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

Computed tomography versus ultrasound for the diagnosis of acute cholecystitis: a systematic review and meta-analysis

OBJECTIVES

Some patients undergo both computed tomography (CT) and ultrasound (US) sequentially as part of the same evaluation for acute cholecystitis (AC). Our goal was to perform a systematic review and meta-analysis comparing the diagnostic performance of US and CT in the diagnosis of AC.

MATERIALS AND METHODS

Databases were searched for relevant published studies through November 2023. The primary objective was to compare the head-to-head performance of US and CT using surgical intervention or clinical follow-up as the reference standard. For the secondary analysis, all individual US and CT studies were analyzed. The pooled sensitivities, specificities, and areas under the curve (AUCs) were determined along with 95% confidence intervals (CIs). The prevalence of imaging findings was also evaluated.

RESULTS

Sixty-four studies met the inclusion criteria. In the primary analysis of head-to-head studies (n = 5), CT had a pooled sensitivity of 83.9% (95% CI, 78.4-88.2%) versus 79.0% (95% CI, 68.8-86.6%) of US (p = 0.44). The pooled specificity of CT was 94% (95% CI, 82.0-98.0%) versus 93.6% (95% CI, 79.4-98.2%) of US (p = 0.85). The concordance of positive or negative test between both modalities was 82.3% (95% CI, 72.1-89.4%). US and CT led to a positive change in management in only 4 to 8% of cases, respectively, when ordered sequentially after the other test.

CONCLUSION

The diagnostic performance of CT is comparable to US for the diagnosis of acute cholecystitis, with a high rate of concordance between the two modalities.

CLINICAL RELEVANCE STATEMENT

A subsequent US after a positive or negative CT for suspected acute cholecystitis may be unnecessary in most cases.

KEY POINTS

When there is clinical suspicion of acute cholecystitis, patients will often undergo both CT and US. CT has similar sensitivity and specificity compared to US for the diagnosis of acute cholecystitis. The concordance rate between CT and US for the diagnosis of acute cholecystitis is 82.3%.

Usefulness of Corticomedullary-Phase CT Urography in Patients with Suspected Acute Renal Colic Visiting the Emergency Department

PURPOSE

To evaluate the sensitivity of corticomedullary-phase imaging for detecting urinary stones in patients with renal colic who visited the emergency department.

MATERIALS AND METHODS

This retrospective study included 253 patients with suspected renal colic from two tertiary hospitals in South Korea, who visited the emergency department and underwent CT urography. Two radiologists blinded to the clinical history independently reviewed the corticomedullary-phase images. The sensitivity for identifying urinary stones were evaluated for each reviewer. After the initial evaluation, the images were re-evaluated based on patient history. The sensitivity of re-evaluation were recorded.

RESULTS

Of 253 patients, 150 (59%) had urinary stones. Among them, significant stones were observed in 138 patients (92%), and obstructive changes on CT in 124 patients (82.7%). For identifying significant urinary stones, the sensitivity was 98.6% (136/138) for both the reviewers. For identifying significant urinary stones with urinary obstruction, the sensitivity was 99.2% (123/124) for reviewer 1, and 100% (124/124) for reviewer 2. The sensitivity for identifying significant stones increased from 98.6% to 100% for reviewer 1, and from 98.6% to 99.3% for reviewer 2 in the re-evaluation session.

CONCLUSION

The corticomedullary-phase CT urography was sensitive for diagnosing urolithiasis in patients with acute renal colic who visited the emergency department.

ACR Appropriateness Criteria® Right Upper Quadrant Pain: 2022 Update

Acute right upper quadrant pain is one of the most common presenting symptoms in hospital emergency departments, as well as outpatient settings. Although gallstone-related acute cholecystitis is a leading consideration in diagnosis, a myriad of extrabiliary sources including hepatic, pancreatic, gastroduodenal, and musculoskeletal should also be considered. This document focuses on the diagnostic accuracy of imaging studies performed specifically to evaluate acute right upper quadrant pain, with biliary etiologies including acute cholecystitis and its complications being the most common. An additional consideration of extrabiliary sources such as acute pancreatitis, peptic ulcer disease, ascending cholangitis, liver abscess, hepatitis, and painful liver neoplasms remain a diagnostic consideration in the right clinical setting. The use of radiographs, ultrasound, nuclear medicine, CT, and MRI for these indications are discussed. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Tailored versus fixed scan delay in contrast-enhanced abdominal multi-detector CT: An intra-patient comparison of image quality

PURPOSE

To perform anintra-patient comparison betweena single-pass protocol (SP) and a portal venous phase (PVP) by means ofboth quantitative and qualitative analysis of image quality.

METHODS

Forty patients (31 M; 9F; aged 20-77 years; BMI 23 ± 4 Kg/m²) underwent both a SP and a PVP using a 64-rows multi-detector CT with a median interval time of 56 days (range5-903). All patients underwent i.v. bolus injection (2.0 cc/sec) of 1.7 cc/Kg of a non ionic iodinated contrast-media (370 mgI/ml) with scan delays of 67 ± 8 and 90 s for the SP and the PVP, respectively. Signal- (SNR) and contrast-to-noise ratios (CNR) were calculated for most visceral organs and for both abdominal aorta (AA) and main portal vein (MPV). For qualitative analysis, reproduction of abdominal viscera and vascular structures was blindly evaluated and inter-observer agreement calculated by the weighted Cohen k-analysis.

RESULTS

Attenuation values (H.U.) of AA (232 ± 53vs180 ± 36) and MPV (215 ± 39vs187 ± 42) were significantly (p < 0.001) higher in the SP than in PVP, respectively. At qualitative analysis, reproduction of mostabdominal viscerawas also significantly sharper (p < 0.001) with the SP than the PVPwith inter-observer agreement scores (k)ranging from 0.60 to 0.88 for all but one imaging criteria.

CONCLUSIONS

As the SP resulted in a significantly higher vascular enhancement and in a sharper reproduction of most abdominal viscera, it may be better suited than a PVP for the CT evaluation of non traumatic acute abdomen.

Computed tomography for detection of septic foci: Retrospective analysis of patients presenting to the emergency department

OBJECTIVE

Sepsis is defined as organ dysfunction due to severe infection. Septic patients face a significant mortality risk. Thus, timely recognition with prompt focus identification and control are essential. This study aims to determine the current role of computed tomography (CT) in the diagnostic workup of septic patients.

METHODS

We retrospectively identified 357 patients in the emergency department (ED) of a large university center with suspected sepsis in a two-year period. A total of 132 patients underwent CT scanning within 72 h of admission. Patients were characterized by clinical and laboratory findings. CT reports were categorized and matched with clinical data.

RESULTS

Of 357 ED patients with suspected sepsis, 37.0% (132/357) underwent CT imaging within 72 h. The most commonly identified septic foci in CT were chest 38.6% (49/127), abdomen 22.0% (28/127) and genitourinary tract 20.5% (26/127) in descending order. The focus detection rate was 76.5% per patient with a concurrent number-needed-to-scan of 1.31. Contrast medium administration in CT did not improve focus detection rate (p = 0.631) or diagnostic confidence in this patient population (p = 0.432). CT had a positive predictive value of 81.82% (CI 76.31 to 86.28%) in predicting the focus of the discharge diagnosis. Follow-up imaging in patients with unclear focus reveals a new focus in 39.5% of patients.

CONCLUSIONS

Our investigation of the role of CT in ED patients with suspected sepsis indicated a high positive predictive value for CT with regard to the discharge diagnosis. Repeat imaging may help identify further septic foci in a subgroup with persistently unclear focus. Use of contrast medium seems less relevant for focus detection than expected, as it did not increase diagnostic confidence.

Accuracy of Nonenhanced CT vs Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults

BACKGROUND

Acute appendicitis is one of the most common causes of acute abdominal pain requiring emergency intervention. It is often difficult for the clinician to make an accurate diagnosis due to nonspecific and overlapping clinical symptoms. Computed tomography (CT) has become the imaging modality of choice for the evaluation of suspected acute appendicitis. The main purpose of our study was to compare nonenhanced CT (NECT) with contrast-enhanced CT (CECT) for the diagnosis of acute appendicitis.

MATERIAL AND METHODS

A total of 140 patients were enrolled in the study. Two abdominal radiologists-masked to both the clinical information and the final diagnosis-retrospectively reviewed the computed tomographic findings and made an imaging diagnosis based on (1) NECT only, (2) CECT only, and (3) both NECT and CECT. With the final diagnosis as the reference standard, the accuracy of each CT technique was estimated.

RESULTS

The respective sensitivity, specificity, and accuracy for NECT, CECT, and NECT + CECT for the diagnosis of acute appendicitis were 80.7%, 86.7%, and 84.3%; 86.0%, 81.9%, and 83.6%; and, 87.7%, 80.7%, and 83.6%. There was no significant difference in the diagnosis of acute appendicitis among the 3 techniques. In order to make a correct diagnosis, the presence of at least 3 imaging findings for NECT or at least 4 for CECT had the best diagnostic accuracy. We also found that 9.25 mm was the optimal cut-off threshold for the detection of patients with acute appendicitis.

CONCLUSION

Our study allowed direct comparison between NECT, CECT, and NECT + CECT combined. There was no difference in the ability of each CT technique for diagnosing patients with acute appendicitis. For a patient whom iodinated contrast media is contraindicated or a patient who has an increased risk of severe adverse reaction, we would encourage the use of NECT because it provides comparable diagnostic accuracy without further exposing such patient to the contrast media.

Portal phase alone is equivalent to multiphasic phase for CT diagnosis of acute non-traumatic pains in an emergency context

OBJECTIVES

To evaluate radiological diagnosis concordance between a simplified and a multiphasic computed tomography (MCT) protocol for patients presenting acute non-traumatic abdominal pains (ANTAE).

METHODS

During five consecutive months, all patients admitted in an emergency department for ANTAE were retrospectively included if they underwent MCT, including at least pre-contrast phase, late arterial phase (LAP), and portal venous phase (PVP). Clinical cases of suspected hemorrhagic conditions were secondarily excluded. For the study, two image sets, pre-contrast phase + LAP + PVP ± late phase called S1 and PVP alone called S2, were reviewed independently to give the most appropriate diagnosis with 5-point confidence scale. Diagnosis concordance and radiation dose were compared for each set of protocol by chi-square test. Linear mixed model was used to assess changes of diagnostic confidence and radiation dose.

RESULTS

All in all, 196 patients were included. The kappa coefficient between S1 and S2 was excellent (98.5%, CI_95% 95.6-99.7). Three errors due to an inappropriate protocol were observed (1.5%; CI_95% = - 0.2 to 3.2%), 2 related to biliary tract obstruction causes and one due to gastric bleeding not suspected on clinical data. S2 was associated with a 61% decrease of the radiation dose (p = 0.01) with a mild decrease of the confidence scale (4.54 ± 0.05 versus 4.74 ± 0.03, p = 0.001).

CONCLUSION

Using PVP-CT alone or MCT is equivalent for the diagnosis of ANTAE if suspected acute hemorrhages are excluded. A simplified CT protocol is associated with a dose decrease of 61%.

Triple-phase abdomen and pelvis computed tomography: standard unenhanced phase can be replaced with reduced-dose scan

Purpose

The aim of the study was to test the hypothesis that unenhanced phase does not require as high image quality as subsequent phases acquired after contrast administration in triple-phase abdomen and pelvis computed tomography (CT), and to assess if attenuation value (AV) measurements may be obtained from unenhanced images acquired with three-fold reduced radiation dose.

Material and methods

In the standard triple-phase abdomen and pelvis CT protocol (unenhanced, late arterial, and portal venous phase) we decreased the tube current time product only in the unenhanced phase. Arterial and venous phases were performed with the standard scanner settings used in our Institution for routine abdomen and pelvis CT. We compared the AV in manually drawn circular-shaped regions of interest (ROIs) obtained from reduced-dose and standard-dose unenhanced images in 52 patients. All ROIs were set in homogeneous parts of psoas muscle, fat tissue, liver, spleen, aorta, and bladder.

Results

There was no statistically significant difference in AV measurements for all considered areas. More noise does not alter the mean AV inside the ROIs. Radiation dose of unenhanced scans was reduced three times and the total dose length product (DLP) in the triple-phase study was decreased by 22%.

Conclusions

Unenhanced images performed with three-fold reduced radiation dose allows reliable AV measurements. The unenhanced phase does not require as high image quality as subsequent phases acquired after contrast administration.

Are the unenhanced and excretory CT phases necessary for the evaluation of acute pyelonephritis?

Background The most widely accepted computed tomography (CT) protocol for diagnosis of acute pyelonephritis (APN) includes at least a pre- and post-contrast scan, which may expose patients to higher doses of ionizing radiation. Purpose To establish the accuracy, reproducibility, and degree of confidence in CT diagnosis of acute pyelonephritis (APN) and urolithiasis using only images obtained during the nephrographic phase. Material and Methods A retrospective study of 100 consecutive patients (88 women; age range, 19-70 years) with clinical and laboratory suspicion of APN and who underwent triphasic abdominal CT scans (non-contrast, nephrographic, and excretory phases) was performed. Two readers first evaluated independently only the nephrographic phase of scans, and, in a second session, the entire study. The diagnostic reference standard was settled by a third experienced radiologist who reviewed all triphasic scans and clinical data. Results The accuracy of only nephrographic phase for diagnosis of APN and urolithiasis was in the range of 90.3-91.78% and 96.27-99.25%, respectively. There was no significant difference in comparison with the triphasic reading (z: -0.4 - 0.2; P = 0.34-0.83). The average degree of confidence for APN also showed no significant variation for both readers ( P = 0.4 and 0.08). Almost perfect inter-observer agreements for the diagnosis of APN (k = 0.86, P < 0.001) and for urolithiasis (k = 0.84, P < 0.001) were observed when considering only the nephrographic phase. Conclusion CT assessment of APN and urolithiasis can be accurately performed using only the late nephrographic phase, with consequent dose reduction.

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.