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Results
You feel the relief of a large drain within hours. Simple fluid tests, such as the white blood cell count that checks for infection, are often back within hours to a day; cultures take a few days. Your doctor will explain whether the fluid is infected, what it suggests about the cause, and whether you need antibiotics or other treatment.
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Ascites is a build-up of fluid in the space inside the belly, between the abdominal wall and the organs. It is most often caused by cirrhosis (advanced liver scarring), but can also result from other conditions such as heart failure, some cancers, infections, or pancreatic disease. In paracentesis, a doctor numbs a small area of the skin and passes a thin needle or a small flexible tube through the belly wall into the fluid, so that some of the fluid can be drawn off. A small sample may be taken for testing (a diagnostic tap), or a larger amount may be drained to relieve symptoms (a therapeutic tap). It is often guided by an ultrasound scan to choose the safest spot.
Why is it done?
It is done for two main reasons. First, to test the fluid: this helps find the cause of the ascites and, importantly, checks for infection of the fluid (spontaneous bacterial peritonitis, SBP), a serious complication of ascites in liver disease that can occur without obvious symptoms. Second, to relieve a swollen, tight or painful belly that causes breathlessness, discomfort, poor appetite or early fullness, especially when medicines and a low-salt diet are not enough (large-volume paracentesis). When a large amount is removed, a medicine called albumin is usually given through a drip to protect the kidneys and circulation.
Who needs it?
- People with new ascites, to find the cause and exclude infection
- People with cirrhosis and ascites who are admitted to hospital, or who have fever, belly pain, confusion, worsening kidney function or other signs of possible infection (the fluid is usually tested in these situations)
- People with large or tense ascites that causes discomfort or breathlessness
- People whose ascites keeps returning despite treatment and need repeated drainage, after which other options may be discussed
Before the procedure
- Your team will explain the procedure and ask for consent. In many cases no fasting is needed, but follow any instructions you are given.
- Tell the team about all your medicines, especially blood thinners and anti-platelet medicines (warfarin, apixaban, rivaroxaban, clopidogrel, aspirin) and about any bleeding problems. Blood tests may be checked, but the procedure is often done even with abnormal clotting tests in liver disease. Do not stop any medicines unless told to.
- Tell the team about allergies (especially to local anaesthetic or antiseptic), previous belly surgery, skin infection over the belly, or pregnancy.
- Empty your bladder just before the procedure, as a full bladder can be closer to the needle.
- You will usually be awake and no sedation is needed. Ask if you should eat or take your medicines as usual. If you are fasting in Ramadan and the procedure is not urgent, discuss timing with your team.
During the procedure
You lie on your back or slightly on your side, with the head raised. The doctor often uses ultrasound to find a safe pocket of fluid, cleans the skin with antiseptic and injects a local anaesthetic, which stings briefly. A thin needle or a soft drainage tube is then passed through the skin; you may feel pressure but should not feel sharp pain. For a test sample, a small amount of fluid (a few syringes) is drawn off, which takes a few minutes. For a large drainage, the tube stays in while the fluid drains into a collection bag or bottle, usually over about 30 minutes to a few hours depending on the amount. Your blood pressure and pulse are checked. Tell the staff if you feel dizzy, faint or have pain. The tube is removed and a small dressing is placed over the site.
After the procedure
You will rest for a short time and be watched. A small dressing covers the puncture site; keep it clean and dry as advised. Some clear or pink-tinged fluid can leak from the site for a day or so; tell the staff if it soaks the dressing. Mild soreness at the site is common. If a large amount was drained you may be monitored for several hours, and you will have albumin by drip. Continue your low-salt diet and your water tablets (diuretics) as your liver team instructs, because the fluid can build up again. Weigh yourself regularly as advised. Avoid heavy lifting and strenuous activity for a short time as advised.
Risks
- Pain or bruising at the needle site, and leakage of fluid from the site for a day or so (common)
- Low blood pressure, dizziness or kidney problems after a large drain, which is why albumin is given and blood pressure is monitored
- Bleeding, usually minor; rarely bleeding inside the belly wall or into the belly, especially in people with bleeding problems
- Infection of the skin or the belly lining (peritonitis), uncommon
- Rarely, injury to the bowel or bladder by the needle, which is why ultrasound guidance is used
- A persistent leak of fluid from the puncture site, more likely in tense ascites; it usually settles but may need a stitch or dressing
- The fluid usually returns unless the underlying cause is treated, so drainage is relief, not a cure.
- Get urgent help if you have fever or chills, increasing belly pain, redness, swelling or pus at the site, ongoing heavy leakage or bleeding, dizziness or fainting, very little urine, new confusion or drowsiness, or vomiting blood or passing black stools.
When you get results
Alternatives if you decline
For mild ascites, a low-salt diet and water tablets (diuretics) are the first treatment, and drainage may not be needed. For ascites that keeps returning, options include repeated paracentesis, a long-term drain in selected cases, a procedure that creates a channel in the liver to reduce pressure (TIPS), and in suitable people, liver transplant assessment. For testing the fluid there is no good alternative, since blood tests cannot reliably show infection of the fluid. Declining a needed diagnostic tap can delay finding a dangerous infection. Your liver specialist will advise.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Why do I need the fluid tested, and what are you looking for?
- How much fluid will be drained, and will I need albumin?
- Should I take my water tablets and blood thinners on the day?
- How can I reduce the chance that the fluid builds up again?
- What symptoms mean I should come to the hospital at once?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide