Restoration of the continuity of dog ureter after resection of its 5 cm middle segment

Ureteral reconstruction using a tapered non-vascularized bladder graft: an experimental study in a canine animal model

Background

Reconstruction of ureteral defects and strictures remains problematic for urologists. We aimed to investigate the possibility of a tapered non-vascularized bladder graft as a novel substitute for ureteral reconstruction.

Methods

This experimental study was conducted on nine beagles. Under general anesthesia, a full-thickness graft with 5–6 cm in length was disassociated from the anterior upper wall of the bladder, and tapered into 1/3 to 1/2 thickness, remaining the urothelial surface. After removal of 5 cm of right-sided mid-ureter, the tapered bladder graft was tubularized along the long axis and then respectively anastomosed to the upper and lower stumps of the ureter. A retrograde urography through a cystostomy was performed 8 weeks after the ureteral reconstruction. The animals were euthanized, and histopathologic examinations of the neoureters were performed.

Results

There were no severe complications during postoperative follow-up. The urography indicated patent urine excretion and no fistula or stenosis. Histopathologic examinations of the neoureters showed open lumen with urothelial lining. Nutrient vessels were observed in healthy submucosa, lamina muscularis and peripheral connective tissue.

Conclusions

Our study implied that ureteral reconstruction by a tapered non-vascularized bladder graft was anatomically possible in our animal model. Further studies are expected to confirm long-term and functional outcomes.

Lack of usefulness of ureteral reconstruction with free bladder mucosa flap in dogs confirmed by microangiography

BACKGROUND

There is a paucity of data addressing the blood supply in the surgically reconstructed ureter, and complete lack of microangiographic studies of the reconstructed ureter with the use of a free bladder mucosa flap. The present study evaluated the blood supply in the reconstructed dog ureter after a 5-centimeter segment resection, supplemented by a tube constructed from a free bladder mucosa flap.

MATERIAL AND METHODS

Female mongrel dogs (n=29) were used in this study. Under general anaesthesia, a 5-centimeter autologous free bladder mucosa flap was used to construct a tube, which was afterwards grafted to replace a 5-centimeter ureter resection. After a period of 3 months (n=2) and after 1 year (n=2), microangiography was performed to assess the revascularization of the grafted ureter.

RESULTS

In our study, we observed the continuity of the ureter, but the grafted reconstruction was narrowed by the cicatrization in about 86% (n=25) of cases. This resulted in the development of hydronephrosis, as described in previous publications. The ureteral wall was covered by a normal urothelium, but consisted of fibrous connective tissue, which failed to restore a regular (normal) coat. The reconstructed segment showed no smooth muscle cells. A few smooth monocytes were found only at the border with intact portions of the ureter. The microangiography performed at the end of the experiments showed no vascularization of the restored segment of the ureter.

CONCLUSIONS

The experiments showed a whole regeneration of urothelium in the transected and reanastomosed ureters. However, there was no regeneration of the muscular coat and a complete lack of revascularization.

Comparison of a biodegradable ureteral stent versus the traditional double-J stent for the treatment of ureteral injury: an experimental study

Ureteral injury remains a major clinical problem; here we developed a biodegradable ureteral stent and compared its effectiveness with a double-J stent for treating ureteral injury. Eighteen dogs with injured ureters were subdivided into two groups. In group A, one injured ureter was treated with a biodegradable stent, whereas only end-to-end anastomosis was performed on the other side. In group B, one injured ureter was treated with a biodegradable stent, while a double-J stent was used on the other side. Intravenous urography, radioactive renography, histological examinations, scanning electron microscopy (SEM) and elemental composition analysis were performed at 40, 80 and 120 days postoperatively. Results showed that the biodegradable stent could effectively prevent hydronephrosis and hydroureter secondary to ureteral injury. Moreover all biodegradable stents gradually degraded and discharged completely in 120 days. SEM and elemental composition analysis of the surface of the double-J stent confirmed calcification at 80 days and calcific plaque at 120 days, while no signs of calcification were found in the biodegradable stent group. Histological studies found no difference between the biodegradable stented ureters and double-J stented ureters. It is concluded that the biodegradable ureteral stent was more advantageous than the double-J stent for treating ureteral injury in a canine model.

The use of seromuscular tapered ileal tube in ureteral replacement: an experimental model

PURPOSE

To assess the capability of urothelium to proliferate, creep and line the inner surface of the interposed seromuscular tapered ileal tube.

MATERIALS AND METHODS

Under general anesthesia, 15 female dogs underwent resection of 5 cm of the mid ureter and replaced with tapered seromuscular ileal tube stented for 6 weeks. The animals were sacrificed, and cross section of the ileal ureters were examined histologically for the lining cells.

RESULTS

Multilayer of transitional epithelium was seen covering all the inner surface of the interposed seromuscular tube at the end of 6 weeks. Excessive inflammatory cell infiltration was a prominent finding in the submucosal layer.

CONCLUSION

Transitional epithelium has the capability to proliferate, grow and cover the inner surface of the interposed seromuscular ileal tube. Urothelium lining avoid the metabolic complications of the intestinal mucosa.

Management of ureteral obstruction

The most common cause of ureteral obstruction in dogs and cats is ureteral calculi. Common clinical signs associated with ureteral obstruction include abnormalities in urination, persistent urinary tract infection, abdominal pain, vomiting, anorexia, weight loss,and depression or lethargy. Medical management of ureteral obstruction includes fluid diuresis, muscle relaxants, and treatment of azotemia using nephrostomy tubes or hemodialysis. Surgical techniques used to restore patency to the ureter include ureterotomy,partial ureterectomy and ureteroneocystostomy, and ureteral resection and anastomosis. Lithotripsy has been used in dogs to remove ureteral calculi. Renal function can be preserved if complete ureteral obstruction is relieved within several days of onset.