Cavoportal collateral pathways in vena cava obstruction: imaging features

CT Findings of Azygos Venous System: Congenital Variants and Acquired Structural Changes

The azygos venous system is a crucial conduit of the posterior thorax and potentially vital collateral pathway. However, it is often overlooked clinically and radiologically. This pictorial essay reviews the normal azygos venous anatomy and CT findings of congenital variations and structural changes associated with acquired pathologies.

Lesion or Pseudolesion? A Comprehensive Description of Perfusion-Based Liver Alterations on Contrast-Enhanced Computed Tomography and Literature Review

ABSTRACT

Pseudolesions on contrast-enhanced computed tomography represent a diagnostic challenge for radiologists because they could be difficult to distinguish from true space-occupying lesions. This article aims to provide a detailed overview of these entities based on radiological criteria (hyperattenuation or hypoattenuation, localization, morphology), as well as a brief review of the hepatic vascular anatomy and pathophysiological process. Relevant examples from hospital case series are reported as helpful hints to assist radiologists in recognizing and correctly diagnosing these abnormalities.

Iatrogenic superior vena cava syndrome with concomitant deep vein thrombosis of azygos and hemiazygos veins

Iatrogenic superior vena cava syndrome (SVCs) represents an emergent diagnostic entity and its correlation with deep vein thrombosis is extremely rare. Recently, the increased use of indwelling lines, pacemakers and intracardiac devices has led to more cases of SVC syndrome also associated with a higher frequency of DVT. We report an unusual complication in a 74-year-old female, who has been undergoing hemodialysis via CVC for 14 years, who referred at our Emergency Department complaining of shortness of breath, headache, face and neck swelling. She underwent chest Computed Tomography Angiography (CTA), that showed a thrombus extending from the superior vena cava to the azygos and hemiazygos veins. Acute SVCs should be suspected in emergency settings in symptomatic patients with indwelling central lines, catheters and pacemakers. CTA represents an accurate and quick imaging modality for the diagnosis and the assessment of the extension of the thrombus.

Changes of the hepatic subcapsular blood flow in a case of high-grade retroperitoneal liposarcoma: what to expect?

Changes of the hepatic subcapsular blood flow with the early appearance of hypervascularity near the falciform ligament are rare radiologic findings. They present most frequently in cases of superior vena cava (SVC) obstruction and are related to the recruitment of the cavo-mammary-phrenic-hepatic-capsule-portal and the cavo-superficial-umbilical-portal pathways. We present the case of a 52-year-old female patient with an highly aggressive retroperitoneal liposarcoma with SVC obstruction caused by external compression due to a mediastinal metastatic mass. The patient exhibited no symptoms of SVC obstruction due to the collateral cavo-portal pathways.

Adaptation of the hepatic transudation barrier to sinusoidal hypertension

The role of the hepatic transudation barrier in determining ascites volume and protein content in chronic liver disease is poorly understood. Therefore, the purpose of the present study was to characterize how chronic sinusoidal hypertension impacts hepatic transudation barrier properties and the transudation rate. The suprahepatic inferior vena cava was surgically constricted, and animals were exposed to either short-term (SVH; 2-3 wk) or long-term venous hypertension (LVH; 5-6 wk). Compared with SVH, LVH resulted in lower peritoneal fluid pressure, ascites volume, and ascites protein concentration. The transudation barrier protein reflection coefficient was significantly higher, and the transudation barrier hydraulic conductivity, transudation rate, and transudate-to-lymph protein concentration ratio were significantly lower in LVH animals compared with SVH animals. The sensitivity of transudation rates to acute changes in interstitial fluid pressures was also significantly lower in LVH animals compared with SVH animals. In contrast, there was no detectable difference in hepatic lymph flow rate or sensitivity of lymph flow to acute changes in interstitial fluid pressures between SVH and LVH animals. Taken together, these data suggest that decreased hepatic transudation barrier permeability to fluid and protein and increased reflection coefficient led to a decrease in the hepatic contribution to ascites volume. The present work, to the best of our knowledge, is the first to quantify an anti-ascites adaptation of the hepatic transudation barrier in response to chronic hepatic sinusoidal hypertension.

CT of the paraumbilical and ensiform veins in patients with superior vena cava or left brachiocephalic vein obstruction

The purpose of this study was to elaborate on the anastomoses between the paraumbilical and systemic veins, particularly the ensiform veins. The connections with the ensiform veins have received little attention in the anatomical and radiological literature, and remain incompletely described. Too small to be reliably traced in normal CT scans, the paraumbilical veins can dilate in response to increased blood flow from systemic veins in superior vena cava obstruction (SVCO), allowing a study of their arrangement and connections. Collateral paraumbilical veins were therefore analyzed retrospectively in 28 patients with SVCO using CT. We observed inferior and superior groups of collateral vessels in 23/28 (82%) and 17/28 (61%) patients, respectively. Inferior veins ascended towards the liver and drained into portal veins (19/28, 68%) or the umbilical vein (8/28, 29%); superior veins descended and drained into portal veins. The inferior veins (N = 27) could be traced to ensiform veins in almost all of the cases (26/27, 96%), and a little over half (14/27, 52%) were also traceable to subcutaneous and deep epigastric veins. They were opacified by ensiform (25/27, 93%), deep epigastric (4/27, 15%) and subcutaneous (4/27, 15%) veins. The superior veins (N = 17) were supplied by diaphragmatic (13/17, 76%) and ensiform veins (4/17, 24%); the diaphragmatic veins were branches of collateral internal thoracic, left pericardiacophrenic and anterior mediastinal veins. Collateral ensiform veins were observed in 22 patients and anastomosed with internal thoracic (19/22, 86%), superior epigastric (9/22, 41%), diaphragmatic (4/22, 18%), subcutaneous (3/22, 14%) and anterior mediastinal veins (1/22, 5%). These observations show that the paraumbilical veins communicate with ensiform, deep epigastric, subcutaneous and diaphragmatic veins, joining the liver to the properitoneal fat pad, anterior trunk, diaphragm and mediastinum. In SVCO, the most common sources of collateral flow to the paraumbilical veins are the ensiform and diaphragmatic branches of the internal thoracic veins.

Hepatic Pseudolesion due to "Vein of Sappey" in Superior Vena Cava Syndrome

One of the common causes of superior vena cava (SVC) syndrome is malignancy of the lung. The invasion of SVC leads to opening of the various venous channels for continuation of the blood flow from upper extremity and proximal trunk and finally draining into right atrium. Vein of Sappey is one of these channels and it causes focal striking enhancement in segment IV of the liver on arterial phase of contrast computed tomography (CT). This enhancement causes diagnostic difficulty and unnecessary biopsy due to misinterpretation of it as a secondary from lung cancer. Awareness and accurate diagnosis can avoid further examination in such patients. It can also provide an idea of a more proximal major thoracic vessel obstruction if first detected on CT of the abdomen (contrast).

Pseudolesion in segment IV A of the liver from vein of Sappey secondary to SVC obstruction

Pseudolesions in the liver are caused by unusual/altered hemodynamics of the liver and can be confused with a true hepatic mass. In superior vena cava (SVC) obstruction. there is recruitment of the cavo-mammary-phrenic-hepatic-capsule-portal pathway. and the venous blood follows the internal mammary vein, the inferior phrenic vein, the hepatic capsule veins, and the intrahepatic portal system. causing a hypervascular pseudolesion in segment IV A of the liver. Recognizing the classic appearances of this hypervascular pseudolesion from the vein of Sappey in a CT study of the abdomen has prognostic implications in directing further evaluation of the chest for SVC obstruction. We present a case of a 54-year-old HIV-positive male smoker in whom identification of the hypervascular pseudolesion from the vein of Sappey on the abdominal CT led to the diagnosis of SVC syndrome.

Downhill esophageal varices: a prevalent complication of superior vena cava obstruction from benign and malignant causes

OBJECTIVE

Downhill esophageal varices (DEV) usually develop secondary to superior vena cava (SVC) obstruction. Downhill esophageal varices have been less well characterized compared to uphill varices. The aim of the study was to characterize the anatomy and etiology of DEV by contrast-enhanced computed tomography.

METHODS

Patients with SVC obstruction were included in the study. Downhill esophageal varices were defined as discrete esophageal submucosal or mucosal vessels. Ten random computed tomographic scans were assessed as controls.

RESULTS

Downhill esophageal varices were seen in 11 of 36 patients. Three types of varices were observed. Between 1 and 6 varices were seen in each patient with a diameter of 1 to 5 mm.

CONCLUSIONS

Downhill esophageal varices can be seen in 30% of patients with SVC obstruction. They have several patterns and are mostly systemic-to-systemic collaterals. The most common etiology associated with DEV is renal failure. Downhill esophageal varices are of small caliber, this may in part account for less frequent bleeding compared to uphill varices.

Beyond PET/CT in Hodgkin lymphoma: a comprehensive review of the role of imaging at initial presentation, during follow-up and for assessment of treatment-related complications

Objective

The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL). PET/CT is the imaging modality of choice in the management of Hodgkin’s lymphoma (HL). However, imaging modalities other than PET/CT such as plain radiographs, ultrasound, CT, MRI and nuclear imaging can help in various stages of clinical management of HL, including the initial workup and post-treatment surveillance. Both CT and MRI help in detecting recurrences, treatment-related pulmonary, cardiovascular and abdominal complications as well as second malignancies. Familiarity with expected post-treatment changes and complications on surveillance images can help radiologists guide patient management. The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL).

Main Messages

• Surveillance of HL patients is usually performed with plain radiographs and CT.

• Follow-up imaging can depict normal post-treatment changes or treatment-related complications.

• Imaging is important for the timely detection of second malignancies in HL patients.

The azygos vein pathway: an overview from anatomical variations to pathological changes

The azygos venous system represents an accessory venous pathway supplying an important collateral circulation between the superior and inferior vena cava. The aim of this article is to revise the wide spectrum of changes ranging from normal to pathological conditions involving the azygos system. Teaching points • The azygos vein is a collateral venous pathway, becoming a vital shunt if major pathways of venous return are obstructed. • In azygos continuation, the azygos vein becomes significantly enlarged due to inferior vena cava interruption. • Fibrosing mediastinitis is an underestimated acquired disorder. • Fibrosing mediastinitis induces a variable engorgement of collateral veins. • Fibrosing mediastinitis leads to superior vena cava syndrome.

The azygos system as a rare alternative for chronic indwelling catheters placement

Chronic indwelling catheters are plagued with a high rate of complications, including infection, central venous occlusion, or thrombosis. When direct access to the superior or inferior vena cava is not possible, venography may identify alternatives that might be viable with current endovascular techniques. This case report describes the successful placement of a tunneled catheter for total parenteral nutrition in the azygos arch through a small collateral vein from the left jugular vein in a patient with no other alternatives because of superior vena cava occlusion and inferior vena cava thrombophlebitis.

Imaging the inferior vena cava: a road less traveled

A broad spectrum of congenital anomalies and pathologic conditions can affect the inferior vena cava (IVC). Most congenital anomalies are asymptomatic; consequently, an awareness of their existence and imaging appearances is necessary to avoid misinterpretation. Imaging also plays a central role in the diagnosis of Budd-Chiari syndrome secondary to membranous obstruction of the intrahepatic IVC. Primary malignancy of the IVC is far less common than intracaval extension of malignant tumors arising in adjacent organs, and imaging can accurately help determine the presence and extent of tumor thrombus, information that is crucial for surgical planning. However, the radiologist should be aware that artifactual filling defects at computed tomography and magnetic resonance imaging can mimic true thrombus in the IVC and must be able to differentiate true from pseudo filling defects. Other imaging findings such as flat IVC and early enhancement of the IVC are useful in limiting the differential diagnosis. Familiarity with the imaging features of the various congenital and pathologic entities that can affect the IVC is paramount for early diagnosis and management.

[Abnormality of hepatic perfusion secondary to superior vena cava obstruction: three case reports]

The aim of this study was to evaluate the altered flow dynamics of liver perfusion that can be observed during superior vena cava obstruction. Through the description of three case reports of patients with SVC obstruction, the authors discuss the different collateral pathways used that result in systemic portal venous shunting creating this altered flow dynamics and their appearance in computed tomography.

Portal flow into the liver through veins at the site of biliary-enteric anastomosis

The aim of this study was to establish the role played by jejunal veins in hepatopetal flow after biliary-enteric anastomosis and to evaluate the helical CT features of hepatopetal flow through the anastomosis. We retrospectively analyzed helical CT images of the liver in 31 patients with biliary-enteric anastomosis who underwent hepatic angiography with (n=13) or without (n=18) CT arterial portography within 2 weeks of the CT examination during the last 4 years. Arterial portography showed hepatopetal flow through small vessels located (communicating veins) between the elevated jejunal veins and the intrahepatic portal branches in two (9%) of 22 patients with a normal portal system. Helical CT showed focal parenchymal enhancement around the anastomosis in these two patients. All nine patients with extrahepatic portal vein occlusion (100%) had hepatopetal flow through the anastomosis, and four of the nine had decreased portal flow. CT revealed small communicating veins in two of these four patients. In five patients with normal portal perfusion despite extrahepatic portal vein occlusion, CT detected dilated communicating veins and elevated jejunal veins. The presence of communicating veins and/or focal parenchymal enhancement around the anastomosis indicates hepatopetal flow through the elevated jejunal veins.

Unusual hemodynamics and pseudolesions of the noncirrhotic liver at CT

Recognition of pseudolesions of the liver at computed tomography (CT) is important because of their close resemblance to primary liver cancers or metastases. Two types of pseudolesion in the noncirrhotic liver include that due to transient extrinsic compression, typically caused by ribs or the diaphragm, and that due to a "third inflow" of blood from other than the usual hepatic arterial and portal venous sources: the cholecystic, parabiliary, or epigastric-paraumbilical venous system. Although the location of both types of pseudolesion are characteristic, their appearances at CT during arterial portography and CT during selective angiography vary from nonenhanced low-attenuation areas to well-enhanced high-attenuation areas, depending on the amount and timing of the inflow and presence or absence of focal metabolic alteration of the hepatocytes. Radiologists need to understand the underlying mechanism of these pseudolesions to better recognize the wide range of their appearances at CT.

A large pseudolesion in the left lobe of the liver caused by inferior vena caval obstruction secondary to metastatic retroperitoneal lymphadenopathy

A rare case with a large pseudolesion in the left lobe of the liver observed on early phase of incremental dynamic computed tomography (CT) caused by inferior vena caval obstruction is presented. Decreased portal perfusion due to increased volume of systemic venous inflow into the left lobe via paraumbilical venous system may be its underlying hemodynamic change. The etiology of this pseudolesion was successfully confirmed by conventional CT with intravenous contrast medium injection via superficial vein of lower extremity.