In gastrointestinal practice, patients often present with symptoms of partial bowel obstruction. The examination of these patients involves cross-sectional imaging, which frequently shows small bowel strictures. These patients may have clinical features that indicate a particular disease or concomitant imaging findings such as mass lesions or adjacent lymph nodes, which may lead to a diagnosis. However, other diagnostic clues are rare. The presence of single or multiple small bowel strictures without mass lesions, colonic involvement, and mesenteric or retroperitoneal lymphadenopathy may be due to diverse causes. Only a few studies evaluated the etiology of small bowel strictures and suggested other causes for this condition, including NSAIDs-related diaphragmatic disease, ischemic stricture, and malignancy.^1,2,3,4 However, in the absence of the intake of NSAIDs, most clinicians limit the differentiation to CD and intestinal tuberculosis (ITB). ITB is an important cause of strictures, especially in endemic countries such as India. ITB occurs mainly in the terminal ileum and ileo-cecal junction but can also occur in the proximal small bowel. CD is an important cause of small bowel strictures and is being diagnosed more often even in countries endemic for tuberculosis.^5,6 Because of the absence of diagnostic clues in small bowel strictures, patients are often treated with anti-tubercular therapy (ATT), which has adverse effects, or steroids in cases of inadequate response to ATT. In the absence of such data, the treating clinician is confronted with a dilemma: to choose between surgical confirmation of diagnosis or empirical medical therapy for common causes, including ITB and CD. Therefore, it is important to differentiate common causes of strictures (such as ITB and CD) from rare etiologies, especially malignancy, because this differentiation can lower the threshold for surgical resection. Therefore, we retrospectively analyzed the records of all patients who underwent surgery for single or multiple small bowel strictures at a tertiary care center in northern India over the past 15 years and did not have a definitive preoperative diagnosis.

Patients presenting with recurrent abdominal pain or intestinal obstruction often have evidence of isolated small bowel strictures on imaging. Of these, many patients have classic clinical or imaging features that allow a definite diagnosis. However, dilemma arises in patients whose symptoms do not allow a definite diagnosis, especially in patients without imaging findings such as mesenteric changes and mass or lymph nodes. In these situations, other than differentiating CD from ITB (which are the most common etiologies), the differentiation between malignant and benign strictures, especially in older patients, is equally important because the threshold for operative intervention is low in malignant strictures. To the best of our knowledge, only a few studies addressed this topic and the present study tries to solve this clinical dilemma. We analyzed the data of 89 patients who underwent surgery for small bowel strictures (without definite preoperative diagnosis) at our center. The most common site of stricture was the proximal small bowel (41.5%) followed by the terminal ileum (28.1%). As expected, the most common final histological diagnosis was ITB (26.9%) followed by CD (23.5%). Therefore, ITB and CD accounted for approximately 50% of the undiagnosed cases of small bowel strictures. The number of diagnoses of CD was similar to that of ITB, indicating that the incidence of IBD is increasing in India.^5,6 Other than diarrhea (which is a common symptom),^7,8 there were no significant differences in the clinical, imaging, or operative findings between CD and ITB patients. It is of interest that neither the location nor the number of strictures could help differentiate between these 2 diseases. Therefore, in undiagnosed cases of small bowel strictures, the differentiation between CD and ITB is difficult, and surgery should be performed early in cases in which the patient does not respond to ATT.

The most important finding in the present study was that, although ITB and CD were the most common diagnoses, they accounted for only 50% of the cases. Among the remaining patients, malignancy was the most common cause, present in approximately 16% of the cases, and included adenocarcinoma, lymphoma, gastrointestinal stromal tumor, and neuroendocrine tumor. We found that age >50 years had a specificity for malignant etiology of 80%. Moreover, only 1 patient with malignant stricture had more than 1 stricture preoperatively, and 64% of the patients with malignant strictures had proximal small bowel involvement. Among the patients aged >50 years with a single stricture and proximal bowel involvement, 44% had a malignant etiology. Therefore, the threshold for surgery is low in patients aged >50 years with a single undiagnosed isolated stricture in the proximal small bowel.

The second most common etiology after ITB/CD and malignant stricture was ischemic stricture, present in approximately 10% of the patients. Ischemic strictures are often overlooked as a cause of intestinal obstruction and are rarely suspected in clinical cases. Ischemic strictures showed a predilection for the proximal segments of the small intestine considering that 7 of 9 patients had strictures in this region (Table 1). Therefore, ischemic strictures should be suspected, particularly in patients who do not respond to empirical treatment of CD or ITB. Furthermore, approximately 20% of the study patients had a non-specific histology and thus a definitive diagnosis could not be reached even after surgical resection.

Our study has limitations. First, the nature of the study was retrospective and therefore the reliability of the extracted information may be questioned. Second, the fact that our center is a tertiary care referral hospital with special interest in IBD may produce a referral bias. Third, our study initiated in the year 2000. In this respect, endoscopic procedures for small bowel lesions such as double balloon/single balloon enteroscopy were not widely available in India then. Therefore, many patients with small bowel strictures remained undiagnosed and received empirical treatment. Furthermore, these procedures may not be advisable to many of these patients because they frequently present with symptoms of bowel obstruction and the diagnosis of these symptoms is technically difficult in the presence of strictures. For this reason, the data remain eligible in the current scenario even with the availability of such procedures.

In conclusion, our results indicate that patients with small bowel strictures without any mass lesion on imaging and endoscopy findings can have a wide range of diagnoses, including neoplastic disorders. Therefore, we suggest a low threshold for surgical resection in these patients, particularly in older patients with a single stricture in the proximal location. This approach may provide a definitive diagnosis and adequate treatment.