Peritoneal Fluid Analysis

Normal peritoneal fluid is a small volume of clear, straw‑colored serous fluid (a few to several tens of milliliters) that lubricates abdominal organs and permits frictionless movement. It is low in protein and cellularity, containing mainly mesothelial cells and few leukocytes, and is sterile. Significant increases in volume or turbidity suggest pathology (inflammation, infection, bleeding, or malignancy).

Peritoneal fluid is tested to diagnose infection (peritonitis), identify cancer cells, and determine the cause of ascites. Analysis includes cell counts and cultures, cytology, and biochemical tests (protein, albumin, LDH, glucose, amylase, bilirubin) to distinguish transudate versus exudate, detect hemorrhage or chylous effusion, and guide treatment decisions such as antibiotics, drainage, or further imaging.

Peritoneal fluid is the normal small amount of lubricating fluid within the abdominal cavity. Ascites is an abnormal, often large accumulation of peritoneal fluid caused by conditions like liver cirrhosis, heart failure, infection, or cancer. Ascitic fluid can be transudative or exudative, produces abdominal distension and symptoms, and usually requires diagnostic evaluation (paracentesis, labs) and treatment.

Peritoneal (ascitic) fluid commonly contains mesothelial cells and macrophages. Inflammatory or pathologic states show increased neutrophils (bacterial peritonitis), lymphocytes (tuberculous or malignant causes), eosinophils (allergic/parasitic reactions), and occasional red blood cells with hemorrhage. Detection of malignant cells indicates cancer involvement. Gram stain or culture can identify organisms; cytology evaluates cell morphology for malignancy.

Treating peritoneal fluid (ascites) focuses on addressing the cause, sodium restriction and diuretics (spironolactone ± furosemide). Large or tense ascites may need therapeutic paracentesis, often with albumin replacement if >5 liters removed. Infected fluid (spontaneous bacterial peritonitis) requires prompt IV antibiotics. Refractory cases may need TIPSS or transplant evaluation. Seek urgent care for fever, severe pain, or worsening breathlessness.

Signs of infected peritoneal fluid include cloudy or foul-smelling drainage, abdominal pain/tenderness, fever, nausea, vomiting, chills, or low blood pressure. Diagnosis uses fluid testing: peritoneal dialysis effluent often shows WBC >100 cells/µL with >50% neutrophils; ascitic fluid infection is suggested by PMNs ≥250 cells/mm3 or positive culture/Gram stain. Seek urgent medical care if suspected.