The clinical utility of inpatient MRI following an abdominopelvic CT

PURPOSE

The purpose of this study was to assess the diagnostic yield of abdomen magnetic resonance imaging (MRI) in the inpatient setting following a computed tomography (CT).

METHODS

All inpatient abdominopelvic MRIs performed on patients for a 1-year period were identified and medical records were retrospectively reviewed for the following information. Only MRIs with a preceding CT were included in the study.

RESULTS

A total of 221 MRIs were included. Forty exams were deemed technically inadequate due to motion, while 9 more patients did not tolerate a full examination. The most common indications were focal liver lesion (n = 101), pancreaticobiliary ductal dilatation (n = 39), abnormal liver function tests (n = 26), acute pancreatitis (n = 14), abdominal pain (n = 10), and fever/sepsis (n = 10). 83 MRIs were recommended on CT and 138 were requests from the care team. In 63 cases, MRI offered new information over CT. Thirty-two MRIs recommended by radiologists affected patient management, while only 31 MRIs recommended by the care team affected management. Of these 63 MRIs, 29 cases changed immediate inpatient management, requiring further intervention. In these cases, MRI identified abscesses, choledocholithiasis, or made other diagnoses such as cholecystitis, which were not diagnosed on CT. Patient LOS increased in 24 patients in order to receive an MRI. Average costs of outpatient CTs and MRIs are typically 20% less than inpatient costs.

CONCLUSION

Inpatient abdomen MRIs have limited impact on patient care following a CECT and entail higher cost, utilize more resources, scanner time, and increase patient LOS. Therefore, it should be reserved for select clinical indications.

Nonfetal Imaging During Pregnancy: Acute Abdomen/Pelvis

Abdominal pain is a common occurrence in pregnant women and may have a variety of causes, including those that are specific to pregnancy (eg, round ligament pain in the first trimester) and the wide range of causes of abdominal pain that affect men and women who are not pregnant (eg, appendicitis, acute cholecystitis). Noncontrast magnetic resonance (MR) imaging is increasingly performed to evaluate pregnant women with abdominal pain, either as the first-line test or as a second test following ultrasonography. The imaging appearance of causes of abdominal pain in pregnant women are reviewed with an emphasis on noncontrast MR imaging.

Morphologic criteria of vermiform appendix on computed tomography and a possible risk of developing acute appendicitis

Objective

To evaluate the correlation of morphological criteria of the cecal appendix using computed tomography (CT) and the possible risk of developing acute appendicitis.

Materials and Methods

Cases were defined as patients with surgically confirmed acute appendicitis who had undergone CT at least twice: at diagnosis and at least one month prior. Controls were defined as emergency patients with abdominal pain who had undergone abdominal CT that excluded acute appendicitis and had also undergone CT at least one month before.

Results

100 cases and 100 controls were selected for inclusion in the final analysis. Comparisons between the cases and controls revealed the following: mean transverse diameter of 0.6 cm (range, 0.4-1.0 cm) versus 0.6 cm (range, 0.6-0.8 cm; p = 0.37); mean length of 6.6 cm (range, 3.5-9.7 cm) versus 6.6 cm (range, 4.5-8.3 cm; p = 0.87); mean angle of 100° (range, 23-178°) versus 86° (range, 43-160°; p = 0.01); vertical descending orientation in 56% versus 45% (p = 0.2); absence of gas in 69% versus 77% (p = 0.34); and presence of an appendicolith in 17% versus 8% (p = 0.08).

Conclusion

Hypothetical risk factors for obstruction of the vermiform appendix detected on CT were not associated with acute appendicitis. That suggests that factors other than those related to mechanical obstruction are implicated in the pathogenesis of acute appendicitis.

T1 bright appendix sign to exclude acute appendicitis in pregnant women

OBJECTIVE

To evaluate the diagnostic value of the T1 bright appendix sign for the diagnosis of acute appendicitis in pregnant women.

MATERIAL AND METHODS

This retrospective study included 125 pregnant women with suspected appendicitis who underwent magnetic resonance (MR) imaging. The T1 bright appendix sign was defined as a high intensity signal filling more than half length of the appendix on T1-weighted imaging. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the T1 bright appendix sign for normal appendix identification were calculated in all patients and in those with borderline-sized appendices (6-7 mm).

RESULTS

The T1 bright appendix sign was seen in 51% of patients with normal appendices, but only in 4.5% of patients with acute appendicitis. The overall sensitivity, specificity, PPV, and NPV of the T1 bright appendix sign for normal appendix diagnosis were 44.9%, 95.5%, 97.6%, and 30.0%, respectively. All four patients with borderline sized appendix with appendicitis showed negative T1 bright appendix sign.

CONCLUSION

The T1 bright appendix sign is a specific finding for the diagnosis of a normal appendix in pregnant women with suspected acute appendicitis.

KEY POINTS

• Magnetic resonance imaging is increasingly used in emergency settings. • Acute appendicitis is the most common cause of acute abdomen. • Magnetic resonance imaging is widely used in pregnant population. • T1 bright appendix sign can be a specific sign representing normal appendix.

MRI for appendicitis in pregnancy: is seeing believing? clinical outcomes in cases of appendix nonvisualization

PURPOSE

The primary objective of this study was to determine the clinical outcomes in cases of appendix nonvisualization with MRI in pregnant patients with suspected appendicitis and the implications of appendix nonvisualization for excluding appendicitis.

METHODS

Fifty-eight pregnant patients with suspected appendicitis evaluated with MRI at three centers from a single institution were retrospectively reviewed by three radiologists with varying levels of abdominal imaging experience. All scans were performed on a 1.5-Tesla Siemens unit. Cases were evaluated for diagnostic quality, visualization of the appendix, presence of appendicitis, and alternate diagnoses. Clinical outcomes were gathered from the electronic medical record.

RESULTS

Of the 58 patients who underwent MRI for suspected appendicitis, 50 cases were considered adequate diagnostic quality by all three radiologists. The rate of appendix visualization among the three radiologists ranged from 60 to 76% (p = 0.44). The appendix was nonvisualized by at least one of the three radiologists in 25 cases (50%). Of these, none had a final diagnosis of appendicitis including one patient who underwent appendectomy. MRI suggested an alternate diagnosis in 6 (24%) patients with appendix nonvisualization. For the three reviewers, the agreement level on whether or not the appendix was visualized on the MRI had a Light's kappa value of 0.526, indicating a "moderate" level of agreement (p value < 0.01).

CONCLUSION

Despite only moderate level of interobserver agreement for appendix visualization, appendix nonvisualization on MRI in pregnant patients with suspected appendicitis confers a significant reduction in the risk of appendicitis compared to all comers as long as the study is adequate diagnostic quality and there are no secondary signs of appendicitis present.

Emergency abdominal MRI: current uses and trends

When evaluating the abdomen in the emergency setting, CT and ultrasound are the imaging modalities of choice, mainly because of accessibility, speed and lower relative cost. CT has the added benefit of assessing the whole abdomen for a wide spectrum of gastrointestinal disease, whereas ultrasound has the benefit of avoiding ionizing radiation. MRI is another tool that has demonstrated increasing utility in the emergency setting and also avoids the use of ionizing radiation. MRI also has the additional advantage of excellent soft-tissue contrast. However, widespread use of MRI in the emergency setting is limited by availability and relative cost. Despite such limitations, advances in MRI technology, including improved pulse sequences and coil technology and increasing clinician awareness of MRI, have led to an increased demand in abdominal MRI in the emergency setting. This is particularly true in the evaluation of acute pancreatitis; choledocholithiasis with or without cholecystitis; acute appendicitis, particularly in pregnant patients; and, in some cases, Crohn's disease. In cases of pancreatitis and Crohn's disease, MRI also plays a role in subsequent follow-up examinations.

Magnetic resonance imaging of acute abdominal and pelvic pain in pregnancy

Evaluation of acute abdominal and pelvic pain in pregnancy presents a diagnostic challenge for clinicians and radiologists alike. The differential diagnosis includes obstetric and nonobstetric conditions unique to pregnancy, in addition to causes of acute abdominal and pelvic pain unrelated to the pregnancy. The clinical presentation and course of disease may be altered in pregnancy, and several pathologies are exacerbated by pregnancy. Discriminating clinical features in the diagnosis of abdominal and pelvic pain are often confounded by expected anatomic and physiologic changes in pregnancy. Moreover, while diagnostic pathways may be altered in pregnancy, the necessity for a timely and accurate diagnosis must be underscored, as delay in treatment may result in an undesirable increase in morbidity and/or mortality for both the patient and fetus. Advances in magnetic resonance imaging (MRI) through faster acquisition and motion-insensitive techniques, coupled with increased awareness and education regarding the value of MRI in diagnosing a wide range of pathology, have established MRI as a valuable strategy in the investigation of acute abdominal and pelvic pain in the pregnant patient. This review presents a practical approach to common obstetric and nonobstetric causes of acute abdominal and pelvic pain during pregnancy, as well as safety considerations for performing MRI in this patient population.

Utility of magnetic resonance imaging for suspected appendicitis in pregnant women

OBJECTIVE

The purpose of this study was to estimate the rate and risk of appendix nonvisualization and alternative diagnoses made with magnetic resonance imaging (MRI) for suspected appendicitis in pregnant women.

STUDY DESIGN

We performed a retrospective cohort study of consecutive pregnant women who underwent MRI for suspected appendicitis at a single center from 2007-2012. Data on clinical presentation, imaging, and surgical pathologic evidence were extracted from electronic medical records. Odds ratios estimated risk factors for nondiagnosis. Radiologic diagnoses were identified, and rates of diagnoses were calculated. Subgroup analysis was performed among women who underwent initial imaging with ultrasound scanning.

RESULTS

Over the 5-year period, 171 pregnant women underwent MRI for suspected appendicitis. The rate of nonvisualization was 30.9% (n = 53). Of the remaining 118 women with a visualized appendix, 18 women had imaging findings that were consistent with appendicitis and underwent appendectomy. Twelve cases of appendicitis were confirmed on pathologic evaluation (66.7%). Women with nonvisualization of the appendix on MRI were more likely to be beyond the first trimester (odds ratio, 2.1; 95% confidence interval, 1.0-4.5). Seventy-four women had disease diagnosed on MRI (43.3%). In the group of 43 women who had a nondiagnostic ultrasound scanning before the MRI, the rate of subsequent diagnostic MRI was 65% (n = 28).

CONCLUSION

MRI yields a high diagnostic rate and accuracy in pregnant women with suspected appendicitis and provides alternative diagnoses to guide further management. Given the high rate of appendix nonvisualization on ultrasound scanning that has been reported in the literature, we recommend MRI as the imaging modality of choice for this population in settings in which MRI is readily available.

The history of imaging in obstetrics

During the past century, imaging of the pregnant patient has been performed with radiography, scintigraphy, computed tomography, magnetic resonance imaging, and ultrasonography (US). US imaging has emerged as the primary imaging modality, because it provides real-time images at relatively low cost without the use of ionizing radiation. This review begins with a discussion of the history and current status of imaging modalities other than US for the pregnant patient. The discussion then turns to an in-depth description of how US technology advanced to become such a valuable diagnostic tool in the obstetric patient. Finally, the broad range of diagnostic uses of US in these patients is presented, including its uses for distinguishing an intrauterine pregnancy from a failed or ectopic pregnancy in the first trimester; assigning gestational age and assessing fetal weight; evaluating the fetus for anomalies and aneuploidy; examining the uterus, cervix, placenta, and amniotic fluid; and guiding obstetric interventional procedures.

MR imaging evaluation of abdominal pain during pregnancy: appendicitis and other nonobstetric causes

Clinical diagnosis of the cause of abdominal pain in a pregnant patient is particularly difficult because of multiple confounding factors related to normal pregnancy. Magnetic resonance (MR) imaging is useful in evaluation of abdominal pain during pregnancy, as it offers the benefit of cross-sectional imaging without ionizing radiation or evidence of harmful effects to the fetus. MR imaging is often performed specifically for diagnosis of possible appendicitis, which is the most common illness necessitating emergency surgery in pregnant patients. However, it is important to look for pathologic processes outside the appendix that may be an alternative source of abdominal pain. Numerous entities other than appendicitis can cause abdominal pain during pregnancy, including processes of gastrointestinal, hepatobiliary, genitourinary, vascular, and gynecologic origin. MR imaging is useful in diagnosing the cause of abdominal pain in a pregnant patient because of its ability to safely demonstrate a wide range of pathologic conditions in the abdomen and pelvis beyond appendicitis.

Imaging acute appendicitis: state of the art

The goal of this review is to present the state of the art in imaging tests for the diagnosis of acute appendicitis. Relevant publications regarding performance and advantages/disadvantages of imaging modalities for the diagnosis of appendicitis in different clinical situations were reviewed. Articles were extracted from a computerized database (MEDLINE) with the following activated limits: Humans, English, core clinical journals, and published in the last five years. Reference lists of relevant studies were checked manually to identify additional, related articles. Ultrasound (US) examination should be the first imaging test performed, particularly among the pediatric and young adult populations, who represent the main targets for appendicitis, as well as in pregnant patients. A positive US examination for appendicitis or an alternative diagnosis of possible gastrointestinal or urological origin, or a negative US, either showing a normal appendix or presenting low clinical suspicion of appendicitis, should lead to a final diagnosis. A negative or indeterminate examination with a strong clinical suspicion of appendicitis should be followed by a computed tomography (CT) scan or alternatively, a magnetic resonanace imaging (MRI) scan in a pregnant patient. A second US examination in a patient with persistent symptoms, especially if the first one was performed by a less experienced imaging professional, is a valid alternative to a CT.

Unenhanced MR Imaging in adults with clinically suspected acute appendicitis

PURPOSE

The purpose of the study was to evaluate unenhanced Magnetic Resonance Imaging (MRI) for the diagnosis of appendicitis or another surgery-requiring condition in an adult population scheduled for emergency appendectomy based on a clinical diagnosis of suspected acute appendicitis.

MATERIALS AND METHODS

The prospective study included 48 consecutive patients (29 female, 19 male, 18-70 years old, mean age=37.1 years). MRI examination was designed to be comfortable and fast; no contrast was administered. The sequences were performed during quiet respiration. The MRI findings were reviewed by two radiologists and one surgeon independent of each other and compared with surgical and pathological records.

RESULTS

According to the surgical and histopathological findings 30 of 48 patients (63%) had acute appendicitis. Of the remaining 18 patients, 4 patients had no reasons for the clinical symptoms and 14 patients had other pathology. For the three reviewers the performance of MRI in the diagnosis of acute appendicitis showed the following sensitivity, specificity and accuracy ranges: 83-93%, 50-83% and 77-83%. Moderate (κ=0.51) and fair (κ=0.31) interobserver agreements in the MR diagnosis of acute appendicitis were found between the reviewers. Sensitivity, specificity and accuracy values for overall performance of MRI in detecting pelvic abnormalities were 100%, 75% (3 of 4 healthy patients were identified by MRI) and 98%, respectively.

CONCLUSION

Unenhanced fast MRI is feasible as an additional fast screening before the appendectomy. It may prevent unnecessary surgeries. The fast MRI examination can be adequately performed on an MRI unit of broad range of field strengths.

Suspected appendicitis in the pregnant patient

ABSTRACT Appendicitis is the most common nonobstetric cause of abdominal pain in pregnancy. Pregnant patients may present with an atypical examination, thereby challenging clinicians. National specialty organizations recommend that nonionizing imaging options be pursued to aid in early diagnosis. Multiple studies suggest that magnetic resonance imaging technology is a safe and accurate alternative to ionizing imaging such as X-ray or computerized tomography imaging. A standard protocol that incorporates magnetic resonance imaging technology in the evaluation of the pregnant patient is proposed.