Effusion Tests

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Effusions are defined as excessive accumulations of fluid in body cavities lined with serous or synovial membranes. In health, both serous and synovial fluids are clear to pale yellow in color. Effusions are named for their associated cavities. Therefore, the pericardial cavity produces pericardial effusions, the peritoneal cavity has peritoneal effusions, pleural effusions are found in the pleural cavity, and synovial effusions are related to the cavities of various synovial joints.

Serous cavity effusions, fluids contained within the closed cavities of the body, can be differentiated as transudates or exudates. Transudates are fluids that are pressed through a membrane or tissue into the space between the cells of the tissue. Transudates are usually characterized as low-protein, cell-free fluids occurring due to a systemic disease. Exudates are effusions resulting from damage to cells or cell membranes. Exudates are usually seen in malignancies, infection, and inflammations and contain cells, cell debris, and proteins.

Both the physical properties and microscopic characteristics of effusions can be analyzed for diagnostic purposes. Physical properties include color, clarity, volume, and clotting ability. Color and clarity changes can indicate a range of disease processes from perforated ulcers to metastatic cancer. The ability for a serious fluid to clot indicates the presence of an inflammatory reaction. Most cavities contain only a small amount of fluid or effusions. An increase or buildup of effusions can indicate mechanical abnormalities related to capillary permeability and/or serous or synovial membrane damage. Microscopic examination of effusions is performed to identify and measure the presence of cells and microorganisms. Chemical testing for a wide variety of effusion constituents such as glucose, protein, enzymes, and tumor markers can be performed on request.

Effusion samples are obtained via needle aspiration. Centesis is the suffix that denotes "puncture and aspiration of." The name of each sample collection technique is taken from the structure or cavity involved. Therefore, pericardial effusions are collected via pericardiocentesis; since the lungs are located in the thoracic cavity, thoracentesis is performed to withdraw pleural effusions; aspiration of peritoneal fluid is accomplished via paracentesis; and synovial effusions, usually withdrawn from joint spaces, are taken by arthrocentesis. The diagnostic significance of each type of effusion is discussed individually.

Pericardial Effusion Tests

Pericardial effusions are withdrawn from the pericardial sac via pericardiocentesis. The chief indication for pericardiocentesis and pericardial effusion analysis is an abnormal accumulation of fluid in the pericardial space. Contraindications for this test include bleeding disorders and an uncooperative patient. Risks attendant to this procedure are laceration of the coronary artery, needle-induced ventricular dysrhythmias, pneumothorax, and introduction of infective agents from the skin.

Pericardial effusions are routinely analyzed in relation to gross appearance, red blood cell count, and a white blood cell count and differential, glucose levels, and blood. These analyses provide valuable diagnostic information related to all types of pericarditis. Cytologic examination of pericardial effusions is performed to detect malignant cells.

Normal Range

Red blood cells None White blood cells <1000/mm3 Cytology No abnormal cells

Variations from Normal. Bloody pericardial effusion, not associated with pericardiocentesis trauma, is seen in hemorrhagic pericarditis, metastatic cancer, aneurysms, and tuberculosis. The presence of red blood cells, an elevation in specific types of white cells, and variations in glucose levels provide diagnostically significant information. Bacterial, tubercular, or fungal pericarditis is evidenced by an elevated white count, predominantly neutrophils; the presence of red blood cells; and a decrease in glucose levels. The presence of red cells and an elevated white count, with lymphocytes dominant, points to a viral pericarditis.

Other diseases that can cause pericardial effusion include Dressler's syndrome, a postmyocardial infarction syndrome characterized by fever, pericarditis, pleurisy, and joint pain; hemorrhagic problems due to trauma or anticoagulant therapy; and leukemia or lymphoma as indicated by the presence of abnormal cells, kidney failure, or rheumatic disease. Table 9-1 summarizes the diseases associated with variations of substances present in pericardial effusions.

Interfering Circumstances. Contamination of the effusion sample with skin cells or pathogens, and blood in the sample due to a traumatic needle puncture, alter test results. Hyperglycemia and hypoglycemia also interfere with effusion analysis.

Table 9-1. Pericardial Effusions

Disease

Increased/Presence

Decreased

Dressler's syndrome

Red cells

White cells, neutrophils

Bacterial pericarditis

Red cells

Glucose

White cells, neutrophils

Fungal, tuberculous

Red cells

pericarditis

White cells, lymphocytes

Malignancy

Red cells, abnormal cells

Glucose

Rheumatoid disease;

Red cells

Glucose

systemic lupus

White cells

erythematosus

Viral pericarditis

Red cells

White cells, neutrophils

Kidney failure, uremia

Red cells, white cells

Peritoneal Effusion Tests

Peritoneal effusions are withdrawn from the peritoneal cavity via paracentesis. The chief indication for paracentesis is the abnormal accumulation of fluid in the peritoneal cavity. The fluid, know as peritoneal effusion or ascitic fluid, is analyzed to determine the cause of the effusion. Contraindications for this test include coagulation abnormalities or bleeding tendencies. Risks attendant to this procedure are vascular collapse if a large volume of peritoneal fluid is removed, hepatic coma in the presence of chronic liver disease, and peritonitis.

Peritoneal effusions are routinely evaluated for color, clarity, red blood cell count, and white blood cell count with differential. Levels of alkaline phosphatase, ammonia, amylase, carcinoembryonic antigen (CEA), glucose, and protein can also be measured on request. Cytologic exams are used to detect malignancies. Suspected ruptured or punctured bladder calls for urea and creatinine measurement. Variations in each of the tested substances are related to specific diagnoses.

Normal Range

Clarity and color Clear and light yellow, serous <50 mL

Red blood cells None

White blood cells <300 wbc/ JJ./L with <25% PMNs

Alkaline phosphatase Adult male 90-240 U/L

Female <45 yr 76-196 U/L

Female >45 yr 87-250 U/L

Amylase 138-404 U/L

CEA Negative

Glucose 70-100 mg/dl

Variations from Normal. The mere presence of abnormal amounts of peritoneal fluid is pathological. The color of the effusion supports a variety of diagnoses. Milk-colored (chylous) effusion is associated with blocked thoracic lymph ducts, trauma, cirrhosis, pancreatitis, or tuberculous peritonitis. The two most common causes of chylous peritoneal effusions are malignant lymphoma and carcinoma. Cloudy fluid indicates an inflammatory condition such as pancreatitis, bacterial peritonitis, or neoplasm. Effusion tinged green or stained with bile is consistent with a ruptured gallbladder or perforated intestines. Patients with cirrhosis of the liver present with a light yellow effusion.

The presence of red blood cells in the peritoneal effusion is consistent with neoplasms, tuberculosis, or intraabdominal trauma such as gunshot or stab wounds. Increased white blood cells can indicate cirrhosis of the liver and bacterial peritonitis. Table 9-2 summarizes diseases related to increases and decreases of alkaline phosphatase, ammonia, amylase, carci-noembryonic antigen, creatinine, glucose, and urea in peritoneal effusions.

Interfering Circumstances. Contamination of the effusion sample with skin cells or pathogens, and blood in the sample due to a traumatic needle puncture, alter test results. Hyperglycemia and hypoglycemia also interfere with effusion analysis.

Table 9-2. Peritoneal Effusions

Disease Increased Decreased

Table 9-2. Peritoneal Effusions

Disease Increased Decreased

Abdominal malignancy

Red cell count, Glucose

carcinoembryonic

antigen

Gastrointestinal

Amylase, ammonia,

necrosis, perforation,

alkaline phosphatase

or strangulation

Pancreatitis, pancreatic

Amylase

trauma, pancreatic

pseudocyst

Tuberculous peritonitis

Lymphocyte count, Glucose

positive acid-fast

bacillus smear and

culture

Urinary bladder rupture

Ammonia, creatinine,

or perforation

urea

Pleural Effusion Tests

Pleural effusions are withdrawn from the pleural space via thoracentesis. The chief indication for thoracentesis and pleural effusion analysis is an abnormal accumulation of fluid in the pleural space. Removing this fluid has both diagnostic and therapeutic benefits. Therapeutic thoracentesis is accomplished to relieve pain and dyspnea. Diagnostic thoracentesis allows for identification of diseases that may cause pleural effusion, as well as better radiographic visualization of the lung. Contraindications for this test include bleeding disorders and an uncooperative patient. Risks attendant to this procedure are pneumothorax, interpleural bleeding, pulmonary edema, and reflex hypertension.

Pleural effusions can be classified as transudates or exudates. It is important to analyze effusions in light of the difference between these two classifications. Congestive heart failure, cirrhosis of the liver, and nephrotic syndromes usually present with pleural transudates. Pleural exudates are associated with pneumonia, empyema, tuberculosis, pulmonary infarction, and malignancies.

Pleural effusions are routinely evaluated for gross color, clarity, clotting, red blood cell count, and white blood cell count with differential. Levels of amylase, CEA, glucose, lactate dehydrogenase (LDH), and protein are also measured. The pH of pleural effusions is also identified. Variations in each of the tested substances are related to specific diagnoses. Gram stain and culture and sensitivity tests are performed in order to identify the pathogens responsible for infections. Cytologic exams are used to detect malignancies.

Normal Range

Red blood cells Few

White blood cells 0-<1000/mm3 (mainly lymphocytes)

Glucose Adults Children Newborns

70-115 mg/dl 60-100 mg/dl 30-80 mg/dl 70-207IU/L 7.4 or greater 3.0 g/dl

Protein

Protein

Variations from Normal. The mere presence of abnormal amounts of pleural fluid is pathological. The color and gross appearance of the effusion can indicate empyema or the presence of chyle, the product of digestion, in the pleural cavity. Thick, foul-smelling, puslike fluid is related to empyema. Chylothorax is evidenced by an opalescent, pearly pleural effusion.

The presence of red blood cells and white blood cells in the pleural effusion is consistent with pneumonia, pulmonary tuberculosis, pancreatitis, tuberculous empyema, pulmonary infarction, carcinoma, or thoracic trauma. Lymphocytes are usually seen in pulmonary tuberculosis and carcinoma. Effusions caused by pneumonia, pancreatitis, and bacterial or tuberculous empyema are rich in neutrophils. Table 9-3 summarizes diseases related to variations in amylase, CEA, glucose, lactate dehydrogenase, pH, and protein levels in pleural effusions. Note that several diagnoses exhibit the same increases and decreases. Other laboratory results such as cell count, AFB smear and culture, and cytological examinations provide additional information needed for a definitive diagnosis.

Interfering Circumstances. Contamination of the effusion sample with skin cells or pathogens, and blood in the sample due to a traumatic needle puncture, alter test results. Variations in blood glucose levels also interfere with effusion analysis.

Table 9-3. Pleural Effusions

Disease

Increased

Decreased

Carcinoma

Protein, lactate

pH, glucose

dehydrogenase (LDH),

carcinoembryonic

antigen

Empyema, tuberculous

Protein, LDH

pH, glucose

Esophageal rupture

Amylase

PH

Pancreatitis

Protein, LDH,

pH

amylase

Pulmonary infarction

Protein, LDH

pH

Tuberculosis

Protein, LDH

pH, glucose

Synovial Effusion Tests

Synovial effusions are withdrawn from joint cavities by way of arthrocen-tesis. The most frequently aspirated joint is the knee, but samples may be obtained from other synovial joints if needed. The chief indication for arthrocentesis and synovial effusion analysis is to determine the type or cause of joint disorders. Contraindications for this test include skin and/or wound infections in the area of the needle puncture. Risks attendant to this procedure are joint infection and/or joint hemorrhage.

Synovial effusions are routinely evaluated visually and microscopically for gross appearance, cellular content, crystals, and granulocytes that contain inclusion bodies. Inclusion bodies associated with specific diseases are substances that are present in the cytoplasm of granulocytes. Examples of white cells with inclusion bodies are (1) LE cells, neutrophils containing an inclusion substance called a "round body," which is the nucleus of another WBC; (2) RA cells, neutrophils with dark granules in the cytoplasm that consist of immune complexes; and (3) rice bodies, inclusion bodies that resemble polished rice.

Other synovial effusion studies are microbial studies, gram stain, culture and sensitivity, and immunologic tests to identify the presence of rheumatoid factor (RF) or antinuclear antibodies (ANAs). Levels of glucose, lactate, protein, and uric acid are also measured. Variations in each of the tested substances are related to specific diagnoses.

Normal Range

Red blood cells White blood cells

Neutrophils

Antinuclear antibodies

Crystals

Glucose

Lactate

Protein

Rheumatoid factor

<2000/mm3 <200/mm3

No abnormal white cells or inclusions

Negative

None present

Within 10 gm/dl of serum glucose value 5-20 mg/dl <3 g/dl Negative

Uric acid

Children 2.5-5.5 mg/dl

Variations from Normal. The presence of specific types of white blood cells in the synovial effusion can be diagnoses specific. An overall elevation of white cells, with a normal differential count, is consistent with osteoarthritis and degenerative joint disease. A high percentage of neutrophils indicates acute bacterial infectious arthritis. An elevated red blood cell count coupled with increased protein levels are diagnostic for hemophilic arthritis, joint trauma, and joint tumor. Effusions are examined for various types of crystals. Crystals are seen in diseases such as gout, chronic joint effusions, and synovitis. Table 9-4 summarizes variations in synovial effusion constituents for gout, rheumatoid arthritis, systemic lupus erythematosus involving the joint, and tuberculous arthritis.

Table 9-4. Synovial Effusions

Disease Increased/Present Decreased

Table 9-4. Synovial Effusions

Disease Increased/Present Decreased

Gout

White cell count, neutrophils, uric acid

Glucose

Rheumatoid arthritis

White cell count, neutrophils, lactate, protein rheumatoid factor (present), rice cells RA cells

Glucose

Systemic lupus erythematosus

White cell count, neutrophils, protein antinuclear antibody (present) LE cells

Glucose

Tuberculous arthritis

White cell count, neutrophils, lactate, rice cells (present)

Glucose

Interfering Factors. Contamination of the effusion sample with skin cells or pathogens, or blood in the sample due to a traumatic needle puncture, alter test results. Hyper- and hypoglycemia also interfere with effusion analysis. Improper handling of the sample in relation to temperature and room air exposure adversely affect test results.

Secretions of the stomach are often referred to as "gastric juices." Gastric secretions prepare food for absorption, initiate the digestion of protein, and assist in vitamin B12 absorption. Gastric secretions consist of pepsinogen, pepsin, hydrochloric acid, an alkaline substance that protects the lining of the stomach from damage, electrolytes, and enzymes such as gastric lipase.

Specimen collection for gastric content analysis is accomplished by inserting a nasogastric tube (NG) into the stomach and aspirating gastric secretions. Although risks associated with this procedure are minimal, some individuals may experience extreme anxiety prior to and during tube placement.

The gastric secretion analysis test is covered in this chapter. Analyzing the quantity, quality, and characteristics of gastric secretions can provide diagnostic information concerning ulcers, obstruction diseases, pernicious anemia, and cancer of the stomach.

Gastric secretions are analyzed for blood, color, mucus, and pH levels. Microscopic analysis involves evaluating the specimen for red blood cells, white blood cells, epithelial cells, bacteria, yeast, and parasites.

Normal Range

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