In
the present
study, we
evaluated
both Qmax
and BV in
patents
with obstructive
BPH as well
as in healthy
males. The
relation
between
Qmax and
BV was further
investigated
to determine
whether
this relation
is altered
in BPH patients,
and the
altered
relation
can account
for the
circadian
change in
urinary
flow.
MATERIALS
AND METHODS
20
patients
with bladder
outlet obstruction
secondary
to BPH were
the subjects
for this
study. The
diagnosis
of obstruction
was made
by pressure-flow
study. Mean
age of these
patients
was 70years
(range 68
to 78).
All patients
were hospitalized
for the
surgical
treatment
of BPH (TUR-P).
The study
was performed
early in
the hospital
stays before
TUR. An
uroflowmeter
(Microflow;
Life-Tech)
was used
for the
measurement
of urinary
flow. During
the first
2 days,
these patients
were asked
to void,
as they
would do
normally.
Then, they
were asked
to void
with various
BV to construct
a urinary
flow-BV
curve for
each patient.
For
the measurement
of residual
urine volume,
a BladderScan
(BVI-5000;
Diagnosis
Ultrasound)
was used
immediately
after urination.
BV was defined
as: voided
volume plus
residual
urine volume.
A total
of five
healthy
male volunteers
27 to 35
years old
(mean 29.5)
served as
normal controls.
RESULTS
Relationship
between
Qmax and
BV was adequately
fitted by
a quadratic
equation
in each
subject.
Optimal
bladder
capacity
(OBC) that
gives the
highest
Qmax was
defined
as the intersection
of the axis
of the quadratic
curve with
the volume
axis (Fig1A
and 1B).
OBC was
significantly
smaller
in patients
with BPH
than that
in healthy
males. (Table1).
The
shape of
the quadratic
curve differed
considerably
between
the two
groups.
The curves
for healthy
males had
the rather
flat top
(a near-plateau),
indicating
that Qmax
was maintained
over a wide
range of
BV (Fig.1A).
In contrast,
in BPH patients
the curve
was changed
to a typical
quadratic
curve with
the distinct
peak (Fig.1B).
Thus, Qmax
was decreased
immediately
when the
BV exceeded
the OBC.
A
circadian
change in
Qmax was
noticed
in BPH patients.
Qmax was
significantly
lower during
the midnight
to morning
period,
when compared
with the
daytime
period (Table2).
During daytime,
these patients
urinated
at the BV
near the
OBC, which
maintained
the high
Qmax (Fig.
2). However,
from midnight
to early
morning,
the BV was
consistently
observed
to be larger
than the
OBC in individual
patients,
which resulted
in a decrease
in Qmax
(Fig.2).
CONCLUSIONS
The present study demonstrates that in patients with BPH
obstruction
a typical
quadratic
relation
exists between
Qmax and
BV. Thus,
Qmax reaches
the highest
value at
OBC, which
corresponds
to a peak
of the quadratic
curve. However,
Qmax is
decreased
with a further
increase
in BV. Since
the OBC
is decreased
in BPH patients
(257ml as
mean), the
amount of
urine stored
in the bladder
seems to
frequently
exceed this
OBC. This
may occur
easily during
night because
a urine
production
increases
at night
in the elderly.
2)
Thus,
the observed
decrease
in Qmax
during the
midnight
to morning
period was
primarily
due to an
increase
in BV.
Fig.1
Correlation
between
BV and Qmax
A) healthy male
(R=0.96)
B) BPH
patient
(R=0.8)
Fig.2
Circadian
change in
BPH patient
●daytime ■midnight to morning
| |
healthy
males
|
BPH
patients
|
significance
|
| OBC(ml) |
424.5±62.0 |
257.2±75.8 |
P<0.01 |
Table.1
| |
Daytime |
midnight
to morning |
significance
|
|
BV(ml)
Qmax(ml/s)
|
231.7±70.1
11.1±4.5
|
333.4±97.8
8.2±2.1
|
P<0.01
P<0.05
|
Table.2
REFERENCES
1.Neuro.Urodyn
1999; 18:25-32
2.Am.J.Med.Sci 1997; 314(4): 232-238
