Hassan A. Siddiki

Prospective Comparison of State-of-the-Art MR Enterography and CT Enterography in Small-Bowel Crohn's Disease

OBJECTIVE The objective of our study was to prospectively obtain pilot data on the accuracy of MR enterography for detecting small-bowel Crohns disease compared with CT enterography and with a clinical reference standard based on imaging, clinical information, and ileocolonoscopy. SUBJECTS AND METHODS The study group for this blinded prospective study was composed of 33 patients with suspected active Crohns ileal inflammation who were scheduled for clinical CT enterography and ileocolonoscopy and had consented to also undergo MR enterography. The MR enterography and CT enterography examinations were each interpreted by two radiologists with disagreements resolved by consensus. The reports from ileocolonoscopy with or without mucosal biopsy were interpreted by a gastroenterologist. The reference standard for the presence of small-bowel Crohns disease was based on the final clinical diagnosis by the referring gastroenterologist after reviewing all of the available information. RESULTS All 33 patients underwent CT enterography and ileocolonoscopy, 30 of whom also underwent MR enterography. The sensitivities of MR enterography and CT enterography for detecting active small-bowel Crohns disease were similar (90.5% vs 95.2%, respectively; p = 0.32). The image quality scores for MR enterography examinations were significantly lower than those for CT enterography (p = 0.005). MR enterography and CT enterography identified eight cases (24%) with a final diagnosis of active small-bowel inflammation in which the ileal mucosa appeared normal at ileocolonoscopy. Furthermore, enterography provided the only available imaging in three additional patients who did not have ileal intubation. CONCLUSION MR enterography and CT enterography have similar sensitivities for detecting active small-bowel inflammation, but image quality across the study cohort was better with CT. Cross-sectional enterography provides complementary information to ileocolonoscopy.

Incidental Findings in Imaging Research Evaluating Incidence, Benefit, and Burden

BACKGROUND Little information exists concerning the frequency and medical significance of incidental findings (IFs) in imaging research. METHODS Medical records of research participants undergoing a research imaging examination interpreted by a radiologist during January through March 2004 were reviewed, with 3-year clinical follow-up. An expert panel reviewed all IFs generating clinical action to determine medical benefit/burden on the basis of predefined criteria. The frequency of IFs that generated further clinical action was estimated by modality, body part, age, and sex, along with net medical benefit or burden. RESULTS Of 1426 research imaging examinations, 567 (39.8%) had at least 1 IF (1055 total). Risk of an IF increased significantly by age (odds ratio [OR], 1.5; 95% confidence interval, 1.4-1.7 per decade increase). Abdominopelvic computed tomography generated more IFs than other examinations (OR, 18.9 vs ultrasonography; 9.2% with subsequent clinical action), with computed tomography of the thorax and magnetic resonance imaging of the head next (OR, 11.9 and 5.9; 2.8% and 2.2% with action, respectively). Of the 567 examinations with an IF, 35 (6.2%) generated clinical action, resulting in clear medical benefit in 1.1% (6 of 567) and clear medical burden in 0.5% (3 of 567). Medical benefit/burden was usually unclear (26 of 567 [4.6%]). CONCLUSIONS Frequency of IFs in imaging research examinations varies significantly by imaging modality, body region, and age. Research imaging studies at high risk for generating IFs can be identified. Routine evaluation of research images by radiologists may result in identification of IFs in a high number of cases and subsequent clinical action to address them in a small but significant minority. Such clinical action can result in medical benefit to a small number of patients.

Appropriate Patient Selection at Abdominal Dual-Energy CT Using 80 kV: Relationship between Patient Size, Image Noise, and Image Quality

PURPOSE To determine the computed tomographic (CT) detector configuration, patient size, and image noise limitations that will result in acceptable image quality of 80-kV images obtained at abdominal dual-energy CT. MATERIALS AND METHODS The Institutional Review Board approved this HIPAA-compliant retrospective study from archival material from patients consenting to the use of medical records for research purposes. A retrospective review of contrast material-enhanced abdominal dual-energy CT scans in 116 consecutive patients was performed. Three gastrointestinal radiologists noted detector configuration and graded image quality and artifacts at specified levels-midliver, midpancreas, midkidneys, and terminal ileum-by using two five-point scales. In addition, an organ-specific enhancement-to-noise ratio and background noise were measured in each patient. Patient size was measured by using the longest linear dimension at the level of interest, weight, lean body weight, body mass index, and body surface area. Detector configuration, patient sizes, and image noise levels that resulted in unacceptable image quality and artifact rankings (score of 4 or higher) were determined by using multivariate logistic regression. RESULTS A 14 × 1.2-mm detector configuration resulted in fewer images with unacceptable quality than did the 64 × 0.6-mm configuration at all anatomic levels (P = .004, .01, and .02 for liver, pancreas, and kidneys, respectively). Image acceptability for the kidneys and ileum was significantly greater than that for the liver for all readers and detector configurations (P < .001). For the 14 × 1.2-mm detector configuration, patient longest linear dimensions yielding acceptable image quality across readers ranged from 34.9 to 35.8 cm at the four anatomic levels. CONCLUSION An 80-kV abdominal CT can be performed with appropriate diagnostic quality in a substantial percentage of the population, but it is not recommended beyond the described patient size for each anatomic level. The 14 × 1.2-mm detector configuration should be preferred.

Prospective Blinded Comparison of Wireless Capsule Endoscopy and Multiphase CT Enterography in Obscure Gastrointestinal Bleeding

PURPOSE To compare the performance of multiphase computed tomographic (CT) enterography with that of capsule endoscopy in a group of patients with obscure gastrointestinal bleeding (OGIB). MATERIALS AND METHODS This prospective HIPAA-compliant study was approved by the institutional review board and the institutional conflict of interest committee. All patients provided written informed consent. Two radiologists, blinded to clinical data and results of capsule endoscopy, interpreted images from CT enterography independently, with discordant interpretations resolved by consensus. Results were compared with those from a reference standard (surgery or endoscopy) and clinical follow-up. Sensitivity and 95% confidence intervals were calculated for each modality. RESULTS Fifty-eight adult patients, referred for the evaluation of OGIB (occult, 25 patients [43%]; overt, 33 patients [57%]), underwent both tests. A small bowel bleeding source was identified in 16 of the 58 patients (28%). The sensitivity of CT enterography was significantly greater than that of capsule endoscopy (88% [14 of 16 patients] vs 38% [six of 16 patients], respectively; P = .008), largely because it depicted more small bowel masses (100% [nine of nine patients] vs 33% [three of nine patients], respectively; P = .03). No additional small bowel tumors were discovered during the follow-up period (range, 5.6-45.9 months; mean, 16.6 months). CONCLUSION In this referral population, the sensitivity of CT enterography for detecting small bowel bleeding sources and small bowel masses was significantly greater than that of capsule endoscopy. On the basis of these findings, the addition of multiphase CT enterography to the routine diagnostic work-up of patients with OGIB should be considered, particularly in patients with negative findings at capsule endoscopy.

Prevalence of penetrating disease and extraintestinal manifestations of Crohn's disease detected with CT enterography

Background: This study was conducted to determine the prevalence of penetrating disease and extraintestinal manifestations of Crohns disease (CD) identified by computed tomography enterography (CTE). We also sought to examine the percentage of clinically significant new noninflammatory bowel disease (IBD) related findings in these patients. Methods: We analyzed the records of 357 consecutive patients with previously diagnosed CD evaluated at our institution who underwent a CTE between August 2004 and October 2005. Radiology reports were reviewed for the presence of penetrating disease (abscess, fistula, or phlegmon) or extraintestinal IBD manifestations (nephrolithiasis, cholelithiasis, sacroiliitis, avascular necrosis, deep vein thrombosis, or primary sclerosing cholangitis). Additional non‐IBD‐related abnormalities were also recorded, including any mass or cystic lesion. Urgent findings were defined as those that were deemed by the radiologist or ordering physician to require medical follow‐up within 3 months. Results: Of 357 patients identified (51% female) the median age was 41.6 years and median disease duration was 9.9 years. Of this cohort, 20.7% had penetrating disease (new finding in 58.1%) and 18.8% had extraintestinal IBD manifestations (new finding in 67.2%). Six patients had primary sclerosing cholangitis and portal/mesenteric vein thrombosis, respectively. In addition, 45.1% had non‐IBD findings including 2 unsuspected malignancies. Most of these extraenteric non‐IBD abnormalities were benign, with only 13.0% requiring urgent follow‐up. Conclusions: CT enterography is a valuable diagnostic modality for detecting both penetrating disease and extraintestinal IBD manifestations. These data add to a growing body of evidence that supports the use of CTE in CD diagnostic and management algorithms.

Benefit of computed tomography enterography in Crohn's disease: Effects on patient management and physician level of confidence

Background: Computed tomographic enterography (CTE) has been shown to have a high sensitivity and specificity for active small bowel inflammation. There are only sparse data on the effect of CTE results on Crohns disease (CD) patient care. Methods: We prospectively assessed 273 patients with established or suspected CD undergoing a clinically indicated CTE. Providers were asked to complete pre‐ and postimaging questionnaires regarding proposed clinical management plans and physician level of confidence (LOC) for the presence or absence of active small bowel disease, fistula(s), abscess(es), or stricturing disease. Correlative clinical, serologic, and histologic data were recorded. Following revelation of CTE results, providers were questioned if CTE altered their management plans, and whether LOC changes were due to CTE findings (on a 5‐point scale). Results: CTE altered management plans in 139 cases (51%). CTE changed management in 70 (48%) of those with established disease, prompting medication changes in 35 (24%). Management changes were made post‐CTE in 69 (54%) of those with suspected CD, predominantly due to excluding CD (36%). CTE‐perceived changes in management were independent of clinical, serologic, and histologic findings (P < 0.0001). Clinically meaningful LOC changes (2 or more points) were observed in 212 (78%). Conclusions: CTE is a clinically useful examination, altering management plans in nearly half of patients with CD, while increasing physician LOC for the detection of small bowel inflammation and penetrating disease. These findings further support the use of CTE in CD management algorithms. (Inflamm Bowel Dis 2011;)

Computed Tomography Enterography Detects Intestinal Wall Changes and Effects of Treatment in Patients With Crohn's Disease

BACKGROUND & AIMS The use of computed tomography enterography (CTE) in patients with Crohns disease has increased. However, there is little data available on how radiologic parameters of active disease change during treatment with infliximab and whether these changes correspond to symptoms, serum biomarkers, or endoscopic appearance. METHODS We performed a retrospective study of patients with Crohns disease who had undergone serial CTE imaging while receiving infliximab. Lesions were defined as improved if their enhancement or length decreased without worsening of other parameters. Patients were grouped as responders (all lesions improved), partial responders (some lesions improved), and nonresponders (worsening or no changes in all lesions). Of the 63 patients identified (47% female), the median age was 37.7 years, the median disease duration was 7.6 years, and the median time between initial and first follow-up CTE was 356 days (interquartile range, 215-630). RESULTS Of 105 lesions, 52 (49.5%) improved, 11 (10.5%) remained unchanged, and 42 (40.0%) worsened. Per patient, 28 (44.4%) were responders, 12 (19.0%) were partial responders, and 23 (36.5%) were nonresponders. The radiologic response had poor-to-fair agreement with symptoms, endoscopic appearance, and levels of C-reactive protein at time of second CTE (κ = 0.26, 0.07, and 0.30 respectively). CONCLUSIONS Radiologic improvement was observed in 63.4% of patients with Crohns disease who received infliximab therapy, despite a study design that was likely biased toward nonresponders. Radiologic response was not in good agreement with clinical symptoms, serum biomarkers, or endoscopic appearance; CTE might be used as a complementary approach to identify mural healing or inflammation not detected by other methods.

Validation of a lower radiation computed tomography enterography imaging protocol to detect Crohn's disease in the small bowel

Background: The purpose was to validate a lower radiation dose computed tomography enterography (CTE) imaging protocol to detect the presence of Crohns disease (CD) in the small bowel using two different reference standards and to identify a prediction model based on CTE signs for the presence of active CD. Methods: This retrospective study included patients with known or suspected CD who underwent CTE between January and October 2006 according to a lower radiation dose protocol. Two gastrointestinal radiologists blindly and independently classified each CTE as being active or inactive. Reference standards included ileocolonoscopy ± biopsy and a comprehensive clinical reference standard (retrospectively created by a gastroenterologist, also including history, physical, follow‐up course, and subsequent endoscopy, imaging, or surgery). Logistic regression was used to identify CTE findings that predicted the presence of active CD based on the combined clinical reference standard. Results: In all, 137 patients underwent CTE and ileocolonoscopy. Using an endoscopic reference standard, the sensitivity of CTE to detect active CD for the two readers was 81% and 89%, respectively. Using the clinical reference standard, the sensitivity of CTE to detect active CD was 89% and 98%, respectively. For both readers the sensitivity of CTE increased by 8%–9% when using the comprehensive reference standard. Multivariate analysis showed that a combination of mural thickness and hyperenhancement best predicted active CD (area under the curve [AUC] = 0.92–0.93, P < 0.0001). Conclusions: Lower radiation dose CTE exams are sensitive for the detection of active small bowel CD. The combination of mural thickness and hyperenhancement are the best radiologic predictors of active CD. (Inflamm Bowel Dis 2011;)

Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials

IntroductionDead-space fraction (Vd/Vt) has been shown to be a powerful predictor of mortality in acute lung injury (ALI) patients. The measurement of Vd/Vt is based on the analysis of expired CO2 which is not a part of standard practice thus limiting widespread clinical application of this method. The objective of this study was to determine prognostic value of Vd/Vt estimated from routinely collected pulmonary variables.MethodsSecondary analysis of the original data from two prospective studies of ALI patients. Estimated Vd/Vt was calculated using the rearranged alveolar gas equation: Vd/Vt=1−[(0.86×V˙CO2est)/(VE×PaCO2)] where V˙CO2est is the estimated CO2 production calculated from the Harris Benedict equation, minute ventilation (VE) is obtained from the ventilator rate and expired tidal volume and PaCO2 from arterial gas analysis. Logistic regression models were created to determine the prognostic value of estimated Vd/Vt.ResultsOne hundred and nine patients in Mayo Clinic validation cohort and 1896 patients in ARDS-net cohort demonstrated an increase in percent mortality for every 10% increase in Vd/Vt in a dose response fashion. After adjustment for non-pulmonary and pulmonary prognostic variables, both day 1 (adjusted odds ratio-OR = 1.07, 95%CI 1.03 to 1.13) and day 3 (OR = 1.12, 95% CI 1.06 to 1.18) estimated dead-space fraction predicted hospital mortality.ConclusionsElevated estimated Vd/Vt predicts mortality in ALI patients in a dose response manner. A modified alveolar gas equation may be of clinical value for a rapid bedside estimation of Vd/Vt, utilizing routinely collected clinical data.

Abdominal Findings in Hereditary Hemorrhagic Telangiectasia: Pictorial Essay on 2D and 3D Findings with Isotropic Multiphase CT

The rapid evolution in multidetector computed tomographic (CT) technology has produced improvements in temporal and spatial resolution, leading to greater recognition of the spectrum of abdominal findings in hereditary hemorrhagic telangiectasia (HHT). In this multisystem vascular disorder, the abdominal findings are predominantly within the liver. Hepatic vascular lesions in HHT range from tiny telangiectases to transient perfusion abnormalities and large confluent vascular masses. Focal hepatic lesions are often associated with arteriovenous, arterioportal, or portovenous shunts. Pancreatic, splenic, and other vascular abnormalities are also observed because they are included in the field of view. By taking advantage of the increased z-axis spatial resolution and faster scanning times, and by using a bolus tracking technique, multiphase CT can be used to identify hepatic and extrahepatic lesions in HHT and to characterize the associated vascular shunts. Coronal maximum intensity projection images are particularly helpful in depiction of small hepatic vascular lesions.