[CT strategy for patients with suspected acute appendicitis; comparison of conditional and immediate CT]. / CT-strategie bij vermoeden van acute appendicitis; vergelijking van conditionele en directe CT.

OBJECTIVE: To compare the diagnostic accuracy of conditional CT strategy, i.e. CT if ultrasound findings are negative or inconclusive, with immediate CT strategy for patients with suspected appendicitis. DESIGN: Subanalysis of a prospective multicenter diagnostic accuracy study. METHOD: Only data of patients with signs of appendicitis based on medical history, physical examination, and laboratory tests were analyzed. All patients underwent both ultrasound and CT. Images of each were read by different observers who were blinded to the results of the other imaging modality. The observer then selected the most likely diagnosis. These diagnoses were compared with the reference standard, i.e. final diagnoses as assigned by an expert panel based on all available data and at least 6 months of follow-up. RESULTS: A total of 422 patients with suspected appendicitis were included. In 251 patients the final diagnosis was acute appendicitis (59%). In 199 patients (47%), ultrasound findings were inconclusive or negative. Use of conditional CT strategy resulted in correctly identified number of correctly identified patients with appendicitis, i.e. 96% (95% CI 93-98), versus 95% identified by immediate CT (95% CI 91-97). However, conditional CT strategy resulted in more false positive diagnoses compared with immediate CT (39 versus 22), had an accompanying lower specificity of 77% (95% CI 70-83) versus 87% (95% CI 81-91), and a lower positive predictive value of 86% (95% CI 81-90) versus 92% (95% CI 87-95). CONCLUSION: Use of a conditional CT strategy results in exactly the same number of patients with correctly identified acute appendicitis while halving the number of CTs needed. However, conditional strategy results in more false positive diagnoses.

A comparison of the accuracy of ultrasound and computed tomography in common diagnoses causing acute abdominal pain.

OBJECTIVES: Head-to-head comparison of ultrasound and CT accuracy in common diagnoses causing acute abdominal pain. MATERIALS AND METHODS: Consecutive patients with abdominal pain for >2 h and <5 days referred for imaging underwent both US and CT by different radiologists/radiological residents. An expert panel assigned a final diagnosis. Ultrasound and CT sensitivity and predictive values were calculated for frequent final diagnoses. Effect of patient characteristics and observer experience on ultrasound sensitivity was studied. RESULTS: Frequent final diagnoses in the 1,021 patients (mean age 47; 55% female) were appendicitis (284; 28%), diverticulitis (118; 12%) and cholecystitis (52; 5%). The sensitivity of CT in detecting appendicitis and diverticulitis was significantly higher than that of ultrasound: 94% versus 76% (p < 0.01) and 81% versus 61% (p = 0.048), respectively. For cholecystitis, the sensitivity of both was 73% (p = 1.00). Positive predictive values did not differ significantly between ultrasound and CT for these conditions. Ultrasound sensitivity in detecting appendicitis and diverticulitis was not significantly negatively affected by patient characteristics or reader experience. CONCLUSION: CT misses fewer cases than ultrasound, but both ultrasound and CT can reliably detect common diagnoses causing acute abdominal pain. Ultrasound sensitivity was largely not influenced by patient characteristics and reader experience.

Imaging strategies for detection of urgent conditions in patients with acute abdominal pain: diagnostic accuracy study.

OBJECTIVE: To identify an optimal imaging strategy for the accurate detection of urgent conditions in patients with acute abdominal pain. DESIGN: Fully paired multicentre diagnostic accuracy study with prospective data collection. SETTING: Emergency departments of two university hospitals and four large teaching hospitals in the Netherlands. PARTICIPANTS: 1021 patients with non-traumatic abdominal pain of >2 hours' and <5 days' duration. Exclusion criteria were discharge from the emergency department with no imaging considered warranted by the treating physician, pregnancy, and haemorrhagic shock. INTERVENTION: All patients had plain radiographs (upright chest and supine abdominal), ultrasonography, and computed tomography (CT) after clinical and laboratory examination. A panel of experienced physicians assigned a final diagnosis after six months and classified the condition as urgent or non-urgent. MAIN OUTCOME MEASURES: Sensitivity and specificity for urgent conditions, percentage of missed cases and false positives, and exposure to radiation for single imaging strategies, conditional imaging strategies (CT after initial ultrasonography), and strategies driven by body mass index and age or by location of pain. RESULTS: 661 (65%) patients had a final diagnosis classified as urgent. The initial clinical diagnosis resulted in many false positive urgent diagnoses, which were significantly reduced after ultrasonography or CT. CT detected more urgent diagnoses than did ultrasonography: sensitivity was 89% (95% confidence interval 87% to 92%) for CT and 70% (67% to 74%) for ultrasonography (P<0.001). A conditional strategy with CT only after negative or inconclusive ultrasonography yielded the highest sensitivity, missing only 6% of urgent cases. With this strategy, only 49% (46% to 52%) of patients would have CT. Alternative strategies guided by body mass index, age, or location of the pain would all result in a loss of sensitivity. CONCLUSION: Although CT is the most sensitive imaging investigation for detecting urgent conditions in patients with abdominal pain, using ultrasonography first and CT only in those with negative or inconclusive ultrasonography results in the best sensitivity and lowers exposure to radiation.