What are the different types of enemas and how are they used?

Types of Enemas and Their Use

Main Types of Enemas

Enemas fall into three primary categories based on their clinical purpose: retention enemas, evacuant enemas, and softener enemas, which are the most commonly used formulations in nursing practice. 1

Diagnostic/Contrast Enemas

Fluoroscopic contrast enemas can be performed with either water-soluble contrast or barium, depending on the clinical indication. 2

• Water-soluble contrast enemas are preferred when perforation or anastomotic leak is suspected, as they avoid barium spillage into the peritoneal cavity or extraperitoneal pelvis. 2
• Water-soluble contrast enemas are routinely used to evaluate clinically suspected leaks, anastomotic stenoses, fistulas, and sinus tracts, with sensitivity of 80% for small-bowel strictures and 50% for pouch leaks. 2
• Barium enemas should be avoided when leak or perforation is suspected because barium interferes with subsequent CT scans due to streak artifact. 2
• Hydrostatic enemas use liquid under controlled pressure to distend the colon, while pneumatic enemas use air or gas under controlled pressure. 3

Therapeutic Enemas for Constipation

Enemas should only be used after oral laxative therapy (polyethylene glycol plus stimulant laxatives) has failed for several days, as they carry significant risks including perforation with 38.5% mortality when it occurs. 4, 3

Normal Saline Enemas

• Normal saline enemas are less irritating to rectal mucosa compared to other formulations, though large volumes risk water intoxication if retained. 4, 5
• For pediatric patients, 10 mL/kg of normal saline is sufficient when the child has received clear liquids for 24 hours. 4
• In adults, 500-1000 mL of tap water is the standard volume for therapeutic enemas. 3

Soap Suds Enemas

• The correct formulation is 1 mL of mild liquid soap per 200 mL of solution, with a total volume of 1000 mL, and must be administered by an experienced healthcare professional, not self-administered. 5
• The mechanism involves distending the rectum and moistening/softening stools. 5
• Chemical irritation of mucous membranes is the primary concern with soap suds enemas. 5

Osmotic Micro-Enemas

• Small-volume self-administered enemas (120-150 mL) are preferred when appropriate, as they are safer than large-volume enemas. 3
• Osmotic micro-enemas work best when the rectum is full on digital rectal examination. 5

Docusate Sodium Enemas

• Docusate sodium enemas soften stool in 5-20 minutes, though may cause anal/rectal burning. 5

Specialized Formulations

• For hepatic encephalopathy, mix 300 mL lactulose with 700 mL water (total 1000 mL) and administer 3-4 times daily, retaining the solution for at least 30 minutes. 3
• A 20% lactitol enema demonstrated 100% efficacy versus 20% for tap water alone in improving hepatic encephalopathy symptoms. 3

Medication Delivery Enemas

Moderately hypotonic enemas with ion compositions similar to feces result in high local tissue levels with minimal systemic drug exposure, making them ideal for treating local colorectal conditions. 6

• Sodium-based, absorption-inducing (hypotonic) enemas rapidly transport drugs and nanoparticles deep into colorectal folds to reach virtually the entire epithelial surface. 6
• Strongly hypotonic and hypertonic enemas cause rapid systemic drug uptake, whereas moderately hypotonic enemas maximize local drug concentrations. 6
• For ulcerative colitis, corticosteroid, 5-aminosalicylate (5-ASA), and nicotine liquid enemas, as well as corticosteroid foam, show no significant difference in patient preference or overnight retention. 7

Absolute Contraindications - Screen Every Patient Before Use

Never administer enemas to patients with any of the following conditions, as they carry life-threatening risks:

• Therapeutic or prophylactic anticoagulation - risk of fatal bleeding and intramural hematomas. 4, 5, 3
• Neutropenia or thrombocytopenia - increased infection and bleeding risk. 4
• Paralytic ileus or intestinal obstruction - risk of perforation. 4, 3
• Recent pelvic radiotherapy - weakened bowel wall. 5, 3
• Recent deep biopsy or polypectomy with electrocautery - impaired bowel wall integrity. 8
• Undiagnosed abdominal pain - may mask serious pathology. 3

Critical Safety Considerations

Volume Guidelines

• Median final effective enema volume is 22 mL/kg (range: 5-48 mL/kg), with no patient requiring more than 48 mL/kg daily to achieve bowel management. 9
• Large-volume enema administration requires an experienced healthcare professional due to perforation risk. 3
• The volume needed to fill the colon on contrast enema has limited value (R² = 0.21) in predicting effective therapeutic saline enema volume. 9

Osmolality Effects

• Sodium-based enemas induce rapid fluid absorption even when moderately hyper-osmolal (~350 mOsm) compared to blood (~300 mOsm), suggesting active sodium absorption plays a key role. 6
• Moderately hypotonic enema formulations cause little to no detectable epithelial damage, while hypertonic solutions cause significant damage including epithelial sloughing. 6

Perforation Risk

• Perforation occurs in approximately 0.02% to 0.04% of patients (1 in 1,000 procedures), with a mortality rate of 38.5% when it occurs. 3, 8
• Inflation of a retention balloon within a stricture, neoplasm, inflamed rectum, or colostomy stoma is particularly hazardous. 8
• Injury to the rectal mucosa or anal canal from the enema tip or retention balloon is the most common traumatic cause of perforation. 8
• Intraperitoneal perforation leads to severe acute peritonitis with intravascular volume depletion and potentially fatal shock requiring prompt fluid replacement and laparotomy. 8

Other Serious Complications

• Bacteremia occurs in up to 23% of patients following enema administration, particularly dangerous in immunocompromised patients. 4, 5, 8
• Venous intravasation of barium is rare but may be immediately lethal, most often attributed to trauma from the enema tip or retention balloon. 8
• Electrolyte abnormalities (hyperphosphatemia, hypokalemia) especially with sodium phosphate enemas can occur. 4
• Sodium phosphate enemas should not be used in children younger than 12 years and are contraindicated in renal disease due to risk of fatal hyperphosphatemia. 4

Algorithmic Approach to Enema Use

Step 1: Exhaust Oral Therapy First

• Start with polyethylene glycol (PEG) 17g with 8 oz water twice daily PLUS senna or bisacodyl as first-line therapy for chronic constipation. 4
• Ensure adequate fluid intake and mobility within patient limits. 4
• Goal is one non-forced bowel movement every 1-2 days. 4

Step 2: Screen for Contraindications

• Review anticoagulation status, blood counts, recent procedures, radiotherapy, and bowel obstruction symptoms before considering any enema. 4, 5, 3

Step 3: Select Appropriate Enema Type

• For acute constipation rescue: Normal saline enema (500-1000 mL in adults, 10 mL/kg in children) is preferred due to lower mucosal irritation. 4, 3
• For diagnostic purposes: Water-soluble contrast if leak/perforation suspected; barium only if bowel integrity confirmed. 2
• For medication delivery: Moderately hypotonic formulation for local effect, hypertonic for systemic absorption. 6

Step 4: Monitor for Complications

• Never ignore abdominal pain during or after enema administration - this may indicate perforation requiring emergency surgery. 5, 3
• Watch for signs of bacteremia, especially in immunocompromised patients. 4, 5

Common Pitfalls to Avoid

• Never use enemas chronically or routinely - they should be reserved for acute rescue only after oral therapy fails. 4, 3
• Never use sodium phosphate enemas in renal dysfunction - risk of fatal hyperphosphatemia. 4
• Never use tap water for specimen collection in suspected botulism cases - it interferes with laboratory testing; use sterile nonbacteriostatic water instead. 3
• Do not rely on contrast enema volume to predict therapeutic enema volume - individualized titration is required. 9