To help diagnose the cause of peritonitis, an inflammation of the membrane lining the abdomen, and/or peritoneal fluid accumulation, where fluid builds up in the abdomen or around internal organs (called ascites)
When you have abdominal pain and swelling, nausea, and/or fever and your healthcare practitioner suspects you have peritonitis or ascites
A peritoneal fluid sample obtained by inserting a needle into the abdominal cavity
You will be asked to empty your bladder prior to sample collection.
Peritoneal fluid is a liquid that acts as a lubricant in the abdominal cavity. It is found in small quantities (generally 5-20 mL) between the layers of the peritoneum that line the abdominal wall. Peritoneal fluid acts to moisten the outside of the organs and to reduce the friction of organ movement during digestion and movement.
A variety of conditions and diseases can cause inflammation of the peritoneum (peritonitis) and/or excessive accumulation of peritoneal fluid (peritoneal effusion or ascites). Peritoneal fluid analysis is a group of tests that evaluate this liquid to determine the cause of the increased fluid.
The two main reasons that fluid may collect in the abdominal cavity are:
Determining the type of fluid present (transudate or exudates) is important because it helps narrow down the possible causes of fluid buildup or inflammation. Healthcare practitioners and laboratorians use an initial set of tests, including cell count, serum and fluid albumin levels, and appearance of the fluid, to distinguish between transudates and exudates. Once the fluid is determined to be one or the other, additional tests may be performed to further pinpoint the disease or condition causing ascites.
Peritoneal fluid analysis is used to help diagnose the cause of fluid buildup in the abdomen (ascites) and/or inflammation of the peritoneum (peritonitis). There are two main reasons for fluid accumulation, and an initial set of tests is used to differentiate between the two types of fluid that may be produced, transudate or exudate. These tests typically include:
Transudate—an imbalance between the pressure within blood vessels (which drives fluid out of the blood vessel) and the amount of protein in blood (which keeps fluid in the blood vessel) can result in accumulation of fluid (called a transudate). Transudates are most often caused by congestive heart failure , nephrotic syndrome, or hepatic cirrhosis. If the fluid is determined to be a transudate, then usually no more tests on the fluid are necessary.
Exudate—injury or inflammation of the peritoneum may cause abnormal collection of fluid (called an exudate). Exudates are associated with infections, malignancies, pancreatitis, ruptured gallbladder, or autoimmune disease. Laboratory tests may be performed to determine one of the following conditions:
Additional testing on exudate fluid may include:
Peritoneal fluid analysis may be ordered when a healthcare practitioner suspects that a person has a condition or disease that is causing peritonitis and/or ascites. It may be ordered when someone has:
Test results can help distinguish between types of peritoneal fluid and help diagnose the cause of fluid accumulation. The initial set of tests performed on a sample of peritoneal fluid helps determine whether the fluid is a transudate or exudate. Findings may include:
Most ascitic fluids are transudates and are caused by either congestive heart failure or hepatic cirrhosis. Typical fluid analysis results include:
Exudates can be caused by a variety of conditions and diseases and usually require further testing to aid in the diagnosis. Infections, trauma, various cancers, or pancreatitis may cause exudates. The following is a list of additional tests that a healthcare practitioner may order depending on the suspected cause and typical results.
Physical characteristics – the normal appearance of a peritoneal fluid sample is usually straw-colored and clear. Abnormal appearances may give clues to conditions or diseases present and may include:
Chemical tests – tests that may be performed in addition to albumin may include:
Microscopic examination – may be performed if infection or cancer is suspected; normal peritoneal fluid has small numbers of WBCs but no red blood cells (RBCs) or microbes. Results of an evaluation of the different kinds of cells present may include:
Infectious disease tests – tests may be performed to look for microbes if an infection is suspected.
Other less common tests for infectious diseases may be performed to identify a virus, mycobacteria (such as the mycobacterium that causes tuberculosis), or a parasite as the cause of an infection and fluid accumulation.
A blood glucose or albumin may be ordered to compare concentrations with those in the peritoneal fluid. If a healthcare practitioner suspects that you have a systemic infection, then a blood culture may be ordered in addition to the peritoneal fluid analysis.
Paracentesis is the removal of peritoneal fluid from the abdominal cavity with a needle, tubing, and a container that may have a vacuum. The individual receiving that test is positioned lying down with the head of the bed raised. A local anesthetic is applied, then the healthcare practitioner inserts the needle into the abdominal cavity and the sample is removed.
Yes. Sometimes it will be performed to drain excess peritoneal fluid – to relieve pressure in the abdomen. The volume of fluid removed may be large – sometimes as much as four liters (1 gallon) or more. This may need to be repeated periodically with some diseases.
Yes. If abdominal bleeding is suspected but is not evident because there is no swelling of the abdomen, a peritoneal lavage may be performed. This is done by inserting a small tube (catheter) into the peritoneal space, infusing a small amount of sterile fluid, and then withdrawing the fluid to see if any blood is present. A cell count is usually performed on a sample of the fluid.
Sources Used in Current Review
Wolf, D. (Updated 2014 December 10). Chylous ascites. Medscape Reference. Available online at http://emedicine.medscape.com/article/185777-overview#showall. Accessed 9/9/2016.
Christensen, B. (Updated 2014 December 15). Serum ascites albumin gradient (SAAG) interpretation. Medscape Reference. Available online at http://www.mayoclinic.org/diseases-conditions/peritonitis/basics/definition/con-20032165. Accessed 9/9/2016.
Lal, S. K. (Updated 2015 February 11). Peritoneal fluid analysis. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003626.htm. Accessed 9/9/2016.
Mayo Clinic Staff. (Updated 2015 March 23). Peritonitis. Mayo Clinic. Available online at http://www.mayoclinic.org/diseases-conditions/peritonitis/basics/definition/con-20032165. Accessed 9/9/2016.
Lal, S. K. (2015 August 14). Ascites. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000286.htm. Accessed 9/9/2016.
Shlamovitz, G. L. (Updated 2016 July 28). Paracentesis. Medscape Reference. Available online at http://emedicine.medscape.com/article/80944-overview. Accessed 9/9/2016.
Bhutta RA, Syed NA, Ahmad A. Peritoneal fluid analysis (Ascitic fluid analysis, Peritoneal tap or abdominal paracentesis, or abdominal tap) part 3. Available online at http://www.labpedia.net/test/227. Accessed Sept 2016.
Shah, Rahil. Ascites. Medscape. Available online at http://emedicine.medscape.com/article/170907-overview#a5. Accessed Sept 2016.
Sources Used in Previous Reviews
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 694-699.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1535-1536.
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition]. Pp 1448-1449.
Forbes, B. et. al. (© 2007). Bailey & Scott's Diagnostic Microbiology, Twelfth Edition: Mosby Elsevier Press, St. Louis, Missouri. Pp 904 – 913.
Van Voorhees, B. (2007 January 22, Updated). Peritoneal fluid analysis. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003626.htm. Accessed on 6/21/08.
Lehrer, J. (2006 November 14, Updated). Peritonitis – spontaneous. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000648.htm. Accessed on 6/21/08.
(2002 May 13). National Cancer Institute. Mesothelioma: Questions and Answers [On-line information]. Available online at http://www.cancer.gov/cancertopics/factsheet/sites-types/mesothelioma. Accessed on 7/3/08.
(2008 March 22, Updated). ACS. Malignant Mesothelioma Detailed Guide [On-line information]. Available online at http://www.cancer.org/docroot/CRI/content/CRI_2_4_7x_CRC_Malignant_Mesothelioma_PDF.asp. Accessed on 7/3/08.
Carl Kjeldsberg and Joseph Knight. Body Fluids. Third edition. ASCP Press. Pp. 223-253.
Shlamovitz, G. and Shah, N. (Updated 2012 May 9). Paracentesis. Medscape Reference. [On-line information]. Available online at http://emedicine.medscape.com/article/80944-overview. Accessed June 2012.
Dugdale, D. (Updated 2011 February 4). Peritoneal fluid analysis. MedlinePlus Medical Encyclopedia. [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003626.htm. Accessed June 2012.
Daley, B. et. al. (Updated 2011 March 29). Peritonitis and Abdominal Sepsis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/180234-overview. Accessed June 2012.
Zieve, D. (2011 October 16). Ascites. MedlinePlus Medical Encyclopedia . [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000286.htm. Accessed June 2012.
Wolf, D. and Raghuraman, U. (Updated 2011 March 21). Chylous Ascites. Medscape Reference. [On-line information]. Available online at http://emedicine.medscape.com/article/185777-overview#showall through http://emedicine.medscape.com. Accessed June 2012.
Herrine, S. (Revised 2009 July). Ascites. Merck Manual for Healthcare Professionals. [On-line information]. Available online through http://www.merckmanuals.com. Accessed June 2012.