Clinical Procedures - Ascitic Fluid Sampling (Tap) Indications • Diagnosing nature of new onset ascites (i.e. exudate or transudate) • Diagnosis of spontaneous bacterial peritonitis • Cytology to diagnose malignant : ascites. Contraindications • Acute abdomen that requires surgery • Pregnancy • Intestinal obstruction • Grossly distended urinary bladder • Superficial infection (cellulitis) at the potential puncture site • Hernia at the potential puncture site. Risks • Persistent leak of ascitic fluid: • This is more likely if there is a large amount of fluid under tension • Perforation of hollow viscera (e.g. bowel and bladder). This is very rare • Peritonitis • Abdominal wall hematoma • Bleeding is very rare but may occur if there is injury to inferior epigastric artery (be careful to tap lateral abdominal wall as described). Procedure Tips • Check the patient's clotting and platelet count before the procedure and proceed with caution and senior advice if abnormal (correct if platelets <20 x 10°L, INR ≥2.5) • Inform the laboratory especially during out of hours if cultures needed urgently and if SBP is suspected • D If unable to obtain fluid despite correct technique, do not persist! Stop and seek senior advice. SAAG Calculating the serum-ascites albumin gradient (SAAG) is a method of determining the cause of ascites. SAAG = [serum albumin] - [ascites albumin] >11g/L = portal hypertension (cirrhosis, alcoholic hepatitis, cardiac ascites, Budd-Chiari syndrome, massive liver metastases). <11g/L = infection, malignancy, nephrotic syndrome, pancreatic ascites. Equipment • Sterile gloves • Dressing pack • Antiseptic solution (e.g. iodine) • 1% or 2% lidocaine • 1 × 20mL syringe • 2 × 5mL syringes • 21G (green) and 25G (orange) needles • Sterile containers • Culture bottles • Sterile dressing. Procedure • Introduce yourself, confirm the patient's identity, explain the procedure, and obtain informed consent • Examine the abdomen and select a site for aspiration, 3 finger-breadths cranial to the anterior superior iliac spine: • D Beware of positioning too medial as this risks hitting the inferior epigastric vessels • D Be sure to identify and avoid any organomegaly which might interfere with procedure (in patients with massive splenomegaly, for example, avoid left iliac fossa) • Clean the area with disinfectant and apply sterile drape • Using the 25G (orange) needle and the 5mL syringe, administer local anaesthetic to the skin and subcutis, raising a wheal • Using the 21G (green) needle, infiltrate deeper tissues, intermittently applying suction until the peritoneal cavity is reached, confirmed by flow of ascitic fluid into the syringe • Note the depth needed to enter the peritoneal cavity • Discard the used needles and attach a clean 21G needle to the 20mL syringe • With the green needle perpendicular to the skin, insert carefully, aspirating continuously until you feel resistance give way • Aspirate as much fluid as needed (usually 20mL is plenty) • Withdraw needle and syringe and apply dressing •Send sample for Gram stain and culture (in blood culture bottles), white cell count/neutrophils, biochemistry, cytology (if malignancy suspected): • White cell count can be calculated in haematology lab; send fluid in EDTA-containing bottle. » (Total white cell count >500/mm' or neutrophils >250/mm3 suggests spontaneous bacterial peritonitis, SP) • Neutrophil count is usually a manual procedure via microbiology and may take longer • If malignancy is suspected, a large volume of ascites (e.g. 500mL) should be sent to cytology. Documentation • Date, time, indication, informed consent obtained • Type and amount of local anaesthetic used • Site aspirated • Aseptic technique used? • How many passes? • Volume and colour of aspirate obtained • Tests requested on samples • Any immediate complications • Signature, printed name, and contact details.
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