Portal phase alone is equivalent to multiphasic phase for CT diagnosis of acute non-traumatic pains in an emergency context
Herpe G, Boucebci S, Cassan T, Verdier M, Simonet C, Sztark G, Tasu JP
Emerg Radiol. 2020 Apr;27(2):151-156
Acute non-traumatic abdominal emergencies (ANTAE) represent one of the most frequent causes of access in the ED (1), embracing life-threatening conditions and self-limiting ones. Due to the comparable clinical findings and lack of sensibility and specificity of laboratory tests, ANTAE is a medical challenge for emergency physicians. For this reason, imaging is often required for definitive diagnosis and treatment (2).
Although ultrasonography is the first-choice non-invasive imaging modality, multidetector computed tomography (MDCT) has shown stronger accuracy in reaching the correct diagnosis (3). Multiphasic scanning protocol – which includes the acquisition in pre-contrast, arterial, portal venous, and delayed phases of contrast enhancement – is usually the most common approach (3), even though many recent publications (2, 4, 5) have demonstrated that in specific clinical non-traumatic abdominal settings the correct diagnosis can be reached with the same accuracy cutting off unnecessary phases and thus significantly lowering radiation exposure.
Herpe G. and coworkers emphasize the importance of lowering radiation exposure assessing that portal-phase only (PVP) acquisition protocol is equivalent to a multiphasic one, in term of radiological diagnosis concordance of ANTAE in the ED. The authors performed a retrospective study including 250 patients admitted to the ED for suspected ANTAE, including at least a pre-contrast phase, late arterial phase (LAP) and portal phase (PVP). Cases of suspected active hemorrhage and known malignancies were secondarily excluded since the multiphasic protocol is here recommended (6). 196 CT studies were examined. The multiphasic protocol (pre-contrast phase ± LAP + PVP) and the PVP alone were reviewed independently by nine radiologists who determined the most appropriate diagnosis with five-point confidence scale. Diagnosis concordance and radiation were compared by chi-square test: PVP-alone diagnosis was concordant with the multiphasic protocol without difference in term of confidence reading (kappa coefficient between the two diagnosis 98,5% (CI 95%= 95.6–99.7, p < 0.001), with a 61% decrease of radiation dose.
Results are consistent with other previous publications, confirming the inter-observer agreement between multiphasic and simplified acquisition protocol in abdomino-pelvic CT in the ED (2, 4, 5, 7), suggesting that in this scenario limiting radiation exposure does not have an impact on the management of patients.
However, to the best of our knowledge, there are no guidelines on how to standardize CT protocol in ANTAE since the most appropriate protocol relies upon clinical presentation (8). For this reason, when it is not possible to exclude malignancies and/or active bleeding from the initial clinical evaluation, multiphasic protocol should remain the gold standard (6). The most clinically relevant limit of this approach remains misinterpretation of spontaneously hyper-dense structures (i.e. biliary tract stones), difficult to detect and characterized with the only PVP phase. Nevertheless, some authors have suggested that additional scan might be taken with minimal doses (9, 10) just to obtain the additional necessary information limiting radiation exposure and without compromising the diagnostic accuracy of the exam.
In conclusion, considering the limitations of the study (e.g., retrospective design, low number of patients, lack of data about diagnostic accuracy) it is important to bear in mind the importance of using adequate protocols in the ED avoiding unnecessary ionizing radiation exposure, as many patients admitted in the ED suffer from acute self-limiting benign diseases.
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- Hwang SH, You JS, Song MK, Choi JY, Kim MJ, Chung YE. Comparison of diagnostic performance between single- and multiphasic contrast-enhanced abdominopelvic computed tomography in patients admitted to the emergency department with abdominal pain: potential radiation dose reduction. European radiology 2015;25(4):1048-58.
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Dr. Alessandro Onori is a first-year radiology resident at Sapienza, University of Rome. He graduated at Sapienza University of Rome with a dissertation on AI applications in differential diagnosis of interstitial lung diseases. He is currently involved in both diagnostic and interventional radiology training, polarizing his interests towards emergency radiology and vascular minimally-invasive procedures.
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