Peritoneal Fluid Analysis

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.
  • 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
  • Ascitesdevelops either from:
    • Increased  accumulation
      • Increased capillary permeability
      • Increased venous pressure
      • Decreased protein (oncotic pressure)
    • Decreased clearance
      • Increased lymphatic obstruction

Cause

  • 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)

Analysate interpretation

Gross appearance

  • Clear to pale yellow
  • Normal
  • Milk-coloured (Chylous)
  • Malignant tumour, lymphoma, TB
  • Parasitic infection, hepatic cirrhosis
  • Cloudy/turbid
  • Peritonitis, Primary bacterial infection
  • Perforated bowel, appendicitis, pancreatitis
  • Strangulated or infarcted bowel
  • Bloody tap
  • Benign or malignant tumour
  • Haemorrhagic pancreatitis, perforated ulcer

Paracentesis biochemistry

Levels Interpretation
  • Triglyceride
  • Elevated
  • Malignant tumour, lymphoma, TB
  • Parasitic infection, hepatic cirrhosis
  • Protein
  • 0.3-4.0g/dL
  • >4g/dL
  • Normal
  • TB, SBP
  • Glucose
  • 7-10
  • <6
  • Normal
  • TB and malignancy
  • Amylase
  • 50% of serum level
  • Increased (Up to 5x serum level
  • Normal
  • Pancreatitis, pancreatic pseudocyst, pancreatic trauma or Intestinal strangulation
  • Alkaline phosphatase
  • Increased
  • Small bowel perforation and strangulation

Exudate Serum:Ascites Ratios

  • Evidence for these ascites:serum ratios is controversial
    • Ascitic fluid protein/Serum Protein >0.5
    • Ascitic Fluid LDH/Serum LDH >0.6
    • Ascitic Fluid LDH >400
  • Presence of any 2 of these three findings is usually associated with TB, Malignancy or Pancreatitis
  • Absence of all three usually indicates hepatic cause

The Serum-Ascites Albumin Gradient (SAAG)

  • The SAAG has become more favored in helping to characterize ascites fluid
  • The concept surrounds oncotic-hydrostatic balance
  • Simple calculation:
    • Serum albumin – Ascites albumin= SAAG
SAAG > 1.1 mg/dl SAAG < 1.1 mg/d
  • Cirrhosis
  • Alcoholic Hepatitis
  • Cardiac Ascites
  • “Mixed Ascites”
  • Massive Liver Metastasis
  • Fulminant Hepatic Failure
  • Budd-Chiari Syndrome
  • Portal Vein Thrombosis
  • Veno-Occlusive Disease
  • Myxedema
  • Fatty Liver of Pregnancy
  • Peritoneal Carcinomatosis
  • Tuberculous Peritonitis
  • Pancreatic Ascites
  • Bowel Obstruction
  • Biliary Ascites
  • Nephrotic Syndrome
  • Posteroperative Lymphatic Leak
  • Serositis in Connective Tissue Disease

Microscopy and analysis

Red cell count

Interpretation
  • None
  • >100/microlitre
  • >100,000/microlitre
  • Normal
  • Malignancy, TB
  • Intra-abdominal trauma (DPL)

White cell count

Interpretation
  • <300/microlitre
  • >300/microlitre
    • >25% neutrophils
    • >25% lymphocytes
    • Mesothelial cells
  • Gram +ve cocci
  • Gram –ve
  • Normal
  • Abnormal
    • SBP (90%), cirrhosis (50%)
    • TB or Chylous Ascites
    • TB peritonitis
  • Primary peritonitis
  • Secondary peritonitis


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