From the Guidelines
The most appropriate investigation for this 56-year-old man with absolute constipation, rectal bleeding, distended but soft abdomen, empty rectum on digital examination, and radiographic findings of dilated colon with small bowel dilatation is a conventional CT scan (option D). This recommendation is based on the high diagnostic accuracy of computed tomography with intravenous contrast, as noted in the study by 1, which provides superior sensitivity and specificity compared to conventional abdominal radiography and ultrasound.
Key Points to Consider
- The patient's presentation suggests a large bowel obstruction, possibly due to colorectal cancer, which is common in this age group.
- CT scanning provides excellent visualization of the entire abdomen and pelvis, allowing assessment of the site and cause of obstruction, presence of masses, wall thickening, and extraluminal pathology.
- While colonoscopy might eventually be needed for tissue diagnosis, it's contraindicated in acute obstruction due to perforation risk.
- CT colonography requires bowel preparation which is inappropriate in obstruction, and CT enteroclysis focuses primarily on small bowel pathology rather than colonic disease.
- The study by 1 highlights the importance of computed tomography in identifying complications such as intestinal perforation, peritonitis, and ischemia, which is critical in the management of bowel obstruction.
Additional Considerations
- The ACR appropriateness criteria, as mentioned in the study by 1, recommend CT abdomen and pelvis with IV contrast as the initial imaging for suspected small-bowel obstruction with an acute presentation.
- However, in this case, the patient's symptoms and radiographic findings suggest a large bowel obstruction, making a conventional CT scan the most appropriate initial investigation.
From the Research
Diagnostic Approach
The patient's symptoms of absolute constipation, rectal bleeding, and a distended abdomen with a dilated colon and small bowel on conventional abdominal x-ray suggest a possible bowel obstruction.
Investigation Options
The most appropriate investigation for this patient would be:
- CT enteroclysis, as it is a sensitive and specific test for diagnosing small-bowel obstruction and can help identify the cause of the obstruction 2, 3, 4.
- Alternatively, a conventional CT scan could be considered, but CT enteroclysis is more accurate in diagnosing small-bowel obstruction, especially in cases of low-grade obstruction 5, 6.
- Colonoscopy and CT colonography may not be the best initial choices, as they are more suited for evaluating the colon rather than the small bowel.
Rationale
CT enteroclysis is a valuable diagnostic tool for evaluating small-bowel disorders, including obstruction, and can provide detailed images of the small bowel and its contents 2, 3. It is particularly useful in cases where the cause of the obstruction is unclear or when specific management issues need to be addressed 5. The use of CT enteroclysis can help guide treatment decisions and reduce the need for unnecessary surgery 4.