Signs of Fecal Impaction
Fecal impaction is diagnosed by digital rectal examination (DRE) revealing a large mass of dry, hard stool in the rectum, though proximal impactions in the sigmoid colon will have a non-diagnostic DRE. 1
Primary Clinical Presentation
Cardinal Signs
- Large mass of compacted, dry, hard stool in the rectum or proximal colon that cannot be evacuated 1, 2
- Paradoxical overflow diarrhea - watery stool leaking around the impaction from higher in the bowel 1, 3
- Abdominal discomfort or pain - often chronic and progressive 1
- Inability to pass stool despite urge to defecate 2
Associated Symptoms
- Rectal fullness or pressure sensation 1
- Abdominal distension or bloating 1
- Nausea and vomiting in severe cases 3
- Loss of appetite 2
- Urinary symptoms - frequency, retention, or incontinence due to mass effect 1
Physical Examination Findings
Rectal Examination (Most Important)
- Palpable hard stool mass on DRE - confirms distal impaction 1
- Empty rectum on DRE - suggests proximal sigmoid or colonic impaction 1
- Rectal distension 1
Abdominal Examination
- Palpable abdominal mass - may feel firm fecal matter through abdominal wall 1
- Abdominal tenderness - variable severity 1
- Tympany on percussion - from associated bowel distension 1
Critical Warning Signs of Complications
These signs indicate potentially life-threatening complications requiring urgent intervention: 1, 4
- Severe, unrelenting abdominal pain - suggests ischemia or perforation 4
- Fever - indicates infection or perforation 5
- Tachycardia - sign of systemic compromise 5
- Peritoneal signs (guarding, rebound tenderness) - suggests perforation 5, 4
- Rectal bleeding - may indicate stercoral ulceration 1
- Signs of bowel obstruction - complete absence of flatus, severe distension, vomiting 6, 4
- Altered mental status - particularly in elderly patients 1
Serious Complications to Recognize
The ESMO guidelines emphasize that while uncommon, complications include 1:
- Urinary tract obstruction from mass effect 1
- Colonic perforation - can be catastrophic 1, 4
- Stercoral ulcers with bleeding 1
- Rectal necrosis from pressure ischemia 4
- Abdominal compartment syndrome in massive impaction 4
- Dehydration and electrolyte imbalance 1
- Renal insufficiency 1
Diagnostic Approach
Clinical Assessment
- Complete history focusing on constipation duration, laxative use, and risk factors (opioid use, immobility, advanced age, neurologic disease) 1
- Systematic DRE - essential first step, though may miss proximal impactions 1
When DRE is Non-Diagnostic
- Plain abdominal radiography - can identify proximal impactions 1
- CT imaging - for suspected complications or unclear diagnosis 1
Common Clinical Pitfalls
The most dangerous pitfall is mistaking overflow diarrhea for infectious gastroenteritis, leading to inappropriate antidiarrheal medication that worsens the impaction 1, 3. The NCCN guidelines note this presentation can cause significant diagnostic confusion 1.
In elderly or cognitively impaired patients, symptoms may be subtle or atypical, with only behavioral changes or decreased oral intake as presenting signs 1, 2. Always maintain high clinical suspicion in high-risk populations.
Rectal bleeding should prompt evaluation for stercoral ulceration rather than being dismissed as hemorrhoidal bleeding 1, 7, 8.