Laboratory diagnosis of Ascitic fluid analysis

1. ASCITIC FLUID EXAMINATION
Dr Abdul Hafeez Kandhro
Senior Lecturer
B.Sc, M.Sc; Medical Technology,
M.Phil Biochemistry
Ph.D. Medical Technology
(Mahidol University, Bangkok , Thailand)

2. Peritoneal fluid (ascitic fluid) analysis
• The peritoneum is a tough semi-permeable
membrane lining abdominal and visceral cavities.
• It encloses, supports and lubricates organs within
the cavity.
• Paracentesis is effectively the analysis of ‘Ascites’
the abnormal accumulation of fluid within the
abdomen.

3. Peritoneal fluid (ascitic fluid) analysis
• The peritoneum is important in osmoregulation
– Passive diffusion of water and solute (up to a certain
size)
– Maintains osmotic and chemical equilibrium with
blood and lymph
• Ascites develops either from:
– Increased accumulation
• Increased capillary permeability
• Increased venous pressure
• Decreased protein (oncotic pressure)
– Decreased clearance
• Increased lymphatic obstruction

4. Peritoneal fluid (ascitic fluid) analysis
• Causes
• Transudate (<30g/L protein) (Systemic disease)
– Liver (Cirrhosis)
– Cardiac e.g. RHF, CCF, SBE right heart valve disease and
constrictive Pericarditis
– Renal failure
– Hypoalbuminaemia (nephrosis)
• Exudate (>30g/L protein) (Local disease)
– Malignancy
– Venous obstruction e.g. Budd-Chiari, Schistosomiasis
– Pancreatitis
– Lymphatic obstruction
– Infection (especially TB)

6. Peritoneal fluid (ascitic fluid) analysis
• A 1 or 1.5 inch 21 or 22 gauge needle can be used for diagnostic paracentesis in
lean patients
• A 3.5 inch 22 gauge needle can be used in obese patients.
• Larger caliber (15 or 16 gauge), multi-hole needles can be used for therapeutic
paracentesis.
• Plastic-sheathed catheters can be shaved off into the peritoneal cavity and can
lead to the need for laparoscopy or laparotomy to retrieve the piece that was
shaved off.

8. Peritoneal fluid (ascitic fluid) analysis
• Physical Examination
• Appearances
• Straw: Serous effusion (clear = transudate; cloudy =
exudates)
• Bloody: Trauma, malignancy, haemorrhagic pancreatitis,
perforated peptic ulcer
• Turbid: SBP, perforated Viscous
• Chylous (milky): Malignancy, lymphoma, tuberculosis,
parasitic
• pH
• Specific Gravity

11. Peritoneal fluid (ascitic fluid) analysis
• Biochemical Examination
• Serum-Ascites Albumin Gradient (SAAG)
• The SAAG indirectly measures portal pressure and can be
used to determine if ascites is due to portal hypertension:
SAAG= serum albumin–ascitic fluid albumin
NOTE: ensure all values are in g/L

12. Peritoneal fluid (ascitic fluid) analysis
• Biochemical Examination
• Serum-Ascites Albumin Gradient (SAAG)
• High SAAG >11g/L causes= PORTAL HYPERTENSION
Portal hypertension causes
a) Pre-hepatic: portal vein thrombosis
b) Hepatic: cirrhosis, chronic hepatitis
c) Post-hepatic: right heart failure, constrictive pericarditis, Budd-
Chiari syndrome
Low SAAG<11g/L causes = OTHER
Other Causes
a) Peritoneal disease: intra-abdominal malignancy, peritoneal
dialysis, TB
b) Hypoalbuminaemia: nephrotic syndrome, malnutrition, protein-
loosing enteropathy
c) Other: pancreatitis/pancreatic pseudocyst, haemoperitoneum,
myxoedema, chylous ascites

13. Peritoneal fluid (ascitic fluid) analysis
Biochemical Examination
LDH
• Normally, LDH molecule is too large to enter the ascitic
fluid readily from blood.
• [LDH] in ascitic fluid is usually less than one half of the
serum level (uncomplicated cirrhotic ascites)
• In SBP, ascitic fluid LDH level rises because of the release
of LDH from neutrophils.
• In secondary peritonitis, LDH ascitic fluid > LDH serum ,
higher than those in SBP

14. Peritoneal fluid (ascitic fluid) analysis
Biochemical Examination
Amylase
• In uncomplicated cirrhotic ascites, amylase ascitic fluid
usually is one half that of the serum value, approximately
50 U/L.
• In patients with acute pancreatitis or intestinal
perforation (with release of luminal amylase into the
ascitic fluid), the fluid amylase concentration is
• elevated markedly, usually greater than 2000 U/L
• approximately five-fold greater than simultaneous serum
values

15. Peritoneal fluid (ascitic fluid) analysis
Biochemical Examination
Adenosine Deaminase (ADA)
• ADA levels are used for diagnosing tuberculosis in several
locations.
• ADA levels showed high sensitivity (100%) and specificity
(97%) using cut-off values from 36 to 40 IU/L in diagnosis
tuberculosis ascites.

16. Peritoneal fluid (ascitic fluid) analysis
Microscopic Examination
Cells
MC&S: identify infective causes
Cell count
▪ Neutrophils (normally <0.25x109): raised in spontaneous
bacterial peritonitis)
▪ Lymphocytes (normally<0.5x109): raised in inflammation,
TB, malignancy
Gram stain—for direct observation of bacteria or fungi under
a microscope; there should be no microbes present in
peritoneal fluid.
ZN stain: for Mycobacterium tuberculosis bacilli

19. Peritoneal fluid (ascitic fluid) analysis
Fluid Culture
• New method - blood culture bottles – with ascitic fluid
detects bacterial growth in approximately 80%.
• Gene probes are now commercially available for the
detection of bacteremia; hopefully, they will also lead to
rapid (30-minute) and accurate detection of organisms in
ascitic fluid.
• Culture will continue to be required, however, for
assessment of the susceptibility of the organism to
antibiotics

20. Peritoneal fluid (ascitic fluid) analysis
Cytological Exam
• Have a sensitivity of 60% in detecting malignant ascites.
• Why ?
• Because malignant ascites is caused by:
• peritoneal carcinomatosis
• massive liver metastases
• hepatocellular carcinoma superimposed on cirrhosis
• Chylous ascites caused by lymphoma

22. Peritoneal fluid (ascitic fluid) analysis
Molecular Exam
• Tuberculosis
• Other Bacteria and their species