Introduction To evaluate the risk of colorectal cancer in a 5-year period after a negative colonoscopy (PCCRC).
Methods Data of patients undergoing colonoscopy in a 1-year period from January to December 2004 collected from endoscopy database (847 cases), and matched electronically with patients diagnosed with CRC in the next 5 years. 60 matches were made. Exclusion criteria: Patients detected to have cancers by colonoscopy in 2004 (44 cases). Inclusion criteria: Patients with negative colonoscopy in 2004 with CRC from 2005 to 2009 were included (n=803).
Results Four patients with negative colonoscopy in 2004 were diagnosed with CRC between 2005 to 2009.
Case 1: M78 with diverticular disease in 2004 and iron deficiency anaemia 2005. OGD showed pyloric ulcer. Colonoscopy deferred as negative 1 year ago. In 2006 found to have caecal cancer.
Case 2: M43 known IBD, on surveillance with negative colonoscopy in 2004 had low rectal cancer in 2005.
Case 3: M66 had four adenomas (ascending colon, hepatic flexure, splenic flexure and 20 cm from anal verge) removed in July 2004. Rectal Malignancy detected in 2005.
Case 4: F76 incomplete colonoscopy in 2004 due to a tight sigmoid diverticular stricture, developed sigmoid cancerin 2008.
4 PCCRCs (1 Caecal, 1 Sigmiod, 2 Rectal) detected out of 803 patients in an interval of 5 years with a miss rate of 0.49% over 5 years. Three were males. Age range 43–78 years.
Conclusion What is known: Previous studies1 have shown that female sex diverticular disease, older age,2 3 right sided cancers1–5 IBD, incomplete colonoscopy2 3 are all risk factors for missed CRCs. What this study found: 3 out of 4 missed cancers were in males and 3 out of 4 were left sided cancers, two of them in rectum. Our miss rate was 4/803 that is 0.49% compared to an average of 5% in other studies1–6 and similar to the miss rate in the National Polyp study. What this study adds: Diligent examination of the rectum is important; particularly in IBD patients on surveillance. It is important to retroflex in rectum to inspect the anal verge. Left sided cancers comprised the major part of missed cancers.
Competing interests None declared.
References 1. Bressler B, et al. Rates of new or missed colorectal cancers after colonoscopy and their risk factors. Gastroenterology 2000.
2. Shah HA, et al. Factors associated with incomplete colonoscopy. Gastroenterology 2007.
3. Aslinia F, et al. Quality assessment of colonoscopic cecal intubation: an analysis of 6 years of continuous practice at a university hospital. Am J Gastroenterology 2006.
4. Lakoff J, et al. Risk of developing proximal versus distal colorectal cancer after a negative colonoscopy. Clin GastroenterolHepatol 2008.
5. Rex DK, et al. Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer. Gastroenterology 1997.
6. Winawer SJ, et al. Prevention of colorectal cancer by colonoscopic polypectomy.The National Polyp Study. N Engl J Med 1993.
- Post colonoscopy colorectal cancer (PCCRC)