Biopsy and Drainage · IR Playbook

Image-Guided Paracentesis (-)

Image-guided paracentesis is percutaneous aspiration of ascitic fluid under ultrasound localization or real-time guidance for diagnosis, symptom relief or both. Ultrasound is used to confirm drainable fluid, select a bowel-free route and avoid abdominal-wall vessels. It is a low-bleeding-risk procedure; the principal preventable hazards are vascular injury, bowel injury and persistent leakage.

Learning objectives

Select a safe ultrasound-guided route that avoids bowel, bladder, scars and abdominal-wall vessels
Perform diagnostic aspiration or large-volume drainage using an appropriate needle or catheter
Handle ascitic fluid correctly for cell count, chemistry, culture and selective tests
Prevent and recognize bleeding, organ injury, leakage and post-paracentesis circulatory dysfunction

Indications

New-onset ascites requiring etiologic evaluation
Known cirrhotic ascites with hospital admission or clinical deterioration, including fever, abdominal pain, gastrointestinal bleeding, encephalopathy, hypotension or worsening renal or hepatic function
Suspected spontaneous bacterial peritonitis
Tense or refractory ascites causing pain, early satiety, impaired mobility or respiratory compromise
Ascites requiring targeted testing for malignancy, tuberculosis, pancreatic disease, chylous ascites or secondary peritonitis
Recurrent malignant or end-stage-disease ascites requiring palliative symptom relief

Relative contraindications

No safe sonographic access route because of small or loculated fluid, interposed bowel, organomegaly, adhesions or a distended bladder
Cellulitis, wound, stoma, tumor deposit or mesh infection at the proposed site
Marked bowel distension, ileus or suspected surgical abdomen
Inability to cooperate or remain in the scanned position
Active DIC, hyperfibrinolysis or uncontrolled systemic bleeding
Pregnancy or a large pelvic mass requiring modified route planning

Equipment

Ultrasound unit with 2–5 MHz curvilinear transducer for survey and high-frequency linear transducer with color Doppler for the abdominal wall
Sterile probe cover, sterile gel, skin antiseptic, fenestrated drape, sterile gloves and gauze
1% lidocaine, 5–10 mL syringe and 25 G and 22 G needles for local anesthesia
18–22 G needle with 20–50 mL syringe for diagnostic aspiration
Dedicated 5–8 Fr catheter-over-needle paracentesis set for therapeutic drainage
No. 11 blade for a small skin nick when required
Three-way stopcock, drainage tubing and graduated collection bag or vacuum bottles
EDTA tube, sterile specimen containers and aerobic and anaerobic blood-culture bottles
Pressure dressing or sterile occlusive dressing

Procedure steps

Confirm patient, indication, requested tests and consent. Record baseline observations, empty the bladder and establish intravenous access when large-volume drainage or clinical instability makes it prudent.Pearl: Prepare culture bottles and specimen labels before puncture.
Place the patient supine or mildly head-up and rotate slightly if needed to pool fluid laterally. Use a position the patient can maintain throughout scanning and puncture.
Survey the abdomen, identify the largest accessible pocket and measure wall thickness and fluid depth. Confirm a bowel-free route in two planes and use color Doppler to exclude abdominal-wall vessels.Pearl: The safest sonographic pocket is more important than a traditional landmark.
Perform sterile skin preparation and draping. Infiltrate 1% lidocaine from skin through the abdominal wall to the parietal peritoneum while aspirating before injection.Pearl: The parietal peritoneum is pain-sensitive and requires adequate anesthesia.
Use an oblique or Z-track path and advance the needle under real-time ultrasound when the pocket is small or difficult. Maintain visualization of the needle tip and aspirate gently until free ascitic fluid returns.
For therapeutic drainage, advance only the soft catheter into the peritoneal cavity once fluid return is established, then remove the needle or stylet. Connect the catheter to a stopcock and drainage tubing.Pearl: Ensure sufficient catheter length lies freely within the fluid before applying suction.
Send cell count with differential, albumin and total protein for routine diagnostic evaluation, with simultaneous serum albumin when calculating SAAG. When infection is suspected, inoculate ascitic fluid directly into aerobic and anaerobic blood-culture bottles at the bedside; add cytology, amylase, triglyceride, glucose, LDH, mycobacterial studies or other tests only when clinically indicated.Pearl: Do not delay cell count or bedside culture inoculation while completing therapeutic drainage.
Drain by gravity or controlled vacuum while monitoring pain, pulse and blood pressure. Stop for severe pain, hypotension, bloody output, loss of free flow despite repositioning or suspected organ injury; record the total volume and appearance.Pearl: In cirrhosis, give 6–8 g albumin per liter removed when >5 L is drained.
Remove the catheter at the end of drainage, apply firm pressure and place an occlusive dressing. Reassess the puncture site and vital signs, document ultrasound guidance, site, device, specimens, volume, fluid appearance, albumin dose and any complication.Pearl: An oblique track and prompt pressure reduce persistent leakage.

Complications

Pain or vasovagal reaction
Persistent ascitic fluid leak
Abdominal-wall hematoma or hemoperitoneum
Bowel or bladder injury
Procedure-related infection
Post-paracentesis circulatory dysfunction

Exam pearls

Always map the planned tract with color Doppler; avoiding the inferior epigastric and collateral vessels is a key safety step.
The safest ultrasound-defined pocket takes priority over the classic blind landmark.
Cirrhosis-associated coagulopathy is rebalanced: INR and platelet count alone poorly predict bleeding after paracentesis.
Bedside inoculation into blood-culture bottles improves microbiological yield when SBP is suspected.
SAAG identifies portal hypertension; PMN count identifies SBP. They answer different questions.
Albumin after large-volume paracentesis is disease-specific: the standard >5 L and 6–8 g/L rule applies to cirrhosis, not automatically to malignant ascites.

Viva questions

Why is ultrasound guidance preferred for paracentesis?: It confirms that drainable fluid is present, identifies the largest safe pocket, avoids bowel and abdominal-wall vessels and improves procedural success while reducing serious complications.
What is the preferred puncture site?: There is no universally fixed site. Choose the largest safe pocket on immediate ultrasound, commonly in a lateral lower quadrant lateral to the rectus, after excluding bowel and vessels in two planes with color Doppler.
Should an elevated INR in cirrhosis be corrected before paracentesis?: Not routinely. Paracentesis is low bleeding risk, and cirrhosis-related INR elevation does not reliably predict bleeding; evaluate active bleeding, DIC, hyperfibrinolysis, severe thrombocytopenia and supratherapeutic anticoagulation instead.
When is albumin given after paracentesis?: In cirrhosis, give albumin when **more than 5 L** is removed, typically **6–8 g per liter removed**. Routine albumin replacement is not established for uncomplicated malignant ascites.
Which ascitic fluid tests are routine in new-onset ascites?: Send cell count with differential, ascitic albumin and total protein, with same-episode serum albumin for SAAG. Inoculate fluid into aerobic and anaerobic blood-culture bottles at the bedside when infection is suspected; order cytology, amylase, triglyceride or mycobacterial studies selectively.
What ascitic neutrophil count diagnoses spontaneous bacterial peritonitis?: An ascitic PMN count of **250 cells/mm³ or greater** supports SBP in the appropriate setting and warrants prompt treatment.
How do you reduce post-paracentesis leakage?: Use a small catheter and an oblique or Z-track, remove it promptly when drainage is complete and apply firm pressure with an occlusive dressing.