Comparative study on the establishment efficacy of four types of animal models of rectovaginal fistula in rabbits.

Various surgical methods have so far been developed for treating rectovaginal fistula (RVF), each with its own advantages and disadvantages. The lack of standardized animal models of RVF is a major reason for the failure to establish a unified and effective surgical method for the treatment of RVF. This study aimed to explore the feasibility of an RVF animal model by magnetic compression and compare it with the traditional modeling method. Thirty-two female Japanese white rabbits were randomly divided into four groups: A, B, C, and D, based on how the rectovaginal septum was treated. The operation time, intraoperative blood loss, and model success rate of each group were determined. The experimental animals were euthanized 2 weeks after the operation. Their rectovaginal septum specimens were obtained. RVF was observed by the naked eye. The fistula size was measured. Histological changes of fistula were observed by hematoxylin and eosin and Masson staining. All rabbits completed the RVF model and survived 2 weeks after the operation. Groups A and B had no bleeding, while groups C and D had < 0.5 mL of bleeding. The magnet detached in 4-6 days in group A, while it remained in place for 2 weeks after surgery in group B. Only one group D rabbit had a plastic hose for 2 weeks after surgery. The RVFs of groups A and C healed by themselves. In group B, the fistula was well formed. In group D, fistula healing was observed in three animals and the diameter of the fistulas was only 2.82-4.64 mm in the other four animals. Groups B and D had a scar on the inner surface of fistulas. Our study shows that the magnetic compression technique based on the T-shaped magnet is a highly useful method to establishing a continuous and stable RVF model in rabbits.

Optimization of tracheoesophageal fistula model established with T-shaped magnet system based on magnetic compression technique.

BACKGROUND: The magnetic compression technique has been used to establish an animal model of tracheoesophageal fistula (TEF), but the commonly shaped magnets present limitations of poor homogeneity of TEF and poor model control. We designed a T-shaped magnet system to overcome these problems and verified its effectiveness via animal experiments. AIM: To investigate the effectiveness of a T-shaped magnet system for establishing a TEF model in beagle dogs. METHODS: Twelve beagles were randomly assigned to groups in which magnets of the T-shaped scheme (study group, n = 6) or normal magnets (control group, n = 6) were implanted into the trachea and esophagus separately under gastroscopy. Operation time, operation success rate, and accidental injury were recorded. After operation, the presence and timing of cough and the time of magnet shedding were observed. Dogs in the control group were euthanized after X-ray and gastroscopy to confirm establishment of TEFs after coughing, and gross specimens of TEFs were obtained. Dogs in the study group were euthanized after X-ray and gastroscopy 2 wk after surgery, and gross specimens were obtained. Fistula size was measured in all animals, and then harvested fistula specimens were examined by hematoxylin and eosin (HE) and Masson trichrome staining. RESULTS: The operation success rate was 100% for both groups. Operation time did not differ between the study group (5.25 min ± 1.29 min) and the control group (4.75 min ± 1.70 min; P = 0.331). No bleeding, perforation, or unplanned magnet attraction occurred in any animal during the operation. In the early postoperative period, all dogs ate freely and were generally in good condition. Dogs in the control group had severe cough after drinking water at 6-9 d after surgery. X-ray indicated that the magnets had entered the stomach, and gastroscopy showed TEF formation. Gross specimens of TEFs from the control group showed the formation of fistulas with a diameter of 4.94 mm ± 1.29 mm (range, 3.52-6.56 mm). HE and Masson trichrome staining showed scar tissue formation and hierarchical structural disorder at the fistulas. Dogs in the study group did not exhibit obvious coughing after surgery. X-ray examination 2 wk after surgery indicated fixed magnet positioning, and gastroscopy showed no change in magnet positioning. The magnets were removed using a snare under endoscopy, and TEF was observed. Gross specimens showed well-formed fistulas with a diameter of 6.11 mm ± 0.16 mm (range, 5.92-6.36 mm), which exceeded that in the control group (P < 0.001). Scar formation was observed on the internal surface of fistulas by HE and Masson trichrome staining, and the structure was more regular than that in the control group. CONCLUSION: Use of the modified T-shaped magnet scheme is safe and feasible for establishing TEF and can achieve a more stable and uniform fistula size compared with ordinary magnets. Most importantly, this model offers better controllability, which improves the flexibility of follow-up studies.

Feasibility experiment of a novel deformable self-assembled magnetic anastomosis ring (DSAMAR) for gastrointestinal anastomosis through a natural orifice.

Although the application of magnetic compression anastomosis is becoming increasingly widespread, the magnets used in earlier studies were mostly in the shape of a whole ring. Hence, a deformable self-assembled magnetic anastomosis ring (DSAMAR) was designed in this study for gastrointestinal anastomosis. Furthermore, its feasibility was studied using a beagle model. The designed DSAMAR comprised 10 trapezoidal magnetic units. Twelve beagles were used as animal models, and DSAMARs were inserted into the stomach and colon through the mouth and anus, respectively, via endoscopy to achieve gastrocolic magnamosis. Surgical time, number of failed deformations, survival rate of the animals, and the time of magnet discharge were documented. A month later, specimens of the anastomosis were obtained and observed with the naked eye as well as microscopically. In the gastrocolic anastomosis of the 12 beagles, the procedure took 65-120 min. Although a deformation failure occurred during the operation in one of the beagles, it was successful after repositioning. The anastomosis was formed after the magnet fell off 12-18 days after the operation. Naked eye and microscopic observations revealed that the anastomotic specimens obtained 1 month later were well-formed, smooth, and flat. DSAMAR is thus feasible for gastrointestinal anastomosis under full endoscopy via the natural orifice.

A novel magnetic compression technique for establishment of a vesicovaginal fistula model in Beagle dogs.

Vesicovaginal fistula lacks a standard, established animal model, making surgical innovations for this condition challenging. Herein, we aimed to non-surgically establish vesicovaginal fistula using the magnetic compression technique, and the feasibility of this method was explored using eight female Beagle dogs as model animals. In these dogs, cylindrical daughter and parent magnets were implanted into the bladder and vagina, respectively, after anesthesia, and the positions of these magnets were adjusted under X-ray supervision to make them attract each other, thus forming the structure of daughter magnet-bladder wall-vaginal wall-parent magnet. Operation time and collateral damage were recorded. The experimental animals were euthanized 2 weeks postoperatively, and the vesicovaginal fistula gross specimens were obtained. The size of the fistula was measured. Vesicovaginal fistula was observed by naked eye and under a light microscope. Magnet placement was successful in all dogs, and remained in the established position for the reminder of the experiment. The average operation time was 14.38 min ± 1.66 min (range, 12-17 min). The dogs were generally in good condition postoperatively and were voiding normally, with no complications like bleeding and urine retention. The magnets were removed from the vagina after euthanasia. The vesicovaginal fistula was successfully established according to gross observation, and the fistula diameters were 4.50-6.24 mm. Histological observation revealed that the bladder mucosa and vaginal mucosa were in close contact on the internal surface of the fistula. Taken together, magnetic compression technique is a simple and feasible method to establish an animal model of vesicovaginal fistula using Beagle dogs. This model can help clinicians study new surgical techniques and practice innovative approaches for treating vesicovaginal fistula.

Endoscopic gastrointestinal bypass anastomosis using deformable self-assembled magnetic anastomosis rings (DSAMARs) in a pig model.

BACKGROUND: To investigate the feasibility of a deformable self-assembled magnetic anastomosis ring (DSAMAR), designed and developed by us, for endoscopic gastrointestinal bypass anastomosis. METHODS: Ten experimental pigs were used as model animals. The DSAMAR comprises 10 trapezoidal magnetic units, arranged in a straight line under the constraint of a guide wire. When the desired anastomosis site is reached under the guidance of an endoscope, the catheter pushes the magnetic unit along the guide wire. The linear DSAMAR can be assembled into a circular DSAMAR. Two DSAMARs were inserted, one at the end of the duodenum and the other into the stomach successively. They attracted each other and compressed the wall of the stomach and duodenum to establish gastrointestinal bypass anastomosis. The experimental pigs were euthanized 4 weeks after the operation, and the gastrointestinal bypass anastomosis specimens were obtained. The anastomosis formation was evaluated by the naked eye and histology. RESULTS: Gastrointestinal bypass anastomosis with DSAMARs was successfully performed. The average operation time under an endoscope was 70.30 ± 19.05 min (range: 43-95 min). The DSAMARs were discharged through the anus 10-17 days after surgery. There were no complications such as gastrointestinal bleeding, perforation, anastomotic fistula, and gastrointestinal obstruction during and after the operation. Gastroscopy and gross specimen of the anastomosis showed a well-formed magnetic anastomosis. Histological observation showed good continuity of the serous membrane and the mucosa of magnetic anastomosis. CONCLUSION: The DSAMAR is a safe and feasible device for fashioning gastrointestinal bypass anastomosis in this animal model.

Application of Y-Z deformable magnetic ring for recanalization of transanal single-access rectal stricture.

Magnetic compression anastomosis has been reported to have remarkable clinical outcomes. Here, we tested the applicability of a Y-Z deformable magnetic ring (DMR) for non-surgical manipulation of rectal stenosis (RS) in a beagle dog model under a transanal single-access condition. RS was modeled in 8 beagle dogs using partial ligation with silk thread. Under X-ray guidance, the Y-Z DMR was positioned at the proximal and distal ends of the RS, and the magnetic ring was bent into an "O" shape, such that the two rings were magnetically attracted. Operation time, complications during or after operation, and discharge time of the magnetic rings were recorded. The anastomosis bursting pressure was measured two weeks after removing the rings, and its formation was assessed through gross and histological examination. Partial ligation with a silk thread successfully established the canine RS model. After Y-Z DMR installation, the magnetic ring was successfully reconfigured from an "S" to an "O" shape. Strong attraction existed between the rings. The operation time was 9-15 min (average: 11.75 ± 1.98 min). No rectal bleeding or perforation occurred during or after operation. The ring was naturally expelled 7-10 days after surgery. A pressure of > 300 mmHg was recorded at the point of anastomosis rupture. The rectal anastomosis appeared to have healed properly on the surface, which was confirmed histologically, signifying the success of this procedure. A Y-Z DMR facilitated the successful recanalization of transanal single-channel RS without needing surgery in an animal model.

A Novel Deformable Self-Assembled Magnetic Anastomosis Ring (DSAMAR) for Esophageal Stenosis Recanalization without Temporary Gastrostomy in Beagle Dogs.

BACKGROUND: To assess the feasibility of a deformable self-assembled magnetic anastomosis ring (DSAMAR) in the treatment of esophageal stenosis in beagle dogs via transoral access without temporary gastrostomy. METHODS: Experimental esophageal stenosis was created in 10 beagle dogs by partial cervical esophageal ligation. The DSAMAR was inserted into the distal esophagus via the narrow section of the esophagus using a gastroscope. A circular DSAMAR was placed in the proximal esophagus. The magnetic rings on both sides of the experimental stenosis automatically attracted each other. We then recorded the operation time, postoperative complications, anastomotic formation time, and magnetic ring discharge time. The dogs were euthanized 4 weeks postoperatively; subsequently, we obtained the esophageal anastomotic specimens and observed the anastomotic formation via the naked eye and by light microscopy. RESULTS: Our esophageal stenosis model produced reproducible stenoses in all dogs, which was confirmed via endoscopy and esophagography. DSAMAR was successfully implanted in all experimental animals under endoscopic and X-ray monitoring, and all linear DSAMARs were successfully transformed into rings. The magnets at both ends of the esophageal stenosis were automatically attracted. All animals survived until euthanasia. No complications, including esophageal perforation, bleeding, and gastrointestinal obstruction, were noted during the perioperative period. The mean operation time of endoscopic magnetic anastomosis was 15.6 ± 2.41 (range, 12-19) min. The mean esophageal anastomotic formation time was 8.8 ± 1.03 (range, 7-10) days, and the mean expulsion time of DSAMAR was 13.94 ± 2.88 (range, 10-19) days. Gastroscopy and esophagography were performed at 4 weeks postoperatively; the esophageal patency was good. Macroscopic observation of the esophageal anastomotic specimens revealed that the esophageal mucosal layer of the anastomosis had good continuity and the anastomosis was smooth. CONCLUSION: DSAMAR is a feasible option for magnetic recanalization of esophageal stricture via transoral access without temporary gastrostomy.

Novel deformable self-assembled magnetic anastomosis ring for endoscopic treatment of colonic stenosis via natural orifice.

BACKGROUND: Although endoscope-assisted magnetic compression anastomosis has already been reported for colonic anastomosis, there is no report on a single-approach operation using the natural orifice. AIM: To design a deformable self-assembled magnetic anastomosis ring (DSAMAR) for colonic anastomosis for use in single-approach operation and evaluate its feasibility and safety through animal experiments. METHODS: The animal model for colonic stenosis was prepared by partial colonic ligation in eight beagles. The magnetic compression anastomosis of their colonic stricture was performed by endoscopically assisted transanal implantation of the DSAMAR. The anastomotic specimen, obtained 2 wk after the operation, was observed by both the naked eye and a light microscope. RESULTS: The DSAMAR was successfully inserted into the proximal end of colon stenosis through the anus. The DSAMAR of seven dogs was successfully transformed into rings, while that of the remaining dog was removed after the first deformation failed. The rings were successfully retransformed after optimization. All animals underwent colonic anastomosis using the DSAMAR. No device-related or procedure-related adverse events were observed. The colostomy specimens of the experimental dogs were obtained 2 wk after the operation. Both gross and histological observations showed good anastomotic healing. CONCLUSION: The DSAMAR is a safe and feasible option for the treatment of colon stenosis. Its specific deformation and self-assembly capability maximize the applicability of the minimally invasive treatment.

Primary animal experiment to test the feasibility of a novel Y-Z magnetic hepatic portal blocking band.

BACKGROUND: Hepatic portal blood flow occlusion is a common technique for reducing hepatic hemorrhage during hepatectomy. We designed a novel Y-Z magnetic hepatic portal blocking band (Y-Z MHPBB) based on the principle of magnetic compression technique. AIM: To introduce the Y-Z MHPBB device and verify the feasibility of this device for hepatic portal blood flow occlusion in dogs. METHODS: Ten beagles were randomly divided into the experimental group and control group. The operation time, intraoperative blood loss, the number of portal blood flow occlusions, the total time spent on adjusting the blocking band, and the average time spent on adjusting the blocking band were recorded. The surgeons evaluated the feasibility and flexibility of the two portal occlusion devices. RESULTS: Laparoscopic hepatectomy was successfully performed in both the experimental group and control group. There was no statistical difference between the two groups in the operation time, intraoperative blood loss, and the number of hepatic portal blood flow occlusions. With respect to the total time spent on adjusting the blocking band and the average time spent on adjusting the blocking band, the experimental group showed significantly better outcomes than the control group, with a statistical difference (P < 0.05). The operators found that the Y-Z MHPBB was superior to the modified T-tube in terms of operational flexibility. CONCLUSION: The Y-Z MHPBB seems to be an ingenious design, accurate blood flow occlusion effect, and good flexibility; and it can be used for hepatic portal blood flow occlusion during laparoscopic hepatectomy.

Magnetic compression anastomosis for reconstruction of digestive tract after total gastrectomy in beagle model.

BACKGROUND: Magnetic compression anastomosis (MCA) is a simple procedure contributing to a reliable anastomosis. However, digestive-tract reconstruction after total gastrectomy using MCA has not yet been reported. AIM: To investigate the feasibility of MCA for simultaneous esophagojejunostomy and jejunojejunostomy after total gastrectomy using beagle dogs. METHODS: Sixteen beagles were randomly divided into an MCA group (study group, n = 8) and a manual-suture anastomosis group (control group, n = 8). Two different magnetic anastomosis devices were used in the study group for esophagojejunal and jejunojejunal anastomoses. Both devices included a pair of circular daughter and parent magnets each. The time of esophagojejunostomy and jejunojejunostomy, postoperative complications, and survival rate of the two groups were compared. The dogs were sacrificed one month after the operation and their anastomotic specimens were obtained. Healing was observed by the naked eye and a light microscope. RESULTS: Digestive-tract reconstruction after total gastrectomy was successfully completed in both groups (survival rate = 100%). In the study group, esophagojejunal and jejunojejunal anastomoses took 6.13 ± 0.58 and 4.06 ± 0.42 min, respectively, significantly lower than those in the control group (15.63 ± 1.53 min, P < 0.001 and 10.31 ± 1.07 min, P < 0.001, respectively). Complications such as bleeding, anastomotic leakage, and anastomotic stenosis were not observed. In the study group, the magnets did not interfere with each other. Discharge time of the jejunojejunal magnetic anastomosis device was 10.75 ± 1.28 d, while that of the esophagojejunal magnetic anastomosis device was 12.25 ± 1.49 d. Residual silk was found in the control group. The study group showed a greater smoothness of the anastomosis than that of the control group. All layers of anastomosis healed well in both groups. CONCLUSION: MCA is a safe and feasible procedure for digestive-tract reconstruction after total gastrectomy in this animal model.

A novel magnetic compression technique for cystostomy in rabbits.

Magnetic compression technique (MCT) is a popular new anastomosis method. In this paper, we aimed to explore the feasibility of use of MCT for performing cystotomy in rabbits. The parent magnets and daughter magnets for rabbit cystostomy were designed and manufactured according to the anatomical characteristics of rabbit lower urinary tract. Twelve female New Zealand rabbits were used as animal models. After anesthesia, a daughter magnet was inserted into the bladder through the urethra, and the parent magnet was placed on the body surface projection of the bladder over the abdominal wall. The two magnets automatically attract each other. Postoperatively, the state of magnets was monitored daily, and the time when the magnets fell off was recorded. Cystostomy with MCT was successfully performed in all twelve rabbits. The mean operation time was 4.46 ± 0.75 min. The magnets fell off from the abdominal wall after a mean duration of 10.08 ± 1.62 days, resulting in the formation of bladder fistula. Macroscopic and microscopic examination showed that the fistula was well formed and unobstructed. The junction between bladder and abdominal wall was tight and smooth. We provide preliminary experimental evidence of the safety and feasibility of cystostomy based on MCT.