Ascitic Fluid study

Gram Stain:

  • – Gram stain is positive when > 10,000 bacteria/ml present
  • – Bacteria are detected on Gm stain only with overwhelming infection
  •               • Advanced SBP
  •               • Asplenic pneumococcal sepsis
  • – Gm staining of ascetic fluid is most helpful in the diagnosis of free perforation of the intestine into ascetic fluid

 

Smear and Culture for TB

 

  • – A direct smear of ascitic fluid to detect mycobacteria is almost never positive because of the low concentration of mycobacteria in ascitic fluid in TB peritonitis
  • – Negative bacterial culture and predominance of mononuclear cells in the differential count provide clues to the diagnosis of TB peritonitis
  • – Laparoscopy with histology and culture of peritoneal biopsies has a sensitivity approaching 100% for detecting TB peritonitis

 

 

Cytologic examination

  • – Cytologic studies can be expected to detect malignancy only when tumor cells line the peritoneal cavity and exfoliate into the ascetic fluid ( i.e. peritoneal carcinomatosis)
  • – Cytologic studies cannot detect tumor when peritoneum is uninvolved as in
  •                  • Ascites resulting from portal HTN
  •                  • Massive Liver Metastasis
  •                  • Lymph node obstruction from malignancy/lymphoma
  • – In malignancy-related ascites, the fluid may have an elevated PMN count because dying tumor cells attract Neutrophils, the elevated PMN may cause confusion with SBP. But the prediomonance of lymphocytes in malignancy related ascites is ususal

 

Glucose

  • – The glucose molecule is small enough to diffuse readily into body fluid cavities. Therefore, the concentration of glucose in ascitic fluid is similar to that in serum, unless glucose is being consumed by ascitic fluid WBCs or bacteria
  • – In early SBP- the ascetic fluid glucose concentration is similar to that of sterile fluid
  • – In SBP detected late in its course: the ascetic fluid glucose concentration usually drops to 0 mg/dl because of large number of stimulated neutrophil and bacteria

 

 

Total Protein

  • – The ascetic fluid protein concentration is determined almost entirely by theserum protein protein concentration and portal pressure
  • – Ascetic fluid protein concentration does not does increase during SBP. It remains stable before, during and after infection
  • – Patients with the lowest ascetic fluid concentration are the most susceptible to SBP
  • – Surgical (secondary) peritonitis is present if 2 of the following 3 criteria is present
  •                       • Total protein > 1 g/dL (10 g/L)
  •                       • Glucose < 50 mg/dL (2.8 mmol/L),
  •                       • LDH > ULN for serum

 

Amylase

  • – In acute pancreatitis or intestinal perforation (with release of luminal amylase into the ascitic fluid), the fluid amylase is usually > 2000 U/L, and approximately 5-fold greater than simultaneous serum values.

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