Towards appropriate imaging: Tips for practice.

BACKGROUND: The best use of diagnostic imaging is a challenge for many health professionals and the health system. Potential hazards of inappropriate imaging include exposure to ionising radiation, false positive and negative results, unexpected incidental findings, overdiagnosis and cost. OBJECTIVE: Using a fictional case, we aim to illuminate and discuss some of the challenges to appropriate diagnostic imaging and offer some solutions. DISCUSSION: While normal imaging results can reassure a patient, abnormal incidental findings can sometimes cause harm. When serious disease is very unlikely, verbal reassurance may be more appropriate than imaging. We remind doctors of the risks of ionising radiation, including how to access resources to estimate these risks and the need to ensure that the potential benefit of the test outweighs the risk - the process of justification. We point readers to imaging guidelines to help guide decision-making, such as the 'Diagnostic imaging pathways' resource. We look forward to relationships between radiologists and general practitioners characterised by collaboration and consultation, rather than just ordering and reporting.

Crohn's disease activity: quantitative contrast-enhanced ultrasound assessment.

OBJECTIVES: To determine whether quantitative parameters from contrast-enhanced ultrasound examination (CE-US) of the bowel wall correlate with endoscopic inflammatory activity in Crohn's disease and to assess its utility in the follow-up of patients on treatment. METHODS: This was a prospective study of 30 patients with Crohn's disease requiring colonoscopy or flexible sigmoidoscopy. The Crohn's disease activity index (CDAI), serum C-reactive protein (CRP) and Crohn's disease endoscopic index of severity (CDEIS) were calculated. CE-US was performed within 7 days of endoscopy using intravenous perflutren lipid microsphere and repeated a median of 45.5 days following treatment. Time-intensity curves of bowel wall enhancement were generated to derive the area under the curve (AUC), time to peak intensity (TTP) and peak intensity (PI). RESULTS: In separate multivariate regression models, the AUC, TTP and PI showed no significant association with endoscopic activity whilst controlling for CDAI and CRP. However, the reductions in CDAI and CRP following treatment were mirrored by significant reductions in TTP (P = 0.05). CONCLUSIONS: CE-US does not appear to predict for Crohn's disease endoscopic activity independent of simple parameters such as CDAI and CRP. However, it may be useful in the serial assessment of patients on treatment.

Diagnostic imaging: Doing the right thing.

Inappropriate diagnostic imaging (DI) is a burgeoning issue and embraces its overuse and its misapplication. The obverse problem is one of underuse - that is when patients who should undergo imaging fail to do so. This article attempts to define these problems, examines the causes and effects and suggests some potential solutions.

Computed tomography in the assessment of suspected large bowel obstruction.

BACKGROUND: The aim of this study was to assess the efficacy of computed tomography (CT) scanning in the diagnosis of acute large bowel obstruction. METHODS: Forty-four patients (22 men; 22 women, ages 39-94 years, mean 71 years) with clinical features and abdominal radiographic findings suggesting acute large bowel obstruction (LBO) or pseudo-obstruction were examined with CT. Supine scans were obtained with i.v. contrast medium (unless contraindicated), but (in the majority) without oral contrast. Additional prone and/or decubitus scans were obtained in 33 patients when clarification of a possible transition point on the supine scan was required. CT diagnosis of LBO was made by finding a transition point +/- mass. Final diagnosis was confirmed by surgery, further imaging and/or clinical course. RESULTS: Twenty-two patients had proven mechanical acute LBO of whom 18 had an obstructing carcinoma; 22 patients had no mechanical obstruction. Sensitivity, specificity, Positive Predictive Value, Negative Predictive Value of CT for diagnosis of mechanical LBO were each 91%. Positive and negative likelihood ratios were 10.1 and 0.1, respectively. There were two false-negative CT scans, although one of these was reported as showing segmental mural thickening. A mass was identified on 14 of 17 patients with true-positive CT, subsequently found to have carcinoma. CONCLUSION: Computed tomography with additional selective prone and/or decubitus scanning is highly effective in the diagnosis of mechanical LBO. It is suggested that it replace contrast enema as the initial imaging method.

Vascular complications of pancreatitis.

Vascular complications of pancreatitis are a major cause of morbidity and mortality. Arterial complications include haemorrhage from direct arterial erosion or pseudoaneurysm formation, and visceral ischaemia. Venous complications predominantly are related to splanchnic vein thrombosis. This review, with illustrative cases, describes the main manifestations of these complications and emphasizes the importance of early radiological diagnosis and intervention.

Influences on participation in a community-based colorectal neoplasia screening program by virtual colonoscopy in Australia.

OBJECTIVE: To determine the effect of certain personal and health behaviour characteristics on participation in a community-based colorectal neoplasia (CRN) screening program using virtual colonoscopy. METHODS: The study population comprised randomly selected subjects from the State electoral roll; screening by virtual colonoscopy was offered through letter of invitation. For non-responders, a further invitation was sent a month later. Non-response after a further month led to subjects being considered non-participants. Non-participants were contacted by letter to complete a structured questionnaire; participants completed a similar questionnaire immediately after their screening virtual colonoscopy. RESULTS: Discussing the invitation to screening with someone else increased the likelihood of participation by 63% (prevalence ratio 1.63, 95% CI 1.38-1.93); knowing someone with cancer increased the likelihood of participation by 23% (PR 1.23, 95% CI 1.07-1.42). Among participants who discussed screening with another individual, the spouse was the most common (71%). Subjects who were single were less likely to participate (PR 0.79, 95% CI 0.67-0.94). The strongest reported influence for participation was information provided in the letter of invitation (29.8%). The most common reasons for non-participation were lack of time and perceived good health. CONCLUSIONS AND IMPLICATIONS: This study suggests that a simple strategy to facilitate participation is to encourage subjects to discuss screening with others; further, to recognise that this may be most difficult for those who are single. Information provided to subjects prior to screening positively contributes to participation.

Low-dose computed tomography versus plain abdominal radiography in the investigation of an acute abdomen.

BACKGROUND: To compare low-dose abdominal computed tomography (LDCT) with plain abdominal radiography (AR) in the primary investigation of acute abdominal pain to determine if there is a difference in diagnostic yield, the number of additional investigations required and hospital length of stay (LOS). METHODS: This randomized controlled trial was approved by the institutional review board, and informed consent was obtained. Patients presenting to the emergency department with an acute abdomen and who would normally be investigated with AR were randomized to either AR or LDCT. The estimated radiation dose of the LDCT protocol was 2-3 mSv compared to 1.1 mSv for AR. Pearson's chi-square and the independent samples t-test were used for the statistical analysis. RESULTS: A total of 142 patients were eligible, and after exclusions and omitting those with incomplete data, 55 patients remained for analysis in the AR arm and 53 in the LDCT arm. A diagnosis could be obtained in 12 (21.8%) patients investigated with AR compared to 34 (64.2%) for LDCT (P < 0.001). Twenty-eight (50.9%) patients in the AR group required further imaging during their admission compared to 14 (26.4%) in the LDCT group (P= 0.009). There was no difference in the median hospital LOS (3.84 days for AR versus 4.24 days for LDCT, P= 0.83). CONCLUSION: LDCT demonstrates a superior diagnostic yield over AR and reduces the number of subsequent imaging tests for a minimal cost in radiation exposure. However, there is no difference in the overall hospital LOS between the two imaging strategies.

For discussion: obtaining consent for ionising radiation: has the time come?

The aim of this paper is to promote debate on the issues surrounding the provision of information to, and the obtaining of valid consent from patients exposed to ionising radiation (IR) from diagnostic and interventional imaging procedures. This is especially pertinent in view of recent interest in the risks of IR expressed in the medical and lay press.

Imaging pathways: will they be well trodden or less traveled?

Evidence of inappropriate investigations is not hard to find, and these result in a range of adverse clinical and economic outcomes. An online, evidence-based education and decision support application called Diagnostic Imaging Pathways (DIP) has been developed to assist clinicians to request the most appropriate examinations in the best sequence to achieve diagnoses. The development of the clinical and academic content of DIP and its continuous review and revision involve a network of specialists and general practitioners coordinated by an editorial panel. A research fellow is employed to search the literature, evaluate the evidence, and draft pathways for review. An information technologist develops the Web site, including new functionality, as the scope of the application is expanded. Dissemination is straightforward, with DIP being freely available on the Web (http://www.imagingpathways.health.wa.gov.au). Raising awareness of DIP beyond the immediate clinical environment is challenging. This is assisted through the development of partnerships with national and international entities, which have the core purpose of encouraging evidence-based clinical practice. The greatest challenge, however, is implementation; that is, achieving compliance between requesting practice and recommendations. There is a need to embed DIP into the clinical workflow such that clinicians are guided to choose the "correct" examination. One strategy is to replace paper-based referral processes with an electronic process and to progressively link "electronic requesting" to decision support. Evaluated trials are planned to bring the strategy to the stage of "proof of concept" in Australia.

Computed tomography colonography (virtual colonoscopy): review.

Computed tomography examination of the colon performed after bowel cleansing and distension of the lumen with gas goes by several different names--CT colonography (CTC) and CT colography perhaps being the most common. Strictly, the term 'virtual colonoscopy' (VC), should be reserved for the process of examining 3-D, simulated endoluminal images with a capability to navigate through the bowel using appropriate software. Computed tomography colonography appears to be the name that has gained favour among radiologists, although it is suspected that 'virtual colonoscopy' will persist as a generic term due to its attractive 'high-tech' connotations for non-radiological medical and lay persons. Whatever the name, the technique has been made possible through the advent of fast helical CT scanners which allow acquisition of a volume of data, and of proprietary software which enables multiplanar reformatting and 3-D endoluminal reconstructions. It is evident that if CTC/VC can be shown to be acceptable to patients, safe, affordable and accurate, it has enormous potential as a diagnostic and screening tool for colorectal neoplasia.

Colorectal neoplasia screening with CT colonography in average-risk asymptomatic subjects: community-based study.

PURPOSE: To evaluate computed tomographic (CT) colonography as a screening tool for average-risk asymptomatic subjects with regard to participation, acceptability, and safety. MATERIALS AND METHODS: CT colonography for colorectal neoplasia screening was offered to 2,000 subjects aged 50-54 and 65-69 years. Only asymptomatic subjects at average risk of colorectal neoplasia were enrolled. Participants underwent CT colonography followed by colonoscopy if CT colonography findings showed any polyps. Acceptability was measured with a 100-point (0, most favorable; 100, least favorable) visual analogue scale (VAS). Chi2 statistic was used to compare participation rates among subgroups. Safety of CT colonography was evaluated by recording all important adverse events. RESULTS: A total of 1,452 subjects were eligible for screening. The adjusted participation rate was 28.4%. Participation was higher in younger subjects and in those from a high socioeconomic region. Major reasons for nonparticipation were insufficient time and perceived good health. Median VAS scores for pain, general satisfaction, embarrassment, and willingness to repeat screening were 13, 6, 8, and 5, respectively. Most subjects found CT colonography better than (60%) or same as (32%) expected. Ninety-three (27.4%) of 340 subjects were referred for colonoscopy, with polyps found in 67 (positive predictive value, 0.73). By adopting criteria that a positive finding at CT colonography is that of a single polyp larger than 5 mm or multiple polyps larger than 2 mm, 14% of CT examinations would have led to colonoscopy; 5.7% of CT findings were false-positive, with no significant impairment in large polyp detection. There were no important adverse events related to CT colonography, although four subjects had syncope or presyncope related to bowel preparation. CONCLUSION: Community-based colorectal neoplasia screening with CT colonography was accompanied by a participation rate that compares favorably with that of similar screening programs. CT colonography was highly acceptable to participants.

Community-based screening by colonoscopy or computed tomographic colonography in asymptomatic average-risk subjects.

OBJECTIVES: Visualizing the entire colorectum in screening is an advantage of colonoscopy, and also computed tomographic (CT) colonography, another potentially suitable screening test. Our objective was to compare screening CT colonography and colonoscopy in an asymptomatic average-risk population, and to determine whether providing a choice of tests increased participation. METHODS: One thousand and four hundred subjects from the general community, randomly selected from the parliamentary electoral roll, were allocated one of three screening groups: colonoscopy, CT colonography, or a choice of these tests, and were sent an institutional letter of invitation. Those with symptoms, colorectal cancer in first-degree relatives, or colonoscopy within 5 yr were ineligible. Outcome measures were participation, acceptability of screening, and yield for advanced colorectal neoplasia in participants. RESULTS: Of the subjects, 24.9% were ineligible; the overall participation rate was 18.2% (184/1,009). Participation in each screening group was not different. Both tests were accompanied by the same high levels of acceptability; most participants found colonoscopy (87%) and CT colonography (67%, p < 0.001) less unpleasant than expected. About 29% (26/89) CT colonography subjects had a positive screening test. The yield of advanced colorectal neoplasia was 8.7% (95% CI 5-14%), with no difference in yield between tests. CONCLUSION: Colorectal neoplasia screening by colonoscopy or CT colonography was associated with modest participation, high levels of acceptability, and similar yield for advanced colorectal neoplasia. Providing a choice of test did not increase participation.

Renal colic: a prospective evaluation of non-enhanced spiral CT versus intravenous pyelography.

The aim of this study was to compare non-enhanced spiral CT (NECT) and intravenous pyelography (IVP) in patients with suspected acute renal colic. Two-hundred patients presenting to the Emergency Department with suspected acute renal colic were randomized into groups undergoing NECT or IVP. The main outcome measures were diagnostic utility, incidence of alternative diagnoses, requirement for further imaging, length of hospital stay, urological intervention rates, radiation dosage and costs. Non-enhanced spiral CT was better than IVP in making a definitive diagnosis of ureteric calculus or of recent calculus passage (65/102 or 66% vs 42/98 or 41%; P = 0.003). Calculi were missed in two patients in the IVP group. Two patients in each group had alternative diagnoses by initial imaging. There was no difference in the length of hospital stay or intervention rate. More plain X-rays during admission and more IVPs during follow up were performed in the NECT group. Effective radiation dosages were 2.97 mSv (IVP) and up to 5 mSv (NECT). Non-enhanced spiral CT provided greater diagnostic utility in this randomized comparison but no difference in measured outcomes. The incidence of alternative diagnoses was low, probably due to patient selection. Financial costs for each modality are comparable in a public tertiary hospital. Radiation dosages are higher for NECT and, for this reason, it might be appropriate to consider limiting NECT use to patients who have do not have classical symptoms of renal colic, to older patients and those with a contraindication to the administration of intravenous contrast media.