Vascularity of Gastrointestinal Staple Lines Demonstrated

With Silicone Rubber Injection

Craig R. Smith, MD, Rochester, New York

Giles Ft. Cokelet, ScD, Rochester, New York

James T. Adams, MD, Rochester, New York

Seymour I. Schwartz, MD, Rochester, New York

Advocates of gastrointestinal stapling devices maintain that the B configuration of the closed staple minimizes interference with circulation across the stapled area, implying that this allows better vascu- larity than that attainable with suture techniques [I ,2]. However, this has never been documented ei- ther experimentally or clinically. Such proof could be a strong endorsement for the routine use of staple instruments for bowel anastomosis. The present study assesses the vascularity of stapled anastomosis using a silicone rubber injection technique and demonstrates objectively that the circulation across a gastrointestinal staple line is not compromised.

Material and Methods

The study was done in adult mongrel dogs. After satis- factory pentobarbital anesthesia, celiotomy was performed and the small intestine mobilized. At sites selected for stapling, an opening just large enough to admit the tip of the stapler was made through an avascular area in the mesentery near the mesenteric border of the intestine. Each stapler was applied transversely or obliquely across the bowel with sufficient length passed through the mes- enteric opening to ensure that no undivided tissue re- mained beyond the end of the staple line. Multiple stapler applications were made in each dog.

TA-55 and GIA Auto Suture@ staplers (United States Surgical Corporation, Norwalk, Connecticut) were used. The TA-55 stapler produces a double staggered row of staples 53 mm in length, with a choice of two staple sizes. The GIA stapler produces two parallel double staggered rows of staples separated by 4 mm of tissue through which the dividing knife blade passes when that is part of the loading unit assembly. Three types of standard disposable

From the Department of Surgery and the Department of Radiation Biology and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York.

Requests for reprints should be addressed to James T. Adams, MD, De- partment of Surgery, University of Rochester School of Medicine and Den- tistry, Rochester, New York 14642.

loading units were used. Two staple sizes, loading units 55-3.5 and 55-4.8, were used in the TA-55 instrument. No difference between them was discernible in the vascularity of the completed specimens, and results are not presented separately. Only the SGIA loading unit, which does not contain a dividing knife, was used in the GIA stapler. Pertinent specifications of each loading unit used are summarized in Figure 1. The manufacturer cautions that tissue compressing to less than 1.5 mm for the 3.5 mm staple, and to less than 2.0 mm for the 4.8 mm staple may prevent tight enough closure to ensure adequate hemo- stasis. This limit was not approached in our specimens.

After a suitable number of staple rows had been created in the small intestine, appropriate branches of the superior mesenteric artery and accompanying veins were cannu- lated. Mesenteric arterial back-pressure was measured as a reference point for injection pressure. Silicone rubber injection compound (Microfilm) which had been freshly prepared according to the manufacturer’s specifications was injected through the arterial cannula until a continuous venous return free of air bubbles was obtained. Injection pressure was monitored and maintained in a physiologic range. To emphasize larger vessels, in some specimens the injection was stopped before capillary filling occurred. In such cases, the venous side of the circulation was filled through the venous cannula. Once suitable filling was ob- tained, all vessels were ligated and the segment of intestine removed. The specimens were cleared using a standard alcohol-methyl salicylate clearing sequence, without prior fixation in formalin. All of the cleared specimens were ex- amined under a dissecting microscope, and microdissection was performed as necessary. Photomicrographs of repre- sentative specimens were obtained at selected magnifica- tions with the specimens submerged in methyl salicy- late.

Results

Figure 2 shows complete vascular casts of small intestinal villi, demonstrating the high degree of capillary filling and anatomic fidelity obtainable with silicone rubber injection. Figure 3 shows a TA-55

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Smith et al

4mm

OPEN STAPLE f-H leg length

4mm

CLOSED STAPLE m 1 closed height (Varies slightly with tissue thickness)

LOADING UNIT: 55-3.5 55-4.8 SGIA ---

leg length (mm) 3.5 4.8 4.0

wire diameter (mm) 0.23 0.28 0.20 closed height (mm) 1.5 2.0 1.75

row length (mm) 53 53 52

Figure 1. Loading unit specifications.

staple line at the mesenteric border, where a rich network of vessels can be seen surrounding the sta- ples. To preserve this pattern, microdissection in this specimen was limited to the amount necessary to reveal a single larger deep vessel, approximately 0.3 mm in diameter, passing through the staple line.

Figure 4 shows vessels as large as 0.8 mm in di- ameter intertwining through two parallel double staggered rows of staples, again at the mesenteric edge of the bowel. This configuration was produced using the GIA stapler with the SGIA loading unit, which does not divide the tissue between the staple rows. Capillary filling was not obtained in this and similar specimens, which highlights larger vessels with a minimum of potentially distorting.microdis-

Figure 3. Mesenterlc edge of canine small Intestine after con- struction of a TA-55 staph llne using the 55-4.8 loadktg unit, fol- lowed by slllcone rubber InjectIon and tissue clearing. Microdis- section was limited to show a skrgle large vessel pas&g through the staples (arrow), preserving the rich small vessel network visible around the staples. ( MagnlflcatrOn X 20, reduced 42 per- cent.)

section. Figure 5 shows a TA-55 specimen similar in preparation to that shown in Figure 4. The remark- able finding is that staple closure was sufficiently atraumatic that one vessel, 0.3 mm in diameter, was pinched squarely by the staple end but reformed intact on either side of the staple without any evi- dence of extravasation.

Figure 6 shows the serosal surface of an undis- sected specimen in which capillary filling was ob- tained after application of the GIA stapler without

Figure 2. Cross-section of canine small Intestlne after Injection with sIllcone rubber and tissue clearing, showlng the capillary microstructure of the lntestkral vllll. ( Magn~atlon X 20, reduced 40 percent. )

Figure 4. Mesenterlc edge of canine small Intestine In which an undlvkted GIA staple llne had been placed before slllcone rubber in~ectlon and tissue clearing. The stapler tip was passed through the avascular space vlslble In the upper left hand corner. To hlghllght larger vessels, capillary fllllng was not obtalned. ( Mag- nification X 8, reduced 48 percent.)

564 The American Journal of Surgery

Vascularity of Gastrointestinal Staple Lines

Figure 5. Specimen simiiar in preparation to the one shown in Figure 4, except that the staple line was placed with the TA-55 stapler containing a 55-4.8 loading unit. The vessel in the center of the field reforms intact around the end of the closed staple. The staple wire diameter is 0.28 mm. (Magnification X 15, reduced 42 percent. )

division between the staple rows. Because the stapler was applied with the end passing through an avas- cular hole in the mesentery, vascular filling between the two staple rows can only occur by way of vessels passing through one of the two double rows of staples. The extensive network of vessels clearly visible be- tween the two double rows of staples is qualitatively indistinguishable from that visible in the tissue on either side of the staple rows. This confirms that the staple line interferes very little with vessels passing through it.

Comments

The increasing popularity of gastrointestinal sta- plers is a result of several advantages they provide, the best document of which is a reduction in opera- tive time [3-61. In one series of 455 cases, stapler procedures required one fourth the time required for conventional procedures 141. It has also been sug- gested that the incidence of perioperative sepsis is reduced with the staple technique [5] and that res- olution of postoperative ileus is more rapid.[3]. The healing of stapled anastomoses was studied grossly and microscopically in dogs, and uniformly demon- strated a secure and durable result [1,7]. Clinically, when the incidence of postoperative complications after 472 stapled anastomoses and 269 sutured an- astomoses was compared, no significant difference was found [8].

Rich vascularity of the staple line is a frequently cited virtue of stapler procedures which has not been shown experimentally. Ravitch [2] stated that the B configuration of the closed staple “allows small blood vessels to pass through the openings,” and speculated on the advantage this offered to the viability of du-

Figure 6. Serosai surface of an undissected specimen in which an undivided GiA staple line was placed before silicone rubber Injection and tissue clearing. The vascuiarity of the 4 mm zone of tissue between the staple lines is indistinguishable from that of the tissue on efther side. (Magnification X 75, reduced .33 percent. )

odenal stump tissue lying beyond the staple line. Not until the present report, however, has the vascularity across the staple line actually been demonstrated, and it is now clear that the configuration of the closed staple allows vessels of substantial size to pass through.

One implication of our findings is that significant bleeding might be expected from vessels distal to the staple line which have been divided but not occluded by the staples. In fact, this has been observed clini- cally and experimentally [5,7,8], although an in- creased incidence of bleeding complications has yet to be confirmed in clinical series [3,8]. Presumably the bleeding comes from small vessels. which, in ag- gregate, might benefit healing, but are rarely large enough to produce major hemorrhage. Nonetheless, careful inspection of staple lines for hemostasis is strongly emphasized in descriptions of the stapler technique, and this appears appropriate.

Our findings do not imply that staplers cannot be used to control large vessels, and in fact they have been used quite successfully for that purpose. Their use in the closure of atriotomy incisions [9] and in the closure of Potts anastomoses [IO] has been described. Staple closures have been shown to produce bron- chial stump closures with air leakage pressures greater than that of sewn closures [ 111, and their use in lung parenchyma has been associated in some se- ries with less blood loss and air leak than suture techniques [12,13]. Although we have not applied the silicone injection technique to intrathoracic organs,

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Smith et al

it seems reasonable to speculate that small vessels of staple lines was clearly demonstrated. The B con- the vasa vasorum and bronchial arterial system figuration of the closed staple allows blood vessels of would pass through the staple lines, as they do in the substantial size to pass through it. This might make intestine, even with the larger conduit securely staple technique especially advantageous whenever closed. vascularitv is critical.

Our findings also imply that the practice of cleaning the mesenteric bowel edge several milli- meters from the divided end, which is often done for suture anastomosis, is not desirable with the staple technique. Removing these attachments does not improve the secure application of the stapler, and would eliminate vessels which can wind through the staple line to supply tissue distal to the staples, ex- actly where vascularity is most crucial. Although it was shown experimentally with lampblack injections that baring the mesenteric bowel edge for 7 to 8 mm before constructing inverted sewn anastomoses did not affect circulation at the suture line [14], the op- portunity to preserve these vessels would make sta- pler technique especially advantageous whenever vascularity is critical.

It should be emphasized that the results presented here do not compare the vascularity obtainable with staple technique to that obtainable with suture technique. Relatively crude methods have been used in the past to analyze the vascularity of inverted and everted sewn anastomoses, with inconclusive and contradictory results [14-161. The vascularity of in- verted and everted stapled anastomoses has never been compared, and stapled anastomoses in either configuration have never been compared with their counterparts constructed with suture technique. It is tempting to speculate that stapled anastomoses place a greater number of small vessels in closer ap- proximation than is possible with suture technique, and that this would accelerate the capillary cross- bridging which occurs in the early stages of healing. Further experiments with the silicone rubber injec- tion technique may shed light on this assumption.

Summary

Gastrointestinal stapling devices were applied across canine small intestine, and then the blood supply of the stapled segments was immediately filled with silicone rubber. After tissue clearing and microdissection, the outstanding vascularity of the

Acknowledgment: Valuable technical assistance was provided by Jerome F. Flaherty.

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