Why is a per rectal (PR) examination necessary before administering an enema?

Why Per Rectal Examination is Needed Before Enema Administration

A per rectal examination is essential before administering an enema to rule out contraindications such as anorectal abscess, rectal obstruction, or fecal impaction, which could lead to serious complications including bowel perforation if an enema is given inappropriately.

Clinical Rationale for Pre-Enema Rectal Examination

Safety Assessment

A digital rectal examination (DRE) before enema administration serves several critical purposes:

1. Identification of contraindications 1:

   • Detecting anorectal abscesses or inflammation
   • Identifying undiagnosed rectal trauma
   • Ruling out intestinal obstruction
   • Checking for recent colorectal surgery sites

2. Assessment of rectal contents 1:

   • Determining if fecal impaction is present
   • Evaluating stool consistency and location
   • Confirming the rectum is not empty (which would make an enema unnecessary)

3. Anatomical evaluation 1:

   • Assessing anal sphincter tone and function
   • Evaluating the puborectalis muscle
   • Checking for structural abnormalities like rectocele

Prevention of Complications

Per rectal examination helps prevent serious complications that could occur if an enema is administered inappropriately 1:

• Perforation risk: Particularly in patients with:

  • Neutropenia or thrombocytopenia
  • Severe colitis or inflammation
  • Recent colorectal surgery
  • Undiagnosed abdominal pain

• Infection risk: Enemas in patients with anorectal abscesses can spread infection and potentially lead to sepsis 1

• Ineffective treatment: Administering an enema when a different intervention is needed (e.g., manual disimpaction for hard fecal impaction)

Proper Examination Technique

The digital rectal examination before an enema should include 1:

1. Patient positioning: Left lateral position with buttocks separated
2. External inspection: Check for:
   • Perianal skin condition
   • Evidence of fecal soiling
   • Anal reflex response
3. Digital examination: Assess:
   • Resting tone of the sphincter
   • Ability to contract (squeeze)
   • Presence of tenderness along puborectalis
   • Presence and consistency of stool
   • Any masses or abnormalities

Enema Selection Based on Examination Findings

The findings from the per rectal examination guide the choice of enema 1:

• Full rectum with soft stool: Small-volume osmotic micro-enema may be sufficient
• Hard impacted stool: Oil retention enema may be more appropriate initially
• Empty rectum with proximal loading: High-volume solution may be needed
• Tenderness or inflammation: May contraindicate enema completely

Contraindications Identified by Rectal Examination

A per rectal examination may reveal absolute contraindications to enema administration 1:

• Neutropenia or thrombocytopenia
• Paralytic ileus or intestinal obstruction
• Recent colorectal or gynecological surgery
• Recent anal or rectal trauma
• Severe colitis, inflammation, or infection
• Toxic megacolon
• Undiagnosed abdominal pain
• Recent radiotherapy to the pelvic area

Conclusion

The per rectal examination is not merely a procedural formality but a critical safety step before enema administration. It allows healthcare providers to identify contraindications, select the appropriate enema type, and prevent potentially serious complications that could significantly impact patient morbidity and mortality.