Since 2010, more than 158 patients with acute mesenteric ischemia have been administered in the ISC by a multidisciplinary stepwise management strategy, and a better outcome was achieved, as shown in previous reports[10, 16, 17]. However, in clinical practice and follow-up, we found that many patients with AMVT suffered from segmental intestinal stenosis in the long term, even though those patients successfully underwent mesenteric revascularization in the acute phase. Surprisingly, stenosis of the small bowel is rarely mentioned in reports of mesenteric venous thrombosis, suggesting that it may be a rare complication. In this large study, we evaluated 42 patients with PIIS secondary to AMVT and showed that the triad of abdominal pain, abdominal distention and vomiting was present in 55% of patients. In addition, hypoproteinemia and hypoalbuminemia were present in 62% of patients. Surprisingly, hypoproteinemia could not be corrected with prompt initial nutrition support and symptom alleviation can’t be achieved after conservative therapy in most cases. Ultimately, resection of the involved segmental intestine and postoperative nutrition resulted in a good general outcome, and the postoperative courses were uneventful in most patients.
Signs appear during the post-thrombotic course, and the main triad of symptoms, which indicates the appearance of chronic intestinal obstruction as a result of intestinal stenosis, mainly occurs several weeks after revascularization (it varies from several days to months). Ischemic intestinal stenosis does meet the diagnostic criteria of ischemic enteritis, which can also be related to limited thrombosis or embolism[19, 20]. However, in this research, we found that constant malnutrition with hypoproteinemia and hypoalbuminemia was another main clinical feature. In addition, Matsushita et al also demonstrated that it is a cause of protein-losing enteropathy (PLE) with the use of technetium 99 m-labeled human serum albumin scintigraphy. However, postprandial pain and intolerance to oral intake may be another cause of malnutrition. Thus, the term “postischemic intestinal stenosis” instead of “ischemic enteritis” was used in this research.
CT has been useful for the diagnosis of AMVT, as it produces a specificity of 90% and a sensitivity of 95%[5, 22]. It can evaluate the venous drainage of the portal venous system and exclude the possibility of thrombosis recurrence and the nonvascular findings can help assess intestinal ischemia. Segmental bowel wall thickening and bowel dilation are the main nonvascular findings, which indicates the appearance of bowel edema and the possibility of intestinal obstruction. Moreover, extensive collaterals are also found in most cases. Prompt revascularization and the development of sufficient collaterals ensure venous drainage from the involved ischemic bowels. However, in some cases, the collaterals might not be adequate for preventing segmental chronic bowel ischemia, which has been demonstrated in the histological examination of chronic inflammation in most resected specimens. A similar result was also found by Eugene et al who reported that intestinal strictures associated with mesenteric vein thrombosis were probably the consequence of ischemia. Interestingly, involvement of the colon has not yet been found, and the reason for this may be better collateralization of the colonic venous system, preventing chronic ischemia and therefore ischemic stenosis.
Barium examination is considered to be most useful for the diagnosis of ischemic enteritis. However, barium studies may be dangerous in cases of nearly complete obstruction, as it may become inspissated above the level of obstruction, or barium may spread into the peritoneal cavity if perforation occurs or is present. In this research, complete obstruction was found in 8 patients, and severe stenosis was also found in many patients. By contrast, gastrografin, a water-soluble contrast medium, can decrease edema of the bowel wall and enhance bowel motility, and it can be easily diluted by enteric fluid and can enhance mucosal details on radiography. Furthermore, water-soluble contrast medium of high osmolarity can accelerate the resolution of postoperative ileus and enhance the resolution of adhesive bowel obstruction[24, 25]. Positive findings of intestinal stenosis were found in all patients who underwent this test. The location of the involved intestine, which varies from the jejunum to the ileum, can be identified by the use of gastrografin, which has a beneficial effect on subsequent surgical interventions.
Stricture in ischemic enteritis sometimes tends to progressively worsen and ultimately results in total occlusion[15, 26]. Similar results may also occur in PIIS secondary to AMVT. The condition of 5 patients worsened from mild symptoms to severe abdominal pain during initial nutrition therapy. Moreover, the worsen of intestinal stenosis and the increase in leukocyte counts may also indicate the aggravation of intestinal ischemia and the initiation of a systemic inflammatory response[16, 27]. According to the comparison of enterography findings in these patients, we hypothesize that “mucosal erosion-stricture-complete obstruction” may also be the progression of PIIS secondary to AMVT to some extent. Thus, in the 4 patients who experienced symptom alleviation and were discharged after conservative treatment, close follow-up after discharge is still warranted and has already been carried out.
90.5% patients do not improve with conservative treatment and nutritional therapy. In contrast, postoperative nutrition therapy can effectively correct constant hypoproteinemia, and symptoms can improve after resection of the involved intestines. The postoperative course was uneventful in most patients. Thus, as patients may improve promptly with conservative management, it is better to perform surgery, and prompt surgical resection may lead to better outcomes. Surgical resection is also the main strategy of intestinal enteritis. An emerging role of balloon dilation for symptomatic intestinal stricture has also been reported and is considered to be a useful alternative to surgery when the length of the stricture is less than 3 cm. However, small bowel strictures that are long (> 3 cm) may not be candidates for balloon dilation, and the length of the involved intestine in PIIS secondary to AMVT was longer than 3 cm in most patients. Moreover, endoscopic balloon dilation of strictures carries a risk of perforation at rates of up to 2.9%. Therefore, the role of balloon dilation in PIIS secondary to AMVT should be further evaluated and warrants additional research in the future.
The main limitations of the study include its retrospective nature and the fact that the clinical data were limited in the records. Moreover, the diagnostic effect of endoscopy, especially capsule endoscopy, was not discussed, which allows for precise examination of the small intestine, and it could not be done due to non-availability in the research period. However, a prospective study is already in progress.