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Benjamin M Yeh

Publications and source records attributed to Benjamin M Yeh.

At least 37 records · Page 2Linked to original sources
PubMed2004

Use of CT cholangiography to evaluate the biliary tract after liver transplantation: initial experience.

Evaluation of the biliary tract after liver transplantation, particularly when a Roux-en-Y hepatojejunostomy precludes endoscopic retrograde cholangiography, may be challenging. We present five cases of suspected biliary obstruction after liver transplantation in which multidetector-row computed tomography (CT) cholangiography was used. In conclusion, it was determined that multidetector-row CT cholangiography may be a useful modality for demonstrating patent biliary-enteric anastomoses and excluding flow-limiting biliary anastomotic strictures.

Adult↗
PubMed2004

Precaval right renal arteries: prevalence and morphologic associations at spiral CT.

PURPOSE: To determine the prevalence and morphologic associations of precaval right renal arteries at spiral computed tomography (CT). MATERIALS AND METHODS: The authors retrospectively reviewed 186 arterial phase contrast material-enhanced spiral CT scans of the abdomen (5.0-mm section thickness in 97 scans, 2.5 mm in 89 scans) obtained during a 2-year period to identify patients with precaval right renal arteries. During routine interpretation of CT scans at daily readout, the authors prospectively identified 39 additional patients with precaval right renal arteries. All cases were evaluated for anatomic variants and associated clinical findings. Fisher exact analysis and chi2 analysis were performed to compare the frequency of anatomic variants between patients with and those without precaval renal arteries. RESULTS: Nine of 186 patients had precaval right renal arteries, for a prevalence of 5%. In the 48 patients with precaval renal arteries, 52 precaval arteries were found, of which 48 were accessory and four were dominant. Fourteen patients had right pelviectasis to the level of the precaval artery, and three of these had a clinical diagnosis of right ureteropelvic junction obstruction. Eighteen (35%) of the 52 precaval renal arteries arose from the anterior aspect of the aorta (within 30 degrees of the midline). The lower pole of the right kidney was rotated anteriorly in two (22%) of nine and 13 (33%) of 39 patients with precaval renal arteries in the retrospective and prospective groups, respectively, compared with four (2%) of 177 patients without precaval arteries (P <.05 and P <.001, respectively). CONCLUSION: On the basis of these results, precaval right renal arteries appear to be more common than previously reported. Anterior rotation of the lower pole of the right kidney should prompt a search for precaval renal arteries.

Adult↗
PubMed2004

Biliary tract depiction in living potential liver donors: comparison of conventional MR, mangafodipir trisodium-enhanced excretory MR, and multi-detector row CT cholangiography--initial experience.

PURPOSE: To compare biliary tract depiction in living potential liver donors at conventional magnetic resonance (MR), mangafodipir trisodium-enhanced excretory MR, and multi-detector row computed tomographic (CT) cholangiography. MATERIALS AND METHODS: Eight living potential liver donors underwent iodipamide meglumine-enhanced CT cholangiography. Eight different potential liver donors then underwent conventional MR cholangiography and mangafodipir trisodium-enhanced excretory MR cholangiography. Two readers independently scored all first-, second-, and third-order biliary branches with a four-point scale from 0 (not seen) to 3 (excellent visualization). Interobserver agreement was calculated by using the weighted kappa statistic. Scores were compared between imaging modalities by using generalized estimating equations. Imaging findings of second-order biliary tract anatomy were compared with intraoperative findings for nine patients. RESULTS: Interobserver agreement for overall biliary tract visualization was good for CT, conventional MR, and excretory MR cholangiography (with weighted kappa values of 0.76, 0.66, and 0.79, respectively). The mean second-order biliary branch visualization scores for readers 1 and 2, respectively, were significantly higher at CT cholangiography (2.81 and 2.75) than at conventional MR (1.84 and 1.75, P <.001), excretory MR (2.00 and 2.06, P <.001), and combined conventional and excretory MR cholangiography (2.31 and 2.25, P <.01). At CT, conventional MR, and excretory MR cholangiography, respectively, second-order biliary branching anatomy was discernible in eight, five, and seven patients, with second-order biliary branch variants seen in three, two, and two patients. Surgical findings confirmed the pattern of second-order biliary branching seen at CT in five patients, that seen at conventional MR imaging in one patient, and that seen at excretory MR cholangiography in three patients. At surgery, one case of variant biliary anatomy was found to have been missed at CT cholangiography. CONCLUSION: In living potential liver donors, CT cholangiography enables significantly better biliary tract visualization than conventional or excretory MR cholangiography either alone or in combination.

Adolescent↗
PubMed2004

Peritoneal calcification: causes and distinguishing features on CT.

OBJECTIVE: We undertook this study to determine the causes of peritoneal calcification seen on CT and to investigate which CT features distinguish benign from malignant peritoneal calcification. MATERIALS AND METHODS: Seventeen patients with peritoneal calcification were identified through retrospective review of reports from 74765 abdominopelvic CT examinations performed during a 7-year period. We determined the cause of peritoneal calcification by examining medical and histopathologic records. Calcification morphology was classified as nodular or sheetlike on the basis of the consensus interpretation by two independent radiologists. The radiologists also recorded the presence or absence of associated soft-tissue components or lymph node calcification. The association between the CT findings and the cause of calcification was assessed using chi-square analysis. RESULTS: Peritoneal calcification was due to peritoneal dialysis (n = 4), prior peritonitis (n = 3), cryptogenic origin (n = 1), or peritoneal spread of ovarian carcinoma (n = 9). Sheet-like calcification was more common in patients with benign calcification (seven of eight patients) than in those with malignant calcification (two of nine patients, p < 0.05). Nodal calcification was seen only in patients with malignant calcification (five of nine patients vs none of eight, p < 0.05). CONCLUSION: Common causes of peritoneal calcification are dialysis, prior peritonitis, or ovarian cancer; sheetlike calcification indicates a benign cause, whereas associated lymph node calcification strongly suggests malignancy.

Adult↗
PubMed2004

Parallel imaging and diffusion tensor imaging for diffusion-weighted MRI of the liver: preliminary experience in healthy volunteers.

OBJECTIVE: Our aim was to determine whether parallel imaging and diffusion tensor imaging affect the measurement of apparent diffusion coefficient (ADC) during diffusion-weighted MRI of the liver in healthy volunteers. SUBJECTS AND METHODS: We performed breath-hold single-shot echo-planar diffusion-weighted MRI of the liver in 10 healthy volunteers using conventional diffusion, conventional diffusion with parallel imaging, and diffusion tensor with parallel imaging sequences. TE values for the three sequences were 83, 74, and 63, respectively. Liver signal intensity was measured on all sequences and normalized to the SD of the measurement. Hepatic ADC was calculated by acquiring all sequences with b values of 0 and 500 sec/mm(2). RESULTS: The normalized liver signal intensity was higher on diffusion tensor with parallel imaging and conventional diffusion with parallel imaging than on conventional diffusion without parallel imaging for a b value of 500 sec/mm(2) (13.0 and 10.1 vs 9.1, respectively; p < 0.03) and for a b value of 0 sec/mm(2) (9.0 and 7.6 vs 6.9, respectively; without reaching a significant difference, p = 0.12). Hepatic ADC was not significantly different between sequences (p = 0.16). CONCLUSION: Higher signal intensity can be obtained when using parallel imaging and diffusion tensor imaging during diffusion-weighted MRI of the liver without compromising hepatic ADC measurement.

Adult↗
PubMed2004

Hepatic pseudotumor due to nodular fatty sparing: the diagnostic role of opposed-phase MRI.

OBJECTIVE: We sought to describe the role of opposed-phase MRI in the diagnosis of nodular fatty sparing in the liver. CONCLUSION: Nodular fatty sparing of the liver displays characteristic findings on opposed-phase MRI. Because the lesion may otherwise mimic a hepatic tumor, knowledge of these findings may prevent unnecessary biopsy or inappropriate treatment.

Adolescent↗
PubMed2004

Organ-confined prostate cancer: effect of prior transrectal biopsy on endorectal MRI and MR spectroscopic imaging.

OBJECTIVE: Our aim was to determine the effect of prior transrectal biopsy on endorectal MRI and MR spectroscopic imaging findings in patients with organ-confined prostate cancer. MATERIALS AND METHODS: Endorectal MRI and MR spectroscopic imaging were performed in 43 patients with biopsy-proven prostate cancer before radical prostatectomy confirming organ-confined disease. For each sextant, two independent reviewers scored the degree of hemorrhage on a scale from 1 to 5 and recorded the presence or absence of capsular irregularity. A spectroscopist recorded the number of spectrally degraded voxels in the peripheral zone. The outcome variables of capsular irregularity and spectral degradation were correlated with the predictor variables of time from biopsy and degree of hemorrhage after biopsy. RESULTS: Capsular irregularity was unrelated to time from biopsy or to degree of hemorrhage. Spectral degradation was inversely related to time from biopsy (p < 0.01); the mean percentage of degraded peripheral zone voxels was 18.5% within 8 weeks of biopsy compared with 7% after 8 weeks. Spectral degradation was unrelated to the degree of hemorrhage. CONCLUSION: In organ-confined prostate cancer, capsular irregularity can be seen at any time after biopsy and is independent of the degree of hemorrhage, whereas spectral degradation is seen predominantly in the first 8 weeks after biopsy. MRI staging criteria and guidelines for scheduling studies after biopsy may require appropriate modification.

Biopsy↗
PubMed2004

Clinical relevance of retrograde inferior vena cava or hepatic vein opacification during contrast-enhanced CT.

OBJECTIVE: The purpose of this investigation was to explore the clinical relevance of retrograde inferior vena cava or hepatic vein opacification during contrast-enhanced CT. MATERIALS AND METHODS: We retrospectively identified 127 patients who underwent contemporaneous contrast-enhanced CT of the chest or abdomen and echocardiography. On CT, the presence of retrograde inferior vena cava or hepatic vein opacification and the rate of IV contrast injection (> 3 mL/sec, high; < or = 3 mL/sec, low) were recorded. On echocardiography, the presence of tricuspid regurgitation, pulmonary hypertension, or right ventricular systolic dysfunction was recorded. RESULTS: Retrograde inferior vena cava or hepatic vein opacification was more common in studies performed with a high rather than a low contrast injection rate (28/56 vs 6/71 patients, respectively; p < 0.01). This finding was 31% sensitive (5/16) and 98% specific (54/55) for right-sided heart disease at low contrast injection rates, and 81% sensitive (17/21) and 69% specific (24/35) at high injection rates. Multivariate logistic regression models showed that high injection rate, tricuspid regurgitation, pulmonary hypertension, and right ventricular systolic dysfunction were independent predictors of retrograde inferior vena cava or hepatic vein opacification (p < 0.05 for each). CONCLUSION: Retrograde opacification of the inferior vena cava or hepatic veins on CT is a specific but insensitive sign of right-sided heart disease at low contrast injection rates, but the usefulness of this classic sign decreases with high injection rates. This realization is important because many centers increasingly use high-injection-rate CT.

Adolescent↗
PubMed2004

Symptomatic perirenal serous cysts of müllerian origin mimicking renal cysts on CT.

OBJECTIVE: Our aim was to describe the clinical presentation, CT appearance, and management of a series of symptomatic perirenal serous cysts of müllerian origin, confirmed by laparoscopic resection. CONCLUSION: Perirenal serous cysts of müllerian origin are uncommon lesions that may present as large symptomatic perirenal cystic masses mimicking exophytic renal cysts on CT. Serous cyst of müllerian origin should be considered in the differential diagnosis when CT reveals a large solitary perirenal cyst in a woman with flank or abdominal pain or both. Laparoscopic resection may be an effective treatment of such cysts.

Adult↗
PubMed2004

CT of benign hypervascular liver nodules in autoimmune hepatitis.

OBJECTIVE: The purpose of this report is to describe the frequency and histopathologic basis of benign hypervascular liver nodules seen on CT in patients with autoimmune hepatitis. CONCLUSION: Benign hypervascular liver nodules may be seen on CT in patients with cirrhosis due to autoimmune hepatitis and may represent large regenerative nodules. This phenomenon is important to recognize because of the potential for confusion with hepatocellular carcinoma.

Adolescent↗
PubMed2003

Azygos arch valves: prevalence and appearance at contrast-enhanced CT.

PURPOSE: To evaluate the prevalence and appearance of azygos arch valves at intravenous contrast material-enhanced computed tomography (CT). MATERIALS AND METHODS: Findings of 309 intravenous contrast-enhanced spiral CT examinations of the chest were retrospectively reviewed. The presence of contrast material reflux into the azygos arch and of a focal bulge in the azygos arch was recorded. An azygos valve was considered present if contrast material with a curvilinear posterior contour was seen in the azygos arch. The chi2 test was used to compare the frequency of contrast material reflux into the azygos vein for high and low rates of contrast material injection and for right and left arm injection. RESULTS: Reflux of contrast material into the azygos arch occurred at 154 (49.8%) of 309 examinations, and valves were seen on images of 105 (68.2%) examinations. A focal bulge was seen in the azygos arch on images of 86 (81.9%) of 105 examinations with an azygos valve. Contrast material refluxed more frequently into the azygos vein in examinations with high rates of injection (83 of 128 examinations, 64.8%) than in those with low rates of injection (71 of 181, 39.2%, P <.001). Among the patients with high rates of injection, contrast material refluxed more frequently into the azygos vein with the right arm injection than with left arm injection (53 of 70, 76% vs 30 of 58, 52%, P <.01). Refluxed contrast material appeared as discrete collections within cusps of the azygos valves on images of 69 (44.8%) of 154 examinations. CONCLUSION: Valves in the azygos arch are common and more frequently seen at CT when high injection rates and right arm injections are used.

Adolescent↗
PubMed2003

Distinction of renal cell carcinomas from high-attenuation renal cysts at portal venous phase contrast-enhanced CT.

PURPOSE: To determine if renal cell carcinomas can be distinguished from high-attenuation renal cysts on portal venous phase contrast material-enhanced computed tomographic (CT) scans. MATERIALS AND METHODS: Fifty-seven renal cell carcinomas and 37 high-attenuation (>20 HU) renal cysts that were at least 1 cm in diameter were retrospectively identified in 90 patients who underwent portal venous phase contrast-enhanced CT. Two independent readers recorded the CT number and degree of internal heterogeneity (uniform or mildly, moderately, or markedly heterogeneous) of all lesions. Logistic regression analysis with adjustment for the two readers was used to examine the association between clinical and CT parameters and the final diagnosis. Stepwise logistic regression analysis was used to identify independent distinguishing variables, which were then incorporated in a classification and regression tree analysis to construct the most efficient classification algorithm. RESULTS: Renal cell carcinomas were of significantly greater size (5.10 cm vs 2.84 cm, P <.001), mean attenuation (101.2 HU vs 55.3 HU, P <.001), and internal heterogeneity (P <.001) than high-attenuation renal cysts. Stepwise logistic regression showed attenuation and internal heterogeneity were both independent variables associated with final diagnosis, but lesion size was not an independent distinguishing variable after adjustment for internal heterogeneity. Classification and regression tree analysis demonstrated that an attenuation greater than 70 HU or the presence of moderate or marked internal heterogeneity was an accurate sign of renal cell carcinoma, with a sensitivity of 91% (52 of 57) for both readers and a specificity of 92% (34 of 37) for reader 1 and 84% (31 of 37) for reader 2. CONCLUSION: On portal venous phase contrast-enhanced CT scans, attenuation greater than 70 HU or moderate or marked internal heterogeneity favor a diagnosis of renal cell carcinoma over a diagnosis of high-attenuation renal cyst.

Adult↗
PubMed2003

Cardiovascular shunts: MR imaging evaluation.

Magnetic resonance (MR) imaging has become an important tool for the accurate and noninvasive assessment of congenital heart disease. Because more precise delineation of anatomy and evaluation of function can be obtained with MR imaging than with either echocardiography or angiography, MR imaging is frequently used to evaluate cardiovascular shunt lesions. It is essential that imaging specialists be able to recognize the MR imaging features of various kinds of shunts, including supracristal ventricular septal defect, atrioventricular septal defect, and partial anomalous pulmonary venous connection. MR imaging is particularly useful for evaluating shunt severity, which can be expressed quantitatively as the ratio of pulmonary flow to systemic flow. This ratio can be estimated accurately with the use of either volumetric cine MR imaging or velocity-encoded cine MR imaging.

Adult↗
PubMed2003

CT and MR imaging of pericardial disease.

In the evaluation of pericardial disease, computed tomography (CT) and magnetic resonance (MR) imaging traditionally have been used as adjuncts to echocardiography. However, CT and MR imaging are particularly useful as sensitive and noninvasive methods for evaluating loculated or hemorrhagic pericardial effusion, constrictive pericarditis, and pericardial masses. Both CT and MR imaging provide excellent delineation of the pericardial anatomy and can aid in the precise localization and characterization of various pericardial lesions, including effusion, constrictive pericarditis and pericardial thickening, pericardial masses, and congenital anomalies such as partial or complete absence of the pericardium. Both modalities provide a larger field of view than does echocardiography, allowing the examination of the entire chest and detection of associated abnormalities in the mediastinum and lungs. Soft-tissue contrast on CT scans and MR images also is superior to that on echocardiograms. Given the many potential applications of these modalities in the evaluation of pericardial diseases, familiarity with the CT and MR imaging features of these diseases is important.

Adult↗
PubMed2003

MR imaging of retained products of conception.

OBJECTIVE: The objective of this article is to describe the MR imaging appearances of retained products of conception. CONCLUSION: Retained products of conception appear on MR imaging as an intracavitary uterine soft-tissue mass with variable amounts of enhancing tissue and variable degrees of myometrial thinning and obliteration of the junctional zone. These findings should not be misinterpreted as indicating gestational trophoblastic disease, particularly in the setting of a postpartum patient with a normal or minimally elevated beta-human chorionic gonadotropin level. MR imaging may also be helpful in showing anatomic variants that hinder successful instrumentation of the uterine cavity in patients with suspected retained products of conception.

Adult↗
PubMed2003

CT signs of hepatofugal portal venous flow in patients with cirrhosis.

OBJECTIVE: We investigated whether CT signs can be used to predict hepatofugal flow in the main portal vein in patients with cirrhosis. MATERIALS AND METHODS: We retrospectively identified 36 patients with cirrhosis, 18 with hepatopetal and 18 with hepatofugal flow in the main portal vein, who underwent contemporaneous abdominal sonography and CT. Two independent observers evaluated the following features on the randomized CT studies: diameter of the portal, splenic, and superior mesenteric veins; spleen size; and the presence of ascites, varices, or arterial phase portal venous enhancement. These data were correlated with the flow direction seen on sonography. RESULTS: A small main portal vein was the only sign significantly (p </= 0.05) predictive of hepatofugal flow by univariate and multivariate analyses. Observers 1 and 2 recorded a portal vein diameter of less than 1 cm in eight (44%) and seven (39%) of the 18 patients with hepatofugal flow compared with one (6%) and none of the 18 patients with hepatopetal flow, respectively (p < 0.02). Receiver operating characteristic analysis using the size of the portal vein to predict flow direction revealed an area under the curve of 0.83 for observer 1 and 0.74 for observer 2. CONCLUSION: A diameter of less than 1 cm for the main portal vein is highly specific, although not sensitive, for hepatofugal portal venous flow in patients with cirrhosis. This sign may be useful when sonography is limited, or this sign may prompt sonographic assessment in patients not known to have hepatofugal flow.

Adolescent↗
PubMed2002

Precaval right renal artery: description and embryologic origin.

OBJECTIVES: To describe our experience with precaval right renal arteries and discuss a theory of development of this unusual vascular variant. The right renal artery typically passes dorsal to the inferior vena cava and is thought to represent a consistent anatomic relationship. METHODS: Three cases of precaval renal arteries were identified during laparoscopic and endourologic procedures. The intraoperative and radiologic anatomic findings were recorded. The embryologic origins of the kidney and renal artery were reviewed to postulate a mechanism for the precaval location of a renal artery. RESULTS: In all cases, the precaval renal artery was an accessory vessel to the lower pole. Computed tomography demonstrated the location of the accessory artery ventral to the vena cava; the superior "main" renal artery was dorsal to the vena cava. In addition, bifid collecting systems (ie, pelves) were present, and the renal contours suggested nearly complete fusion of two renal moieties, with normal location and rotation of the kidney. No other cases of precaval renal arteries were recorded in urologic operative reports during the past 5 years at the University of California, San Francisco. CONCLUSIONS: The precaval renal artery is a rare but important variant of renal vascular anatomy. Several associated findings on computed tomography (bifid collecting system, enlarged kidney) may suggest its presence. The embryologic origin is likely due to the late, incomplete division of the ureteral bud during the eighth week of gestation. The renal artery to the lower pole develops and persists after the posterior cardinal vein has become the inferior vena cava but before gonadal descent.

Adult↗