Intraperitoneal Placement Research Articles

Prospective Evaluation of Adhesion Formation and Shrinkage of Intra-Abdominal Prosthetics in a Rabbit Model

Laparoscopic ventral hernia repair requires an intraperitoneal prosthetic; however, these materials are not without consequences. We evaluated host reaction to intraperitoneal placement of various prosthetics and the functional outcomes in an animal model. Mesh (n = 15 per mesh type) was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included ePTFE (DualMesh), ePTFE and polypropylene (Composix), polypropylene and oxidized regenerated cellulose (Proceed), and polypropylene (Marlex). Adhesion formation was evaluated at 1, 4, 8, and 16 weeks using 2-mm mini-laparoscopy. Adhesion area, adhesion tenacity, prosthetic shrinkage, and compliance were evaluated after mesh explantation at 16 weeks. DualMesh had significantly less adhesions than Proceed, Composix, or Marlex at 1, 4, 8, and 16 weeks (P < 0.0001). Marlex had significantly more adhesions than other meshes at each time point (P < 0.0001). There were no statistically significant differences in adhesions between Proceed and Composix meshes. After mesh explantation, the mean area of adhesions for Proceed (4.6%) was less than for Marlex (21.7%; P = 0.001). The adhesions to Marlex were statistically more tenacious than the DualMesh and Composix groups. Overall prosthetic shrinkage was statistically greater for DualMesh (34.7%) than for the remaining mesh types (P < 0.01). Mesh compliance was similar between the groups. Prosthetic materials demonstrate a wide variety of characteristics when placed inside the abdomen. Marlex formed more adhesions with greater tenacity than the other mesh types. DualMesh resulted in minimal adhesions, but it shrank more than the other mesh types. Each prosthetic generates a varied host reaction. Better understanding of these reactions can allow a suitable prosthetic to be chosen for a given patient in clinical practice.

Migration of the peritoneal tip of a ventriculoperitoneal catheter causing shunt malfunction

This 6-year-old boy presented with a short history of headache, nausea, and vomiting. He was born prematurely at 24.5 weeks of gestational age and suffered an intraventricular hemorrhage causing hydrocephalus. A ventriculosubgaleal shunt was inserted 4.5 months later, which was converted after 1 month to a ventriculoperitoneal shunt with a medium-pressure valve. The peritoneal catheter was placed using a trocar; no purse-string suture was placed around the opening. An intraoperative lateral radiograph of the abdomen confirmed intraperitoneal placement of the catheter. The shunt was revised twice at the upper end. The last revision had been 3 years prior to presentation, when the valve was changed to an Orbis Sigma valve (Integra NeuroSciences; Sophia Antipolis, France). Upon admission to our institution, the boy was lethargic but otherwise normal neurologically. A computed tomography scan of his head showed no change in ventricular size (Fig. 1), and radiographs of the shunt were nondiagnostic. The patient’s neurological condition subsequently deteriorated, necessitating a shunt revision. During the surgery, the ventricular end was found to be working, but the peritoneal catheter was blocked. When the abdominal wound was opened, the shunt was found to be tracking back along the shunt track. The peritoneal end was removed and a new catheter was inserted via a new abdominal opening into the peritoneum. The patient recovered, and his symptoms resolved immediately. On reviewing the radiographs of the shunt retrospectively, they were found to show the backtracking of the shunt clearly (Fig. 2 upper). Radiographs of the shunt obtained 1 year previously had shown normal findings (Fig. 2 lower). Retrograde migration of a shunt in the same track is rare; one case of its occurrence in a 1-year-old patient has been previously reported. 1 In that case it was hypothesized to be due to a combination of excess catheter, a small peritoneal cavity, and an opening in the peritoneum that was not in a purse-string configuration around the catheter. The mechanism of the migration in our case remains unclear, but a lateral radiograph would have indicated clearly that the shunt catheter was extraperitoneal. 1

Effect of body habitus and parity on the initial Veres intraperitoneal CO 2 insufflation pressure during laparoscopic access in women

Study objectives Since most gynecologists use the Veres/trocar entry, and because the Veres intraperitoneal (VIP) pressure appears to be the most reliable indicator of correct Veres needle placement, the objective of this study was to determine the effect of height, weight, body mass index (BMI), parity, and age on the initial Veres intraperitoneal CO 2 insufflation pressure during laparoscopic access in women. Design Prospective observational cohort study (Canadian Task Force classification II-1). Setting University affiliated teaching hospital. Patients We prospectively collected data on 356 women undergoing laparoscopy for a variety of indications by the senior author (G.A.V.). The median and (range) for height, weight, BMI, parity, and age were 1.64 m (1.45–1.85 m), 65 kg (40–120 kg), 24.3 kg/m 2 (16–47 kg/m 2), 1 (0–5) and 34 years (18–87 yrs), respectively. Intervention Under general endotracheal anesthesia including muscle relaxants and with the patient in appropriate stirrups in the horizontal position, a nondisposable Veres needle was inserted at the umbilicus or left upper quadrant (Palmer’s point) with CO 2 flowing at 1 L/min. The initial Veres intraperitoneal insufflation pressure was recorded once the Veres needle was believed to be in the peritoneal cavity. Measurements and main results The mode and the median VIP pressure was 4 mm Hg with a range of 2 to 10 mm Hg. With multivariate analysis, the VIP pressure correlated positively with the weight (r = 0.518, p <.001) and BMI (r = 0.545, p <.001) and negatively with the parity (r = −0.179, p <.001) of women. The correlation of the VIP pressure with height and age was r = 0.029 (p = .591) and r = −0.044 (p = .411), respectively. Conclusion A VIP pressure ≤10 mm Hg indicates intraperitoneal placement of the Veres needle. The VIP pressure correlates positively with the weight and BMI and negatively with the parity of women. There is no correlation of the VIP pressure with women’s height and age.

Seprafilm Does Not Aggravate Intraperitoneal Septic Conditions or Evoke Systemic Inflammatory Response

To determine whether Seprafilm aggravates the systemic inflammatory response and adversely affects the outcome of postoperative intraperitoneal septic conditions. We retrospectively analyzed the relationship between the intraperitoneal placement of Seprafilm and the rate of intraperitoneal septic complications in 278 consecutive patients. Experimentally, 40 rats were subjected to laparotomy with or without the intraperitoneal placement of Seprafilm. Bacterial peritonitis was induced by cecal ligation and puncture (CLP) and the serum cytokine levels were measured. Seprafilm did not increase the rate of septic complications or aggravate inflammatory responses in patients with or without postoperative intraperitoneal inflammatory complications. Experimentally, there was no significant difference between the serum inflammatory cytokine levels after CLP with or without Seprafilm. Seprafilm did not adversely affect postoperative inflammatory response or clinical outcomes, even in patients with intraperitoneal septic complications.

Bladder augmentation in dogs using the tissue capsule formed around a perivesical tissue expander.

Enterocystoplasty provides needed improvement in bladder storage parameters in many patients but it also generates significant morbidity. We evaluated the unusual potential alternative of using the capsule that forms around a standard silicone tissue expander placed perivesically to augment the bladder in dogs. Six mongrel dogs underwent baseline videourodynamics and assessment of serum electrolytes, followed by placement of a 250 to 500 cc perivesical silicone tissue expander. Four months after implantation the tissue expander was removed and the fibrous capsule around the expander was biopsied. The capsule was opened and anastomosed to the bladder to augment storage. Serum electrolytes were determined 2 and 4 weeks after augmentation. Videourodynamics were repeated after 3 to 5 months, that is at sacrifice. The harvested bladders underwent histological evaluation. Five dogs underwent augmentation as described, while in an additional dog that underwent intraperitoneal placement of the tissue expander a fibrous capsule failed to form. Of the 5 augmented dogs 4 underwent repeat urodynamic and electrolyte evaluation with harvesting of the lower urinary tract, while 1 died of undetermined causes 3 weeks after augmentation. A distinct capsule formed in all dogs and augmentation was technically achievable. Anastomosis calcification in 3 dogs limited filling the augmenting capsule for cystography. Bladder capacity and compliance improved in all animals but it varied in degree. Histological examination of the capsule biopsies showed collagen rich connective tissue without epithelium or smooth muscle. After augmentation the capsular segment revealed urothelium in all cases with squamous metaplasia in 1. The subepithelial region had dense fibrosis and a thin band of osseous metaplasia occupied the lamina propria in all cases. Disorganized smooth muscle bundles were noted in all augmented bladders within the collagen of the capsule wall. Bladder augmentation with the collagenous capsule formed over a perivesical tissue expander is technically feasible. There was evidence of epithelial and smooth muscle ingrowth from the native bladder with improved bladder capacity and compliance in all dogs. Osseous metaplasia of the luminal surface of the collagen based capsule that developed in all animals may have been responsible for anastomotic narrowing and limited filling on cystography.

CHEMICALLY MODIFIED TETRACYCLINE PREVENTS THE DEVELOPMENT OF SEPTIC SHOCK AND ACUTE RESPIRATORY DISTRESS SYNDROME IN A CLINICALLY APPLICABLE PORCINE MODEL

Sepsis causes more than with 215,000 deaths per year in the United States alone. Death can be caused by multiple system organ failure, with the lung, in the form of the acute respiratory distress syndrome (ARDS), often being the first organ to fail. We developed a chronic porcine model of septic shock and ARDS and hypothesized that blocking the proteases neutrophil elastase (NE) and matrix metalloproteinases (MMP-2 and MMP-9) with the modified tetracycline, COL-3, would significantly improve morbidity in this model. Pigs were anesthetized and instrumented for hemodynamic monitoring and were then randomized to one of three groups: control (n = 3), laparotomy only; superior mesenteric artery occlusion (SMA) + fecal blood clot (FC; n = 7), with intraperitoneal placement of a FC; and SMA + FC + COL (n = 5), ingestion of COL-3 12 h before injury. Animals emerged from anesthesia and were monitored and treated with fluids and antibiotics in an animal intensive care unit continuously for 48 h. Serum and bronchoalveolar lavage fluid (BALF) were sampled and bacterial cultures, MMP-2, MMP-9, NE, and multiple cytokine concentrations were measured. Pigs were reanesthetized and placed on a ventilator when significant lung impairment occurred (PaO2/FiO2 < 250). At necropsy, lung water and histology were assessed. All animals in the SMA + FC group developed septic shock evidenced by a significant fall in arterial blood pressure that was not responsive to fluids. Lung injury typical of ARDS (i.e., a fall in lung compliance and PaO2/FiO2 ratio and a significant increase in lung water) developed in this group. Additionally, there was a significant increase in plasma IL-1 and IL-6 and in BALF IL-6, IL-8, IL-10, NE, and protein concentration in the SMA + FC group. COL-3 treatment prevented septic shock and ARDS and significantly decreased cytokine levels in plasma and BALF. COL-3 treatment also significantly reduced NE activity (P < 0.05) and reduced MMP-2 and MMP-9 activity in BALF by 64% and 34%, respectively, compared with the SMA + FC group. We conclude that prophylactic COL-3 prevented the development of ARDS and unexpectedly also prevented septic shock in a chronic insidious onset animal model of sepsis-induced ARDS. The mechanism of this protection is unclear, as COL-3 inhibited numerous inflammatory mediators. Nevertheless, COL-3 significantly reduced the morbidity in a clinically applicable animal model, demonstrating the possibility that COL-3 may be useful in reducing the morbidity associated with sepsis and ischemia/reperfusion injury in patients.

What happens to the rectus abdominus fascia after laparoscopic ventral hernia repair?

One criticism of laparoscopic ventral hernia repair (LVH) is that the rectus muscles are not re-approximated to the midline, and the effect of LVH repair on the fascial edges is unclear. Progressive migration of the fascial edges toward the midline has been observed anecdotally, but objective evidence remains limited. The purpose of this study is to observe the effect of LVH repair on the rectus abdominus fascia. Patients undergoing LVH repair with defects > 10 cm in horizontal diameter were identified prospectively and enrolled. All were repaired laparoscopically with intraperitoneal placement of mesh (DualMesh, W.L. Gore and Associates) using a standard approach. Radio-opaque clips were placed at the fascial edges intraoperatively to mark the defect, and plain abdominal films were taken postoperatively (Time 1) to establish the initial distance between clips (measured in cm). A subsequent follow-up film was taken (Time 2), and the difference in clip distance per patient was recorded. Results were analyzed using a chi-squared test. Twelve patients qualified for analysis and their results were compared. Mean fascial defect size was 15.1 cm (range 8.3-22.0). With respect to change in clip distance from Times 1 to 2, three events were observed: (1) Diminished (i.e. medialized), (2) Enlarged, or (3) No Change. Ten patients (83%) medialized, one patient enlarged, and one patient showed no change (chi2 (d.f. = 2) 9.17, p < 0.0023). Medialization of the rectus abdominus fascia occurs in the majority of patients undergoing LVH repair. Causes for this phenomenon are unclear: however eliminating intrabdominal pressure with intraperitoneal mesh placement likely plays a role.

Windows of opportunity for organogenesis

Growing new organs in situ by implanting developing animal organ anlagen/primordia represents a novel solution to the problem of limited supply for human donor organs that offers advantages relative to transplanting embryonic stem (ES) cells or xenotransplantation of developed organs. We and others have shown that renal anlagen transplanted into animal hosts undergo differentiation and growth, become vascularized by blood vessels of host origin, exhibit excretory function and support life in otherwise anephric hosts. Renal anlagen can be transplanted across both concordant (rat to mouse) and highly disparate (pig to rodent) xenogeneic barriers. Similarly, pancreatic anlagen can be transplanted across concordant and highly disparate barriers, and undergo growth, differentiation and secrete insulin in a physiological manner following intra-peritoneal placement. Successful transplantation of organ primordia depends on obtaining them at defined windows during embryonic development within which the risk of teratogenicity is eliminated, growth potential is maximized, and immunogenicity is reduced. Here we review studies that delineate such developmental windows of opportunity for kidney and pancreas.

Contrast-Enhanced MR Angiography After Pancreas Transplantation: Normal Appearance and Vascular Complications

ancreatic transplantation is increasingly used for the treatment of type 1 diabetes mellitus [1]. It commonly is performed in conjunction with kidney transplantation. The original procedure is the systemic bladder drainage type, which consists of intraperitoneal placement of the whole pancreas into the pelvis and anastomosis of the transplanted splenic and superior mesenteric arteries to the recipient’s iliac arteries via a Y-graft formed from the donor’s common, internal, and external iliac arteries. Pancreatic venous outflow with this type of graft is into the iliac veins and therefore the systemic circulation (Figs. 1 and 2). Drainage of the exocrine secretions is into the urinary bladder using an interposition duodenal segment. This technique has a number of drawbacks: namely, the development of peripheral hyperinsulinemia due to venous drainage of the insulin into the systemic circulation rather than the portal vein. This condition has been found to accelerate the development of insulin resistance and possibly atherosclerosis. In addition, urinary tract infections and graft pancreatitis occur as complications of the drainage of the exocrine secretions into the urinary bladder, necessitating conversion from bladder to enteric drainage in a substantial number of patients. These drawbacks led to the development of a modified form of pancreatic transplantation, commonly referred

THE DEVELOPMENT OF ACUTE RESPIRATORY DISTRESS SYNDROME AFTER GUT ISCHEMIA/REPERFUSION INJURY FOLLOWED BY FECAL PERITONITIS IN PIGS: A CLINICALLY RELEVANT MODEL

Numerous clinical trials using anti-inflammatory agents for patients with acute respiratory distress syndrome (ARDS) have failed despite efficacy in acute animal models. This underscores the necessity of developing a clinically relevant model of ARDS. Initially, we attempted to induce lung injury in pigs by fecal peritonitis only. When this was unsuccessful, we designed a two-hit model of ischemia/reperfusion (I/R) injury followed by fecal peritonitis to create a clinically applicable model of ARDS. The initial study consisted of Yorkshire swine [group 1, fecal clot (FC), n = 4] that were followed clinically after intraperitoneal placement of a fecal (0.5 mL/kg) blood (2 mL/kg) clot. Blood was sampled daily for cultures, a complete blood count, a lactate level, and various cytokine expression determined by enzyme-linked immunosorbent assay (ELISA). Pigs were treated with antibiotics and fluids, placed on a ventilator before sacrifice to obtain hemodynamic and pulmonary parameters, and underwent histologic lung assessment. Additionally, bronchoalveolar lavage fluid was obtained for protein concentration and cytokine levels. Once it was evident that no lung injury had occurred, we designed a more severe model. A second group of Yorkshire swine [group 2, superior mesenteric artery (SMA) + FC, n = 4] underwent SMA occlusion for 30 min (I/R) followed by intraperitoneal placement of a FC as in the initial group. These pigs were monitored more invasively and continuously in an intensive care setting for 48 h and followed, treated, and assessed in a similar fashion to group 1. Group 1 (FC) pigs survived 9 days and showed signs of sepsis (bacteremia with polymicrobial organisms), an inflammatory response in the form of elevated cytokines, yet no physiologic or histologic evidence of lung injury. Group 2 (SMA + FC) pigs demonstrated more severe sepsis, a significantly increased cytokine response compared with animals in the FC group, and physiologic signs of progressive pulmonary injury. Pigs in the SMA + FC group were sacrificed at 48 h after clinical deterioration (significant decline in oxygenation) and demonstrated pathologic evidence of lung injury indicated by increased bronchoalveolar lavage fluid protein, diffuse and thickened alveolar septae, hyaline membrane formation, and pulmonary edema. The addition of a second "hit" (SMA occlusion, I/R) to a FC sepsis model resulted in severe lung injury that developed within a 3-day period. To our knowledge, this is the first large animal experiment that definitively and consistently causes insidious onset ARDS in pigs. By closely paralleling the clinical development of pulmonary injury, this model should prove invaluable in the study of human ARDS.

Traitement des éventrations de la paroi abdominale

Incisional hernias occur in about 13 to 20 % of patients undergoing abdominal surgical procedures. They entail a large financial burden with high cumulative rate of reoperative repairs. Development of minimally invasive surgery got rid of occurrence of large hernias but might induce a new concept, the limited port-site hernias. Anatomical reconstitution with closure of linea alba by suture or autoplasty has been shown to have a high recurrence rate. Tension free obturation of the defect with a prosthetic mesh is becoming the procedure of choice for any hernia whatever the size. The recurrence rate has been reduced to less than 10 %. Non absorbable synthetic biomaterials are widely used. Macroporous meshes (polypropylene, polyester) have a high adhesion rate unsuitable for direct contact with the bowel as opposed to microporous one (e PTFE). Newer composite biomaterials with an anti-adhesive inner surface are available for intraperitoneal placement. Current sites of mesh implantation are intraperitoneal, preperitoneal, retro muscular-prefascial, pre muscular-prefascial. Mesh reinforcement is also indicated for repair of muscle-splitting transverse or sub-costal hernias. In case of emergency laparotomy for intestinal obstruction or planned surgical procedure in patient presenting with incisional hernia, synchronous repair with mesh is mandatory. Non absorbable mesh can be used in the presence of open bowel. In a grossly contaminated field, absorbable mesh is advisable. The most commonly reported complication is seroma formation which generally resolved spontaneously. Infection is the second most common complication. Incidence, treatment and outcome depend on the nature of the biomaterial. In case of repeated repair for recurrence, a procedure different from that previously used with a prosthetic reinforcement must be performed. Laparoscopic approach to incisional hernia includes intraperitoneal placement of a composite biomaterial overlapping the margins of the defect without any attempt of anatomical reconstitution, nor resection of the hernia sac. Mesh is secured with a combination of non absorbable sutures through the abdominal wall and laparoscopically placed staples. The benefits are a decrease in surgical morbidity and hospital stay. Recurrence rate is reported to be equal or less than in the open repair. Drawbacks are a longer operative time, frequent difficulties of performing adhesiolysis with risk of bowel injuries and persistance of cutaneous changes. Laparoscopic approach is mainly indicated for small sized hernias with a reductible content.

Adhérences viscérales après cure d’éventration par plaque intrapéritonéale : étude monocentrique comparant un renfort conventionnel (Mersilène ®) à un renfort composite (Parietex ®)

Aim of the study. – Intraperitoneal (IP) ventral hernia repair is advantageous because of reduced dissection, shorter operative time and less postoperative pain. However, the IP positioning of the mesh is suspected to increase the risk of visceral adhesion and induce complications. To overcome these drawbacks, an innovative mesh: Parietex ® Composite (RC) was developed with one side protected by a hydrophilic resorbable film. The purpose of this study was to compare using ultrasonography the rate of visceral adhesions after IP placement of a conventional mesh (RP) versus RC mesh. Patients and methods. – Twenty-six patients who received a Parietex ® Composite were prospectively compared to a retrospective series of 26 consecutive asymptomatic patients who received a non protected polyester mesh (RP). In order to objectively assess visceral adhesion toward the abdominal wall, an ultrasound specific examination was used after previous validation by comparison of preoperative ultrasonographic data with peroperative gross appearance in both groups. Results. – With a mean follow up of 33 months, both groups were equivalent in term of inclusion criteria excepted for age which was older the RP group. US validation data were: sensitivity 72%, accuracy 69%, negative predictive value 67%. Using this procedure, 81% of the patients exhibit visceral adhesion to the mesh in the RP group, versus 27% in the PC group ( P =0.0002, χ2). Conclusion. – US examination represents a suitable tool to evaluate postoperative adhesions to the abdominal wall. A significant reduction of visceral adhesion in the RC group was shown.

Transplantation of embryonic organs - kidney and pancreas

One novel solution to the shortage of human organs available for transplantation envisions 'growing' new organs in situ via xenotransplantation of developing anlagen from animal embryos. We and others have shown that renal anlagen (metanephroi) transplanted into animal hosts undergo differentiation and growth, become vascularized by blood vessels of host origin and exhibit excretory function. Metanephroi can be stored for up to 3 days in vitro prior to transplantation with no impairment in growth or function post-implantation. Metanephroi can be transplanted across both concordant (rat to mouse) and highly disparate (pig to rodent) xenogeneic barriers. Similarly, pancreatic anlagen undergo growth, differentiation and secrete insulin in a physiological manner following intraperitoneal placement. Implantation of the embryonic pancreas, is followed by selective differentiation of islet as compared to acinar components. Here we review studies exploring the potential therapeutic use of embryonic kidney or pancreas transplantation.

Intraperitoneal placement of a microdialysis catheter in patients with gastrointestinal anastomosis: preliminary results of a prospective study

Intraperitoneal placement of a microdialysis catheter in patients with gastrointestinal anastomosis: preliminary results of a prospective study

Effect of prosthetic material on adhesion formation after laparoscopic ventral hernia repair in a porcine model.

Intraperitoneal placement of prosthetic mesh causes adhesion formation after laparoscopic incisional hernia repair. A prosthesis that prevents or reduces adhesion formation is desirable. In this study, 21 pigs were randomized to receive laparoscopic placement of plain polypropylene mesh (PPM), expanded polytetrafluoroethylene (ePTFE), or polypropylene coated on one side with a bioresorbable adhesion barrier (PPM/HA/CMC). The animals were sacrificed after 28 days and evaluated for adhesion formation. Mean area of adhesion formation was 14% (SD+/-15) in the PPM/HA/CMC group, 40% (SD+/-17) in the PPM group, and 41% (SD+/-39) in the ePTFE group. The difference between PPM/HA/CMC and PPM was significant ( P=0.013). A new visceral layer of mesothelium was present in seven out of seven PPM/HA/CMC cases, six out of seven PPM cases, and two out of seven ePTFE cases. Thus, laparoscopic placement of PPM/HA/CMC reduces adhesion formation compared to other mesh types used for laparoscopic ventral hernia repairs.

Assessment of adhesion formation to intra-abdominal polypropylene mesh and polytetrafluoroethylene mesh

BackgroundThe development of intra-abdominal adhesions, bowel obstruction, and enterocutaneous fistulas are potentially severe complications related to the intraperitoneal placement of prosthetic biomaterials. The purpose of this study was to determine the natural history of adhesion formation to polypropylene mesh and two types of polytetrafluoroethylene (ePTFE) mesh when placed intraperitoneally in a rabbit model that simulates laparoscopic ventral hernia repair. Materials and methodsThirty New Zealand white rabbits were used for this study. A 10-cm midline incision was performed for intra-abdominal access and a 2 cm x 2 cm piece of mesh (n = 60) was sewn to an intact peritoneum on each side of the midline. Two types of ePTFE mesh (Dual Mesh and modified Dual Mesh, W.L. Gore & Assoc., Flagstaff, AZ) and polypropylene mesh were compared. The rate of adhesion formation was evaluated by direct visualization using microlaparoscopy (2-mm endoscope/trocar) at 7 days, 3 weeks, 9 weeks, and 16 weeks after mesh implantation. Adhesions to the prosthetic mesh were scored for extent (%) using the Modified Diamond Scale (0 = 0%, 1 ≤ 25%, 2 = 25–50%, 3 > 50%). At necropsy the mesh was excised en bloc with the anterior abdominal wall for histological evaluation of mesothelial layer growth. ResultsThe mean adhesion score for the polypropylene mesh was significantly greater (P < 0.05) than Dual Mesh at 9 weeks and 16 weeks and modified Dual Mesh at 7 days, 9 weeks, and 16 weeks. Fifty-five percent (n = 11) of the polypropylene mesh had adhesions to small intestine or omentum at necropsy compared to 30% (n = 6) of the Dual Mesh and 20% (n = 4) of the modified Dual Mesh. There was a significantly greater percentage (P < 0.003) of ePTFE mesh mesothelialized at explant (modified Dual Mesh 44.2%; Dual Mesh 55.8%) compared to the polypropylene mesh (12.9%). ConclusionsSerial microlaparoscopic evaluation of intraperitoneally implanted polypropylene mesh and ePTFE mesh in a rabbit model revealed a progression of adhesions to polypropylene mesh over a 16 week period. The pore size of mesh is critical in the development and maintenance of abdominal adhesions and tissue ingrowth. The macroporous polypropylene mesh promoted adhesion formation, while the microporous nature of the visceral side of the ePTFE served as a barrier to adhesions.

Intraperitoneal transplantation of pancreatic anlagen.

To determine whether embryonic pancreatic anlagen transplanted to an intraperitoneal site in adult hosts grow, differentiate, and function, we implanted pancreas from embryonic day (E) 12.5 Lewis rat embryos into the omentum of adult Lewis rats or C57Bl/6J mice. E12.5 pancreatic anlagen were relatively undifferentiated except for the presence of condensing tubuloacinar cords. By 2 weeks after implantation, pancreatic anlagen transplanted into rats had enlarged and differentiated such that islets of Langerhans that stained positive for insulin could be delineated. Continued differentiation, as reflected by the presence of "ductal" islets connected to the duct epithelium, was observed at 6 weeks after implantation. At 15 weeks after implantation, "mature" islets had separated from the ducts. Electron microscopy showed eccentric dense bodies within clear vacuoles consistent with insulin granules. Little or no acinar tissue was present in developed anlagen. Within 5 weeks of pancreatic anlagen transplantation, levels of glucose in rats rendered diabetic by an injection of streptozotocin were normalized compared with levels in nontransplanted diabetic controls. Rat pancreatic anlagen underwent growth and development in the peritoneum of C57Bl/61 mice that received costimulatory blocking agents but not in the absence of costimulatory blockade. We concluded that whole E12.5 pancreatic anlagen undergo growth, differentiation, and function after intraperitoneal placement. Implantation of the embryonic pancreas, a "cellular" transplant, is followed by selective differentiation of islet compared with acinar components.

Editorial: Management of umbilical hernia in patients with advanced liver disease

The tendency for patients with severe liver disease to develop an umbilical hernia has been known for some time.1,2 The denominator is hard to determine, but review of patients referred for consideration of liver transplantation shows that approximately 20% have an umbilical hernia.3 Unlike the general population, in which female sex and obesity are risk factors for umbilical hernia, patients with liver disease who form umbilical hernias are more likely to be men with muscle wasting and ascites. Although the sex difference probably reflects the incidence of cirrhosis, men with liver disease are more likely to develop hernia at the umbilicus than the inguinal canal, unlike the general population, in which the opposite is true. The reason for this is not clear because the contributory factors, abdominal distension and abdominal wall weakness, are as likely to promote an inguinal hernia as an umbilical hernia. A personal hypothesis is that portosystemic venous communication at the umbilicus transmits the additional pressure required to favor herniation to the umbilicus rather than the groin. An umbilical hernia often is accompanied by marked thrombocytopenia, even before ascites is evident. If true, it has important implications in planning the repair of an umbilical hernia in cirrhotic patients. Traditional repairs made before transplantation usually fail. Although ascites and muscle wasting are thought to contribute to the development of umbilical hernias, one third of patients will present with an umbilical hernia before the diagnosis of liver disease.2,3 In a review by the author’s group,3 several patients underwent three or four repairs before referral for transplantation. The skin over a large hernia thins and becomes prone to necrosis. Spontaneous leakage of ascites, bleeding from umbilical varices, and bacterial or fungal peritonitis may ensue. Umbilical hernias rarely incarcerate in the presence of ascites. Conversely, successful treatment of ascites may become a prelude to incarceration.3,4 The best time for umbilical hernia repair has not been considered in the literature; however, control of ascites is believed to be essential to success.1,5,6 Taking these factors into consideration, an algorithm for the management of umbilical hernias in patients with severe liver disease is suggested (Fig. 1). Liver transplantation candidates with an uncomplicated umbilical hernia usually postpone repair until transplantation unless there is rapid resolution of ascites. Urgent repair of a complicated hernia requires a strategy to control ascites, if present. Ultra–low-salt diet, diuretics, abdominal drainage, transjugular intrahepatic portosystemic shunt, and peritoneovenous shunt have each been used.1,5,6 The high rate of recurrence of umbilical hernias in cirrhotic patients is from the era of suture repair. A trial of prosthetic mesh repair in the general population shows a lower hernia recurrence rate, but a greater wound complication rate, than suture repair.7 The latter problem may be addressed using the laparoscopic approach.8 In this issue of Liver Transplantation, Sarit, Eliezer, and Mizrahi describe laparoscopic reduction of an incarcerated bowel and placement of a mesh prosthesis to repair a recurrent hernia in a patient with cirrhosis.9 Certain risks specific to cirrhotic patients inherent in this surgical approach were not encountered. Trocar placement in the left subcostal region must be careful to avoid an enlarged spleen. Reduction of incarcerated hernia contents may be hampered by the proximity and adherence of umbilical varices. This also will make it hazardous to dissect the hernia sac and create a preperitoneal space for the mesh. Intraperitoneal placement of mesh will be prone to displacement by ascites or the formation of adhesions to intestine. Multiple trocar sites increase the potential for an ascitic leak. The surgical strategy should account for these risks. A preoperative duplex ultrasound examination will confirm the position of the spleen, determine if there is flow in the umbilical vein, and, possibly, outline the

Laparoscopic ventral hernia repair with extraperitoneal mesh: surgical technique and early results.

Laparoscopic repair of ventral abdominal wall hernias involves intraperitoneal placement of a mesh, which may lead to adhesion formation and bowel fistulation. The first series of selected patients with ventral abdominal wall hernias treated laparoscopically by extraperitoneal placement of a polypropylene mesh is presented. Thirty-four patients (24 women and 10 men; median age, 52 years [range, 34-70]) were selected from among 122 patients undergoing laparoscopic ventral hernia repair. Of these patients, 18 had a primary ventral abdominal wall hernia and 16 had an incisional hernia. After reduction of sac contents and adhesiolysis intraperitoneally, a large flap of peritoneum (with extraperitoneal fat, fascia, and posterior rectus sheath where present) was raised to accommodate a suitably sized polypropylene mesh, which was then covered again with the peritoneal flap at the end of the procedure. Intraoperatively, apart from circumcision of the hernial sac at the neck, a total of 24 iatrogenic peritoneal tears occurred in 20 patients, mainly at the site of the previous scar. In two patients, it was observed that greater than 25% of the mesh was exposed after the procedure. The median (+/-SD) duration of hospitalization postoperatively was 1 day (+/-0.56). One patient's hernia recurred 4 months after surgery, and one patient's infected mesh was removed 8 months after surgery. Laparoscopic extraperitoneal placement of a mesh is feasible and appears to be an advance over laparoscopic intraperitoneal mesh placement for ventral abdominal wall hernias in selected patients. However, longer follow-up and controlled clinical trials will be necessary before any firm conclusions can be drawn.

Serious abdominal complications of intra-peritoneal placement of left ventricular assist devices

Serious abdominal complications of intra-peritoneal placement of left ventricular assist devices