Pleural effusion and ascites fluid analysis

Pleural and ascites fluid are frequently analyzed for diagnosis. Much can be learnt about a patient's condition by these fluid analyses.

Let's discuss the principles of fluid analysis here.

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Pleural fluid analysis:


Microscopy

• Red blood cell count >100,000 cells/mm3 suggests hemorrhagic fluid
• White blood cell count >10,000 cells/mm3 certainly suggests infection

Biochemistry
By Light's criteria, which compare protein and LDH levels in pleural fluid with those in serum, an effusion is an exudate if it satisfies any one of the following:

• If ratio of pleural fluid protein to serum protein is >0.5
• If pleural fluid lactate dehydrogenase (LDH) is >200 international units or two-thirds of the upper limit of normal
• If ratio of pleural fluid LDH to serum LDH is >0.6

(Historically, a protein content <3.0g/dL was thought to denote a transudate and >3.0g/dL an exudate)
Bacteriology

• Gram stain and culture establishes etiology of infection
• Sensitivity testing guides therapy
• Acid-fast smears and cultures can identify tuberculosis

Cytology

• Sample is collected in a 50mL heparinized bottle
• Taking three samples maximizes chance of positive findings (to 80% of malignant cases)
• malignant cells are found in two-thirds of effusions due to bronchogenic or breast cancer but in only 15% of those due to lymphoma

Cause of abnormal result

Visual inspection

• Very clear fluid is likely to be transudate
• Dark fluid likely is to be exudate
• Turbid or milky fluid likely to be pus from empyema or chyle
• Uniformly blood-stained fluid likely to be hemorrhagic

Microscopy
Red blood cell count >100,000 cells/mm3 may be due to:

• Malignancy
• Trauma
• Pulmonary embolism
• Bleeding diathesis

If white cell count is raised with neutrophils >50%:

• Acute pleuritis or other pyogenic infection

If white cell count is raised with lymphocytes >90%:

• Tuberculosis
• Lymphoma or other malignancies

If white cell count is raised with eosinophils >10%:

• Asbestos effusions
• Resolving infections
• Pneumothorax

If mesothelial cells are absent:

• Tuberculosis

Biochemistry
Any one of the following criteria denotes an exudate:

• Ratio of pleural fluid protein to serum protein is >0.5
• Pleural fluid lactate dehydrogenase (LDH) is >200 international units or two-thirds of the upper limit of normal
• Ratio of pleural fluid LDH to serum LDH is >0.6

Glucose <60mg/dL:

• Rheumatoid-related effusions
• Tuberculosis
• Empyema
• Malignancy

pH <7.2:

• Malignancy
• Tuberculosis
• Empyema
• Esophageal rupture

Amylase - ratio of pleural fluid amylase to serum amylase >1.0:

• Pancreatitis, malignancy, and esophageal rupture

Bacteriology

• Positive Gram stain or culture provides likely etiology of infection

Cytology

• Positive identification of malignant cells proves etiology

Others

• Antinuclear antibodies - ratio of pleural fluid antinuclear antibodies to serum antinuclear antibodies >1.0 suggests systemic lupus erythematosus
• Rheumatoid factor >640 suggests rheumatoid-related effusion
• Hyaluronic acid >1mg/mL is highly suggestive of mesothelioma (and other malignancies)
• Adenosine deaminase >70 international units suggests tuberculosis

Ascitic fluid analysis:


Gross appearance:

1) clear, straw coloured or light green
Cirrhosis, CCF, nephrotic syndrome

2)hemorrhagic
malignancy, TB, pancreatitis

3)cloudy, turbid
bacterial peritonitis

4)deep green
biliary leak

5)milky white
lymphatic obstruction

Specific gravity:

1) less than 1.016 in transudate
2)more than 1.016 in exudate

Protein:

1)less than 2.5g/dl in transudate
2)more than 2.5g/dl in exudate

Glucose:

low in malignancy, TB, peritonitis

Amylase activity:

more than 1000U/L in pancreatitis

Microscopy:

1) neutrophils
less than 250mm3 in cirrhosis
more than 250mm3 in bacterial peritonitis

2)lymphocytes
TB,malignancy

3)ZN staining
TB

4) grams stain
bacterial peritonitis

5)cytological examinaiton
malignancy

Culture:

1)pyogenic bacteria
bacterial peritonitis

2)Acid fast bacteria
TB

Pleural effusion fluid analysis

Exudative

This is due to local factor that influence the formation and absorption of fluid alteration ( eg : infection , malignancy )

• Pleural fluid/serum protein > 0.5 or absolute value > 3 g/dl.

• Pleural fluid/serum LDH > 0.6 or absolute value > 0.45 upper normal serum limit

• Pleural fluid specific gravity > 1.018

Transudative

This is due to systemic factor that influence the formation and absorption of fluid alteration

• Pleural fluid/serum protein < 0.5 or absolute value < 3 g/dl.

• Pleural fluid/serum LDH < 0.6 or absolute value < 0.45 upper normal serum limit

• Pleural fluid specific gravity < 1.018

Once an effusion is categorized as transudative or exudative, etiologic considerations narrow. Additional pleural fluid studies that help to establish a diagnosis include glucose, amylase, white blood cell counts with differential, and cytologic and microbiologic examination.

Ascites fluid analysis

The ascitic fluid should be analyzed for:

1. The serum-ascitic albumin gradient (SAAG) is calculated by subtracting the albumim concentration of the ascitic fluid from the albumin concentration of a serum specimen obtained on the same day.

1. The amylase concentration which is elevated in pancreatic ascites.

1. The triglyceride concentration which is elevated is chylous ascites.

1. White cell count when greater than 350/microliter is suggestive of infection. If most cells are polymorphonuclear, bacterial infection should be suspected. When mononuclear cells predominated , tuberculosis or fungal infection is likely.

1. Red cell count When greater than 50.000/microliter denotes hemorrhagic ascites, which usually is due to malignancy, tuberculosis or trauma.

1. Gram stain and culture which can confirm the diagnosis of bacterial infection.

1. pH when less than 7 suggests bacterial infection

1. Cytology can be positive in malignancy.

The serum-ascitic albumin gradient correlates directly with portal pressure, and patients with gradients greater than or equal to 1.1 g/dl have portal hypertension (transudative ascites) and patients with gradients lesser than 1.1 g/dl do not (exudative ascites). The total protein concentration of ascitic fluid and LDH activity has been traditionally used to classify ascitic fluid in exudate or transudate

PLEURAL FLUID ANALYSIS
The fluid is evaluated for the following:

• Chemical composition including protein, lactate dehydrogenase (LDH), albumin, amylase, pH and glucose
• Gram stain and culture to identify possible bacterial infections
• Cell count and differential
• Cytology to identify cancer cells, but may also identify some infective organisms
• Other tests as suggested by the clinical situation - lipids, fungal culture, viral culture, specific immunoglobulins

TRANSUDATE VERSUS EXUDATE

TRANSUDATE
Transudative pleural effusions are caused by systemic factors that alter the balance of the formation and absorption of pleural fluid
Eg: Congestive Cardiac Failure
Nephrotic Syndrome
Cirrhosis
EXUDATE
Exudative pleural effusions are caused by alterations in local factors that influence the formation and absorption of pleural fluid.
Eg : A) Above the diaphragm
-Tuberculosis
-Pyogenic infections : pneumonia,lung abscess, bronchiectasis,septicaemia
-Viral and fungal infections
-Pulmonary infection
-Neoplasms
-Chest wall affections –trauma,tuberculous osteitis
-Post myocardial infarction syndrome
-Rupture of esophagus

B) Below the diaphragm
-Ameobic liver abscess
-Subdiaphragmatic abscess
- Acute pancreatitis

C) Systemic disorders :
-collagen disease : SLE , Rheumatoid arthritis, polyarthritis
-septicaemia
-drug allergy
-bleeding disorders



SPECIFIC FEATURES OF DIFFERENT PLEURAL EFFUSIONS


1) GROSS

A) Purulent
B) Haemorrhagic
C) Milky
D) Greenish : pseudomonas,streptococcus,pneumococcus
E) Gold Paint : myxedema
F) Anchovy sauce pus –ruptured amebic liver abscess

2) MICROSCOPIC

A) Lymphocytic predominance :
Chronic conditions like TB,resolving pneumonia,fungal infections,
Carcinoma and myxedema.
B) Polymorphic predominance : Acute conditions like acute bacterial
Infections and rheumatic fever.
C) Eosinophilic predominance

3) BIOCHEMICAL INVESTIGATIONS

A) proteins more than 3gm%-exudate; less than 3gm%-transudate
B) sugar diminished in rheumatoid arthritis
C) LDH increased in tuberculosis effusion
D) Amylase increased pancreatitis,rupture of esophagus and salivary
Gland abscess.
E) Adenosine deaminase activity increased in tuberculous effusion.
F) Hyaluronidase is increased in mesothelioma of pleura.
G) Light’s criteria using serum and pleural fluid protein and LDH ratio
Used to differentiate transudate from exudate.

Transudative :

· Pleural fluid/serum protein < 0.5 or absolute value < 3 g/dl.
· Pleural fluid/serum LDH < 0.6 or absolute value < 0.45 upper normal serum limit
· Pleural fluid specific gravity < 1.018

Exudative :

• Pleural fluid/serum protein > 0.5 or absolute value > 3 g/dl.
• Pleural fluid/serum LDH > 0.6 or absolute value > 0.45 upper normal serum limit
• Pleural fluid specific gravity > 1.018

ASCITES FLUID ANALYSIS

Etiology
The main causes of ascites include the following conditions:

• Hepatic - cirrhosis, veno-occlusive disease
• Cardiac - right ventricular failure, constrictive pericarditis
• Renal - nephrotic syndrome, renal failure
• Malignancy - ovarian, gastric, colorectal carcinoma
• Infection - tuberculosis
• Pancreatitis
• Lymphatic - congenital anomaly, trauma
• Malnutrition
• Myxoedema

Investigation
A diagnostic peritoneal tap allows peritoneal fluid to be sent for:

• Protein estimation
• A transudate has a total protein < 30 g/l - cirrhosis, heart failure
• An exudate has a total protein > 30 g/l - carcinomatosis, infection
• Cytology
• Bacteriology
• Biochemistry - amylase, CEA

SPECIFIC FEATURES IN DIFFERENT ASCITES FLUID

GROSS :

Clear- transudative
Turbid- purulent-abdominal infections,pyemia,septocaemia,rupture or perforation of organ,ruptured amoebic abscess,pelvic inflammatory disease
Straw- ccf,nephritic syndrome,cirrhosis
Haemorrhagic-malignancy,tuberculosis,trauma,pancreatitis
Deep green : biliary leak
Milky white : Lymphatic obstruction

MICROSCOPY

Lymphocytic predominance – Tuberculosis,.
Polymorphic predominance : Bacterial peritonitis
Gram stain : bacterial peritonitis
ZN staining : Acid fast bacilli-tuberculosis
Cytology : malignancy
Culture : bacterial peritonitis


BIOCHEMICAL

Proteins: > 3gm/dl – exudative
<3gm/dl –transudative
Specific gravity : >1.015-exudative
<1.015 transudative
Glucose : decreased in malignancy,TB and bacterial peritonitis
Amylase : >1000U/l inpancreatitis
Carcinoembryonic antigen(CEA) : Colorectal carcinoma

Pleural effusion fluid analysis

Pleural fluid is collected in the pleural space.
A sample of pleural fluid is obtained by a procedure called thoracentesis.

Transudative effusions are caused by some combination of increased hydrostatic pressure and decreased oncotic pressure in the pulmonary or systemic circulation. Heart failure is the most common cause, followed by cirrhosis with ascites and hypoalbuminemia, usually from the nephrotic syndrome.

Exudative effusions are caused by local processes leading to increased capillary permeability resulting in exudation of fluid, protein, cells, and other serum constituents. Causes are numerous, the most common being pneumonia, malignancy, pulmonary embolism, viral infection, and TB.

Normal pleural fluid has the following characteristics:

• clear ultrafiltrate of plasma
• pH 7.60-7.64
• protein content less than 2% (1-2 g/dL)
• fewer than 1000 WBCs per cubic millimeter
• glucose content similar to that of plasma
• lactate dehydrogenase (LDH) level less than 50% of plasma and sodium
• potassium and calcium concentration similar to that of the interstitial fluid

Exudative

• Pleural fluid/serum protein > 0.5 or absolute value > 3 g/dl.

• Pleural fluid/serum LDH > 0.6 or absolute value > 0.45 upper normal serum limit

• Pleural fluid specific gravity > 1.018

Transudative

• Pleural fluid/serum protein < 0.5 or absolute value < 3 g/dl.

• Pleural fluid/serum LDH < 0.6 or absolute value < 0.45 upper normal serum limit

• Pleural fluid specific gravity < 1.018

Ascites fluid analysis
Ascites is the presence of excess fluid in the peritoneal cavity.
Causes

1. Peritoneal source
   1. TB
   2. Bacterial, fungal or parasitic disease
   3. Cancer
   4. Vasculitis
   5. Whipple's Disease
   6. Familial Mediterranean fever
   7. Endometriosis
   8. Starch peritonitis
2. Extra-peritoneal source
   1. Cirrhosis
   2. CCF
   3. Budd Chiari Syndrome
   4. Hypoalbuminemia
   5. 1. Nephrotic Syndrome
      2. Protein-losing enteropathy
      3. Malnutrition
   6. Ovarian disease (e.g. Meigs' Syndrome)
   7. Pancreatic disease
   8. Chylous

Gross Appearance of Ascites

• · Translucent or yellow - Normal/sterile
• · Brown -Hyperbilirubinemia, Gallbladder or biliary perforation
• · Cloudy or turbid – Infection
• · Pink or blood tinged - Mild trauma at the site
• · Grossly bloody - Malignancy or Abdominal trauma
• Milky ("chylous") – Cirrhosis, Thoracic duct injury, Lymphoma

Analysis

• Cell count: Leukocyte>500/cc or absolute neutrophil >250/cc suggests infection.
• Protein < 1g/dL in spontaneous peritonitis; >1 g/dL in secondary peritonitis.
• Glucose <50 mg/dL or increased LDH in secondary peritonitis.
• Albumin serum-ascites gradient = serum albumin - ascitic albumin
  - Gradient of > 1.1 g/dL suggests portal hypertension; seen in cirrhosis, alcoholic hepatitis, CHF, massive liver metastasis, fulminant liver failure, portal-veiin thrombosis, Budd-Chiari synd, veno-occlusive disease, fatty liver of pregnancy, myxedema.
  - Gradient of < 1.1 g/dL seen in peritoneal carcinomatosis, TB, pancreatic ascites, biliary ascites, nephrotic synd, bowel obstruction or infarction, serositis.
• Gram stain & C/S
• Amylase in pancreatic or perforation.
• Cytology or TB smear & culture

Pleural effusion
- accumulation of serous fluid within the pleural space.

This can be caused by:

1) Accumulation of fluid occurs due to local factors which influence the formation and absorption of pleural fluid. ----- exudative pleural fluid.

CAUSES:

• malignancy (e.g bronchial carcinoma, lymphoma, metastatic tumor)
• Inflamatorry processes:-

1. Infections (e.g. TB, pneumonia)
2. Pulmonary embolic disease
3. Collagen vascular disease (e.g. rheumatoid arthritis)
4. Subdiaphragmatic process
5. Asbestosis
6. Pancreatitis
7. Hypothyroidism

2) Accumulation of fluid occurs due to systemic factors which alter the balance of the formation and absorption of pleural fluid-----------transudative pleural effusion


CAUSES:

1. Decrease plasma oncotic pressure
2. Nephrotic syndrome
3. Cirrhosis
4. Increase hydrostatic pressure
5. Congestive heart failure

The procedure for collection of pleural fluid is called thoracenthesis.
The fluid collected is evaluated for the following:

• Cell count and differential culture and sensitivity
• Chemical composition including proteins, albumin, amylase, pH, glucose and lactate dehydrogenase
• Gram staining and culture and sensitivity to identify possible bacterial infections
• Cytology to identify cancer cells, but may also identify some infective organisms

Features of pleural fluid:

1) Appreance
A) Serous
-amber cloured - TB
- straw coloured - Cardiac failure
B) Milky - obstruction of thoracic duct
C) Blood stained - malignancy, acute pancreatitis
D) Greenish - pseudomonas,pneumococcus, streptococus
F) Anchovy sauce pus – ruptured amebic liver abscess

2) microscopy

A)Polymorphic predominance :
- Seen in actue conditions:
Acute bacterial Infections and Rheumatic .
B) Lymphocytic predominance :
- Seen in chronic conditions:
TB, resolving pneumonia, fungal infections, carcinoma, Rheumatoid Disease,
SLE
C) Eosinophilic predominance
- Seen in pulmonary infarction

3) biochemical
Transudative :

· Pleural fluid/serum protein < 0.5 or absolute value < 3 g/dl.
· Pleural fluid/serum LDH < 0.6 or absolute value < 0.45 upper normal serum limit
· Pleural fluid specific gravity < 1.018

Exudative :

• Pleural fluid/serum protein > 0.5 or absolute value > 3 g/dl.
• Pleural fluid/serum LDH > 0.6 or absolute value > 0.45 upper normal serum limit
• Pleural fluid specific gravity > 1.018

Ascities
- accumulation of freefluid in the peritoneal cavity.

Causes:
Common causes

• Malinant disease- hepatic, peritoneal malinancies
• Cardiac failure
• Hepatic cirrhosis

Uncommon causes

• Hypoproteinemia - nephotic syndrome,protein loosing enterpathy,malnutrition
• Hepatic venous occlusion- Budd- chiari syndrome ,Veno- occlusive disease
• Pancreatitis
• Lymphatic obstruction
• Infection- TB

Investigations:

1. Diagnostic peritoneal tap is sent for :

• Protein estimation

- A transudate has a total protein < 30 g/l - cirrhosis, heart failure
- An exudate has a total protein > 30 g/l - carcinomatosis, infection

• Serum ascities < 11g/l
• Cytology
• Microscopy, bacteriology
• Biochemistry - total albumin, amylase, CEA

2. Apperance

• Cirrhosis - clear/ straw coloured/ light green
• Malignant disease - bloody
• Infection - cloudy
• Biliary communicatiob - heavy bile stained
• Lymphatic onstruction - milky white

3. Miroscopy

• Lymphocytic predominance – Tuberculosis,
• Polymorphic predominance : Bacterial peritonitis
• Gram stain : bacterial peritonitis
• ZN staining : Acid fast bacilli-tuberculosis
• Cytology : malignancy
• Culture : bacterial peritonitis

4. Biochemical

• Proteins: < 3gm/dl – transudative , >3gm/dl – exudative
• Specific gravity : <1.015-transudative , > 1.015 exudative
• Glucose : decreased in malignancy,TB and bacterial peritonitis
• Amylase : >1000U/l inpancreatitis
• Carcinoembryonic antigen(CEA) : Colorectal carcinoma

Pleural fluid analysis:

Normally, very small amounts of pleural fluid are present in the pleural spaces, and fluid is not detectable by routine methods. When certain disorders occur, excessive pleural fluid may accumulate and cause pulmonary signs and symptoms.

Thoracentesis and Fluid analysis
• Thoracentesis is a diagnostic procedure done in patients who have abnormal amounts of fluid accumulation in the pleural space.
• The procedure is usually done at the bedside under local anesthesia.
The needle is placed through the chest wall into the pleural space and fluid is then withdrawn into a syringe.

Utility of test results:
1) Exudate vs. transudate:
(a) Fluid/serum protein ratio > 0.5
(b) Fluid/serum LDH ration > 0.6
(c) Fluid LDH > 2/3 upper normal serum LDH; exudates have 1 or more; transudates none these characteristics
2) If LDH only is abnormal - consider malignancy or Para pneumonic effusion
3) Protein may confuse: e.g., CHF
4) <3 g/dl, but might be 3-4 g/dl if patient uses diuretics, or is chronic or recurrent
5) WBC: rarely diagnostic alone; > 50,000 in Para pneumonic effusion, usually empyema; > 10,000 very inflammatory
(a) Early, acute, PMN predominant
(b) Later mononuclear - high counts suggest TB, carcinoma, lymphoma, sarcoidosis
(c) Eosinophilia - 10% suggest benign, self- limited; commonly with air or blood in pleural space; consider: hemothorax, pulmonary infarction, pneumothorax, previous thoracentesis, parasitic diseases, fungi, drugs, asbestos; rare with TB or malignancy. In 1/3 "idiopathic"
(d) Basophilia - 10%, rare; suggest leukemia
6) Mesothelial cells - paucity of cells occurs with chronic diffuse pleural lesions, e.g., TB, malignancy, empyema rheumatoid effusion, pleurodesis. If > 5%, essentially rules out TB
7) Bloody (> 100,000 cells/mm3): malignancy, trauma, pulmonary embolism, post-cardiac injury, asbestos pleurisy
8) Cytology: yields nearly 90% with malignancy as cause

Causes of pleural transudates
• Congestive heart failure
• Cirrhosis
• Atelectasis
• Nephrotic syndrome
• Peritoneal dialysis
• Myxedema
• Constrictive pericarditis

Causes of pleural exudates
• Parapneumonic illness
• Malignancy (carcinoma, lymphoma, mesothelioma)
• Pulmonary embolism
• Collagen vascular disease (rheumatic disease, lupus)
• Tuberculosis
• Asbestos-related illness
• Pancreatitis, pseudocyst
• Trauma
• Postcardiac injury syndrome
• Esophageal perforation
• Radiation pleuritis
• Drug-induced reactions
• Chylothorax
• Meig's syndrome


Ascites fluid analysis

Ascites is the presence of excess fluid in the peritoneal cavity. It is a common clinical finding with a wide range of causes, but develops most frequently as a part of the decompensation of previously asymptomatic chronic liver disease.

Causes of ascites
A) Incresased hydrostatic pressure
• Cirrhosis
• Hepatic vein occlusion(Budd-Chiari syndrome)
• Inferior vena cava obstruction
• Constrictive pericarditis
• Congestive heart failure

B) Decreased colloid osmotic pressure
• End-stage liver disease with poor protein synthesis
• Nephrotic syndrome with protein loss
• Malnutrition
• Protein-losing enteropathy

C) Increased permeability of peritoneal capillaries
• Tuberculous peritonitis
• Bacterial peritonitis
• Malignant disease of the peritoneum

D) Leakage of fluid into the peritoneal cavity
• Bile ascites
• Pancreatic ascites(secondary to a leaking pseudocyst)
• Chylous ascites
• Urine ascites

E) Miscellaneous causes
• Myxedema
• Ovarian disease(Meigs' syndrome)
• Chronic hemodialysis

Ascitic Fluid Analysis:
The ascitic fluid should be analyzed for:
1) The serum-ascitic albumin gradient (SAAG) is calculated by subtracting the albumim concentration of the ascitic fluid from the albumin concentration of a serum specimen obtained on the same day.
2) The amylase concentration which is elevated in pancreatic ascites.
3) The triglyceride concentration which is elevated is chylous ascites.
4) White cell count when greater than 350/microliter is suggestive of infection. If most cells are polymorphonuclear, bacterial infection should be suspected. When mononuclear cells predominated , tuberculosis or fungal infection is likely.
5) Red cell count When greater than 50.000/microliter denotes hemorrhagic ascites, which usually is due to malignancy, tuberculosis or trauma.
6) Gram stain and culture which can confirm the diagnosis of bacterial infection.
7) pH when less than 7 suggests bacterial infection
8) Cytology can be positive in malignancy.

A. Transudative ascites (Serum Albumin - Ascites Albumin >1.1 gm/dl)
• Liver cirrhosis
• Congestive heart failure
• Hepativ vein obstruction (Budd Chiari syndrome)
• Nephrotic syndrome
• Meig's ovarian tumor syndrome
• Constrictive pericarditis
• Inferior vena cava obstruction
• Viral hepatitis with submassive or massive hepatic necrosis

B. Exudative ascites (Serum Albumin - Ascites Albumin <1.1 gm/dl)
• Neoplastic diseases involving the peritoneum: Peritoneal carcinomatosis, Lymphomatous disorders
• Tuberculous peritonitis
• Pancreatitis
• Post surgery talc or starch powder peritonitis
• Transected lymphatics following portal caval shunt surgery
• Myxedema
• Sarcoidosis
• Lymphatic obstruction: a. Intestinal lymphangiectasia, b. Lymphoma
• Pseudomyxoma peritonei
• Struma oovarii
• Amyloidosis
• Prior abdominal trauma with ruptured lymphatics
• Hemodialysis CRF related ascites

C. Disorders simulating ascites
• Pancreatic pseudocyst
• Hydronephrosis
• Ovarian cyst
• Mesenteric cyst
• Obesity

Pleural fluid analysis:
Transudate:

• Appearance - clear
• protein - absolute value - <3.0g/dl, fluid : serum ratio - <0.5
• lactic dehydrogenase - absolute value - <200iu/L, fluid : serum ratio - <0.6
• Glucose - >60mg/dl
• leucocytes - total <1000/mm3, differential - >50% lymphocytes or mononuclear cells
• erythrocytes - <5000/mm3

Exudate:

• Appearance - clear, cloudy or hemorrhagic
• protein - absolute value - >3.0g/dl, fluid : serum ratio - >0.5
• lactic dehydrogenase - absolute value - >200iu/l, fluid : serum ratio - >0.6
• Glucose - <0.6mg/dl
• leucocytes - total - >1000/mm3, differential - >50% polymorphs or lymphocytes
• erythrocytes - variable

Low glucose concentration (<60mg/dl) suggest - empyema, malignancy, TB
very low glucose concentration(<15mg/dl) is characteristic of rheumatoid effusion
pleural fluid erythrocytes count exceeding 100000/mm3 are most often seen in malignancy and pulmonary embolism.
pleural fluid amylase is elevated in patients with pancreatic disease and esophageal rupture.

Ascites fluid analysis:
The ascitic fluid should be analyzed for:

• The serum-ascitic albumin gradient (SAAG) is calculated by subtracting the albumim concentration of the ascitic fluid from the albumin concentration of a serum specimen obtained on the same day.
• The amylase concentration is elevated in pancreatic ascites.
• The triglyceride concentration is elevated in chylous ascites.
• White cell count when greater than 350/microliter is suggestive of infection. Bacterial infection should be suspected if predominant cells are polymorphonuclear cells. Suspect TB or fungal infection if mononuclear cells is predominant.
• Red cell count greater than 50.000/microliter denotes hemorrhagic ascites, which usually is due to malignancy, tuberculosis or trauma.
• Gram stain and culture can confirm the diagnosis of bacterial infection.
• pH less than 7 suggests bacterial infection
• Cytology can be positive in malignancy.

Types of Ascites according to the level of the serum-ascites albumin gradient:

- High Gradient ( > or = 1.1 g/dl)

• Cirrhosis
• Alcoholic Hepatitis
• Cardiac Failure
• Fulminant Hepatic Failure
• Portal-vein Thrombosis

- Low Gradient ( < 1.1 g/dl)

• Peritoneal Carcinomatosis
• Pancreatic ascites
• Biliary ascites
• Peritoneal Tuberculosis
• Nephrotic Syndrome
• Serositis
• Bowel obstruction or infarction

Principles of fluid analysis.

Pleural effusion.
-Perform diagnostic thoracentesis
-Measure the pleural fluid protein and LDH.

If the pleural fluid or serum protein > 0.5 and the serum LDH >0.6 , its > 2/3rd upper normal serum limit

Hence, its Exudate cause and its requires further investigation.

If the following criteria was not met, then its transudate causes such as, chronic heart failure, cirrhosis or nephrosis.

In the exudate causes, further investigation such as

-Pleural fluid glucose
-Pleural fluid amylase
-Pleural fluid cytology
-Obtain differential count
-Culture stain
-Marker for tuberculosis.

- If serum amylase is elevated, consider esophageal rupture, pancreatic pleural effusion or even malignancy

- If glucose is < 60mg/dl, consider malignancy, bacterial infections, rheumatoid pleuritis.

- There are times where by diagnosis cant be obtained, in this cases, consider pulmonary embolus, if it is still not the diagnosis perform a pleural fluid marker for tuberculosis.

- If there is difficulty in obtaining the diagnosis still, consider thoracoscopy or open pleural biopsy.


Ascites fluid

-Diagnostic paracentesis about 50- 100 ml is essential, using a 22 gauge needle in linea alba 2 cm below the umbilicus.

- Routine evaluation includes inspection, protein albumin, glucose, cell count, and differential, culture and cytology. In selected cases check amylase, LDH, triglycerides, and also culture for TB.

- Ascites due to CHF( example pericardial constriction) may require evaluation by right- sided heart catheterization.
- Differential diagnosis:- more than 90% of cases due to cirrhosis, neoplasm, CHF and tuberculosis.

- Fluid characteristics can be divided into many causes based upon mainly the appearance, the protein content, serum- ascities albumin gradient, RBC and WBC.

- Example, in a case of cirrhosis, appearance is straw colour, protein is < 2.5g/dl, serum ascities albumin gradient > 1.1, RBC is low, and WBC < 250

- Spontaneous bacterial peritonitis, which is one of the complication of ascities can be diagnosed by doing a fluid analysis, where by there will be low ascetic protein concentration. Diagnostic suggesting by ascetic fluid when the PMN count ( polymorphonuclear) > 250 miu/L. It is comfirmed by positive culture of usually Enterobacteriaceae, group D streptococci, Streptococcus pneumoniae, S. viridans.

- Efficacy of the treatment demonstrated by marked decrease in ascetic PMN count after 48 hours.