Bart M Wiarda

Medisch Centrum Alkmaar, Alkmaar, North Holland, Netherlands

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Publications (23)93.91 Total impact

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    ABSTRACT: Objective To compare accuracy and interobserver agreement between radiologists with limited experience in the evaluation of abdominal MRI (non-experts), and radiologists with longer MR reading experience (experts), in reading MRI in patients with suspected appendicitis. Methods MR imaging was performed in 223 adult patients with suspected appendicitis and read independently by two members of a team of eight MR-inexperienced radiologists, who were trained with 100 MR examinations previous to this study (non-expert reading). Expert reading was performed by two radiologists with a larger abdominal MR experience (>500 examinations) in consensus. A final diagnosis was assigned after three months based on all available information, except MRI findings. We estimated MRI sensitivity and specificity for appendicitis and for all urgent diagnoses separately. Interobserver agreement was evaluated using kappa statistics. Results Urgent diagnoses were assigned to 147 of 223 patients; 117 had appendicitis. Sensitivity for appendicitis was 0.89 by MR-non-expert radiologists and 0.97 in MR-expert reading (p = 0.01). Specificity was 0.83 for MR-non-experts versus 0.93 for MR-expert reading (p = 0.002). MR-experts and MR-non-experts agreed on appendicitis in 89% of cases (kappa 0.78). Accuracy in detecting urgent diagnoses was significantly lower in MR-non-experts compared to MR-expert reading: sensitivity 0.84 versus 0.95 (p < 0.001) and specificity 0.71 versus 0.82 (p = 0.03), respectively. Agreement on urgent diagnoses was 83% (kappa 0.63). Conclusion MR-non-experts have sufficient sensitivity in reading MRI in patients with suspected appendicitis, with good agreement with MR-expert reading, but accuracy of MR-expert reading was higher.
    European Journal of Radiology. 01/2014; 83(1):103–110.
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    ABSTRACT: Objectives To identify MRI features associated with appendicitis. Methods Features expected to be associated with appendicitis were recorded in consensus by two expert radiologists on 223 abdominal MRIs in patients with suspected appendicitis. Nine MRI features were studied: appendix diameter >7 mm, appendicolith, peri-appendiceal fat infiltration, peri-appendiceal fluid, absence of gas in the appendix, appendiceal wall destruction, restricted diffusion of the appendiceal wall, lumen or focal fluid collections. Appendicitis was assigned as the final diagnosis in 117/223 patients. Associations between imaging features and appendicitis were evaluated with logistic regression analysis. Results All investigated features were significantly associated with appendicitis in univariate analysis. Combinations of two and three features were associated with a probability of appendicitis of 88 % and 92 %, respectively. In patients without any of the nine features, appendicitis was present in 2 % of cases. After multivariate analysis, only an appendix diameter >7 mm, peri-appendiceal fat infiltration and restricted diffusion of the appendiceal wall were significantly associated with appendicitis. The probability of appendicitis was 96 % in their presence and 2 % in their absence. Conclusions An appendix diameter >7 mm, peri-appendiceal fat infiltration and restricted diffusion of the appendiceal wall have the strongest association with appendicitis on MRI. Key points • An enlarged appendix, fat infiltration and restricted diffusion are associated with appendicitis. • One such feature on MRI gives an 88 % probability of appendicitis. • Two features in combination give a probability of appendicitis of 94 %. • Combinations of three features give a probability of appendicitis of 96 %. • The absence of these features almost rules out appendicitis (2 %).
    European Radiology 01/2014; 24(1). · 3.55 Impact Factor
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    ABSTRACT: Diverticulitis is commonly diagnosed using ultrasound (US), followed by computed tomography (CT). Our aim was to determine the diagnostic accuracy of US compared with CT for patients with uncomplicated and complicated diverticulitis. We reviewed medical records of 232 patients admitted with diverticulitis via the emergency department between January 2009 and January 2011. Patients who had undergone US and a CT scan were identified and further analyzed. A total of 123 patients underwent an US and a CT scan. In 78/94 patients with uncomplicated diverticulitis, results of US and CT scan were compatible (83 %); in 6 of the remaining 29 patients both modalities showed a complicated diverticulitis (21 %). US misdiagnosed 17 % of patients with uncomplicated diverticulitis and 79 % with complicated diverticulitis. US is insufficient for diagnosing a complicated diverticulitis. Missing a complicated diverticulitis can have important clinical implications, and if diverticulitis is suspected, we suggest obtaining a CT scan to confirm diagnosis and to exclude complications.
    World Journal of Surgery 12/2013; · 2.23 Impact Factor
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    ABSTRACT: To compare magnetic resonance imaging (MRI) and ultrasound in children with suspected appendicitis. In a single-centre diagnostic accuracy study, children with suspected appendicitis were prospectively identified at the emergency department. All underwent abdominal ultrasound and MRI within 2 h, with the reader blinded to other imaging findings. An expert panel established the final diagnosis after 3 months. We evaluated the diagnostic accuracy of three imaging strategies: ultrasound only, conditional MRI after negative or inconclusive ultrasound, and MRI only. Significance between sensitivity and specificity was calculated using McNemar's test statistic. Between April and December 2009 we included 104 consecutive children (47 male, mean age 12). According to the expert panel, 58 patients had appendicitis. The sensitivity of MRI only and conditional MRI was 100 % (95 % confidence interval 92-100), that of ultrasound was significantly lower (76 %; 63-85, P < 0.001). Specificity was comparable among the three investigated strategies; ultrasound only 89 % (77-95), conditional MRI 80 % (67-89), MRI only 89 % (77-95) (P values 0.13, 0.13 and 1.00). In children with suspected appendicitis, strategies with MRI (MRI only, conditional MRI) had a higher sensitivity for appendicitis compared with a strategy with ultrasound only, while specificity was comparable. • In children, MRI has a higher sensitivity for appendicitis than ultrasound. • Ultrasound followed by MRI in negative or inconclusive findings is accurate. • The tolerance for ultrasound and MRI in children is comparable. • MRI can be performed in children in an emergency setting.
    European Radiology 10/2013; · 3.55 Impact Factor
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    ABSTRACT: The management of patients with IBD requires evaluation with objective tools, both at the time of diagnosis and throughout the course of the disease, to determine the location, extension, activity and severity of inflammatory lesions, as well as, the potential existence complications. Whereas endoscopy is a well-established and uniformly performed diagnostic examination, the implementation of radiologic technique for assessment of IBD is still heterogeneous; variations in technical aspects and the degrees of experience and preferences exist across countries in Europe. ECCO and ESGAR scientific societies jointly elaborated a consensus to establish standards for imaging in IBD using magnetic resonance imaging, computed tomography, ultrasonography, and including also other radiologic procedures such as conventional radiology or nuclear medicine examinations for different clinical situations that include general principles, upper GI tract, colon and rectum, perineum, liver and biliary tract, emergency situation, and the postoperative setting. The statements and general recommendations of this consensus are based on the highest level of evidence available, but significant gaps remain in certain areas such as the comparison of diagnostic accuracy between different techniques, the value for therapeutic monitoring, and the prognostic implications of particular findings.
    Journal of Crohn s and Colitis 04/2013; · 3.39 Impact Factor
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    ABSTRACT: The management of patients with IBD requires evaluation with objective tools, both at the time of diagnosis and throughout the course of the disease, to determine the location, extension, activity and severity of inflammatory lesions, as well as, the potential existence complications. Whereas endoscopy is a well-established and uniformly performed diagnostic examination, the implementation of radiologic technique for assessment of IBD is still heterogeneous; variations in technical aspects and the degrees of experience and preferences exist across countries in Europe. ECCO and ESGAR scientific societies jointly elaborated a consensus to establish standards for imaging in IBD using magnetic resonance imaging, computed tomography, ultrasonography, and including also other radiologic procedures such as conventional radiology or nuclear medicine examinations for different clinical situations that include general principles, upper GI tract, colon and rectum, perineum, liver and biliary tract, emergency situation, and the postoperative setting. The statements and general recommendations of this consensus are based on the highest level of evidence available, but significant gaps remain in certain areas such as the comparison of diagnostic accuracy between different techniques, the value for therapeutic monitoring, and the prognostic implications of particular findings.
    Journal of Crohn s and Colitis 04/2013; · 3.39 Impact Factor
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    ABSTRACT: Purpose:To compare the diagnostic performance of imaging strategies with magnetic resonance (MR) imaging and computed tomographic (CT) imaging in adult patients suspected of having appendicitis.Materials and Methods:Institutional review board approval was obtained prior to study initiation, and patients gave written informed consent. In a multicenter diagnostic performance study, adults suspected of having appendicitis were prospectively identified in the emergency department. Consenting patients underwent ultrasonography (US) and subsequent contrast-enhanced CT if US imaging yielded negative or inconclusive results. Additionally, all patients underwent unenhanced MR imaging, with the reader blinded to other findings. An expert panel assigned final diagnosis after 3 months. Diagnostic performance of three imaging strategies was evaluated: conditional CT after US, conditional MR imaging after US, and immediate MR imaging. Sensitivity and specificity were calculated by comparing findings with final diagnosis.Results:Between March and September 2010, 229 US, 115 CT, and 223 MR examinations were performed in 230 patients (median age, 35 years; 40% men). Appendicitis was the final diagnosis in 118 cases. Conditional and immediate MR imaging had sensitivity and specificity comparable to that of conditional CT, which resulted in 3% (three of 118; 95% confidence interval [CI]: 1%, 7%) missed appendicitis, and 8% (10 of 125; 95% CI: 4%, 14%) false-positives. Conditional MR missed appendicitis in 2% (two of 118; 95% CI: 0%, 6%) and generated 10% (13 of 129; 95% CI: 6%, 16%) false-positives. Immediate MR missed 3% (four of 117; 95% CI: 1%, 8%) appendicitis with 6% (seven of 120; 95% CI: 3%, 12%) false-positives. Conditional strategies resulted in more false-positives in women than in men (conditional CT, 17% vs 0%; P = .03; conditional MR, 19% vs 1%; P = .04), wherease immediate MR imaging did not.Conclusion:The accuracy of conditional or immediate MR imaging was similar to that of conditional CT in patients suspected of having appendicitis, which implied that strategies with MR imaging may replace conditional CT for appendicitis detection.© RSNA, 2013.
    Radiology 03/2013; · 6.34 Impact Factor
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    ABSTRACT: Objective:The aim of this study was to examine which factors influence guideline adherence and to determine the impact of non-adherence on survival.Materials and methods:Cohort of 606 patients (median age 65.3 years) newly diagnosed with head and neck cancer at Medical Centre Alkmaar between 1997 and 2009. Treatment was compared to guideline recommendations. Multivariable analyses were performed to determine factors associated with non-adherence and associated outcome.Results:Ninety-one percent of patients were treated in accordance with guidelines for head and neck cancer. Reasons for discordant treatment were comorbidity, lack of cooperation in patients aged < 70 years, and patients' refusal to undergo recommended treatment. Age (OR 1.40, 95% CI 1.04–1.87), comorbidity (OR 1.68, 95% CI 1.32–2.13) and advanced disease (OR 1.83, 95% CI 1.46–2.28) were independently associated with non-adherence. Five-year overall survival was 64% for accordant treatment and 16% for discordant treatment (p < 0.001). Higher age (HR 1.03, 95% CI 1.01–1.04), advanced stage (HR 1.36, 95% CI 1.21–1.53), recurrent disease (HR 3.29, 95% CI 1.97–5.52) and treatment discordant with guidelines (HR 3.22, 95% CI 2.15–4.85) were independently associated with cancer-specific mortality.Conclusion:Discordance with guidelines occurred in less than 10% of patients at our centre and was associated with age, tumour stage, comorbidity, and a significantly poorer cancer-specific survival.
    Journal of Geriatric Oncology 10/2012; 3(4):329–336. · 1.12 Impact Factor
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    ABSTRACT: Background and aim:  To prospectively determine patient burden and patient preference for magnetic resonance enteroclysis (MRE), capsule endoscopy (CE) and balloon-assisted enteroscopy (BAE) in patients with suspected or known Crohn's disease (CD) or occult gastrointestinal bleeding (OGIB). Subjects and Methods:  Consecutive consenting patients with CD or OGIB underwent MRE, CE and BAE. CE was only performed if MRE showed no high-grade small bowel stenosis. Patient preference and burden was evaluated by means of standardized questionnaires at 5 moments in time. Results:  From January 2007 until March 2009, 76 patients were included (M/F 31/45; mean age 46.9 y; range 20.0-78.4y): 38 patients with OGIB and 38 with suspected or known CD. Seventeen patients did not undergo CE because of high-grade stenosis. Ninety-five percent (344/363) of the questionnaires were suitable for evaluation. CE was significantly favored over MRE and BAE with respect to bowel preparation, swallowing of the capsule (compared to insertion of the tube/scope), burden of the entire examination, duration and accordance with the pre-study information. CE and MRE were significantly preferred over BAE for clarity of explanation of the examination, and MRE was significantly preferred over BAE for bowel preparation, painfulness and burden of the entire examination. BAE was significantly favored over MRE for insertion of the scope and procedure duration. Pre- and post-study the order of preference was CE, MRE and BAE. Conclusion:  CE was preferred to MRE and BAE, it also had the lowest burden. MRE was preferred over BAE for clarity of explanation of the examination, bowel preparation, painfulness and burden of the entire examination, and BAE over MRE for scope insertion and study duration. © 2012 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd.
    Journal of Gastroenterology and Hepatology 06/2012; · 3.33 Impact Factor
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    ABSTRACT: To determine if training with direct feedback helps to improve the diagnostic performance of inexperienced readers in the detection of appendicitis on magnetic resonance (MR) images. The institutional review board approved this retrospective study and waived the requirement for informed consent. Nine radiologists and eight residents without experience in evaluating MR images for acute abdominal conditions evaluated a training set of images from 100 MR imaging examinations of patients suspected of having appendicitis and received direct feedback after each evaluation. An expert panel made a diagnosis of appendicitis in 45 patients and an alternative diagnosis in 55 patients on the basis of histopathologic examination and follow-up. Readers recorded two diagnoses: the first after viewing images from conventional MR sequences (half-Fourier rapid acquisition with relaxation enhancement and true fast imaging with steady-state precession) and the second after viewing diffusion-weighted (DW) MR images. Reader sensitivity and specificity were calculated per set of 25 cases. The average reader sensitivity for detecting appendicitis improved significantly after training (0.82 vs 0.92, P = .003); the average specificity improved nonsignificantly (0.82 vs 0.88, P = .10). Sensitivity for radiologists increased from 0.81 in the first set of 25 cases to 0.91 in the last set, and specificity improved from 0.82 to 0.85. For residents, sensitivity increased from 0.82 to 0.94, and specificity increased from 0.82 to 0.91. Sensitivity improved from 0.80 to 0.87 (P < .001) in all readings combined when DW images were read in addition to conventional MR images. Diagnostic accuracy of inexperienced readers in the evaluation of abdominal MR images for acute appendicitis improved after training with direct feedback, and the addition of DW images improved reader sensitivity.
    Radiology 06/2012; 264(2):455-63. · 6.34 Impact Factor
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    ABSTRACT: New modalities are available for visualization of the small bowel in patients with possible obscure gastrointestinal bleeding (OGIB), but their performance requires further comparison. This study compared the diagnostic yield of magnetic resonance enteroclysis (MRE) and capsule endoscopy in patients with OGIB, using balloon-assisted enteroscopy (BAE) as the reference standard. Consecutive consenting patients who were referred for evaluation of OGIB were prospectively included. Patients underwent MRE followed by capsule endoscopy and BAE. Patients with high grade stenosis at MRE did not undergo capsule endoscopy. The reference standard was BAE findings in visualized small-bowel segments and expert panel consensus for segments not visualized during BAE.Results: Over a period of 26 months, 38 patients were included (20 female [53 %]; mean age 58 years, range 28 - 75 years). Four patients (11 %) did not undergo capsule endoscopy due to high grade small-bowel stenosis at MRE (n = 3; 8 %) or timing issues (n = 1; 3 %). Capsule endoscopy was non-diagnostic in one patient. The reference standard identified abnormal findings in 20 patients (53 %). MRE had sensitivity, specificity, and positive and negative likelihood ratios of 21 %, 100 %, infinity, and 0.79, respectively. The corresponding values for capsule endoscopy were 61 %, 85 %, 4.1, and 0.46. The reference standard and capsule endoscopy did not differ in percent positive findings (P = 0.34), but MRE differed significantly from the reference BAE (P < 0.001). Capsule endoscopy was superior to MRE for detecting abnormalities (P = 0.0015). Capsule endoscopy performed better than MRE in the detection of small-bowel abnormality in patients with OGIB. MRE may be considered as an alternative for the initial examination in patients with clinical suspicion of small-bowel stenosis.
    Endoscopy 04/2012; 44(7):668-73. · 5.74 Impact Factor
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    ABSTRACT: New modalities are available to visualize the small bowel in patients with Crohn's disease (CD). The aim of this study was to compare the diagnostic yield of magnetic resonance enteroclysis (MRE) and capsule endoscopy (CE) to balloon-assisted enteroscopy (BAE) in patients with suspected or established CD of the small bowel. Consecutive, consenting patients first underwent MRE followed by CE and BAE. Patients with high-grade stenosis at MRE did not undergo CE. Reference standard for small bowel CD activity was a combination of BAE and an expert panel consensus diagnosis. Analysis included 38 patients, 27 (71%) females, mean age 36 (20-74) years, with suspected (n = 20) or established (n = 18) small bowel CD: 16 (42%) were diagnosed with active CD, and 13 (34%) by MRE with suspected high-grade stenosis, who consequently did not undergo CE. The reference standard defined high-grade stenosis in 10 (26%) patients. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value of MRE and CE for small bowel CD activity were 73 and 57%, 90 and 89%, 88 and 67%, and 78 and 84%, respectively. CE was complicated by capsule retention in one patient. MRE has a higher sensitivity and PPV than CE in small bowel CD. The use of CE is considerably limited by the high prevalence of stenotic lesions in these patients.
    Abdominal Imaging 11/2011; 37(3):397-403. · 1.91 Impact Factor
  • Gastroenterology 01/2011; · 12.82 Impact Factor
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    ABSTRACT: PURPOSE: This study aimed to determine the reliability of magnetic resonance imaging (MRI) without luminal contrast medium versus MR enteroclysis for evaluating small bowel pathology, to compare MRI and MRE findings per observer, and to compare these findings with those of an expert reader in order to determine the influence of luminal contrast medium on morphological evaluations. CONCLUSION: The use of luminal contrast medium bowel improves reliability for measuring bowel wall thickness and for the diagnosis and grading of obstruction when evaluating the small bowel.
    Clinical imaging 01/2009; 33(4):267-73. · 0.73 Impact Factor
  • Gastroenterology 01/2009; 136(5). · 12.82 Impact Factor
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    ABSTRACT: OBJECTIVE: MR enteroclysis has become an important tool to visualize the complete small bowel wall and extramural structures. In many centers, this technique is rapidly becoming the first-line technique for small bowel visualization. MR enteroclysis yields a diagnosis of thickened jejunal loops in some patients. In this paper, we describe an MR enteroclysis protocol and review the literature on jejunum abnormalities with several sample cases. CONCLUSION: Jejunum abnormalities are not uncommon. These abnormalities can be self-limiting, but some patients suffer from infectious and other pathologic conditions of the small bowel necessitating intervention.
    European Journal of Radiology 08/2008; 67(1):125-32. · 2.51 Impact Factor
  • Radiology 06/2007; 243(2):598-602. · 6.34 Impact Factor
  • Radiology 01/2007; 242(1):305-306. · 6.34 Impact Factor
  • Radiology 01/2007; 243:598-602. · 6.34 Impact Factor

Publication Stats

94 Citations
185 Downloads
1k Views
93.91 Total Impact Points

Institutions

  • 2005–2014
    • Medisch Centrum Alkmaar
      • Department of Radiology
      Alkmaar, North Holland, Netherlands
  • 2012
    • St. Antonius Ziekenhuis
      Nieuwegen, Utrecht, Netherlands
    • University of Amsterdam
      • Faculty of Medicine AMC
      Amsterdam, North Holland, Netherlands
  • 2007
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • Department of Radiology
      Amsterdam, North Holland, Netherlands