Diagnosis of abdominal venous thrombosis by means of spin-echo and gradient-echo MR imaging: analysis with receiver operating characteristic curves

Anemia and the liver. Hepatobiliary manifestations of anemia

Many types of hemolytic anemia may be associated with liver disease. Liver injury can be caused by the adherence of deformed or hemolyzed erythrocyses to hepatic vascular endothelium. Adhesion of large numbers of hemolyzed red blood cells to hepatic macrophages, or occlusion of hepatic sinusoids by fragmented red cells, can also result in injury of the liver. Thrombosis of the hepatic or portal vein is associated with some types of hemolytic anemia, and can cause severe liner injury. These are some examples of hepatic injury that can be caused by hemolytic anemias. This article discusses some aspects of liver disease that is associated with sickle cell anemia, paroxysmal nocturnal hemoglobinuria, glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis, and HELLP syndrome.

Atypical low-signal-intensity renal parenchyma: causes and patterns

Certain renal diseases manifest as low signal intensity of the renal parenchyma on magnetic resonance images. Sometimes, the appearance is sufficiently characteristic to allow a specific radiologic diagnosis to be made. The causes of this finding can be classified into three main categories on the basis of the pathophysiology: hemolysis, infection, and vascular disease. The first category includes paroxysmal nocturnal hemoglobinuria (PNH), hemosiderin deposition in the renal cortex from mechanical hemolysis, and sickle cell disease. The second category includes hemorrhagic fever with renal syndrome (HFRS). The third category includes acute renal vein thrombosis, renal cortical necrosis, renal arterial infarction, rejection of a transplanted kidney, and acute nonmyoglobinuric renal failure with severe loin pain and patchy renal vasoconstriction. These disease processes have different patterns of low signal intensity. PNH, hemosiderin deposition from mechanical hemolysis, and sickle cell disease involve the entire cortex including the columns of Bertin. HFRS involves the medulla, especially the outer medulla, whereas cortical necrosis involves the inner cortex including the columns of Bertin. In renal vein thrombosis, low-signal-intensity lesions involve the outer medulla, an appearance resembling that of HFRS. Wedge-shaped low-signal-intensity regions involving both the cortex and the medulla are seen in arterial infarction.

Prevalence of deep venous anomalies in congenital vascular malformations of venous predominance

PURPOSE

The overall incidence of congenital vascular malformations in the general population is 1.5%. Approximately two thirds of them are malformations of venous predominance. Abnormalities of the deep venous trunks have been observed in association with large superficial compensatory varices in these type of malformations. Knowledge of the integrity of the deep venous system is important in their management because excision of the enlarged superficial veins may be deleterious if there is aplasia or hypoplasia of the deep venous trunks. The objective was to investigate the prevalence and nature of deep venous anomalies that occur in patients with congenital vascular malformations of venous predominance both in our series and in the series from the medical literature.

METHODS

From the last 35 years of medical literature, we reviewed seven series of congenital vascular malformations that provided pertinent information on the subject of our study. We also reviewed our own series of 392 patients with congenital vascular malformations studied at Children's Hospital of Mexico City (1963-1983; n = 223 children) and at Walter Reed Army and National Naval Medical Centers (1984-1998; n = 169 children). Of 392 patients, 257 (65.5%) had malformations of venous predominance; these were the subject of our analysis. Prevalence of the following deep venous anomalies was recorded: phlebectasia, aplasia or hypoplasia of venous trunks, aneurysms, and avalvulia. Diagnosis was made by one or more of the following methods: Doppler scanning, duplex scanning, plethysmography, computerized tomography, magnetic resonance imaging, and angiography.

RESULTS

At least one anomaly of the deep venous system was present in 47% of the congenital vascular malformations of venous predominance reviewed. Phlebectasia was recorded in 36% of the cases, and aplasia or hypoplasia of deep venous trunks was observed in 8% of the cases. Venous aneurysms also were present in 8% of the cases; avalvulia was recorded in 7% of the cases.

CONCLUSION

Anomalies of the deep venous system occur in almost one half of congenital vascular malformations of venous predominance. The most common is the relatively innocuous phlebectasias that occur in over one third of cases. Aplasia/hypoplasia, venous aneurysms, and avalvulia were less frequent, each less than 10%; but failure to detect the latter three anomalies may lead to serious therapeutic errors.

MR assessment of the extremity veins

This article provides an overview of the technique of magnetic resonance venography (MRV) and its relative value in the diagnostic work-up of suspected lower or upper extremity venous thrombosis. MRV is accurate for diagnosis or exclusion of deep vein thrombosis. MRV should be considered complimentary, in many instances, to the less expensive modality of venous sonography. It is the complimentary use of magnetic resonance techniques at the level of the pelvis and the mediastinum that offers the greatest cost benefit as part of an incremental strategy for the work-up of patients presenting with lower or upper extremity swelling.

Absence of flow in ovarian vein by time-of-flight magnetic resonance angiography without evidence of thrombosis

A case of absent flow in the left ovarian vein was diagnosed on time-of-flight (TOF) magnetic resonance angiography (MRA) while investigating for pelvic vein thrombosis in a 53-year-old female. This appearance should not be misdiagnosed as a sign of ovarian vein occlusion or thrombosis. Magnetic resonance imaging (MRI) is a sensitive noninvasive imaging modality in such a clinical setting. Familiarity with the potential pitfalls of different MRA techniques is essential for correct diagnosis. A review of different MRA techniques in evaluation of pelvic venous thrombosis is presented.

Body magnetic resonance angiography and its effect on the use of alternative imaging--experience in 1026 patients

Time-of-flight magnetic resonance (MR) angiography has been described for numerous applications but the number of patients described in published reports is usually relatively small. There is little information concerning the general utility of MR angiography in the body, outside the cranial circulation, or its effect on use of other imaging studies. Utilization of two-dimensional (2D) time-of-flight MR angiography over a 3 year period was reviewed to determine its accuracy and impact on other imaging modalities. Cranial and cardiac studies were excluded. Correlation was made with alternative imaging and surgical findings. Between January 1990 and December 1992 2D time-of-flight MR angiography was used to examine 1026 patients. MR angiography was used most frequently to examine the venous system. There was a slight reduction in the use of alternative imaging with two exceptions. When chest MR venography was performed, alternative imaging was completely abolished. Also, contrast portal venography was virtually eliminated. Five errors (0.2% of total MR angiography examinations) were recorded. Time-of-flight MR angiography, especially MR venography, is accurate and can replace contrast venography for abdominal and thoracic applications. Cost and limited availability means that other imaging, usually ultrasound, often precedes MR angiography.

Angiomagnetic resonance imaging of iliofemorocaval venous thrombosis

Although magnetic resonance imaging has been proposed for the diagnosis of deep venous thrombosis (DVT), its role in diagnostic strategy remains to be defined. We compared prospectively magnetic resonance angiography (MRA) with two-dimensional time-of-flight with contrast venography (CV) and colour duplex sonography (CDS) in 25 patients with DVT of the pelvis confirmed by CV. All patients were examined by CV (gold standard) and MRA and 17 by CDS. These studies were compared for DVT diagnosis in the pelvis and inferior vena cava and analysis of thrombotic spread. MRA was positive in 25 patients whose DVT was diagnosed by CV (100% sensitivity). MRA sensitivity and negative predictive value were 100%, specificity 98.5% and positive predictive value 97.5% for the diagnosis of thrombosis at each anatomic level. There were discrepancies between MRA and CV (2 false-positive results for 2 venous segments) and between CDS and CV (2 false-positive and 3 false-negative results). CV was uninterpretable for 8.8% of segments and CDS was often technically limited to the pelvic level, whereas all venous segments explored were analysable in MRA. MRA gave excellent results for positive diagnosis and DVT spread. MRA is a potentially valuable technique for assessing iliofemorocaval venous thrombosis.

MR imaging in inferior vena cava thrombosis

PURPOSE

To prospectively evaluate the efficacy of MR imaging in inferior vena cava (IVC) thrombosis; to differentiate acute from non-acute thrombus, and to identify the presence of changes in the morphology and signal intensity during medical treatment.

METHODS AND MATERIALS

Seventeen patients with suspected IVC thrombosis underwent 30 MR examinations. The IVC thromboses were subdivided into two groups (acute and non-acute) according to onset of clinical symptoms. MR imaging of the IVC was analyzed and when an IVC thrombus was identified, a qualitative and quantitative assessment of the thrombus on spin-echo sequences with magnitude and phase reconstruction was performed to evaluate the relationship between signal intensity and the time elapse since the onset of clinical symptoms. Venography and/or CT scan proof was available in all cases.

RESULTS

IVC thrombus was correctly identified in 19 MR examinations which showed the size, localization and the degree of lysis during follow-up. No differences were found in the signal intensity of the thrombus related to time. The pattern of the signal intensity was homogeneous in six (86%) acute thrombus and heterogeneous in nine (75%) thrombus of more than 1 week duration. A significant statistical relationship (P < 0.01) existed between the thrombus age and differences in the pattern of signal intensity.

CONCLUSIONS

MR imaging is accurate to assess the localization and size of IVC thrombus, similar to the imaging techniques of reference. In addition, MR also provides useful information about the age and the morphological variations of thrombus during medical treatment.

MRI of Budd-Chiari syndrome

A retrospective study was undertaken to reassess the various magnetic resonance imaging (MRI) features of Budd-Chiari syndrome (BCS). MRI examinations of 22 patients with pathologically confirmed BCS were studied. Spin-echo (SE) T1- (TR = 300-450 ms/TE = 12-15 ms), and SE T2-weighted (TR = 1600-2000 ms/TE = 30-60/90-120 ms) MRI images were obtained in all patients. Gradient-recalled-echo (GRE) images (TR = 7-60 ms/TE = 3-19 ms, flip angle = 10-40 degrees) were obtained in 14 patients. MRI showed thrombosis of three or two hepatic veins in 19 (86%) and 3 (14%) patients, respectively. Spontaneous intrahepatic anastomoses was depicted in five (23%) patients. Ascites appeared in 15 patients (68%). Thrombosis or external compression of the inferior vena cava (IVC) by an enlarged caudate lobe was depicted in six (27%) and five (23%) patients, respectively. Prominent azygos and hemiazygos veins were demonstrated in seven (32%) patients (six of whom had thrombosis of the IVC). MRI showed hepatomegaly in all patients and enlarged caudate lobe in 18 (82%) patients. SE T1- and SE T2-weighted MRI images revealed inhomogeneous signal intensity of hepatic parenchyma in 14 (64%) patients. SE T1- and SE T2-weighted MRI images showed homogeneous signal intensity of hepatic parenchyma in eight (36%) patients. Our results demonstrate that BCS displays various features on MRI images, and such information is important for diagnosis.

A comparison of MR and duplex Doppler ultrasound for vascular assessment prior to orthotopic liver transplantation

A prospective blinded comparison of duplex Doppler ultrasound (DDU) and a magnetic resonance angiography (MRA) 2-D time-of-flight technique was performed to assess the hepatic vasculature in 23 adult patients referred for orthotopic liver transplantation. Both techniques confirmed patency of the inferior vena cava in all patients, demonstrated a complete portal vein occlusion in one patient, and accurately defined the vascular and organ anatomy in a patient with situs inversus. The results were confirmed at surgery in 18 of the patients who have subsequently undergone liver transplantation. In one patient a partial portal vein thrombosis was found at surgery which was not detected by either imaging technique. MRA was more sensitive overall in detecting porto-systemic collaterals (31 locations in 17 patients) compared with ultrasound (24 locations in 17 patients), although ultrasound detected more patients with recanalized para-umbilical veins (DDU: 10 patients; MRA: 8 patients). These results indicate that a simple MRA technique can equal duplex Doppler ultrasound for the non-invasive assessment of patency of the hepatic vasculature and should be considered when DDU examination is equivocal or technically inadequate. MRA may provide additional information on the presence and size of porto-systemic collaterals which may be of value in monitoring portal hypertension.

Mesoinnominate shunt for the treatment of Budd-Chiari syndrome: evaluation with multimodality imaging

The construction of a mesoinnominate shunt between the superior mesenteric vein and the left innominate vein is a recent surgical procedure for the treatment of Budd-Chiari syndrome with vena caval obstruction. The purpose of this study was to determine the role of the different imaging modalities for the follow-up of mesoinnominate shunts. Doppler US (n = 32), and MR imaging examinations (n = 32) were prospectively performed in 10 patients with mesoinnominate shunts. Shunt patency or thrombosis was confirmed with angiography (n = 32) and transhepatic portography with pressure measurement (n = 6). For each follow-up evaluation, all examinations were performed within 4 days. Shunt patency was correctly demonstrated in 28/28 cases with Doppler US, CT and MR imaging. Shunt thrombosis was correctly demonstrated in 4/4 cases with Doppler US, CT and MR imaging. Since Doppler US, CT and MR imaging have the same accuracy for diagnosing mesoinnominate shunt patency and detecting thrombosis, our study suggests that redundant screening methods can be avoided. Doppler US is accurate enough and should be the preferred technique in the evaluation of mesoinnominate shunts.