Intestinal Obstruction: Role of MDCT with Surgical Correlation

Amandeep Singh, Indreet Kaur Makkar, CL Thukral, Kamlesh Gupta, Manjit Singh Uppal Associate Professor, Department of Radiodiagnosis & Imaging, SGRD Institute of Medical Sciences and Research, Amritsar, India, Senior Resident, Department of Radiodiagnosis & Imaging, SGRD Institute of Medical Sciences And Research, Amritsar, India, Professor, Department of Radiodiagnosis & Imaging, SGRD Institute of Medical Sciences and Research, Amritsar, India, Professor & Head, Department of Radiodiagnosis & Imaging, SGRD Institute Of Medical Sciences And Research, Amritsar, India, Director-Principal , Professor Surgery SGRD Institute of Medical Sciences & Research, Amritsar, India.


Introduction
Intestinal obstruction is one of the common cause of admission to emergency department with acute abdomen. The early diagnosis of bowel obstruction is critical in preventing complications, particularly perforation and ischemia. [1] Small bowel obstruction remains important cause of morbidity accounting for upto 15% of surgical admissions for non -traumatic abdominal pain. [2] Plain abdominal radiography continues to be the initial examination in these patients due to its wide availability and relatively low cost. However, radiographs are diagnostic in only 50%-60% of cases and have high sensitivity only for high-grade obstruction. Nevertheless, the results of this modality should serve as a basis for triage for further imaging work-up and assist in the therapeutic decision. [3][4][5] Sonography is not commonly used for the evaluation of SBO (Small Bowel Obstruction) mainly because most of the time the bowel loops are filled with gas, producing nondiagnostic sonograms, and because adhesions, the most common cause of mechanical SBO, are not detected with this technique. [6] However, when the obstructed bowel segments are dilated and filled with fluid, not only can the level of obstruction be recognized but the cause of the obstruction can also be demonstrated by using the fluidfilled bowel as a sonic window. [6,7] Contrast material-enhanced studies, particularly volume-challenge enteral examinations like enteroclysis, were once advocated as the definitive study in patients with clinical uncertainty about the diagnosis of SBO, since these studies correctly demonstrate the presence of obstruction in 100% of cases, the level (proximal vs distal) of obstruction in 89% of cases, and the cause of the obstruction in 86% of surgically treated patients. [8] The new technology, that is of increasing interest in the diagnosis of small bowel obstruction is multiplanar reformatted imaging at a workstation. Volume data of the abdomen is acquired with the helical technique during a single breath hold, usually with a collimation of 5mm. MDCT scanner enables better spatial resolution through thinner collimation. Axial, sagittal, coronal, and curved multiplanar reformatted images are created at a workstation from the acquired volume data. Multiplanar views may help identify the site, level and cause of obstruction when axial images are indeterminate. [9] Conversely, if the initial radiographic findings are interpreted as normal, equivocal, or suggestive of a lowgrade partial SBO, an examination that challenges the distensibility of the small bowel such as small bowel follow-through study, enteroclysis, or CT enteroclysis is recommended, as these usually exaggerate the effects of mild obstructions. [3,[10][11][12][13] Nevertheless, we emphasize that a bowel obstruction is a dynamic and ever-changing process. It can rapidly evolve into a catastrophic condition with ischemia or resolve by itself. Therefore, in those cases where surgical treatment is not immediate or advocated, it is ISSN (0): 2347-338X; ISSN (P): 2347-3371 Original Article necessary to maintain close communication between the surgeon and radiologist in order to guarantee the appropriate imaging and clinical follow-up. [14] Intestinal obstruction may be classified into two types: • Dynamic-in which peristalsis is working against a mechanical obstruction. It may occur in an acute or a chronic form. It includes intraluminal (faecal impaction, foreign bodies, bezoars,gallstones), intramural (stricture and malignancy) and extramural causes (bands/adhesions, hernia, intususcception and volvulus). • Adynamic-in which there is no mechanical obstruction; peristalsis is absent or inadequate (e.g. paralytic ileus, mesenteric ischaemia or pseudo-obstruction). [15] Types of obstruction Simple Small Bowel Obstruction: Typical cases of simple obstruction may show diffuse bowel loop dilatation with a smooth transition zone or a smooth "beak" at the obstructed site on computed tomography (CT). The bowel wall at the site of obstruction may be minimally thickened or of normal thickness.
Mesenteric changes, such as vascular engorgement and haziness, are absent or minimal, and ascites is either absent or minimal.

Closed-Loop Obstruction:
The most important CT indicators may include the whirl sign, convergence of mesenteric vessels toward the twisted site, and reversed position of the mesenteric artery and vein. The whirl sign, however, is also seen in asymptomatic subjects or in patients who had undergone gastric surgery for gastric pathologies.

Strangulated Small Bowel Obstruction:
Strangulation implies interference with the blood supply associated with an obstruction that may not necessarily be complete.
CT criteria for strangulated obstruction are as follows: • Portal or mesenteric venous gas, pneumatosis intestinalis • Abnormal bowel wall enhancement • Serrated beak sign • Unusual mesenteric vascular course • Diffuse mesenteric vascular engorgement and haziness • Bowel wall thickening • A large amount of ascites. [16] subjects and Methods

Study design
A prospective study was done with evaluation of forty patients, clinically suspected of intestinal obstruction who were referred to the department of radiodiagnosis.
All patients (age >18yrs) who were clinically suspected for intestinal obstruction with complications (such as strangulation and bowel ischemia) and without complications whose follow up data (surgical) was available were included in the study.
Patients with age <18yrs, deranged renal function tests, allergic to contrast, pregnancy and conservatively managed patients were excluded. Protocol: Patients clinically suspected for intestinal obstruction and referred to the department were subjected to CT examination which was performed by using Somatom Scope (Siemens, Erlangen, Germany). The scanning parameter were 130-150 mAs, 130kVp, 6x2.0 mm collimation, 5 mm slice thickness, 1.5 mm reconstruction intervals. Oral positive/neutral/negative contrast were given in selected patients. CT images were obtained after administering 100 mL of intravenous contrast (contrapaque-containing iohexol equivalent to 300mg iodine, 1.2mg tremathine, 0.1mg edetate calcium sodium, water for inj q.s.) All the patients who underwent CT examination were followed up for surgical management. Correlation of the CT findings with operative findings were done.

Results
In the present study, the maximum number of patients presenting with intestinal obstruction were in the age group of 31-40 years i.e. 10 patients (25%). The youngest patient in the present series was 19 years old whereas the oldest patient was 90 years old [ Table 1]. Out of 40 patients, the number of male patients was more than female patients. 24 (60%) male patients were part of the study, whereas 16 (40%) patients were females on X-ray abdomen (Erect) air-fluid levels were seen in 29 (72.50%) patients. Whereas no air-fluid levels were seen in 11 patients (27.50%) In the present study on intestinal obstruction, the level of obstruction was diagnosed in the small bowel in 30 (75%) patients. The level of obstruction was diagnosed in large bowel in 10 (25%) patients Ileum was the most common site of obstruction in the present study. Out of the total 40 patients 13 (32.50%) had distal ileal obstruction. Proximal ileal obstruction was seen in 8 (20%) patients. Jejunal obstruction was seen in 4 (10%) patients and duodenum obstruction was seen in 2 (5%) patients. Ascending/ transverse/ descending colon was the site of obstruction in 7(17.5%) patients. Rectosigmoid was the site of obstruction in 3 (7.5%) patients. No definite site of obstruction was seen in three patients amongst which two patients who had multiple dense adhesions hence zone of transition was not determined and another patient had prominent distal ileal loops with no narrow zone of transition. On MDCT, out of total 40 patients, adhesions were found to be the cause of obstruction in 21 (52.50%) patients. Hernia was the cause in 3 (7.50%) patients. Intussusception was the reason of obstruction in 2 (5%) patients. Malignancy was the cause of obstruction in 5 (12.5%) patients. Malrotation was the cause in 4 (10%) patients and malignancy was the cause of obstruction in 5 (12.50%) patients. Ischaemia, intraluminal and indeterminate were the cause in 1 (2.5%) patient each while extrinsic compression was the cause in 2 (5.00%) patients. In the present study on 40 patients with intestinal obstruction was adhesions (32.50%). The result of present study matched with studies done by Malik AM et al in which commonest cause of obstruction was adhesions comprising 41% of patients. [21] Malik AM et al evaluated 229 patients with acute intestinal obstruction. Post operative adhesions accounted for 41% (n = 95) of the total cases, followed by abdominal tuberculosis (25%, n = 58), obstructed/ strangulated hernias of different types (18%, n = 42). The most common cause of intestinal obstruction was postoperative adhesions. [21] Limitations of my study were small sample size, inadequate distention of the bowel loops with oral/rectal contrast may mimic stricture and oral contrast given in some patients hindered with the detection of the bowel wall thickness and detection of pneumatosis intestinalis.

Conclusion
MDCT by using its multiplanar reformatting and 3D capabilities is highly specific and accurate in detecting the presence of intestinal obstruction and can demonstrate the exact site of obstruction in high percent of cases and detection of complications with high precession helps in appropriate management of the patient.