Ascitic aspiration (tap) is routinely performed for every patient admitted with ascites to identify the underlying cause. The most urgent reason to do it would be to consider the diagnosis of spontaneous bacterial peritonitis (SBP). Occasionally a patient may have a therapeutic aspiration where a larger volume is aspirated to relieve pressure if a drain is deemed inappropriate but usually ascitic paracentesis is used (a drain).
- Absolute contraindications include patient refusal or local infection
- Relative contraindications include abnormal clotting (INR >1.5)
Often the gastroenterology team perform diagnostic aspirations irrespective of the INR. Despite cirrhotic patients often being thrombocytopenic or coagulopathic, their bleeding risk in minor procedures is usually low and FFP and/or platelets is not required.
Often verbal consent is sufficient as complications are very rare. These include:
- Failure to obtain a sample
- Infection (skin/peritonitis)
- Fluid leaking from the wound
- Perforation of viscus (e.g. bladder or bowel)
An ascitic drain is a very safe procedure overall but definitely requires close supervision. When draining ascites, a relatively common complication is hypotension secondary to fluid shifts. Thus, 100ml of 20% human albumin is sometimes given for every 2L of ascites drained. This isn’t usually required in malignant ascites.Top Tips
- Avoid being close to a surgical scare to avoid adhesions
- Ultrasound will help you find a large pocket of fluid & assist you in the depth. Consider a longer needle in obesity
- Position the patient angled slightly towards you. The bowel will float away if you do this.
- If suspecting malignancy, send as large a volume as you can for cytology
- Avoid any superficial vasculature you can see
- You will likely require some pressure to pierce the peritoneum, but hold the needle close to the skin to prevent you from accidentally going in too deep
- Ultrasound machine
- Sterile trolley
- Sterile field and sterile gloves
- Chlorhexidine cleaning wand
- 1% Lidocaine*
- Orange, and 2 green needles
- 10ml syringe for lidocaine
- 20ml syringe (50ml ideally if sending cytology)
*I tend to offer lidocaine in an ascitic tap but many patients decline as they do not want two needles.
- Explain procedure and obtain consent – complications to explain include infection, bleeding, pain, failure of procedure, damage to surround structure and leakage.
- Ensure patient has emptied bladder (urine & ascitic fluid look very similar)
- Position the patient supine, angled slightly towards you, with the abdomen exposed
- Identify the area of maximum fluid – ideally using USS but can percuss the fluid level to confirm presence of ascites
- Mark insertion site with skin marking pen
- Left lower quadrant may be safest as less chance of nicking liver
- Aim for 2 fingers breadth above and medial to the ASIS
- Prepare the sterile field and clean skin using chlorhexidine spray and allow to dry
- Don sterile gloves and apply drape with the opening over the marked site
- Stretch skin taught by pulling skin 2cm down (this creates a Z track – a non-linear path from ascitic fluid to puncture site minimising leak) and inject local anaesthetic – 1% in a 5ml syringe – inject a small bleb cutaneously using orange needle, subcutaneously then inject through the whole insertion tract using green needle into peritoneum
- Advance the needle in 5mm increments, draw back and if no blood aspirated inject a small amount of anaesthetic, keep going until you reach ascitic fluid – this confirms its presence and the depth of penetration needed to reach the ascites.
- At this point either follow instructions for your local ascitic drain pack or proceed to an ascitic tap using Z tracking technique – Insert a 21 gauge needle on a 20 or 50ml and advance while aspirating until fluid is withdrawn. Aspirate fluid required.
- Remove the needle and apply sterile dressing – send fluid for MC&S, Biochemistry and cytology.
- Lie the patient on the side with the puncture wound up to minimise fluid leakage.
If inserting an ascitic drain for a patient with cirrhosis, remember that the catheter is usually removed after 6L of fluid or by 6 hours (whichever comes sooner).
Interpretation of Ascitic fluid
|Ascitic fluid appearance|
|Clear/Straw coloured||Liver cirrhosis|
|Chylous – Milky||Lymphoma|
|Protein||See Serum to Ascites Albumin Gradient (SAAG) below|
|Glucose||If low compared to paired serum glucose suggests infection or malignancy|
|Amylase||If raised – pancreatitis|
|WCC||>250/dL and predominantly neutrophils = SBP|
>250/dL and predominantly lymphocytes consider TB
|Gram Stain and Culture|
|Polymicrobial||Secondary bacterial peritonitis – search for a perforated viscus|
Serum to Ascites albumin gradient
High SAAG >1.1g/dL (not much albumin in ascitic fluid) suggests the presence of portal hypertension – since the liver sinusoids are designed to keep albumin in the blood and diseased liver sinusoids which are fibrotic are even less likely to keep allow albumin to escape the blood into hepatic lymph
Causes include: Cirrhosis, Venous occlusion e.g. Budd Chiari syndrome and CCFLow SAAG <1.1g/dL (ascitic albumin close to plasma albumin) – this is typically caused by inflamed or tumour laden peritoneum leaking albumin into the peritoneal cavity > osmotic accumulation of ascites.
Causes include: Peritoneal carcinomas, TB peritonitis, pancreatitis or nephrotic syndrome
Spontaneous Bacterial Peritonitis
- Always consider SBP in patients with cirrhosis who suddenly decompensate
- Most commonly seen in patients with end-stage liver disease
- Common organisms are E.Coli, Klebsiella and Strep.
- Key symptoms are abdominal pain, fever, vomiting, altered mental status and GI bleeding however patients are often minimally symptomatic.
- Defined are ascitic fluid absolute neutrophil count >250 cells/mm3 regardless of if there is culture growth.
Treatment with empirical broad-spectrum antibiotics are key to management – third-generation cephalosporins e.g. cefotaxime is usual however use the trust microbiology guidelines to take into account local resistance patterns. Usually, human albumin solution is additionally given on Day 1 (1.5g/kg) & Day 3 (1g/kg). Addition of metronidazole may be appropriate if there has been recent instrumentation to ascites. Antibiotic prophylaxis may be considered in patients who are high risk.
Written by Dr Emma-Jane Monteith (FY1)
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