Exercise : Vascular Abnormalities

EXERCISE 3-4. VASCULAR ABNORMALITIES

3-16. The most likely diagnosis in Case 3-16 (Figure 3-46) is

A.         pericardial cyst.

B.         adenopathy.

C.         aortic dissection.

D.         pulmonary artery aneurysm.

E.         enlarged azygous vein.

3-17. The abnormality outlined by arrows in Case 3-17 (Figure 3-47) is

A.         substernal goiter.

B.         innominate artery aneurysm.

C.         lung cancer.

D.         right aortic arch.

E.          mediastinal adenopathy.

3-18. Causes for the appearance of the chest in Case 3-18 (Figure 3-48) include all of the following except

A.         ascending aortic aneurysm.

B.         anterior mediastinal mass.

C.         pleural mass.

D.         lung cancer.

E.          Ewing’s sarcoma of the rib.

3-19. The arrow in Figure 3-49 is showing

A.         aortic ectasia.

B.         aortic constriction.

C.         pulmonary artery dilatation.

D.         adenopathy.

E.         embolic changes.

3-20. The abnormality shown by the arrow in Figure 3-50 is most likely a(n)

A.         enlarged main pulmonary artery.

B.         descending thoracic aorta aneurysm.

C.         patent ductus arteriosus.

D.         pulmonary vein stenosis.

E.         left superior vena cava.

Radiographic Findings

3-16. In this case (Figure 3-46), there is marked enlarge-ment of the distal ascending and transverse thoracic aorta with shift of the trachea to the right. In associa-tion with the clinical symptoms, the most worrisome diagnosis is dissection of the aorta (C is the correct answer to Question 3-16).

3-17. This case (Figure 3-47) is an example of a right-sided aortic arch in an asymptomatic individual (D is the correct answer to Question 3-17).

3-18. This case (Figure 3-48) is a radiograph of the patient in Case 3-16 (Figure 3-46) 9 years later and shows a localized mass in the region of the ascending aorta.

The CT image (Figure 3-51) confirmed the large as-cending aorta aneurysm (E is correct answer to Question 3-18).

3-19. This case (Figure 3-49) shows rib notching (arrow-head) and a localized constriction of the proximal descending aorta (arrow) (B is the correct answer to Question 3-19). These findings are diagnostic of coarctation of the aorta.

3-20. This case (Figure 3-50) is an example of a chronic pseudoaneurysm of the proximal descending aorta (arrow) in a patient with remote major trauma (B is the correct answer to Question 3-20).

Discussion

Anomalies of the major vessels are commonly encountered on the chest radiograph. The aortic arch is an easily recog-nized shadow. On the PA projection, the aorta originates in the middle of the chest and then arches superiorly and slightly to the left (hence the term aortic arch), then curves, crosses the mediastinum at an oblique angle, and continues as the descending thoracic aorta (see Figure 3-1). The con-figuration of the aorta changes during life. In the young person, the aortic arch is narrow and smooth and the descending thoracic segment very straight. In the older indi-vidual with atherosclerotic disease or aortic stenosis, the as-cending aorta becomes more prominent along the right heart border and may have an undulating pattern in the descending thoracic portion.

Aortic dissection as seen in Case 3-16 (Figure 3-46) can be a life-threatening diagnosis. This is often the result of atherosclerosis and/or medial layer necrosis. In this disor-der, blood dissects into the aortic wall through a tear of the intima. This process may begin anywhere along the course of the thoracic aorta, but the exact location is very important because it has therapeutic implications. Aortic dissec-tion is most easily classified by the Stanford system. This di-vides dissections into type A, those involving the ascending aorta, and type B, those that begin distal to the left subcla-vian. When associated with symptoms, type A dissections are considered surgical emergencies, whereas symptomatic type B dissections often can be managed medically. In the acute setting, the diagnosis is best established by CT be-cause it can rapidly define the entire scope of the dissection as well as show the relationship to other major vessels (see Figure 3-15). Echocardiography can also rapidly detect dis-section but provides less anatomic detail. MR imaging is often not used in the acute setting because of time and availability issues. The role of angiography as a diagnostic procedure for dissection has virtually disappeared; however, intravascular therapy including placement of stent-grafts and fenestration of the dissection flap can be performed for treatment in many instances, including medically inop-erable individuals.

Other abnormalities of the aortic arch are uncommon. Congenital aortic anomalies include left aortic arch with aberrant branching, right aortic arch, and double aortic arch. The most prominent of these aberrations is the right aortic arch, which occurs in 1 in 2500 people. It can be diagnosed on the conventional radiograph by noting an indentation to and slight deviation of the right side of the trachea and dis-placement of the SVC shadow, as shown in Case 3-17 (Figure 3-47, arrows). In many individuals, the right arch is discov-ered incidentally and in these cases, is usually associated with an aberrant left subclavian artery (Figure 3-52). The barium swallow can also demonstrate mass effect on the esophagus by the aberrant subclavian and aorta as it crosses from right to left in the chest. When associated with congenital anom-alies (tetralogy of Fallot, truncus arteriosus, etc), the great vessel branching pattern is a mirror image of that seen in a normal left aortic arch.

Aneurysms of the aorta, shown in Cases 3-18 and 3-20 (Figure 3-48 and 3-50), are most often caused by atheroscle-rosis. Trauma, infection, and connective tissue disorders such as Marfan and Ehlers-Danlos syndrome are other causes. Aneurysms may be saccular or fusiform in shape, and symp-toms include chest pain, hoarseness from compression of the recurrent laryngeal nerve, postobstructive atelectasis from compression of a bronchus, and dysphagia from esophageal compression. However, aneurysms are most commonly dis-covered as an incidental finding on an imaging study done for other reasons. An aneurysm of the ascending or trans-verse aortic segments shows a focal enlargement of the aortic shadow, usually with curvilinear calcification in its wall. A saccular aneurysm of the descending aorta may be misdiag-nosed as a lung, mediastinal, or pleural mass, especially if it does not contain linear calcification. In these cases, as men-tioned previously, CT is the next best imaging modality to perform (see Figure 3-51). The lack of rib destruction in Case 3-18 strongly argues against a chest wall sarcoma.

The abnormality in Case 3-19 (Figure 3-49) is coarctation of the aorta. This congenital anomaly results in partial or complete obstruction of the aorta at the junction of the aor-tic arch and descending aorta near the ligamentum arterio-sum (the in utero connection between the aorta and pulmonary arteries). About one half of these individuals also have a bicuspid aortic valve. The obstruction to flow due to the coarctation results in elevated upper-extremity blood pressure and decreased lower-extremity blood pressure. A systolic ejection murmur may also be heard. Because of the partial aortic obstruction, collateral flow through the inter-costal arteries results in the rib notching seen (Figure 3-53).