The Origin of Regenerating Mesothelium: A Historical Perspective

Bichat first described the mesothelium in 1827 but despite its early discovery, it has only been in recent years that its importance both in health and disease has been realised. One area still poorly understood is that of the mechanisms regulating mesothelial repair. Mesothelial cells are derived from the mesoderm but express many epithelial characteristics. However, mesothelium does not heal in the same way as other epithelial-like cells. Epithelium heals by centripetal migration, with cells at the edge of the wound proliferating and migrating into the injured area. Hertzler in 1919 noted that both large and small peritoneal injuries healed within the same time frame, concluding that the mesothelium could not heal solely by centripetal migration. The exact mechanisms involved in mesothelial regeneration following injury are controversial with a number of proposals suggested to explain the origin of the regenerating cells. This review will examine these proposals and give some insights into the likely mechanisms involved.

State of the Art on Autologous Mesothelial Transplant in Animals and Humans

Sixteen years ago rabbit and human mesothelial cells were successsfully cultured and autoimplanted. The aim of the study was merely to demostrate that mesothelial implant was possible and interesting not only in peritoneal dialysis, but also in the vaster field of medicine and surgery concerning all the mesothelial districts of the body.

The aim of this paper is to recollect the steps which have led to autolougous mesothelial transplantation and verify if the tecnique has been validated and adopted by others.

Review of the literature published in the last 15 years shows that intraperitoneal transplantation of mesothelial cells has been effective in reducing the formation of peritoneal adhesions, and in remodeling the area of mesothelial denudation. New studies on the mesothelial cell opened the way to costruction of transplantable tissue-engineered artificial peritoneum, to the utilization of mesothelial progenitor cells and to find simple metods to collect autologous mesothelial cells.

Finally mesothelial trasnsplantation may represent a new neovascular therapy in the prevention and treatment of ischemic coronaric heart disease.

The peritoneum as a natural scaffold for vascular regeneration

Objective

The peritoneum has the same developmental origin as blood vessels, is highly reactive and poorly thrombogenic. We hypothesize that parietal peritoneum can sustain development and regeneration of new vessels.

Methods and Results

The study comprised two experimental approaches. First, to test surgical feasibility and efficacy of the peritoneal vascular autograft, we set up an autologous transplantation procedure in pigs, where a tubularized parietal peritoneal graft was covered with a metal mesh and anastomosed end-to-end in the infrarenal aorta. Second, to dissect the contribution of graft vs host cells to the newly developed vessel wall, we performed human-to-rat peritoneal patch grafting in the abdominal aorta and examined the origin of endothelial and smooth muscle cells. In pig experiments, the graft remodeled to an apparently normal blood vessel, without thrombosis. Histology confirmed arterialization of the graft with complete endothelial coverage and neointimal hyperplasia in the absence of erosion, inflammation or thrombosis. In rats, immunostaining for human mitochondri revealed that endothelial cells and smooth muscle cells rarely were of human origin. Remodeling of the graft was mainly attributable to local cells with no clear evidence of c-kit+ endothelial progenitor cells or c-kit+ resident perivascular progenitor cells.

Conclusions

The parietal peritoneum can be feasibly used as a scaffold to sustain the regeneration of blood vessels, which appears to occur through the contribution of host-derived resident mature cells.

[Long-term efficacy of tubularized peritoneal free grafts as ureteral mucosal substitutes in dogs]

OBJECTIVE

To investigate the long-term efficacy of ureteral reconstruction with tubularized peritoneal free grafts for the treatment of avulsion of ureteral mucosa in animal models.

METHODS

The model of avulsion of ureteral mucosa was established in 12 adult dogs. Then they were divided into Group A (n = 6, length of avulsed mucosa at 4 cm) and Group B (n = 6, length of avulsed mucosa at 6 cm). And the tubularized peritoneal free grafts and ureteral stents were implanted into the injured ureters. The curative effect was observed by intravenous urethrogram (IVU) and histological examination at Week 24 post-operation.

RESULTS

Severe stenosis was observed by IVU in 1 dogs in Groups A and B respectively. In the remaining 10 dogs, IVU showed normal size and morphology of kidneys. There was no hydronephrosis. And no obvious stricture of ureteral part was observed for mucosa substitutes made of peritoneal free grafts. In all 10 dogs without stenosis of both groups, peritoneal membrane was replaced by integrated transitional epithelium. And there was no obvious stricture. Collagen fibers were arranged parallel to mucosal surface.

CONCLUSION

For avulsion of ureteral mucosa under 6 cm, reconstruction with tubularized peritoneal free grafts as mucosa substitutes is an effective method. And its long-term efficacy is satisfactory.

[Possibilities of rational choice and application of autotissues for hermetization of the suture connections in biliary surgery]

The results of experimental investigation of peculiarities of morphological transformation course in autotissues under the influence of bile were adduced. There was proposed a choice of peritoneum as an optimal plastic material in conditions of possible deficiency of local tissues during biliary surgery performance.

[Vascular graft of aponeurosis with peritoneum in dogs]

BACKGROUND

Vascular autografts are commonly used to repair damage to blood vessels; however, they can be used only with small-caliber vessels. Although synthetic vascular grafts are good options, there may be a high likelihood of thrombus formation.

METHODS

An experimental animal model was used in order to evaluate feasibility and viability of a vascular autograft. Under inhalatory anesthesia, seven mongrel dogs were operated on. A 4-cm vascular autograft was created with the posterior rectus aponeurosis with subjacent peritoneum, leaving the second one as the internal sheath. A 2-cm-long portion of the abdominal aorta was removed and the vascular autograft was inserted by end-end surgical anastomosis. Animals were observed for 7 weeks, evaluating clinical data of vascular insufficiency (intensity of pulse, temperature and trophic changes of the legs). At the end of the experiment, aortography under fluoroscopic visualization was performed. Dogs were sacrificed and autograft removed in order to evaluate permeability.

RESULTS

All dogs survived until the end of the procedure. Vascular autograft was easy to create. During surgery, no evidence of bleeding of the anastomosis or the graft suture was noted. At the end of the procedure, no clinical signs of vascular insufficiency were noted; radiographic evaluation of the autograft showed no dye leakage at any level. Autografts were removed and no signs of thrombus formation were noticed.

CONCLUSIONS

Feasibility of the vascular autograft was demonstrated with good permeability and no thrombogenicity.

[Laparoscopically assisted neovaginaplasty using peritoneum as vaginal mucous substitute]

OBJECTIVE

To practice a more atraumatic, physiological and aesthetically valued approach of construction for neovagina.

METHODS

Laparoscopically using peritoneum as neovagina lining.

RESULTS

From March 2005 to September 2006, this technique was adopted to treat 10 patients whose diagnosis was congenital absence of vagina. The ages of the patients were from 19 to 32. The operation lasted average 2.34 hours. And hospitalization was about 20.5 days. Follow-up ranged from 3 - 12 months. No complication occurred. All of the patients was satisfied with their sexual life.

CONCLUSIONS

Laparoscopically assisted neovaginaplasty, in which peritoneum was substituted for vaginal mucous membrane, was a kind of ideal approach of vaginal creation.

Biological coating for arterial stents: the next evolutionary change in stents

PURPOSE

To describe the in vivo results of a promising new stent-graft lined with peritoneum.

METHODS

Eighteen dogs underwent balloon angioplasty injury to the bilateral iliac arteries followed by placement of either an 8-mm x 5-cm glutaraldehyde-fixed bovine peritoneum- lined balloon-expandable stent (PLS) or a similarly sized, commercially prepared, polyester-lined self-expanding stent (DLS) as a control. Animals were sacrificed at 1 and 6 months. Biplanar arteriography and intravascular ultrasound were done at the time of sacrifice, and the vessels were harvested after perfusion fixation for histology/morphometry. Immunofluorescence with CD34 and factor VIII staining was used to evaluate endothelialization, while alpha-actin was used to quantify smooth muscle cell (SMC) deposition.

RESULTS

At 1 month, all vessels were patent in both groups. At 6 months, 8 of 9 vessels were open in the PLS group versus 6 of 9 in the control DLS group. Vessel lumen diameter at 1 month was significantly greater in the PLS vessels compared to the DLS group at 1 cm above the stent (35.9 +/- 4.4 versus 29.4 +/- 4.7 mm2; p = 0.02) and 1 cm below the stent (37.2 +/- 7.1 versus 25.2 +/- 3.2 mm2; p = 0.005); these results persisted to 6 months. Histological morphometry demonstrated progression of neointimal hyperplasia in the DLS stent between 30 and 180 days (8.3 +/- 1.79 versus 14.9 +/- 6.6 mm2; p = 0.03), whereas the peritoneum-lined stent had no change during the same time period (4.62 +/- 0.98 versus 4.72 +/- 0.97 mm2; p = 0.85). The same patterns were true for the intima:media ratio. Immunohistochemistry demonstrated complete endothelialization at 6 months in both DLS and PLS. However, SMC staining with alpha-actin demonstrated more smooth muscle actin-positive cells in the DLS compared to the PLS (327 +/- 87 versus 262 +/- 73 counts/5 high-powered fields; p = 0.04).

CONCLUSION

Peritoneum-lined stents offer a novel method to improve patency of lower extremity arterial stents.

The role of bovine preserved peritoneum in rats ventral hernia: a histological evaluation

PURPOSE

To assess the role of preserved bovine parietal peritoneum as a material for hernia repair in a rat ventral hernia model.

METHODS

An abdominal wall defect (15mm x 25mm) was created in Wistar male rats (n=40). Control animals (n=20) had the polypropylene (PP) mesh sutured into the defect, whereas bovine preserved peritoneum (BPP) was used in experimental group (n=20). After 7 and 28 days, the abdominal wall was taken off and histological studies of the amount of collagen by Sirius Red stain and morphometric evaluation consisted in quantitative analysis of the collagen by using specific software (Imagelab). The Mann-Whitney, Kruskal-Wallis and ANOVA tests were applied for statistical analysis (pd"0.05).

RESULTS

Histological examination revealed no difference between the BPP and PP groups (p = 0.55 NS).

CONCLUSION

BPP is suitable for the closure of ventral hernias in rat model as shown by its morphological properties.

[Reconstruction of the tongue with rectus abdominis musculoperitoneal flap]

OBJECTIVE

To investigate the outcome of surgical reconstruction of the tongue after hemiglossectomy with reinnervated rectus abdominis musculoperitoneal flaps in the treatment of tongue cancer.

METHODS

Five patients underwent immediate reconstruction of the tongue and oral floor defects with rectus abdominis musculoperitoneal flaps after resection of squamous cell carcinoma of tongue. The rectus abdominis musculoperitoneal flap consists of the rectus muscle, posterior rectus sheath, peritoneum, the 10 th, 11th, 12th intercostal nerves and the vascular pedicle that includes the deep inferior epigastric artery and veins. During the operation a reinnervated rectus abdominis musculoperitoneal free flap, in which the intercostal nerves were anastomosed to the descending branch of hypoglossal nerve, was grafted to remaining tongue stump.

RESULTS

All patients recovered uneventfully from surgery, with no immediate postoperative complications. All transplanted flaps survived. The peritoneum was replaced by squamous epithelium 8 weeks after surgery. The average follow-up period was 10 months. During the follow-up period the contour of the reconstructed tongues was satisfactory. The patients demonstrated good functional mobility of the reconstructed and remaining tongue. The swallowing and speech function was nearly at normal levels and the patients could ingest a solid or semisolid diet.

CONCLUSIONS

Reconstruction of the tongue with rectus abdominis musculoperitoneal flaps after hemiglossectomy is a suitable, cosmetically acceptable method. Long-term follow-up is needed for reaching some final conclusions.

[Comparative experimental study of left colonic anastomoses in intestinal obstruction; the value of anastomoses protection with free peritoneal graft]

The paper describes the concept of peritoneal graft used to reinforce the colo-colic anastomoses made in emergency conditions of left colic obstruction, experimentally induced by surgical ligature, on Wistar rats. The comparative study was done on 24 rats, divided in 3 groups: group A with colic anastomoses protected with peritoneal graft, group B with one-layer colic anastomoses and group C with two-layer colic anastomoses. After 8 days, 7 rats survived in group A, 2 rats in group B and 3 rats in group C. All surviving rats in groups B and C presented anastomotic leak with local peritonitis, while in group A the anastomosis were healed. For group A, bursting strength of the anastomosis was measured and the mean value found was 63.64 cmH2O. It was proved the importance of protecting the colic anastomosis with supplementary layers, which increase the mechanical resistance and also prevents minor spillage of the colic content during the first postoperative days.

Successful treatment of cervical aplasia using a peritoneal graft

OBJECTIVE

To evaluate the efficacy of a peritoneal graft for the treatment of cervical aplasia.

METHOD

Four patients with cervical aplasia who had a functioning endometrium and hematometra were recruited for this clinical trial. Through an abdominoperineal approach a plastic stent was inserted between the endometrial cavity and the upper part of the vagina; then, a graft of peritoneum was applied over the stent. In the absence of a vagina, grafts of skin or amniotic membrane were also used. The plastic stent was removed after 1 month in 2 patients and after 1 week in the 2 other patients.

RESULT

After more than 1 year of observation the 4 patients had regular menstrual cycles with normal menstruation. Sonographic examinations also showed empty uterine cavities.

CONCLUSION

Traditional gynecology textbooks recommend hysterectomy in cases of cervical aplasia. This report presents a new technique with 2 variations using a peritoneal graft. Although both variations were successful in the treatment of cervical aplasia in 4 women, more trials are needed to determine which one should be developed.

Free peritoneal graft for repair of severe seromuscular defect of bowel: from experiment to clinical practice

BACKGROUND

Severe seromuscular tear of the bowel with impending perforation following enterolysis or trauma is not uncommon in gastrointestinal surgery. It is sometimes complicated with enterocutaneous fistula, intra-abdominal abscess or free perforation, especially of the ileus. In addition, direct serosal repair is often impossible, or complicated by lumen compromise. Serosal patch repair also reportedly is also associated with complications such as dislodgement of the sutured bowel loop, fistula formation, adhesion ileus, or volvulus. Free peritoneal graft (FPG), as in split-thickness skin graft (STSG), can be taken by underlying healthy tissue within 24 to 48 h and used for repair of such defect.

PATIENTS AND METHODS

In this study, FPG was used as an alternative to serosal patch repair or resection to cover severe defects of the colon, rectum, duodenum, or small bowel in 30 consecutive patients. All defects were over 8 x 4 cm in size and involved 30 to 80% of the circumference of the bowel wall. Each defect was deep enough to expose the thin mucosal layer, with the intestinal content visible through it. These defects could have been successfully treated by resection or repair using a serosal or mucosal patch instead of FPG. After making sure that the mucosa associated with the defect was alive and not perforated, a patch of intact peritoneum with pre-peritoneal tissue from the lateral abdominal wall (slightly smaller than the defect) was superimposed, with the edges simply sewn to the margin of the defect.

RESULTS

All patients recovered uneventfully, with no untoward effects determined, even after long-term follow-up.

CONCLUSION

We believe that FPG provides a feasible, simple, effective, economic, and safe alternative for repair of severe seromuscular defects; potentially making it widely applicable in clinical practice.

In vivo and mechanical properties of peritoneum/fascia as a novel arterial substitute

OBJECTIVE

This study evaluates the efficacy of bovine peritoneum/fascia as an arterial substitute.

METHODS AND OUTCOME MEASURES

Twelve dogs underwent bilateral femoral artery patch angioplasty with a glutaraldehyde-fixed bovine peritoneal/fascial patch (PFA patch) on one side and polyester patch on the contralateral side. Arteriograms were performed just before vessel harvest at 1 and 6 months, and vessels were evaluated for aneurysms and inflammation. Histologic analysis included intima area, media thickness, and lumen area. Immunofluorescence for CD 34 and Factor VIII was done to evaluate endothelialization and alpha-actin for smooth muscle cell growth. Mechanical strength testing was evaluated in separate PFA patches and compared independently to a commercially available bovine pericardial patch and polyester patch.

RESULTS

All vessels examined at both 1 and 6 months were patent with no arteriographic evidence of stenosis. There was no evidence of aneurysm formation in any vessel and no difference between groups in inflammatory reaction. One polyester patch at 1 month developed an infection. Microscopic evaluation of experimental vessels revealed no difference between groups in intima area at 1 month (2.1 +/- 1.2 vs 2.2 +/- 1.2 mm 2 ; P = .5) and at 6 months (1.81 +/- 1.2 vs 1.9 +/- 1.2 mm 2 ; P = .5). There was no difference in media thickness, but the PFA patch group had a greater lumen area at 1 month (8.8 +/- 2.9 vs 9.8 +/- 3.0 mm 2 ; P = .02) and 6 months (10.5 +/- 4.2 vs 11.7 +/- 5.6 mm 2 ; P = .02). Immunofluorescence for CD34 and Factor VIII demonstrated complete re-endothelialization of all patches. The polyester patch had a chronic inflammatory response, but not the PFA patch. Mechanical strength testing demonstrated that compared to pericardium, the PFA patch had superior ( P < .05) failure tension, stiffness, and suture pull-out strength, whereas extensibility, fatigue tension, relax slope, and creep tests were not different. Polyester demonstrated superior suture pull-out, stiffness, relax slope, and failure strain ( P < .05), but it was not different in failure tension and extensibility than the PFA patch. However, the PFA patch had significantly less creep (0.25 +/- 0.25 vs 4.92 +/- 0.84; P < .01).

CONCLUSIONS

The PFA patch has similar clot-resistant properties to polyester and is superior to the pericardial patch in mechanical strength. It is a promising endothelial alternative for not only arterial patches but other vascular products.

CLINICAL RELEVANCE

The search for an artificial, thromboresistant, and intimal hyperplasia resistant interface between blood and native blood vessels still continues. This study demonstrates the feasibility and proof of concept of the peritoneum's clot-resistant properties. When adding the underlying fascia, it serves as an ideal arterial patch. Other studies are underway evaluating its feasibility as a bypass graft and a "drug coated"-like stent lining.

[Experimental use of the peritoneal graft as a vascular prosthesis]

INTRODUCTION

The parietal peritoneum appears to be a suitable material for the vascular system reconstructions.

AIM

The aim was to assess and compare thrombogenicity and ability for endothelization of the mesothelial and submesothelial side of the parietal peritoneum in the canine venous system.

MATERIAL AND METHODOLOGY

EXPERIMENTAL ANIMALS

canis familiaris (n = 13), half-breeds of both sexes, aged between 1 and 2 years, weighting 15-25kgs, underwent authological transplantations of the peritoneal grafts with the mesothelial side in the lumen- the group M (n = 5) and with the submesothelial side in the lumen the group S (n = 5). In the control group K (n = 3) a part of the venous wall was used as a graft and was affixed back to its original place. The bioptic samples collected on the 10th, 20th, 30th and 40th postoperative day (POD) were stained using the HE staining, NADPH-d and imunohistochemically on the intermedial filaments. The endothelization rate of the peritoneal graft was measured using morphometry and the trombogenicity was assessed peroperatively.

RESULTS

In none of the trial groups a presence of thrombi was detected peroperatively. In the first trial group (group M), the onset of the peritoneal graft epithelization (reaching 20%) was recorded on the 10th POD. The endothelization process was completed on the 30th POD in this trial group. In the second trial group (group S), the peritoneal graft epithelization reaching 10% was recorded on the 10th POD. The process was completed on the 40th POD. In the third trial group K, no endothelial changes were recorded during the experiment.

CONCLUSION

Both sides of the peritoneum do not show signs of thrombogenicity and possess ability for endothelization.

[Peritoneal-fascia-muscle autologous graft in the inguinal canal of rats]

PURPOSE

To study the fragment of the autologous tissue, built by a peritoneum-fascia-muscle, implanted on the level of the wall of inguinal canal and the spermatic cord of rats aiming to verify the histological behavior of the survive and the tissue incorporation.

METHODS

Thirty-six rats were distributed into four groups. The rats of the group A, B, C and D were submitted to the median laparotomy to obtain the species to be implanted. On the group A, was implanted a tissue compounded by peritoneum and transversal fascia on the wall of the inguinal canal. On the B, the tissue implanted was added a part of rectum muscle of the abdomen and implanted on the wall of the inguinal canal. On the C, the tissue grafted was similar to the groupA, now grafted into the spermatic cord. On the D, the tissue was similar to the group B, now grafted into the spermatic cord.

RESULTS

After 21 days of implant, these tissues presented the following histological alteration: the group A and C, fibroadipous tissue with dilated vessel, Focus of fibrosis' and limphoplasmocitary infiltrated and the groups B and D, fibroadipous tissue with dilated vessels, skeletal muscle and focus of fibrosis. The fibrosis displayed on the groups B and D was more intensive. On the group B, we almost always find the skeletal muscle, while on the group D this tissue was presented in six animals, almost replaced by fibrosis in two and not present in one.

CONCLUSION

All the implanted grafts displayed survive and local incorporation, what could be useful on the correction of defects on the inguinal canal, on situations when the autologous tissue was indicated.

Repair of duodenal fistula with rectus abdominis musculo-peritoneal (RAMP) flap

INTRODUCTION

Large duodenal defects/fistulae are difficult to repair, due to complex duodenal anatomy. Musculo-epithelial flaps are conventionally used for reconstruction of large soft tissue defects. We report the clinical use of rectus abdominis musculo-peritoneal (RAMP) flap for repair of duodenal fistulae.

METHODS

Eight patients with duodenal fistulae underwent repair using right RAMP flap, based on the position of the superior epigastric artery. Feeding jejunostomy was done routinely to start early enteral feeding.

RESULTS

Duodenal fistulae healed within 3-5 days in all the cases except one, in whom bile continued to leak for 30 days. One patient died within 12 hours of second surgery. Superficial wound infection was a common (n=3) cause of morbidity.

CONCLUSION

RAMP flap for closure of duodenal defect is a simple, technically easy and dependable procedure, which can be performed quickly in critically ill patients. It can be used for repair of large duodenal defects with friable edges when omentum is not available or when other conventional methods are impractical.

Reconstruction of the Vena Cava with the Peritoneum: The Effect of Temporary Distal Arteriovenous Fistula on Patency (An Experimental Study)

OBJECTIVE

To determine the effect of increasing inferior vena cava blood flow by means of distal arteriovenous fistula on the patency of a peritoneal tube graft.

MATERIALS AND METHODS

In 16 mongrel dogs, a 3-4 cm long circular defect was created at the infrarenal inferior vena cava. The defect was interposed with peritoneal tube graft. A temporary distal femoro-femoral arteriovenous fistula was also constructed in 8 dogs just after the caval interposition. Graft patency was evaluated by Doppler ultrasonography and angiography. Histological evaluation was also performed.

RESULTS

Seven dogs in each group survived. All control grafts occluded within the first week, compared to no occlusions in fistula group (Fisher's exact test, p<0.005). However one 'fistula' dog with a still patent graft was sacrificed on the 18th day due to ultrasonographically occluded arteriovenous fistula.

CONCLUSION

In dogs, the peritoneum may be used as graft material for reconstruction of the inferior vena cava, provided a distal arteriovenous fistula is constructed.

Use of fascia-peritoneum patch as a pledget for an infected aortic stump

Treatment of aortic prosthetic graft infections remains a challenge. One frequently encountered technical difficulty when removing an infected prosthetic aortic graft is how to close a short, friable remnant aortic stump. We present three case reports in which we used a layer of posterior rectus fascia-peritoneum to bolster oversewing a short infected aortic stump after removal of an infected aortic graft. All three patients underwent staged extra-anatomic axillary-to-femoral artery bypass procedures, with subsequent removal of the infected aortic graft as a second operation. Two of the three procedures were semi-elective, and one was done urgently because of a recurrent aortoenteric fistula. All three patients had less than 1 cm of remaining aortic neck below the renal arteries for closure. In each instance a segment of autogenous posterior rectus fascia-peritoneum was harvested and used as a circumferential pledget to bolster the anastomosis. No patient had stump blowout, and in no case was there computed tomography evidence of aneurysmal enlargement of the stump with follow-up of 12 and 24 months in two of the three survivors. Use of autogenous fascia-peritoneum is a durable and effective method to assist stump closure and prevent stump blowout after removal of infected aortic grafts.

Omentum pediculed musculo-peritoneal flap (OPMP) for growing intestinal neomucosa in a rat model

BACKGROUND/PURPOSE

To construct a musculo-peritoneal flap adequately vascularised through attached omentum and to evaluate whether this flap is functional for growing new intestinal mucosa.

METHODS

24 rats underwent two surgical procedures. 1) A musculo-peritoneal flap was prepared, omentum was fixed onto the muscular side and a silicon graft was placed on the peritoneal side. 2) After one month the so constructed OPMP flap was mobilised and attached to the jejunum. Animals were harvested at 2, 4 and 8 months for macroscopic and microscopic evaluation.

RESULTS

One rat died at 7 months due to intestinal volvulus. In the remainder the circumference of the patched intestine significantly increased compared to that of normal intestine (p<0.001). The flaps were markedly contracted in the 4 month rats (p<0.01). All flaps were completely covered by neomucosa except in the 2 month rats. Crypt depth and crypt density of the neomucosa was significantly lower in 2 month rats compared to other groups (p<0.05). Similarly neomucosal villous height was markedly low in the 2 month rats (p<0.01).

CONCLUSIONS

To date, we have found no reports of small bowel patching using this technique. In this context, use of OPMP flap is likely to be useful for increasing intestinal surface area.

Middle hepatic vein reconstruction using a peritoneal patch: report of a case

A 67-year-old male complaining of constipation with a change in stool caliber for several months visited our hospital in June 1999. A positive test for occult blood in the feces led to the disclosure of a type II carcinoma of the sigmoid colon with multiple liver metastases. A lymph node dissection with a sigmoidectomy disclosed no metastases histologically, so a left hepatectomy and enucleations of the metastases were performed. In addition, the invaded middle hepatic vein (MHV) was resected and repaired using a peritoneal patch. The patient's postoperative course was uneventful until July 2000, when computed tomography of the liver showed a single nodule measuring 3 cm in diameter in segment 6. The metastasis was excised in August. Since then, the patient has shown normal tumor marker values. The MHV has remained patent for 24 months after its reconstruction. A resection of the liver metastases including venous reconstruction is beneficial for patients since it results in a longer survival and allows for venous drainage of the residual liver. The peritoneum is also accessible, enabling the fitting of a patch graft for hepatic vein repair.

Autoaugmentation peritoneocystoplasty in a sheep model

OBJECTIVE

To report our experience with autoaugmentation peritoneocystoplasty (AAPC) in a sheep model, and to compare the results with autoaugmentation gastrocystoplasty (AAGC) in a sheep model and in paediatric patients.

MATERIALS AND METHODS

Ten 6-month-old male lambs underwent bladder augmentation by detrusorotomy. A flap of parietal peritoneum, dissected from the anterior abdominal wall, was used to cover the bladder mucosa. The sheep were evaluated by urodynamics 6 months after surgery. Bladder compliance (bladder volume/intravesical pressure) was calculated for the bladder capacity at leakage. The urodynamic results were compared with age-matched control sheep and with 12 sheep that had undergone AAGC; the results were assessed using the Mann-Whitney U-test.

RESULTS

In two of the 10 sheep, bladder volumes after AAPC increased by > 100%, although for the group, the mean (range) bladder volume after augmentation, at 159 (42-261) mL, was not significantly different from that before surgery (mean 143 mL). Bladder volumes after AAPC were not significantly different from those in the control sheep (mean 205 mL) but were significantly less than in the AAGC group (mean 317 mL; P < 0.05). Bladder compliance at leak capacity in the AAPC group (mean 5.4 mL/cmH2O) was also not significantly different from the controls (mean 9.1 mL/cmH2O), but was lower than the in the AAGC animals (median 14.6 mL/cmH2O; P < 0.05).

CONCLUSIONS

AAPC in a sheep model does not result in a reliable increase in bladder volume or compliance. The volume and compliance are inferior to those found in bladders augmented by AAGC.

Reconstruction of the portal vein using a peritoneal patch-graft

BACKGROUND

Reconstruction of the portal vein with autologous veins requires extra incisions. Prosthetic material is associated with an increased risk of infection. We therefore created an animal model of portal vein reconstruction using the peritoneum.

METHODS

A 2.5 x 2.5 cm piece of the peritoneum was resected from Landrace pigs weighing 30 to 40 kg and was dipped in 100% alcohol for 10 minutes. The anterior wall of the portal vein measuring 1.2 x 0.6 cm was resected. The peritoneal patch-graft fitting the defect of the portal vein was used to repair it.

RESULTS

All 7 pigs survived the surgery, and were killed at 2, 7, 7, 14, 21, 35 and 49 days, respectively, after surgery. There was no evidence of thrombosis or obstruction of the reconstructed portal vein or any other complications. Complete endothelialization of the patches were noted at day 14.

CONCLUSIONS

Our patch-graft technique using the peritoneum is considered to be a good and safe alternative for reconstruction after partial resection of the portal vein in clinical surgery.

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.

Animal experimental study on surgical repair of hypospadias by free peritoneal graft

Surgical repair of hypospadias was successfully performed by using free peritoneal graft in the model of rabbit hypospadias. The results showed that free peritoneal graft used as a substitute for urathra had a high survival rate, and the canal was formed well. Our study demonstrated that peritoneum could be used for the surgical repair of hypospadias and other urethral disorders such as urethral stricture.

Reconstruction of the vena cava with the peritoneum

BACKGROUND

Reconstruction of the vena cava with an autologous vein requires extra incisions. Prosthetic material is associated with an increased risk of infection. We therefore created an animal model of vena cava reconstruction using the peritoneum.

METHODS

A 2.5 x 2.5 cm piece of peritoneum was resected from 7 pigs weighing 30 to 40 kg. An oval window (long axis: 1.5 cm) was made in the infrarenal vena cava. This was repaired with the peritoneal patch fixed in alcohol.

RESULTS

In 2 animals sacrificed at 5 hours, there was no evidence of thrombosis, but there was fibrin clot on the patches. Two animals sacrificed on day 8 exhibited excellent patency of the vena cava. Complete endothelialization of the patch was noted at day 15. At 6 weeks, the vena cava was healed. No infections or other problems were noted.

CONCLUSIONS

The peritoneum is an accessible and safe substitute for reconstruction of the vena cava.

Organogenesis and tissue regeneration of fallopian tube: a desired metaplastic transformation of mesodermal stem cells in live animal models (dogs)

The capacity of stem cells of peritonium of mesodermal origin to undergo metaplastic transformation and form different tissues developed from mesoderm germ layer is exploited with ulterior motive to use it in the management of human diseases. The excised fallopian tube was replaced with a tube on a stent constructed from autogenous peritoneum from a suitable donor site. The effect of the surroundings environment of the new tissue system to which the peritoneum stem cells are now exposed was studied for 3, 6 and 12 months period in live animal models. The gross and histological studies revealed development of all the component of the wall of the fallopian tube. The lumen of the constructed peritoneal tube was well preserved in its whole length including the anastomotic sites. The scientific rationale of the working hypothesis on which the work is based, is discussed.

[The peritoneal autoplasty of the hernial hili in patients with large strangulated recurrent inguinal-scrotal hernias]

A new method of operative treatment of incarcerated recurring great inguinal-scrotal hernias is proposed with the help of plasty of the posterior wall of the inguinal canal with cicatricial changes to the tissues of the hernial sac. This method was used in operations on 56 patients aged 45-80 years. There were no postoperative recurrences of the disease or lethal outcomes.

Bladder augmentation with urothelial preservation

PURPOSE

Bladder reconstruction is performed because the characteristic properties of a healthy bladder are no longer present. The bladder manifests poor capacity, poor compliance and potential or actual changes in the upper tracts that may lead to damage. Augmentation procedures provide a means to improve capacity and compliance, and they may be performed with catheterizable channels to facilitate bladder emptying. Natural tissues or synthetic materials may be used but urothelial preservation is desirable. Demucosalized augmentation with a gastric flap and auto-augmentation with peritoneum are techniques that have been used in the last 5 years.

MATERIALS AND METHODS

We retrospectively evaluated the records of 13 patients who underwent demucosalized augmentation with a gastric flap and 8 who underwent augmentation with peritoneum from 1992 to 1995. Average age of the 11 girls and 10 boys was 8 years (range 6 to 12). The diagnosis was myelomeningocele in 15 patients, exstrophy in 2, and the VATER association, posterior urethral valves, spinal cord injury and nonneurogenic neurogenic bladder in 1 each. Concurrent procedures included appendicovesicostomy creation, a fascial sling or wrap and ureteroneocystostomy.

RESULTS

Mean followup is 50 months for patients who underwent demucosalized augmentation with a gastric flap and 47 for those who underwent augmentation with peritoneum. Outcome was defined as good-dry for 4 hours, catheterization without difficulty and a stable upper tract; poor-a secondary procedure (augmentation) required because the initial procedure did not improve bladder capacity, compliance, continence or the degree ofhydronephrosis, and fair-dry for less than 4 hours, some problems with incontinence, or compliance 10 ml/cm water or less. Of the patients who underwent demucosalized augmentation with a gastric flap the outcome was good in 5, fair in 4 and poor in 4 who required repeat augmentation. Of the 8 patients who underwent auto-augmentation with peritoneum the outcome was good in 5 and poor in 2, and 1 was lost to followup.

CONCLUSIONS

Augmentation with urothelial preservation may result in a good capacity, compliant bladder in certain patients but a poorly compliant, small capacity bladder in others. Our overall results underscore the lack of understanding of the properties and characteristics of these bladders and of stromal-epithelial interaction that occurs after augmentation. Such an understanding is critical before this procedure can be recommended routinely.

Regeneration of abdominal wall aponeurosis: new dimension in Marlex peritoneal sandwich repair of incisional hernia

Loss of abdominal wall substance is a major cause of incisional hernia formation. It makes repair of this iatrogenic human ailment a difficult surgical problem. The abdominal wall substance loss has compelled the world's surgical community dealing with this condition to substantiate the repair with extra material such as skin, fascia, wire mesh, and lately biocompatible synthetic mesh. Even though the synthetic mesh is compatible and well tolerated by body tissues, it is not without complications. Regenerative repair in the region of the abdominal wall with substance loss is probably the best repair if it can be achieved. With reasonable success in animal experiments and the positive regenerative capacity of stem cells to transform the peritoneum into an aponeurotic layer, the new technique using a Marlex peritoneal sandwich for repair of large incisional hernias was attempted but was not reported in the article published in the World Journal of Surgery in 1991. The present study is based on experiments on seven mongrel dogs. A suitable embryonal segment of autogenous peritoneum was excised and transferred to the rectus sheath region. The gross appearance of the grafted membrane 3 months after operation revealed tough, thick tissue formation. The histology confirmed the presence of collagen fiber tissue in layers similar to the aponeurosis in the grafted peritoneal membrane. The use of this regeneration in the Marlex peritoneal sandwich technique of repair of large incisional hernias and the scientific rationale of tissue regeneration by desired metaplasia is discussed.

Inferior vena caval resection with autogenous peritoneo-fascial patch graft caval repair: a new technique

BACKGROUND

In the course of oncological surgery, resection of the inferior vena cava (IVC) may be required to obtain an adequate resection margin and to offer the best opportunity of cure. The remaining defect in the IVC may be managed by: (i) primary repair which may lead to subsequent narrowing of the lumen, possibly leading to turbulent flow and thrombus formation; (ii) patch grafting of the defect, which may prevent narrowing. Several synthetic and biosynthetic materials are available as patch grafts and autologous pericardium has also been used.

METHODS

The harvesting and use of the autogenous peritoneo-fascial (APF) graft as an alternative caval patch graft material in the management of defects in the caval wall is proposed. Autogenous peritoneo-fascial caval patch graft repair in six patients was undertaken.

RESULTS

One patient with leiomyosarcoma secondaries in the liver eventually succumbed to the disease. The other five patients are clinically well with no evidence of IVC obstruction or venous aneurysms.

CONCLUSION

Preliminary results show that this new technique of utilizing an APF patch graft for caval repair is clinically a suitable alternative to current biosynthetic and synthetic materials and may in fact be superior in many aspects.

[Study on the replacement of the portal vein of pig with autogeneous-peritoneal tube]

OBJECTIVE

To investigate the possibility of applying autogeneous peritoneal tube in the portal vein reconstruction.

METHODS

Twenty-seven small healthy domestic pigs were used. A section of portal vein about 2.5-3.0 cm long was resected and replaced by autogenous peritoneum tube (APT), autogenous vein and decron artificial blood vessel respectively. Patency and pathological changes of the APT grafts were investigated after the replacement.

RESULTS

Twenty-four animals survived the operation. In the early stage of replacement, the APTs were dilated slightly, the cannual patency rate (CPR) was 12/13(92.3%). 3 months later, the fibrous hypertrophy and thickness were observed. The CPR was 8/10(80%). 2 more months later, the CPR was 4/6(66.7%), which was quite similar to that reconstructed by autogeneous vein. All three pigs which were replaced by decron blood vessel were dead within three to five hours after operation because of portal thrombi found by autopsy. After 12 weeks of replacement, scanning electron microscopy revealed that APT grafts were covered with a layer of endothelial-like cells. Endothelial cells and mesothelial cells were seen under transmitted electronic microscopy.

CONCLUSIONS

The long-term patency of the APTs were slightly lower than that of the autogenous vein, peritoneum might be a perspective self-material for portal vein reconstruction and worth further studying.

Fascioperitoneal graft with T-tube drainage for patching bile duct defects

Reconstruction of choledochal wall defects in an experimental dog model by T-tube plus fascioperitoneal graft and an evaluation of the short-term results were the aims of this study. Twelve randomly selected mongrel dogs of both sexes, having an average weight of 22.15 +/- 1.85 kg, were anaesthetized with ketamine HCI and xylazine and underwent laparatomy. The front wall of choledoch canal were excised with its all layers 0.5 cm in diameter at the distal part of the cystic duct junctions. These defects were repaired by using grafts prepared of the same diameter from the dorsal fascias of rectus muscles and peritoneum. T-tubes were introduced into the common ducts on the proximal part of the grafts. One of the animals died in the postoperative period due to evantration. T-tube cholangiograms on the twelfth day did not indicate any extravasation or stricture. Histopathological examination of the graft regions on the sixtieth day revealed that the epithelialization had commenced on the border between the bile epithelium and grafts. Based on these early findings, it was suggested that if supported by further studies it may be thought of as a clinical method.

Adhesion formation of the parietal and visceral peritoneum: an explanation for the controversy on the use of autologous and alloplastic barriers?

OBJECTIVE

To compare formation of adhesions after injury to both parietal and visceral peritoneum and to determine the benefit of autologous transplants and alloplastic barriers in adhesion prevention.

DESIGN

Experimental prospective animal study and prospective randomized clinical study.

SETTING

An academic research environment.

PATIENT(S)

Forty women undergoing laparoscopy for endometriosis treatment.

INTERVENTION(S)

In 60 rats, either the visceral or parietal peritoneum was injured and covered with autologous peritoneal transplants in half of the animals. The formation of adhesions was assessed 21 days postoperatively. In women, adhesions were evaluated 3 months after surgery with or without placement of alloplastic barriers on visceral lesions.

MAIN OUTCOME MEASURE(S)

Adhesions evaluated according to a scoring system.

RESULT(S)

Adhesions after injury of the visceral peritoneum in rats were significantly more severe than those from the parietal peritoneum. Autologous peritoneal transplants led to fewer adhesions especially after serosal injuries. Female volunteers treated with alloplastic barrier material showed less severe adhesions than the control group.

CONCLUSION(S)

The present data indicate that the potential to form adhesions is significantly higher in visceral than in parietal peritoneal lesions. The development of adhesions after injury to the visceral peritoneum could be reduced by a synthetic barrier material.

A new biologic membrane in cardiovascular surgery

Reconstruction techniques for major vessels and intracardiac defect repair use synthetic grafts or autogenic pericardium. Here, autologous abdominal parietal peritoneum with the overlying posterior rectus sheath as a biologic membrane are evaluated. Twelve adult canines were used. Via a midline subumbilical incision, the parietal peritoneum and overlying posterior rectus sheath were harvested. In the first group of six, the membrane was used to repair the right ventricular infundibulum and perform pulmonary artery annuloplasty. In the second group of six, under cardiopulmonary bypass and moderate hypothermia, the right atrium was opened and a secundum type defect was created. Autopsies performed 90 days after surgery revealed mild intrapericardial adhesions and moderate pericardial reaction over the cardiotomy incisions. The right ventricular outflow tract patch was nonaneurysmal. The interatrial patch was intact without thrombi. Histologic examination revealed intact membrane morphology, fibroblasts, smooth muscle cells, and endothelialization. Proline C14 uptake and autoradiography detected cellular viability of implanted membranes. These findings suggest that the peritoneum with overlying sheath repaired vascular and intracardiac defects and substituted for pericardium. Future studies are needed before clinical use.

Protection of intestinal anastomoses in septic environment with peritoneal graft and polyglycolic acid mesh: an experimental study

We carried out an experimental study in dogs to evaluate the outcome of large bowel anastomosis with 6 stitches (Group C, n : 6) in a septic environment with protection by a polyglycolic acid (PGA) mesh (Group M, n : 12) or peritoneal graft (Group P, n : 12). Thirty dogs were used to compare the techniques. Two dogs in each group were re-operated after 3, 5, 7, 14, 28 and 90 days. They were evaluated for adhesion formation, lumen diameter (anastomotic index), clinical features, histologic appearance and quality of healing at the anastomotic sites. All dogs in group P and group M survived, whereas 2 dogs in the control group died of anastomotic leakage and 3 dogs were re-operated for anastomotic leakage and peritonitis. In group M, one dog was reoperated because of the anastomotic leakage and two dogs were reoperated because of the anastomotic stenosis. Also, 4 anastomoses showed evidence of moderate stenosis. In group P, three anastomoses were graded as minimal stenosis. Histopathologic evaluation showed more complete epithelization, less inflammation, and less adhesion in group P than group M. We could not find any study in the literature that described and compared both techniques. We report here the results of such a study.

Formation of neoureter from peritoneum in live animal model (dog)

Regeneration of ureter in vivo is possible from peritoneal stem cells as both are derivative of embryonal germ layer mesoderm. The peritoneal stem cells are engaged in repair of loss due to normal wear and tear by differentiation and proliferation. With pluripotent nature, they have a capacity to undergo metaplastic transformation to various mesodermal tissues. The intrinsic cell factor along with regional tissue organisers coupled with functional need of the region, a desired metaplastic transformation to ureteric wall components is possible.

Reconstruction of the flexor tendon sheath. An experimental study in rabbits

The role of the tendon sheath in flexor tendon healing was investigated in rabbits. Tendon sheath was reconstructed with syngeneic parietal peritoneum or a non-tanned processed porcine collagen membrane. Resection of the tendon sheath led to adhesions. Reconstruction of the sheath with either graft resulted in a synovial-like lining, resembling a neo-tendon sheath. Even when combined with tendon repair a neo-tendon sheath was seen after reconstruction with both grafts, without adhesions. Subcutaneously implanted processed porcine collagen membrane was completely resorbed in less than 3 months.

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.

Results of modified laparoscopically assisted neovaginoplasty in 18 patients with congenital absence of vagina

Construction of a neovagina using pelvic peritoneum via a laparoscopically assisted approach was used in 18 patients with congenital absence of the vagina. A better operative procedure is reported, which was modified from our preliminary technique, and the results of treatment are evaluated. Pelvic peritoneum was used for construction of a vagina, replacing a laparotomy by a minimally invasive laparoscopic approach. During follow-up, the advantages of our procedures are: (i) minimal likelihood of 'poor take' or later contraction because an autograft peritoneal epithelial line is used; (ii) minimal short and long term care is required; (iii) the technique is simple in experienced hands and has all the well-recognized benefits of minimal invasive surgery; (iv) the average length of neovagina is adequate and patency and depth can be maintained with minimal dilatation; (v) the neovagina, with epithelial lining resembling that of a normal vagina, facilitates comfortable sexual intercourse; (vi) the procedure is unaccompanied by dyspareunia or scarring, which are frequently associated with other techniques; (vii) less emotional stress and better cosmetic and economic benefits are noted.

Experimental evaluation of peritoneum and pericardium as dural substitutes

Although many substances have been tested in the search for an ideal dural substitute, an entirely satisfactory material has still not been found. The authors report an experimental study involving the closure of dural defects in rabbits with biomaterials developed from pig peritoneum and pericardium. Macroscopic and histologic examination, performed over a period between 15 and 45 days after implantation showed slight or no adhesion between the graft material and the cortex. No infection, CSF leakage, fistula or toxicity was noticed. The results demonstrated that these biomaterials could be used as satisfactory dural substitutes.

Short phase efficacy of autologous peritoneum as a pericardial substitute

The risks associated with resternotomy are largely related to loss of pericardial integrity. No satisfactory substitute for pericardium has been identified. The structural similarity between pericardium and peritoneum prompted an assessment of the latter as a biologic substitute. Two peritoneal patches were harvested from four juvenile swine, which then underwent left thoracotomies. In each pig, two pericardial defects were created and repaired with fresh and glutaraldehyde treated autologous peritoneal patches. Three weeks post operatively, the chest and abdomen were re-explored and the patches evaluated. In all cases, extrapericardial adhesions were insignificant. On gross examination of the intrapericardial surfaces, the fresh patches appeared smooth and glistening, with neither degenerative changes nor adherence to the epicardium. The treated patches were easily separated from the epicardium in two cases, but the other two patches were moderately to severely adherent. Histologic examination demonstrated well preserved morphology in all patches. C proline uptake and autoradiography revealed preserved fibroblast viability in the fresh patches. Intra abdominally, in all cases, there was complete reperitonealization without adhesion formation. In conclusion, fresh autologous peritoneum performed well as a pericardial substitute after heart surgery.