The "aortic nipple" as a sign of impending superior vena caval syndrome

Acute hemodialysis catheter follows the path of least resistance

The placement of large bore double-lumen catheters for hemodialysis (HD) is one of the most frequent procedures performed in HD patients. However, these procedures are associated with complications, the most common being catheter malposition. In this context, catheter deviation to the left superior intercostal vein (LISV) is a very uncommon malposition, which must be differentiated from intrathoracic extravascular catheter lodgment. We report a case of an adult male patient on hemodialysis who presented with a thrombosed arteriovenous fistula and requiring urgent HD. His past medical history included hemophilia, allergy to contrast media, and multiple previous central vein catheterizations. A non-tunneled HD catheter was placed without any difficulty in the left internal jugular vein. However, the arterial lumen failed to pull any blood with free flow in the venous lumen. A chest X-ray revealed a surprising finding. The malpositioned catheter was removed successfully without any complications.

(Mis)placed central venous catheter in the left superior intercostal vein

Background

Chest X-ray is routinely performed to check the position of the central venous catheter (CVC) inserted through the internal jugular or subclavian vein, while the further evaluation of CVC malfunction is usually performed by contrast venography. In patients with superior vena cava obstruction, the tip of the catheter is often seen in collateral mediastinal venous pathways, rather than in the superior vena cava. In such cases detailed knowledge of thoracic vessel anatomy is necessary to identify the exact location of the catheter.

Case report.

We report a case of 32-year-old female patient with relapsing mediastinal lymphoma and previous superior vena cava obstruction with collateral azygos-hemiazygos venous pathways. The patient had CVC inserted through the left subclavian vein and its position was detected by CT to be in the dilated left superior intercostal vein and accessory hemiazygos vein. Considering that dilated accessory hemiazygos vein can tolerate infusion, the CVC was left in place and the patient had no complaints related to CVC (mal)position. Furthermore, we present anatomical and radiological observations on the azygos-hemiazygos venous system with the special emphasis on the left superior intercostal vein.

Conclusions

Non-contrast CT scans can be a valuable imaging tool in the detection of the CVC position, especially in patients with renal insufficiency and contrast media hypersensitivity.

The radiographic findings of fibrosing mediastinitis

We retrospectively reviewed the radiographic findings of fibrosing mediastinitis (FM) in 33 patients. Imaging studies included chest radiographs, computed tomographic scans, magnetic resonance imaging examinations, esophograms, ventilation perfusion scans, angiograms, and venograms. Findings include bronchial narrowing in 11 patients (33 percent), pulmonary artery obstruction/narrowing in 6 patients (18 percent), esophageal narrowing in 3 patients (9 percent), and superior vena cava obstruction/narrowing in 13 patients (39 percent). Two distinctly different radiographic patterns were identified: a localized pattern seen in 27 patients (82 percent) that frequently contained calcification and a diffuse pattern seen in 6 patients (18 percent) that did not contain calcification. The localized pattern is most likely due to histoplasmosis and does not show radiographic evidence of improvement with steroid therapy. The diffuse pattern may more likely be truly idiopathic or of a noninfectious etiology. Several patients with the diffuse pattern showed radiographic evidence of improvement with steroid therapy.

MRI visualization of the aortic nipple

The aortic nipple, a small "pseudotumor" adjacent to the aortic arch, is the left superior intercostal vein. In our series of 40 patients it was demonstrated in six; all had a right upper thoracic mass and four had a superior vena caval syndrome. Coronal magnetic resonance images (MRI) of the thorax were superior to all other imaging methods in demonstrating the nipple. It is concluded that in patients with masses in the right upper chest, coronal MR chest examinations are valuable in demonstrating an aortic nipple, a sign of impending present superior vena caval or innominate vein obstruction.