REDUCING THE INCIDENCE OF POSTOPERATIVE URINARY RETENTION BY CHANGING THE DEFINITION:  A RANDOMIZED TRIAL

Postoperative urinary retention (POUR) can be defined as *a certain maximal*
postoperative bladder volume while being unable to void spontaneously. POUR is
considered as a common postoperative complication.  Risk factors for POUR are
related to the type of operation, to the type of anaesthesia or to the patient
(age and history of voiding problems). Another factor that could influence the
risk for POUR is an unemptied bladder before the operation.  When POUR occurs,
bladder catheterization seems imminent. If bladder catheterization is delayed
until the bladder volume is well beyond its maximum capacity, bladder damage
may occur. The incidence of POUR in the recovery room is varying between 5% to
40%, depending on definition used for POUR. The incidence of POUR at the
surgical wards is unknown, because the BladderScan® is more used at the
Recovery Room than  at the ward. Thanks to the introduction of the BladderScan®
the definition for the occurrence of POUR has changed from a time limit (i.e. 6
to even 12 hours postoperatively) into a volume limit. This volume limit for
POUR is commonly, though arbitrarily, set at 500 ml. This means that when the
bladder volume exceeds the level of 500 ml - as determined by the BladderScan®
- catheterization is generally executed. This volume limit of 500 ml is
considered as a maximum bladder capacity (MBC) at which, normally, humans have
a strong urge to void. The MBC is the bladder volume that a person is able to
void spontaneously, after holding up their urine until voiding could not longer
be postponed together with the measured residual bladder volume that stays in
the bladder after complete emptying. However, there is limited knowledge about
the average MBC and it may well vary between individuals. The currently used
fixed bladder volume limit of 500 ml to define the presence of POUR and thus
the present indication for urinary catheterization, can either be too small or
too large compared to the patient*s true MBC. Therefore patients may be
catheterized unnecessarily too early, or too late. Bladder catheterization is
an unpleasant procedure for the patient involved and can lead to unnecessary
complications; such as urethral trauma or urinary tract infections. Also,
Bladder catheterization is a time consuming effort for the nursing staff. 
Preventing unnecessarily urinary catheterizations is improving the quality of
patient care.  

This study aims to investigate whether the definition of a fixed volume limit
of 500 ml can be changed to a bladder volume limit adapted to each individual*s
own maximum bladder capacity. It is expected that this change in definition
will lead to much less urinary catheterizations, which likely reduces the
incidence of complications and changes in voiding pattern due to
catheterizations postoperatively.

In this prospective randomized study two surgical patient groups will be
studied and compared. The included patients will be randomly assigned in one of
the two groups: group one (control group) will receive care as usual, i.e. POUR
is defined when, postoperatively, the patient*s bladder volume reaches the 500
ml limit and they are not able to void spontaneously, such that they are
catheterized.  In the index group, POUR presence will be defined - and
catheterization will be executed -when postoperatively the patient*s bladder
volume reaches their preoperatively measured MBC and the patient is yet unable
to void spontaneously. After Informed Consent (IC) the patient will receive an
instruction form, about how to preoperatively measure their MBC at home,
together with a measuring bowl. Patients will be asked to measure their Bladder
Capacity (BC) 3 times. The measured volumes are recorded by the patient.
PEROPERATIVELYAfter arriving at the Operation Centre (OC), the patient returns
the instruction form with the 3 measured BC written down. The RA fills in the
Case Record Form (CRF). Then randomization will take place. The patient will be
asked whether he/she went to the restroom before arriving at the OC, the time
of last voiding, and the bladder will be scanned. The anaesthesia technique and
volume infused during the per- and postoperative period is, conform routine
care, managed by the responsible anaesthesia team, who are blinded for the
group in which the patient is randomized.POSTOPERATIVELYPostoperatively the
patient will be scanned by the RA at regular intervals (every hour) until
normal voiding happens. The patient is followed after discharge from the
Recovery Room to the Surgical Ward, until spontaneous voiding or urinary
catheterization has happened. Before spontaneous voiding a Bladderscan will be
performed to register the pre-voiding volume. If a patient is not (yet) being
able to void spontaneously and the scanned volume is smaller than 500 ml (when
randomized to the control group) or than his/her personal MBC (index group),
the next scan will be performed the following hour. This procedure will be
repeated (if necessary on the wards) until the scanned bladder volume has
reached the definition for POUR (depending on the assigned intervention group)
and catheterization will be performed. Bladder catheterization will be
performed by the nursing staff according to routine care. If the patient was
operated under spinal anesthesia the level of regression of the sensory block
will be assessed by a routine test (ice cube) at the moment of spontaneous
voiding or urinary catheterization.FOLLOW UPOne day, one week and one month
after the operation, each included patient will be interviewed for any change
in voiding pattern compared to preoperatively, using the same standard
questionnaire which has also been used preoperatively (IPSS, see appendix). If
the IPSS shows a significant increase, the urologist will be consulted as in
routine care.INTERIM ANALYSISAfter 250 included patients an interim analysis
will be performed to search for patiënts at risk due to the study protocol.

The only intervention is the change in the definition for POUR for half of the
study group.

There is no associated risk other than the normal procedure.The burden for the
patient consist of measuring their bladder capity (BC = maximum voided volume)
at home. This can be done by postponing normal voiding until the urge to void
can no longer be withheld. Then normal voiding can be performed by voiding in a
calibrated bowl, making it possible te read the volume. Measuring the BC have
to performed by all patients included in the study