Indications and Contraindications for Ascitic Tap
Indications for Diagnostic Paracentesis
All patients with new-onset ascites should undergo diagnostic paracentesis to determine the etiology and exclude infection. 1
Mandatory Indications
- New-onset ascites in any patient, regardless of suspected etiology 1, 2
- All cirrhotic patients with ascites requiring hospital admission - this is a surveillance tap to detect unsuspected spontaneous bacterial peritonitis (SBP), which is present in approximately 15% of hospitalized patients 1
- Any clinical deterioration in patients with known ascites, including:
Additional Clinical Scenarios
- Suspected infection even in asymptomatic patients, as SBP can present without symptoms in a significant proportion of cases 1, 4
- Suspected secondary bacterial peritonitis (intestinal perforation) - requires additional testing beyond standard analysis 2
- Suspected malignancy - cytology should be requested when peritoneal carcinomatosis is suspected 1, 2
Contraindications to Paracentesis
There are essentially no absolute contraindications to paracentesis except clinically evident fibrinolysis or disseminated intravascular coagulation, which occur in less than 1 in 1,000 procedures. 1, 6
True Contraindications (Extremely Rare)
- Clinically evident hyperfibrinolysis with three-dimensional ecchymosis or hematoma formation 6
- Clinically evident disseminated intravascular coagulation 1, 6
Common Misconceptions - NOT Contraindications
Coagulopathy should NOT preclude paracentesis. The following are explicitly NOT contraindications: 1, 6
- Prolonged prothrombin time/INR - no data-supported cutoff exists; paracentesis has been safely performed with INR as high as 8.7 1, 6
- Thrombocytopenia - paracentesis is safe even with platelet counts as low as 19,000 cells/mm³ 6
- Abnormal coagulation profile - 71% of patients in safety studies had abnormal prothrombin times without increased complications 1
Prophylactic transfusion of fresh frozen plasma or platelets before paracentesis is NOT recommended unless thrombocytopenia is severe (<40,000/mm³), in which case most clinicians would consider platelet transfusion, though this is not evidence-based 1, 2
Safety Profile
- Complications occur in only ~1% of patients, primarily abdominal wall hematomas 1
- Serious complications (hemorrhage, bowel perforation) occur in less than 1 in 1,000 procedures 1, 6
- Bleeding complications are more common in patients with renal failure rather than coagulopathy 6
- No deaths or infections were reported in recent large series of paracentesis procedures 1
Technical Considerations
Preferred Site
- Left lower quadrant: 2 finger breadths (3 cm) cephalad and 2 finger breadths medial to the anterior superior iliac spine 6
- This site is preferred because the abdominal wall is thinner and a larger fluid pool accumulates here 6
Structures to Avoid
- Inferior and superior epigastric arteries - run just lateral to the umbilicus toward the mid-inguinal point 1, 6
- Visible collateral vessels on the abdominal wall 6
- Enlarged liver or spleen 1
When Ultrasound Guidance May Help
- Obesity 6
- Pregnancy 6
- Severe intestinal distension 6
- History of extensive abdominal surgery 6
- Minimal ascites (at least 1,500 mL must be present for successful blind paracentesis) 6, 7
Essential Ascitic Fluid Analysis
Initial paracentesis should include: 2
- Cell count with differential (polymorphonuclear neutrophil count) - PMN ≥250 cells/mm³ is diagnostic of SBP 1, 2, 7
- Ascitic fluid albumin to calculate serum-ascites albumin gradient (SAAG ≥1.1 g/dL indicates portal hypertension with 97% accuracy) 2, 7
- Total protein concentration 2
- Blood culture bottles inoculated at bedside - improves culture yield 1, 2, 3
For repeated therapeutic paracenteses in asymptomatic patients, analysis may be limited to cell count with differential, and blood culture is not necessary 2