Superior mesenteric artery bypass for chronic mesenteric ischaemia: a DGH experience

Introduction Patients and methods Results

Discussion References

This article evaluates the results of single vessel bypass surgery for symptomatic chronic mesenteric ischaemia (CMI) in 6 patients undergoing a total of 8 superior mesenteric artery (SMA) bypass operations, all with good post-operative symptom relief. Post-prandial pain and weight loss was present in 5 out of 6 patients. Epigastric bruit was present in only two patients and 4 out of 6 patients had diarrhoea. The patients had varying degrees of peripheral vascular disease, ischaemic heart disease and hypertension. All patients had occlusion of the SMA on angiography and bypassing the occluded segment resulted in disappearance of the symptoms and weight gain. The vascular graft was sutured end to side to the front of the infra-renal aorta and end to side to the SMA, distal to the origin of the middle colic artery. Two patients had recurrence of symptoms due to graft occlusion at 3 and 4 years, respectively; they were successfully treated with repeat SMA bypass. There were no major complications or deaths related to the procedure in this study; one patient developed an incisional hernia requiring elective repair. Thus, early restoration of SMA circulation by bypass grafting in patients with CMI is sufficient to alleviate symptoms and prevent intestinal infarction with its high mortality rate.

Keywords: intestinal angina, intestinal ischaemia, visceral artery occlusion

J.R.Coll.Surg.Edinb., 45, October 2000, 285-287

INTRODUCTION

Chronic mesenteric ischaemia (CMI) is an uncommon but potentially lethal problem. The modern era in management of CMI began in 1950, with Klass' application of the recently developed principles of vascular surgery to superior mesenteric ischaemia (SMA) embolism.¹ Up to that time, diagnosis was considered 'early' if it was made before the patient became moribund, allowing for resection of the infarcted bowel and possible survival. Klass (1951) introduced the concept of returning the blood flow to ischaemic but viable bowel and, of equal importance, the concept of making a diagnosis before infarction had occurred. In 1958, Shaw and Maynard² reported the first successful thrombo-endarterectomy for CMI. In 1957, Mikkelsen³ coined the term "Intestinal Angina" to describe the symptom complex of post-prandial pain, weight loss and altered intestinal motility. Because of multiple potential sources of collateral flow, at least 2-3 major vessels must be occluded or have critical stenosis for mesenteric ischaemia to ensue. However, the concept of CMI remains controversial because at autopsy some patients have evidence of stenosis of all three splanchnic arteries without abdominal symptoms.⁴Autopsy series of unsuspected patients have found significant stenoses in approximately 50% of coeliac axes, and 30% of superior and inferior mesenteric arteries.⁵

The purpose of this article is to briefly review the clinical presentation and diagnosis and to evaluate the results of 8 SMA bypass procedures in 6 patients presenting with CMI. Current opinion on the diagnosis and management of these patients is also discussed.

PATIENTS AND METHOD

Between 1982 and 1994, 6 patients presented with symptomatic CMI. A total of 8 SMA bypass operations were performed successfully by one vascular surgeon. The case records of these patients were retrospectively analysed to present our experience of this uncommon condition in a District General Hospital (DGH). The grafting procedure was regarded as successful and the graft patent if the patient remained symptom free on follow-up.

The infra-renal abdominal aorta was exposed and a lateral occlusion clamp applied. A length of saphenous vein, harvested from the thigh, was sutured end to side to the front of the aorta. The vein was then positioned in a long curving course up and over the duodeno-jejunal junction and down onto the front of the small bowel mesentery where it was anastomosed end to side to the SMA, distal to the origin of the middle colic artery. In one patient, with a blocked graft, the second bypass procedure was carried out between SMA and right common iliac artery. In the second patient with a blocked graft, the second bypass procedure was carried out using a 6 mm Gore-Tex graft.

RESULTS

Six patients presented with CMI, 5 were female and one male. The age of the patients varied from 41 to 81 years. Table 1 shows the duration and distribution of symptoms in the six patients in this series. The duration of the symptoms ranged from 3 to 66 months. Most patients presented with typical symptoms of post-prandial pain (5/6) and weight loss (5/6). Two patients with blocked grafts had recurrence of the same symptoms. One patient (Table 1 (6a)), who had a second graft carried out, occluded this graft after 2 years. His symptoms disappeared following trans-luminal angioplasty of his stenotic coeliac artery. Angiography was performed in all the patients to confirm the diagnosis. Findings of angiography are presented in Table 1. All patients had an occluded SMA; the coeliac artery (CA) was stenosed in 3 patients and occluded in one. There were no major complications or deaths related to the procedure in this study; one patient developed an incisional hernia, which required elective repair. Four patients are still alive and asymptomatic. One patient died of a myocardial infarct and one patient died of severe pancreatitis, 7 yrs and 3 yrs after the bypass operation, respectively. Duration of follow-up ranged from 2 to 11 years.

Table 1: Duration and distribution of symptoms and angiographic findings in patients. CA: coeliac axis; SMA: superior mesenteric artery; IMA: inferior mesenteric artery; P: patent; S: stenosed; O: occluded; 5/5a, 6/6a: repeat surgical procedures

Table 2: Long term outcome and follow-up of the patients

DISCUSSION

No accurate estimate of the incidence of CMI in a general population is available. The natural history of mesenteric ischaemia is poorly defined. Occlusive disease of the mesenteric arteries is almost always part of a generalised atherosclerotic process. Despite the high frequency of mesenteric atherosclerosis, most such patients are asymptomatic due to the highly efficient mesenteric collateral circulation. The natural history of symptomatic patients is better defined. Without intervention, such patients develop severe protein-calorie malnutrition and may progress to visceral infarction. Thus, urgent revascularisation is indicated in all symptomatic patients. The typical presentation is characterised by post-prandial abdominal pain, epigastric bruit and weight loss. This characteristic triad, however, can be incomplete or absent. Post-prandial pain is the pathognomic symptom of CMI. Pain occurs within 1 hour after eating and diminishes one to 2 hours later. The most common physical sign of CMI is weight loss due to "food fear" in anticipation of pain. One-third of the patients may have nausea and/or vomiting, diarrhoea or constipation. Early diagnosis of CMI is a continuing problem because physical and roentgenographic findings are non-specific. Patients are generally investigated in the first instance by ultrasonography, CT scan, endoscopy or barium studies to rule out more common causes of abdominal pain. Duplex scanning⁵  accurately identifies high-grade stenosis in the SMA and CA and is recommended as an early non-invasive screening procedure for patients with symptoms suggestive of CMI. It can also be used for post-operative surveillance of SMA revascularisation. SMA and CA peak systolic velocity on duplex scan demonstrates a linear relationship with angiographic stenosis; a 50% stenosis can be predicted with an overall sensitivity of 94% and specificity of 84%.⁶ Selective arteriography is critical to confirm the diagnosis of CMI as well as aid in planning revascularisation. Involvement of two mesenteric vessels is an indication of CMI. More than 85% of cases involve the CA and SMA; however, patients can be symptomatic from an isolated SMA occlusion. At the present time, surgical revascularisation remains the treatment of choice for most patients presenting with clinical symptoms and angiographic evidence of CMI. The entire spectrum of vascular reconstructive techniques, including bypass, ^7,8 endarterectomy,⁹ reimplantation¹⁰ and angioplasty^11,12 has been used to improve blood flow in the mesenteric vessels. Controversy continues as to the preferred technique for revascularisation, as few surgeons have more than an anecdotal experience in treating these patients. The results of the various revascularisation techniques are generally satisfactory and quite comparable. The precise choice of operation depends not only on the particular clinical circumstances but also on the judgement and experience of the operating surgeon. Despite strong institutional preferences, no prospective randomised clinical trial has clearly documented superiority of any single revascularisation technique. Life table analysis confirm that 75 to 86% of these high risk patients are alive 3 years following operation.^8,13 Multi-vessel reconstruction for CMI is superior to single vessel reconstruction in preventing recurrence of symptoms,¹⁴ as suggested in a large series by Pokrovsky and Kasantchjan (1980). Between 1977 and 1996, 272 cases were published in the literature from various studies with a mean follow-up of 5.2 years clinical failure was noted in 18% of cases with single vessel reconstruction, compared with 13.6% for two to three vessel reconstruction.¹⁵ Hollier et al (1981) concluded that early symptomatic relief occurred regardless of the number of vessels reconstructed, but that compared with more extensive revascularisation long-term patency was poorer in patients who had only one vessel reconstructed.¹⁶ In our experience this is not true for single vessel reconstruction, as we have had good long-term symptomatic relief ranging from 3 to 11 years.

We conclude that SMA bypass remains the treatment of choice for patients with CMI. Diagnosis, though difficult to make, should be strongly suspected in patients presenting with abdominal pain and unexplained weight loss.

REFERENCES

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Copyright date: 19th July 2000

Correspondence: Mr R.C. Smith, Department of General and Vascular Surgery, Ward 9 Office, Falkirk and District Royal Infirmary, Falkirk FK1 5QE, U.K.

©2000 The Royal College of Surgeons of Edinburgh, J.R.Coll.Surg.Edinb.