According to umm.edu, "Pulmonary edema(congestion) is an abnormal build up of fluid in the air sacs of the lungs, which leads to shortness of breath.

Pulmonary edema may be caused by damage directly to the lung, such as that caused by poisonous gas or severe infection, as a side effect of medications, or the result of major trauma."

The major drugs that are mentioned that may cause pulmonary congestion are Proleukin and Aldesleukin.

Congestive heart failure is a condition in which the function of the heart as a pump is insufficient to supply oxygen-rich blood to the body. Congestive heart failure can be caused by diseases that weaken the heart muscle, diseases that cause the stiffness of the heart muscles or diseases that increase oxygen demand by tissues of the body beyond the capacity of the heart to provide blood adequate oxygen-rich. Congestive heart failure can affect many organs. For example: The weakened heart muscle may not be able to deliver enough blood to the kidneys, which in turn begin to lose their normal ability to excrete salt and water. This can cause decreased kidney function in the body to retain more fluid. The lungs can become clogged with fluid and the ability of the person to take down. The fluid can also accumulate in the liver, which hinders their ability to rid the body of toxins and produce essential proteins. The intestines can become less efficient in absorbing nutrients and drugs. The fluid can also accumulate in the extremities, causing swelling of the ankles and feet.
http://www.insideheart.com/causes-of-congestive-heart-failure.html

Pulmonary congestion is a complication brought about by heart failure. Heart failure means an inability of the heart to maintain cardiac output sufficient enough to meet the body's metabolic needs. The heart is also unable to clear venous return. That is unoxygenated blood that can be found in the veins find it hard to pass through the superior vena cava (the largest venous branch) into the right chambers of the heart. Because of this there is vacular congestion and a drop of cardiac out which will eventually lead to pulmonary congestion and edema .(generalized swelling).

The most common causes of Congestive Heart Failure are:
1. increase in blood pressure or hypertension
2. chronic alcohol abuse
3. heart valves that are not functioning well because of disorder
Less common causes are:
4. infection of cardiac muscles
5. thyroid problem

Symptoms of CHF
1.fatigue
2. swollen ankles and arms
3. accumulation of fluid in the lungs or pulmonary congestion
4.inability to sleep
5. nausea
6.stomach pain
7. appetite loss

Prevention includes:

1. Lifestyle modification by avoiding alcoholic beverages, eating well balanced diet
2. Regular exercise
3. maintain an appropriate weight.
4. enough fluid intake
5. avoid smoking
6. immunization against pneumococcal bacterium

What is pulmonary congestion exactly?
Pulmonary congestion also referred as Pulmonary edema is fluid accumulation in the lungs.

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Pulmonary edema (American English), or oedema (British English; both words from the Greek οἴδημα), is fluid accumulation in the lungs.1 It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the heart to remove fluid from the lung circulation ("cardiogenic pulmonary edema") or a direct injury to the lung parenchyma ("noncardiogenic pulmonary edema").2 Treatment depends on the cause, but focuses on maximizing respiratory function and removing the cause.
----quote----
Information quoted from http://en.wikipedia.org/wiki/Pulmonary_edema

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/APO.jpg/230px-APO.jpg

What causes pulmonary congestion?

----quote----
Increased hydrostatic pressure
Increased capillary permeability
Over-hydration
Pulmonary infiltration
Pulmonary vein occlusion
Pulmonary embolism
Reduced osmotic pressure
Transfusion reaction
Reduced production of plasma proteins
ARDS (Adult Respiratory Distress Syndrome)
----quote----
Information quoted from http://www.medcyclopaedia.com/library/radiology/chapter18/4/9.aspx

What are the symptoms?
1.Difficulty breathing
2.Coughing up blood
3.Excessive sweating
4.Anxiety
5.Pale skin.