A 60-year-old male presents with abdominal pain, absolute constipation, and vomiting. On examination, his abdomen is distended, and percussion reveals no shifting dullness. What is the first step in the evaluation of his condition?
A. Passing nasogastric tube
B. Abdominal ultrasound
C. Plain X-ray of abdomen
D. Sigmoidoscopy
E. CT scan abdomen
Correct Answer: C. Plain X-ray of abdomen
Explanation:
The patient’s symptoms of abdominal pain, distension, vomiting, and absolute constipation strongly suggest intestinal obstruction. The first diagnostic step in evaluating such a case is a plain X-ray of the abdomen in both supine and erect positions. The X-ray is a rapid, non-invasive, and readily available tool to confirm the diagnosis and identify the level of obstruction (e.g., small bowel vs. large bowel). It may show characteristic findings like:
- Dilated bowel loops: Proximal to the site of obstruction.
- Air-fluid levels: Typically seen in the upright X-ray.
- Absence of gas in the rectum: Indicative of complete obstruction.
Why Other Options Are Incorrect:
A. Passing nasogastric tube:
- While an NG tube is often inserted for decompression and symptom relief in intestinal obstruction, it is a management step, not an investigation. It does not confirm the diagnosis or identify the cause of obstruction. Imaging is necessary first.
B. Abdominal ultrasound:
- Although an ultrasound can identify some abdominal pathologies, it is not the preferred modality for evaluating suspected intestinal obstruction. Gaseous distension in the bowel can obscure ultrasound imaging, making it less effective in this situation.
D. Sigmoidoscopy:
- Sigmoidoscopy may be used in cases of suspected colonic obstruction due to malignancy or volvulus. However, it is not the first step in evaluation and is typically performed after imaging studies confirm the diagnosis and the site of obstruction.
E. CT scan abdomen:
- A CT scan is highly sensitive for identifying the site, severity, and cause of intestinal obstruction (e.g., hernia, volvulus, mass). However, it is not the initial step because a plain X-ray is quicker, less expensive, and often sufficient for the initial evaluation.
Key Features of Intestinal Obstruction:
- Clinical Presentation:
- Abdominal distension: Common in both small and large bowel obstruction.
- Vomiting: Early in small bowel obstruction; may be late in large bowel obstruction.
- Absolute constipation: Absence of both feces and gas passage indicates complete obstruction.
- Abdominal pain: Colicky in nature, often worsening as the obstruction persists.
- Physical Examination:
- Distended abdomen: More pronounced in large bowel obstruction.
- Absent bowel sounds: Suggestive of paralytic ileus.
- Hyperactive bowel sounds: Indicative of early obstruction.
- No shifting dullness: Suggests the absence of ascites.
Common Causes of Intestinal Obstruction:
- Small Bowel Obstruction:
- Adhesions (most common).
- Hernias.
- Intussusception.
- Tumors.
- Large Bowel Obstruction:
- Colorectal carcinoma (most common).
- Diverticulitis.
- Volvulus (sigmoid or cecal).
- Fecal impaction.
Management Overview:
- Immediate Actions:
- Nasogastric decompression: To relieve vomiting and reduce intra-abdominal pressure.
- IV fluid resuscitation: Prevent dehydration and correct electrolyte imbalances.
- Imaging Studies:
- Plain X-ray of abdomen: Initial diagnostic tool.
- CT scan abdomen and pelvis: Next step if the X-ray is inconclusive or more detailed evaluation is required.
- Definitive Treatment:
- Surgical intervention: Required for complete obstructions, volvulus, or malignancy.
- Non-surgical management: May be appropriate for partial obstructions or paralytic ileus.
Conclusion:
In a patient presenting with symptoms of intestinal obstruction, the first step in evaluation is a plain X-ray of the abdomen to confirm the diagnosis and guide further management. Early identification and intervention are critical to preventing complications such as bowel ischemia or perforation. CT scans and other advanced imaging modalities are reserved for cases where additional detail is required or if the diagnosis remains unclear after an X-ray.