Interpreting sample results in ascites

There is no ‘standardized’ fluid cell count
The generally accepted ‘cut-off’ for the upper-limit of normal is <250 neutrophils/mm3. Neutrophils usually constitute 70% of the cell count.
In spontaneous bacterial peritonitis, neutrophils are the predominant line. In TB ascites, lymphocytes predominate.
Bloody ascites is usually the result of the procedure itself, i.e. a traumatic tap. (Remember the anatomical position of the superficial epigastric arteries).

Patients with an ascitic total protein gradient of <15g/L have an increased risk of developing spontaneous bacterial peritonitis and may benefit from antibiotic prophylaxis.
Traditionally the serum: ascites LDH and protein ratios help differentiate exudates from transudates. However, the literature shows that these calculations are actually not helpful.
The Serum Ascites Albumin Gradient (SAAG), a concept involving oncotic-hydrostatic balance, has become the preferred measurement to characterize ascites.

SAAG > 1.1 mg/dl (Portal Hypertension)	SAAG < 1.1 mg/d
“Mixed Ascites” Cardiac Ascites Alcoholic Hepatitis Cirrhosis Massive Liver Metastasis Fulminant Hepatic Failure Budd-Chiari Syndrome Portal Vein Thrombosis Veno-Occlusive Disease Myxoedema Fatty Liver of Pregnancy	Peritoneal Carcinomatosis Tuberculous Peritonitis Pancreatic Ascites Bowel Obstruction Biliary Ascites Nephrotic Syndrome Posteroperative Lymphatic Leak Serositis in Connective Tissue Disease

You would expect the ascitic amylase to be about half the serum amylase
If the ascites is secondary to pancreatitis or perforated viscus, the ascitic amylase can be as great as five-fold higher than serum amylase

In uncomplicated ascites this should be similar to serum levels.
In advanced (but often not in early) Spontaneous Bacterial Peritonitis, glucose levels in ascites can drop to as low as 0 mg/dl as a result of bacterial consumption

Cultures should be obtained by inoculating blood culture bottles at the bedside. This has been shown to improve sensitivity to at least 80%, compared with 50% for ‘conventional’ culture methods.
Gram stains are relatively 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.

Truly only helpful in diagnosing peritoneal carcinomatosis with reported sensitivities of ≤100%.
Does not detect most other intra-abdominal cancers, mainly because most do not frequently metastasize to the peritoneum.
Think of cytology as helping you only if you’re suspicious of a cancer that has spread to the peritoneum. And remember that a negative cytology does not rule out cancers such as hepatocellular carcinoma or liver metastases, which commonly cause ‘malignant ascites.’

Examinations