Creation of the isolated bowel segment in animals by omentoenteropexy

Creation of a Continent Urinary Bladder Reservoir Vascularized by Omentum as a Possible Surgical Option for Canine Trigonal/Urethral Urothelial Carcinoma

Surgical procedures that maintain continence with minimal complication following resection of trigono-urethral urothelial carcinoma (UC) are limited in canines; therefore, palliative options are often pursued. A feasible tumor resection option may improve disease control and survival. The study's objective was to evaluate a continent urine reservoir created from the urinary bladder body and vascularized solely by omentum. We hypothesized that a viable urine reservoir could be created, and staged omentalization would provide improved vascularity. Nine normal female Beagles were randomized to one of three groups. Group A urinary bladders were transected cranial to the ureteral papillae to create a closed bladder vesicle which was concomitantly omentalized. Group B underwent omentalization two weeks prior to vesicle creation. Based on Group A and B results, Group C underwent neoureterocystostomy and omentalization followed by neoreservoir formation and tube cystostomy 2 weeks later. Serial ultrasounds and histopathology confirmed adequate omental neovascularization in Groups B and C with continent Group C neoreservoirs maintained for 2 months. Some pylectasia and ureteral dilation was documented in all Group C dogs at variable timepoints. Progressive hydroureteronephrosis developed in 2/6 kidneys. Transient azotemia was noted in only 1 Group C dog, although all developed treatable urinary tract infections. The sample size is limited, and the efficacy of this technique in providing disease control for UC is unknown. However, this novel option could allow for primary UC resection while providing continence and limiting complications. Postoperative local or systemic adjuvant therapy, ultrasonographic neoreservoir monitoring, and BRAF analysis would be indicated.

A morphometric study of the intestinal mucosa of rats submitted to omentoenteropexy

CONTEXT: The omentoenteropexy technique was developed as an alternative method for intestinal neovascularization, due to the angiogenic properties of factors from the omentum. OBJECTIVES: This study investigated changes in intestinal villi heights and crypts depths due to surgical techniques: seromiotomy with and without omentoenteropexy. METHOD: Thirty rats were operated on, after being divided into three groups, namely GI, GII and GIII with 10 rats each. In the GI rats were submitted to omentoenteropexy; rats in GII were submitted only to a seromiotomy, and in the GIII only laparotomy. Sixty days after the first surgery, the animals were sacrificed and a segment of intestine was removed for histology using Masson's trichrome technique and morphometric study of intestinal mucosa. RESULTS: The histological findings showed that seromiotomy with or without omentoenteropexy increased the length of intestinal villi when compared with GIII (only laparotomy) (analysis of variance: P = 0.0068; GI 38.88 ± 4.17; GII 39.41± 6.33; GIII 31.85 ± 5.56; GI = GII P>0.05; GII>GIII P<0.05; GI>GIII P<0.001). CONCLUSION: No differences were demonstrated in relation to crypt depths between the groups (P = 0.60). Ongoing studies are being set forth by our group to add more data on the role of omentopexy as a tool to promote neovascularization and intestinal mucosal growth.

Omentopexy improves vascularization and decreases stricture formation of esophageal anastomoses in a dog model

BACKGROUND

Anastomotic strictures are common after primary esophageal anastomosis in pediatric patients. Recent studies provided evidence that omentopexy may improve vascularization of gastroesophageal anastomoses and decrease the rate of stricture-related complications. The effect of omentopexy on primary esophago-esophageal anastomosis, however, is unknown. The aim of the current study was to examine the role of omentopexy on the healing process of primary midesopageal anastomoses.

METHODS

Six dogs were operated on. A 5-cm portion of the midesophagus was resected, and continuity was restored by end-to-end anastomosis. In 3 dogs, an omental pedicle was placed around the anastomotic region. Eating patterns were recorded and functional swallowing was evaluated by fluoroscopic studies. Eight weeks after the operations, the experimental animals were killed and anastomotic lumen diameters and vascularization of the anastomotic sites were evaluated by radiographic studies and histologic examination, respectively.

RESULTS

Two dogs in the omentopexy group were able to resume regular feeding, whereas none of the dogs in the control group were able to tolerate solid food intake. Fluoroscopic studies found preserved motility patterns of the esophagus in the omentoesophagopexy group, while prestenotic dilatation and delayed food clearance through the anastomosis were observed in the control group. Histologically, neovascularization was observed at the anastomotic site in the omentoesophagopexy group in contrast to the marked degree of fibrosis displayed in the control group.

CONCLUSIONS

Omentopexy may improve vascularization and decrease stricture formation after primary esophagoesophageal anastomosis.

Are there any structural alterations in a neovascularized jejunal segment by omentoenteropexy? A histologic and immunohistochemistry study

BACKGROUND/PURPOSE

Although the bowel neovascularization by omentoenteropexy seems to be a good alternative to bowel lengthening, there were no rigorous analyses about its histologic structure and intrinsic innervation. The aim of this study was a histologic and immunohistochemical analysis of a neovascularized jejune segment (NJS) by omentoenteropexy.

METHODS

An NJS was done by omentoenteropexy in 13 Wistar rats. Seven weeks afterward, the mesentery of the NJS was ligated and divided. The NJS was separated from the normal jejunum by proximal and distal complete sections. End-to-end anatomosis was done between NJS and normal jejunum to restore bowel continuity. Twenty-six rats were sham operated. At 10 weeks, specimens were taken, and H&E, S-100 protein, and neuron-specific enolase staining were done. The muscle layer thickness, mucosae layer, and myenteric plexus were analyzed. The statistical tests were the Mann-Whitney test, Friedman's test, and Spearman's correlation.

RESULTS

There was a significant increase in NJS diameter. The muscle layers and mucosa were greater in the study group. The average number of neurons per intestinal ganglion was significantly fewer in the NJS.

CONCLUSIONS

Omentoenteropexy provoked an increase in the diameter of NJS and contributed toward a reduction of the number of neurons in the myenteric plexus of NJS.

Viability of a jejunal segment after neovascularization by omentoenteropexy

Omentoenteropexy was developed as an alternative technique to promote neovascularization in an isolated bowel segment. OBJECTIVE: The aim of the present protocol was to study the long-term viability of an isolated jejunal segment following neovascularization by omentoenteropexy. Long-term survival of a neovascularized bowel segment is an indication that the utilization of this segment as an intestinal graft can be successful. METHODS: To test the proposed surgical technique, 13 Wistar rats were subjected to laparotomy, the jejunum was exposed at 20 cm from the angle of Treitz and a pedicle of greater omentum was isolated. An incision of 6 cm was made along the antimesenteric jejunal border, exposing the submucosa. Omentoenteropexy was performed between the incision of the jejunum and the pedicle of the greater omentum. After seven weeks, the mesentery of the jejunal segment subjected to omentoenteropexy was ligated and isolated from the rest of the jejunum by a complete proximal and distal transversal section. Subsequently, an end-to-end anastomosis was performed to restore the continuity of the bowel. RESULTS: At 10 weeks from the first surgical intervention, the isolated jejunal segment subjected to omentoenteropexy was completely neovascularized and viable. CONCLUSION: No evidence of anatomical or functional intestinal obstruction was observed.

Preservation of a digital osteotendinous structure with an omental flap

Taking into account the angiogenic properties of the omentum to revascularize ischemic tissues, this experimental, longitudinal, prospective, double-blind study in rabbits was designed to revascularize and preserve the mobility of a digital osteotendinous structure surgically devascularized in advance and to compare such omental angiogenic ability with that of the muscle and the panniculus carnosus. Thirty New Zealand rabbits were used. Three toes from the hind feet were surgically amputated from each rabbit. The skin was removed, exposing the bones, tendons, ligaments, and joints, to form what we termed the osteotendinous structure. Through a median laparotomy, the first part of each rabbit's own osteotendinous structure was placed inside the panniculus carnosus (group I), the second under the rectus abdominis muscle (group II), and the third was wrapped in a pediculate omental flap (group III). Three weeks later, each structure was assessed clinically for mobility and fibrosis and microscopically for fibrosis, newly formed vessels, viability, and tissue regeneration. Clinically, the group I structures showed a greater amount of fibrosis. The structures in groups II and III showed minimal fibrosis in all but four cases, which showed moderate fibrosis. Differences in joint mobility were assessed with the Kruskal-Wallis test. There was a statistically significant difference in mobility for the structures from group III, which was higher, followed by those from groups II and I. The exception was the proximal interphalangeal joints in groups II and III, for which the differences had no statistical significance. Microscopically, fibrosis and tissue necrosis were intense in the structures in group I, moderate in the group II structures, and mild in the group III structures. Conversely, vessel neoformation and tissue regeneration were intense in the structures in group III, moderate in group II, and were nil in group I. This study confirms with statistical significance that, in the rabbit, the omentum has a higher ability to revascularize degloved tissues than do the muscle and the panniculus carnosus, thus preserving a higher joint and tendon mobility. Consequently, it is suggested that a free omental flap be used in the treatment of ring avulsion injuries that lead to degloving of the digits.

Functional innervation of the isolated bowel segment

PURPOSE

The aim of this study is to investigate whether there might be an eventual change in the enteric nerve responses to electrical field stimulation (EFS) of the isolated bowel segment (IBS) created by omentoenteropexy.

METHODS

In the experimental group, an IBS was created in 10 rats using the omentum as the host organ by dividing of its mesentery 4 weeks later. In the control group, a jejunal loop of identical site and length to the IBS was studied in another 10 rats as normal jejunal segment. Longitudinal muscle strips were prepared from the IBSs (n 20) and the normal jejunal segments (n = 20). The effects of atropine, tetrodotoxin, L-arginine, and L-nitroarginine methyl ester (L-NAME) on the responses to transmural EFS were examined in both the IBS and normal jejunal segment using the isometric tension recording technique.

RESULTS

Transmural EFS of the IBS strips produced contractile responses. Atropine and tetrodotoxin abolished the EFS-induced contractions of the IBS. Moreover, EFS-induced contractions were increased by the application of L-NAME, and were decreased by the application of L-arginine in the IBS. Mean percent change of IBS's contraction was not found statistically different from mean percent change of normal jejunal segment's contraction on the effects of L-NAME and L-arginine.

CONCLUSION

These results suggest that the IBS, created by omentoenteropexy, produced enteric nerve responses to EFS as seen as in normal jejunal segment.

Isolated bowel segment created by omentoenteropexy: histologic findings

An isolated bowel segment (IBS) is a viable loop of bowel that is completely free of its mesenteric attachments. In this study, omentoenteropexy (OEP) was performed in 5-cm-long IBS of rats in order to provide neovascularization. Thirty-two rats were divided into four groups. After OEP, mesenteric division of the IBSs was performed at successive 1 week intervals in each group (3-6 weeks). The bowel-wall structures were histologically examined 2 days after division of the mesentery. Ischemic changes were observed in the group in which the interval was shorter than 4 weeks. In the IBSs that were supplied by the pediculated omental flap for 4 or more weeks no ischemic changes were noted in the mucosa, muscle layers, or intramural ganglia. We conclude that an IBS that preserves normal bowel structures can safely be created in the rat when its mesentery is divided 4 weeks after OEP. Physiological studies of motility and absorption can be performed and longitudinal tubularization may enable such an IBS to be used in short-bowel syndrome.

Testicular neovascularization by "omentotesticulopexy': a possible adjuvant in the surgical correction of high undescended testes

The surgical repair of "very high" undescended testes may bring about testicular atrophy, as a result of impaired vascular supply, whether caused unintentionally by extensive dissection, or deliberately when the Fowler-Stephens operation is employed. In this experimental study, improvement of the vascular supply by means of "omentotesticulopexy" (an omental flap pexied to the rat testis) before or concomitant with spermatic vessel division (known as the Fowler-Stephens operation) was achieved and demonstrated by angiographic studies. The authors believe that the addition of "omentotesticulopexy" to the Fowler-Stephens operation will reduce the rate of testicular atrophy among patients with high undescended testes.

Preserved viability of the isolated bowel segment, created by omentoenteropexy: a histological observation

Creation of the isolated bowel segment (IBS) by omentoenteropexy in rats and dogs consists of a two-step procedure: initial omentoenteropexy to the antimesenteric border of a jejunal segment, and division of its mesentery 6 weeks later. Viability of this IBS is maintained by the angiogenic process, which occurs at the level of the myoenteropexy. Histological studies were performed by light microscopy on the bowel wall structures of the IBS before and after the mesenteric division, as well as after a lengthening procedure performed on the IBS in one dog. The authors conclude that (1) in rats and dogs the intestinal wall structures of all IBS variants created by omentoenteropexy appear close to normal, and (2) neovascularization can be clearly detected at the level of the omentoenteropexy.

Jejunal mucosal function of the isolated bowel segment created by omentoenteropexy in dogs: a study by in situ luminal perfusion

An isolated bowel segment (IBS) was created in dogs by omentoenteropexy, using staged procedures. (1) Omentoenteropexy was performed at the antimesenteric border of a 15-cm jejunal segment, which was exteriorized at both ends (IBSB). (2) After 6 weeks, once dual vascularization to the IBS had been established, its mesentery was divided (IBSA) or longitudinally split, thus achieving its elongation (IBSE). A control dog underwent a Thiry-Vella (T-V) loop procedure of an identical jejunal segment. Viability of the IBSB and IBSA was previously proven by the authors, through angiographic studies. In the present study, the absorption capability of IBS variants was assessed using in situ luminal perfusion, with a bicarbonate buffer containing glucose and labeled glycine. Jejunal transport rates of these solutes were calculated from the differences in their concentrations in the perfusion solution and in the effluent. Comparisons were made among the IBS variants and between them and the T-V loop. No significant difference in the absorption capability of glucose and glycine was noted between the various IBS variants. There was a marked reduction of glucose absorption and a moderate reduction of glycine absorption in all IBS variants. when compared with the fresh T-V loop, most probably because of disuse atrophy of the mucosa. In conclusion, absorption of glucose and glycine is preserved in the IBS, created by omentoenteropexy, both after its mesenteric division and following the IBS elongating procedure.