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CT of Small-Bowel Obstruction

Another Perspective Using Multiplanar Reformations

¹ Both authors: Department of Radiology, Duke University Medical Center, P. O. Box 3808, Durham, NC 27710

Received July 21, 1999; accepted after revision September 24, 1999.

 
Address correspondence to E. K. Paulson.

Introduction

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Small-bowel obstruction is a frequent cause of abdominal pain and accounts for 20% of all acute surgical admissions [1]. CT is useful for patients with suspected small-bowel obstruction and is used in many institutions [2,3,4,5]. Unlike barium examinations, CT can reveal the presence, site, and cause of obstruction [4,5,6].

New methods of image processing have increased interest in viewing abdominal anatomy and abnormality. By using a workstation, radiologists can view the tissue volume acquired with helical CT in the axial and other planes. In some patients with small-bowel obstruction, the presumed point of transition from dilated to nondilated bowel is difficult to determine in the axial plane. Multiplanar views centered on an anticipated transition point may help determine the site, level, and cause of obstruction. We describe the use of multiplanar reformations in the evaluation of small-bowel obstruction.

Technique

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Images were obtained through the abdomen and pelvis using a helical single detector CT/i unit (General Electric Medical Systems, Milwaukee, WI) (collimation, 5 mm; pitch, 1.5:1; 140 kVp; 160-190 mAs; matrix, 512 x 512). In most patients, images were acquired during a single breath-hold. Patients received 450 ml of a 2% barium sulfate suspension (Readi-Cat2; E-Z-EM, Westbury, NY) 1-2 hr before scanning. Some patients declined oral contrast material and received an IV dose of 150 ml of iopamidol (Isovue 300: Bracco Diagnostics, Princeton, NJ) at a rate of 3 ml/sec. Imaging was obtained after a delay of 70 sec. Images were then reconstructed at 3-mm intervals using the soft-tissue algorithm. Reconstructions were downloaded to a Vitrea workstation (Vital Images, Minneapolis, MN) for processing. We used the workstation to view images in the sagittal, coronal, and axial planes. Once a probable transition point was identified, curved multiplanar reformations were created by manually tracing a ray along the dilated loop of bowel just proximal to the presumed transition point (Fig. 1A,1B,1C). The workstation made it easy to scroll through multiplanar images. Postprocessing required approximately 10-15 min.

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —67-year-old man with Crohn's disease who underwent terminal ileum resection and who presented with vomiting. Axial CT scan shows dilated loops of small bowel and collapsed colon (large arrow). Note narrowed segment of bowel (arrowhead) between two dilated loops of bowel, suggestive of proximal and distal obstruction point. Markers (small arrow) placed along transition from dilated to narrowed bowel define points of connection for curved coronal oblique reconstruction image shown in B.

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —67-year-old man with Crohn's disease who underwent terminal ileum resection and who presented with vomiting. Coronal oblique reformation along markers in A confirms fixed narrowing (arrowheads) with dilated bowel proximally and distally. Image also shows transition point more distally (arrow). At surgery, multiple adhesions were identified that caused two separate points of transition.

View larger version (160K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —67-year-old man with Crohn's disease who underwent terminal ileum resection and who presented with vomiting. Sagittal oblique reformation shows narrowed segment (arrows) between two dilated loops of small bowel. No mass appears at transition point.

Hernias

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Approximately 95% of obstructions caused by hernias are external [7]. CT is excellent for detecting and characterizing bowel and mesentry in the hernia sac (Fig. 2A,2B,2C). Internal hernias originate from defects in the mesentery or peritoneum and appear similar to external hernias because loops of bowel are tightly apposed in a hernia sac in the abdomen (Fig. 3A,3B). Internal hernias are typically congenital in origin and occur in the left or right paraduodenal, paracecal, and parasigmoid regions; however, hernias sometimes occur after trauma or surgery. Approximately 28% of obstructions caused by hernias are complicated by strangulation and ischemia [7].

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —59-year-old woman who underwent abdominal hysterectomy and presented with abdominal pain and vomiting. Axial CT scan reveals dilated small bowel (arrow), collapsed small bowel (arrowhead), and ventral hernia (V). Line indicates plane of coronal oblique reconstruction in B.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —59-year-old woman who underwent abdominal hysterectomy and presented with abdominal pain and vomiting. Coronal oblique reformation through defect in abdominal musculature shows mesenteric fat and small bowel contained in hernia sac (arrows). Plane of reformation is indicated by line in A. Note abdominal musculature (arrowheads).

View larger version (168K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —59-year-old woman who underwent abdominal hysterectomy and presented with abdominal pain and vomiting. Sagittal oblique multiplanar reformation shows transition from dilated to collapsed bowel (arrows) at inferior aspect of fascial defect. Transition point was confirmed at surgery. Note reconstructed image is somewhat degraded by unsharpness and graininess. Noise could be reduced by decreasing slice thickness, decreasing pitch, or increasing percentage overlap on reconstructions.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —84-year-old man who underwent partial gastrectomy for peptic ulcer disease and vomiting. Axial CT scan reveals small-bowel obstruction caused by incarcerated ileum (arrowheads) in retrocolic peritoneal defect. Internal hernia was confirmed at surgery and was likely caused by prior surgery.

View larger version (180K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —84-year-old man who underwent partial gastrectomy for peptic ulcer disease and vomiting. Coronal oblique reformation reveals relationship of hernia sac (arrows) to retroperitoneal structures, including right kidney (k). Specific transition point could not be identified.

Neoplasms

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Neoplasms of the small bowel represent 3-6% of all gastrointestinal tumors. The most common primary neoplasm is carcinoid. The tumor may invade mesenteric nodes creating a mass that is often associated with a desmoplastic reaction that may involve the small bowel. Small-bowel obstruction associated with carcinoid is usually caused by fibrotic response [7] (Fig. 4A,4B,4C).

View larger version (127K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A. —58-year-old woman with carcinoid and vomiting. Axial source image shows mild small-bowel dilatation and bowel wall thickening (arrow). Note enlarged lymph nodes and stranding in mesenteric fat. Oral contrast material has progressed to colon, suggesting low-grade obstruction.

View larger version (168K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B. —58-year-old woman with carcinoid and vomiting. Coronal oblique reformation shows multiple loops of bowel with thick walls and increased attenuation in mesenteric fat (arrow). Findings are suggestive of serosal and mesenteric involvement by carcinoid.

View larger version (172K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C. —58-year-old woman with carcinoid and vomiting. Sagittal oblique multiplanar reformation shows thickening of several loops of bowel (arrow).

Metastases are more common than primary tumors for small-bowel malignancies. Primary tumors that tend to hematogenously metastasize to the submucosa include bronchogenic carcinoma and melanoma. Cancer of the ovary, breast, stomach, pancreas, and colon may also cause peritoneal carcinomatosis that can involve the serosa of the small bowel, resulting in obstruction [7] (Fig. 5A,5B,5C,5D).

View larger version (118K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A. —74-year-old man who underwent right nephrectomy for renal cell carcinoma and radical cystoprostatectomy for transitional cell carcinoma. Patient received oral contrast material to help distinguish urinary diversion conduit from fluid-filled bowel. Axial CT scan shows low-attenuation pelvic mass (arrow) resulting from recurrent transitional cell carcinoma. Carcinoma caused small-bowel obstruction, and tumor was necrotic.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B. —74-year-old man who underwent right nephrectomy for renal cell carcinoma and radical cystoprostatectomy for transitional cell carcinoma. Patient received oral contrast material to help distinguish urinary diversion conduit from fluid-filled bowel. Sagittal oblique reformation shows tumor encasing several loops of opacified small bowel (arrow) and extending to anterior abdominal wall (arrowhead).

View larger version (169K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C. —74-year-old man who underwent right nephrectomy for renal cell carcinoma and radical cystoprostatectomy for transitional cell carcinoma. Patient received oral contrast material to help distinguish urinary diversion conduit from fluid-filled bowel. Coronal oblique reformation shows mass with several loops of opacified small bowel (arrow).

View larger version (169K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5D. —74-year-old man who underwent right nephrectomy for renal cell carcinoma and radical cystoprostatectomy for transitional cell carcinoma. Patient received oral contrast material to help distinguish urinary diversion conduit from fluid-filled bowel. Coronal oblique reformation shows hydroureteronephrosis (arrow) resulting from tumor involving distal left ureter.

Adhesions

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
After abdominal surgery, adhesions form in approximately 90% of patients and are the cause of small-bowel obstruction in 60% of patients [7]. The CT diagnosis of adhesions can be difficult because the diagnosis is based on exclusion. The diagnosis is presumed when the caliber of bowel lumen changes dramatically with no other explanation [2,3] (Fig. 1A,1B,1C). Multiplanar reformations allow the transition point to be viewed from a variety of perspectives and can increase diagnostic confidence that a mass is absent. Adhesive bands are typically unidentified on CT unless complicated by inflammation or carcinomatosis. With these complications, adhesions may appear as linear bands of soft tissue.

Miscellaneous

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Inflammatory bowel disease, specifically Crohn's disease, commonly affects the small intestine. CT findings of Crohn's disease include circumferential bowel wall thickening, stranding of the mesentery, enlarged mesenteric lymph nodes, and fibrofatty proliferation. Complications include intraabdominal abscess, fistula and sinus tracts, and colonic malignancy. Fistulous tracts may appear as linear soft-tissue structures between loops of bowel or may extend to the abdominal wall. Obstruction can occur because of complications of inflammatory bowel disease and because of fibrotic segments of bowel, which are found in long-standing disease [7] (Fig. 6A,6B).

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A. —47-year-old woman with Crohn's disease and vomiting. Axial CT scan shows dilated loops of small bowel and colon (arrow) and possible transition point in left lower quadrant.

View larger version (168K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B. —47-year-old woman with Crohn's disease and vomiting. Coronal oblique reformation shows soft-tissue tracts (arrowheads) from small bowel to descending colon with surrounding inflammation and bowel wall thickening. At surgery, tract represented fistulous communication between inflamed loops of small bowel and descending colon.

Infectious enteritis caused by Yersinia organisms or Mycobacterium tuberculosis may mimic Crohn's disease (Fig. 7A,7B,7C). Similar CT findings may appear with Mycobacterium avium-intracellulare in immunocompromised patients. Other inflammatory processes that mimic Crohn's disease include celiac disease, Behçet's syndrome, and radiation enteritis.

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7A. —28-year-old man with enterocolitis caused by Yersinia organisms. Axial CT scan shows dilated small bowel proximal to focal segment of bowel with thickened wall (arrowhead).

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7B. —28-year-old man with enterocolitis caused by Yersinia organisms. Coronal oblique reformation shows relatively collapsed thick-walled bowel loop (arrowheads) in right abdomen.

View larger version (153K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7C. —28-year-old man with enterocolitis caused by Yersinia organisms. Sagittal oblique reformation reveals thick-walled segment of bowel (arrow).

Conclusion

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 
Helical CT is useful to characterize the cause, site, and possible complications of small-bowel obstruction. The increasing use of CT to examine patients with suspected small-bowel obstruction attests to its availability and reliability. Reformatting helical CT scans in multiple planes provides a new perspective for the evaluation of small-bowel obstruction and may be useful in defining and characterizing obstruction. However, in most patients, the multiplanar reconstructions simply confirm and complement the information revealed on axial source images. Further research is required to assess the added value and efficacy of this technique.

References

Top Introduction Technique Hernias Neoplasms Adhesions Miscellaneous Conclusion References

 

1. McFadden DW, Zinner MJ. Manifestations of gastrointestinal disease. In: Schwartz SI, Shires GT, Spencer FC, eds. Principles of surgery. New York: McGraw-Hill, 1994: 1015 -1042
2. Megibow AJ, Balthazar EJ, Kyunghee CC, et al. Bowel obstruction: evaluation with CT. Radiology 1991;180: 313 -318[Abstract/Free Full Text]
3. Fukuya T, Hawes DR, Lu CC, Chang PJ, Barloon TJ. CT diagnosis of small-bowel obstruction: efficacy in 60 patients. AJR 1992;158: 765 -769[Abstract/Free Full Text]
4. Maglinte DDT, Reyes BL, Harmon BH, et al. Reliability and role of plain film radiography and CT in the diagnosis of small-bowel obstruction. AJR 1996;167: 1451 -1455[Abstract/Free Full Text]
5. Maglinte DDT, Balthazar EJ, Kelvin FM, Megibow AJ. The role of radiology in the diagnosis of small-bowel obstruction. AJR 1997;168: 1171 -1180[Free Full Text]
6. Taourel PG, Fabre JM, Pradel JA, et al. Value of CT in the diagnosis and management of patients with suspected acute small-bowel obstruction. AJR 1995;165: 1187 -1192[Abstract/Free Full Text]
7. Herlinger H, Rubesin SE. Obstruction. In: Gore RM, Levine MS, Laufer I, eds. Textbook of gastrointestinal radiology, vol. 1. Philadelphia: Saunders, 1994: 931-966

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