Diagnosis of renal vascular disease with MR angiography.

Renal magnetic resonance (MR) angiography allows accurate evaluation of patients suspected to have renal artery stenosis without the risks associated with nephrotoxic contrast agents, ionizing radiation, or arterial catheterization. Other applications of renal MR angiography are mapping the vascular anatomy for planning renal revascularization, planning repair of abdominal aortic aneurysms, assessing renal bypass grafts and renal transplant anastomoses, and evaluating vascular involvement by renal tumors. A variety of pulse sequences provide complementary information about kidney morphology, arterial anatomy, blood flow, and renal function and excretion. Three-dimensional gadolinium-enhanced MR angiography can be combined with several other sequences to produce a comprehensive approach to renal MR angiography. This comprehensive approach is designed to allow hemodynamic characterization of renal artery stenosis with a single MR imaging examination that can be easily completed in 1 hour. Three-dimensional gadolinium-enhanced MR angiography demonstrates the renal arteries along with the abdominal aorta, iliac arteries, and mesenteric arteries in a 20-30-second acquisition that can be performed during breath holding. Numerous projections are reconstructed from a single three-dimensional volume of data acquired with a single injection of contrast material to obtain perpendicular and optimized views of each renal artery.

Speckle decorrelation flow measurement with B-mode US of contrast agent flow in a phantom and in rabbit kidney.

PURPOSE: To use speckle decorrelation in the presence of ultrasonographic (US) contrast agent as an alternative flow measurement technique to Doppler US. MATERIALS AND METHODS: In vivo and in vitro studies were performed. A tube with flowing saline solution containing contrast agent was positioned horizontally across a US image. The amount of decorrelation between a series of images was recorded. The flow profile across the tube was generated by averaging the decorrelation values and was compared with a Doppler frequency shift image. In addition, B-mode images of six rabbit kidneys were obtained during and after intravenous injection of contrast agent. Images were analyzed to compute the correlation between successive points in time. RESULTS: The velocity profiles across the tube were parabolic, with the fastest flow rates measured in the center of the tube. In the rabbit kidneys, measurements indicated the largest decorrelation rates occurred in the larger vessels. The cortical decorrelation rates were significantly slower than those for the hilar vessels (P < .05) and were relatively angle independent. CONCLUSIONS: Decorrelation flow measurements can be used to estimate flow in vitro and in vivo similar to measurements obtained with Doppler US but with less angle dependence. These measurements could lead to a US perfusion technique.

Gadolinium-enhanced magnetic resonance venography of the portal venous system prior to transjugular intrahepatic portosystemic shunts and liver transplantation. Original investigation.

RATIONALE AND OBJECTIVES: The accuracy of gadolinium-enhanced magnetic resonance venography (GdMRV) in identifying visceral venous abnormalities was assessed in patients before they underwent transjugular intrahepatic portosystemic shunt (TIPS) or orthotopic liver transplantation (OLT). METHODS: Twenty-seven patients with portal hypertension underwent GdMRV and transcatheter venography prior to OLT or TIPS. The gadolinium dose was 0.5 mL/kg (0.25 mmol/kg), administered by rapid hand injection. Coronal 3D spoiled gradient-echo GdMRV was performed in a single breath-hold. Four blinded reviewers retrospectively evaluated coronal maximum intensity projection (MIP) images, while two reviewers evaluated the MIPs and multiplanar reconstructions. Abnormalities that could affect transjugular intrahepatic portosystemic shunt or transplantation were noted and compared with the results of corresponding catheter venograms read by a separate blinded reviewer. RESULTS: Abnormalities were identified by GdMRV with a sensitivity and specificity of 83% and 97% for the right hepatic vein, 86% and 100% for the main portal vein (MPV), 42% and 99% for the right portal vein, 54% and 94% for the left portal vein, 61% and 96% for the superior mesenteric vein, and 74% and 91% for the splenic vein. Varices and shunts were correctly identified with a sensitivity of 96%. Multiplanar reconstruction increased MPV sensitivity to 100%. CONCLUSION: Vascular abnormalities that affect TIPS and OLT can be identified by GdMRV. Multiplanar reconstruction increased the accuracy to 100% for the MPV.

The dissected aorta: percutaneous treatment of ischemic complications--principles and results.

PURPOSE: Describe the principles and results of percutaneous treatment of ischemic complications of aortic dissection. MATERIALS AND METHODS: Twenty-four patients with aortic dissection complicated by ischemic compromise of the liver or bowel (n = 15), kidney (n = 18), or lower extremity (n = 13) were evaluated by means of aortography, intravascular ultrasound, and manometry, and were treated percutaneously. Visceral arteries were classified as obstructed or nonobstructed. Obstruction was classified as static, in which the dissecting hematoma extended into and narrowed the lumen of a branch artery, or dynamic, in which the dissection flap prolapsed into the vessel origin or narrowed the true lumen (TL) above it. Treatment consisted of vascular stents alone (n = 4), or balloon fenestration (n = 20) without (n = 8) or with (n = 12) vascular stents. RESULTS: Obstruction was present in 77 arteries and was static in 12 arteries, dynamic in 45 arteries, static and dynamic in 17 arteries, and indeterminate in three arteries. Percutaneous treatment did not alter false lumen (FL) pressure, but reduced the peak systolic interluminal pressure gradient from 28 mm Hg to 2 mm Hg and restored flow in 71 of 77 arteries (92%). Six patients died within 30 days (25% operative mortality), none as a result of the procedure. Two additional patients died in follow-up from complications of an expanding FL. Technical complications in two patients due to altered hemodynamics after initial intervention were recognized and corrected percutaneously during the same procedure. CONCLUSIONS: Percutaneous fenestration and endovascular stent deployment are indicated to restore blood flow to arteries compromised by aortic dissection. The prognosis of patients is related to the ischemic injury sustained prior to the percutaneous interventional procedure and, in patients with acute type I dissection who have not undergone surgery, to the preoperative stability of the FL.

The dissected aorta: part III. Anatomy and radiologic diagnosis of branch-vessel compromise.

PURPOSE: To determine the anatomic, hemodynamic, and radiologic characteristics of branch-vessel compromise in patients with aortic dissection. MATERIALS AND METHODS: Sixty-two patients with aortic dissection were evaluated with aortography (n = 62), intravascular ultrasound (US) (n = 35), and manometry (n = 56). Branch-vessel compromise with ischemia was suspected in 40 of these patients. Radiologic and manometric findings were correlated with clinical findings of ischemia. Femoral artery pulse strength was correlated with access from the respective femoral artery to the true and false lumina of the dissected aorta. RESULTS: Twenty-six of 40 patients suspected of having ischemia had angiographic evidence of branch-vessel compromise, and intravascular US helped identify two types of branch-vessel compromise in them: static (dissection intersected and narrowed the vessel origin) and dynamic (dissection spared the vessel origin, but the dissection flap appeared to compress the true lumen at or above the origin and covered the origin). False-lumen pressure in classic dissections exceeded (n = 16) or equaled (n = 30) true-lumen pressure. Branch vessels that arose exclusively from the false lumen were well perfused. Findings of a dissection flap oriented concave toward the false lumen were 91% sensitive and 72% specific for a true-lumen pressure deficit. CONCLUSION: Intravascular US and manometric findings clarify the mechanisms of branch-vessel compromise after aortic dissection and provide a rational guide for percutaneous treatment.

Gadolinium-enhanced magnetic resonance angiography of renal transplants.

Our purpose was to investigate three-dimensional (3D) gadolinium-enhanced magnetic resonance angiography (Gd-MRA) in the evaluation of renal transplant arteries. Eleven MR angiography examinations were performed in nine renal transplant patients. Gd-MRA, three-dimensional phase contrast (3D-PC) post-gadolinium, and two-dimensional time-of-flight (2D-TOF) MR angiography were performed and independently reviewed by three vascular radiologists who, for each MR angiography sequence, separately graded occlusive disease in the ipsilateral iliac artery, the transplant artery anastomosis, and the transplant artery itself. The Gd-MRA and 3D-PC data were reviewed as maximum intensity projections (MIP) reconstructed in standard planes, and the 2D-TOF data were interpreted from source images. In addition, a single vascular radiologist prospectively interpreted the Gd-MRA and 3D-PC data together, hereinafter Gd/PC, from MIP reconstructions for each case. In all of these patients either surgical (n = 3) or angiographic studies (n = 8) were performed within 21 days following the MR examination, which served as a reference standard to determine sensitivity and specificity. The sensitivity/specificity for the detection of significant stenosis were as follows: Gd-MRA, 67/88; 3D-PC, 60.3/76.6; 2D-TOF, 47/81; and Gd/PC, 100/100. The kappa statistic (kappa) for interobserver agreement for the grading of stenoses by 2D-TOF, Gd-PC, and Gd-MRA was 0.48, 0.60, and 0.74, respectively. The percentage of all vascular segments seen well enough to grade (cumulative for all three observers) was 94%, 85%, and 79% for Gd-MRA, 3D-PC, and 2D-TOF, respectively. The combination of Gd-MRA and 3D-PC is a promising approach to the evaluation of transplant renal arteries.

Discrete gastrointestinal mass lesions caused by cytomegalovirus in patients with AIDS: report of three cases and review.

We report the detailed clinical features of discrete mass lesions of the gastrointestinal tract caused by cytomegalovirus in three patients who had the acquired immunodeficiency virus syndrome. The disease occurred in the fundus of the stomach in one patient and in the cecum in the other two persons. The symptoms as well as radiographic and endoscopic findings in each case are described and are shown to be indistinguishable from those resulting from a neoplasm. The diagnosis was established by the presence of inflammation with cytomegalovirus-like inclusions and confirmed by immunoperoxidase staining. Cytomegalovirus infection should be considered, along with Kaposi's sarcoma and lymphoma, as a cause of focal mass lesions of the alimentary tract in persons infected with HIV.