Radiology 5th year, 14th lecture/part one (Dr. Abeer)
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Transcript of Radiology 5th year, 14th lecture/part one (Dr. Abeer)
Pulmonary Vessels
*It is not possible to measure the diameter of the MPA from the plain film (usually subjective); but if there are variable
degrees of bulging, means enlarged MPA.
*Assessment of the hilar pulmonary arteries is more objective & the diameter of the Rt. lower lobe artery at its
mid-point (normally 9 – 16 mm).
*The size of pulmonary vessels with the lung reflects the pulmonary blood flow.
*Increase pulmonary blood flow is seen in ASD, VSD& , PDA, & all of these will lead to Systemic to Pulmonary (Lt.
to Rt. shunt) & these will to increase pulmonary blood flow.
Pulmonary Vessels
*Hemodynamically significant Lt. to Rt. shunt is (2/1 ratio or more) & this will produce CXR findings; if less ratio
there will be no CXR findings & all the pulmonary vessels will (from the MPA to the periphery of the lung) will be
enlarged, & this is called "Pulmonary Plethora."
*There is good correlation between the size of the vessel on CXR & degree of the shunt.
*Decrease pulmonary blood flow, all the vessels are small
" Pulmonary Oligemia."
*The commonest cause of decrease pulmonary blood flow is TOF & pulmonary stenosis.
*Obstruction of the Rt. ventricle outflow + VSD will lead to Rt. to Lt. shunt.
*Pulmonary stenosis will cause oligemia only is severe cases & babies or very young children.
Pulmonary Vessels
Pulmonary Arterial Hypertension
*The pressure in the pulmonary artery depends on:
1 -Cardiac output.
2 -Pulmonary vascular resistance.
Pulmonary Arterial Hypertension
*Conditions that cause significant pulmonary arterial hypertension all increase the resistance of blood flow
through the lungs, examples:
1 -Various lung diseases (cor pulmonale). 2 -Pulmonary embolism.
3 -Pulmonary arterial narrowing in response to mitral valve diseases or Lt. to Rt. shunt.
4 -Idiopathic pulmonary hypertension.
Pulmonary Arterial Hypertension
*By CXR: There will be enlargement of the mean pulmonary artery + the hilar pulmonary artery, vessels within the lung tissue are normal or small.
*Eisenmenger's syndrome:
Greatly raised pulmonary artery resistance in associationwith ASD, VSD, & PDA leading to reverse shunt (i.e. : Rt. to Lt. shunt).
Pulmonary Arterial Hypertension
*The cause of pulmonary arterial hypertension may be visible on the CXR as cor pulmonale & mitral valve
diseases.
Pulmonary Arterial Hypertension due to ASD & Eisenmenger's
syndrome
Pulmonary Venous Hypertension
*The commonest causes of pulmonary venous hypertension are:
1 -Mitral valve diseases. 2 -Lt. ventricular failure.
*In normal upright person (by CXR) the lower zone vessels
are larger than the upper zone.
*In pulmonary venous hypertension the upper zone vessels are enlarged.
*In severe cases, the upper zone vessels become larger
than that of the lower zone, & eventually Pulmonary Edema will supervene & may obscure the blood vessels.
Pulmonary Venous Hypertension
Pulmonary Venous Hypertension in a patient with Mitral Valve
Disease
Aorta *With aging the aorta becomes elongated, elongation
necessarily involve unfolding, where the ascending aorta will deviate to the Rt. & the descending aorta to the Lt.,
because the aorta is fixed at the aortic valve & the diaphragm.
*Unfolding aorta is easily confused with aortic dilatation. *Aortic dilatation of the ascending aorta is due to:
1 -Aneurysm. 2 -Aortic regurgitation or aortic stenosis.
3 -Systemic hypertension. *The two common causes of descending aortic aneurysm
are: 1 -Atheroma.
2 -Aortic dissection. (Also, there is a rare cause as previous trauma following decelerating injury.)
Aorta *By CXR:
1 -The diagnosis of aortic aneurysm may be obvious, but substantial dilatation may be needed before the bulge of
Rt. mediastinal border can be recognized.
2 -Atheromatous aneurysm invariably shows calcification of their walls.
*CT scan with IVCM or CT angiography or MRA are very useful to assess the aneurysm.
Note:
IVCM = I.V. Contrast Media.MRA = Magnatic Resonance Angiography.
Dissecting Aortic Aneurysm
It is important to know the extent of the dissecting aneurysm as those involving the ascending aorta are treated surgically & those confined to the descending aorta are treated with hypotensive drugs.
*By CXR: Two congenital aortic anomalies can be seen, & they are:
1 -Coarctation of Aorta. 2 -Rt. sided aortic arch, in association with TOF,
Pulmonary Atresia, & Truncus Arteriosus, or it also can be isolated with no clinical significance.
Dissecting Aortic Aneurysm
Trans-Esophageal Echocardiogram showing the True (T) & False (F)
lumina in the descending aorta
Dissecting Aortic Aneurysm
CT-scan showing the displaced intima (arrows) separating the
true & false luminae in the ascending & descending aorta