Collateral pathways in superior vena caval obstruction as seen on gamma images

The collateral pathways, known from contrast studies to take over the drainage of blood from the various parts of the body when the superior vena cava or its major tributaries are occluded because of disease, can easily be demonstrated with equal clarity (except for the vertebral plexus pathway) by radionuclides. The failure to delineate the vertebral plexus pathway is felt to lie in the close anatomical relationship between the vertebral plexus and the vertebrae, which cause attenuation of the emerging photons. Because of the existing anastomotic channels and their anatomical direction, location and distribution of the individual collateral pathways are individually identifiable. The site/level, extent, degree, and probable duration of occlusion directly affect the degree and extent of the collaterals that subsequently develop. In 20 of 49 abnormal radionuclide superior venacavograms, incidental but abnormal imaging features not ascribable to caval obstruction or syndrome were noted. These included persistent left superior vena cava, aortic aneurysm, pericardial effusion, and disparity in pulmonary perfusion.     

Collateral pathways observed by radionuclide superior cavography in 70 patients with superior vena caval obstruction.

Schematic representations of collateral pathways that have developed in association with superior vena caval obstruction have been established in studies using radionuclide superior cavography (RNSC). However, these were hampered by the poor resolution of earlier scintillation cameras. Using a modern scintillation camera, we performed RNSC in 70 patients with obstruction of the superior vena caval system, and examined the differences in collateral pathways in the presence or absence of obstruction of the azygos vein. RNSC visualized the site of obstruction and collateral pathways far more readily than in prior studies. When the orifice of the azygos vein was not obstructed, collateral flow drained into the azygos system. When it was obstructed, however, the collaterals drained into the inferior vena caval system. An important collateral pathway comprising the contralateral brachiocephalic vein and the jugular venous arch was also found, which has not previously been reported. Our diagrams of collateral circulation may provide a means of determining the site of obstruction in the superior vena caval system by RNSC.     

Cavo-portal shunting in superior and inferior vena caval obstruction

Focal radionuclide accumulation of Tc-99m sulfur colloid (SC) and tc-99m macroaggregated albumin (MAA) in the liver has been reported in both inferior and superior vena caval obstruction. We studied a patient with uniform radionuclide accumulation of Tc-99m MAA in the liver during lung scintigraphy. In this patient, both the superior vena cava (SVC) and the inferior vena cava (IVC) were obstructed. Most of the systemic venous return appeared to be passing through the liver on its way to the heart, through the anastomoses between the systemic veins and the portal vein. The the best of our knowledge, uniform hepatic uptake in vena caval obstruction is not reported in the literature.     

The value of radionuclide venography in superior vena caval obstruction

A prospective study on 27 patients with suspected obstruction of the superior vena cava (SVC) and 10 control patients with no known chest disease was undertaken to determine the value of radionuclide venography in aiding diagnosis and treatment of the condition. The technique proved simple, safe and non-invasive and could rapidly confirm or exclude the diagnosis when in doubt. In addition, the technique had a role in radiotherapy planning, highlighting unsuspected superior mediastinal disease not visible on the chest radiograph. However, follow-up post-treatment scans were of little help due to the good clinical markers of obstruction of the SVC. The normal and abnormal scan appearances are described.     

Superior vena caval obstruction: detection using CT

A review of 210 chest computed tomographic (CT) examinations demonstrating upper chest masses revealed 16 cases of superior vena caval obstruction (SVCO); 11 of these were clinically occult. Two of the occult cases subsequently became clinically evident. Contrast-enhanced chest CT permits the diagnosis of clinically occult SVCO and should be considered in patients with upper chest masses, even in the absence of any physical signs of SVCO.     

Left ventricular pseudoaneurysm causing superior vena caval obstruction and effusive-constrictive pericarditis

A diabetic woman with a silent myocardial infarction on clinical and electrocardiographic criteria presented with findings on physical examination of superior vena caval obstruction and effusive-constrictive pericarditis. A left ventricular posterior wall pseudoaneurysm and intrapericardial hematoma were found, with extrinsic compression of the right atrium. The diagnosis was first suspected by radionuclide imaging and confirmed by contrast angiography and surgery.     

Unexpected demonstration of superior vena caval obstruction in third trimester lung imaging

A large focus of liver activity was seen after the injection of Tc-99m macroaggregated albumin (MAA) in a pregnant patient thought to have pulmonary embolism (PE). The correct diagnosis of superior vena caval (SVC) obstruction led to an immediate cesarean section, CT of the chest and abdomen, open lung biopsy of a mediastinal mass, and radiation therapy for the lymphoma with pericardial invasion, all within 24 hours of presentation. The next day, an in vitro labeled Tc-99m red blood cell (RBC) angiogram was performed, which documented collateral flow from the SVC obstruction to the abdomen and filling of the right ventricle via the liver, presumably through reopened channels of the umbilical vein.     

Metastatic thyroid carcinoma causing superior vena caval obstruction diagnosed on I-131 scan

An 80-year-old woman was referred for a painless mass arising in right side of her neck of 4 months' duration. Ultrasound revealed a multinodular goiter, but cytology confirmed a follicular carcinoma. Thyroid function was normal. Total thyroidectomy was performed with evidence of tumor infiltration into the strap muscles extending up to the right submandibular gland and right internal jugular vein, which was completely occluded. Radioiodine was considered as the treatment of choice postoperatively. This is an unusual case of SVC obstruction caused by tumor embolus diagnosed on I-131 scan.     

Diffuse uptake of osteotropic radionuclide in the breast secondary to superior vena caval obstruction

Osteotropic radionuclide uptake in breast tissue has been described in a variety of benign and malignant lesions. The authors present a case of diffuse unilateral breast uptake secondary to neoplastic obstruction of the right brachiocephalic vein and superior vena cava. Following radiotherapy, the vascular obstruction resolved and the breast uptake was no longer observed.     

Scintigraphy compared to other imaging modalities in benign superior vena caval obstruction accompanying fibrosing mediastinitis

Evaluation of a 50-year-old man with benign but insidious development of chronic superior vena caval obstruction secondary to old pulmonary histoplasmosis is presented. The radiologic evaluation was done in stages to exclude involvement of other disease. Nuclear scintigraphy revealed the superior vena caval obstruction. Anatomical features are compared to dynamic findings using contrast venography, computed tomography, and magnetic resonance imaging to differentiate pulmonary vascular compression from neoplasm and pulmonary embolism. The combination of modalities reveals the character and extent of pathology without extensive interventional procedures.     

Bronchogenic cyst causing superior vena cava obstruction: CT appearance

The CT appearance of bronchogenic cysts is well known. In addition, CT is useful in evaluating cases of suspected superior vena cava (SVC) syndrome. Although most cases of SVC syndrome are caused by malignant diseases, certain benign disorders such as granulomatous infections may be the underlying cause. A case of a bronchogenic cyst causing SVC occlusion is presented here.