Hemodialysis Access: US for Preprocedural Mapping and Evaluation of Maturity and Access Dysfunction.

Patients with kidney failure require kidney replacement therapy. While renal transplantation remains the treatment of choice for kidney failure, renal replacement therapy with hemodialysis may be required owing to the limited availability and length of time patients may wait for allografts or for patients ineligible for transplant owing to advanced age or comorbidities. The ideal hemodialysis access should provide complication-free dialysis by creating a direct connection between an artery and vein with adequate blood flow that can be reliably and easily accessed percutaneously several times a week. Surgical arteriovenous fistulas and grafts are commonly created for hemodialysis access, with newer techniques that involve the use of minimally invasive endovascular approaches. The emphasis on proactive planning for the placement, protection, and preservation of the next vascular access before the current one fails has increased the use of US for preoperative mapping and monitoring of complications for potential interventions. Preoperative US of the extremity vasculature helps assess anatomic suitability before vascular access creation, increasing the rates of successful maturation. A US mapping protocol ensures reliable measurements and clear communication of anatomic variants that may alter surgical planning. Postoperative imaging helps assess fistula maturation before cannulation for dialysis and evaluates for early and late complications associated with arteriovenous access. Clinical and US findings can suggest developing stenosis that may progress to thrombosis and loss of access function, which can be treated with percutaneous vascular interventions to preserve access patency. Vascular access steal, aneurysms and pseudoaneurysms, and fluid collections are other complications amenable to US evaluation. ©RSNA, 2023 Supplemental material is available for this article. Test Your Knowledge questions for this article are available through the Online Learning Center.

Contrast-enhanced US Evaluation of Endoleaks after Endovascular Stent Repair of Abdominal Aortic Aneurysm.

Ruptured abdominal aortic aneurysm (AAA) carries high morbidity and mortality. Elective repair of AAA with endovascular stent-grafts requires lifetime imaging surveillance for potential complications, most commonly endoleaks. Because endoleaks result in antegrade or retrograde systemic arterialized flow into the excluded aneurysm sac, patients are at risk for recurrent aneurysm sac growth with the potential to rupture. Multiphasic CT has been the main imaging modality for surveillance and symptom evaluation, but contrast-enhanced US (CEUS) offers a useful alternative that avoids radiation and iodinated contrast material. CEUS is at least equivalent to CT for detecting endoleak and may be more sensitive. The authors provide a general protocol and technical considerations needed to perform CEUS of the abdominal aorta after endovascular stent repair. When there are no complications, the stent-graft lumen has homogeneous enhancement, and no contrast material is present in the aneurysm sac outside the stented lumen. In patients with an antegrade endoleak, contrast material is seen simultaneously in the aneurysm sac and stent-graft lumen, while delayed enhancement in the sac is due to retrograde leak. Recognition of artifacts and other potential pitfalls for CEUS studies is important for examination performance and interpretation. Online supplemental material is available for this article. ©RSNA, 2022.

Through thick and thin: a pictorial review of the endometrium.

The purpose of this pictorial review is to describe the normal appearance of the endometrium and to provide radiologists with an overview of endometrial pathology utilizing case examples. The normal appearance of the endometrium varies by age, menstrual phase, and hormonal status with differing degrees of acceptable endometrial thickness. Endometrial pathology most often manifests as either focal or diffuse endometrial thickening, and patients frequently present with abnormal vaginal bleeding. Endovaginal ultrasound (US) is the first-line modality for imaging the endometrium. This article will discuss the endometrial measurements used to direct management and workup of symptomatic patients and will discuss when additional imaging may be appropriate. Three-dimensional US is complementary to two-dimensional ultrasound and can be used as a problem-solving technique. Saline-infused sonohysterogram is a useful adjunct to delineate and detect focal intracavitary abnormalities, such as polyps and submucosal fibroids. Magnetic resonance imaging is the preferred imaging modality for staging endometrial cancer because it best depicts the depth of myometrial invasion and cervical stromal involvement. Unique imaging features and complications of endometrial ablation will be introduced. At the completion of this article, the reader will understand the spectrum of normal endometrial findings and will understand the workup of common endometrial pathology.

Effect of Direct Marketing for Uterine Artery Embolization on Rates of Leiomyomas, Incidental Findings, and Management After Pelvic MRI.

PURPOSE: The aim of this study was to determine whether a self-referred population screened by an interventional radiology (IR) clinic and a non-IR, physician-referred population differed with regard to suitability for uterine artery embolization (UAE) for symptomatic leiomyomas on the basis of preprocedure MRI. METHODS: This was an institutional review board-approved, HIPAA-compliant retrospective study of 301 women evaluated in an IR clinic for possible UAE from January 2009 to September 2012. Subjects were retrospectively divided into two groups: self-referred via direct marketing (group A, n = 203; mean age, 41.8 years; range, 22-58 years) and physician referred (group B, n = 98; mean age, 42.9 years; range, 30-65 years). RESULTS: There was no significant difference between groups in presenting symptoms (multiple symptoms, bleeding, bulk-related symptoms, pain). After initial screening, 73.4% of group A (149 of 203) and 79.6% of group B (78 of 98) underwent MRI (P = .242). On the basis of MRI findings, 91.3% of group A (136 of 149) and 94.9% of group B (74 of 78) had uterine leiomyomas (P = .328). Adenomyosis without leiomyoma was present in 4.0% of group A (6 of 149) and 3.8% of group B (3 of 78) (P = .947). Incidental findings requiring further clinical or imaging evaluation were found in 20.8% of group A (31 of 149) and 24.4% of group B (19 of 78) (P = .539). After MRI, 41.6% of group A (62 of 149) and 48.7% of group B (38 of 78) proceeded to UAE (P = .306). CONCLUSIONS: After initial screening, similar proportions of self-referred and physician-referred patients were candidates for UAE. The rates of confirmed leiomyomas and incidental findings on MRI were similar between groups.

In-phase signal intensity loss in solid renal masses on dual-echo gradient-echo MRI: association with malignancy and pathologic classification.

OBJECTIVE: The purposes of this study were to determine the prevalence of in-phase signal intensity loss on dual-echo gradient-echo MRI in solid renal masses using visual and quantitative techniques and to test for any association between in-phase signal intensity loss and pathologic classification. MATERIALS AND METHODS: The renal MRI studies of 177 patients (192 solid masses consisting of 166 renal cell carcinomas [RCCs], four malignant non-RCCs, and 22 benign tumors) were qualitatively reviewed by two blinded readers for visual evidence of relative in-phase signal intensity loss. For lesions without visual evidence, whole-lesion ROIs were used to attempt quantification of subtle signal intensity loss between opposed- and in-phase images (signal intensity loss index). RESULTS: Visual in-phase signal intensity loss was noted in 18% of clear cell RCC, 42% of papillary RCC, and no benign lesions. There was significant correlation between malignancy and visual signal intensity loss (Fisher exact test, p = 0.0092). Visual signal intensity loss was predictive of papillary RCC over clear cell RCC (odds ratio, 5.79; p = 0.0002) in logistic regression analysis of all RCCs, controlling for size. Quantitative assessment of remaining lesions provided no additional diagnostic benefit. CONCLUSION: Visible in-phase signal intensity loss is relatively common within solid renal masses and was associated with RCC and particularly papillary RCC (among all RCCs) in our population. Quantitative analysis in lesions without visible signal intensity loss was not predictive of RCC. Further work should be performed to validate the usefulness of this additional imaging parameter to help characterize renal masses and to determine the impact of this finding on imaging techniques potentially sensitive to susceptibility effects.

Magnetic resonance urography update--are we there yet?

Magnetic resonance (MR) urography, in conjunction with traditional MR imaging sequences, offers the potential for a comprehensive evaluation of the entire urinary tract. In addition to defining anatomic form, MR imaging excels at tissue differentiation and can estimate renal function. Most importantly, this information can be obtained without ionizing radiation or iodinated contrast media. Therefore, MR urography has become of particular interest in certain populations, including children, pregnant women, and renal transplant donors and recipients. Despite the challenges inherent in imaging a dynamic system with often subtle abnormalities, recent advances in MR technology and field strength, coupled with expanding functional capabilities, promise a bright future for MR urography.