Role of MDCT in small bowel lesions

INTRODUCTION: Computed tomography has rapidly become the imaging modality of choice for small bowel pathologies. This study is an example to assess the role of MDCT in the detection and characterization of small bowel pathologies and to decide the further course of the intervention. The availability of MDCT and the continuous refinement of the 3D imaging process had expanded the utility of CT for evaluating patients with bowel disease. MDCT has advantages over classic helical CT in the imaging of the mesenteric vasculature and the bowel. The purpose of this study was to see MDCT in the evaluation of small bowel diseases including tumorsischaemic bowel disease by utilizing the multiplanar capabilities (axial, coronal and sagittal images) and post-processing techniques like Maximum Intensity Projection (MIP), MPR, 3D Volume Rendering (VR) for a detailed evaluation of disease process and enhancing the diagnostic accuracy of initial diagnosis, management, follow up and detection of potential complications. The creation of MPR images increases confidence in identifying the lesion and in diagnosing or excluding the bowel pathology. In abdomen imaging with spiral CT, the area to be scanned is about 40–60 cm from the base of the lungs to the pubis. CT can cover the entire abdomen and display high-resolution images. Recent advances have improved the imaging evaluation of the small bowel using MDCT which includes the use of MDCT scanners that acquire data, oral contrast agents, and administration techniques that improve small-bowel distension. These advances plus imaging workstations that allow multiplanar reformation and 3D evaluation of these data sets had allowed improved identification and characterization of small-bowel pathology. AIMS AND OBJECTIVES: Aim: Evaluation of small bowel lesions using MDCT. Primary Objective: 1. To study the imaging characteristics of various small bowel pathologies and narrow down the differential diagnosis using MDCT with multiplanar reformation. Secondary objective: 2. To study the role of MDCT with its multiplanar reformation in confirmation of clinically suspected small bowel pathologies. 3. To determine the sensitivity, specificity, and accuracy of MDCT in evaluation of small bowel pathologies. MATERIALS AND METHODS: Type of study: Prospective study Study period: DEC 2018 to OCT 2020 Sample size: Cases – 40 Study population: Data will be collected from patients referred for CECT abdomen with suspected bowel lesions/symptoms of bowel lesions. Method of collection of data: A prospective study will be conducted over two years (DECEMBER 2018 to OCTOBER 2020) on 40 patients with small bowel lesions. They will be evaluated with MDCT(Siemens Somatom definition edge) initially with plain CT scan with the patient in the supine position. Patients undergoing CT were asked to withhold oral intake starting 4hours before the examination. 0.1% mannitol suspension was administered as a neutral oral contrast agent. Our regimen concerning the timing of administration of mannitol involved the ingestion of a total of 1.35 L over 1 hour (450 ml at 60minutes, 450 ml at 40 minutes, 225 ml at 20 minutes, 225ml at 10 minutes before scanning14 After the mannitol was ingested, a bolus of intravenous contrast material (125 ml) followed by 50 ml of saline solution was administered with a power injector at a rate of 4ml/sec. 14 Helical scanning using a 64 slice MDCT scanner was performed from the diaphragm to the symphysis pubis, included a triple-phase study (arterial, venous, and delayed). Postprocessing techniques include axial image reconstruction with a section thickness of 1 mm, reformatting of axial image data for maximum intensity projections, and volume rendering when required. RESULTS: 1. The study was conducted among 40 study participants. Among them 35 (87.5%) were males and 5 (12.5%) were females 2. The mean age of the study population was 38.93 years with a standard deviation of 17.74 years. 3. In our study population, distal ileum and the ileocaecal junction is the most common part involved 22 (55%). This was followed by proximal ileum 6 (15%), caecum 5 (12.5%), distal jejunum 4 (10%), proximal jejunum 2 (5%) and ascending colon 1 (2.5%). 4. Out of 40 lesions, 38 (95%) were non-neoplastic and only 2 (5%) were neoplastic. Both the 2 neoplastic lesions were gastrointestinal stromal tumors (GIST). Among non-neoplastic lesions, Crohn’s disease is the most common lesion present in 18 (47.36%) followed by tuberculosis in 11 (28.94%). 5. Bowel wall involvement was observed in 36 (90%) of the patients. Both the neoplastic lesions of GIST had bowel wall involvement. Among non-neoplastic lesions, 34 (89.47%) had bowel wall involvement. 6. The majority of the study participants had a target pattern of contrast enhancement 25 (62.5%) followed by homogenous enhancement at 9 (22.5%) and heterogeneous enhancement at 2 (5%). Contrast enhancement was found to be poor in 4 (10%) of the study participants. Both the neoplastic lesions had heterogeneous contrast enhancement. Heterogenous contrast enhancement was not found in non-neoplastic lesions. The length of the thickened bowel segment was classified into three categories as follows: Focal ( 40 cm). 7. In our study, segmental involvement was more common at 20 (50%) followed by focal at 16 (40%) and diffuse involvement in 4 (10%) study participants. Both the neoplastic lesions had focal thickening. 8. Among 40 study participants, the wall involvement of lesions was observed in 36 (90%). Among those who had wall involvement mucosal involvement was observed in 34 (85%) and submucosal involvement was seen in 2 (5%). Both the neoplastic lesions had submucosal wall involvement. The mucosal wall was not affected in 4 (10%) individuals. 9. The involvement of mesentery in the form of mass or fat stranding or vascular engorgement was observed in 19 (47.5%) study participants. Mesenteric involvement was not observed in 21 (52.5%) individuals. Both the neoplastic lesions did not have mesenteric involvement. 10. The results of MDCT enterography and biopsy are compared and the following table is made to calculate the sensitivity, specificity, positive, and negative predictive values. The sensitivity of MDCT enterography incorrectly identifying the bowel lesions in our study population was found to be 88.23%. The specificity of MDCT enterography was found to be 50% in our study population. The positive and negative predictive values were 93.75% and 33.33% respectively. CONCLUSION: CT enterography can diagnose all major pathologies originating in the lumen and different layers of the small bowel and also evaluate the disease spread outside the bowel with good sensitivity and specificity. The technique is simple and the time taken for the procedure is less than standard conventional small bowel procedures and no more than a standard CT abdomino pelvic study. At the same time, it combines the advantages of enteroclysis and CT scans without any additional radiation risk. Hence, we propose that CT enterography should be considered as the investigation of choice for evaluating small bowel pathologies.