19 Differences Between Transudates and Exudates

The major difference between transudates and exudates Pleural effusion is that transudate pleural effusion causes the formation of a clear fluid that has a low level of protein and cell. This is due to higher capillary hydrostatic pressure as well as the lower capillary pressure oncotic. However, on the other hand, exudate causes pleural effusion, which results in an opaque fluid that has an elevated amount of protein and cells due to the increase in capillary permeability caused by an inflammation process. In addition congestive heart failure persistent kidney diseases, enteropathy that loses protein and so on. can cause an exudate pleural effusion, while infections or tumors and pulmonary embolism and autoimmune disorders cause an exudate and pleural effusion.

In brief, transudate as well as exudate pleural effusions are the two main pathophysiological causes of pleural effusion. They result in the build-up of fluid inside the cavity of the pleural wall. In addition, the criteria of Light are the most widely used and precise diagnostic tool which aids in determining between two forms of pleural effusion.


What is Pleural Effusion ?

The pleural effusion can be described as a condition that can be a result of the pathophysiology of the lungs, which results in the accumulation of excessive fluid within the pleural cavity. The pleural cavity is a space filled with fluid, that lies between the parietal and visceral pleura, which is the lung lining. In general, a tiny amount of fluid is found within the pleural cavity, for the purpose of lubrication as well as to facilitate breathing.

Furthermore an accumulation of excess fluid may cause breathing difficulties due to the limitation of the lung’s expansion. The amount of breathing impairment and the efficacy of treatments are the two primary variables that determine the severity of the pleural effusion. Additionally, depending on the reason the two kinds of pleural effusions: proteins-poor (transudate) as well as protein rich (exudate).

Pleural effusion
Pleural effusion

Signs and Symptoms of Pleural Effusion

Examining the symptoms and signs In the case of some patients, they do not exhibit any symptoms or signs. However, the most frequent signs of pleural effusion can be ascites, peripheral edema friction rubs on the pleural area, elevated jugular vein pressure and lower extremity swelling that is unilateral and lymphedema, yellowish nails and many more. Additionally indications, signs of pleural effusion are chest pain, fever dry nonproductive cough and dyspnea (shortness of breath or difficult breathing or breathing) and orthopnea (the difficulty breathing even if the person is sitting straight or standing straight) hemoptysis and weight loss, etc.

Diagnosis of Pleural Effusion

The identification of pleural effusion depends on medical history as well as physical examination. Additionally, it can be confirmed with a chest X-ray where the pleural effusion is visible as a white area on a typical postoanterior chest radiograph. Other diagnostic methods are an examination of the chest CT (computed tomography) and lung ultrasound that are more reliable as compared to chest X-rays.


Additionally, thoracentesis is a procedure used to diagnose, helping to identify the reason for an edema of the pleural. Additionally, it involves the taking of the pleural fluid for the analysis of the composition to collect blood cells, and checking for the presence of cancerous cells.


In general, the pH of the fluid in the pleural cavity is 7.6. A pleural fluid pH higher than 7.3 indicates that resolution is achievable with only medical treatment. A pH less than 7.2 indicates the possibility of a more complex effusion or empyema that requires surgical drainage is likely to have developed. On the other hand the normal levels of glucose within the fluid of the pleural are believed to be below 3.4 mg/L. But, in certain circumstances, like cancer, tuberculosis empyema or rheumatoid, the pleural sugar/serum fluid glucose ratio is lower than 0.5.


In the case of a typical amounts of the red blood cell within the pleural fluid are less that 10,000 RBCs/uL, while the norms for the white blood cell count are lower 1,000 WBCs/uL. In essence, RBC counts greater than 100,000/uL are seen in malignancy, trauma or an infarct of the pulmonary system. The elevated numbers in WBC counts and the percentage of neutrophils found in the pleural fluid suggests an infection with bacteria or diarrhea or active colitis menstrual or ovulation cycles, and pelvic inflammatory diseases.

Light’s Criteria 

“Light’s” criteria are a method which helps to determine if fluid in the body cavity, also known as an effusion is the result of exudate or transudate. Utilizing the patient’s blood and the fluid present in the effusion and comparing characteristics, medical professionals can determine whether the fluid is caused by pressure issues (transudate) or cell leakage (exudate).


What is the Transudate Pleural Effusion?

Transudate pleural effusion is among of two pathophysiological causes of the pleural effusion. It’s typically defined by the transudation or permeation in pleural fluid via the walls of pulmonary vessels. Additionally, the two most common causes of transudate pleural effusion , are higher hydrostatic pressure that occurs in congestive heart failure or decreased oncotic pressure in cirrhosis and nephrotic disorder. Thus, the filtrate is a clear liquid with an extremely low protein content and cell count.

What is the Exudate Pleural Effusion ?

Exudate pleural effusion can be described as the different kind of pleural effusion, which is defined by the exudation or escaping from the body due to the lymph vessels result of tumors and inflammation. The majority of the time, these lesions permit larger molecules and the solid matter to flow through the cavity of the pleural. This is why the pleural cavity becomes cloudy and contains a lot of protein and cell count.

Differences Between Transudates and Exudates
Differences Between Transudates and Exudates

How Do You Distinguish Between Transudate and Exudate?

“Transudate” is the result of the buildup of fluid due to systemic conditions that alter the pressure inside blood vessels, which causes fluid to exit the blood vessels.

“Exudate” is the result of the buildup of fluid that is caused by tissue leakage caused by inflammation or local damage to cells. The fluid is exudate when any of the following requirements is present:  

  • The ratio of serum protein to Effusion protein is higher than 0.5
  • Lactate dehydrogenase (LDH) infusion (LDH)/serum LDH ratio that is greater than 0.6
  • The level of LDH infusion is higher than two-thirds of the upper limit of laboratory’s reference range for serum LDH

Why Is LDH High in Exudate?

Lactate dehydrogenase (LDH) is an enzyme that is found in cells of the body. If there is cell damage, LDH leaks out and is then absorbed into the effusion. A excessive LDH within the effusion indicates damage to cells, which generally results from an exudative procedure. This is the reason why one of the criteria used by Light measures LDH within the effusion.

What Are Causes of Transudative Effusions?

  • Lung tissue that is partially collapsed (atelectasis) due to an increase in negative pressure within the lung cavity
  • Cerebrospinal liquid (CSF) leaks into the the lung cavity (pleural space) Trauma to the spine of the thoracic Ventriculoperitoneal (VP) Shunt malfunction
  • Heart failure
  • Liver dysfunction
  • The blood albumin level is low (hypoalbuminemia)
  • Iatrogenic (misplaced catheter into lung)
  • Nephrotic syndrome
  • Peritoneal dialysis
  • Inflammation of the urinary tract causing urinary backflow within the body (urinothorax due to obstruction of the urology)

What Are Causes of Exudative Effusions?

  • Abdominal fluid: Abscess of tissues near lung or abdomen. Fluid in the abdomen (ascites) Meigs syndrome and pancreatitis
  • Connective-tissue disease: Churg Strauss disease, Lupus, Rheumatoid arthritis Wegener granulomatosis
  • Endocrine Thyroid: Low thyroid (hypothyroidism) and ovarian hyperstimulation
  • Iatrogenic: drug-induced esophageal perforation or feeding tube in the lung
  • Infectious: Abscess on the lung’s tissue the fungal infection, parasites tuberculosis
  • Inflammatory: Acute respiration distress syndrome (ARDS) asbestosis, pancreatitis and radiation, sarcoidosis, excessive levels of urea (uremia) in blood (uremia)
  • Lymphatic anomalies: Chylothorax (fluid around the lung) and cancer of the lymph nodes and lymphangiectasia (over-dilation of lymph vessels)
  • Malignancy: Lymphoma, cancer mesothelioma paraproteinemia

Differences Between Transudates and Exudates

DefinitionTransudate pleural effusion refers to the type of pleural effusion in which fluid is pushed through the capillary due to high pressure within the capillary.Exudate pleural effusion refers to the other type of pleural effusion in which fluid leaks around the cells of the capillaries caused by inflammation.
CauseUsually develop from imbalances in hydrostatic and oncotic forces in circulation.Usually develop from increased capillary permeability or decreased lymphatic reabsorption.
Associated withCongestive heart failure Fluid overload Nephrotic syndrome Hepatic cirrhosis MalnutritionMicrobial infections Membrane inflammations Malignancy Connective tissue diseases.
AppearanceClear, thin-colored, pale yellowTurbid, hemorrhagic, straw colored
FibrinogenLow content of fibrinogen (low tendency to clot)High content of fibrinogen (high tendency to clot)
Specific gravity<1.012>1.012
Common CausesCongestive heart failure, chronic kidney disease, protein-losing enteropathy, nephrotic syndrome, and hepatic cirrhosis result in transudate pleural effusion.Infections, malignancies, pulmonary embolism, and autoimmune diseases result in exudate pleural effusion.
Glucose contentSame as plasmaLow (less than 60 mg/dl)
SAAG (Serum-Ascites Albumin Gradient)The SAAG of transudate pleural effusion is more than 1.2 g/dLThe SAAG of exudate pleural effusion is less than 1.2 g/dL.
Total ProteinLess than 3 gm/dlMore than 3 gm/dl
Fluid/Serum Protein<0.5>0.5
Fluid/Serum LDH (Lactate Dehydrogenase)The fluid/serum LDH ratio is less than 0.6 in transudate pleural effusion.The fluid/serum LDH is more than 0.6 in exudate pleural effusion.
Fluid LDHThe fluid LDH is less than 0.67 x ULN serum for transudate pleural effusion.The fluid LDH is more than 0.67 x ULN serum for exudate pleural effusion.
Cholesterol ContentThe cholesterol content of the transudate pleural effusion is less than 1.2 mmol/l.The cholesterol content of the exudate pleural effusion is 1.2 mmol/l or greater.
WBC count<1000/ul>1000/ul
Differential countMesothelial cells or lymphocytesPolymorphs, lymphocytes or RBCs
Radiodensity on CT ScanThe radiodensity on CT scan is 2-15 HU of transudate pleural effusion.The radiodensity on CT scan is 4-33 HU of exudate pleural effusion.

Leave a Comment

Our Domain,, has now change to
This domain will be Unavailable, All the posts from this website are transferred to the new domain. Enjoy study
Important notice
Overlay Image
Our website,, has now change to
This domain will be Unavailable, All the posts from this website are transferred to the new domain. Enjoy study
Overlay Image

Adblocker detected! Please consider reading this notice.

We've detected that you are using AdBlock Plus or some other adblocking software which is preventing the page from fully loading.

We don't have any banner, Flash, animation, obnoxious sound, or popup ad. We do not implement these annoying types of ads!

We need money to operate the site, and almost all of it comes from our online advertising.

Please add to your ad blocking whitelist or disable your adblocking software.