15 ml/s then the
incidence of BOO is 71% or less
➢ Because 29% of these patients will not have
BOO, patients with a Qmax of 10 ml/s or more
should have PRESSURE FLOW STUDIES
before invasive therapy
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Dept of Urology, GRH and KMC,
Chennai.

38. 38
Dept of Urology, GRH and KMC,
Chennai.

39. AUA Guidelines
➢ Urinary flow rate measurement is optional
➢ It is useful in the initial diagnostic assessment and during
or after treatment to confirm response
➢ Despite the noninvasive nature of the test and its clinical
value, it is an optional test before embarking on any
invasive therapy
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Dept of Urology, GRH and KMC,
Chennai.

40. AUA Guidelines
➢ Peak urinary flow (Qmax) is the best single measure to
estimate the probability of a patient to be urodynamically
obstructed
➢ But a low Qmax does not distinguish between
obstruction and decreased detrusor contractility
➢ Because of the intra‐individual variability and the volume
dependency of the Qmax, at least 2 flow rates should be
obtained, ideally both with a volume greater than 150 mL
voided urine.
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Dept of Urology, GRH and KMC,
Chennai.

41. THANK U
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Dept of Urology, GRH and KMC,
Chennai.

42. ICS NOMOGRAM
BOOI = PdetQmax
− 2(Qmax)
Men are considered
obstructed if BOOI is
greater than
40, unobstructed if
BOO is less than 20,
and equivocal if
BOOI is 20 to 40.
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Dept of Urology, GRH and KMC,
Chennai.

43. BCI NOMOGRAM
the bladder contractility index (BCI), is
➢ given by the formula: PdetQmax + 5(Qmax)
➢ Strong contractility is a BCI greater than 150
➢ Normal contractility a BCI of 100 to 150
➢ weak contractility a BCI of less than 100
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Dept of Urology, GRH and KMC,
Chennai.