Introduction Colonoscopy, CT colonography (CTC) and barium enema have been used to detect Colorectal Cancer (CRC). A diagnosis of CRC following a false-negative investigation represents a missed opportunity and may lead to adverse clinical outcomes. The literature describes various rates for missed CRC with some authors suggesting patients be consented for between 2–6%.¹ We present audit data from our NHS Trust looking at the miss rate of CRC following these investigations in both symptomatic and screened patients.

Methods We retrospectively audited the computerised (EZNotes) case notes and investigations of patients with a diagnosis of CRC between January-December 2013. Patients were sourced from the Somerset cancer registry and National Bowel Cancer Audit (NBOCA). We recorded whether patients had been investigated with colonoscopy, CTC or barium enema in the preceding 6 to 36 month period, obtaining a rate for false-negative investigations i.e a missed diagnosis of CRC.

Results 385 patients had a diagnosis of CRC made within the period. Of 291 colonoscopies performed, 17 missed a diagnosis made in the preceding 6–36 month period equating to a 6% miss rate. The mean time delay between date of colonoscopy in PCCRCs and date of diagnosis was 613 days (range 201–1075). 38% of these missed cancers were in the right colon and 39% were found in the rectum and sigmoid. 62% of patients had concomitant diverticular disease.

Of 32 CTCs undertaken 3 missed a CRC and of 11 barium enemas performed 5 CRCs were missed.

11% of patients presented as emergencies, 14% via bowel cancer screening and the remaining 75% presented with symptoms, from surveillance or with a significant family history.

Conclusion Colonoscopy is the best test for detecting CRC but missed cancers still occur. The missed CRC rate found in this audit was comparable to published series. Several factors seem to be associated with false negative investigations; right sided cancers are often cited as more susceptible to misses due to anatomy and technical difficulties. We found that rectal cancers were missed in comparable numbers to right sided cancers, and suggest that particular care is taken when diverticular disease is present. Extra time should be taken in the caecum and hepatic flexure as “review areas” where misses are more likely to occur. Ongoing audit as well as improved endoscopy training and technology will ensure that rates of missed CRC are reduced.

Reference 1 Bressler B, et al. Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis. Gastroenterology. 2007 Jan;132(1):96–102.

Disclosure of Interest None Declared