Suspicion of appendicitis in pregnant women: emergency evaluation by sonography and low-dose CT with oral contrast

CAR/CETARS/CSAR Practice Guideline on Imaging the Adult Patient With Right Lower Quadrant Pain

In 2023, the Canadian Society of Abdominal Radiology (CSAR) and Canadian Emergency, Trauma, and Acute Care Radiology Society (CETARS) received Canadian Association of Radiologists (CAR) member feedback that there was an unmet educational need for guidance in the imaging investigation of right lower quadrant (RLQ) pain. Members requested specific guidance on how to handle controversial scenarios including which test to order when, specifics of imaging protocols, and managing pregnant patients who have RLQ pain-all from a Canadian perspective. After conducting an exhaustive literature review, the working group agreed that a Canadian-specific set of guidelines was warranted. The management recommendations presented in this guideline were discussed as a group to achieve expert consensus. As the workup for RLQ pain can vary considerably in the paediatric population, the scope of this paper was restricted to adults (18 years of age or older). Whenever possible, the best evidence was used to inform the clinical guidance, and where gaps existed, the guidelines reflect consensus among experts in the field. The result is a framework to aid in this process of managing patients with RLQ pain across various clinical scenarios while addressing current questions and controversies, particularly those most relevant to the Canadian healthcare system.

ACR Appropriateness Criteria® Right Lower Quadrant Pain: 2022 Update

This document focuses on imaging in the adult and pregnant populations with right lower quadrant (RLQ) abdominal pain, including patients with fever and leukocytosis. Appendicitis remains the most common surgical pathology responsible for RLQ abdominal pain in the United States. Other causes of RLQ pain include right colonic diverticulitis, ureteral stone, and infectious enterocolitis. Appropriate imaging in the diagnosis of appendicitis has resulted in decreased negative appendectomy rate from as high as 25% to approximately 1% to 3%. Contrast-enhanced CT remains the primary and most appropriate imaging modality to evaluate this patient population. MRI is approaching CT in sensitivity and specificity as this technology becomes more widely available and utilization increases. Unenhanced MRI and ultrasound remain the diagnostic procedures of choice in the pregnant patient. MRI and ultrasound continue to perform best in the hands of the experts. 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 process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Accuracy of Point-of-care Ultrasound in Diagnosing Acute Appendicitis During Pregnancy

Introduction: Acute appendicitis is the most common non-obstetrical surgical emergency in pregnancy. Ultrasound is the imaging tool of choice, but its use is complicated due to anatomical changes during pregnancy and depends on the clinician’s expertise. In this study, our aim was to investigate the diagnostic accuracy of point-of-care ultrasound (POCUS) in suspected appendicitis in pregnant women. Methods: We conducted a retrospective analysis of all pregnant women undergoing POCUS for suspected appendicitis between June 2010–June 2020 in a tertiary emergency department. The primary outcome was to establish sensitivity, specificity, and likelihood ratios of POCUS in diagnosing acute appendicitis, overall and for each trimester. We used histology of the appendix as the reference standard in case of surgery. If appendectomy was not performed, the clinical course until childbirth was used to rule out appendicitis. If the patients underwent magnetic resonance imaging (MRI), we compared readings to POCUS. Results: A total of 61 women were included in the study, of whom 34 (55.7%) underwent appendectomy and in 30 (49.2%) an acute appendicitis was histopathologically confirmed. Sensitivity of POCUS was 66.7% (confidence interval [CI] 95% 47.1-82.7), specificity 96.8% (CI 95% 83.3-99.9), and positive likelihood ratio 20.7. Performance of POCUS was comparable in all trimesters, with highest sensitivity in the first trimester (72.7%). The MRI reading showed a sensitivity of 84.6% and a specificity of 100%. In the four negative appendectomies a MRI was not performed. Conclusion: Point-of-care ultrasound showed a high specificity and positive likelihood ratio in diagnosing acute appendicitis in pregnant women in all trimesters with suspected appendicitis. In negative (or inconclusive) cases further imaging as MRI could be helpful to avoid negative appendectomy.

Role of Ultrasound in the Assessment and Differential Diagnosis of Pelvic Pain in Pregnancy

Pelvic pain (PP) is common in pregnant women and can be caused by several diseases, including obstetrics, gynaecological, gastrointestinal, genitourinary, and vascular disorders. Timely and accurate diagnosis as well as prompt treatment are crucial for the well-being of the mother and foetus. However, these are very challenging. It should be considered that the physiological changes occurring during pregnancy may confuse the diagnosis. In this setting, ultrasound (US) represents the first-line imaging technique since it is readily and widely available and does not use ionizing radiations. In some cases, US may be conclusive for the diagnosis (e.g., if it detects no foetal cardiac activity in suspected spontaneous abortion; if it shows an extrauterine gestational sac in suspected ectopic pregnancy; or if it reveals a dilated, aperistaltic, and blind-ending tubular structure arising from the cecum in suspicious of acute appendicitis). Magnetic resonance imaging (MRI), overcoming some limits of US, represents the second-line imaging technique when an US is negative or inconclusive, to detect the cause of bowel obstruction, or to characterize adnexal masses.

Abdominal fellowship-trained versus generalist radiologist accuracy when interpreting MR and CT for the diagnosis of appendicitis

OBJECTIVES

To compare the diagnostic accuracy of generalist radiologists working in a community setting against abdominal radiologists working in an academic setting for the interpretation of MR when diagnosing acute appendicitis among emergency department patients.

METHODS

This observational study examined MR image interpretation (non-contrast MR with diffusion-weighted imaging and intravenous contrast-enhanced MR) from a prospectively enrolled cohort at an academic hospital over 18 months. Eligible patients had an abdominopelvic CT ordered to evaluate for appendicitis and were > 11 years old. The reference standard was a combination of surgery and pathology results, phone follow-up, and chart review. Six radiologists blinded to clinical information, three each from community and academic practices, independently interpreted MR and CT images in random order. We calculated test characteristics for both individual and group (consensus) diagnostic accuracy then performed Chi-square tests to identify any differences between the subgroups.

RESULTS

Analysis included 198 patients (114 women) with a mean age of 31.6 years and an appendicitis prevalence of 32.3%. For generalist radiologists, the sensitivity and specificity (95% confidence interval) were 93.8% (84.6-98.0%) and 88.8% (82.2-93.2%) for MR and 96.9% (88.7-99.8%) and 91.8% (85.8-95.5%) for CT. For fellowship-trained radiologists, the sensitivity and specificity were 96.9% (88.2-99.5%) and 89.6% (82.8-94%) for MR and 98.4% (90.5-99.9%) and 93.3% (87.3-96.7%) for CT. No statistically significant differences were detected between radiologist groups (p = 1.0, p = 0.53, respectively) or when comparing MR to CT (p = 0.21, p = 0.17, respectively).

CONCLUSIONS

MR is a reliable, radiation-free imaging alternative to CT for the evaluation of appendicitis in community-based generalist radiology practices.

KEY POINTS

• There was no significant difference in MR image interpretation accuracy between generalist and abdominal fellowship-trained radiologists when evaluating sensitivity (p = 1.0) and specificity (p = 0.53). • There was no significant difference in accuracy comparing MR to CT imaging for diagnosing appendicitis for either sensitivity (p = 0.21) or specificity (p = 0.17). • With experience, generalist radiologists enhanced their MR interpretation accuracy as demonstrated by improved interpretation sensitivity (OR 2.89 CI 1.44-5.77, p = 0.003) and decreased mean interpretation time (5 to 3.89 min).

Imaging during pregnancy: What the radiologist needs to know

During the last decades, there has been a growing demand for medical imaging in gravid women. Imaging of the pregnant woman is challenging as it involves both the mother and the fetus and, consequently, several medical, ethical, or legal considerations are likely to be raised. Theoretically, all currently available imaging modalities may be used for the evaluation of the pregnant woman; however, in practice, confusion regarding the safety of the fetus often results in unnecessary avoidance of useful diagnostic tests, especially those involving ionizing radiation. This review article is focused on the current safety guidelines and considerations regarding the use of different imaging modalities in the pregnant population; also presented is an imaging work-up for the most common medical conditions of pregnant women, with emphasis on fetal and maternal safety.

Diagnostic performance of ultra-low dose versus standard dose CT for non-traumatic abdominal emergencies

PURPOSE

The purpose of this study was to compare the diagnostic performance of ultra-low dose (ULD) to that of standard (STD) computed tomography (CT) for the diagnosis of non-traumatic abdominal emergencies using clinical follow-up as reference standard.

MATERIALS AND METHODS

All consecutive patients requiring emergency abdomen-pelvic CT examination from March 2017 to September 2017 were prospectively included. ULD and STD CTs were acquired after intravenous administration iodinated contrast medium (portal phase). CT acquisitions were performed at 125mAs for STD and 55mAs for ULD. Diagnostic performance was retrospectively evaluated on ULD and STD CTs using clinical follow-up as a reference diagnosis.

RESULTS

A total of 308 CT examinations from 308 patients (145 men; mean age 59.1±20.7 (SD) years; age range: 18-96 years) were included; among which 241/308 (78.2%) showed abnormal findings. The effective dose was significantly lower with the ULD protocol (1.55±1.03 [SD] mSv) than with the STD (3.67±2.56 [SD] mSv) (P<0.001). Sensitivity was significantly lower for the ULD protocol (85.5% [95%CI: 80.4-89.4]) than for the STD (93.4% [95%CI: 89.4-95.9], P<0.001) whereas specificities were similar (94.0% [95%CI: 85.1-98.0] vs. 95.5% [95%CI: 87.0-98.9], respectively). ULD sensitivity was equivalent to STD for bowel obstruction and colitis/diverticulitis (96.4% [95%CI: 87.0-99.6] and 86.5% [95%CI: 74.3-93.5] for ULD vs. 96.4% [95%CI: 87.0-99.6] and 88.5% [95%CI: 76.5-94.9] for STD, respectively) but lower for appendicitis, pyelonephritis, abscesses and renal colic (75.0% [95%CI: 57.6-86.9]; 77.3% [95%CI: 56.0-90.1]; 90.5% [95%CI: 69.6-98.4] and 85% [95%CI: 62.9-95.4] for ULD vs. 93.8% [95%CI: 78.6-99.2]; 95.5% [95%CI: 76.2-100.0]; 100.0% [95%CI: 81.4-100.0] and 100.0% [95%CI: 80.6-100.0] for STD, respectively). Sensitivities were significantly different between the two protocols only for appendicitis (P=0.041).

CONCLUSION

In an emergency context, for patients with non-traumatic abdominal emergencies, ULD-CT showed inferior diagnostic performance compared to STD-CT for most abdominal conditions except for bowel obstruction and colitis/diverticulitis detection.

Magnetic resonance imaging reduces the rate of unnecessary operations in pregnant patients with suspected acute appendicitis: a retrospective study

Purpose

This is a retrospective single-institution study performed to compare the rate of unnecessary operations in pregnant women with suspected acute appendicitis with and without the use of MRI.

Methods

The study subjects were all pregnant women with suspected acute appendicitis admitted to a tertiary institution from January 2012 to December 2019. If acute appendicitis was not excluded clinically and by ultrasound (US), laparoscopies were performed until May 2017 (US-only group). MRI was added as a diagnostic tool when US was inconclusive from May 2017 (US + MRI group). Surgery was considered unnecessary when no inflamed appendix was found. The rate of unnecessary surgery, postoperative complications, length of stay were analyzed.

Results

Seventy-six women were included in the study; 38 women in the US-only group and 38 women in the US + MRI group. There were no differences in admission characteristics between the groups. One of 38 women (2.6%) underwent unnecessary surgery in the US + MRI group vs. 10 of 38 (26.3%) in the US-only group (P = 0.007). The patients in the US + MRI group were significantly less likely to undergo a diagnostic operation than in the US-only group (5.26% vs. 55.3%, respectively; P < 0.001) and their hospital stay was significantly shorter (0.74 ± 1.64 days vs. 3.7 ± 3.0 days, respectively; P < 0.001). The obstetric outcomes were not different between the groups. MRI had a sensitivity of 83.3% and specificity of 100% in the series.

Conclusion

The rate of unnecessary surgery was significantly reduced in pregnant women, who underwent MRI after inconclusive transabdominal US.

Body mass index as an indicator of the likelihood of ultrasound visualization of the appendix in pregnant women with suspicion of appendicitis

PURPOSE

To determine if clinical characteristics of pregnant women are associated with the likelihood of ultrasound (US) visualization of the appendix in cases where there is a clinical suspicion of appendicitis.

MATERIALS AND METHODS

A retrospective study of 471 pregnant patients with suspicion of appendicitis from 2009 to 2018 were studied. Patients underwent sonography of the appendix as their initial imaging study. The association of body mass index (BMI) and gestational age with sonographic visualization of the appendix was analyzed using logistic regression. Cut-off values were determined for BMI to predict visualization of the appendix.

RESULTS

The rate of visualization of the appendix on US was 16% (95% CI 12% to 19%). When stratified by trimester of pregnancy, rebound pain on compression US examination in the 1st trimester and BMI in the 2nd and 3rd trimesters were identified as predictors of US visualization. Applying BMI cut-off values rounded to the nearest whole number, 36, 30, and 26 in the 1st, 2nd, and 3rd trimesters, non-visualization rates would be reduced by 16% (95% CI 10% to 25%), 35% (95% CI 29% to 42%), and 67% (95% CI 58% to 74%). Using BMI index cut-off values would reduce the number of primary US examinations by 35% (95% CI 30% to 39%) and increase the rate of visualization by 6% (95% CI 0.02% to 12%, P = 0.04).

CONCLUSION

Using BMI cut-off values for determining the efficaciousness of US visualization of the appendix in pregnant women with suspicion of appendicitis could significantly reduce the non-visualization rate.

Reliability of standardized reporting system of acute appendicitis in adults at low-dose 320-rows CT

Aim

To assess the reliability of a standardized reporting system of acute appendicitis at low-dose 320-rows CT.

Subjects and Methods

Retrospective analysis CT of 78 patients with pathologically proven acute appendicitis. The study was performed at a low-dose 320-rows CT. The image analysis was performed by 2 radiologists according to a standardized reporting system of acute appendicitis.

Results

There was an excellent overall of the inter-observer agreement of both observers for the standardized reporting system of acute appendicitis (K = 0.89, 95 % CI = 0.87-0.92, P = 0.001). There was good inter-observer agreement for visualization of the appendix (K = 0.78, P = 0.001), the tip diameter (K = 0.75, P = 0.001), and a single wall thickness of appendix (K = 0.77, P = 0.001). There was excellent inter-observer agreement for outer to outer wall diameter (K = 0.82, P = 0.001), mucosal hyper-enhancement (K = 0.80, P = 0.001), appendicolith (K = 0.86, P = 0.001), gas in the appendix (K = 0.82, P = 0.001), surrounding fat stranding (K = 0.81, P = 0.001), focal cecal thickening (K = 0.85, P = 0.001), peri-appendiceal air (K = 0.87, P = 0.001), peri-appendicular fluid collection, phlegmon, or abscess (K = 0.82, P = 0.001), and right ovary cyst (K = 0.83, P = 0.001).

Conclusion

we concluded that excellent reliability of a standardized reporting system of acute appendicitis in the adults using low-dose 320-rows CT.

Estimation of the radiation dose in pregnancy: an automated patient-specific model using convolutional neural networks

OBJECTIVES

The conceptus dose during diagnostic imaging procedures for pregnant patients raises health concerns owing to the high radiosensitivity of the developing embryo/fetus. The aim of this work is to develop a methodology for automated construction of patient-specific computational phantoms based on actual patient CT images to enable accurate estimation of conceptus dose.

METHODS

We developed a 3D deep convolutional network algorithm for automated segmentation of CT images to build realistic computational phantoms. The neural network architecture consists of analysis and synthesis paths with four resolution levels each, trained on manually labeled CT scans of six identified anatomical structures. Thirty-two CT exams were augmented to 128 datasets and randomly split into 80%/20% for training/testing. The absorbed doses for six segmented organs/tissues from abdominal CT scans were estimated using Monte Carlo calculations. The resulting radiation doses were then compared between the computational models generated using automated segmentation and manual segmentation, serving as reference.

RESULTS

The Dice similarity coefficient for identified internal organs between manual segmentation and automated segmentation results varies from 0.92 to 0.98 while the mean Hausdorff distance for the uterus is 16.1 mm. The mean absorbed dose for the uterus is 2.9 mGy whereas the mean organ dose differences between manual and automated segmentation techniques are 0.07%, - 0.45%, - 1.55%, - 0.48%, - 0.12%, and 0.28% for the kidney, liver, lung, skeleton, uterus, and total body, respectively.

CONCLUSION

The proposed methodology allows automated construction of realistic computational models that can be exploited to estimate patient-specific organ radiation doses from radiological imaging procedures.

KEY POINTS

• The conceptus dose during diagnostic radiology and nuclear medicine imaging procedures for pregnant patients raises health concerns owing to the high radiosensitivity of the developing embryo/fetus. • The proposed methodology allows automated construction of realistic computational models that can be exploited to estimate patient-specific organ radiation doses from radiological imaging procedures. • The dosimetric results can be used for the risk-benefit analysis of radiation hazards to conceptus from diagnostic imaging procedures, thus guiding the decision-making process.