Likelihood of missed and recurrent adenomas in the proximal versus the distal colon

Gastrointest Endosc. 2011 Aug;74(2):253-61. doi: 10.1016/j.gie.2011.02.023. Epub 2011 May 6.


Background: Colonoscopy may be less efficacious in reducing colorectal cancer mortality in the proximal compared with the distal colon. A greater likelihood for missed and recurrent adenomas in the proximal colon may contribute to this phenomenon.

Objective: To examine whether a proximal adenoma is associated with the risk and location of missed and recurrent adenomas.

Design: Prospective.

Setting: Polyp Prevention Trial.

Participants: A total of 1864 patients with an adenoma at baseline underwent a follow-up colonoscopy 4 years later (adenoma recurrence). Of these, 1731 underwent a clearing colonoscopy 1 year after the baseline examination (missed adenoma).

Main outcome measurements: Association of baseline adenoma location with the risk and location of adenomas found at colonoscopy performed 1 year and 4 years later.

Results: At the year 1 colonoscopy, 598 patients (34.6%) had an adenoma (missed adenoma). Compared with those with a distal-only adenoma at baseline, patients with a proximal-only adenoma at baseline were more likely to have any missed adenomas (relative risk [RR] 1.28; 95% CI, 1.09-1.49) and a proximal-only missed adenoma (RR 2.05; 95% CI, 1.49-2.80). At the year 4 colonoscopy, 733 patients (39.3%) had adenoma recurrence. Patients with a baseline proximal-only adenoma were more likely to have any adenoma recurrence (RR 1.14; 95% CI, 1.00-1.31) and a proximal-only adenoma recurrence (RR 1.52; 95% CI, 1.15-2.02). Sensitivity analyses involving missed adenomas did not materially affect the risk or location of recurrent adenomas at year 4 colonoscopy.

Limitation: Lesions may still be missed on repeated colonoscopies.

Conclusions: Missed and recurrent adenomas are more likely to be in the proximal colon.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Adenoma / diagnosis*
  • Aged
  • Colon, Ascending / pathology*
  • Colon, Descending / pathology*
  • Colon, Sigmoid / pathology*
  • Colon, Transverse / pathology*
  • Colonic Neoplasms / diagnosis*
  • Colonoscopy
  • False Negative Reactions
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local / diagnosis*
  • Prospective Studies
  • Regression Analysis
  • Risk Factors