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3D-Printing-Assisted EADs for Preventing VUR through DJ Stents
3. Results and discussion the efficiency of EADs of various shapes, which were
inserted into the ureter after being assembled with the
3.1. Anti-reflux performance DJ stent. Figure 5B shows the urination state with reflux
Figure 5 presents an experimental setup to characterize when the stop valve was removed. It was noticed that
the anti-reflux performance of the EAD. To demonstrate the canopy membrane of the EAD was expanded by the
and compare the anti-reflux performance of each EAD, reflux pressure compared to normal EAD. This result
a voiding (urination) model, which is designed for is consistent with the simulation result (Figure 2D).
urination and reflux circumstances, was prepared using The maximum height (indicated as H max in Figure 5B)
a 3D printer, transparent polycarbonate (PC) pipes, and at which the reflux urine can rise in the ureter differs in
silicone rubber. The designed voiding model is classified response to the anti-reflex performance. Therefore, the
into three parts: 3D-printed bladder part where urine flows efficiency of anti-reflux was characterized by measuring
by urination pressure, urethra line in the bladder where the maximum reflux height (H max ) of the water along the
urine is secreted, and ureter line where the reflex occurs ureter line when pressure was applied. The lower the H max
along the inserted DJ stent. The bladder model was printed measured, the better the anti-reflux efficiency.
to have three different holes: 7-mm inner diameter for the Figure 6A shows the measured H max with respect to
urethra line, 10-mm inner diameter for the connection of the types of EADs and attached positions along the DJ
the ureter line, and 30-mm inner diameter for 50-cm long stent using a urination model. The positions are presented
PC pipe to provide the 50 cm-H O hydrostatic pressure in Figures 6B-D, and only one device was attached to the
2
and urine, as shown in Figure 5A. The bladder model and DJ stent during this experiment. Five types (without EAD
ureter line were connected using silicone rubber with a and with quadra-, penta-, hexa-, and octa-shaped EADs)
10-mm inner diameter. To mimic the bladder pressure and of a single device were evaluated 5 times with respect
urine simultaneously, hydrostatic pressure (i.e., 50 cm- to each position (Position #1, Position #2, and Position
H O) was used in this study . The PC pipe was filled #3). Accordingly, the penta-shaped EAD exhibited
[21]
2
with deionized water dyed in red color up to a length of the best anti-reflux performance at Position #1 (H max
50 cm and assembled with the bladder model. Although =220.6 mm) with a 44% decrease in the maximum reflux
water was filled in the PC pipe up to the 50-cm height to height compared to that without EAD (H max =394 mm).
represent voiding pressure, the actual initial pressure was Moreover, the penta-shaped device showed the best
48 cm-H O because some portion of the inner volume of efficiency compared to the other types of EADs at the
2
the bladder model was filled with water in this experiment. same attached position along the DJ stent, as shown in
The water flowed into the urethra and the ureter due Figure 6A. Thus, the penta-shaped EAD was beneficial
to reflux when the stop valve was removed to apply in significantly mitigating the urine reflux in this study. It
pressure on the bladder model. Using this experimental was noticed that the anti-reflux efficiency of the devices
model, in vitro experiments were conducted to determine showed the same tendency at each attached position. The
efficiency decreased in the order of penta-, octa-, hexa-
A B
A
B

C

D

Figure 5. Experimental setup to characterize the anti-reflux
efficiency. (A) Urination model with the extraluminal anti-reflux
diode (EAD) and the DJ stent before the bladder pressure was Figure 6. (A) Average values of the maximum height in the urine
applied with the zoomed-in image of normal EAD. (B) Urination reflux without and with four different types of extraluminal anti-
state after the removal of the stop valve with the zoomed-in image reflux diodes (quadra-, penta-, hexa-, and octa-shaped) with respect
of expanded EAD. Maximum height in the backflow (H max ) can be to the attached position along the DJ stent. (B) Position #1, (C)
varied in response to the anti-reflux efficiency. Position #2, and (D) Position #3.

100 International Journal of Bioprinting (2022)–Volume 8, Issue 2