n a recent surgery, one
I
author of this study noted
poor urine flow after kid-
ney reperfusion in a liver-
kidney transplant patient; how-
ever, after straightening the urine
drainage tubing to empty the
urine that had accumulated in
the generally U-shaped depend-
ent loop in the Foley drainage
tube, the rate of urine outflow
from the bladder appeared to
increase. This sequence of events
raised a simple question with
clinical implications: could
potentially harmful back-pres-
sures sometimes exist in urine
drainage systems that are considered as passive drains that reli-
ably channel urine from the blad-
der to the urine collection bag? At
a minimum, obstruction to urine
outflow may cause patient dis-
comfort and may also predispose
a patient to a catheter-associated
urinary tract infection (CAUTI).
Informal experimentation with a
commercial urine drainage sys-
tem led to the hypothesis that sig-
nificant back-pressures might arise in clinical practice, and con-
sequently, to the bench experi-
ments described herein.
Garcia et al. (2007) described
a cessation of drainage in urine
drainage systems with fluid-filled
dependent loops due to back-
pressure created by fluid trapped
in the loop. Dependent loops in
bladder drainage tubing signifi-
cantly increase the risk of CAUTI
(Maki & Tambyah, 2001). As a measure to avoid CAUTI, Trautner
and Darouiche (2004) and Kwak
et al. (2010) recommend ensuring
dependent drainage as appropri-
ate management of Foley
drainage systems. The urge to
void generally occurs near a blad-
der volume of 150 mL, and an
accumulating bladder volume is
associated with physical discom-
fort (Sulzbach, 2002).