Alan N. Desmond

Crohn's disease: factors associated with exposure to high levels of diagnostic radiation

Aims: Exposure to diagnostic radiation may be associated with increased risk of malignancy. The aims of this study were: (a) to examine patterns of use of imaging in Crohn9s disease; (b) to quantify the cumulative effective dose (CED) of diagnostic radiation received by patients; and (c) to identify patients at greatest risk of exposure to high levels of diagnostic radiation. Methods: 409 patients with Crohn9s disease were identified at a tertiary centre. CED was calculated retrospectively from imaging performed between July 1992 and June 2007. High exposure was defined as CED>75 milli-Sieverts (mSv), an exposure level which has been reported to increase cancer mortality by 7.3%. Complete data were available for 399 patients. 45 were excluded (20 attended outside study period, 25 primarily managed at other centres). Results: Use of computed tomography increased significantly and accounted for 77.2% of diagnostic radiation. Mean CED was 36.1mSv and exceeded 75mSv in 15.5% of patients. Factors associated with high cumulative exposure were: age 1) surgeries (OR 2.7, CI 1.4-5.4). Conclusions: Identifiable subsets of patients with Crohn9s disease are at risk of exposure to significant amounts of diagnostic radiation. Given the background risk of neoplasia and exposure to potentially synergistic agents such as purine analogues and other immune-modulators, specialist centres should develop low-radiation imaging protocols.

Diagnostic Accuracy of Computed Tomography Using Lower Doses of Radiation for Patients With Crohn's Disease

BACKGROUND & AIMS Magnetic resonance and ultrasonography have increasing roles in the initial diagnosis of Crohns disease, but computed tomography (CT) with positive oral contrast agents is most frequently used to identify those with acute extramural complications. However, CT involves exposure of patients to radiation. We prospectively compared the diagnostic accuracy of low-dose CT (at a dose comparable to that used to obtain an abdominal radiograph) with conventional-dose CT in patients with active Crohns disease. METHODS Low and conventional dose CT of the abdomen and pelvis were acquired from 50 patients with Crohns disease, referred from an inflammatory bowel disease service (20 male; median age, 34 years). Acute complications of Crohns disease were suspected. Iterative reconstruction was performed on all CT datasets to facilitate dose reduction. Three radiologists reviewed the low-dose CT images before the conventional-dose CT images. RESULTS The median effective dose (interquartile range) of radiation for the low-dose CT was reduced by 72% from that of conventional CT: from 3.5 mSv (3-5.08 mSv) to 0.98 mSv (0.77-1.42 mSv) (P < .001). As expected, the quality indexes of the low-dose images were inferior to those of the conventional-dose images, but no clinically significant diagnostic findings were missed with low-dose imaging. Follow-up CT examinations were recommended for 5 patients; 1 had a cervical tumor, 1 had a pancreatic lesion, and 3 had intra-abdominal abscess. In each case, the image obtained by low-dose CT was considered sufficient for diagnosis. CONCLUSIONS Although low-dose CT images are of lower quality than images obtained with conventional doses of radiation, no clinically significant diagnostic findings were missed from low-dose CT images of patients with Crohns disease. The low-dose CT was obtained at a median effective dose equivalent to 1.4 abdominal radiographs.

Radiation Exposure From Diagnostic Imaging Among Patients With Gastrointestinal Disorders

BACKGROUND & AIMS There are concerns about levels of radiation exposure among patients who undergo diagnostic imaging for inflammatory bowel disease (IBD), compared with other gastrointestinal (GI) disorders. We quantified imaging studies and estimated the cumulative effective dose (CED) of radiation received by patients with organic and functional GI disorders. We also identified factors and diagnoses associated with high CEDs. METHODS We analyzed data from 2590 patients who were diagnosed with GI disorders at a tertiary gastroenterology center from January 1999-January 2009 on the basis of International Statistical Classification of Diseases and Health-related Problems, 10th revision and Rome III criteria. High annual CED and high total CED were defined as figures exceeding the 90th percentile for the population. RESULTS Diagnostic imaging was performed on 57% of the patients (1429 of 2509). High annual CEDs (>9.6 millisieverts/annum) were independently associated with Crohns disease (odds ratio [OR], 5.3; P < .0001), organic small bowel disease (OR, 2.6; P < .005), and functional disorders of childhood and adolescence (OR, 9.8; P < .005). High total CEDs (>30.8 millisieverts) were independently associated with Crohns disease (OR, 81.9; P < .0001), ulcerative colitis (OR, 19.0; P < .0001), indeterminate colitis (OR, 7.5; P < .0005), and the following non-IBD diagnoses: organic small bowel disorders (OR, 12.5; P < .0001), organic hepatic disorders (OR, 3.6; P < .01), and functional disorders of childhood and adolescence (OR, 13.8; P = .02). CONCLUSIONS Higher levels of annual and total diagnostic radiation exposure are associated with IBD and with other organic and functional GI disorders. Evidence-based guidelines for image analysis of patients with organic and functional gastrointestinal disorders, especially those that reduce radiation exposure, are needed.

Selection of Symptomatic Patients With Crohn's Disease for Abdominopelvic Computed Tomography: Role of Serum C-Reactive Protein

Background Results of previous studies have shown that repeated abdominopelvic computed tomography (CT) examinations can lead to substantial cumulative diagnostic radiation exposure in patients with Crohns disease (CD). Improved selection of patients referred for CT will reduce unnecessary radiation exposure. This study examines if serum C-reactive protein (CRP) concentration predicts which symptomatic patients with CD are likely to have significant disease activity or disease complications (such as abscess) detected on abdominopelvic CT. Methods All abdominopelvic CTs performed on patients with CD at a tertiary referral centre during the period June 2003 to June 2008 were identified. CT findings were coded by a pair of independent blinded senior radiologists for (i) small bowel luminal disease, (ii) large bowel luminal disease, (iii) mesenteric inflammatory changes, (iv) penetrating disease (fistulas, abscess, or phlegmon), (v) acute disease complications (obstruction or perforation), and (vi) acute non-CD findings. Imaging findings were correlated with serum CRP checked within 14 days before imaging. The reference range for CRP was defined as 0–5 mg/L. Results A total of 147 patients with symptomatic CD had a CRP assay performed within 14 days before undergoing abdominopelvic CT. The median time from CRP assay to imaging was 2 days (interquartile range, 0-6 days). Median CRP before imaging was 24 mg/L (interquartile range, 6-88 mg/L). CT was normal in 34 of 147 case (23.1%). Patients with normal CRP (n = 36) were significantly less likely to have penetrating disease (odds ratio [OR], 0.04 [95% confidence interval {CI}, 0.01-0.7]; P < .001) or large bowel luminal disease (OR, 0.3 [95% CI, 0.1-0.8]; P < .05). Normal CRP excluded penetrating disease with a sensitivity of 1.0 (95% CI, 0.87-1.0). CRP levels did not correlate with the presence of small bowel luminal disease (n = 82), mesenteric inflammatory changes (n = 68), or acute disease complications (n = 10). Conclusion Symptomatic patients with CD and normal serum CRP are unlikely to have evidence of abscess, fistulating disease, or large bowel luminal disease detected on abdominopelvic CT. However, abdominopelvic CT may demonstrate evidence of clinically significant non-penetrating CD or complications, including perforation and acute obstruction, regardless of serum CRP concentration.

Plain abdominal radiographs in patients with Crohn's disease: radiological findings and diagnostic value.

AIM To determine the diagnostic yield and clinical value of plain film of the abdomen (PFA) in Crohns disease (CD) patients and to determine whether performance of PFA yields definitive diagnostic information or whether additional imaging examinations are required. MATERIALS AND METHODS One hundred and seventy-seven CD patients underwent 643 PFAs during the period September 1992 to August 2008. Two radiologists blinded to the clinical details independently evaluated individual PFAs and/or their reports for abnormal findings using the following criteria: normal, small bowel (SB) findings; colonic findings, acute CD complications, extra-colonic findings; global assessment/impression. The results of additional imaging studies performed within 5 days of PFA were recorded and findings were analysed. RESULTS A mean of 3.6 (range 1-22) PFAs was performed per patient during the study period. Almost 70% of films were normal (n = 449). SB abnormalities were detected in 21.8% (n = 140) PFAs; most commonly dilated loops (18.8%, n = 121) and mucosal oedema (5%, n = 32). Colonic abnormalities were present in 11.4% (n = 73); most commonly mucosal oedema (7.5%, n = 48) and dilated loops (5%, n = 32). Four cases of pneumoperitoneum were detected. There was no case of toxic megacolon. There was one case in which intra-abdominal abscess/collection was suspected and two cases of obstruction/ileus. Extracolonic findings (renal calculi, sacro-iliitis, etc.) were identified in 7.5% (n = 48). PFAs were followed by additional abdominal imaging within 5 days of PFA in 273/643 (42.5%) of cases. CONCLUSION Despite the high rates of utilization of PFA in CD patients, there is a low incidence of abnormal findings (32.5%). Many of the findings are non-specific and clinically irrelevant and PFA is frequently followed by additional abdominal imaging examinations.

Computed tomography assessment of intestinal gas volumes in functional gastrointestinal disorders.

Background/Aims Many patients with functional gastrointestinal disorders (FGIDs) rank sensations of bloating and distension among their most debilitating symptoms. Previous studies that have examined intestinal gas volume (IGV) in patients with FGIDs have employed a variety of invasive and imaging techniques. These studies are limited by small numbers and have shown conflicting results. The aim of our study was to estimate, using CT of the abdomen and pelvis (CTAP), IGV in patients attending FGID clinic and to compare IGV in patients with and without FGID. Methods All CTAP (n = 312) performed on patients (n = 207) attending a specialized FGID clinic over 10-year period were included in this study. Patients were classified into one of 3 groups according to the established clinical grading system, as organic gastrointestinal disorder (OGID, ie, patients with an organic non-functional disorder, n = 84), FGID (n = 36) or organic and functional gastrointestinal disorder (OFGID, ie, patients with an organic and a functional disorder, n = 87). Two independent readers blinded to the diagnostic group calculated IGV using threshold based 3D region growing with OsiriX. Results Median IGVs for the FGID, OGID, and OFGID groups were 197.6, 220.6 and 155.0 mL, respectively. Stepwise linear regression revealed age at study, gender, and calculated body mass index to predict the log IGV with an r2 of 0.116, and P < 0.001. There was a significant positive correlation between age and IGV in OGID (Spearmans = 0.253, P = 0.02) but this correlation was non-significant in the other groups. Conclusions Although bloating is a classic symptom in FGID patients, IGV may not be increased compared with OGID and OFGID patients.