PAIR (Puncture, Aspiration, Injection, and Re-aspiration)
The procedure for drainage of hepatic hydatid cysts is called PAIR (Puncture, Aspiration, Injection, and Re-aspiration), which is a percutaneous minimally invasive technique performed under ultrasound or CT guidance 1, 2.
Procedure Details
The PAIR technique involves the following steps:
- Puncture: The cyst is accessed percutaneously under imaging guidance (ultrasound or CT) using a needle (typically 19-22 gauge) or modified approach with 5-mm laparoscopic trocar for thick-walled or posteriorly situated cysts 2, 3
- Aspiration: Cyst fluid is aspirated (typically 175-300 cc) 1, 4
- Injection: A scolicidal agent is instilled into the cyst cavity—commonly 95% ethanol, 0.05% silver nitrate solution, or 20% saline 4, 5
- Re-aspiration: The scolicidal solution is re-aspirated after appropriate dwell time 1
Essential Adjunctive Therapy
All patients must receive albendazole 10 mg/kg starting 48 hours to 2 weeks before the procedure and continuing for 2-6 months postoperatively to prevent secondary echinococcosis from spilled scolices 4, 5, 6.
Clinical Outcomes
The PAIR technique demonstrates excellent results with:
- Significant cyst size reduction (mean diameter decreasing from 7.5 cm to 3.2 cm) 4
- Low complication rates (2-4% allergic reactions, rare anaphylaxis) 4, 5
- Short hospital stays (1-4 days versus prolonged surgical recovery) 4
- Minimal recurrence when combined with albendazole 5
Important Caveats
PAIR is contraindicated in cysts with biliary communication, superficial cysts at risk of rupture, and cysts with daughter cysts (Gharbi types III-IV). The technique is most appropriate for simple unilocular cysts (Gharbi types I-II) in hemodynamically stable patients 1, 5. For complex cases not amenable to standard PAIR, surgical approaches (laparoscopic or open cyst fenestration/pericystectomy) remain necessary 6.
The modified PAIR using laparoscopic trocars extends applicability to thick-walled, intraparenchymal, and posteriorly located cysts that are difficult to access with conventional needle techniques 2.