Can an enema be ineffective in removing all residual stool in a patient post-fecal decompression if only watery stool is expelled without solid components?

From the Guidelines

An enema can be ineffective in removing all residual stool in a patient post-fecal decompression if only watery stool is expelled without solid components, as the enema fluid may bypass harder stool that remains adherent to the bowel wall or is located higher in the colon. This is a critical consideration in clinical practice, as inadequate clearance of stool can lead to recurrent impaction, constipation, and other complications that can significantly impact morbidity, mortality, and quality of life 1.

When a patient has been severely impacted, the colon can become dilated and develop pockets where stool may remain lodged despite initial decompaction efforts. In such cases, further preparation with large-volume enemas or additional oral preparation could be considered, as suggested by the US Multi-Society Task Force on Colorectal Cancer 1. The use of a through-the-scope enema technique as a salvage regimen during colonoscopy has also been described, with reported success rates of up to 96% 1.

To ensure complete clearance, multiple enemas may be necessary, or a different approach might be required, such as higher-volume enemas or oral laxatives to address more proximal impactions. Healthcare providers often follow decompaction with a bowel maintenance regimen including stool softeners, osmotic laxatives, and sometimes stimulant laxatives to prevent recurrence. Follow-up assessment with abdominal examination, digital rectal examination, or imaging may be necessary to confirm complete resolution of the impaction, especially if the patient continues to experience symptoms of constipation or abdominal discomfort.

Key considerations in the management of patients with inadequate preparation include the use of supplemental measures aimed at effective colonoscopy and acted on as soon as deemed safe, as well as the recognition of individuals likely to have a poor preparation at the time of arrival to the endoscopy suite 1. By prioritizing these strategies, healthcare providers can minimize the risk of complications and optimize outcomes for patients undergoing fecal decompaction and colonoscopy procedures.

In terms of specific management strategies, the use of large-volume enemas, such as phosphate or bisacodyl enemas, has been shown to be effective in salvaging inadequate preparations 1. Additionally, the implementation of an intensive bowel-cleansing strategy, including a low-fiber diet, liquid diet, and oral laxatives, has been associated with improved outcomes in patients with previously failed outpatient colonoscopy due to inadequate preparation 1.

From the Research

Enema Effectiveness in Removing Residual Stool

• The effectiveness of an enema in removing all residual stool in a patient post-fecal decompression can be limited if only watery stool is expelled without solid components 2, 3.
• Studies have shown that enemas can be effective in treating rectal fecal impaction, but may not always remove all residual stool 4, 2.
• In some cases, enemas may be less effective than other treatments, such as polyethylene glycol (PEG), in removing residual stool and achieving successful disimpaction 2, 3.
• The use of enemas can also be associated with adverse events, such as perforation and metabolic derangement, particularly in elderly patients 5.

Comparison with Other Treatments

• Polyethylene glycol (PEG) has been shown to be equally effective as enemas in treating rectal fecal impaction in children with constipation 2, 3.
• PEG may be more likely to increase defecation frequency and reduce the risk of treatment failure, but can also increase the risk of watery stools and fecal incontinence 2, 3.
• Other treatments, such as antegrade colonic enema, may also be effective in managing fecal incontinence and constipation in certain patients 6.

Limitations and Variability

• The effectiveness of enemas in removing residual stool can vary depending on the individual patient and the specific treatment protocol used 4, 2.
• The quality of evidence supporting the use of enemas and other treatments for fecal impaction and constipation can be limited, and further high-quality studies are needed to determine the optimal management approach 3.