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Esophagogastric anastomotic wound healing in rats
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Original article Esophagogastric anastomotic wound healing in rats Y. Cui, J. D. Urschel Department of Thoracic Surgery, Roswell Park Cancer Institute, and State University of New York at Bualo, Bualo, NY, USA SUMMARY. Esophagectomy with esophagogastric anastomosis is commonly complicated by anastomotic dehiscence. Although this is a major problem in clinical esophageal surgery, laboratory investigation of esophagogastric anastomotic wound healing has been hampered by the lack of a practical rodent model. Problems with aspiration pneumonia and anastomotic strictures hindered our previous studies in the rat. Other researchers have turned to large animal experiments, or used various upper gastrointestinal pseudoanastomotic techniques in rodents. None of these approaches has proved satisfactory. We developed a technique of side-to-side esophagogastric anastomosis in the rat, and then studied normal esophagogastric anastomotic healing in this model. Anastomoses were performed in 24 rats. Anastomotic breaking strength and hydroxyproline concentration were measured 1 and 2 weeks after surgery. Anastomotic breaking strength was 3.78 1.18 N at 1 week and 4.83 0.91 N after 2 weeks (p < 0.03). Anastomotic tissue hydroxyproline concentration was 370.6 31.2 nmol/mg at 1 week and 462.1 69.7 nmol/mg after 2 weeks (p < 0.001). Many of the problems encountered in esophagogastric anastomotic studies in the rat have been overcome using this new model. INTRODUCTION Esophagogastric anastomotic leaks complicate 5–20% of esophagectomies for esophageal cancer. 1,2 Anastomotic leaks are responsible for approximately one-third of perioperative deaths after esophagec- tomy. 3 Despite the seriousness of this clinical prob- lem, surprisingly little laboratory investigation of esophagogastric anastomotic wound healing has been carried out. 1 Unlike small bowel and colon anasto- moses 4,5 , esophagogastric anastomoses are techni- cally dicult to perform in rodents. A consistent and reproducible small animal model for esophagogastric anastomotic wound healing studies would facilitate further laboratory investigation in this area. We describe a technique for esophagogastric anastomoses in the rat and report anastomotic wound healing results in this model. MATERIALS AND METHODS Twenty-four female Sprague–Dawley (Harlan, Indianapolis, IN, USA) rats (200–250 g) were fasted for 4 h and then anesthetized with intraperitoneal pentobarbital sodium (50 mg/kg) (Abbott Laborato- ries, Abbott Park, IL, USA). Antibiotics were not given. Using a sterile technique, a 3-cm midline laparotomy was performed. The distal esophagus was mobilized using blunt dissection. The vagus nerves were preserved to prevent post-operative gastropare- sis. The anterior aspect of the esophagus was incised transversely at a point 5 mm proximal to the gastro- esophageal junction. A 4-mm gastrotomy was made in the glandular portion of the proximal anterior stomach. The gastrotomy was made obliquely, be- tween the first and second branches of the left gastric artery. A side-to-side single-layer anastomosis was constructed using interrupted 7–0 polypropylene (Ethicon, Somerville, NJ, USA) sutures. The sutures were placed through all layers of the stomach and esophagus. Suturing began by placing two traction sutures between each end of the esophagotomy and gastrotomy. With gentle traction, the stomach was brought into apposition with the esophagus. A third suture was placed halfway between the end sutures, in Address correspondence to: J. D. Urschel, Department of Surgery, St. Joseph’s Hospital, 50 Charleton Ave East, Hamilton, Ontario, Canada L8N 4A6. Tel: (+1) 905 522 0118; Fax: (+1) 905 521 6190; e-mail: [email protected] 149 Diseases of the Esophagus (1999) 12, 149–151 Ó 1999 ISDE/Blackwell Science Asia
Transcript of Esophagogastric anastomotic wound healing in rats
Original article
Esophagogastric anastomotic wound healing in rats
Y. Cui, J. D. Urschel
Department of Thoracic Surgery, Roswell Park Cancer Institute, and State University of New York at Bu�alo,Bu�alo, NY, USA
SUMMARY. Esophagectomy with esophagogastric anastomosis is commonly complicated by anastomoticdehiscence. Although this is a major problem in clinical esophageal surgery, laboratory investigation ofesophagogastric anastomotic wound healing has been hampered by the lack of a practical rodent model. Problemswith aspiration pneumonia and anastomotic strictures hindered our previous studies in the rat. Other researchershave turned to large animal experiments, or used various upper gastrointestinal pseudoanastomotic techniques inrodents. None of these approaches has proved satisfactory. We developed a technique of side-to-sideesophagogastric anastomosis in the rat, and then studied normal esophagogastric anastomotic healing in thismodel. Anastomoses were performed in 24 rats. Anastomotic breaking strength and hydroxyproline concentrationwere measured 1 and 2 weeks after surgery. Anastomotic breaking strength was 3.78 � 1.18 N at 1 week and4.83 � 0.91 N after 2 weeks (p < 0.03). Anastomotic tissue hydroxyproline concentration was370.6 � 31.2 nmol/mg at 1 week and 462.1 � 69.7 nmol/mg after 2 weeks (p < 0.001). Many of the problemsencountered in esophagogastric anastomotic studies in the rat have been overcome using this new model.
INTRODUCTION
Esophagogastric anastomotic leaks complicate5±20% of esophagectomies for esophageal cancer.1,2
Anastomotic leaks are responsible for approximatelyone-third of perioperative deaths after esophagec-tomy.3 Despite the seriousness of this clinical prob-lem, surprisingly little laboratory investigation ofesophagogastric anastomotic wound healing has beencarried out.1 Unlike small bowel and colon anasto-moses4,5, esophagogastric anastomoses are techni-cally di�cult to perform in rodents. A consistent andreproducible small animal model for esophagogastricanastomotic wound healing studies would facilitatefurther laboratory investigation in this area. Wedescribe a technique for esophagogastric anastomosesin the rat and report anastomotic wound healingresults in this model.
MATERIALS AND METHODS
Twenty-four female Sprague±Dawley (Harlan,Indianapolis, IN, USA) rats (200±250 g) were fastedfor 4 h and then anesthetized with intraperitonealpentobarbital sodium (50 mg/kg) (Abbott Laborato-ries, Abbott Park, IL, USA). Antibiotics were notgiven. Using a sterile technique, a 3-cm midlinelaparotomy was performed. The distal esophagus wasmobilized using blunt dissection. The vagus nerveswere preserved to prevent post-operative gastropare-sis. The anterior aspect of the esophagus was incisedtransversely at a point 5 mm proximal to the gastro-esophageal junction. A 4-mm gastrotomy was madein the glandular portion of the proximal anteriorstomach. The gastrotomy was made obliquely, be-tween the ®rst and second branches of the left gastricartery.
A side-to-side single-layer anastomosis wasconstructed using interrupted 7±0 polypropylene(Ethicon, Somerville, NJ, USA) sutures. The sutureswere placed through all layers of the stomach andesophagus. Suturing began by placing two tractionsutures between each end of the esophagotomy andgastrotomy. With gentle traction, the stomach wasbrought into apposition with the esophagus. A thirdsuture was placed halfway between the end sutures, in
Address correspondence to: J. D. Urschel, Department of Surgery,St. Joseph's Hospital, 50 Charleton Ave East, Hamilton, Ontario,Canada L8N 4A6. Tel: (+1) 905 522 0118; Fax: (+1) 905 5216190; e-mail: [email protected]
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Diseases of the Esophagus (1999) 12, 149±151Ó 1999 ISDE/Blackwell Science Asia
the posterior aspect of the anastomosis (joining theinferior side of the esophagotomy to the superior sideof the gastrotomy). Two additional sutures wereplaced in the posterior half of the anastomosis. Thethree posterior sutures and the two end sutures wereserially tied. The knots of the posterior sutures weretied within the lumen. Three sutures were placed inthe anterior part of the anastomosis and tied withtheir knots outside the lumen. These sutures broughtthe superior aspect of the esophagotomy into appo-sition with the inferior part of the gastrotomy.
The linea alba was closed with a continuous 4±0polygalactin 910 (Ethicon, Somerville, NJ, USA)suture. The skin incision was closed with the samesuture, using a running horizontal mattress tech-nique. Animals were allowed free access to food andwater after recovery from anesthesia. Rats were killed1 and 2 weeks after surgery with an intraperitonealinjection of pentobarbital sodium (120 mg/kg). Oneanimal was killed early because of illness (pneumo-nia); it was excluded from further analysis. Anasto-moses were excised, mounted in an Instron mini-44tensiometer (Canton, MA, USA) and distracted at10 mm/min to measure breaking strength. Breakingstrength was measured in newtons (N). The anasto-motic tissue (wound plus 1 mm of tissue on each side)was then excised and subjected to hydroxyprolineanalysis (an indicator of wound collagen formation)as previously described.6
Measured data are presented as means � SD.Di�erences in breaking strength and hydroxyprolineconcentration were assessed using Student's t-test.A value of p < 0.05 was taken to be signi®cant. Thestudy was approved by the Institutional Animal Careand Use Committee and conducted in accordancewith the National Research Council's guide for thecare and use of laboratory animals.
RESULTS
Anastomotic breaking strength was 3.78 � 1.18 N at1 week and 4.83 � 0.91 N after 2 weeks (p < 0.03).Anastomotic tissue hydroxyproline concentrationwas 370.6 � 31.2 nmol/mg at 1 week and 462.1 �69.7 nmol/mg after 2 weeks (p < 0.001).
DISCUSSION
Gastrointestinal anastomotic wound healing has beenextensively investigated in animal models.4,5 Colonicand small intestinal anastomoses are simple toperform in rats, but it is di�cult to study esophagealanastomotic healing in rodents.7,8 If too large ananastomotic lumen is constructed, re¯ux and aspira-tion pneumonia can occur. However, the rat'sesophagus has a very small lumen, and anastomotic
stricturing is a more common problem than re¯ux.Strictures inevitably cause malnutrition in the rat;this is a major obstacle to successful laboratoryinvestigation of esophageal anastomotic healing.Therefore, some researchers have used larger animals,such as pigs, cats, dogs and primates, to studyesophageal anastomotic wound healing.9±13 Ethicaland ®nancial concerns limit the use of large animalsfor wound-healing studies. A rodent model ofesophageal anastomotic wound healing investigationis desirable.
Several approaches have been used to overcomethe di�culties of studying esophageal anastomotichealing in rats. When the research is primarily relatedto gastric `pull-up' surgery or gastroplasty tubeformation, gastric wound healing can be used as asurrogate for esophagogastric wound healing.8,13±15
This approach has obvious limitations. Anotherstrategy is to study linear esophagotomy woundhealing as a substitute for true anastomotic healing.7
However, experiments on linear esophagotomywound healing are not relevant to clinical esophagealsurgery. Finally, we have tried several end-to-endesophagogastric anastomotic techniques. Narrowingof the anastomotic lumen was a consistent problem,even if the esophageal end was `spatulated'. Wereported previously a technique of end-to-end esoph-agogastric anastomosis that left a small bridge ofnative esophagogastric junction intact.6 This tech-nique was fairly simple, but strictures still developedand animal nutrition was compromised. The tech-nique was only suitable for very short-term studies ofesophagogastric anastomotic healing.6
The problem of anastomotic strictures has beensolved by using a side-to-side technique. The side-to-side anastomosis has a bigger lumen than ourprevious end-to-side anastomosis. In addition, thenormal esophagogastric route of alimentation ispreserved. Therefore, the rat can maintain its normalnutritional state even if an anastomotic strictureoccurs. Our rat model should facilitate furtherlaboratory investigation of esophagogastric anasto-motic wound healing.
References
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6. Urschel J D, Antkowiak J G, DeLacure M D, Takita H.Ischemic conditioning (delay phenomenon) improves esoph-agogastric anastomotic wound healing in the rat. J Surg Oncol1997; 66: 254±256.
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