From the Guidelines
The most appropriate investigation for this 56-year-old man with absolute constipation, rectal bleeding, abdominal distension, empty rectum on digital examination, and radiographic findings of dilated colon and small bowel is a conventional CT scan (option D). This recommendation is based on the clinical presentation suggesting a large bowel obstruction, which requires immediate and accurate diagnosis to guide management. A conventional CT scan can rapidly identify the cause of obstruction, detect the location, and evaluate for potential complications such as perforation or ischemia 1. Key advantages of a conventional CT scan in this context include its non-invasive nature, comprehensive assessment of both intraluminal and extraluminal pathology, and the ability to provide critical information without the need for bowel preparation, which is contraindicated in suspected obstruction. Considerations against other options include:
- Colonoscopy (option B), which may not be technically feasible in the setting of obstruction and carries inherent risks.
- CT Colonography (option C), which requires bowel preparation and is thus contraindicated in obstruction.
- CT enteroclysis (option A), which primarily focuses on small bowel pathology and may not adequately address the colon, the primary site of concern in this patient. Given the acute presentation and the need for a comprehensive assessment, a conventional CT scan with IV contrast is usually appropriate for the initial imaging, as suggested by the American College of Radiology appropriateness criteria for suspected small-bowel obstruction 1.
From the Research
Diagnostic Approach
The patient presents with symptoms of absolute constipation, rectal bleeding, and a distended abdomen, which suggests a potential obstruction in the bowel. The digital rectal examination reveals an empty rectum, and the conventional abdominal x-ray shows a dilated colon with associated dilatation of the small bowel.
Investigation Options
Given the clinical presentation and imaging findings, the most appropriate investigation would be one that can accurately diagnose the cause and extent of the bowel obstruction. The options include:
- CT enteroclysis
- Colonoscopy
- CT Colonography
- Conventional CT scan
Rationale for Choice
Based on the studies 2, 3, 4, 5, CT enteroclysis is a valuable diagnostic tool for evaluating small bowel disorders, including obstruction. It provides detailed images of the small bowel and can help identify the cause and degree of obstruction. In contrast, colonoscopy is more suitable for evaluating the colon and rectum, while CT colonography is better suited for detecting colon cancer and polyps. Conventional CT scan may not provide sufficient detail to diagnose small bowel obstruction.
Key Points
- CT enteroclysis is a hybrid technique that combines fluoroscopic intubation-infusion small-bowel examinations with abdominal CT 4.
- It is superior to other imaging tests, such as peroral small-bowel examinations, conventional CT, and barium enteroclysis, in evaluating small bowel disease 4.
- CT enteroclysis is particularly useful in diagnosing small bowel obstruction, Crohn's disease, and unexplained gastrointestinal bleeding 3, 4.
- Patient preferences for diagnostic tests are influenced by factors such as test sensitivity, risks, and side-effects 6.