2. 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 level
3. cell count and differential
4. appearance
3. fluid accumulate in the abdominal
cavity
1. 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.
4. 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
5. 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
6. Cell
no ‘standardized’ ascites fluid cell count
Generally accepted ‘cut-off’ for upper-limits of normal
for infection is less than 250 PMNs/mm3
1. PMNs usually constitute 70% of the cell count.
spontaneous bacterial peritonitis: PMN’s
predominance
2. tuberculous ascites: lymphocytic predominance.
Bloody ascites fluid is usually the result of traumatic tap
7. • 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 origin
2. Abdominal pain and tenderness
3. Intestinal perforation
4. Suspected intra-abdominal malignancy
8. Exudates, Transudates and Ratios:
We are always taught in medical school that the
serum:ascites LDH and protein ratios : to
differentiate exudates and transudates
The literature shows that these calculations are
actually not all that helpful
The SAAG become more favored in helping to
characterize ascites fluid.
9. 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
10. 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
11. The Serum-Ascites Albumin Gradient:
The concept surrounds oncotic-hydrostatic balance
Simple calculation: Serum albumin – Ascites albumin= SAAG
12. 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
13. 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.
14. Cytology
helpful 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 peritoneum
Negative cytology does not rule out cancers
such as HCC or liver metastases, which
commonly cause ‘malignant ascites.’
