Diagnostic abdominal paracentesis (ascitic tap) [advanced]

Before you start

Indications: diagnosis of cause of new ascites; diagnose spontaneous bacterial peritonitis or other infections (e.g. abdominal TB); diagnose blood in peritoneal space in trauma

Relative contraindications: severe coagulopathy (disseminated intravascular coagulation or accelerated fibrinolysis); pregnancy; distended bowel (obstruction/ileus); organomegaly; distended bladder


  • Wash hands, Introduce self, Patients name & DOB & wrist band, Explain procedure and get written consent
    • Risks: pain; bleeding; infection; damage to local structures (including bowel perforation); paracentesis leak
    • Ask patient to empty their bladder prior to procedure
  • **Check patients clotting screen, platelet count and if they have been on an therapeutic anticoagulant/clopidogrel**
  • Ensure assistant is available
  • Examine patient and tap out ascites
  • Use ultrasound to confirm the presence/location of ascites, check the depth of the abdominal wall and mark the spot pre-procedure (although, if there is tense ascites with fluid thrill, it is usually safe to proceed without ultrasound)

Preparation part

  • Wash hands and apply apron
  • Clean a trolley
  • Gather equipment onto bottom of trolley (think through what you need in order)

Equipment list

  • Sterile pack
  • Cleansing snap-sponge x2 (iodine or alcohol/chlorhexidine)
  • OPTIONAL: Sterile drape with hole in centre (or 2-3 drapes without holes in)
  • 10ml syringe and 3 needles (1 blunt fill 18G drawing-up needle, 1 orange 25G, 1 green 21G) for local anaesthetic
  • 20ml syringe and green 21G needle for aspirating ascitic fluid
  • Cotton gauze swabs (used whenever needed throughout procedure to dry/clean sterile area)
  • Sterile dressing
  • Equipment to be kept outside of the sterile field
    • Sterile gloves
    • 10ml 1% lidocaine (maximum 3mg/kg – note 1ml 1% lidocaine = 10mg)
    • Bottles: 1-3 white-topped sample collection bottles, purple EDTA haematology tube, yellow SST biochemistry tube, blood culture bottles

  • Walk to patient
  • Wash hands
  • Open sterile pack to form a sterile field on the top of the trolley
  • Open packets (without touching the instruments themselves) and drop sterile instruments neatly into the sterile field
  • Pick up waste bag from sterile pack without touching anything else and stick to side of trolley

Patient part

Positioning and exposure

  • Position patient lying supine in bed with head of bed elevated (aids fluid accumulation in lower abdomen)
  • Expose patient’s abdomen

If the insertion point has not already been marked using ultrasound…

  • Locate insertion point:
    • Traditionally in the right iliac fossa (approximately 5cm above and up to 5cm medial to the right ASIS)
    • Tap out ascites and confirm flank dullness at intended insertion point
  • Use different site if there is overlying infection
  • Mark insertion point with a skin pen/indentation


  • Wash hands
  • Apply sterile gloves using sterile technique (open pack on a side surface)
  • Sterilize area
    • Work from middle outwards in one spiral motion (using cleansing snap-sponge)
    • Repeat with second cleansing snap-sponge
    • Discard used snap-sponges as they are no longer sterile, but note all equipment used after this (including all needles) can be returned to the sterile field after use
    • OPTIONAL: Apply the sterile drape over the patient’s body so that the hole is in the correct place to allow access to the insertion site (or apply 2-3 drapes centred around exposed insertion site if no holes)
  • Anaesthetise tract
    • Ask assistant to snap open lidocaine bottle and hold open upside-down
    • Draw up lidocaine using drawing-up needle on 10 ml syringe and expel any air
    • Change to the orange needle and insert at an acute angle to form a single subcutaneous bleb around insertion site in order to anaesthetise the skin
    • Change to the green needle and insert perpendicular to the skin to anaesthetise the insertion tract
      • This is done by instilling lidocaine in small increments of increasing depth
      • Always aspirate when advancing the needle (so you know when you get to the peritoneal cavity) and aspirate before injecting lidocaine (to check you are not in a vessel)
      • When fluid is aspirated, remove needle and do not advance further
    • Wait 1 minute to work


  • Attach new green needle to the 20ml syringe
  • Insert perpendicular to the skin into the same tract, aspirating during infiltration
  • When fluid is aspirated, stop advancing and remove 20ml of ascitic fluid
  • Remove needle


  • Dress wound

To complete

  • Thank patient and cover them
  • Bin waste and gloves, dispose of sharps safely, clean trolley and wash hands
  • Decant ascitic fluid into sample tubes, label them and send to lab
    • MC&S (blood culture bottles or white-top) → microbiology
    • Albumin (white-top or yellow SST tube) → biochemistry
    • Cytology if first ascitic sample (white-top) → histopathology
    • Cell count (purple EDTA top) → haematology
    • Other tests to consider: protein, glucose (paired)
  • Perform venepuncture to determine concurrent albumin level
  • Fully document procedure in patients notes

Learn how to interpret the results too…

Ascitic fluid result interpretation is covered here!

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