colonoscopy

Introduction

A procedure for viewing the entire length of the colon to the ileocecal valve. Viewing the distal ileum may be indicated if enteritis is suspected.

Indications

• rectal bleeding
• unexplained abdominal symptoms
• equivocal or abnormal barium enema
• removal or search of polyps (see intestinal polypectomy)
• search for & biopsy of suspected carcinoma
• follow-up for colorectal cancer or adenomatous polyp(s)
• intraoperative colonoscopy
• unexplained weight loss
• metastatic carcinoma of unknown primary
• unexplained chronic diarrhea
• unexplained iron-deficiency anemia
  • serum ferritin < 100 mg/mL suggested as indicator
• screening for colorectal carcinoma
  • 10 year interval sufficient
  • reduces risk of colorectal cancer by 18% but does not reduce 10 year cancer-related deaths
  • extension of 10-year screening intervals may be warranted, especially for female & younger patients
• surveillance

Contraindications

• patient refusal
• patient is dying or at the point of death (moribund)
• known or suspected perforation
• unavailability of resuscitation
• unstable cardiac condition
• respiratory insufficiency
• elderly > 75 years with limited life expectancy

Clinical significance

• Sensitivity:
  • 89% for polyps > 5 mm in size
  • may miss 2-4% of colon cancers
  • better in the left colon than in the right
  • colonoscopy might not provide any substantial protection in the right colon
• Screening:
  • reduction in mortality?
    • 57% reduction in colon cancer deaths
      • absolute 10 year risk reduction for normal colonoscopy at 56 years of age = 0.1%
    • no reduction in 10 year colorectal cancer mortality or all-cause mortality
  • 56% risk reduction for right-sided colon cancer
  • 84% risk reduction for left-sided colon cancer
  • colorectal cancer found in 0.5% of colonoscopies
  • high-risk adenomas found in 3.2% of colonoscopies
  • reduction in colorectal cancer within 10 years 0.98% vs 1.20%
• surveillance
  • colorectal cancer detection at surveillance colonoscopy rare among older adults regardless of prior adenoma finding
  • advanced neoplasia detection was more common in elderly with prior advanced adenoma vs nonadvanced adenoma

Procedure

Patient preparation:

• informed consent
• one day prior to procedure*
  • clear liquids with no red or orange gelatin
  • metoclopramide 10 mg at 11 AM & 3 PM
  • Colyte 4 liters (2 glasses every 30 min) beginning at 1 PM
  • evening/morning split dose sodium phosphate - two 45 mL bottles given 6, 12 or 24 hours apart outperforms Colyte
• procedure preparation
  • intravenous access
  • cardiac rhythm monitor
  • pulse oximetry
  • O2 if indicated
  • resuscitation equipment
  • left lateral position with right knee flexed more than left
• walking aids bowel preparation
• inadequate bowel preparation should be followed by repeat colonoscopy
  • exception: mass lesions including colonic polyps >= 5 mm can be excluded, despite the indadequate preparation

* see bowel preparation for colonoscopy or flexible sigmoidoscopy

Sedation:

• adequate sedation is achieved when the patient develops slurred speech
• pharmacologic agents
  • intravenous benzodiazepine & opioid combination (standard)
  • meperidine (Demerol) 50-100 mg IV
  • midazolam (Versed) 0.5 mg increments
  • morphine 5-10 mg IV
  • diazepam (Valium) 5-20 mg IV
  • fentanyl (Sublimaze) 0.05-0.1 mg IV
• sedation reversal
  • should be available
  • naloxone (Narcan) 0.4 mg IV up to 2 mg
  • flumazenil (Mazicon, Romazicon)
    • 0.2 mg IV over 15 seconds every min up to 1 mg

Technique:

• retroflexion may be useful for polypectomy
• narrow-band imaging & chromoendoscopy are techniques used to identify polyp characteristics (pit morphology)
• policy of at least 7 minutes examining the colonic mucosa during colonoscopy withdrawal (guideline) has no effect on polyp yield
• apparently, 2 pairs of eyes better than 1
  • nurse paired with gastroenterologist viewing colon detect 28% more adenomas than gastroenterologist alone
• endocuff-assisted colonoscopy improves cecal intubation rate & may improve adenoma detection
• repeat examination of the right colon during colonoscopy with higher colorectal adenoma detection rate 27% than single pass 22%
• adenoma detection rate may be an emerging quality measure
  • gastroenterologists detect more adenomas than other endoscopists

Complications

• bacteremia, hemorrhage, colonic perforation, serosal tears, abdominal distention, vasovagal reflex, splenic avulsion, cardiac arrhythmias, volvulus, toxic megacolon, pneumoperitoneum
• significant complications: 5/1000 to 2.5/1000
  • perforation: 1/2500; 1/1000; 0.07%;1/1200; 1/10,000*; 3/100,000 (without intervention) 6/100,000 with intervention; 5.8/10,000 unrelated to polypectomy[48]; 0/12,000
    • gastrointestinal bleeding & perforation observed/expected ratios > 1 at all ages within 0-60 days of colonoscopy
    • diverticulosis, inflammatory bowel disease, glucocorticoid use, certain comorbid conditions increases risk
    • provider factors (experience, volume, performance by non-gastroenterologist influences risk
  • post-polypectomy serosal burns 0.02%
  • bleeding
    • major bleeding 14/12,000
    • bleeding due to polypectomy (0.14%); 2.4/1000
      • polyp size risk factor
    • bleeding requiring hospitalization 1/600
  • complications resulting in emergency department visit: 1%
  • death: 1/55,000; 1/20,000; 1/14,000; 3/100,000
• risk factors for complications
  • older age, male, polypectomy, low-volume endoscopist
  • history of stroke, COPD, atrial fibrillation, or congestive heart failure
• other
  • myocardial infarctions & ischemic stroke predominated over intestinal perforation in elderly > 75 years
  • cardiovascular & pulmonary complications related to sedation
  • postpolypectomy electrocoagulation syndrome (0.003-1%)
  • gas explosion
  • injury to spleen (rare, but likely under-reported)

* study reports unsually low rate of complications & unsually high rate of pathologic findings (no discussion regarding financial implications for GI endoscopists)

Management

• antithrombotics/anticoagulants/antiplatelet agents
  • in general, stop most antithrombotics before a colonoscopy due to increased risk of bleeding with polypectomy
    • aspirin is an exception, continue aspirin in most cases
    • stop warfarin, clopidogreal 5 days prior to the procedure
    • stop dabigatran, rivaroxaban, apixaban 1-2 days prior to the procedure
    • if risk of procedure is high, bridge warfarin with LMW heparin
  • if polypectomy is not performed, restart antithrombotics immediately following the procedure.
  • if polypectomy is performed
    • restart warfarin about 12 hours after the procedure
    • restart dabigatran, rivaroxaban, apixaban about 48-72 hours after the procedure
    • restart clopidogrel 24 hours after the procedure
• Post-procedure:
  • observe patient until fully awake
  • instruct patient to notify physician for:
    • fever/chills
    • abdominal pain
• risk of colon cancer diminished after negative colonoscopy
  • absolute 10 year risk reduction for normal colonoscopy at 56 years of age = 0.1%
• afternoon colonoscopies have higher failure rates than morning colonoscopies
• risk factors for new (within 6-36 months) or missed cancers
  • older age
  • diverticular disease
  • large serrated polyps (adenomatous polyps)
  • right-sided or transverse colon cancers
  • advanced adenomas may be associated with risk colon cancer
    • nonadvanced adenomas may not be associated with risk
  • inadequate training or experience (colonoscopy by internist or family practice)
  • inadequate facilities (office-based rather than hospital-based)
• repeat colonoscopy may detect source of obscure bleed

Notes

• repeat colonoscopies common among Medicare patients without clear indication
• ~ 25% of colonoscopies in elderly may be inappropriate
• complication rate is much higher in patients > 90 years of age than in patients 75-79 years of age (9.2% vs. 0.7%), mostly due to cardiopulmonary events
  • colon cancer is much more frequent in patients > 90 (14% vs. 2%) (%s for patients with indications for colonoscopy, not screening)
• even in Veterans Administration surveillance colonoscopy is overused
• 3-fold increased risk of early/missed colon cancer in patients with inflammatory bowel disease
  • 5.8-6.8% in patients without inflammatory bowel disease
  • 15.1-16.5% in patients with Crohn disease
  • 15.8-18.8% in patients with ulcerative colitis
• patients generally know whether their colonoscopy found polyps but do not know the characteristics of the polyps
• higher adenoma detection rates linked to lower colorectal cancer risk
• older black persons more likely than older whites for colorectal cancer diagnosis within 5 years after colonoscopy (7.1% vs 5.8%)

More general terms

• gastrointestinal endoscopy

More specific terms

• colonoscopy through stoma
• colonoscopy with cautery
• colonoscopy with dilation of stricture
• colonoscopy with polypectomy
• colonoscopy with removal of foreign body
• fluorescence-guided colonoscopy

Additional terms

• adenocarcinoma of the colon &/or rectum
• bowel preparation (whole bowel irrigation, bowel evacuation)
• colonoscope
• flexible sigmoidoscopy
• intestinal polypectomy
• screening for colon cancer
• virtual (CT) colonoscopy (CT colonography)

Patient information

colonoscopy patient information