• View in gallery

    Photographs of a fresh cadaveric canine jejunal segment after closure of a 3-cm-long enterotomy with 3-0 barbed polyglyconate suture material applied in a simple continuous, single-layer appositional pattern. A—The segment is manually suspended between Doyen intestinal forceps. An 18-gauge IV catheter has been inserted into the jejunal lumen at each end of the intestinal segment. The catheter to the right of the image is connected to a fluid pump, and the catheter to the left side of the image is connected to a pressure transducer. B—For leak pressure testing, Hartmann solution containing methylene blue dye was infused through the catheter on the right of the image at a rate of 500 mL/h while the enterotomy site and serosal surface were monitored for leakage. In this segment, colored solution is visible on the antimesenteric portion, providing evidence of extraluminal leakage from the suture holes.

  • View in gallery

    Box-and-whisker plots of ILP determined during leak pressure testing of 36 fresh (tested within 4 hours after collection), chilled (stored at 4°C for 24 hours before testing), and frozen-thawed (stored at −20°C for 7 days and thawed at 21°C for 6 hours before testing) canine jejunal segments after enterotomy closure. Of the 12 segments in each group, 3 were derived from each of 4 dogs. Compared with findings for fresh and chilled segments, frozen-thawed segments leaked at significantly (P < 0.001 and P < 0.002, respectively) lower ILP. For each box, the horizontal line represents the median and the upper and lower boundaries represent the 75th and 25th percentiles, respectively. Whiskers represent the minimum and maximum values.

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Effect of presurgical storage conditions on leakage pressures of enterotomy sites closed with unidirectional barbed suture material in fresh, chilled, and frozen-thawed cadaveric canine jejunal specimens

Daniel J. Duffy BVM&s, MS1, Yi-Jen Chang BVetMed, MS1, Julie A. Balko VMD2, and George E. Moore DVM, PhD3
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  • 1 1Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607.
  • | 2 2Department of Molecular and Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607.
  • | 3 3Department of Veterinary Administration, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

Abstract

OBJECTIVE

To evaluate the effect of presurgical storage conditions on leakage pressures of enterotomy sites closed with unidirectional barbed suture material in fresh, chilled, and frozen-thawed cadaveric canine jejunal specimens.

SAMPLE

36 grossly normal jejunal segments obtained from 4 dog cadavers.

PROCEDURES

9 jejunal segments were harvested immediately from each euthanized dog and randomly assigned to be tested within 4 hours after collection (fresh segments), stored at 4°C for 24 hours before testing (chilled segments), or stored at −20°C for 7 days and thawed at 21°C for 6 hours before testing (frozen-thawed segments). For leakage pressure testing, a 3-cm-long antimesenteric enterotomy was performed and repaired with 3-0 unidirectional barbed suture material in a simple continuous pattern in each segment. Time to complete the enterotomy, initial leakage pressure, maximum intraluminal pressure, and leakage location were recorded for each segment.

RESULTS

Mean ± SD initial leakage pressure for fresh, chilled, and frozen-thawed segments was 52.8 ± 14.9 mm Hg, 51.8 ± 11.9 mm Hg, and 33.3 ± 7.7 mm Hg, respectively. Frozen-thawed segments had significantly lower mean initial leakage pressure, compared with findings for fresh or chilled segments. Time to complete the enterotomy, maximum intraluminal pressure, and leakage location did not differ among groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Leak pressure testing of cadaveric jejunal segments that are fresh or chilled at 4°C for 24 hours is recommended for enterotomy studies involving barbed suture material in dogs. Freezing and thawing of cadaveric jejunal tissues prior to investigative use is not recommended because leak pressure data may be falsely low.

Enterotomies are routinely performed in dogs for various purposes, such as treatment of foreign body obstruction, biopsy specimen collection, or enteral feeding tube placement.1,2 Among dogs that undergo an enterotomy, incisional dehiscence with leakage of luminal contents can be a major contributor to morbidity and death, and rates of full-thickness dehiscence in dogs are reported to be 3% to 28%.3–7 Dehiscence may result in septic peritonitis, which is a surgical emergency associated with a guarded prognosis; among affected dogs, the mortality rate is 36.4% to 85%.8–10 Thus, minimizing intestinal incisional dehiscence and leakage following enterotomy is critical for improving long-term outcomes for dogs that undergo gastrointestinal tract surgery.

A variety of hand-sewn and staple techniques11,12 are routinely used for intestinal closure. Use of barbed suture materials for intestinal closure has previously been investigated in several experimental studies.13–16 In the production of barbed suture material, automated processing creates either unidirectional or bidirectional barbs; when the suture material is used, the barbs lodge within tissues, allowing even distribution of tension along the incisional line. The tensile pull strength of barbed suture materials is equivalent to that of barbless suture material of the same size or 1 size smaller (as defined by the US Pharmacopeia).16 In canine leak pressure studies,13,15 the ILPs for barbed suture material and smooth monofilament suture material appear equivalent. Unidirectional barbed sutures have a preconstructed end loop, and the suture needle can be passed through the loop after the initial tissue bite; hence, no knot is needed. Moreover, the barbs prevent backward slippage of the suture material. Overall, these characteristics of the suture material negate the need for knotting for suture security, which can facilitate shorter operative times.15 The elimination of suture knots may be advantageous because knots represent the weakest portions of a suture line.17

Leakage pressure testing is commonly performed to evaluate surgical methods that mimic in vivo conditions prior to clinical implementation.2,13,18–24 Cadaveric samples have been used for leak pressure testing of barbed suture materials in canine,13,15 equine,25 and ovine studies22,23; in those studies, various specimen storage temperatures and handling techniques prior to definitive testing were evaluated. Multiple factors, including but not limited to sample manipulation, storage temperature, interval from sample collection to time of testing, and postmortem changes associated with tissue autolysis, may adversely change and negatively affect the microscopic architecture and tissue integrity of tested specimens and, subsequently, affect study results and data interpretation.21 Results of a recent study21 identified the negative impact of cryopreservation and the deleterious effects of a single freeze-thaw cycle on the integrity of closed enterotomies in cadaveric jejunal specimens obtained from juvenile pigs. To date, there is no consensus regarding the optimal storage conditions for canine intestinal specimens prior to postenterotomy leakage pressure testing.

Following enterotomy closure in cadaveric intestinal specimens, establishment of a seal at the site of closure that is water-tight at physiologic pressures is a crucial step in determining the efficacy and safety of experimental suture materials and patterns for use in live animals. Small intestinal peristaltic pressures in healthy dogs range between 15 and 25 mm Hg.26 Determination of any potential negative effect of storage conditions on leakage pressures of cadaveric tissue specimens is of critical importance for validation of the results of ex vivo enterotomy leak pressure studies. This information may lead to implementation of more rigorous protocol stipulations in future leakage pressure studies involving cadaveric specimens.

The purpose of the study reported here was to compare the effect of presurgical storage conditions on enterotomy site leakage pressures, specifically intraluminal pressure at the time of enterotomy leakage (ie, ILP) and MIP, following enterotomy closure with unidirectional barbed suture material placed in a single-layer appositional continuous pattern in cadaveric canine jejunal segments. We hypothesized that ILP and MIP would be greater for segments tested immediately following collection and segments chilled at 4°C for 24 hours prior to testing, compared with findings for segments that had undergone a single controlled freeze-thaw cycle (ie, stored at −20°C for 7 days and thawed at 21°C for 6 hours) prior to testing.

Materials and Methods

Sample collection

Four apparently healthy adult (> 1-year-old) mixed-breed dogs that weighed 25 to 30 kg were used in the study. The dogs were obtained from a local animal shelter and euthanized by IV administration of pentobarbital sodiuma for reasons unrelated to the study. Approval of the study protocol by an institutional animal use and care committee was not required by North Carolina State University. For each carcass, the portion of jejunum aborad to the caudal duodenal flexure and orad to the antimesenteric ileal vessel was harvested within 45 minutes following IV administration of pentobarbital sodium and cadaver transport. Dogs were not included in the study if there was any history of gastrointestinal signs (vomiting, regurgitation, or diarrhea) or dietary indiscretion. Dogs were also excluded from the study if they had been administered any medications within 6 weeks prior to study recruitment.

Following euthanasia, the gastrointestinal tract of each dog was rigorously inspected and rejected if gross abnormalities were observed. The collected portion of the jejunums were divided transversely on a durable surface with straight Metzenbaum scissors into 10-cm-long segments, yielding a total of 36 segments (9 segments/dog). The mesentery was carefully excised to avoid distortion and bunching of any intestinal segment. Jejunal segments were milked of their contents and then flushed with balanced electrolyte solutionb to clear ingesta from the lumen. The segments from each dog were randomly assigned by use of a random number generatorc to be tested within 4 hours after collection (fresh segment group), stored at 4°C for 24 hours before testing (chilled segment group), or stored at −20°C for 7 days and thawed at 21°C for 6 hours before testing (frozen-thawed segment group). Of the 12 segments in each group, 3 were derived from each dog.

Storage conditions

Jejunal segments assigned to the fresh segment group were placed in 200 mL of Hartmann solutionb in a sealed bagd at room temperature (21°C) and tested within 4 hours following collection. Segments assigned to the chilled segment group were placed in 200 mL of Hartmann solutionb in a sealed bagd and stored at 4°C within a thermostatically controlled environment for 24 hours prior to testing. Specimens were then allowed to warm to room temperature (21°C) prior to experimental testing. Segments assigned to the frozen-thawed segment group were individually wrapped in saline (0.9% NaCl) solution–soaked gauze and placed in a sealed bagd along with 200 mL of Hartmann solutionb; the segments were stored at −20°C within a thermostatically controlled environment for 7 days and then thawed at room temperature (21°C) for 4 to 6 hours prior to testing by means of a previously validated method for specimen freezing.27

Surgical procedure

Regardless of group assignment, all segments underwent the same testing procedure. Each fresh, chilled, or frozen-thawed segment was flushed with Hartmann solution,b manually suspended, and occluded by use of 2 atraumatic Doyen intestinal forceps placed 8 cm apart by the same investigator (Y-JC). A No. 11 scalpel blade was used to make a full-thickness stab incision in an avascular portion on the antimesenteric border of each jejunal segment. The incision was then extended to a length of 3 cm (measured with a calibrated ruler for standardization) with straight Metzenbaum scissors. Residual fluid was manually evacuated from the intestinal lumen prior to closure. Each enterotomy incision was then closed with 3-0 barbed polyglyconate suture materiale applied in a simple continuous single-layer appositional pattern by the same board-certified surgeon (DJD) who was experienced with the use of barbed suture. Full-thickness sutures were placed to ensure engagement of the submucosa. The suture line was secured by first passing the needle fully through the intestinal tissue at a location 0.5 cm proximal to the start of the incision and by inserting the suture needle through the preconstructed end loop. Tension was then placed on that suture to draw the suture loop tight against the serosal surface of the segment. A simple continuous suture line was then extended with suture bites placed 2 to 3 mm apart and 2 to 3 mm from the incision edge (Figure 1). At the termination of the suture line, 3 additional suture bites were performed before the suture was cut with scissors to a length of 3 mm without tying a knot. Even tension was maintained during each enterotomy closure while avoiding crushing of intestinal tissues, although this was only subjectively assessed. The time from the start to completion of suturing the enterotomy was recorded (in seconds) with a stop watch. Throughout the testing period, each segment was kept moist with Hartmann solutionb delivered by use of a spray bottle to prevent tissue desiccation.

Figure 1—
Figure 1—

Photographs of a fresh cadaveric canine jejunal segment after closure of a 3-cm-long enterotomy with 3-0 barbed polyglyconate suture material applied in a simple continuous, single-layer appositional pattern. A—The segment is manually suspended between Doyen intestinal forceps. An 18-gauge IV catheter has been inserted into the jejunal lumen at each end of the intestinal segment. The catheter to the right of the image is connected to a fluid pump, and the catheter to the left side of the image is connected to a pressure transducer. B—For leak pressure testing, Hartmann solution containing methylene blue dye was infused through the catheter on the right of the image at a rate of 500 mL/h while the enterotomy site and serosal surface were monitored for leakage. In this segment, colored solution is visible on the antimesenteric portion, providing evidence of extraluminal leakage from the suture holes.

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.220

Suture material

Each enterotomy closure was performed with 3-0 barbed polyglyconate suture materiale and a swaged 26-mm half-circle tapered needle. The contents of each suture package were sterile and used prior to the manufacturer's expiration date. Each suture package was opened immediately prior to use, and a new suture strand was used for each closure.

Evaluation of enterotomy site leakage following closure

The method of leak pressure testing used in the study was designed on the basis of the results of pilot experimentation performed for the purposes of this study prior to definitive testing. For the pilot experimentation, jejunal segments (n = 3/group) were collected from cadavers (n = 2) other than those used in the main study at the same animal shelter; segments were selected on the basis of the same exclusion criteria used in the main study. The pilot study was performed to determine the appropriate procedures for intestinal preparation, complete thawing of frozen intestinal segments, creation of an antimesenteric enterotomy, barbed suture closure, and determination of intraluminal leakage pressures. The optimal protocol was standardized and subsequently used during testing of all jejunal segments in the main study.

After enterotomy closure in each segment was complete, two 18-gauge, 1.16-inch, IV cathetersf were each inserted 1 cm from one or the other end of the enterotomy incision obliquely through the jejunal wall into the lumen (Figure 1). A 5-L bag of Hartmann solutionb containing 20 mL of methylene blue dyeg was connected to a fluid line,h which was in turn connected to a fluid pumpi that was then connected to a preplaced catheter (catheter 1). Another fluid linej was primed with Hartmann solution; one end of the fluid line was connected to a pressure transducer,i and the other end was attached to the other preplaced catheter (catheter 2). The pressure transducer was connected to a pressure monitork and zeroed at the level of each intestinal segment prior to testing. For definitive testing, fluid was infused through catheter 1 at a rate of 500 mL/h while the enterotomy site and serosal surface were monitored for leakage by a sole study investigator (DJD). Initial leakage pressure (recorded in mm Hg) was defined as the intraluminal pressure at which colored solution was first observed to visibly leak extraluminally from the closed enterotomy site. Leakage locations were recorded as being at the level of the preconstructed end loop, at any of the suture holes, or along the incisional line. After initial leakage, fluid was continuously infused at the same rate until there was complete failure of the enterotomy site, which was defined as either a sudden drop in pressure or the time when MIP reached a plateau that was sustained for at least 6 seconds.

Statistical analysis

Published data from an ex vivo study21 to compare enterotomy leak pressure among fresh, cooled, and frozen-thawed porcine jejunal segments and findings of the pilot experimentation performed prior to definitive testing of canine jejunal segments in this study were used in a sample size calculation. It was determined that a sample size of at least 12 intestinal segments/group was needed to detect a between-group difference in mean leakage pressure of 10 mm Hg (SD, 10 mm Hg) with a power of 0.8 and a confidence level of 95%.

Continuous numerical variables were assessed for conformity to normal distribution by the Shapiro-Wilk test, and there were no violations of the assumption of normality. Results for ILP (in mm Hg) and MIP (in mm Hg) are reported as mean ± SD. A frequency table was constructed to assess the distribution of observed leakage locations. A 1-way ANOVA was performed to assess for differences among the groups’ mean values of ILP and MIP. A Bartlett test was performed to assess homoscedasticity, and posthoc analysis was performed with the Scheffe method to assess results among groups. A Fisher exact test was performed to assess differences in leakage location among groups. A value of P ≤ 0.05 was considered significant. Statistical analysis was performed with commercially available software.l

Results

Dogs

The 4 dogs included in the study had no known history of gastrointestinal signs or dietary indiscretion and had not been administered any medications within 6 weeks prior to study recruitment. Following euthanasia, inspection of the gastrointestinal tract of each dog revealed no gross abnormalities. No jejunal segments were rejected at the time of collection.

Leak pressure testing

Enterotomies were successfully created and closed in all jejunal segments. Leak pressure testing of each segment was performed without technical error. In each group, jejunal segments were tested on the same day. Mean ± SD ILP and MLP for all groups were summarized (Table 1). There was a significant difference (P < 0.001) in mean ILP among groups. Compared with findings for fresh and chilled segments, frozen-thawed segments leaked at significantly (P < 0.001 and P < 0.002, respectively) lower ILP (Figure 2). There was no difference (P = 0.98) in mean ILPs for the fresh and chilled segment groups. Among the 3 experimental groups, MIP did not differ significantly (P = 0.68).

Table 1—

Mean ± SD ILP and MIP determined during leak pressure testing of 36 fresh (tested within 4 hours after collection), chilled (stored at 4°C for 24 hours before testing), and frozen-thawed (stored at −20°C for 7 days and thawed at 21°C for 6 hours before testing) canine jejunal segments after enterotomy closure.

 Segment group (No. of specimens)
VariableFresh (12)Chilled (12)Frozen and thawed (12)
ILP (mm Hg)52.8 ± 14.9a51.8 ± 11.9a33.3 ± 7.7b
MIP (mm Hg)99.5 ± 32.9a86.3 ± 41.7a95.8 ± 38.7a

Of the 12 segments in each group, 3 were derived from each of 4 dogs.

Within a variable, different superscript letters denote a significant (P < 0.05) difference between groups.

Figure 2—
Figure 2—

Box-and-whisker plots of ILP determined during leak pressure testing of 36 fresh (tested within 4 hours after collection), chilled (stored at 4°C for 24 hours before testing), and frozen-thawed (stored at −20°C for 7 days and thawed at 21°C for 6 hours before testing) canine jejunal segments after enterotomy closure. Of the 12 segments in each group, 3 were derived from each of 4 dogs. Compared with findings for fresh and chilled segments, frozen-thawed segments leaked at significantly (P < 0.001 and P < 0.002, respectively) lower ILP. For each box, the horizontal line represents the median and the upper and lower boundaries represent the 75th and 25th percentiles, respectively. Whiskers represent the minimum and maximum values.

Citation: American Journal of Veterinary Research 81, 3; 10.2460/ajvr.81.3.220

Location of leakage in jejunal segments

Among the 3 experimental groups, there was no significant (P = 1.00) difference in leakage location. For all jejunal segments collectively, leakage was observed at the location of the preconstructed suture loop in 22 of 36 (61.1%) segments and from at least 1 suture hole in 14 of 36 (38.9%) segments. Leakage at the location of the preconstructed suture loop occurred in 8 of 12 fresh segments, 7 of 12 chilled segments, and 7 of 12 frozen-thawed segments. Leakage occurred at 1 or more suture holes in 4 of 12 fresh segments, 5 of 12 chilled segments, and 5 of 12 frozen-thawed segments. Visible leakage of colored solution did not occur from the closed incisional line during testing of any segment.

Enterotomy closure times

Mean ± SD time from the start to completion of enterotomy closure was 136.5 ± 8.7 seconds, 148.7 ± 20.8 seconds, and 135.3 ± 10.8 seconds for the fresh, chilled, and frozen-thawed segment groups, respectively. The duration of enterotomy completion did not differ significantly (P = 0.056) among groups.

Discussion

In the present study, the effect of storage conditions on intraluminal leakage pressure test results for canine jejunal segments with enterotomies that had been closed with barbed suture was evaluated. In support of our hypothesis, jejunal segments that underwent a single controlled freeze-thaw cycle and subsequent leak pressure testing of enterotomy sites closed with a unidirectional barbed suture had significantly lower ILP, compared with findings for tested fresh and chilled segments.

To date, there is a wide variety of protocols with differing conditions for storage of intestinal specimens prior to experimental testing. With regard to dogs, cadaveric tissues are commonly used to evaluate enterotomy closure techniques and for burst pressure studies.11,13,20,24,28 Specimens have been evaluated for leak pressure immediately following collection2,24 or within 4, 24, or 72 hours after collection.11,13,20,29 Temperature during storage of specimens has also varied with fresh,2,24 chilled (at 4°C),20 and frozen21 segments being used for experimental leak pressure assessments.

In canine intestinal segments, leakage from incisions closed with barbed suture material or equivalent-sized smooth monofilament suture material occurs at similar intraluminal pressures.13,29 In healthy dogs devoid of gastrointestinal tract disease, normal physiologic intraluminal pressures range from 15 to 25 mm Hg.26 In the present study, the mean ILP of the jejunal segments that underwent a single controlled freeze-thaw cycle was significantly lower than findings for fresh or chilled segments; this finding was in agreement with that of a recent study21 in which enterotomy leak pressures among fresh, cooled, and frozen-thawed porcine jejunal segments were evaluated. In the present study, mean ILP in the frozen-thawed segment group was 33 mm Hg (a value approx 60% of mean ILPs for the fresh and chilled segment groups), which was higher than the value reported for the frozen-thawed porcine jejunal segments.21 The discordance between the leakage pressures for the canine and porcine frozen-thawed segments may be explained by anatomic differences between species. The submucosal layer of porcine intestinal tissue is relatively thin, compared with that of the canine jejunum,14 which could have contributed to a lower mean leak pressure of 14.4 mm Hg for the frozen-thawed porcine jejunal segments in the study21 by Aeschlimann et al. The results of the present study were in agreement with the aforementioned study,21 and the lower ILPs recorded in tested frozen-thawed jejunal segments, compared with ILPs in fresh and chilled jejunal segments, may have been attributable to loss of the normal holding strength of the submucosal collagen that can occur with freezing. We speculated that destabilization of collagen fibrils as a result of intrafibrillar expansion by ice crystal formation may be the cause of the observed findings. To further elucidate these findings would necessitate undertaking studies involving calorimetric measurements combined with morphological examination of collagen matrices by scanning electron microscopy. Further research to help elucidate the duration of freezing that results in tissue degradation and a loss of functional integrity is required to allow outcome measures to be assessed and meaningful comparisons made among studies. Tissue changes and ice crystal formation associated with freezing likely alter the structural integrity, intestinal architecture, or suture holding capacity of the intestinal segments.

The canine alimentary tract is a low-pressure system under normal physiologic resting conditions; maximum jejunal intraluminal pressures in clinically normal dogs rarely exceed 40 mm Hg.30 In the present study, MIP did not differ significantly among the experimental groups. The lack of difference in MIP was likely attributable to the relatively high rate of fluid infusion into the lumen of the jejunal segments, which prevented leakage at the same flow rate through suture holes. In the present study, mean MIP in each experimental group was higher than reported in vivo pressures.30 In a previous resection and anastomosis study13 involving canine cadaveric small intestinal segments, mean ± SD MIP in segments that underwent anastomosis with barbed suture material placed in a simple continuous pattern was 185.2 ± 67.9 mm Hg. In a study21 to compare enterotomy site leak pressure among fresh, cooled, and frozen-thawed porcine jejunal segments, the maximal leakage pressure was 118.8 mm Hg; however, it should be noted MIP was not a variable of interest in that study. Differences in data obtained in the present study and other investigations may be related to the rate of fluid infusion used during testing of the intestinal segments. An infusion rate of 500 mL/h was used in the present study, whereas rates of 90021 and 99913 mL/h were used in other studies; the infusion rate differences could account for the differences in pressure measurements. The results of the present study were in agreement with findings of previous pressure studies involving similar fluid infusion techniques in dogs.15,24,26,31 However, another canine cadaveric study32 evaluating the effect of a surgical sealant on leakage pressures, ILP, and MIP of fresh canine cadaveric small intestinal anastomoses revealed significantly lower subphysiologic pressures. We concluded that the use of cadaveric tissue likely leads to changes in the ability of enterotomy sites to withstand increasing intraluminal pressures, compared with the ability of enterotomy sites in in vivo or in-situ assessments.24 The variability in MIP among studies may be attributable to different techniques of anastomosis, intestinal closure, or methods of pressure testing and has highlighted the need for species-specific research and assessment of procedural methods used for leak pressure testing studies.

When barbed sutures are created from a monofilament strand, barbs are cut directly into the suture core.16 The barbs extend out from the suture shaft itself, thereby having the potential to cause a greater degree of tissue trauma when used, compared with that resulting from use of smooth monofilament suture of an equivalent size. In the present study, the location of failure and fluid leakage along the enterotomy site closure did not differ among the 3 experimental groups. In 14 of the 36 (38.9%) fresh, chilled, and frozen-thawed jejunal segments, leakage occurred at 1 or more suture holes with mild serosal tearing circumferentially. Leakage locations in the present study were consistent with those of previous studies, in which needle penetration sites were identified as a common site of leakage in experiments involving similar methods of collection of fresh24 and chilled29 intestinal specimens. Temperature and duration of intestinal specimen storage may affect the tissue-suture interaction and may adversely affect the holding strength of submucosal tissues. Further focused investigation of the effect of storage conditions on intestinal segments from various species is warranted.

In the majority of jejunal segments (22/36 [61.1%]) in the present study, leakage occurred at the location of the preconstructed suture loop. After the barbed suturee needle passes through the preconstructed loop following the initial tissue bite and the next tissue bite is performed, the suture in position becomes effectively locked in place. On the suture line, a 14-mm-long section adjacent to the suture loop is devoid of barbs and likely represents a point of uneven tension distribution because this portion of the suture strand does not engage the surrounding tissue.33 Positioning the preconstructed end loop at a greater distance from the start of the enterotomy incision may allow barbs to engage along the entire length of the enterotomy closure. In another study of cadaveric canine urinary bladders,34 barbed suture material from the manufacturer of the barbed suture material used in the present study was used to close cystotomy sites, and the location of the preconstructed end loop was the most common site of closure failure leading to fluid exudation and leakage. Currently, there is no consensus regarding the optimal distance for placement of the initial suture bite from the incisional line when barbed suture material is used. Use of bidirectional barbed suture material may eliminate the observed pattern of leakage location because there is no preconstructed end loop required for this method of closure.35 It should also be noted that sutured enterotomy sites leak at pressures greater than those expected to cause clinically relevant failures.36

Limitations of this study were inherent to its study design and included the nonphysiologic method of testing and the use of cadaveric tissues wherein the suture-tissue interaction may behave differently, compared with that in tissues in vivo. Jejunal distensibility and burst pressure measurements may be different in dogs with infiltrative, neoplastic, or inflammatory intestinal disease, and the results of the present study would not be applicable to such clinical scenarios. All experiments were performed with Doyen intestinal forceps; however, in clinical cases, digital occlusion may be used with fingers positioned at a variable distance from the enterotomy site. In clinical scenarios, enterotomies may be reinforced with additional techniques such as omental wrapping or serosal patching,29 both of which have been shown to significantly increase ILP, compared with ILP following enterotomy closure alone. Adjunctive surgical techniques were not evaluated in the present study. Also, histologic assessment of the jejunal segments used in the present study was not performed because dogs were considered free of gross gastrointestinal tract disease on the basis of findings of visual inspection.

Results of the present study indicated that freezing and thawing of segments of canine jejunum may falsely decrease ILPs of enterotomy sites; thus, this storage method should not be used for leakage pressure testing of cadaveric specimens from this species.

To obtain reliable pressure data in future studies, it is recommended that cadaveric intestinal segments be tested immediately after collection or following chilling for ≤ 24 hours.

Acknowledgments

The authors declare no conflict of interest related to this study, nor was any financial support received.

The authors thank Jon Hash for assistance with cadaver specimen collection. All surgical suture was provided by Covidien Inc, Mansfield, Mass.

ABBREVIATIONS

ILP

Initial leakage pressure

MIP

Maximum intraluminal pressure

Footnotes

a.

Euthasol, Virbac AH Inc, Fort Worth, Tex.

b.

Vetivex Hartmann solution for injection, Dechra Veterinary Products, Overland Park, Kan.

c.

Random number generator, Research Randomizer, Lancaster, Pa. Available at: www.randomizer.org. Accessed Sep 12, 2019.

d.

Ziplock, SC Johnson & Son Inc, Racine, Wis.

e.

Polyglyconate, V-Loc 180 absorbable wound closure device (V-20 needle), Covidien Animal Health, Mansfield, Mass.

f.

Insyte, BD Vialon Material, Franklin Lakes, NJ.

g.

Methylene blue, Kordon LLC, Hayward, Calif.

h.

Lifeshield Primary Plumset, Hospira, Lake Forest, Ill.

i.

Plum A+, Hospira, Lake Forest, Ill.

j.

Logical, Smiths Medical, Dublin, Ohio.

k.

Passport 2, Mindray North America, Mahwah, NJ.

l.

Statistical software, Stata/SE, v.15.0, StataCorp, College Station, Tex.

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Contributor Notes

Address correspondence to Dr. Duffy (djduffy@ncsu.edu).