Non-traumatic acute bowel disease: differential diagnosis with 64-row MDCT

Exploring the evidence-practice gap in the use of plain radiography for acute abdominal pain and intestinal obstruction: a systematic review and meta-analysis

AIM

Previous studies, some dating back several decades, have recommended that the use of plain abdominal radiography should be curbed, particularly with the growth of more accurate imaging modalities. However, evidence from referral data suggests that plain abdominal radiography continues to be a commonly requested examination. The aim of this review was to explore the gap between evidence and practice by re-examining the evidence using a robust methodology, investigating the diagnostic accuracy of plain abdominal radiography.

METHODS

Studies were identified from electronic databases and reference lists. Eligible studies provided data as to the sensitivity and specificity of plain abdominal radiography for either acute abdominal pain (Group A) or suspected intestinal obstruction (Group B). Version 2 of the Quality Assessment of Diagnostic Accuracy Studies was used to assess the quality of studies and hierarchical summary receiver operator characteristic curves and coupled forest plots were generated.

RESULTS

Four studies evaluated plain abdominal radiography for acute abdominal pain (Group A) and 10 for suspected intestinal obstruction (Group B). Two studies investigated both presentations and were included in both groups. Methodological quality of studies was moderately high, though incorporation bias was a common limitation. Sensitivity for Group A studies ranged from 30 to 46%, with specificity from 75 to 88%. For Group B, the range of sensitivity was 48 to 96% and specificity from 50 to 100%.

CONCLUSION

The results suggest that use of plain abdominal radiography could be substantially reduced, particularly for patients with undifferentiated acute abdominal pain. While some guidelines exist, there is sound argument for clinical decision rules for abdominal imaging to inform evidence-based clinical decision-making and radiology referrals.

Diagnostic efficacy of single-pass abdominal multidetector-row CT: prospective evaluation of a low dose protocol

OBJECTIVE

To evaluate the diagnostic efficacy of single-pass contrast-enhanced multidetector CT (CE-MDCT) performed with a low-radiation high-contrast (LR-HC) dose protocol in selected patients with non-traumatic acute bowel disease.

METHODS

65 (32 males, 33 females; aged 20-67 years) consecutive patients with non-traumatic acute bowel disease underwent single-pass CE-MDCT performed 70-100 s after i.v. bolus injection of a non-ionic iodinated contrast medium (CM) (370 mgI ml^-1). In 46 (70%) patients with a clinical and/or ultrasonographic suspicion of inflammatory bowel disease, up to 1.2-1.4 l of a 7% polyethylene-glycol solution was orally administered 45-60 mins prior to the CT examination. Patients were then divided into two groups according to age: Group A (20-44 years; n = 34) and Group B (45-70 years; n = 31). Noise index (NI) and CM dose were selected as follows: Group A (NI = 15; 2.5 ml kg^-1) and Group B (NI = 12.5; 2 ml kg^-1). All patients of Group A underwent thyroid functional tests at 4-6 weeks. Final diagnoses were obtained by open (n = 12) or laparoscopic surgery (n = 4), endoscopy w/without biopsy (n = 24) and clinical (n = 19) and/or instrumental (ultrasonography) (n = 6) follow-up at 11 ± 4 months (range 6-18 mo.). Statistical analysis was performed by χ² and Student's t-test for categorical and continuous variables, respectively.

RESULTS

Sensitivity and specificity were 91.3 vs 95.4% (p = 0.905) and 90.9 vs 88.8% (p = 0.998) with an overall diagnostic accuracy of 91.1 vs 93.5% (p = 0.756), whereas the radiation (in millisievert) and CM dose (in millilitre) were 7.5 ± 2.8 mSv and 155 ± 30 ml for Group A and 14.1 ± 5.3 mSv and 130 ± 24 ml for Group B (p < 0.001), respectively. No patients of Group A showed laboratory signs of thyrotoxicosis at follow-up.

CONCLUSION

The LR-HC has proved to be a safe and a dose-effective protocol in the evaluation of selected young patients with non-traumatic acute bowel disease. Advances in knowledge: (1) As reaching the highest diagnostic benefit to risk ratio (AHARA) appears to be the current principle of MDCT imaging, an increased amount of iodinated CM (0.7-0.9 gI ml^-1) can be safely administered to young patients (<40 years) with normal thyroid and renal function to compensate for the lower image quality resulting from low-dose CT protocols performed with the standard filter back-projection algorithm. Such an approach will result in a significant reduction of the radiation dose, which could be otherwise achieved only using iterative reconstruction algorithms combined with either low tube voltage and/or low tube current protocols. (2) An optimal scan delay (T_delay) for a venous phase caudocranial acquisition can be calculated by the following formula: T_delay = CI + 25 - T_SD, where CI is the duration of the contrast injection, 25 is the average of the sum of abdominal aortic and peak hepatic arrival times and T_SD is the scan duration. With such an approach, the radiation exposure resulting from bolus tracking, albeit performed with low-dose scans, can be spared in patients with normal transit times.

Diagnostic accuracy of low-dose CT compared with abdominal radiography in non-traumatic acute abdominal pain: prospective study and systematic review

OBJECTIVES

Abdominal radiography is frequently used in acute abdominal non-traumatic pain despite the availability of more advanced diagnostic modalities. This study evaluates the diagnostic accuracy of low-dose CT compared with abdominal radiography, at similar radiation dose levels.

METHODS

Fifty-eight patients were imaged with both methods and were reviewed independently by three radiologists. The reference standard was obtained from the diagnosis in medical records. Sensitivity and specificity were calculated. A systematic review was performed after a literature search, finding a total of six relevant studies including the present.

RESULTS

Overall sensitivity with 95 % CI for CT was 75 % (66-83 %) and 46 % (37-56 %) for radiography. Specificity was 87 % (77-94 %) for both methods. In the systematic review the overall sensitivity for CT varied between 75 and 96 % with specificity from 83 to 95 % while the overall sensitivity for abdominal radiography varied between 30 and 77 % with specificity 75 to 88 %.

CONCLUSIONS

Based on the current study and available evidence, low-dose CT has higher diagnostic accuracy than abdominal radiography and it should, where logistically possible, replace abdominal radiography in the workup of adult patients with acute non-traumatic abdominal pain.

KEY POINTS

• Low-dose CT has a higher diagnostic accuracy than radiography. • A systematic review shows that CT has better diagnostic accuracy than radiography. • Radiography has no place in the workup of acute non-traumatic abdominal pain.

Accuracy of 64-row multidetector CT in the diagnosis of surgically treated acute abdomen

OBJECTIVE

To assess the accuracy of 64-row computed tomography (CT) in the differential diagnosis of acute abdomen in the emergency department.

MATERIALS AND METHODS

Prospective analysis of 181 patients with surgically treated acute abdomen.

RESULTS

In 158/181 cases, CT was totally concordant with surgical repertoire. Partial concordance was found in 15 cases. Overall sensitivity was 87.3% when only cases of complete concordance were considered, 95.6% if also partial concordance cases were included.

CONCLUSION

CT showed high reliability in the differential diagnosis of acute abdomen surgically treated, although associated conditions can sometimes be missed.

The accuracy of 64-slice MDCT for determining the perforation site of the gastrointestinal tract: ROC analysis

PURPOSE

This study was performed to evaluate the diagnostic performance of 64-slice multidetector-row computed tomography (MDCT) for preoperatively detecting the perforation site in patients with gastrointestinal (GI) tract perforations.

MATERIALS AND METHODS

A total of 49 patients with pathologically proven GI tract perforations, who had undergone MDCT were included in this study. The contrast-enhanced axial images (3 mm thick) and multiplanar reformation (MPR) images (3 mm thick) were generated for all the patients. Two radiologists independently reviewed the two sets of MDCT images (axial set: the axial images alone, and combined set: the axial and MPR images) for the detection of the perforation site. The perforation site was considered to be positive according to the direct and indirect findings. The diagnostic accuracy was assessed with a receiver operating characteristic (ROC) analysis. Weighted kappa statistics were used to evaluate the interobserver agreement.

RESULTS

The corresponding values in respect of the first and the second observers for the areas under the ROC curve were 0.984 and 0.966 for the axial set; and 0.998 and 0.973 for the combined set. The differences were not statistically significant between the two data sets for each observer (P > 0.05). Both the observers detected the perforation site in 43 (87.8%) and 40 (81.6%) patients on the axial set, and in 46 (93.9%) and 41 (83.7%) patients on the combined set, respectively. The kappa values between the two observers showed excellent agreement with the two data sets.

CONCLUSION

64-slice MDCT showed a consistently excellent diagnostic performance for preoperatively determining the perforation site in patients with GI tract perforations, irrespective of the availability of the MPR images.