The Capabilities and Limitations of Clinical Magnetic Resonance Imaging for Detecting Kidney Stones: A Retrospective Study.

The purpose of this work was to investigate the performance of currently available magnetic resonance imaging (MRI) for detecting kidney stones, compared to computed tomography (CT) results, and to determine the characteristics of successfully detected stones. Patients who had undergone both abdominal/pelvic CT and MRI exams within 30 days were studied. The images were reviewed by two expert radiologists blinded to the patients' respective radiological diagnoses. The study consisted of four steps: (1) reviewing the MRI images and determining whether any kidney stone(s) are identified; (2) reviewing the corresponding CT images and confirming whether kidney stones are identified; (3) reviewing the MRI images a second time, armed with the information from the corresponding CT, noting whether any kidney stones are positively identified that were previously missed; (4) for all stones MRI-confirmed on previous steps, the radiologist experts being asked to answer whether in retrospect, with knowledge of size and location on corresponding CT, these stones would be affirmed as confidently identified on MRI or not. In this best-case scenario involving knowledge of stones and their locations on concurrent CT, radiologist experts detected 19% of kidney stones on MRI, with stone size being a major factor for stone identification.

Safety and technique of ferumoxytol administration for MRI.

Ferumoxytol is an ultrasmall superparamagnetic iron oxide agent marketed for the treatment of anemia. There has been increasing interest in its properties as an MRI contrast agent as well as greater awareness of its adverse event profile. This mini-review summarizes the current state of knowledge of the risks of ferumoxytol and methods of administration.

Association Between Advances in High-Resolution Cross-Section Imaging Technologies and Increase in Prevalence of Pancreatic Cysts From 2005 to 2014.

BACKGROUND & AIMS: Increasingly, pancreatic cysts are discovered incidentally in patients undergoing cross-sectional imaging for nonpancreatic reasons. It is unclear whether this increase is caused by improved detection by progressively more sophisticated cross-sectional imaging techniques or by a true increase in prevalence. We aimed to determine the prevalence of incidental pancreatic cysts in patients undergoing magnetic resonance imaging (MRI) for nonpancreatic indications on successive, increasingly sophisticated MRI systems. Also, we compared prevalence based on the demographic characteristics of the patients. METHODS: We collected data from MRIs performed at the Mayo Clinic in Florida during the sample months of January and February, from 2005 to 2014. Each patient's clinical chart was reviewed in chronological order to include the first 50 MRIs of each year (500 total). Patients were excluded if they had pancreatic disease including cysts, pancreatic surgery, pancreatic symptoms, pancreatic indication for the imaging study, or previous abdominal MRIs. An expert pancreatic MRI radiologist reviewed each image, looking for incidental pancreatic cysts. RESULTS: Of the 500 patients analyzed, 208 patients (41.6%) were found to have an incidental cyst. A significant relationship was observed between pancreatic cysts and patient age (P < .0001), diabetes mellitus (P = .001), and nonpancreatic cancer (P = .01), specifically nonmelanoma skin cancer (P = .03) or hepatocellular carcinoma (P = .02). The multivariable model showed a strong association between hardware and software versions and detection of cysts (P < .0001); the old hardware detected pancreatic cysts in 30.3% of patients, whereas the newest hardware detected cysts in 56.3% of patients. CONCLUSIONS: Based on an analysis of data collected from 2005 through 2014, newer versions of MRI hardware and software corresponded with higher numbers of pancreatic cysts detected. Older age, diabetes, and the presence of nonpancreatic cancer (specifically nonmelanoma skin cancer and hepatocarcinoma) were also associated with the presence of cysts.

Detection of different kidney stone types: an ex vivo comparison of ultrashort echo time MRI to reference standard CT.

BACKGROUND AND PURPOSE: With the development of ultrashort echo time (UTE) sequences, it may now be possible to detect kidney stones by using magnetic resonance imaging (MRI). In this study, kidney stones of varying composition and sizes were imaged using both UTE MRI as well as the reference standard of computed tomography (CT), with different surrounding materials and scan setups. METHODS: One hundred and fourteen kidney stones were inserted into agarose and urine phantoms and imaged both on a dual-energy CT (DECT) scanner using a standard renal stone imaging protocol and on an MRI scanner using the UTE sequence with both head and body surface coils. A subset of the stones representing all composition types and sizes was then inserted into the collecting system of porcine kidneys and imaged in vitro with both CT and MRI. RESULTS: All of the stones were visible on both CT and MRI imaging. DECT was capable of differentiating between uric acid and nonuric acid stones. In MRI imaging, the choice of coil and large field of view (FOV) did not affect stone detection or image quality. The MRI images showed good visualization of the stones' shapes, and the stones' dimensions measured from MRI were in good agreement with the actual values (R(2)=0.886, 0.895, and 0.81 in the agarose phantom, urine phantom, and pig kidneys, respectively). The measured T2 relaxation times ranged from 4.2 to 7.5ms, but did not show significant differences among different stone composition types. CONCLUSIONS: UTE MRI compared favorably with the reference standard CT for imaging stones of different composition types and sizes using body surface coil and large FOV, which suggests potential usefulness of UTE MRI in imaging kidney stones in vivo.

Kidney stone imaging with 3D ultra-short echo time (UTE) magnetic resonance imaging. A phantom study.

Computed tomography (CT) is the current gold standard for imaging kidney stones, albeit at the cost of radiation exposure. Conventional magnetic resonance imaging (MRI) sequences are insensitive to detecting the stones because of their appearance as a signal void. With the development of 2D ultra-short echo-time (UTE) MRI sequences, it becomes possible to image kidney stones in vitro. In this work, we optimize and implement a modified 3D UTE MRI sequence for imaging kidney stones embedded in agarose phantoms mimicking the kidney tissue and in urine phantoms at 3.0T. The proposed technique is capable of imaging the stones with high spatial resolution in a short scan time.

Sclerosing variant of well-differentiated liposarcoma: relative prevalence and spectrum of CT and MRI features.

OBJECTIVE: The purpose of this study was to determine the relative prevalence of the sclerosing variant of well-differentiated liposarcoma at one institution and to elucidate the CT and MRI characteristics of this subtype of well-differentiated liposarcoma. MATERIALS AND METHODS: A retrospective computerized search was conducted to calculate the relative prevalence of the sclerosing variant of well-differentiated liposarcoma among all well-differentiated liposarcoma subtypes at one institution. The MRI and CT features of a total of 19 cases of pathologically proven sclerosing variant of well-differentiated liposarcoma were evaluated (seven identified from the study institution database and 12 cases contributed by other institutions). RESULTS: The cases of a total of 36 patients with well-differentiated liposarcoma were identified in the pathology database; six (17%) cases had evidence of dedifferentiation. Seven (19%) cases of sclerosing variant of well-differentiated liposarcoma were identified. Of these, three (43%) had evidence of dedifferentiation. On images, the sclerosing variant of well-differentiated liposarcoma typically presented as a large (average, 16.6 cm) well-circumscribed heterogeneous mass most commonly situated in the retroperitoneum (58%). Sixteen of the 19 tumors evaluated (84%) had predominantly well-circumscribed margins. Tumor composition ranged from predominantly fatty to entirely devoid of macroscopic fat; only three (16%) were composed of more than 75% fat. Variable amounts of nonlipomatous elements were identified in all cases. Enhancement of these elements was evident at CT or MRI in all 14 cases in which enhancement could be reliably assessed. CONCLUSION: The sclerosing variant of well-differentiated liposarcoma should be included in the differential diagnosis of any well-circumscribed lipomatous mass containing variable amounts of nonlipomatous elements, particularly when located in the retroperitoneum. Unlike other subtypes of well-differentiated liposarcoma, the sclerosing variant is less likely to be composed predominantly of fat and may be associated with an increased propensity for dedifferentiation.

Current developments and recent advances in musculoskeletal tumor imaging.

The radiologic evaluation of musculoskeletal masses has changed dramatically within recent years. This article addresses the current developments and recent advances in musculoskeletal tumor imaging. We include new MR imaging techniques to better define anatomy, especially in difficult to image areas such as the chest wall and abdomen; the use of chemical shift imaging to separate hematopoietic marrow from pathologic marrow infiltration; as well as the use of diffusion and spectroscopy to help distinguish benign and malignant processes. We also briefly address dual-energy computed tomography and positron emission tomography imaging. Our intention is not to provide a comprehensive review of imaging techniques but to offer an update and perspective on current technology.

Impact of neoadjuvant chemoradiation on the tumor burden before liver transplantation for unresectable cholangiocarcinoma.

The very early experience with liver transplantation (LT) for cholangiocarcinoma (CC) was dismal because of the poor survival outcomes and the high recurrence rates. However, LT for CC in conjunction with neoadjuvant chemoradiation recently has shown encouraging results, although the data are extremely limited. At our institution between 2001 and 2008, 22 CC patients underwent protocol orthotopic LT at a median age of 45 years (range = 24-63 years). At a median follow-up of 601.5 days (range = 111-1388 days), the median survival time of the cohort was 3.3 years. The 1-, 2-, and 3-year Kaplan-Meier survival probabilities were 90%, 70%, and 63%, respectively, whereas the historical 5-year survival rates were 0% to 18% for intrahepatic CC and 23% to 26% for extrahepatic CC when patients underwent transplantation without neoadjuvant therapy. These encouraging survival rates for patients with this type of tumor, which is difficult to diagnose and treat, are no less significant when they are compared to the national 1- and 3-year survival rates (86% and 68%, respectively) of patients undergoing deceased donor LT for malignant neoplasms of the liver (as reported by the United Network for Organ Sharing). In our series, disease recurrence was significantly associated with a larger residual tumor [6.3 versus 2.0 cm (mean values), P = 0.008] and with a shorter waiting time for LT after the chemoradiation protocol [18 versus 56 days (mean values), P = 0.04]. Our LT protocol for CC was found to be promising for patients with truly extrahepatic CC and for patients within stages I to IIB of the American Joint Committee on Cancer Staging system (100% survival at a median follow-up of 2.2 years), but the results were notably poor for patients with stage III extrahepatic CC (median survival = 1.2 years). These observations highlight the need for accurate preoperative staging of CC for ideal LT recipient selection and the importance of a low tumor burden and a longer wait after neoadjuvant therapy. More effective chemoradiation regimens for reducing the tumor burden and the appropriate timing of LT after neoadjuvant chemoradiation require further research.

Extrahepatic portal biliopathy: proposed etiology on the basis of anatomic and clinical features.

PURPOSE: To compare the anatomic and clinical features in patients with chronic portal vein thrombosis (PVT) to determine why some patients develop portal biliopathy (PB) while most do not and propose an etiology for PB. MATERIALS AND METHODS: This project satisfied HIPAA regulations and received institutional review board approval for a retrospective review without the need for consent. From 100 patients with PVT, 60 were extracted who had chronic, nonmalignant PVT, after exclusion of those with sclerosing cholangitis, liver transplants, choledocholithiasis, or portosystemic shunts. Clinical and imaging data from 19 patients with biliary dilatation (PB group) were compared with data from 41 patients without biliary dilatation (no-PB group). Statistical analysis was performed with the Fisher exact test for categorical variables or the Wilcoxon rank-sum test for numerical and ordered categorical variables. P values of .05 or less were considered to indicate a significant difference. RESULTS: The etiology of PVT differed between the groups (P < .001); cirrhosis was infrequently seen in the PB group (two of 19, 11%) but was common in the no-PB group (31 of 41, 76%). Only two of 33 (6%) patients with cirrhosis and PVT had PB. Extension of PVT into the mesenteric veins was significantly more common in the PB group (18 of 19, 95%) than in the no-PB group (one of 41, 2%) (P < .001). Compared with the no-PB group, patients in the PB group had more acute angulation of the bile duct (median, 110° vs 128°; P = .008), less frequent gastroesophageal varices (three of 19 [16%] vs 20 of 41 [49%], P = .021), and a smaller mean coronary vein diameter (median, 5 vs 6 mm; P = .014). CONCLUSION: Noncirrhotic patients with hypercoagulable states tend to develop PB when PVT extends to the splenomesenteric veins. A possible etiology is the formation of specific peribiliary venous pathways responsible for bile duct compression and tethering.

Large sample of nephrogenic systemic fibrosis cases from a single institution.

OBJECTIVES: To estimate and stratify the risk of development of nephrogenic systemic fibrosis (NSF) in well-defined at-risk subpopulations from a large single institution, and to perform a single-institution case series study of patients with biopsy-proven NSF. DESIGN: Retrospective cohort of patients exposed to gadolinium-based contrast agents (GBCAs) at a single institution during an 8-year period (January 1, 1999, to December 31, 2006), and a case series study of patients with biopsy-proven NSF. SETTING: A primary, secondary, and tertiary health care center that treated more than 2.2 million outpatients and had 135 000 hospital admissions in 2007. Patients A total of 94 917 patients exposed to GBCAs; patients at risk for NSF (3779 patients on hemodialysis, 1694 patients with renal transplants, and 717 patients with liver transplants, a well-defined subgroup that includes patients at risk for reduced renal function); and 61 patients with a clinical diagnosis of NSF. MAIN OUTCOME MEASURE: Risk estimate for NSF. RESULTS: The risk of development of NSF is 1.0% for patients who undergo hemodialysis (8 of 827), 0.8% for patients with renal transplantation (4 of 527), and 0% for patients with liver transplantation at our institution (0 of 327). CONCLUSIONS: Despite the limitations, this study, which reviewed a large number of patients who underwent intravascular GBCA injections, demonstrates a 77-fold higher risk of NSF among patients who undergo hemodialysis and a 69-fold higher risk in patients with renal transplantation. This increased risk is thought to be associated with poor clearance of most GBCAs.

Aberrant right hepatic arterial anatomy and pancreaticoduodenectomy: recognition, prevalence and management.

BACKGROUND: Aberrant arterial anatomy is a common finding during foregut surgery. Anomalies to the right hepatic lobe are especially relevant during pancreaticoduodenectomy (PD) and their recognition serves to protect the blood supply to the liver and bile ducts. We report our experience with aberrant right hepatic arterial anatomy (ARHAA) found during PD. METHODS: All patients who underwent PD between February 2003 and June 2007 were retrospectively reviewed and those with ARHAA were identified. Preoperative imaging studies were assessed by one radiologist, graded according to the presence of ARHAA and compared with the original interpretations. RESULTS: We found ARHAA in 31 of 191 patients (16.2%). Operative management included dissection and preservation in 24, transection and reconstruction in four, and transection and primary anastomosis in three patients. Reconstruction of ARHAA was carried out through interposition grafts in two patients and implantation into the gastroduodenal stump in two patients. No cases of arterial thrombosis, liver infarction, abscess formation or biliary fistula were demonstrated in the immediate postoperative period. Review of preoperative imaging interpretations found that only nine of 23 reports indicated the presence of ARHAA; however, the retrospective review of the images found that ARHAA was readily apparent in 24 patients. DISCUSSION: Recognition of aberrant vasculature to the liver before PD is important. Preoperative imaging studies will often be adequate to identify these anomalies, but interpreting radiologists may not be aware of its clinical significance. Surgeons performing PD must be adept at managing ARHAA safely.

High-dose gadodiamide for catheter angiography and CT in patients with varying degrees of renal insufficiency: Prevalence of subsequent nephrogenic systemic fibrosis and decline in renal function.

OBJECTIVE: The purpose of our study was to evaluate the prevalence of nephrogenic systemic fibrosis (NSF) and nephrotoxicity among patients with differing degrees of renal dysfunction who are exposed to high doses of gadodiamide. MATERIALS AND METHODS: A search of medical records identified patients who received high-dose IV gadodiamide for catheter angiography or CT between January 2002 and December 2005. The cohort was limited to patients who had received a dose of at least 40 mL of gadodiamide during a single imaging session, who underwent at least 1 year of clinical follow-up, and who had moderate to end-stage renal disease (estimated glomerular filtration rate [GFR] < 60 mL/min/1.73 m(2)) established within the previous 48 hours. Any observation suggestive of NSF was recorded, as were all estimated GFR values obtained during the 2 weeks before and the 5 days after gadodiamide administration. RESULTS: Sixty-one patients met the inclusion criteria. The median estimated GFR was 30 mL/min/1.73 m(2) (range, 3-57 mL/min/1.73 m(2)). The median gadodiamide exposure was 80 mL (range, 40-200 mL). NSF eventually developed in one of the 61 patients, yielding a prevalence of 1.6%. Among the 33 patients not undergoing dialysis with estimated GFR documented within 5 days after contrast injection, the change in estimated GFR ranged from -8.8 to 42.9 mL/min/1.73 m(2), with a statistically significant median improvement of 2.4 mL/min/1.73 m(2) (p = 0.007). CONCLUSION: Although gadolinium exposure appears to be a necessary precondition for NSF, gadolinium-based contrast agents alone are not sufficient to cause the disorder, even in very high doses. Clinically relevant nephrotoxicity of gadolinium-based contrast agents was not found.

Magnetic resonance imaging of the sacral plexus and piriformis muscles.

OBJECTIVE: The objective was to evaluate the piriformis muscles and their relationship to the sacral nerve roots on T1-weighted MRI in patients with no history or clinical suspicion of piriformis syndrome. PATIENTS AND METHODS: Axial oblique and sagittal T1-weighted images of the sacrum were obtained in 100 sequential patients (200 pairs of sacral roots) undergoing routine MRI examinations. The relationship of the sacral nerve roots to the piriformis muscles and piriformis muscle size were evaluated, as were clinical symptoms via a questionnaire. RESULTS: The S1 nerve roots were located above the piriformis muscle in 99.5% of cases (n=199). The S2 nerve roots were located above the piriformis muscle in 25% of cases (n=50), and traversed the muscle in 75% (n=150). The S3 nerve roots were located above the piriformis muscle in 0.5% of cases (n=1), below the muscle in 2.5% (n=5), and traversed the muscle in 97% (n=194). The S4 nerve roots were located below the muscle in 95% (n=190). The piriformis muscles ranged in size from 0.8-3.2 cm, with an average size of 1.9 cm. Nineteen percent of patients had greater than 3 mm of asymmetry in the size of the piriformis muscle, with a maximum asymmetry of 8 mm noted. CONCLUSION: The S1 nerve roots course above the piriformis muscle in more than 99% of patients. The S2 roots traverse the piriformis muscle in 75% of patients. The S3 nerve roots traverse the piriformis muscle in 97% of patients. Piriformis muscle size asymmetry is common, with muscle asymmetry of up to 8 mm identified.

Gallbladder lymphangioma: a case report and review of the literature.

Lymphangiomas are benign neoplasms usually occurring in childhood and located in the head and neck. Intraabdominal lymphangiomas account for less than 5% of cases. The involvement of the gallbladder is rare. We report a case of a 29-year-old woman who presented with right upper quadrant pain that had persisted for 6 months. Imaging with ultrasound and magnetic resonance imaging (MRI) revealed a multiseptated lesion surrounding the gallbladder. The patient underwent an exploratory laporatomy, and the mass was resected en bloc with the gallbladder. Histological evaluation of the cystic mass revealed findings consistent with lymphangioma. The prognosis is generally good after complete surgical excision, as was the case for our patient.

Urethral bulking agents: imaging review.

OBJECTIVE: At imaging, injectable bulking materials used for urinary incontinence have the potential to mimic urethral and periurethral pathology. This article elucidates the appearance of the most commonly used agents in multiple techniques and helps the practicing radiologist avoid potential diagnostic pitfalls. CONCLUSION: Carbon-coated microbeads (Durasphere) and cross-linked bovine collagen (Contigen) have fairly characteristic imaging appearances and can in most cases be differentiated from true pathology.

Diagnosing biliary complications of orthotopic liver transplantation with mangafodipir trisodium-enhanced MR cholangiography: comparison with conventional MR cholangiography.

OBJECTIVE: This study was designed to determine whether the addition of mangafodipir trisodium-enhanced MRI could improve the image quality, visualization of ductal structures, and diagnostic confidence provided by conventional T2-based MR cholangiography (MRC) in patients with suspected biliary complications after orthotopic liver transplantation. SUBJECTS AND METHODS. Our study group consisted of 25 consecutive patients who were referred for MR evaluation of clinically suspected biliary complications after orthotopic liver transplantation. Conventional MRC in the axial and coronal planes was performed in each patient, followed by fat-suppressed volumetric gradient-echo imaging in the same planes both before and after the IV administration of mangafodipir trisodium. Imaging was performed in all patients until the contrast agent was seen in the bowel. Images were then graded for quality, visualization of bile ducts and anastomoses, presence of significant stricture or leak, and level of diagnostic confidence. RESULTS: Mangafodipir trisodium-enhanced MRC tended to outperform conventional MRC in overall image quality and extrahepatic duct visualization; it was also more effective in delineating biliary anastomoses, and the difference was statistically significant (p < 0.001). All 25 enhanced examinations were considered diagnostic. Diagnostic confidence was scored as poor or lacking in 14 of the conventional MRC examinations for biliary stenosis and in 12 examinations for biliary leak. CONCLUSION: Enhancement with mangafodipir trisodium improves the performance of MRC for the detection and exclusion of biliary abnormalities after orthotopic liver transplantation. Future investigations should compare the performance of mangafodipir trisodium-enhanced MRC with the performance of more invasive techniques.

Incidence of occult rectal prolapse in patients with clinical rectoceles and defecatory dysfunction.

OBJECTIVE: The purpose of this study was to determine the incidence of occult rectal prolapse (rectal intussusception) by defecating proctography in patients with clinical rectoceles and defecatory dysfunction. STUDY DESIGN: Patients who were seen from September 2000 through August 2001 with defecatory dysfunction and clinical rectoceles underwent single contrast defecating proctography. Radiologists who specialized in gastrointestinal fluoroscopy interpreted the results, which were retrieved from a computerized database. Study Design: Sixty patients who met the inclusion criteria were evaluated. Twenty patients (33%) had intussusception; 58 patients (97%) had rectocele; 1 patient (1.7%) had sigmoidocele, and 6 patients (10%) had anismus (paradoxic contraction of the puborectalis). RESULTS: All but 1 case of intussusception was associated with a rectocele radiographically. Anismus was associated with rectoceles radiographically, except in 1 patient for whom it was the sole finding. CONCLUSION: The data suggest a 33% incidence of occult rectal prolapse in patients with clinical rectoceles and defecatory dysfunction. This is highly clinically significant because one third of patients who are examined for defecatory dysfunction and rectocele may require sigmoid resection rectopexy along with other reconstructive procedures to restore pelvic floor function and prevent symptomatic recurrence.