The Superior Vena Cava: Conventional Projections

By Benjamin Felsont

A S ALREADY noted, anomalies of the SVC are fairly common and are nicely demon-

mediastinal mass and lead to additional studies and even unnecessary surgery. In my own experi-

strated on CT. I have illustrated them here in conventional frontal projection so that you can suspect or recognize them from the plain films. Figure 1 illustrates double SVC and Fig 2 shows a left SVC entering the left coronary sinus. A left SVC can be recognized on the plain PA tele- roentgenogram as a subtle vertical interface extending caudally from the left clavicle to the heart overlapping or lying just lateral to the aortic knob. This interface vanishes as it approaches the clavicle because of its location in the anterior mediastinum (the cervicothoracic sign’).

From the Department of Radiology, University Hospital, Cincinnati.

fDr Felson died Ott 22, 1988.

Address reprint requests to Benjamin F&on, MD, Department of Radiology, #742, University Hospital, Cin- cinnati, OH 45247.

Another variant of the SVC is idiopathic dila- tation (Fig 3).2 The enlarged vessel may mimic a

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Figl. Two cases of double SVC. (Ai Subtraction bilateral various angiogram. Note the interconnecting v&n. (6) Another

patient. Venous catheterization of heart via the right arm. The catheter her entered the coronary sinus from the right atrium and passes retrograde into the left SVC. W Same patient as (B). Contrast injection into the left innominate vein via the catheter fills the left SVC and coronary sinus.

Seminars in Roentgenology, Vol XXIV, No 2 (April), 1989: pp 9 1-95 91

BENJAMIN FELSON

Fig 1. (Cont’d).

Fig 2. Left SVC en route to the coronary sinus. (Al PA telaroentgenogram. Noto the vartkal intarfaca (white arrow) Lateral to the aortic knob (black arrow). The shadow disappears as it approachas the davii IcMvicathwacic sign’). (81 Venous phase of an angiocardiogram shows contrast filling of the anomalous left cava and its entry into the dilated coronary sinus and right atrium.

SUPERIOR VENA CAVA: CONVENTIONAL PROJECTIONS 93

Fig 3. Idiopathic difatation of the SVC in a young woman. (A) Teleroantgenogram. A right superior mediaatfnal mass is simulated. The shadow, which disappears st the clavicle, decreased with the Valsalva msneuver. (B) Contrast medium injection shows the dilated right SVC.

Fig 4. Jugular lymph sac. This rare anomalous vessel lies at the junction of the thoracic duct and left internal jugular vein. (A) Plain film. A soft tissue mass (arrow) bulges from the left supraclaviou- lar region. It was easily compressible. (B) Brachial venogrsm. Retrograde filling of the sac is shown (arrow).

BENJAMIN FELSON

Fig 4. (Cont’d).

Another congenital aberration you should be aware of, not of the SVC but rather of the innominate venous system, is the jugular lymph sac. This rare anomaly occurs at the junction of the internal jugular vein and subclavian vein, at the site of entry of the thoracic duct.

Its derivation is interesting. The lymphatic vessels embryologically stem from the venous system. Well-formed lymphatic valves prevent reflux of blood into the lymphatics. The only major connection between the two systems retained at birth is the site of entry of the thoracic duct adjacent to the origin of the innom- inate vein. With incompetence or absence of valves at this site, the connection may be wide- open and dilated.

This is called the jugular lymph sac and may be apparent clinically. It is usually found in the left supraclavicular fossa but may be present on the right side instead. It enlarges on Valsalva maneuver. The diagnosis is readily confirmed by either angiography or lymphography (Fig 4).4*5 Jugular lymph sac is usually mistaken for a venous aneurysm and surgically removed, an unnecessary intrusion.6’7

As stated elsewhere in this Seminar, SVC obstruction has many causes. Table 1 is a Gamut listing them.8 I have been surprised at how often patients with complete SVC obstruction show no clinical evidence of the condition. Even with head lowered, the dilated veins and other signs of superior caval obstruction may be lacking. The reason I can make this statement so emphatically is that for many years whenever I have noted a

ence it is encountered most often in teenage girls. The bulging shadow clearly diminishes on the Valsalva maneuver, but remember that a bona fide mediastinal mass may occasionally shift medially with this procedure. It is sometimes necessary to perform CT with contrast enhance- ment to make the diagnosis. The prominent SVC need not be dilated, but merely positioned more to the right than normal.’

Table 1. Superior Vena Caval Obstruction*

Common

1. Aneurysm of aorta or great artery; AV fistula

2. latrogenic fag, pacemaker, central line catheter, ventric-

uloatrial shunt)

3. Lymphadenopathy fesp lymphoma)

4. Mediastinal fibrosis or granuloma (eg, histoplasmosis,

tuberculosis, ergotrates, irradiation, idiopathic)

5. Neoplasm of lung, esophagus, thyroid, or mediastinum

(eg, goiter, superior sulcus carcinoma, cystic hygroma,

thymoma)

Uncommon

1. Axillary vein thrombosis with extension

2. Behcet S

3. Congestive heart failure

4. Idiopathic

5. Mediastinal emphysema, severe: tension pneumothorax

6. Mediastinitis, acute

7. Myxoma of right atrium

8. Osteomyelitis of clavicle

9. Pericarditis. constrictive

10. Pneumoconiosis (coalworkers, silicosis) with conglom-

erate mass

11. Postoperative (eg, cogenital heart disease)

12. Sarcoidosis

13. Thrombosis (eg, polycythemia Vera)

14. Trauma (eg, laceration, transection, mediastinal hema-

tome)

SUPERIOR VENA CAVA: CONVENTIONAL PROJECTIONS

Fig 6. WC obstruction with rib notching. (A) The left eighth rib is ckarty notched (verticalarrow). An enlarge4 brench of the accessory hemiazygos v&n (the superior intercostal vein) juts out from the aodc knob Omrii arrow). ISI Right brad&l venogrem shows obstruction of the SVC (arrow) with extensive collaterals. including a tortuous intercostal vein that is notching the right fdth rib. Autopsy showed fibrocalcific medisstinitis obstructing the superior cava.

right superior mediastinal or RUL mass I begin insist on venous angiography, which to date has my study with a barium swallow, seeking evi- never failed to demonstrate the SVC obstruc- dence of downhill varices. I have demonstrated tion.’ Rib notching from intercostal venous col- them in about half the cases of SVC obstruction. laterals, though rare, is also an indication of SVC If the varices involve the upper esophagus, I obstruction (Fig 5).’

REFERENCES

1. Felson B: Chest roentgenology. Philadelphia: Saunders, 1973

2. Bell MJ, Gutierrez JR, Dubois JJ: Aneurysm of the superior vena cava. Radiology 1970;95:3 17-8

3. Drasin E, Sayre RW, Castellino RA: Non-dilated superior vena cava presenting as a superior mediastinal mass. J Can Assoc Radio1 1972;23:273-4

4. Steinberg I, Watson RC: Lymphangiographic and angiographic diagnosis of persistent jugular lymph sac. New Engl JMed 1966;275:1471-4

5. Gordon DH, Rose JS, Kottmeier P, et al: Jugular venous ectasia in children. Rudiotogy 1976;118: 147-9

6. Koh SJ, Brown RE, Hollabaugh RS: Venous aneurysm. South Med J 1984;77:1327-8

7. Tatezawa T, Shiozawa Z, Akisada M, et al: Venous angioma of the neck in a child. Pediotr Rndiol 1979;8:122-3

8. Felson B, Reeder MM: Gamuts in radiology (ed 2). Cincinnati: Audiovisual Radiology of Cincinnati, 1987