Fadi El-Merhi

Causes of TIPS Dysfunction

OBJECTIVE Transjugular intrahepatic portosystemic shunt (TIPS) creation is an effective method to control portal hypertension. TIPS creations with bare stents have shown limited and unpredictable patency. In nearly all cases of rebleeding or recurrent ascites after TIPS creation, there is shunt stenosis or occlusion. The purpose of this article is to review the biologic and technical factors that predispose to TIPS failure and how the use of an expandable polytetrafluoroethylene (PTFE)-covered-stent has significantly improved TIPS patency. CONCLUSION Biologic and technical factors may predispose to shunt failure. The combination of improved technique and expandable PTFE has significantly improved TIPS patency. The need for follow-up venography and secondary interventions has been reduced significantly as a result of improved shunt patency.

Vascular malformations and arteriovenous fistulas of the kidney

Vascular malformations of the kidney are disease processes that involve renal veins and arteries and include congenital arteriovenous malformations (AVMs) and arteriovenous fistulas. AVMs are congenital communications between arteries and veins with a vascular nidus that bypass the capillary bed. Congenital AVMs are rare and subclassified in cirsoid, angiomatous, and aneurysmal types. Congenital AVMs are different from iatrogenic or traumatic arteriovenous fistulas (AVF), which are characterized by a single direct communication between an artery and a vein without an intervening vascular nidus. These lesions may present with a wide range of signs and symptoms that vary from hypertension to renal masses. Imaging is valuable in the detection and characterization of AVM and AVF. The presence of arteriovenous shunting characterizes AVM and AVF. These lesions represent an important group of entities for diagnostic consideration, and understanding the vascular anatomy helps in guiding for proper treatment. This article describes the imaging features of each lesion that help to differentiate it from the others and the endovascular therapies to treat these vascular processes and their possible complications.

Arteriovenous Malformations of the Uterus

Arterial venous malformations (AVM) of the uterus are uncommon entities and should be considered in patients who present with profuse genital bleeding. There are two types of uterine AVM: acquired and congenital. Acquired uterine AVMs are conformed by communications between the uterine arteries and the myometrial veins, and are caused by an iatrogenic event or a pathological condition. Congenital AVMs are the result of abnormal development of primitive vessels that result in connections between pelvic arteries and veins in the uterus without an interconnecting capillary bed. Ultrasonography is a noninvasive diagnostic method able to demonstrate and characterize AVMs of the uterus. AVM in the pelvis may be noted incidentally by computed tomography (CT) of the pelvis, and magnetic resonance imaging (MRI) is frequently used to confirm and further characterize the sonographic findings of uterine AVM. Catheter angiography and embolization are very effective in defining the vascular anatomy and treating uterine vascular abnormalities.

Hybrid peripheral 3D contrast-enhanced MR angiography of calf and foot vasculature

OBJECTIVE The objective of our study was to describe hybrid peripheral (HyPer) 3D contrast-enhanced MR angiography (CE-MRA) using sagittal acquisition with parallel imaging of the calf and foot station. The benefit of a dedicated sagittal 3D CE-MRA acquisition of the calf and foot was evaluated by assessing the degree of venous contamination and its diagnostic quality compared with standard bolus chase 3D CE-MRA alone. MATERIALS AND METHODS Fifty-three patients (99 legs) were scanned with a 1.5-T MR system equipped with a dedicated bilateral lower extremity phased-array coil. First, high-resolution 3D CE-MRA images of the calves and feet were obtained using two separate sagittal slabs with parallel imaging, with a resulting voxel size of 1.4 x 1.0 x 1.0 mm3. Second, standard bolus chase 3D CE-MRA was performed from the abdomen and pelvis station to the calf-foot station. Images were interpreted by two radiologists. The calf-foot arterial trees were divided into 12 segments. Each segment was characterized as diagnostic or nondiagnostic. The degree of venous contamination was assessed as interfering with the diagnosis or not. Paired Students t test and Wilcoxons signed rank test were used to test for statistically significant differences between the techniques. RESULTS For the left leg (n = 48), the mean number (+/- SD) of diagnosed arterial segments for HyPer 3D CE-MRA was 9.2 +/- 2.3 and for bolus chase 3D CE-MRA, 7.1 +/- 4.2 (p < or = 0.0004). For the right leg (n = 51), the corresponding values were 9.4 +/- 2.2 and 7.6 +/- 3.5 (p < or = 0.0005), respectively. For bolus chase 3D CE-MRA, venous contamination interfered with the diagnosis in 24 of 99 legs, whereas with HyPer 3D CE-MRA, there was no interference. Selective analysis of the dorsalis pedis arteries showed that the number of diagnostic vessels was 62 (62.6%) of 99 for HyPer 3D CE-MRA and 13 (13.1%) of 99 for bolus chase 3D CE-MRA. CONCLUSION HyPer 3D CE-MRA is an alternative method for time-resolved high-resolution peripheral CE-MRA in evaluating the trifurcation and feet vessels with no venous contamination.

Renal aneurysms and pseudoaneurysms.

Pseudoaneurysms and aneurysms are abnormal dilatations of the vessel lumen. Pseudoaneurysm is a perfused hematoma contained by the adventitia and perivascular tissues that is in communication with the lumen of an adjacent artery or vein. Aneurysm is a dilatation of the vessel lumen involving all three layers of the blood vessel wall. Renal artery aneurysms (RAA) are uncommon but the widespread use of cross-sectional imaging and incidental detection of RAA may result in an increasing number of cases diagnosed. Renal artery pseudoaneurysms are suspected in bleeding patients after penetrating renal trauma. Imaging plays a major role in the detection of renal pseudoaneurysms and aneurysms and diagnoses aneurysm rupture and active bleeding. Computed tomography (CT), magnetic resonance imaging, and digital subtraction angiography can characterize lesion size, shape, and location and identify other aneurysms and pseudoaneurysms, helping to narrow the differential diagnosis and to understand the vascular anatomy for guiding proper treatment. Endovascular treatments have contributed considerably in the management of renal pseudoaneurysms and aneurysms. The use of coil embolization or covered stent placement prevents the mortality and mobility of surgery. The article describes imaging features and the endovascular therapies to treat these vascular processes and their possible complications.

Magnetic resonance imaging of the gallbladder: spectrum of abnormalities.

Various pathologies involving the gallbladder can manifest clinically, producing nonspecific clinical symptoms and making diagnosis difficult and challenging. Real-time sonography is the most widely used diagnostic study for the gallbladder and the primary screening examination of choice. With increasing use of magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP), gallbladder pathology is frequently seen. Understanding the basic patterns of various disease manifestations and appearance on MRI is the key to making an accurate diagnosis. Given its inherent tissue contrast and contrast sensitivity, MRI in conjunction with MRCP can be a very valuable test in evaluating gallbladder pathology. Gallbladder pathology can be classified into congenital (such as absence), inflammatory (acute, hemorrhagic, and chronic cholecystitis), traumatic, benign (polyps) and malignant tumors (gallbladder carcinoma and lymphoma), and other disease processes can be seen in cholelithiasis, cholesterosis, thickened gallbladder wall, and Mirrizzi syndrome.

Transjugular Intrahepatic Portosystemic Shunt Flow Reduction with Adjustable Polytetrafluoroethylene-covered Balloon-expandable Stents

Creation of a transjugular intrahepatic portosystemic shunt (TIPS) can effectively treat complications of portal hypertension, but excessive shunting can cause life-threatening hepatic encephalopathy and hepatic insufficiency. The present report describes a novel technique that allows for controlled and adjustable flow reduction through the TIPS via partial closure of the shunt with a balloon-mounted covered stent. The method results in clinical improvement of hepatic encephalopathy and hepatic insufficiency and immediate increase in the portosystemic pressure gradient. However, among the four patients described herein, survival beyond 1 year was seen in only one, who underwent liver transplantation after TIPS reduction.

Fast T2*-Weighted MRI of the Prostate at 3 Tesla

To describe a rapid T2*‐weighted (T2*W), three‐dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1‐weighted turbo‐spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

Peripheral vascular tumors and vascular malformations: imaging (magnetic resonance imaging and conventional angiography), pathologic correlation and treatment options

Vascular anomalies are classified into vascular tumors (infantile hemangioma) and vascular malformations. Vascular malformations are divided into slow flow and high flow subtypes. Magnetic resonance imaging helps in classification and assessing extent and distribution. Conventional angiography also known as digital subtraction angiography is pivotal in assessment of fine vascular details and treatment planning. Imaging correlates well with histopathology. We review recent development in imaging techniques of various vascular anomalies most of which are affecting the peripheral system which potentially may broaden understanding of their diagnosis, classification and treatment.

MDCT angiography of mesenteric bypass surgery for the treatment of chronic mesenteric ischemia

OBJECTIVE Chronic mesenteric ischemia (CMI) is a serious condition that requires surgical or endovascular intervention. Surgical revascularization for the treatment of CMI uses different operative techniques including endarterectomy, vessel reimplantation, and mesenteric bypass. A basic understanding of the operative techniques is essential for the adequate interpretation of imaging studies in patients who have undergone surgery for CMI. In this article, we review the different operative techniques used in the treatment of CMI, discuss the results of surgical intervention for CMI, and illustrate how MDCT angiography (MDCTA) can be used for follow-up and for the detection of early and late complications after surgery. CONCLUSION MDCTA is a powerful tool for the postoperative evaluation of patients with CMI. Early detection of graft dysfunction is critical to prevent graft occlusion and the development of potentially fatal mesenteric ischemia. MDCTA can detect early and late complications after surgery and guide additional surgical or endovascular interventions.