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# Diagnostic and large-volume paracentesis

- Procedure

A needle is placed through the belly wall to take out fluid that has collected in the abdomen, to test it or to relieve pressure.

Updated Nov 13, 2026

## Key points

- Tap every admitted patient with cirrhotic ascites, and any with fever, pain, encephalopathy, kidney injury or bleeding.
- Left lower quadrant, lateral to the rectus sheath: avoids the inferior epigastric vessels.
- Z-track technique reduces persistent leakage of fluid after the needle is removed.
- Inoculate blood culture bottles at the bedside: it raises the yield for spontaneous bacterial peritonitis.
- Large-volume drainage: albumin by protocol to prevent post-paracentesis circulatory dysfunction.

On this page

- The basics Key points
- What it is
- Indications
- Equipment
- Step by step (and why)
- Next step
- Elsewhere in DurgiPedia

- Clinical Complications

- Safety Contraindications and precautions

- Study Test yourself

- Connections Connections

## What it is

Paracentesis removes ascitic fluid from the peritoneal cavity. A diagnostic tap takes a sample to find the cause of ascites and to rule out infection; a large-volume (therapeutic) paracentesis drains the abdomen to relieve tense or refractory ascites. Every patient with cirrhosis and ascites who is admitted to hospital, and any patient with ascites who has fever, abdominal pain, encephalopathy, worsening kidney function or bleeding, should have a diagnostic tap, because spontaneous bacterial peritonitis is common and often silent. The usual site is the left lower quadrant, lateral to the rectus sheath and medial and above the anterior superior iliac spine, which avoids the inferior epigastric vessels and the caecum; the midline below the umbilicus is an alternative. Ultrasound confirms a deep pocket of fluid and shows bowel and vessels. A Z-track insertion (skin pulled to one side before the needle enters) leaves an offset track that closes when released and reduces leakage. Abnormal clotting tests in cirrhosis are not, on their own, a reason to avoid or delay the procedure. After a large-volume drainage, albumin is given according to protocol to prevent circulatory dysfunction and kidney injury.

## Indications

- New-onset ascites: diagnostic tap to find the cause (portal hypertension or not).
- Cirrhosis with ascites on admission, or with fever, abdominal pain, encephalopathy, kidney injury or bleeding.
- Suspected secondary peritonitis, malignant or tuberculous ascites.
- Tense ascites causing breathlessness, pain or early satiety: large-volume drainage.
- Refractory ascites not controlled by diuretics and sodium restriction: repeated drainage.

## Contraindications and precautions

- Clinically evident fibrinolysis or disseminated intravascular coagulation; abnormal INR in cirrhosis alone is not a bar.
- Distended bowel, bowel obstruction or adhesions under the site: use ultrasound or another site.
- Full bladder: empty it first, or use ultrasound.
- Surgical scars, visible collateral veins, skin infection or abdominal wall haematoma at the site.
- Pregnancy and small, loculated collections: ultrasound guidance and senior help.

## Equipment

- Ultrasound machine, or at least a marked site.
- Sterile gloves, drape, antiseptic, gauze and an occlusive dressing.
- Local anaesthetic with needles and syringes.
- Needle (for example 18 to 22 G) for diagnosis; catheter-over-needle or paracentesis catheter, tubing and drainage bag for large volumes.
- Sterile tubes, blood culture bottles, labels and request forms; albumin per protocol for large-volume drainage.

## Step by step (and why)

- Check the indication, the bladder and imaging; explain and consent — this prevents puncturing a full bladder or bowel.
- Lie the patient supine, slightly tilted to the side of the tap — fluid pools in the flank and bowel floats away.
- Scan and mark a deep pocket in the left lower quadrant, lateral to the rectus — this avoids the epigastric vessels.
- Clean widely and drape; infiltrate local anaesthetic down to the peritoneum — the parietal peritoneum is sensitive.
- Pull the skin aside, then insert the needle while aspirating — the Z-track closes when the skin is released.
- Stop advancing when fluid flows freely — going deeper risks bowel; note the colour (clear, cloudy, bloody, milky).
- Fill the blood culture bottles first at the bedside, then the tubes — bedside inoculation raises the culture yield.
- For large volumes, connect the drain and watch blood pressure — rapid fluid shifts can cause hypotension.
- Remove the needle, apply pressure and an occlusive dressing, and record volume and appearance.

## Complications

- Persistent leakage of ascitic fluid from the puncture site, more common without a Z-track.
- Abdominal wall haematoma or, rarely, haemoperitoneum from an injured inferior epigastric or collateral vessel.
- Bowel perforation and infection, uncommon with ultrasound guidance.
- Post-paracentesis circulatory dysfunction after large volumes: hypotension, hyponatraemia, kidney injury.
- Hepatorenal syndrome and encephalopathy precipitated by large fluid shifts.

## Next step

- Send cell count with differential, albumin with same-day serum albumin, total protein, Gram stain and culture; then work out the SAAG.
- Add cytology, glucose, LDH, amylase or adenosine deaminase when malignancy, secondary peritonitis or tuberculosis is suspected.
- A high neutrophil count in the fluid means spontaneous bacterial peritonitis: start antibiotics and albumin per protocol.
- After large-volume drainage, monitor blood pressure, sodium and creatinine; continue diuretics and sodium restriction as planned.
- Refractory ascites or a first episode of peritonitis: refer to hepatology (prophylaxis, TIPS, transplant assessment).

## Test yourself

Think of the answer, then tap the question to see it.

## Why is the left lower quadrant, lateral to the rectus sheath, the preferred site for paracentesis?

It avoids the inferior epigastric vessels, which run within or just behind the rectus, and the caecum, while the fluid pocket there is usually deep.

## What is the Z-track technique and why is it used?

The skin is pulled to one side before the needle enters, so the skin and deeper holes are offset when released; this reduces leakage of ascitic fluid.

## Which patients with cirrhosis and ascites need a diagnostic paracentesis?

Every patient admitted to hospital, and anyone with fever, abdominal pain, encephalopathy, worsening kidney function or gastrointestinal bleeding, to detect spontaneous bacterial peritonitis.

## Why is albumin given after a large-volume paracentesis?

To prevent post-paracentesis circulatory dysfunction, the fall in effective blood volume that can cause hypotension, hyponatraemia and kidney injury.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/clinical-skills/diagnostic-and-large-volume-paracentesis/)

## Elsewhere in DurgiPedia

- [Ascites: shifting dullness and fluid wave](https://durgical.com/en/clinical-exam/ascites-shifting-dullness-and-fluid-wave/)
- [Portal hypertension and the signs of chronic liver disease](https://durgical.com/en/clinical-exam/portal-hypertension-and-the-signs-of-chronic-liver-disease/)
- [Portal hypertension](https://durgical.com/en/general-pathology/portal-hypertension/)

## Connections

## Related 4

- [Ascitic fluid: SAAG and infection](https://durgical.com/en/clinical-skills/ascitic-fluid-saag-and-infection/)
- [Infiltrating local anaesthetic and digital blocks](https://durgical.com/en/clinical-skills/infiltrating-local-anaesthetic-and-digital-blocks/)
- [Ultrasound-guided vascular access](https://durgical.com/en/clinical-skills/ultrasound-guided-vascular-access/)
- [Liver tests: hepatocellular or cholestatic?](https://durgical.com/en/clinical-skills/liver-tests-hepatocellular-or-cholestatic/)

## Related conditions 5

- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)
- [Ascites and spontaneous bacterial peritonitis](https://durgical.com/en/conditions/ascites-and-spontaneous-bacterial-peritonitis/)
- [Portal hypertension](https://durgical.com/en/conditions/portal-hypertension/)
- [Hepatorenal syndrome](https://durgical.com/en/conditions/hepatorenal-syndrome/)
- [Hepatic encephalopathy](https://durgical.com/en/conditions/hepatic-encephalopathy/)

## In Pharmacology 4

- [Local anesthetics](https://durgical.com/en/pharmacology/classes/local-anesthetics/)
- [Lidocaine](https://durgical.com/en/pharmacology/lidocaine/)
- [Human albumin](https://durgical.com/en/pharmacology/human-albumin/)
- [Cefotaxime](https://durgical.com/en/pharmacology/cefotaxime/)

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Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: [Paracentesis](https://www.ncbi.nlm.nih.gov/books/NBK435998/) (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/clinical-skills/diagnostic-and-large-volume-paracentesis/