The Study Of Biodegradable Ureteral Stent In Ureter Traumatic Injury

Purpose:A canine model was built up and tested so that it can be used in testing the viability and efficacy of the biodegradable stent applied to the patients after ureter traumatic injury.Materials and Methods:A hand-made device was used to make firearm fragment wounds unilaterally on ureters of 9 Beagle dogs in model build-up group. The wounds were debrided and sutured 30 minutes later.At 40 days,80 days and 120 days postoperatively intravenous pyelography(IVP) and radioactive renography were done.Then Beagle dogs were all sacrificed,after which ureters were harvested for histological test and urine specimen was obtained for culture. The viability and efficacy of the aforesaid canine model was evaluated.Firearm fragment wounds were made to the bilateral ureters in 9 Beagle dogs of Group A and in 9 Beagle dogs of Group B.For Group A,a biodegradable stent was placed unilaterally with contralateral unstented ureter debrided and sutured. For Group B,a biodegradable stent was placed unilaterally with double-J stent placed in contralateral ureter.At 40 days,80 days and 120 days postoperatively intravenous pyelography(IVP) and radioactive renography were done to both groups.Then bilateral kidneys,ureters and bladders were harvested after all the animals were sacrificed.Stents were removed for microbiological test,surface microcosmic appearance analysis and elemental analysis.The viability and efficacy of the biodegradable ureteral stent was then discussed.Results:In model build-up group,the hydronephrosis and hydroureter occurred and got worse postoperatively on the wounded side in all 9 Beagle dogs. The renal patial concertration index ratio of bilateral kidneys(unwounded side/wounded side) was found to be increasing.The half time of kidney washout ratio(unwounded side/wounded side) was found to be decreasing.Hyperplastic scar and stenosis can be observed where ureteroureterotomy had been performed.In Group A,hydronephrosis or hydroureter cound not be found postoperatively on the stented side while could be found on the unstented side in all 9 Beagle dogs.The renal patial concertration index ratio of bilateral kidneys(biodegradable stent side/unstented side) was found to be increasing while the half time of kidney washout ratio(biodegradable stent side/unstented side)was found to be decreasing.Both of the findings were of significant difference. Neither hyperplastic scar nor stenosis was found on the stented side where ureteroureterotomy had been performed;and the fibers were regular.On the unstented side,stenosis was found and fibers were irregular where ureteroureterotomy had been performed.No bacterial biofilm was formed on the biodegradable stent tube and the bacteria culture result was negative. Biodegradable stents degraded as time went on.The degradation rate became faster at 80 days postoperatively.No calcium sedimentation was found on the stent surface.In Group B,no significant hydronephrosis or hydroureter was found postoperatively on both sides.The renal patial concertration index ratio (unwounded side/wounded side) was increasing.The half time of kidney washout ratio(unwounded side/wounded side) was decreasing.But neither was of significant difference.No significant stenosis was found where ureteroureterotomy had been performed.Fibers were regular.No bacterial biofilm was found either on biodegradable stent or double-J stent.The bacteria culture result was negative.Biodegradable stents degraded as time went on.The degradation rate became faster at 80 days postoperatively.No calcium sedimentation was found on the biodegradable stent surface while on the double-J stent significant calcium sedimentation was found and thickened as time went on.Conclusion:After the firearm fragment injury was made on the ureter of Beagle dogs,hydronephrosis and hydroureter occurred at the wounded side and got worse as time went on.Compared with the situation on unwounded side,on the wounded side the renal uptake became slower and the half time of kidney washout was extended.There were stenosis and irregular fibers where ureteroureterotomy had been performed.This proved the canine model of firearm fragment wounds to be viable and effective.In Group A,based on the Beagle dog model where firearm fragment wounds were caused on both sides,the hydronephrosis and hydroureter on the stented side with biodegradable stent were prevented beforehand compared with the stentless side where hydronephrosis and hydroureter occured.The renal uptake was protected and the half time of kidney washout was shortened.This also helped to protect against stenosis where ureteroureterotomy had been performed.No bacterial biofilm was formed.Bacteria culture result was negative.The biodegradable stent,which degraded gradually,was effective for support and drainage at early stage.No calcium sedimentation was found on the stent surface.In Group B,both the biodegradable stent and double-J stent were effective for support and drainage,protecting against stenosis in ureter and hydronephrosis. In terms of impacts on the renal uptake and half time of kidney washout,no significant difference was found.No calcium sedimentation was found on either stent.The bacteria culture result was negative for both sides.The biodegradable stent,on which no calcium sedimentation was found,degraded automatically, obviating the need for a second procedure for stent removal.Whereas,the double-J stent must be removed;besides,calcium sedimentation and formation of calculus occurred on the surface and got worse as time went on.