Diagnostic failure in colonoscopies for malignant disease

Relative efficacy of different MRI signs in diagnosing active Crohn's disease, compared against a histological gold standard

INTRODUCTION

There has been growing interest in the use of MRI in assessing Crohn's disease because of its lack of ionising radiation. Many MRI signs have been described in the literature, but their relative utility is unknown.

METHODS

The MRIs of the bowel performed at 1.5 Tesla were blindly reviewed on 26 patients with recent histology (surgery and/or colonoscopy and their associated reports) according to a dedicated pro forma. Each patient's bowel was divided into nine segments. Each segment was assessed as to the presence or absence of 15 MRI signs described in the literature: abnormal gadolinium enhancement (both subjective and objective), wall oedema, fat oedema, fat proliferation, nodal enlargement, free fluid, wall nodularity, serosal blurring, mural thickening >4 mm, stricture, multi-segmental disease, fistula, abscess and layered contrast enhancement. The results were compared against a histological gold standard with a six-point scale of disease severity.

RESULTS AND CONCLUSIONS

MRI correctly identified all 15 patients with at least established mucosal disease, and three of eight with only mild mucosal disease. Combining these results, a positive MRI correlated highly with at least early mucosal disease (positive predictive value 95%), while the presence of established mucosal disease was unlikely if MRI was negative (negative predictive value 100%). The MRI signs found to be the most sensitive for detecting active Crohn's disease were those related to the bowel wall, namely, wall thickening, nodularity, contrast enhancement and oedema. The most specific signs were the presence of multi-segmental disease, layered contrast enhancement and complications (fistula and abscess).

What are the sensitivity and specificity of endoscopic photographs in determining completion of colonoscopy? Results from an online questionnaire

OBJECTIVES

There is no consensus as to the optimal method for documenting colonoscopy completion. For endoscopic photographs to be useful for documentation, reviewers must be able to distinguish between photographs taken from incomplete and complete colonoscopy. The primary aim of this study was to calculate the diagnostic specificity and sensitivity of a pair of photographs in confirming complete colonoscopy. The secondary aim was to assess current methods of documenting colonoscopy completion.

METHODS

Eighty pairs of photographs were taken from completed colonoscopies. Two photographs, including at least one view of the ileo-caecal valve, were taken of caecal landmarks and/or the terminal ileum. Colonoscopy completion was independently validated using video clips. Twenty pairs of photographs were also taken from another colonic site that could potentially be misinterpreted as the caecum, for example, hepatic flexure. Using an online questionnaire 34 experienced endoscopists were asked about their own methods of colonoscopy documentation. Thirty-two of these reviewers then assessed the 100 photographic pairs, blinded to their origin, and were asked 'Taking both photographs into account, are you convinced that complete colonoscopy has been performed?'

RESULTS

Fifty-six percent of endoscopists did not routinely use any objective method of documentation although 38% frequently used some photographs for documentation. Using a pair of endoscopic photographs to document colonoscopy completion has a sensitivity of 51.4% (confidence intervals: 49.5-53.3%) and a specificity of 89.2% (confidence intervals: 86.8-91.6%).

CONCLUSION

Both the sensitivity and the specificity of a pair of endoscopic photographs are too low to be used for reliably documenting colonoscopy completion.

Errors in cancer diagnosis: current understanding and future directions

PURPOSE

Errors in cancer diagnosis are likely the most harmful and expensive types of diagnostic errors. We reviewed the literature to understand the prevalence, origins, and prevention of errors in cancer diagnosis, focusing on common cancers for which early diagnosis offers clear benefit (melanoma and cancers of the breast, colon, and lung).

METHODS

We searched the Cochrane Library and PubMed from 1966 until April 2007 for publications that met our review criteria and manually searched references of key publications. Our search yielded 110 studies, of which nine were prospective studies and the remaining were retrospective studies.

RESULTS

Errors in cancer diagnosis were not uncommon in autopsy studies and were associated with significant harm and expense in malpractice claims. Literature on prevalence was scant. For each type of cancer, we classified preventable errors according to their origins in patient-physician encounters in the clinic setting, diagnostic test or procedure performance, pathologic confirmation of diagnosis, follow-up of patient or test result, or patient-related delays.

CONCLUSION

The literature reflects advanced knowledge of contributory factors and prevention for diagnostic errors related to the performance of procedures and imaging tests and emerging understanding of pathology errors. However, prospective studies are few, as are studies of diagnostic errors arising from the clinical encounter and patient follow-up. Future research should examine further the system and cognitive problems that lead to the many contributory factors we identified, and address interdisciplinary interventions to prevent errors in cancer diagnosis.

Inadequacy of colonoscopy revealed by three-dimensional electromagnetic imaging

INTRODUCTION

It is generally accepted that clinicians performing colonoscopy should reach the cecum in at least 90 percent of examinations. However, little attention has been paid to whether the endoscopist correctly estimates the amount of colon actually seen.

METHODS

During colonoscopy, endoscopists were asked to state how far they had reached. This was compared with the amount of colon actually seen, as assessed by a novel electromagnetic imaging device that recorded a three-dimensional position of the scope within a magnetic field pervading the patient's abdomen. If electromagnetic imaging showed that the cecum had not been reached, the endoscopist was asked to use the electromagnetic imaging system to determine whether it helped advance the colonoscope further.

RESULTS

In 119 patients undergoing colonoscopy, clinical assessment of position reached was correct in only 92 (77.3 percent). When the endoscopists stated that cecal landmarks had been seen (n = 85), the scope was distal to the cecum in seven cases (8.2 percent). When cecal landmarks had not been seen (n = 34), the endoscopist's assessment of the position of the scope was accurate in only 14 (41.2 percent). The use of electromagnetic imaging in this latter group assisted passage to the cecum in 26 cases (76.5 percent).

CONCLUSION

Despite assumed visualization of the cecum, inadequate colonoscopy highlights the potential for missing significant pathology in the right colon.

Effect of magnetic endoscope imaging on colonoscopy performance: a randomised controlled trial

BACKGROUND

Colonoscopy can be technically challenging because of unpredictable colonoscope looping. Without imaging, straightening the colonoscope is sometimes difficult since the endoscopist has to guess where the tip is. Magnetic endoscope imaging (MEI), a new non-radiographical technique for picturing the colonoscope shaft in real time, could facilitate loop straightening and thus improve performance.

METHODS

We assessed trainees and endoscopists with much experience of routine outpatient colonoscopy. In group 1, trainees examined 113 consecutive patients. MEI views were recorded in all examinations, but procedures were randomised to be done by two trainees, either with the endoscopist and endoscopy assistants viewing the imager display (n=58), or without the imager view (n=55). In group 2, two skilled endoscopists were randomised (as with group 1) to undertake consecutive examinations (n=183) either with (n=92) or without (n=91) the MEI view. MEI views of all procedures were analysed retrospectively.

FINDINGS

In both groups, intubation times were shorter (median 11.8 min [4.3-31.5] vs 15.3 min [4-67] [group 1]; 8.0 min [2.6-40.8] vs 9.3 min [2.5-52.6] [group 2]) and number of attempts at straightening the colonoscope fewer (median 5 [0-20] vs 12 [0-57] [group 1]; 7 [0-55] vs 10 [0-80] [group 2]), when the endoscopist was able to see the imager view. In group 1, colonoscopy completion rates were also higher (100% [58] vs 89% [49]) and duration of looping was reduced (median 3 min [0-18.8] vs 5.4 min [0-44.5]) when the imager could be seen. Abdominal hand pressure was more effective when the endoscopist and endoscopy assistant could see the imager view.

INTERPRETATION

MEI significantly improves performance of colonoscopy, particularly when used by trainees, or by experts in technically difficult cases; loops were straightened or controlled effectively, resulting in quick intubation times and high completion rates.