Streptococcus milleri in intraabdominal abscesses in children after appendectomy: incidence and course

Intraabdominal abscesses are a common complication after appendectomy, especially in children. In this study, we describe the incidence and course of this complication in relation to the cultured pathogens found in intraabdominal abscesses. The charts of all patients between 1 and 18 years of age undergoing appendectomy in 3 hospitals between January 2006, and July 2009, were retrospectively reviewed. Presence of an intraabdominal abscess was confirmed with abdominal ultrasound examination. We collected all details concerning the appendectomy, pus cultures, and postoperative course in these patients. Two hundred fifty-nine patients underwent appendectomy during the study period. Subsequently, abdominal ultrasound studies showed an intraabdominal abscess in 18 (7%) patients. Intraabdominal abscesses developed more frequently after perforated appendicitis (23%) than after simple appendicitis (2%). The incidence of postoperative abscesses did not differ significantly between open (5.6%) or laparoscopic (6.3%) appendectomy. However, the rate was high (38%) in the patients in whom the appendectomy was converted from laparoscopic to open. In 15 out of the 18 patients with a postoperative abscess drainage was performed. In pus cultures of the drained abscesses Streptococcus milleri and Escherichia coli were the most commonly isolated pathogens. Presence of S milleri was associated with prolonged hospital stay (13.9 versus 9.0 days, P = .105) and prolonged antibiotic treatment (11.3 versus 4.8 days, P = .203). The incidence of intraabdominal abscesses is high after perforated appendicitis in children (23%). Our data suggest that the presence of S milleri correlates with a more complicated postoperative course after appendectomy in childre

A Systematic Review and Meta-Analysis of Diagnostic Performance of Imaging in Acute Cholecystitis

Purpose: To update previously summarized estimates of diagnostic accuracy for acute cholecystitis and to obtain summary estimates for more recently introduced modalities. Materials and Methods: A systematic search was performed in MEDLINE, EMBASE, Cochrane Library, and CINAHL databases up to March 2011 to identify studies about evaluation of imaging modalities in patients who were suspected of having acute cholecystitis. Inclusion criteria were explicit criteria for a positive test result, surgery and/or follow-up as the reference standard, and sufficient data to construct a 2 3 2 table. Studies about evaluation of predominantly acalculous cholecystitis in intensive care unit patients were excluded. Bivariate random-effects modeling was used to obtain summary estimates of sensitivity and specificity. Results: Fifty-seven studies were included, with evaluation of 5859 patients. Sensitivity of cholescintigraphy (96%; 95% confidence interval [CI]: 94%, 97%) was significantly higher than sensitivity of ultrasonography (US) (81%; 95% CI: 75%, 87%) and magnetic resonance (MR) imaging (85%; 95% CI: 66%, 95%). There were no significant differences in specificity among cholescintigraphy (90%; 95% CI: 86%, 93%), US (83%; 95% CI: 74%, 89%) and MR imaging (81%; 95% CI: 69%, 90%). Only one study about evaluation of computed tomography (CT) met the inclusion criteria; the reported sensitivity was 94% (95% CI: 73%, 99%) at a specificity of 59% (95% CI: 42%, 74%). Conclusion: Cholescintigraphy has the highest diagnostic accuracy of all imaging modalities in detection of acute cholecystitis. The diagnostic accuracy of US has a substantial margin of error, comparable to that of MR imaging, while CT is still underevaluated. (C) RSNA, 201

Minder onterechte appendectomie door echografie en CT

To evaluate the effect of the use of ultrasonography (US) and optional computed tomography (CT) or diagnostic laparoscopy on the percentage of unnecessary appendectomies in patients with suspected acute appendicitis. Prospective and comparison with a historical control group. Following the introduction of ultrasound imaging as an initial step, the outcomes in all patients presenting with suspected appendicitis in the emergency department were prospectively collected during a period of 18 months (July 2006-December 2007). Results were compared to retrospectively collected data on all patients who had undergone appendectomy for acute appendicitis in 2001, before the introduction of this imaging investigation. Of the 312 consecutive patients in the emergency department with suspected acute appendicitis, the condition was excluded in 51 patients following clinical and laboratory investigation. The diagnostic algorithm was applied in 239 of the 261 patients (92%). All of them had initial US, followed by additional CT in 75 patients (31%) and diagnostic laparoscopy in 12 patients (5%). Appendectomy was performed in 130 patients, and 8 (6%) of the appendices were shown to be healthy following pathological investigation. Before the implementation of preoperative imaging 36 of the 170 appendices (21%) were healthy. Following the introduction of imaging techniques in accordance with the guideline there was a significant reduction in the percentage of unnecessary appendectomies (21% versus 6%; p <0,001). The complete supplementary diagnostic algorithm had a positive and negative predictive value of respectively 90% and 98% for acute appendicitis. Structural implementation of US with optional CT and diagnostic laparoscopy in patients with suspected acute appendicitis resulted in a lower percentage of unnecessary appendectomie

Acute Appendicitis on Abdominal MR Images: Training Readers to Improve Diagnostic Accuracy

Purpose: 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. Materials and Methods: 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. Results: 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. Conclusion: 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. (c) RSNA, 201

Acute appendicitis on abdominal MR images: training readers to improve diagnostic accuracy

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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

Comparison of imaging strategies with conditional contrast-enhanced CT and unenhanced MR imaging in patients suspected of having appendicitis: a multicenter diagnostic performance study

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. 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. 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. 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 detectio

Diagnostic accuracy and patient acceptance of MRI in children with suspected appendicitis

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 settin

MRI features associated with acute appendicitis

To identify MRI features associated with appendicitis. 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. 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. An appendix diameter >7 mm, peri-appendiceal fat infiltration and restricted diffusion of the appendiceal wall have the strongest association with appendicitis on MRI. • 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 %

Accuracy and interobserver agreement between MR-non-expert radiologists and MR-experts in reading MRI for suspected appendicitis

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. 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. 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). 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 highe

A simple clinical decision rule to rule out appendicitis in patients with nondiagnostic ultrasound results

The objective was to identify a set of clinical features that can rule out appendicitis in patients with suspected acute appendicitis and nondiagnostic ultrasound (US) results, allowing safe discharge and next-day reevaluation without initial computed tomography (CT) or magnetic resonance imaging (MRI). Data on clinical and US evaluation, including a number of prespecified variables potentially associated with acute appendicitis, were prospectively collected in two diagnostic accuracy studies of imaging. These studies included patients with suspected appendicitis seen in the emergency department (ED). For development and validation of the clinical decision rule (CDR), only patients with inconclusive or negative US results were included. There were 199 (of 422) patients in the development cohorts and 120 (of 211) patients in the validation cohort. Logistic regression analysis was used for data from patients with inconclusive or negative US results, and profiles were created of all possible combinations of predictors retained in the multivariable model. A final diagnosis was assigned by an expert panel based on perioperative data, histopathology, and clinical follow-up of at least 3 months. The CDR selected patients after negative or inconclusive US for discharge and next-day reevaluation without initial CT or MRI if fewer than two of the following predictors were present: male sex, migration of pain to the right lower quadrant, vomiting, and white blood cell (WBC) count higher than 12.0 × 10(9) /L. Applying the CDR in the development set selected 126 of 199 (63%) patients with negative or inconclusive US results for discharge without further imaging. This rule reduced the probability of appendicitis from 26% (51 of 199) in the total group of patients with negative or inconclusive US results to 12% (15 of 126) in the group that would be discharged based on the rule (p = 0.001). In the validation set (n = 120), the decision rule selected 72 (60%) patients for discharge and next-day reevaluation and reduced the probability of appendicitis from 20% (24 of 120) in the total group to 6% (4 of 72) in the patients selected on the rule (p = 0.001). The negative predictive value of the decision rule in the validation set was 94% (95% confidence interval [CI] = 87% to 98%). In comparison, the negative predictive value of CT in the same group was 99% (95% CI = 93% to 100%, p = 0.14), and that of MRI was 99% (95% CI = 94% to 100%, p = 0.12). Alternative decision rules based on combinations of the present decision rule with C-reactive protein (CRP) results did not improve selection. This newly developed CDR significantly reduces the probability of appendicitis in a large subgroup of patients with negative or inconclusive US results. These patients can be safely discharged for outpatient reevaluation without further initial imaging if proper follow-up is available. This could assist in lowering the number of ED imaging investigations in patients with suspected appendiciti