Imaging of Antepartum and Postpartum Hemorrhage.

Severe obstetric hemorrhage is a leading cause of maternal mortality and morbidity worldwide. Major hemorrhage in the antepartum period presents potential risks for both the mother and the fetus. Similarly, postpartum hemorrhage (PPH) accounts for up to a quarter of maternal deaths worldwide. Potential causes of severe antepartum hemorrhage that radiologists should be familiar with include placental abruption, placenta previa, placenta accreta spectrum disorders, and vasa previa. Common causes of PPH that the authors discuss include uterine atony, puerperal genital hematomas, uterine rupture and dehiscence, retained products of conception, and vascular anomalies. Bleeding complications unique to or most frequently encountered after cesarean delivery are also enumerated, including entities such as bladder flap hematomas, rectus sheath and subfascial hemorrhage, and infectious complications of endometritis and uterine dehiscence. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Javitt and Madrazo in this issue.

Gastrointestinal malignancies in pregnancy.

Gastrointestinal malignancies, though uncommon in pregnancy, present several unique challenges with regards to diagnosis, staging, and treatment. Imaging the pregnant patient with a suspected or confirmed GI malignancy requires modifications to the radiologic modality of choice and protocol in order to minimize harm to the fetus, ensure accuracy in diagnosis and staging and guide treatment decisions. In this review article, we discuss the imaging approach to the pregnant patient with GI cancer, including safe radiologic modalities and modifications to imaging protocols. We also review the most common GI cancers encountered in pregnancy, including colorectal, pancreatic, gastric, and small bowel tumors, with emphasis to imaging findings, staging, and treatment considerations.

How to perform shear wave elastography. Part I.

We recently introduced a series of papers describing how to do certain techniques. This article is the first part of a review of shear wave elastography (SWE). It reports the principles and interpretation of the technique and describes how to optimize it. Normal values, pitfalls and artefacts for the examination of liver, breast. thyroid and salivary gland with shear wave elastography are presented. The manuscript provides specific tips for applying SWE as part of a diagnostic US examination.

How to perform shear wave elastography. Part II.

Recently a series of papers was introduced describing on "how to do" certain techniques. More specifically we published on how to perform strain imaging using the transcutaneous and endoscopic ultrasound approach and shear wave elastography (SWE). In the first part we describe how to optimize the examination technique, discussing normal values, pitfalls, artefacts and specific tips for applying SWE to specific organs (liver, breast, thyroid, salivary glands) as part of a diagnostic US examination. In part II, the use of SWE in the pancreas, spleen, kidney, prostate, scrotum, musculoskeletal system, lymph nodes and future developments are discussed.

Virtual Unenhanced Dual-Energy CT Images Obtained with a Multimaterial Decomposition Algorithm: Diagnostic Value for Renal Mass and Urinary Stone Evaluation.

Background Virtual unenhanced (VUE) images obtained by using a dual-energy CT (DECT) multimaterial decomposition algorithm hold promise for diagnostic use in the abdomen in lieu of true unenhanced (TUE) images. Purpose To assess VUE images obtained from a DECT multimaterial decomposition algorithm in patients undergoing renal mass and urinary stone evaluation. Materials and Methods In this retrospective Health Insurance Portability and Accountability Act-compliant study, DECT was performed in patients undergoing evaluation for renal mass or urinary stone. VUE images were compared quantitatively to TUE images and qualitatively assessed by four independent radiologists. Differences in attenuation between VUE and TUE images were summarized by using 95% limits of agreement. Diagnostic performance in urinary stone detection was summarized by using area under the receiver operating characteristic curve, sensitivity, and specificity. Results A total of 221 patients (mean age ± standard deviation, 61 years ± 14; 129 men) with 273 renal masses were evaluated. Differences in renal mass attenuation between VUE and TUE images were within 3 HU for both enhancing masses (95% limits of agreement, -3.1 HU to 2.7 HU) and nonenhancing cysts (95% limits of agreement, -2.9 HU to 2.5 HU). Renal mass classification as enhancing mass versus nonenhancing cyst did not change (reclassification rate of enhancing masses, 0% [0 of 78]; 95% CI: 0, 5; reclassification rate of nonenhancing cysts, 0% [0 of 193]; 95% CI: 0, 2) with use of VUE in lieu of TUE images. Among 166 urinary stones evaluated, diagnostic performance of VUE images for stone detection was lower compared with that of TUE images (area under the receiver operating characteristic curve, 0.79 [95% CI: 0.73, 0.84] vs 0.93 [95% CI: 0.91, 0.95]; P < .001) due to reduced sensitivity of VUE for detection of stones 3 mm in diameter or less compared with those greater than 3 mm (sensitivity, 23% [25 of 108; 95% CI: 12, 40] vs 88% [126 of 144; 95% CI: 77, 94]; P < .001). Conclusion Compared with true unenhanced images, virtual unenhanced (VUE) images were unlikely to change renal mass classification as enhancing mass versus nonenhancing cyst. Diagnostic performance of VUE images remained suboptimal for urinary stone detection due to subtraction of stones 3 mm or less in diameter. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Sosna in this issue.

Differential outcomes of patients with thyroid FNA diagnoses of AUS/FLUS with and without nuclear atypia: The potential need for separation in the Bethesda System.

BACKGROUND: In the current version of The Bethesda System (TBS) for thyroid cytopathology, the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category has an estimated risk of malignancy of 10% to 30%. Diagnostic criteria include presence of nuclear atypia, suggestive of papillary thyroid carcinoma (PTC), as well as other types of atypia, which can be seen with non-malignant entities. Aim of this study was to investigate differential outcomes of AUS/FLUS, based on specific morphologic criteria, and assess their respective malignancy risks. METHODS: From a total of 1233 patients undergoing thyroid FNAs between 2010 and 2014 at the University of Washington, 119 had AUS/FLUS without nuclear atypia, and 64 with nuclear atypia. Outcomes for patients with and without nuclear atypia (with the exception of 24 patients lost to follow-up) were evaluated and results were compared. RESULTS: 16/57 (28.1%) patients with AUS/FLUS and nuclear atypia subsequently had carcinomas on thyroidectomy, statistically higher than the 8/102 patients (7.8%, P = .001) without nuclear atypia. When comparing only patients who underwent surgery (n = 63), again those with AUS/FLUS and nuclear atypia had statistically higher rates of carcinoma (16/31, 51.6%), compared to those without (8/32, 25%; P = .0394). Overall, 24/159 (15.1%) of patients with AUS/FLUS had carcinoma on subsequent histology. CONCLUSION: Malignancy rates for AUS/FLUS were in line with TBS estimated risks. However, our data demonstrate that the presence or absence of nuclear atypia is associated with different malignancy rates, suggesting the possibility that the AUS/FLUS category may best be split into two subcategories with different implied risks of malignancy.

Imaging of transgender patients: expected findings and complications of gender reassignment therapy.

OBJECTIVES: Gender dysphoria is defined as a conflict between the biological gender and the gender with which the person identifies. Gender reassignment therapy can alter external sexual features to resemble those of the desired gender and are broadly classified into two types, female to male (FTM) and male to female (MTF). In this paper we describe expected findings and complications of gender reassignment therapy. METHODS: Collaborative multi-institutional project supported by Ovarian and Uterine Cancer Disease Focused panel of Society of Abdominal Radiology. RESULTS: Gender dysphoria is defined as a conflict between the biological gender and the gender with which the person identifies. Gender reassignment therapy can alter external sexual features to resemble those of the desired gender and are broadly classified into two types, female to male (FTM) and male to female (MTF). These therapies include hormonal treatment as well as surgical procedures. FTM genital reconstructive therapy includes creation of a neophallus, which can be achieved by metoidioplasty or phalloplasty with mastectomy, along with testosterone administration. MTF gender reassignment surgery includes complete removal of external genitalia with penectomy and orchiectomy, with vaginoplasty, clitoroplasty, labiaplasty, and breast augmentation along with estrogen supplements. CONCLUSION: Surgical techniques alter the standard anatomy and make imaging interpretation challenging if radiologists are unfamiliar with expected post-operative appearances. It is important to recognize the complications related to surgical and non-surgical treatment of gender dysphoria to avoid interpretation errors. Furthermore, increasing the prevalence of transgender patients requires increased sensitivity when interpreting imaging studies to reduce the potential for misdiagnoses in reporting due to frequently incomplete available clinical history.

Inter-observer Variability in the American College of Radiology Thyroid Imaging Reporting and Data System: In-Depth Analysis and Areas for Improvement.

The American College of Radiology (ACR) introduced a new standardized system for management of thyroid nodules, the Thyroid Imaging Reporting and Data System (TI-RADS). The purpose of this retrospective study is to evaluate the inter-observer variability in applying TI-RADS in clinical practice without prior dedicated training. We evaluated a total of 180 nodules constituting all consecutive thyroid aspirations performed in the radiology department between January 1, 2014 and June 30, 2014, with exclusion of histologically inadequate samples. Four radiologists, blinded to each other's evaluation and to final pathology results, evaluated all of the nodules based on the TI-RADS lexicon. TI-RADS score and management recommendations were then deduced from the inputted features. Statistical analysis was performed to determine inter-observer agreement among all readers, as well as between each two readers, in all TI-RADS sonographic features and for recommended management per TI-RADS score with multi-user Cohen's κ (Light's κ) and percentage agreement using R. There was fair-to-moderate inter-observer agreement in nodule composition (two-reader κ range: 0.327-0.533) and presence of calcifications (κ range: 0.229-0.527), but poor-to-fair agreement in echogenicity (κ range: 0.141-0.355), shape (κ range: 0.0729-0.513) and margins (κ range: 0.176-0.283). There was fair inter-observer agreement regarding management recommendations (κ range: 0.242-0.359).

Placental abruption and hemorrhage-review of imaging appearance.

Placental and periplacental bleeding are common etiologies for antepartum bleeding. Placental abruption complicates approximately 1% of pregnancies and is associated with increased maternal, fetal, and neonatal morbidity and mortality. This article reviews the normal placental appearance on ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) and then discusses the different morphological appearance of placental and periplacental hematomas along with their mimics. Hematomas are classified based on the location as retroplacental, marginal subchorionic, preplacental (subamniotic), or intraplacental. Placenta-related bleeding is a common finding during first trimester ultrasound and its detection can help triage the pregnant females into low- and high-risk groups. This article reviews placenta related bleeding in the setting of trauma. Trauma can complicate pregnancy with potential severe maternal and fetal outcomes. CT is usually performed as part of the trauma workup and it can be challenging for placental evaluation. MRI can characterize the age of the hematomas and can differentiate hematomas from tumors.

B-Flow imaging of the placenta: A feasibility study.

B-Flow imaging directly displays the flowing intravascular echoes during real-time gray-scale ultrasound without using Doppler techniques. The objective of our study was to evaluate the feasibility of B-Flow imaging in the placenta and to evaluate the artifacts seen on B-Flow imaging. After IRB approval, 36 women (17 normal and 19 high risk women) were enrolled in our study. B-Flow images were acquired on GE LOGIC E9 machine. Retrospective analysis of the B-Flow and cine capture images was performed for artifacts and for vessels visualized. Pregnant women enrolled in the study ranged from 19 to 43 years of age with an average age of 31.7 years. Gestational age varied from 17 weeks and five days to 36 weeks and three days with an average of 26 weeks and three days. From a total of 161 B-Flow images reviewed by one researcher, 15 images were acceptable with no evidence of artifact. The remainder of the images had some artifact in them. For the 36 women with color Doppler and B-Flow images reviewed by the two independent blinded reviewers, a total of 144 reads were obtained. More small horizontal (p = 0.046) and small vertical running vessels (p < 0.001) were identified with B-Flow than color Doppler images. B-Flow is capable of showing perfusion in a human placenta; however, recognizing artifacts and modifying the image acquisition to reduce artifacts is necessary with this new technique to acquire the best images for interpretation.

CT Detectability of Small Low-Contrast Hypoattenuating Focal Lesions: Iterative Reconstructions versus Filtered Back Projection.

Purpose To investigate performance in detectability of small (≤1 cm) low-contrast hypoattenuating focal lesions by using filtered back projection (FBP) and iterative reconstruction (IR) algorithms from two major CT vendors across a range of 11 radiation exposures. Materials and Methods A low-contrast detectability phantom consisting of 21 low-contrast hypoattenuating focal objects (seven sizes between 2.4 and 10.0 mm, three contrast levels) embedded into a liver-equivalent background was scanned at 11 radiation exposures (volume CT dose index range, 0.5-18.0 mGy; size-specific dose estimate [SSDE] range, 0.8-30.6 mGy) with four high-end CT platforms. Data sets were reconstructed by using FBP and varied strengths of image-based, model-based, and hybrid IRs. Sixteen observers evaluated all data sets for lesion detectability by using a two-alternative-forced-choice (2AFC) paradigm. Diagnostic performances were evaluated by calculating area under the receiver operating characteristic curve (AUC) and by performing noninferiority analyses. Results At benchmark exposure, FBP yielded a mean AUC of 0.79 ± 0.09 (standard deviation) across all platforms which, on average, was approximately 2% lower than that observed with the different IR algorithms, which showed an average AUC of 0.81 ± 0.09 (P = .12). Radiation decreases of 30%, 50%, and 80% resulted in similar declines of observer detectability with FBP (mean AUC decrease, -0.02 ± 0.05, -0.03 ± 0.05, and -0.05 ± 0.05, respectively) and all IR methods investigated (mean AUC decrease, -0.00 ± 0.05, -0.04 ± 0.05, and -0.04 ± 0.05, respectively). For each radiation level and CT platform, variance in performance across observers was greater than that across reconstruction algorithms (P = .03). Conclusion Iterative reconstruction algorithms have limited radiation optimization potential in detectability of small low-contrast hypoattenuating focal lesions. This task may be further complicated by a high degree of variation in radiologists' performances, seemingly exceeding real performance differences among reconstruction algorithms. © RSNA, 2018 Online supplemental material is available for this article.

Femur-sparing pattern of abnormal fetal growth in pregnant women from New York City after maternal Zika virus infection.

BACKGROUND: Zika virus is a mosquito-transmitted flavivirus, which can induce fetal brain injury and growth restriction following maternal infection during pregnancy. Prenatal diagnosis of Zika virus-associated fetal injury in the absence of microcephaly is challenging due to an incomplete understanding of how maternal Zika virus infection affects fetal growth and the use of different sonographic reference standards around the world. We hypothesized that skeletal growth is unaffected by Zika virus infection and that the femur length can represent an internal standard to detect growth deceleration of the fetal head and/or abdomen by ultrasound. OBJECTIVE: We sought to determine if maternal Zika virus infection is associated with a femur-sparing pattern of intrauterine growth restriction through analysis of fetal biometric measures and/or body ratios using the 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project and World Health Organization Fetal Growth Chart sonographic references. STUDY DESIGN: Pregnant women diagnosed with a possible recent Zika virus infection at Columbia University Medical Center after traveling to an endemic area were retrospectively identified and included if a fetal ultrasound was performed. Data were collected regarding Zika virus testing, fetal biometry, pregnancy, and neonatal outcomes. The 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project and World Health Organization Fetal Growth Chart sonographic standards were applied to obtain Z-scores and/or percentiles for fetal head circumference, abdominal circumference, and femur length specific for each gestational week. A novel 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project standard was also developed to generate Z-scores for fetal body ratios with respect to femur length (head circumference:femur length, abdominal circumference:femur length). Data were then grouped within clinically relevant gestational age strata (<24, 24-27 6/7, 28-33 6/7, >34 weeks) to analyze time-dependent effects of Zika virus infection on fetal size. Statistical analysis was performed using Wilcoxon signed-rank test on paired data, comparing either abdominal circumference or head circumference to femur length. RESULTS: A total of 56 pregnant women were included in the study with laboratory evidence of a confirmed or possible recent Zika virus infection. Based on the Centers for Disease Control and Prevention definition for microcephaly after congenital Zika virus exposure, microcephaly was diagnosed in 5% (3/56) by both the 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project and World Health Organization Fetal Growth Chart standards (head circumference Z-score ≤-2 or ≤2.3%). Using 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project, intrauterine fetal growth restriction was diagnosed in 18% of pregnancies (10/56; abdominal circumference Z-score ≤-1.3, <10%). Analysis of fetal size using the last ultrasound scan for all subjects revealed a significantly abnormal skewing of fetal biometrics with a smaller abdominal circumference vs femur length by either 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project or World Health Organization Fetal Growth Chart (P < .001 for both). A difference in distribution of fetal abdominal circumference compared to femur length was first apparent in the 24-27 6/7 week strata (2014 International Fetal and Newborn Growth Consortium for the 21st Century Project, P = .002; World Health Organization Fetal Growth Chart, P = .001). A significantly smaller head circumference compared to femur length was also observed by 2014 International Fetal and Newborn Growth Consortium for the 21st Century Project as early as the 28-33 6/7 week strata (2014 International Fetal and Newborn Growth Consortium for the 21st Century Project, P = .007). Overall, a femur-sparing pattern of growth restriction was detected in 52% of pregnancies with either head circumference:femur length or abdominal circumference:femur length fetal body ratio <10th percentile (2014 International Fetal and Newborn Growth Consortium for the 21st Century Project Z-score ≤-1.3). CONCLUSION: An unusual femur-sparing pattern of fetal growth restriction was detected in the majority of fetuses with congenital Zika virus exposure. Fetal body ratios may represent a more sensitive ultrasound biomarker to detect viral injury in nonmicrocephalic fetuses that could impart long-term risk for complications of congenital Zika virus infection.

Utility of diffusion-weighted MR imaging in the diagnosis of placenta accreta spectrum abnormality.

PURPOSE: The aim of this study was to evaluate the utility of added DWI sequences as an adjunct to traditional MR imaging in the evaluation of abnormal placentation in patients with suspicion for placenta accreta spectrum abnormality or morbidly adherent placenta (MAP). MATERIALS AND METHODS: The study was approved by local ethics committee. The subjects included pregnant women with prenatal MRI performed between July 2013 to July 2015. All imaging was performed on a Philips 1.5T MR scanner using pelvic phased-array coil. Only T2-weighted and diffusion-weighted imaging (DWI) series were compiled for review. Two randomized imaging sets were created: set 1 included T2-weighted series only (T2W); set 2 included T2W with DWI series together (T2W + DWI). Three radiologists, blinded to history and pathology, reviewed the imaging, with 2 weeks of time between the two image sets. Sensitivity, specificity, and overall accuracy for MAP were calculated and compared between T2W only and T2W + DWI reads. Associations between imaging findings and invasion on pathology were tested using the Chi-squared test. Confidence scores, inter-reader agreement, and systematic differences were documented. RESULTS: A total of 17 pregnant women were included in the study. 8 cases were pathologically diagnosed with MAP. There were no significant differences in the diagnostic accuracy between T2W and T2W + DWI in the diagnosis of MAP in terms of overall accuracy (62.7% for T2W vs. 68.6% for T2W + DWI, p = 0.68), sensitivity (70.8% for T2W vs. 95.8% for T2W + DWI, p = 0.12), and specificity (55.6% for T2W vs. 44.4% for T2W + DWI, p = 0.49). There was no significant difference in the diagnostic confidence between the review of T2W images alone and the T2W + DWI review (mean 7.3 ± 1.8 for T2W vs. 7.5 ± 1.8 for T2W + DWI, p = 0.37). CONCLUSION: With the current imaging technique, addition of DWI sequence to the traditional T2W images cannot be shown to significantly increase the accuracy or reader confidence for diagnosis of placenta accreta spectrum abnormality. However, DWI does improve identification of abnormalities in the placental-myometrial interface.

Congenital Zika virus infection as a silent pathology with loss of neurogenic output in the fetal brain.

Zika virus (ZIKV) is a flavivirus with teratogenic effects on fetal brain, but the spectrum of ZIKV-induced brain injury is unknown, particularly when ultrasound imaging is normal. In a pregnant pigtail macaque (Macaca nemestrina) model of ZIKV infection, we demonstrate that ZIKV-induced injury to fetal brain is substantial, even in the absence of microcephaly, and may be challenging to detect in a clinical setting. A common and subtle injury pattern was identified, including (i) periventricular T2-hyperintense foci and loss of fetal noncortical brain volume, (ii) injury to the ependymal epithelium with underlying gliosis and (iii) loss of late fetal neuronal progenitor cells in the subventricular zone (temporal cortex) and subgranular zone (dentate gyrus, hippocampus) with dysmorphic granule neuron patterning. Attenuation of fetal neurogenic output demonstrates potentially considerable teratogenic effects of congenital ZIKV infection even without microcephaly. Our findings suggest that all children exposed to ZIKV in utero should receive long-term monitoring for neurocognitive deficits, regardless of head size at birth.

Fetal Urinary Tract Anomalies: Review of Pathophysiology, Imaging, and Management.

OBJECTIVE: Common fetal anomalies of the kidneys and urinary tract encompass a complex spectrum of abnormalities that can be detected prenatally by ultrasound. Common fetal anomalies of the kidneys and urinary tract can affect amniotic fluid volume production with the development of oligohydramnios or anhydramnios, resulting in fetal pulmonary hypoplasia and, potentially, abnormal development of other fetal structures. CONCLUSION: We provide an overview of common fetal anomalies of the kidneys and urinary tract with an emphasis on sonographic patterns as well as pathologic and postnatal correlation, along with brief recommendations for postnatal management. Of note, we render an updated classification of fetal abnormalities of the kidneys and urinary tract based on the presence or absence of associated urinary tract dilation. In addition, we review the 2014 classification of urinary tract dilation based on the Linthicum multidisciplinary consensus panel.

The Sonographic Stenosis Index: A New Specific Quantitative Measure of Transplant Hepatic Arterial Stenosis.

OBJECTIVES: This study evaluates the sensitivity and specificity of stenosis index (SI), which accounts for the entire spectral Doppler waveform, to detect significant transplant hepatic arterial stenosis. MATERIALS AND METHODS: In this institutional review board-approved, HIPAA compliant study, we retrospectively analyzed 69 patients who had catheter angiography for suspected transplant hepatic arterial stenosis (THAS) between January 2006 and December 2010; all patients had Doppler ultrasound within 30 days before angiography. Patients with angiographic stenosis requiring intervention were considered positive for THAS. Stenosis index was calculated from each patient's spectral Doppler ultrasound images by obtaining the ratio of the area under the high-frequency signal to low-frequency signal in the spectral Doppler. Resistive index (RI) and pulsatility index (PI) were also calculated. Receiver operator curve analysis was performed and the area under the curve (AUC) was compared among the three metrics. RESULTS: Forty-eight of 69 patients had THAS by angiography requiring intervention; 21patients had no angiographic evidence of THAS. SI was significantly different (P < .001) between patients with THAS (SI = 1.04 ± 0.20) and those without THAS (SI = 1.39 ± 0.30). Stenosis index had an AUC of 0.86 for detecting THAS, which was significantly higher than that from RI (AUC = 0.68, P = .038 for the comparison) and PI (AUC = 0.70, P = .029). For SI < 1.35, the sensitivity for THAS was 94% and specificity was 52%. For RI < 0.5, the sensitivity was 96% and the specificity was 29%. CONCLUSIONS: Stenosis index is more accurate than the resistive index and the pulsatility index for detecting transplant hepatic artery stenosis.

Fetal brain lesions after subcutaneous inoculation of Zika virus in a pregnant nonhuman primate.

We describe the development of fetal brain lesions after Zika virus (ZIKV) inoculation in a pregnant pigtail macaque. Periventricular lesions developed within 10 d and evolved asymmetrically in the occipital-parietal lobes. Fetal autopsy revealed ZIKV in the brain and significant cerebral white matter hypoplasia, periventricular white matter gliosis, and axonal and ependymal injury. Our observation of ZIKV-associated fetal brain lesions in a nonhuman primate provides a model for therapeutic evaluation.

Multimodality approach for imaging of non-traumatic acute abdominal emergencies.

"Acute abdomen" includes spectrum of medical and surgical conditions ranging from a less severe to life-threatening conditions in a patient presenting with severe abdominal pain that develops over a period of hours. Accurate and rapid diagnosis of these conditions helps in reducing related complications. Clinical assessment is often difficult due to availability of over-the-counter analgesics, leading to less specific physical findings. The key clinical decision is to determine whether surgical intervention is required. Laboratory and conventional radiographic findings are often non-specific. Thus, cross-sectional imaging plays a pivotal role for helping direct management of acute abdomen. Computed tomography is the primary imaging modality used for these cases due to fast image acquisition, although US is more specific for conditions such as acute cholecystitis. Magnetic resonance imaging or ultrasound is very helpful in patients who are particularly sensitive to radiation exposure, such as pregnant women and pediatric patients. In addition, MRI is an excellent problem-solving modality in certain conditions such as assessment for choledocholithiasis in patients with right upper quadrant pain. In this review, we discuss a multimodality approach for the usual causes of non-traumatic acute abdomen including acute appendicitis, diverticulitis, cholecystitis, and small bowel obstruction. A brief review of other relatively less frequent but important causes of acute abdomen, such as perforated viscus and bowel ischemia, is also included.