Evaluation of the biofragmentable anastomotic ring following preoperative irradiation to the rectosigmoid in dogs

Compression anastomoses in colorectal surgery: a review

The main serious risks of anastomotic construction in the colon and rectum include dehiscence and stricture formation. There is a resurgence of interest in sutureless anastomoses formed by compression elements since the introduction of shape memory alloy (SMA) systems, which evoke minimal early inflammatory response whilst maintaining anastomotic integrity. Currently, the most commonly used SMA is the nickel-titanium (NiTi) alloy that is highly biocompatible, returning to its pre-deformed stable (austenite) shape under different mechanical and thermal loads for use in humans. Pre-clinical data for shape memory alloy systems in colorectal anastomoses are limited, but it appears to be safe in porcine and canine models with limited leakage and reduced stricture formation. There does not appear to be any difference in tissue biochemistry of inflammatory markers when compared with conventional stapled techniques, although the few studies available show a markedly reduced early inflammatory response at the anastomotic site with the NiTi device. The majority of the clinical data concerning compression anastomoses are derived from the biofragmentable anastomotic ring device. This device has fallen out of use because of reported leaks, instrumental failure and problems with device expulsion. A novel SMA device, the NiTi anastomotic ring, permits construction of a low rectal anastomosis construction during open or laparoscopic procedures. The preliminary data demonstrate a safety comparable to conventional staple technology. This device also provides the potential of benefit of reduced anastomotic inflammation, because the compression ring results in direct serosa-to-serosa (or alternatively serosa-to-muscularis propria) apposition without the persistence of residual foreign material. This type of construction could lead to a reduced incidence of early anastomotic leakage and/or the development of anastomotic stenosis. Randomized clinical trials employing a NiTi arm for elective, emergency and high-risk colorectal anastomoses are required to determine its indications and clinical profile as well as to assess whether such technology may selectively obviate the need for proximal diversion in low colorectal anastomoses.

Estudo comparativo de anastomoses colorretais com anel biofragmentável e com grampeador em cães submetidos à irradiação gama pré-operatória

OBJETIVO: Comparar os resultados precoces entre anastomoses colorretais realizadas com anel biofragmentável e com grampeador circular após irradiação pélvica. MÉTODOS: Foram utilizados 40 cães beagle, em dois grupos de 20 animais, submetidos ou não à irradiação gama pré-operatória, com dose única de 500 cGy. Cada grupo foi dividido em dois subgrupos de dez animais, sendo denominado A o grupo em que se utilizou o anel biofragmentável e B aquele em que se empregou o grampeador. Os animais foram submetidos à secção completa do intestino grosso ao nível da junção retossigmóide, com reconstrução do trânsito sendo efetuada por uma das técnicas, após sorteio. Os animais foram sacrificados no sétimo dia de período pós-operatório. RESULTADOS: Houve dois óbitos antes da reoperação: um em animal do grupo teste, por ruptura da anastomose realizada com anel biofragmentável; outro por peritonite generalizada em animal do grupo controle com anastomose efetuada por grampeador. Aderências e infecções de parede ocorreram de forma similar. A análise histológica convencional e a análise morfométrica realizada por computador das áreas de cicatrização anastomótica identificaram comportamento análogo entre os grupos e subgrupos estudados. CONCLUSÃO: Os resultados precoces das técnicas empregadas para anastomose intestinal foram semelhantes nas condições de risco estudadas.

Conformal preoperative endorectal brachytherapy treatment for locally advanced rectal cancer: early results of a phase I/II study

PURPOSE

Downstaging rectal carcinoma by preoperative radiotherapy decreases local recurrence, and recent phase II studies suggest that, in the lower one-third lesions, sphincter-preserving surgery can be considered. The purpose of the current study was to assess the efficacy and the toxicity of endorectal high dose-rate brachytherapy as a preoperative downstaging treatment modality.

METHODS

Patients with newly diagnosed invasive rectal adenocarcinoma, T2 to very early T4, operable tumors were eligible. A dose of 26 Gy was given over four consecutive daily treatments of 6.5 Gy prescribed at the tumor radial margin using endorectal brachytherapy with high dose-rate delivery system. Surgery as planned initially was done four to eight weeks later to allow for tumor downstaging. Patients found to have pathologic positive nodes received postoperative external beam (45 Gy/25 fractions) to the pelvis and systemic 5-fluorouracil-leucovorin chemotherapy.

RESULTS

Forty-nine patients entered the study. Tumors were in the lower one-third in 24 patients, middle one-third in 22, and upper one-third in 3. With preoperative endorectal ultrasound and magnetic resonance imaging, the clinical staging of the tumors was: 3 T2, 42 T3, 4 T4, and 16 N1-2. Acute toxicity related to brachytherapy was limited to a moderate proctitis (Radiation Therapy Oncology Group acute toxicity scoring system, Grade 2) in all patients, with two patients with tumors extending into the anal canal having Grade 3 dermatitis. Forty-seven patients underwent surgery. Two patients refused their operation based on a normal endoscopic rectal ultrasound after treatment. A complete clinical response was obtained in 32 of 47 (68 percent) patients with 32 percent pathologically pT0N0-1, and 36 percent had only residual microfoci of carcinoma. The surgical approaches did not yield more complications than expected.

CONCLUSION

Preoperative high dose-rate endorectal brachytherapy seems to be safe, because acute toxicity was mainly local, with moderate proctitis (Grade 2) and occasional dermatitis (Grade 3) for very low tumors. Finally, this modality, by providing high rate of tumor downstaging and downsizing especially for patients with lesions in the lower one-third of the rectum, represents a definite potential for sphincter-preserving surgery for investigation in future studies.

High-dose preoperative radiotherapy does not alter the strength of unilaterally irradiated colon anastomoses in rats

PURPOSE

We studied the influence of preoperative radiotherapy on the strength of colon anastomoses in rats. We compared a conventional (2 Gy/fraction; 1 fraction/day; 5 days/week; cumulative doses of 40.0, 60.0, and 80.0 Gy) and a hyperfractionated schedule (1.6 Gy/fraction, 2 fractions/day, 5 days/week, cumulative doses of 41.6, 60.8, and 80.0 Gy). We compared unilaterally with bilaterally irradiated anastomoses for two conventional radiation schedules.

METHODS AND MATERIALS

The rectosigmoid was always irradiated. Depending on the experiment, the cecum was irradiated or not. A side-to-side anastomosis between rectosigmoid and cecum was constructed the day following the last irradiation. The strength of the anastomosis was evaluated by means of a bursting pressure (BP) measurement after 10 days. A control group and a sham-treated group were carried out.

RESULTS

Compared to controls, the strength of unilaterally irradiated anastomoses was not altered and BP values were independent of the radiation schedule and of the cumulative dose. In case of bilaterally irradiated colon anastomoses, anastomotic strength was significantly reduced at 80 Gy, but not at 40 Gy.

CONCLUSIONS

After high doses of preoperative radiotherapy, colon anastomoses in rats can be safely constructed if only one anastomotic segment is irradiated. The strength of bilaterally irradiated colon anastomoses is dose-dependent.

Evaluation of a biofragmentable anastomosis ring for small intestinal anastomosis in ponies

Six ponies divided into two groups of three were used in a double crossover study design. Group 1 ponies had a small intestinal resection and anastomosis performed using a biofragmentable anastomosis ring (BAR); group 2 ponies had a hand-sewn small intestinal resection and anastomosis using a Gambee suture pattern. Approximately 30 days later, all ponies had a second celiotomy and anastomosed segments were removed. Group 1 ponies had a hand-sewn anastomosis performed and group 2 had a BAR. The anastomotic sites were collected at necropsy approximately 30 days later. Anastomosed intestinal segments were evaluated with ultrasound to determine lumen diameter, area, circumference, and wall thickness. Gross descriptions of adhesions were recorded and sections of the anastomotic site were taken for histological evaluation. Time to perform the BAR anastomosis was significantly less (P = .0004) than for the hand-sewn Gambee anastomosis. Ponies with handsewn anastomoses had no signs of colic, whereas five of six ponies with BAR anastomoses had several episodes of abdominal discomfort, between day 16 to 18, corresponding to the time of BAR disintegration as determined by abdominal radiographs. Hand-sewn anastomoses had a tendency to have more adhesion formation than BAR anastomoses, but all anastomoses, except one BAR anastomosis, were graded as having a low obstructive potential. BAR anastomoses had a significantly larger mean index of stenosis for intraluminal diameter (76% +/- 13.6), area (93.7% +/- 6.01) and circumference (75.8% +/- 14.0) than the hand-sewn anastomoses (26.6% +/- 11.9; 44.6% +/- 19.5; 26.8% +/- 12.7). The BAR anastomoses also had a significantly smaller mean intraluminal diameter (0.96 cm +/- 0.49), area (0.838 cm2 +/- 0.65) and circumference (3.28 cm +/- 1.63) than the hand sewn anastomoses (3.11 cm +/- 0.73; 7.99 cm2 +/- 3.9; 10.3 cm +/- 2.47). In addition, the BAR anastomoses had a significantly larger (P = .0069) bowel wall thickness at the anastomoses and a significantly larger (P = .047) wall thickness proximal to the anastomosis than the hand-sewn anastomoses, indicating some degree of hypertrophy because of chronic obstruction. No significant difference was found in the diameter, area, or circumference between bowel proximal and distal to the anastomosis for either the BAR or Gambee techniques, or between the BAR and Gambee anastomosis as a measure of chronic obstruction. There was a significantly higher (P = .0043) histological score (worse healing) for mucosal healing and continuity for the BAR, as well as a tendency to score higher for inflammation, anastomotic alignment, and anastomotic fibrosis. The BAR technique had a significantly higher (P = .0043) total histological score than the Gambee technique. Although the BAR was advantageous in many respects, results of this study suggest that it should not be used for equine small intestinal anastomosis because of the potential for stricture formation.

Comparison of a biofragmentable intestinal anastomosis ring with appositional suturing for subtotal colectomy in normal cats

A subtotal colectomy was performed on 12 normal adult cats using an interrupted apposing suture pattern of monofilament polyglyconate (n = 6) or a biofragmentable intestinal anastomosis ring (Valtrac, Davis and Geck Company, Danbury, CT) (n = 6) composed of polyglycolic acid and barium sulfate. Abdominal radiographs were made daily, beginning 10 days after surgery, to determine fragmentation rates of the anastomosis ring. The cats were euthanatized 30 days after surgery, and a gross and histopathological evaluation of anastomotic healing and stricture formation was performed. The technique for implantation of the anastomosis ring was easy to learn and required only two purse string sutures to complete. Intraoperative complications associated with the anastomosis ring were minor, and included problems with purse string suture placement, small serosal tears, and spasms of the colon that reduced the lumenal diameter. There were no intraoperative complications in the cats with sutured anastomoses. Postoperative recovery was uneventful in all cats. The anastomosis rings fragmented 12.2 +/- 1.1 days (mean +/- standard deviation [SD]) after implantation and passed in the stool 3.8 +/- 1.9 days later without clinical signs in five of six cats. There were no statistically significant differences between the time required to perform the anastomosis (P = .348), postmortem gross anastomosis grades (P = .088), or percent of lumenal stricture (P = .178) between the two groups. Histologically, the only significant differences were an increased muscular inversion in the anastomoses performed using the fragmentable ring (P = .039) and an increased muscular eversion in the sutured anastomoses (P < .001) compared with normal colonic architecture.

Protective effect of RibCys following high-dose irradiation of the rectosigmoid

Ribose-cysteine (RibCys) is a prodrug of L-cysteine that stimulates glutathione biosynthesis. Increased glutathione levels have been shown to have a protective effect against radiation-induced injury and oxidative stress. Surface oximetry has previously been used successfully to predict anastomotic leakage.

PURPOSE

The following study was done to evaluate the protective effect of RibCys and the predictive value of PtO2 determinations in a swine model.

METHODS

Domestic swine were divided into three groups: Group A served as a nonradiated control; Group B received 6,000 to 6,500 rad to the rectosigmoid; and Group C received RibCys (1 g/kg) prior to receiving 6,000 to 6,500 rad. Radiated animals and controls underwent rectosigmoid resection after a three-week rest period. Intraoperative anastomotic PtO2 was checked with a modified Clark electrode. Anastomoses were evaluated radiographically at three and seven days; animals were sacrificed, and bursting strength was recorded at 10 days.

RESULTS

Mean bursting pressures were 243.8 +/- 59.4, 199.5 +/- 37.8, and 209.5 +/- 54.9 mmHg (NS) for Groups A, B, and C, respectively. Anastomotic PtO2 ranged from 19 to 98 mmHg and could not be correlated with anastomotic leaks or bursting pressure. There were 11/15 radiation-related deaths and leaks (eight deaths and three leaks) in the radiated group and 4/12 radiation-related deaths and leaks (three deaths and one leak) in the group receiving radiation and RibCys (P < 0.04).

CONCLUSIONS

1) RibCys protected animals against radiation-related deaths and anastomotic leaks following high doses of pelvic irradiation; 2) anastomotic PtO2 levels did not correlate with anastomotic healing in this model.

Prospective, randomized trial of the biofragmentable anastomosis ring. The BAR Investigational Group

A randomized trial was undertaken to compare the biofragmental anastomotic ring (BAR) with conventional intraperitoneal colorectal anastomotic techniques. Patients were randomized into one of two schemes: BAR versus sutured or BAR versus stapled anastomosis. There were 782 patients entered into the study and 283 patients (36%) had a sutured anastomosis, 104 patients (13%) had a stapled anastomosis, and 395 (51%) had the BAR. Comparison of the BAR with combined suture and stapled controls revealed no significant differences in wound complication, abscess rate, bleeding, anastomotic leaks, ileus, obstruction, or deaths. There were no differences in return of bowel function, return to normal diet, or hospital stay. Intraoperative difficulties occurred in 46 BAR patients (17%), and this was significantly higher (p less than 0.001) than for sutured (3%) but not for stapled anastomoses (11%). The occurrence of these problems did not adversely effect the outcome. The data suggest that the BAR is a safe, satisfactory alternative to sutured or stapled colorectal anastomoses.

Experience with the biofragmentable anastomotic ring (BAR) in bowel preoperatively irradiated with 6000 rad

Previous studies from the authors' laboratory using the biodegradable anastomotic ring (BAR) have demonstrated the safety of this device in animals irradiated preoperatively with the equivalent of 5000 rad; sutured, stapled, and BAR anastomoses all had leak rates of 10 percent or less in this setting. This study was undertaken to assess the safety of the BAR after irradiation with the equivalent of 6000 rad. Thirteen mongrel dogs underwent preoperative irradiation to the rectum and rectosigmoid, receiving 6000 rad according to the nominal standard dose equation. After a three-week rest period, each dog underwent anterior resection of the rectosigmoid and anastomosis with the BAR. The anastomoses were evaluated for early and late healing and anastomotic leaks. The results were compared with previous data from the authors' laboratory using an identical model. Radiographic leaks were found in 7 of 10 sutured anastomoses, 8 of 10 stapled anastomoses, and 3 of 13 BAR anastomoses (P less than 0.01). Comparative clinical leaks were 5 of 10 for sutured, 5 of 10 for stapled, and 3 of 13 for BAR anastomoses. These data suggest that the BAR may offer added safety to an anastomosis after preoperative irradiation. Whether this effect is due to the atraumatic technique of placing the device, improved blood flow to the anastomotic margins, or other factors, is still underdetermined.

Sutureless large bowel anastomosis: European experience with the biofragmentable anastomosis ring

Sutureless colonic anastomosis using a biofragmentable anastomosis ring (BAR) has been evaluated in a prospective randomized comparison with sutures and staples for elective colorectal surgery. One hundred and one patients underwent BAR anastomosis, 85 a sutured anastomosis, and 16 a stapled anastomosis. There were two anastomotic leaks in the patients undergoing BAR anastomosis, seven in patients having a sutured anastomosis, and one in a patient who had a stapled anastomosis. Wound infection occurred in ten BAR patients, ten sutured patients and no stapled patient. There was no statistically significant difference in these or in other postoperative complications between the groups. The BAR was easy to use and is a safe alternative to sutures and staples for large bowel anastomosis.