Peritoneal Fluid Analysis• used to diagnose cause of peritoneal fluid accumulation (ascites) and/or inflammation of the peritoneum (peritonitis)1. initial tests:2. fluid albumin level3. cell count and differential4. appearance
fluid accumulate in the abdominalcavity1. imbalance of pressure within blood vessels VS. protein in blood accumulation of fluid (transudate) (CHF/ cirrhosis)2. Injury/inflammation of the peritoneum cause abnormal collection of fluid (exudate). results of: infection, malignancies (metastatic cancer, lymphoma, mesothelioma), or autoimmune disease.
Exudates are associated w/ diseases:• Infectious diseases: viruses, bacteria, or fungi.• Inflammatory conditions: peritonitis due to certain chemicals, irradiation & rarely autoimmune disorder• Malignancies: mesothelioma, hepatoma, lymphoma, or metastatic cancer• Pancreatitis
Additional tests on exudate fluid:• Peritoneal fluid glucose, amylase, tumor markers• Microscopic examination: if infection/cancer is suspected.• Gram stain – for bacteria or fungi• Bacterial culture and sensi: to detect any microorganisms and guide abx therapy• AFB smear & culture for viruses, mycobacteria & parasites
Cellno ‘standardized’ ascites fluid cell countGenerally accepted ‘cut-off’ for upper-limits of normal for infection is less than 250 PMNs/mm31. PMNs usually constitute 70% of the cell count. spontaneous bacterial peritonitis: PMN’s predominance2. tuberculous ascites: lymphocytic predominance.Bloody ascites fluid is usually the result of traumatic tap
• Peritoneal fluid analysis may be ordered when suspecting a condition or disease that is causing peritonitis or ascites.• It may be ordered when someone has:1. Ascites of unknown origin2. Abdominal pain and tenderness3. Intestinal perforation4. Suspected intra-abdominal malignancy
Exudates, Transudates and Ratios:We are always taught in medical school that the serum:ascites LDH and protein ratios : to differentiate exudates and transudatesThe literature shows that these calculations are actually not all that helpfulThe SAAG become more favored in helping to characterize ascites fluid.
Transudate• Physical characteristics: fluid is clear• Albumin level: low (typically evaluated as the difference between serum albumin and peritoneal fluid albumin (SAAG)• Values > 1.1 g/dL are considered evidence of a transudate• Cell count—few cells are present• <30g/L protein
Exudate• Physical characteristics—fluid appear cloudy• Albumin level—higher than in transudates (SAAG less than 1.1 g/dL)• Cell count—increased• >30g/L protein
The Serum-Ascites Albumin Gradient: The concept surrounds oncotic-hydrostatic balance Simple calculation: Serum albumin – Ascites albumin= SAAG
Glucose:In uncomplicated ascites, usually similar to serum levels.In later SBP (but often not in early), ascites glucose levels can drop to as low as zero mg/dl secondary to bacterial consumption
Cultures and Gram Stains:Cultures should be obtained by inoculating blood culture bottles at the bedside to improve sensitivity to at least 80%, compared with 50% for ‘conventional’ culture methods.Gram stains are useless on ascites fluid – about as useful as asking for a Gram stain on blood cultures to look for bacteremia. The concentration of organisms just won’t be high enough to see something on Gram stain.
Cytologyhelpful only in diagnosing peritoneal carcinomatosis. sensitivities up to 100%.Does not detect most other intra-abdominal cancers because most of the cancers do not frequently metastasize to the peritoneum.Cytology helps only if you’re suspicious of a cancer that has spread to the peritoneumNegative cytology does not rule out cancers such as HCC or liver metastases, which commonly cause ‘malignant ascites.’