What are the potential complications of colonoscopy?

Complications of Colonoscopy

Colonoscopy carries three major complications that can impact morbidity and mortality: post-polypectomy bleeding (most common serious complication), perforation (occurring in approximately 1 in 1,000 procedures), and cardiopulmonary events related to sedation (representing half of all adverse events). 1

Major Complications

Post-Polypectomy Bleeding

• Bleeding is the most common serious complication of colonoscopy, occurring in approximately 4.8 per 1,000 colonoscopies with polypectomy. 2
• Risk increases significantly with large polyp size (>2 cm) and proximal colon location. 1
• Small polyp bleeds are paradoxically more numerous overall because small polyps are so common. 1
• Secondary hemorrhage is unpredictable, occurring 1-14 days post-procedure. 3
• Most bleeding cases can be managed colonoscopically without surgery or angiography. 4

Perforation

• Overall perforation rate is approximately 0.07% (1 in 1,000 screened patients), with diagnostic colonoscopy having lower rates (0.03-0.08%) compared to therapeutic procedures (0.1-0.3%). 1, 5
• In Medicare populations, perforation occurs in 1 in 500 procedures due to age-related risk. 1
• The sigmoid colon is the most common perforation site (72% of cases). 6
• Diagnosis is frequently delayed in 58% of patients, leading to peritoneal contamination in 59% of cases. 6
• Mortality from colonoscopic perforation requiring emergency surgery reaches 14%, with postoperative mortality of 12%. 6

Risk factors for perforation include: 1, 5, 7

• Age >67 years
• Presence of diverticular disease
• Therapeutic procedures (polypectomy, EMR, ESD)
• Chronic steroid use
• Recent abdominal/pelvic radiation
• Multiple comorbidities (diabetes, chronic lung disease, heart failure, peripheral vascular disease, renal insufficiency)

Cardiopulmonary Complications

• Cardiopulmonary events represent approximately 50% of all adverse events during colonoscopy and are usually related to sedation. 1
• Include cardiac arrhythmias, hypotension, and oxygen desaturation. 1
• These events rarely result in hospitalization but require immediate recognition. 1
• One death in a series of 5,000 colonoscopies was attributed to oversedation-related cardiorespiratory arrest. 3

Overall Complication Rates

• Serious complications occur in 5.0 per 1,000 colonoscopies overall. 2
• Colonoscopy without biopsy or polypectomy: 0.8 per 1,000 procedures. 2
• Colonoscopy with biopsy or polypectomy: 7.0 per 1,000 procedures (9.2-fold increased risk). 2
• Mortality within 30 days occurs in approximately 0.06% of procedures, with only a fraction directly attributable to colonoscopy. 2

Less Common Complications

Post-Polypectomy Syndrome

• Occurs in approximately 1% of patients following polypectomy. 4
• Presents with abdominal pain, fever, and leukocytosis without frank perforation. 4
• Most cases resolve without surgical intervention. 4

Infection and Septicemia

• Risk increases in specific clinical situations requiring recognition and prophylaxis. 3
• Bacterial translocation can occur, particularly with underlying ischemia or inflammation. 8

Other Complications

• Thrombophlebitis at IV sites. 3
• Abdominal distension from insufflation. 3
• Vasovagal episodes. 3
• Rare gas explosions (historical concern with inadequate bowel preparation). 9

Critical Clinical Pitfalls

Absolute contraindications that must be recognized: 5, 7

• Known or suspected intestinal perforation
• Acute peritonitis

Relative contraindications requiring delay: 5, 7

• Acute diverticulitis (postpone minimum 6-8 weeks)
• Complete colonic obstruction
• Uncorrected coagulopathy
• Hemodynamic instability

Common errors leading to complications: 3, 6

• Oversedation causing cardiorespiratory compromise
• Failure to review prior imaging for large polyps at high bleeding risk
• Delayed recognition of perforation (occurring in 58% of cases)
• Traumatic instrumentation in patients with ischemic colitis
• Proceeding with colonoscopy in hemodynamically unstable patients

Operator and System Factors

• Colonoscopy is highly operator-skill dependent, with less experienced endoscopists having higher complication rates. 1, 7
• Complication rates decreased by 50% in the second half of one large series due to improved experience and instrumentation. 3
• Formal quality-assurance programs are essential but historically lacking. 1
• The miss rate for large adenomas (≥10 mm) is 6-12%, and for cancer is approximately 5%. 1