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Superior mesenteric artery occlusion in dogs: A model to produce the spectrum of intestinal ischemia
JOURNAL
OF SURGICAL
Superior
RESEARCH
19, 251-257
Mesenteric
to Produce
(1975)
Artery
Occlusion
the Spectrum
A. BONAKDARPOUR, M.D., N. ESSA, M.D.,
in Dogs:
of Intestinal
A Model
Ischemial
S. MING., M.D., P.R.LYNCH, AND F. REICHLE, M.D.
PH.D.,
Departments of Radiology, Pathology, Surgery, and Physiology, Temple University of Medicine, 3401 North Broad Street, Philadelphia, Pennsylvania 19140 Submitted
for publication
Intestinal &hernia in man results in a spectrum of clinical and pathological ranging from abdominal manifestations, angina without overt tissue damage to infarction of bowel and frequently the patient’s death (10, 22). Recent advances in vascular and gastrointestinal surgery have improved the survival of patients with intestinal ischemia if a diagnosis is made early (1, 8, 20, 22). More knowledge of the basic processes following this condition than currently available is needed, so that early diagnosis and appropriate management can be provided. A suitable animal model would offer the possibility of a systemic study Although under controlled conditions. several experimental studies (2, 4-7, 9, 11, 12, 14, 15, 18, 19, 21) have been reported, none produced conditions simulating the whole spectrum of intestinal ischemia from mildly decreased perfusion to frank bowel infarction. It is the purpose of this presentation to introduce an experimental model in dogs which can reliably produce various stages of intestinal ischemia by precisely determining the length and extent of ischemic segments. In such a model, not only the disease process can be studied, but new diagnostic and therapeutic approaches can be examined.
‘Supported by USPHS, Grants No. HL08886-1 I and HL14217. The authors thank Miss Beverly Bender for typing the manuscript and Mr. M. Hewish for preparation of the photographs.
251 Copyright o 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.
March
School
31, 1975
SURGICAL TECHNIQUE Forty-one mongrel dogs weighing from 17 to 20 kg were used in these experiments designed to produce a precise length of ischemic bowel. The animals were anesthetized by an intravenous injection of 32.5 mg of sodium pentobarbital per kg body weight. Thirty-six dogs had occlusion of the superior mesenteric arterial branches, and five dogs had sham operations without arterial ocelusion . Animals in which a branch of the mesenteric artery was occluded had a midline upper abdominal incision made through the linea alba. After the abdomen was opened, the greater omentum was carefully pushed aside. The cecum and terminal ileum were removed from the abdominal cavity for the inspection of their arterial distribution. The arteries were approached from the posterior aspect of the mesentery. By following the appropriate branches of the superior mesenteric artery from the small bowel, the feeding artery to a predetermined length of the intestine could readily be identified. After the point of occlusion was selected, a small incision was made in the mesentery, and the related artery and veins were dissected free. Extreme care was taken to keep the veins intact. A tie was looped around the artery to serve as a tourniquet which could be tightened to determine the length of the bowel rendered pulseless. The artery was then transected between two ligatures. The artery that had been temporarily occluded by the tourniquet began pulsating
252
JOURNAL
OF SURGICAL
RESEARCH
within a few minutes after tourniquet release. Thus the tourniquet could be relocated to obtain a specifically desired length of pulseless bowel. Occasionally the artery remained spastic and did not become pulsatile for 5-15 min. When this occurred, the initial site where the tourniquet was applied was chosen for ligature. The length of ischemic bowel was measured with a sterile ruler. After transection of the artery, the incision in the mesentery was closed with catgut suture. The two ends of pulseless bowel were marked with either metallic clips or black sutures. The bowel was replaced into the abdominal cavity. The greater omentum was reexpanded to cover the bowel. The abdominal wall was closed in three layers. Five-hundred milliliters of iv fluid was given during the operation. All of the dogs received IM injection of penicillin for several days. Various lengths of ischemic bowel (from 15-200 cm) were obtained. Five control dogs that had a sham operation had only an incision of the abdominal wall, exteriorization of the intestine, replacement of the bowel back into the abdominal cavity and closure of the abdominal wall without occlusion of any artery. Ten dogs died, and 17 dogs (16 occlusive and 1 control) were sacrificed from 24 hr to 25 months after occlusion in order to study the pathological changes. Histologic studies were made in these 27 dogs. Three to ten specimens of ischemic bowel were studied, depending on the length of the ischemic segment. The tissue was embedded in paraffin and the sections were stained with hematoxylin and eosin. The remaining 14 dogs (10 occlusive and 4 control) from the
VOL. 19, NO. 4, OCTOBER
1975
total of 41 experimental animals were autopsied, and the bowel was examined only grossly and photographed. RESULTS Arteries distal to the site of occlusion as well as adjacent marginal arteries became pulseless immediately after occlusion. The related portion of the small intestine became pale and developed abnormal contractions. The pulseless segment was readily distinguishable from the remaining normal bowel. In dogs that were sacrificed more than 1 week after operation the arterial pulse was found to have become reestablished gradually from the two ends of the pulseless bowel indicating the opening of collateral arterial channels. Although the bowel was viable, the central portion of the segments sometimes remained pulseless even after 1.5 months. Arterial branches immediately distal and adjacent to the site of transection remained pulseless permanently. Pathological Changesin Ischemic Bowel
The pathologic changes correlated with the length of ischemia (Table 1). All five control dogs showed normal bowel. One, dead in 24 hr, was examined microscopically and four were sacrificed 2-8 weeks after the sham operation. Bowel ischemia of 15-60 cm was produced in 11 dogs. None died. Two were sacrificed in 1 day and two in 3 days. The others were sacrificed after an observation period of 2 weeks to 25 months. Six dogs had histological studies. No gross abnormalities were present in any of these dogs, although
TABLE 1 Summary of Experimental Results Pathology Length of Ischemia (cm) 15-60 65-105 110-200
Number of dogs (days after operation) Operated
Died
Sacrificed
11 11 14
0 0 10 (l-6)
11 (l-760) 11(3-153) 4 (l-6)
Infarction 0 0 13
Mild to moderate damage
Normal
0 9 1
11 2 0
BONAKDARPOUR
ET AL.:
mild congestion in the villi was seen histologically in four dogs sacrificed in the first 3 days. Bowel ischemia of 65-105 cm was produced in 11 dogs. Histological studies were done on 10 dogs. None died. One dog sacrificed 3 days after operation showed mild mucosal congestion. Six dogs sacrificed 2-3 weeks after operation had varying degrees of mucosal necrosis, ulceration and submucosal granulation-tissue formation and fibrosis (Fig. 1). Two of these dogs also showed focal stenosis. Three dogs sacrificed l-2 months after operation showed focal mucosal atrophy and submucosal fibrosis. The remaining dog had grossly normal intestines when examined 5 months after operation. Bowel ischemia of 110-200 cm was produced in 14 dogs, 10 were examined histologically. Seven dogs died within 2 days, and one dog each died 3, 4 and 6 days after operation. Three dogs were sacrificed in 1 day and one in 1 week. All these 13 dogs had an infarcted bowel (Fig. 2). Hemorrhagic necrosis of mucosa was a common finding in the regions peripheral to areas of total infarction. The remaining dog had bowel ischemia of 117 cm and showed multiple linear ulcerations in the ischemic segment without infarction. DISCUSSION It is now well recognized that intestinal ischemia is a very complex phenomenon. It has multiple etiological factors and has a wide range of pathological and clinical manifestations (22). In recent years, ischemit lesions without overt infarction are increasingly being recognized. This condition is particularly important clinically because it is often reversible and responds to treatment (10, 22). In order to understand the problem of intestinal ischemia, many experimental studies have been reported, mostly in dogs. A variety of procedures have been used to investigate different aspects of the disease. Acute infarction has been produced in dogs by ligation of superior mesenteric artery
INTESTINAL
ISCHEMIA
253
near its origin (6, 12), ligation of a large artery (19), tying of both arteries and veins to an isolated segment for 8 hr (7, 19), transection of the mesentery and blood vessels to a blind loop (9), thrombosis of the superior mesenteric artery following electrocoagulation (14), and injection of lead pellets into mesenteric artery (15). Ulcerative and fibrotic lesions, mainly in the colon, have been produced in dogs in long-term experiments by the injection of glass microspheres into the arteries (2), perfusion of Tyrode solution through colonic arteries (5), tying of both arteries and veins to isolated segments for 47 hr (7), clamping colonic arteries for up to 3 hr (18) and ligation of small arteries to colon (11). Finally, hemorrhagic necrosis was produced in dogs by ligation of the superior mesenteric artery near its origin for 2 hr (21) and clamping of all arteries to a segment of the colon for 3 hr (18). None of these reports gave a single procedure to produce a spectrum of lesions comparable to the clinical situation observed in patients. The model reported here reproduced faithfully various stages and types of intestinal ischemia by a simple manipulation of varying the degree of mesenteric occlusion produced by ligation and transection of a selected mesenteric artery. The technique of arterial ligation to cause intestinal ischemia in dogs is neither new nor unique. It has been applied to a variety of reported experiments as already mentioned. It has been used primarily to produce acute lesions by ligating either the main artery for infarction of a long segment or the vasa recta for infarction of a short segment. This technique has been used to produce chronic ischemic lesions only in the colon by ligating the small arteries (11). Other techniques for this latter purpose were temporary occlusion of the blood vessels (7, 18), perfusion of Tyrode solution through colonic arteries (5), and injection of glass microsphere into the arteries (2). The last method is the only one reported to result in ulceration and fibrosis in the small bowel. The present model produced chronic lesions in the small
254
JOURNAL
OF
SURGICAL
RESEARCH
VOL.
19, NO.
4, OCTOBER
1975
FIG. 1. Bowel of a dog with ischemia of 95 cm of the bowel. The dog recovered from the operation and lived for 32 days. When sacrificed, arterial pulsation and collaterals were present at the margins of the involved bowel segment. (a) Mucosal view of the central portion of the ischemic segment showing linear ulceration along the long axis of the bowel. Thin regenerated mucosa covered both ends of the ulcerated area. The mucosa was otherwise normal. Omental adhesions were present on the serosa at this level. (b) Histological appearance of the ulcerated area showing loss of mucosa, inflammation at the base and granulation tissue in the submucosa. Muscularis was intact. x 110. (c) Histological appearance of bowel at the end of the ulcerated area showing regenerated, thin mucosa and submucosal granulation tissue which extended beyond the ulcerated area. x 110.
bowel when the ischemic segments were 65105 cm in length. The mesenteric arterial supply in dogs differs from that in man in that a terminal arcade is present near the mesenteric border of the bowel (13). This arcade allows collateral circulation sufficient to maintain the viability of the bowel when the arterial supply is interrupted for only a short segment (4). Thus, Demel, quoted by Derr (4), demonstrated that dogs were able to
survive ischemia of the intestine up to 40 cm in length, provided the arcuate vessels were intact. In the present model we have shown that occlusion of arteries feeding up to 105 cm of the intestine is compatible with survival. No abnormalities resulted when the ischemic segment was 60 cm or less. In man, occlusion of small mesenteric arteries has also been found to cause no intestinal disease (16, 17). When the ischemic segment in dogs was 65 cm or longer, a whole spectrum of
BONAKDARPOUR
ET AL.:
intestinal lesions comparable to that seen in man occurred. The causative mechanism of these changes is poorly understood in man, but clearly illustrated in this model. Ischemia of bowel lengths of 65- 105 cm is of particular importance since it caused significant but nonlethal damage. This last range is therefore suitable for the study of chronic ischemia. This model thus indicates that a substantial portion of the small bowel
INTESTINAL
ISCHEMIA
and associated vessels must be involved before survival is affected. The critical period for survival has been demonstrated, the first few days being the most important. The advantage of the dog as an experimental model is that this animal is large enough to allow studies similar to those performed in man, such as percutaneous angiographic examination and barium studies. Angiographic findings in 18 of these
256
JOURNAL
OF
SURGICAL
RESEARCH
VOL.
19, NO.
4, OCTOBER
1975
FIG. 2. Autopsy specimen of a dog, with ischemia of 130 cm of the bowel, which died 36 hr after surgery. Specimen shows black discoloration because of hemorrhage in the infarcted bowel. The attached mesentry is also discolored.
dogs have been reported (3). Although there are differences in the anatomy of the mesenteric arteries between man and dog (13) as mentioned above, the practical advantages of the dog over other experimental animals are so great that this animal will serve as an acceptable experimental model for intestinal ischemia. We believe that this easily reproducible model can reliably be used to study the various stages of the perplexing problem of intestinal ischemia from mild decreased perfusion to focal necrosis and ulceration and finally complete through-and-through infarction of the intestine. In such a reliable
model different physiologic, pharmacologic, diagnostic and therapeutic modes can be investigated for the important goal of solving the problem of intestinal ischemia which at present is difficult to recognize and complex to treat. SUMMARY A surgical model in dogs, which can reliably simulate the spectrum of changes seen in intestinal ischemia in man by varying the length and extent of ischemic bowel, is presented. Ischemia of a precise segment of bowel was produced by ligation and transection of a branch of superior mesenteric
BONAKDARPOUR
ET AL.: INTESTINAL
artery. Dogs with ischemia of 60 cm or less of the bowel survived, and the bowel showed no ischemic changes, whereas ischemia of 110 cm or more of the bowel was not compatible with survival and generally resulted in infarction. The intermediate group with ischemia of 65- 105 cm of the bowel revealed significant ischemic changes with ulceration and occasionally stricture formation.
1969.
Marston, A. Mesenteric arterial disease, the present position. Gut 8:203,1967. II. Marston, A., Marcuson, R. W., Chapman, M., and Arthur, J. F. Experimental study of devascularization of the colon. Gut 10:121, 1969. 12. Nelson, L. E., and Kremen, A. J. Experimental occlusion of the superior mesenteric vessels with special reference to the role of intravascular tbrombosis and its prevention by heparin. Surgery 28:819, 1950. 13.
14. 15.
Boley, S. J., Krieger, H., Schultz, L., Robinson, K., Siew, F. P., Allen, A. C., and Schwartz, S. Experimental aspects of peripheral vascular occlusion of the intestine. Surg. Gynecol. Obstet. 121:789, 1965. 3. Bonakdarpour, A. Angiography of mesenteric arterial occlusion. Invest. Radiol. S:316, 1970. 4. Derr, J. W., and Noer, R. J. Experimental mesenteric vascular occlusion. Surg. Gynecol. 2.
Obstet.
89:393,
J. Surg.
58:628,
1971.
9. Larson,N. E., Fleisher, G. A., Dearing, W. H., and Bollman, J. L. Certain plasma enzyme levels following experimental obstruction and infarction of segments of the small intestine. Surg. Forum 10:211,1959.
16.
17.
1949.
5. DeVilhers, D. R. Ischemia of the colon: An experimental study. Br. J. Surg. 53:497, 1966. 6. Ghanem, M., Goadale, R. C., Spanos, P., Tsung, M. D., and Wagensteen, D. H. Value of leukocyte counts in the recognition of mesenteric infarction and strangulation of shorter intestinal length: An experimental study. Surgery 68:634, 1970. 7. Glotzer, D. J., Villegas, A. H., Anekamaya, S., and Shaw, R. S. Healing of the intestine in experimental bowel infarction. Am. Surg. 155:183, 1962. 8. Jago, R. H. Superior mesenteric embolectomy. Br.
257
IO.
REFERENCES 1. Bergan, J. J. Recognition and treatment of superior mesenteric artery embolization. Geriatrics 24:118,
ISCHEMIA
18.
Noer, R. J. The blood vessels of the jejunum and ileum-a comparative study of man and certain laboratory animals. Am. J. Anat. 73:293, 1943. Phillips, J. F. Transcatheter electrocoagulation of blood vessels. Invest. Radiol. 8~295, 1973. Ranninger, K., and Scheiner, D. L. Experimental bowel ischemia. Arch. Surg. 95:768, 1967. Reiner, L., Rodriquez, F. L., Jimenez, F. A., and Platt, R. Injection studies of mesenteric arterial circulation-111. Occlusions without infarction. Arch. Pathol. 73:461, 1962. Reiner, L. Mesenteric vascular occlusion studied by postmortem injection of the mesenteric arterial circulation. In S. C. Sommers (Ed.), Pathology Annual, Vol. 1, pp. 193-220. Prentice-Hall, Englewood Cliffs, NJ. Robinson, J. W. L., Rausis, C., Basset, P., and Mirkovitch, V. Functional and morphological response of the dog colon to ischemia. Gut 13:775, 1972.
Vest, B., and Margulis, A. R. Experimental infarction of small bowel in dogs. Am. J. Roenrgenol. 92:1080, 1964. 20. Wagensteen, S. L., Golden, G. T., and Stapleton, S. L. Successful superior mesenteric embolectomy. 19.
Am.J. 21.
96:987, 22.
Surg.
123:601,1972.
Williams, L. F., Anastasia, L. F., Hasiotis, C. A., Bosniak, M. A., and Byrne, J. J. Experimental nonocclusive mesenteric ischemia. Arch. Surg. 1968.
Williams, L. F.: Vascular insufficiency of the intestines. Gastroenterology 61:757, 197 I,
OF SURGICAL
Superior
RESEARCH
19, 251-257
Mesenteric
to Produce
(1975)
Artery
Occlusion
the Spectrum
A. BONAKDARPOUR, M.D., N. ESSA, M.D.,
in Dogs:
of Intestinal
A Model
Ischemial
S. MING., M.D., P.R.LYNCH, AND F. REICHLE, M.D.
PH.D.,
Departments of Radiology, Pathology, Surgery, and Physiology, Temple University of Medicine, 3401 North Broad Street, Philadelphia, Pennsylvania 19140 Submitted
for publication
Intestinal &hernia in man results in a spectrum of clinical and pathological ranging from abdominal manifestations, angina without overt tissue damage to infarction of bowel and frequently the patient’s death (10, 22). Recent advances in vascular and gastrointestinal surgery have improved the survival of patients with intestinal ischemia if a diagnosis is made early (1, 8, 20, 22). More knowledge of the basic processes following this condition than currently available is needed, so that early diagnosis and appropriate management can be provided. A suitable animal model would offer the possibility of a systemic study Although under controlled conditions. several experimental studies (2, 4-7, 9, 11, 12, 14, 15, 18, 19, 21) have been reported, none produced conditions simulating the whole spectrum of intestinal ischemia from mildly decreased perfusion to frank bowel infarction. It is the purpose of this presentation to introduce an experimental model in dogs which can reliably produce various stages of intestinal ischemia by precisely determining the length and extent of ischemic segments. In such a model, not only the disease process can be studied, but new diagnostic and therapeutic approaches can be examined.
‘Supported by USPHS, Grants No. HL08886-1 I and HL14217. The authors thank Miss Beverly Bender for typing the manuscript and Mr. M. Hewish for preparation of the photographs.
251 Copyright o 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.
March
School
31, 1975
SURGICAL TECHNIQUE Forty-one mongrel dogs weighing from 17 to 20 kg were used in these experiments designed to produce a precise length of ischemic bowel. The animals were anesthetized by an intravenous injection of 32.5 mg of sodium pentobarbital per kg body weight. Thirty-six dogs had occlusion of the superior mesenteric arterial branches, and five dogs had sham operations without arterial ocelusion . Animals in which a branch of the mesenteric artery was occluded had a midline upper abdominal incision made through the linea alba. After the abdomen was opened, the greater omentum was carefully pushed aside. The cecum and terminal ileum were removed from the abdominal cavity for the inspection of their arterial distribution. The arteries were approached from the posterior aspect of the mesentery. By following the appropriate branches of the superior mesenteric artery from the small bowel, the feeding artery to a predetermined length of the intestine could readily be identified. After the point of occlusion was selected, a small incision was made in the mesentery, and the related artery and veins were dissected free. Extreme care was taken to keep the veins intact. A tie was looped around the artery to serve as a tourniquet which could be tightened to determine the length of the bowel rendered pulseless. The artery was then transected between two ligatures. The artery that had been temporarily occluded by the tourniquet began pulsating
252
JOURNAL
OF SURGICAL
RESEARCH
within a few minutes after tourniquet release. Thus the tourniquet could be relocated to obtain a specifically desired length of pulseless bowel. Occasionally the artery remained spastic and did not become pulsatile for 5-15 min. When this occurred, the initial site where the tourniquet was applied was chosen for ligature. The length of ischemic bowel was measured with a sterile ruler. After transection of the artery, the incision in the mesentery was closed with catgut suture. The two ends of pulseless bowel were marked with either metallic clips or black sutures. The bowel was replaced into the abdominal cavity. The greater omentum was reexpanded to cover the bowel. The abdominal wall was closed in three layers. Five-hundred milliliters of iv fluid was given during the operation. All of the dogs received IM injection of penicillin for several days. Various lengths of ischemic bowel (from 15-200 cm) were obtained. Five control dogs that had a sham operation had only an incision of the abdominal wall, exteriorization of the intestine, replacement of the bowel back into the abdominal cavity and closure of the abdominal wall without occlusion of any artery. Ten dogs died, and 17 dogs (16 occlusive and 1 control) were sacrificed from 24 hr to 25 months after occlusion in order to study the pathological changes. Histologic studies were made in these 27 dogs. Three to ten specimens of ischemic bowel were studied, depending on the length of the ischemic segment. The tissue was embedded in paraffin and the sections were stained with hematoxylin and eosin. The remaining 14 dogs (10 occlusive and 4 control) from the
VOL. 19, NO. 4, OCTOBER
1975
total of 41 experimental animals were autopsied, and the bowel was examined only grossly and photographed. RESULTS Arteries distal to the site of occlusion as well as adjacent marginal arteries became pulseless immediately after occlusion. The related portion of the small intestine became pale and developed abnormal contractions. The pulseless segment was readily distinguishable from the remaining normal bowel. In dogs that were sacrificed more than 1 week after operation the arterial pulse was found to have become reestablished gradually from the two ends of the pulseless bowel indicating the opening of collateral arterial channels. Although the bowel was viable, the central portion of the segments sometimes remained pulseless even after 1.5 months. Arterial branches immediately distal and adjacent to the site of transection remained pulseless permanently. Pathological Changesin Ischemic Bowel
The pathologic changes correlated with the length of ischemia (Table 1). All five control dogs showed normal bowel. One, dead in 24 hr, was examined microscopically and four were sacrificed 2-8 weeks after the sham operation. Bowel ischemia of 15-60 cm was produced in 11 dogs. None died. Two were sacrificed in 1 day and two in 3 days. The others were sacrificed after an observation period of 2 weeks to 25 months. Six dogs had histological studies. No gross abnormalities were present in any of these dogs, although
TABLE 1 Summary of Experimental Results Pathology Length of Ischemia (cm) 15-60 65-105 110-200
Number of dogs (days after operation) Operated
Died
Sacrificed
11 11 14
0 0 10 (l-6)
11 (l-760) 11(3-153) 4 (l-6)
Infarction 0 0 13
Mild to moderate damage
Normal
0 9 1
11 2 0
BONAKDARPOUR
ET AL.:
mild congestion in the villi was seen histologically in four dogs sacrificed in the first 3 days. Bowel ischemia of 65-105 cm was produced in 11 dogs. Histological studies were done on 10 dogs. None died. One dog sacrificed 3 days after operation showed mild mucosal congestion. Six dogs sacrificed 2-3 weeks after operation had varying degrees of mucosal necrosis, ulceration and submucosal granulation-tissue formation and fibrosis (Fig. 1). Two of these dogs also showed focal stenosis. Three dogs sacrificed l-2 months after operation showed focal mucosal atrophy and submucosal fibrosis. The remaining dog had grossly normal intestines when examined 5 months after operation. Bowel ischemia of 110-200 cm was produced in 14 dogs, 10 were examined histologically. Seven dogs died within 2 days, and one dog each died 3, 4 and 6 days after operation. Three dogs were sacrificed in 1 day and one in 1 week. All these 13 dogs had an infarcted bowel (Fig. 2). Hemorrhagic necrosis of mucosa was a common finding in the regions peripheral to areas of total infarction. The remaining dog had bowel ischemia of 117 cm and showed multiple linear ulcerations in the ischemic segment without infarction. DISCUSSION It is now well recognized that intestinal ischemia is a very complex phenomenon. It has multiple etiological factors and has a wide range of pathological and clinical manifestations (22). In recent years, ischemit lesions without overt infarction are increasingly being recognized. This condition is particularly important clinically because it is often reversible and responds to treatment (10, 22). In order to understand the problem of intestinal ischemia, many experimental studies have been reported, mostly in dogs. A variety of procedures have been used to investigate different aspects of the disease. Acute infarction has been produced in dogs by ligation of superior mesenteric artery
INTESTINAL
ISCHEMIA
253
near its origin (6, 12), ligation of a large artery (19), tying of both arteries and veins to an isolated segment for 8 hr (7, 19), transection of the mesentery and blood vessels to a blind loop (9), thrombosis of the superior mesenteric artery following electrocoagulation (14), and injection of lead pellets into mesenteric artery (15). Ulcerative and fibrotic lesions, mainly in the colon, have been produced in dogs in long-term experiments by the injection of glass microspheres into the arteries (2), perfusion of Tyrode solution through colonic arteries (5), tying of both arteries and veins to isolated segments for 47 hr (7), clamping colonic arteries for up to 3 hr (18) and ligation of small arteries to colon (11). Finally, hemorrhagic necrosis was produced in dogs by ligation of the superior mesenteric artery near its origin for 2 hr (21) and clamping of all arteries to a segment of the colon for 3 hr (18). None of these reports gave a single procedure to produce a spectrum of lesions comparable to the clinical situation observed in patients. The model reported here reproduced faithfully various stages and types of intestinal ischemia by a simple manipulation of varying the degree of mesenteric occlusion produced by ligation and transection of a selected mesenteric artery. The technique of arterial ligation to cause intestinal ischemia in dogs is neither new nor unique. It has been applied to a variety of reported experiments as already mentioned. It has been used primarily to produce acute lesions by ligating either the main artery for infarction of a long segment or the vasa recta for infarction of a short segment. This technique has been used to produce chronic ischemic lesions only in the colon by ligating the small arteries (11). Other techniques for this latter purpose were temporary occlusion of the blood vessels (7, 18), perfusion of Tyrode solution through colonic arteries (5), and injection of glass microsphere into the arteries (2). The last method is the only one reported to result in ulceration and fibrosis in the small bowel. The present model produced chronic lesions in the small
254
JOURNAL
OF
SURGICAL
RESEARCH
VOL.
19, NO.
4, OCTOBER
1975
FIG. 1. Bowel of a dog with ischemia of 95 cm of the bowel. The dog recovered from the operation and lived for 32 days. When sacrificed, arterial pulsation and collaterals were present at the margins of the involved bowel segment. (a) Mucosal view of the central portion of the ischemic segment showing linear ulceration along the long axis of the bowel. Thin regenerated mucosa covered both ends of the ulcerated area. The mucosa was otherwise normal. Omental adhesions were present on the serosa at this level. (b) Histological appearance of the ulcerated area showing loss of mucosa, inflammation at the base and granulation tissue in the submucosa. Muscularis was intact. x 110. (c) Histological appearance of bowel at the end of the ulcerated area showing regenerated, thin mucosa and submucosal granulation tissue which extended beyond the ulcerated area. x 110.
bowel when the ischemic segments were 65105 cm in length. The mesenteric arterial supply in dogs differs from that in man in that a terminal arcade is present near the mesenteric border of the bowel (13). This arcade allows collateral circulation sufficient to maintain the viability of the bowel when the arterial supply is interrupted for only a short segment (4). Thus, Demel, quoted by Derr (4), demonstrated that dogs were able to
survive ischemia of the intestine up to 40 cm in length, provided the arcuate vessels were intact. In the present model we have shown that occlusion of arteries feeding up to 105 cm of the intestine is compatible with survival. No abnormalities resulted when the ischemic segment was 60 cm or less. In man, occlusion of small mesenteric arteries has also been found to cause no intestinal disease (16, 17). When the ischemic segment in dogs was 65 cm or longer, a whole spectrum of
BONAKDARPOUR
ET AL.:
intestinal lesions comparable to that seen in man occurred. The causative mechanism of these changes is poorly understood in man, but clearly illustrated in this model. Ischemia of bowel lengths of 65- 105 cm is of particular importance since it caused significant but nonlethal damage. This last range is therefore suitable for the study of chronic ischemia. This model thus indicates that a substantial portion of the small bowel
INTESTINAL
ISCHEMIA
and associated vessels must be involved before survival is affected. The critical period for survival has been demonstrated, the first few days being the most important. The advantage of the dog as an experimental model is that this animal is large enough to allow studies similar to those performed in man, such as percutaneous angiographic examination and barium studies. Angiographic findings in 18 of these
256
JOURNAL
OF
SURGICAL
RESEARCH
VOL.
19, NO.
4, OCTOBER
1975
FIG. 2. Autopsy specimen of a dog, with ischemia of 130 cm of the bowel, which died 36 hr after surgery. Specimen shows black discoloration because of hemorrhage in the infarcted bowel. The attached mesentry is also discolored.
dogs have been reported (3). Although there are differences in the anatomy of the mesenteric arteries between man and dog (13) as mentioned above, the practical advantages of the dog over other experimental animals are so great that this animal will serve as an acceptable experimental model for intestinal ischemia. We believe that this easily reproducible model can reliably be used to study the various stages of the perplexing problem of intestinal ischemia from mild decreased perfusion to focal necrosis and ulceration and finally complete through-and-through infarction of the intestine. In such a reliable
model different physiologic, pharmacologic, diagnostic and therapeutic modes can be investigated for the important goal of solving the problem of intestinal ischemia which at present is difficult to recognize and complex to treat. SUMMARY A surgical model in dogs, which can reliably simulate the spectrum of changes seen in intestinal ischemia in man by varying the length and extent of ischemic bowel, is presented. Ischemia of a precise segment of bowel was produced by ligation and transection of a branch of superior mesenteric
BONAKDARPOUR
ET AL.: INTESTINAL
artery. Dogs with ischemia of 60 cm or less of the bowel survived, and the bowel showed no ischemic changes, whereas ischemia of 110 cm or more of the bowel was not compatible with survival and generally resulted in infarction. The intermediate group with ischemia of 65- 105 cm of the bowel revealed significant ischemic changes with ulceration and occasionally stricture formation.
1969.
Marston, A. Mesenteric arterial disease, the present position. Gut 8:203,1967. II. Marston, A., Marcuson, R. W., Chapman, M., and Arthur, J. F. Experimental study of devascularization of the colon. Gut 10:121, 1969. 12. Nelson, L. E., and Kremen, A. J. Experimental occlusion of the superior mesenteric vessels with special reference to the role of intravascular tbrombosis and its prevention by heparin. Surgery 28:819, 1950. 13.
14. 15.
Boley, S. J., Krieger, H., Schultz, L., Robinson, K., Siew, F. P., Allen, A. C., and Schwartz, S. Experimental aspects of peripheral vascular occlusion of the intestine. Surg. Gynecol. Obstet. 121:789, 1965. 3. Bonakdarpour, A. Angiography of mesenteric arterial occlusion. Invest. Radiol. S:316, 1970. 4. Derr, J. W., and Noer, R. J. Experimental mesenteric vascular occlusion. Surg. Gynecol. 2.
Obstet.
89:393,
J. Surg.
58:628,
1971.
9. Larson,N. E., Fleisher, G. A., Dearing, W. H., and Bollman, J. L. Certain plasma enzyme levels following experimental obstruction and infarction of segments of the small intestine. Surg. Forum 10:211,1959.
16.
17.
1949.
5. DeVilhers, D. R. Ischemia of the colon: An experimental study. Br. J. Surg. 53:497, 1966. 6. Ghanem, M., Goadale, R. C., Spanos, P., Tsung, M. D., and Wagensteen, D. H. Value of leukocyte counts in the recognition of mesenteric infarction and strangulation of shorter intestinal length: An experimental study. Surgery 68:634, 1970. 7. Glotzer, D. J., Villegas, A. H., Anekamaya, S., and Shaw, R. S. Healing of the intestine in experimental bowel infarction. Am. Surg. 155:183, 1962. 8. Jago, R. H. Superior mesenteric embolectomy. Br.
257
IO.
REFERENCES 1. Bergan, J. J. Recognition and treatment of superior mesenteric artery embolization. Geriatrics 24:118,
ISCHEMIA
18.
Noer, R. J. The blood vessels of the jejunum and ileum-a comparative study of man and certain laboratory animals. Am. J. Anat. 73:293, 1943. Phillips, J. F. Transcatheter electrocoagulation of blood vessels. Invest. Radiol. 8~295, 1973. Ranninger, K., and Scheiner, D. L. Experimental bowel ischemia. Arch. Surg. 95:768, 1967. Reiner, L., Rodriquez, F. L., Jimenez, F. A., and Platt, R. Injection studies of mesenteric arterial circulation-111. Occlusions without infarction. Arch. Pathol. 73:461, 1962. Reiner, L. Mesenteric vascular occlusion studied by postmortem injection of the mesenteric arterial circulation. In S. C. Sommers (Ed.), Pathology Annual, Vol. 1, pp. 193-220. Prentice-Hall, Englewood Cliffs, NJ. Robinson, J. W. L., Rausis, C., Basset, P., and Mirkovitch, V. Functional and morphological response of the dog colon to ischemia. Gut 13:775, 1972.
Vest, B., and Margulis, A. R. Experimental infarction of small bowel in dogs. Am. J. Roenrgenol. 92:1080, 1964. 20. Wagensteen, S. L., Golden, G. T., and Stapleton, S. L. Successful superior mesenteric embolectomy. 19.
Am.J. 21.
96:987, 22.
Surg.
123:601,1972.
Williams, L. F., Anastasia, L. F., Hasiotis, C. A., Bosniak, M. A., and Byrne, J. J. Experimental nonocclusive mesenteric ischemia. Arch. Surg. 1968.
Williams, L. F.: Vascular insufficiency of the intestines. Gastroenterology 61:757, 197 I,