Experimental rectus abdominis myocutaneous and rectus abdominis myoperitoneal flaps as urinary bladder wall substitutes in miniature swine

Ureteral reconstruction with abdominal wall muscle flap: experimental study in rabbits

The authors detail the experimental development of a technique for the reconstruction of the ureter using a tubular shape, muscle flap of the abdominal wall. the preliminary results indicate the feasibility of this surgical technique.

Closure and augmentation of bladder exstrophy using rectus abdominis musculo-peritoneal flap

Background:

The aim of this study was to investigate the efficacy of the rectus abdominis myo-peritoneal flap (RAMP) technique for the closure and augmentation of small, non-elastic, non-compliant bladder exstrophies.

Materials and Methods:

The RAMP technique was used in three boys with bladder exstrophy who presented late with small, non-elastic, non-compliant bladder. The clinical outcome, imaging, cystoscopy, biochemical and microbiological studies were assessed during a follow-up of 36 months.

Results:

Bladder closure and augmentation was achieved in all patients without any complications. There were no urinary tract infections, metabolic problems or electrolyte disturbances and the kidney function remained normal in all patients. Radiography confirmed intact function and anatomy of the urinary tract and cystoscopy showed complete coverage of the inner peritoneal layer of RAMP with uroepithelium. No stone formation or mucous production was detected.

Conclusions:

The RAMP technique is a good alternative for closing bladder exstrophies and achieves an increase in bladder capacity and compliance. The technique is indicated in the closure of large bladder defects, bladder exstrophies with small, inelastic, non-compliant bladder remnants and failed primary closures.

Urinary bladder wall substitution using autologous tunica vaginalis in male dogs

Fresh autologous tunica vaginalis was experimentally used for partial substitution of the excised urinary bladder wall in ten male mongrel dogs. The substituted areas of two dogs were examined macroscopically and histologically at 2, 4, 6, 8, and 10 weeks after surgery. Two control dogs underwent partial cystectomy and primary wall closure without substitution. The regenerated transitional epithelium completely covered the substituted portion and smooth muscle regeneration was present at 6 weeks. The bladder walls at the closure area of one control dog and at the substituted portions of two dogs at 10 weeks were indistinguishable macroscopically from the native bladder with all layers of the bladder wall present histologically. According to the macroscopic and histological findings and simplicity of the technique, tunica vaginalis can be used as an alternative graft for bladder wall substitution. Calcification and bone metaplasia observed were similar to those found after using other tissue grafts.

One-stage posttraumatic bladder reconstruction and soft-tissue coverage of the lower abdomen or perineum

Mutilating injury on pelvis may be complicated by urinary bladder ruptures and soft-tissue avulsion of the lower abdominal wall or perineum. With retraction of the avulsed abdominal wall or perineum, as well as bladder tissue loss secondary to trauma or infection, direct closure the injured bladder often leads to excessive tension, resulting in ischemia and eventual failure of repair. The authors successfully managed 4 patients with such injuries using the pedicled vastus lateralis myocutaneous flap. No major complications occurred and intact bladders were confirmed with cystograms. Three (75%) of them were able to void normally within 1 year. It is concluded that the pedicled vastus lateralis myocutaneous flap is an ideal option for posttraumatic bladder reconstruction and soft-tissue coverage of the lower abdomen or perineum; whereas the undersurface of the muscle serves as a substitute for the missing bladder wall, the remaining part of the muscle, as well as the subcutaneous fat, provide sufficient bulk for dead space obliteration.

Use of abdominal wall with mesothelium as a substrate for reconstitution of urinary bladder wall: Replacement of the mesothelium by the urothelium and complete bladder wall reconstruction

OBJECTIVE

The urinary bladder has considerable regenerative ability and may enable reconstitution of the urinary bladder if used appropriately.

MATERIAL AND METHODS

Rat urinary bladders were allotransplanted onto the inner surface of the abdominal wall with the urothelium facing the mesothelial cells. The ureters, urethra and blood supply were left intact.

RESULTS

A week after the operation, the mesothelium of the abdominal wall was replaced by the urothelium from the donor urinary bladder and a cyst was formed, the inner surfaces of which were completely covered with the urothelium. After a few months, the submucosal tissue and muscular layer had also moved to cover the wall, forming an almost complete urinary bladder. The mucosal membrane formed complex folds, which was probably due to overgrowth of the epithelial cells and the submucosal connective tissues. The area derived from the abdominal wall showed only minimal shrinkage, whereas the abdominal wall from which the mesothelium had been removed showed significant shrinkage.

CONCLUSION

This method is potentially useful for the reconstruction of urinary bladders.

THE TUNICA VAGINALIS DORSAL GRAFT URETHROPLASTY: EXPERIMENTAL STUDY IN RABBITS

PURPOSE

We created an experimental model of urethral defect and then repaired it using a tunica vaginalis graft applied on the dorsal surface of the urethra. We studied the histological and radiological characteristics of free tunica vaginalis graft urethroplasty.

MATERIALS AND METHODS

In 20 New Zealand rabbits a dorsal urethral defect was created by excising a portion of the dorsal urethral surface. The tunica vaginalis graft was placed dorsally over the corpora cavernosa and tied with 4 interrupted sutures. The mucosal margin of the urethral defect was sutured to the graft using 6-zero polydioxanone sutures in continuous fashion. The animals were divided into 4 equal groups and were sacrificed 14 days, and 4, 8 and 12 weeks after surgery, respectively. A retrograde urethrogram was done at autopsy. The penis was sent for histological analysis and an experienced pathologist evaluated the severity of acute and chronic inflammation, foreign body reaction and scar formation.

RESULTS

There were no deaths related to the procedure and no intraoperative complications. All rabbits voided spontaneously after surgery. Retrograde urethrograms showed no fistula or stricture. As time after surgery increased, the signs of inflammation response disappeared, and the orientation of collagen fibrils and smooth muscle fascicles resembled that of a normal urethra. The mesothelial lining of the tunica vaginalis gradually became replaced by a more stratified epithelial lining, similar to the urothelial lining of the native urethra.

CONCLUSIONS

In the current study we noted that a tunica vaginalis graft placed dorsally can be a successful urethral substitute in the animal model.

The rectus abdominis musculoperitoneal (RAMP) flap for the reconstruction of complicated pharyngoesophageal defects

In the advanced stage of hypopharyngeal cancer, extensive resection may sometimes leave both the cervical soft tissue and pharyngoesophageal defects that must be reconstructed at the same time. In this study, a new reconstructive method using the rectus abdominis musculoperitoneal flap is described. Three patients underwent pharyngoesophageal reconstruction by this method. Complete survival of the flaps was seen in all patients, but one patient developed a fistula due to rapid local recurrence of the tumour. We believe that the rectus abdominis musculoperitoneal flap can be an alternative choice for reconstruction of pharyngoesophageal defect, especially when there is a large area of cervical soft tissue defect at the same time.

Vaginal Reconstruction With a Rectus Abdominis Musculoperitoneal Flap

In more than 300 clinical cases, the authors have observed and documented the presence of a branch of the deep inferior epigastric artery that penetrates the posterior rectus sheath near the umbilicus. Their cadaveric anatomic and animal injection studies confirm the vascularity of the peritoneum via the deep inferior epigastric artery. They report 2 patients treated with a new technique of vaginal reconstruction using a thin, pliable flap with a peritoneal-lined rectus abdominis muscle based on the deep inferior epigastric vessels.

Free peritoneal grafts for patch urethroplasty in male rabbits

PURPOSE

We evaluated the feasibility of urethroplasty using a free peritoneal graft in a rabbit model.

MATERIALS AND METHODS

In 12 male rabbits a urethral defect was created by excising a 3 x 5 mm. portion of the ventral urethral surface. The defect was immediately repaired with a free peritoneal graft harvested via a left flank incision.

RESULTS

There were 2 intraoperative deaths and 1 death on day 8 postoperatively. These animals were excluded from study. The remaining 1, 4 and 4 rabbits were sacrificed 3, 5 and 9 weeks after surgery, respectively. Macroscopic examination of the urethra revealed no stenosis or diverticula, while a fistula was present in 3 of the 9 animals. Histological study of the fistulous tracts showed chronic granulomatous inflammation. In the remaining 6 rabbits there was graft adherence. The inner surface of the graft was uniformly lined with normal urothelium, while in some cases acute inflammatory cells were present in the subepithelial layer.

CONCLUSIONS

Our experience indicates that the ease of harvesting free peritoneal grafts and their satisfactory adherence to the urethra makes them a valid alternative for repairing urethral defects.

Surgically induced urologic models in swine

The porcine urological system is similar anatomically and physiologically to that of humans. Swine have a true multirenculate, multipapillate kidney with a calyceal system like that of humans. The gross anatomic and histologic characteristics of the porcine and the human kidney are more similar than most other commonly used laboratory animals. The physiologic functions of the urinary system including urodynamic parameters are also similar to humans. Swine have been used extensively as models of urologic conditions in humans, most commonly in obstructive urologic syndromes. A large number of investigative procedures can be performed in one experiment both in acute and chronic models. Recently, a new technique of surgically induced antenatal lower urinary tract obstruction in swine has been developed.

Functional urinary bladder wall substitute using a free innervated latissimus dorsi muscle flap

This study was designed to investigate the ability of the latissimus dorsi muscle in situ to evacuate a bladder reservoir and to study the functional, anatomic, and histopathologic results of partial or subtotal bladder reconstruction with an innervated free latissimus dorsi muscle in mongrel dogs. In group I (four dogs), the latissimus dorsi muscle was dissected and tailored in situ. Then the so-formed pedicled latissimus dorsi muscle flap was wrapped around tissue expanders of varying sizes (volumes of 50, 100, and 150 cc, respectively) to form a bladder-like reservoir. Electromyography and intraluminal pressure measurements were done at the time of surgery and 6 months thereafter using a standard electromyograph and a Dantec urodynamic unit. In group II (four dogs), the dome of the bladder wall was removed, with up to 50 percent of the mucosal layer being left intact. The resulting muscular defect was repaired with a free innervated latissimus dorsi muscle flap. The transferred latissimus dorsi muscle was shaped and wrapped around the bladder in a spiral form, with particular attention to the resting tension. The thoracodorsal vessels were anastomosed to the pelvic branches of the hypogastric vessels, and the thoracodorsal nerve was coapted to a pelvic motor nerve that was selected by use of a nerve stimulator. Cystography and urodynamic studies were performed after 3, 6, and 9 months. Electromyography was done after 9 months, before sacrifice of the animals, which was followed by regular histologic and electron microscopic examinations. Stimulation of the thoracodorsal nerve of the reconfigured latissimus dorsi muscle reservoirs in situ after 6 months yielded average intraluminal pressures of 190 cmH2O at maximum capacity and 35 cmH2O at a minimum capacity of 10 to 15 cc. Stimulation of the latissimus dorsi muscle transferred to the bladder resulted in a visible and measurable contraction of the transplanted muscle after 9 months. Urodynamic values preoperatively and postoperatively were basically unchanged. During cystography, the bladder outline was smooth during both filling and voiding. Light and electron microscopic examinations confirmed viable, reinnervated muscle. The reconfigured pedicled latissimus dorsi muscle has the ability to evacuate a bladder-like reservoir after nerve stimulation. A detrusor function of the bladder can be induced through the contractility of a reinnervated free latissimus dorsi muscle that was wrapped around the bladder. An innervated free latissimus dorsi muscle flap does not undergo severe muscle fibrosis, contracture, and atrophy such as occur after transfer of completely or partially denervated, pedicled muscle. This means that a functional bladder reconstruction/augmentation can be achieved by microneurovascular transfer of a latissimus dorsi muscle flap.

Use of tubularized peritoneal free grafts as urethral substitutes in the rabbit

As an alternative to bladder mucosa, free grafts of tubularized peritoneum were used as urethral substitutes in a rabbit model of hypospadias. In group 1, six mature rabbits underwent partial penile urethrectomy followed by interposition of a 2-cm-long peritoneal-lined tube graft. These animals had urethrograms performed at 3 months and were killed at 6 (n = 4) or 12 (n = 2) months. In group 2, six rabbits underwent total penile urethrectomy with placement of 3-cm-long grafts. These animals were killed 1 to 4 weeks after surgery. Clinical assessment and gross examination of the 12 rabbits showed no urinary retention, two small fistulas at the proximal anastomosis, and no strictures or diverticular. At 6 and 12 months (group 1) the urethra had healed completely and the graft edges were not visible. In group 2, 1 to 4 weeks after surgery the graft was intact and the interface between the graft and native urethra was visible. Histological studies of the grafts were compared with control peritoneum. At 1 week, a high-density single-cell layer was present. Beginning at 2 weeks, a multilayered epithelium was present, which became more organized in the older grafts. Neovascularity became visible in the subepithelial layer at 2 weeks. Acute inflammatory cells were present early and were replaced by a palisading layer of lymphocytes and plasma cells in the older grafts. Minimal fibrosis was observed. Tubularized peritoneal free grafts are a promising new urethral substitute. Graft placement is technically simple. Replacement of the peritoneum by a multilayered epithelium resembling transitional epithelium occurs early after graft placement. As much as 1 year later, minimal scarring is present.

Urinary pH and urea concentration correlate to the bacterial colonization rate in gastric, colonic, ileal and myoperitoneal bladder augmentation

We investigated how various types of augmentation cystoplasty alter the native bacteriostatic properties of urine, particularly urinary urea and pH, in the Sprague-Dawley rat. The augmentation cystoplasties studied included 1 cm.2 and 2 cm.2 patches of colon, ileum and stomach as well as myoperitoneal bladder flaps. Augmentations in order of decreasing incidence of bacteriuria and urinary pH are 2 cm.2 ileal greater than 1 cm.2 ileal greater than 2 cm.2 colonic greater than 1 cm.2 colonic greater than myoperitoneal greater than cystotomy alone greater than 1 cm.2 gastric greater than 2 cm.2 gastric. Urinary urea concentrations were similar between cystotomy alone, and myoperitoneal and gastric augments. In contrast, all colonic and ileal augments had significantly lower urea concentrations compared to the aforementioned groups. Our findings suggest that the type and size of augmentation directly affect urinary pH and urea nitrogen concentration, and the incidence of bacteriuria.