From the Guidelines
Fecal burden X-ray is not a recommended initial diagnostic tool for assessing bowel obstruction or Crohn's disease, as its sensitivity and specificity are limited, and it does not provide direct visualization of bowel pathology. According to the most recent and highest quality study, the American College of Radiology (ACR) Appropriateness Criteria for Crohn's disease 1, radiographs of the abdomen are limited in the initial diagnosis for Crohn's disease and may be useful only in severely ill presenting patients to evaluate for the presence of bowel perforation or obstruction.
Diagnostic Approach
When assessing a patient with suspected constipation or fecal impaction, a thorough medical history, physical examination, and laboratory tests are essential for diagnosis. If a patient has a significant fecal burden, treatment typically begins with a bowel regimen including osmotic laxatives such as polyethylene glycol (MiraLAX) 17g mixed in 8oz of water daily, or lactulose 10-20g daily. For more severe impaction, a combination approach may be needed, adding stimulant laxatives like bisacodyl (Dulcolax) 5-10mg orally or as a suppository.
Radiographic Evaluation
In cases of suspected bowel obstruction, abdominal plain X-ray may be used as the first level radiologic study, but its sensitivity and specificity are limited, ranging from 50-60% in small bowel obstruction 1. The ACR Appropriateness Criteria for Crohn's disease also states that radiographs may be useful in severely ill presenting patients to evaluate for the presence of bowel perforation or obstruction 1. However, the value of plain X-rays complementary to physical examination is limited, and they do not provide anatomical information that helps differentiate between the various causes of bowel obstruction 1.
Treatment and Management
After the initial clearance, maintenance therapy should include increased fluid intake (2-3 liters daily), dietary fiber (25-30g daily), and regular physical activity. The underlying pathophysiology involves decreased colonic motility, dehydration of stool, or neuromuscular disorders affecting bowel function. Regular follow-up is important to adjust the regimen as needed and to investigate any underlying causes of chronic constipation. In summary, while fecal burden X-ray may not be a primary diagnostic tool, a comprehensive approach to diagnosis and treatment is essential for managing patients with suspected constipation or fecal impaction.
From the Research
Fecal Burden X-ray Studies
- The utility of plain abdominal radiography in adult ED patients with suspected constipation was studied in 2, which found that abdominal radiography did not appear to significantly affect the ED management of patients presenting with constipation.
- A study published in 3 investigated the value of the plain abdominal radiograph in the assessment of constipation and found that it was as reliable as measurement of faecal weight or marker transit.
- The association between fecal loading in the cecum detected by plain abdominal X-ray and acute appendicitis was studied in 4, which found that radiographic sign of fecal loading in the cecum was detected in 97% of patients with acute appendicitis.
- Abdominal radiograph usage trends in the setting of constipation were analyzed in 5, which found that constipation radiograph volume increased by approximately 56% over a 10-year period.
- The relationship between colonic stool burden and slow transit constipation was investigated in 6, which found that stool burden assessment on AXR may be a reliable alternative to a radiopaque marker study in the assessment of colonic transit.
Key Findings
- Fecal burden on radiography does not preclude a more serious diagnosis 2.
- Plain abdominal radiography can be used to assess constipation and is as reliable as measurement of faecal weight or marker transit 3.
- Fecal loading in the cecum detected by plain abdominal X-ray is associated with acute appendicitis 4.
- Clinicians and radiologists have differing opinions on the utility of abdominal radiographs for constipation 5.
- Stool burden assessment on AXR may be a useful surrogate for slow transit constipation 6.