RADIOLOGY CORNER

Military Medicine, Mar 2008 by Peterson, P Gabriel, Ronsivalle, Joseph, Folio, Les

Answer to last month's radiology case and image:

Case #21: Superior Vena Cava (SVC) Syndrome

(Case # 22 appears at the end of this article)

History

SVC syndrome results from increased hydrostatic pressure in the venous system distal to the SVC, through which blood flow has been diminished or obstructed. William Hunter, a Scottish physician who gained notoriety with regard to his description of aneurysms [1], described the first case of SVC syndrome in 1757, which was caused by a syphilitic aortic aneurysm [2]. In fact, for many years aortic aneurysms were thought to be one of the more common etiologies. As the antibiotic-era began and more cases were compiled, however, extrinsic compression from malignancy was shown to be a far more prevalent cause. Current analysis has revealed that 80-97% of cases are due to extrinsic, malignant processes with bronchogenic lung cancer and lymphoma accounting for most [3]. Intraluminal processes, such as venous thrombosis, account for the remainder of cases [4].

Summary of Findings:

Frontal chest radiograph (Figure 1) demonstrates left mediport placement with catheter tip in the region of the left brachiocephalic vein. Normally, the tip should lie in the SVC. It is also notable for a widened superior mediastinum (arrow), and the absence of a right breast shadow consistent with prior mastectomy. Note the metallic vascular clips from lymph node dissection in the right axillary region (circled). The axial CT image (figure 2) through the chest after IV contrast administration demonstrates a homogeneous filling defect in the SVC. The catheter tip (white arrow) is visible within the filling defect. Contrast venography (figure 3) shows thrombus.

Diagnosis

Superior Vena Cava (SVC) Syndrome

This patient was successfully treated with tissue plasminogen activator (tPA) via infusion catheter in addition to balloon angioplasty and, ultimately, mechanical thrombectomy. see the on-line full text version for a complete review with venogram images. Patients with SVC syndrome most often present with dyspnea, cough, head 'fullness,' and flushing. Physical exam may reveal dilated superficial veins on the superior chest wall with or without upper extremity and facial edema. Chest radiography may suggest the diagnosis by revealing a widened superior mediastinum [4], however computed tomography (CT) and venography are best for diagnosing the etiology and extent of obstruction [5,6]. CT criteria require: 1) decreased or absence of opacification of central venous structures inferior to obstruction AND 2) opacification of collateral venous routes. Collateral routes include the azygos system, which is the most commonly dilated, the vertebral venous system, the internal mammary vein, and the lateral thoracic vein [7]. MR angiography is appropriate for patients with contraindications to iodinated contrast [8]. Treatment is aimed at the underlying cause. In the case of intrinsic thrombosis, thrombolytic therapy, as well as tPA are usually successful if employed within 5 days of symptom onset [9].

CASE # 22

The answer to this case will appear in the next issue of Military Medicine

History: A 32 year old male active duty Air Force Captain presents to the Family Medicine clinic with a 2 month history of left hip and groin pain as well as left hip stiffness. There is no history of trauma, though the patient does report a recent increase in his physical activity.

What is (are) the finding(s)? What is the differential diagnosis? Best diagnosis?

References:

1. Friedman SG, M.D. "A History of Vascular Surgery." 2nd Ed. Blackwell Publishing, 2005; pp 31-34.

2. Hunter W. "The History of an Aneurysm of the Aorta with some remarks on Aneurysms in General." Med Observ lnq 1757; 1:323-57.

3. Abner A. "Approach to the patient who presents with superior vena cava obstruction. (Multimodality Therapy of Chest Malignancies: Proceedings of a Harvard Medical School Symposium)." Chest. Apr. 1993; 103(4): 394S-397S.

4. Parish JM, et al. "Etiologic considerations in Superior Vena Cava syndrome." Mayo Clinic Proceedings. Jul. 1981; 56(7):407-13.

5. Qanadi SD, Hajjam ME, Bruckert F, et al. "Helical CT phlebography of the Superior Vena Cava: Diagnosis and Evaluation of venous obstruction." AJR. May 1999; 172(2): 1327-33.

6. Bechtold RE, Wolfman NT, Karstaedt N, Choplin RH. "Superior Vena Cavai Obstruction: Detection using CT." Radiology. Nov. 1985; 157(2):485-7.

7. Engel IA, Auh YH, Rubenstein WA, et al. "CT Diagnosis of Mediastinal and Thoracic inlet venous obstruction." AJR. Sept. 1983; 141(1):521-6.

8. Finn JP, Zisk JH, Edelman RR, et al. "Central venous occlusion: MR angiography." Radiology. Apr. 1993; 187(1 ):245-51.

9. Gray BH, OHn JW, Graor RA, et al. "Safety and Efficacy of Thrombolytic Therapy for SVC syndrome." Chest. Jan. 1991; 99(1):54-9.

Contributors: CPT P. Gabriel Peterson, MC, USA1; Joseph Ronsivalle, D.O.2; COL Les Folio, MC, USAF1,3

1 Walter Reed Army Medical Center, 2 Madigan Army Medical Center, 3 Uniformed Services University of the Health Sciences.