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Clinical Outcomes of 6-Fr vs 8-Fr Catheters in Percutaneous Transhepatic Gallbladder Drainage: A Propensity Score-Matched Analysis

This propensity score-matched study demonstrates that using 8-Fr catheters for percutaneous transhepatic gallbladder drainage results in significantly fewer adverse events and higher clinical success rates compared to 6-Fr catheters in patients with acute calculous cholecystitis.

Original authors: Tetsushi Azami, Yuichi Takano, Naoki Tamai, Jun Noda, Fumitaka Niiya, Masatsugu Nagahama

Published 2026-06-24

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CC BY 4.0

Original authors: Tetsushi Azami, Yuichi Takano, Naoki Tamai, Jun Noda, Fumitaka Niiya, Masatsugu Nagahama

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine your gallbladder is like a clogged kitchen sink that has become infected and swollen. For patients who are too sick to have surgery, doctors use a procedure called PTGBD to stick a thin tube (a catheter) through the liver and into the gallbladder to drain out the bad, infected fluid. It's like inserting a straw to suck out the sludge so the sink can function again.

For years, doctors have debated: Should the straw be thin (6-Fr) or slightly thicker (8-Fr)?

The Thin Straw (6-Fr): Doctors often thought this was safer because it's smaller, like using a delicate needle. They worried a bigger straw might hurt the liver more or cause bleeding.
The Thick Straw (8-Fr): This one has a wider hole, which should let the thick, chunky sludge flow out faster, but some worried it might be too "rough" for the patient.

This study from Showa Medical University in Japan decided to settle the debate by looking at real patient records. They compared 127 patients who got the thin straw against 149 who got the thick straw. To make sure the comparison was fair, they used a statistical "magic trick" called Propensity Score Matching. Think of this as pairing up patients who are twins in every way (age, health, severity of sickness) so the only difference between the two groups is the size of the straw they received.

What Did They Find?

1. The "Clogged Straw" Problem
The study found that the thin straws (6-Fr) got clogged much more often.

The Analogy: Imagine trying to drain a sink full of wet pasta and eggshells with a tiny coffee stirrer. It gets blocked easily. The thicker straw (8-Fr) was like a wide garden hose; the gunk flowed through it much better.
The Result: Patients with the 6-Fr catheter had a much higher rate of "Adverse Events" (complications). Specifically, the thin tubes were more likely to get blocked or slip out of place.

2. The "Slippery Straw" Problem
The thin straws were also more likely to slip out of the gallbladder.

The Analogy: A thin, flexible straw is like a wet noodle; it wiggles around easily when you breathe or move. A thicker straw is stiffer, like a rigid pipe, so it stays put better inside the body.
The Result: The 6-Fr group had more tubes that moved out of position, requiring doctors to fix them.

3. Did the Bigger Straw Hurt More?
A common fear was that the bigger straw would tear the liver or cause bleeding.

The Result: Surprisingly, no. The study found no difference in bleeding or technical success between the two groups. Both sizes worked just as well at getting into the gallbladder, and neither caused more bleeding.

4. Did the Patients Get Better?

The Result: Patients with the thicker (8-Fr) straw got better faster and more reliably. Their fever went down, and their pain stopped more often than those with the thin straw. While the thin straw worked most of the time, the thick straw worked almost all of the time.

The Bottom Line

The study challenges the old idea that "smaller is always safer."

The 6-Fr (Thin) Catheter: It's like using a tiny, flimsy straw for a messy job. It's more likely to clog, slip out, and fail to drain the infection properly.
The 8-Fr (Thick) Catheter: It's like using a sturdy, wide straw. It drains the gunk better, stays in place, and doesn't cause any extra bleeding or damage compared to the thin one.

The Conclusion: For patients with this specific type of infected gallbladder, the 8-Fr catheter is the better choice. It offers a smoother, more successful recovery with fewer headaches for the doctors and patients, without increasing the risk of injury. The authors suggest that unless there is a very specific reason to use the smaller one, the slightly larger tube is the smarter tool for the job.

Technical Summary: Clinical Outcomes of 6-Fr vs. 8-Fr Catheters in PTGBD

Problem Statement
Percutaneous transhepatic gallbladder drainage (PTGBD) is the standard intervention for acute cholecystitis in patients at high surgical risk. While the procedure has a high technical success rate, the optimal catheter diameter remains undefined. Clinical practice typically utilizes catheters ranging from 6-Fr to 10-Fr, with selection often driven by operator preference and a trade-off between efficacy and safety. Smaller catheters (e.g., 6-Fr) are theoretically less invasive but carry risks of insufficient drainage, occlusion, and dislodgement. Conversely, larger catheters (e.g., 8-Fr) may offer superior drainage but could increase the risk of liver parenchymal injury and bleeding. Prior to this study, evidence regarding the specific impact of catheter diameter on clinical outcomes and safety in PTGBD was scarce.

Methodology
This was a single-center, retrospective observational study conducted at Showa Medical University Fujigaoka Hospital involving patients who underwent PTGBD for acute calculous cholecystitis between January 1, 2017, and August 31, 2025.

Cohort: The study included 276 patients after exclusions for gallbladder cancer, early cholecystectomy, non-6/8-Fr catheters, or early unrelated death. Patients were divided into a 6-Fr group ( $n=127$ ) and an 8-Fr group ( $n=149$ ).
Statistical Adjustment: To address baseline imbalances (notably in antithrombotic therapy and ASA-PS scores), the authors employed Propensity Score Matching (PSM) using 1:1 nearest-neighbor matching without replacement. This resulted in a matched cohort of 71 pairs ( $n=142$ ). A secondary sensitivity analysis using Inverse Probability of Treatment Weighting (IPTW) was performed on the full cohort to validate findings.
Outcomes: The primary outcome was the overall incidence of adverse events (AEs) within 30 days or until discharge/catheter removal, classified by the Clavien–Dindo system. Secondary outcomes included specific AEs (dislodgement, occlusion, bleeding, bile leakage), technical success, clinical success (resolution of fever, pain, and leukocytosis within 5 days), and 30-day mortality.
Definitions: Technical success was defined as successful catheter placement in the gallbladder. Clinical success required normalization of inflammatory markers and symptom resolution.

Key Results
In the propensity score-matched cohort:

Adverse Events: The 6-Fr group demonstrated a significantly higher overall AE rate compared to the 8-Fr group (28.2% vs. 9.9%; Risk Difference [RD] 0.18; Relative Risk [RR] 2.85; $p=0.009$ ).
Specific AEs: Catheter dislodgement was more frequent in the 6-Fr group (19.7% vs. 9.9%), though this did not reach statistical significance ( $p=0.146$ ). Catheter occlusion occurred in 4.2% of the 6-Fr group and 0% of the 8-Fr group. No significant differences were observed in bleeding or bile leakage. All reported AEs were Clavien–Dindo grade I or II; no severe AEs occurred.
Clinical Success: The 8-Fr group achieved a significantly higher clinical success rate (100%) compared to the 6-Fr group (91.5%; RD −0.08; $p=0.041$ ).
Technical Success and Mortality: Technical success was 100% in both groups. There was no significant difference in 30-day mortality (1.4% in 6-Fr vs. 2.8% in 8-Fr; $p>0.999$ ).
Sensitivity Analysis: The IPTW analysis confirmed the primary findings, showing a significantly higher AE rate and lower clinical success in the 6-Fr group, reinforcing the robustness of the results.

Key Contributions
This study provides comparative data on the safety and efficacy of 6-Fr versus 8-Fr catheters in PTGBD, a topic previously lacking robust evidence. It challenges the conventional clinical assumption that smaller catheters are inherently safer for high-risk patients. The findings suggest that the theoretical safety benefit of smaller catheters does not translate to reduced adverse events in practice; rather, the 6-Fr catheters were associated with higher rates of dislodgement and occlusion, leading to lower clinical success. The study highlights that catheter diameter is a critical determinant of drainage efficiency and stability in the context of viscous purulent material found in acute cholecystitis.

Significance and Claims
The authors conclude that 8-Fr catheters are associated with fewer adverse events and higher clinical success rates compared to 6-Fr catheters in patients undergoing PTGBD for acute calculous cholecystitis. While the absolute difference in clinical success is modest, the reduction in adverse events is statistically significant. The paper posits that an 8-Fr catheter may be a reasonable first-line option depending on the clinical context, as it offers a balance of drainage efficiency and catheter stability without increasing technical difficulty or procedural mortality. The authors acknowledge limitations, including the retrospective nature of the study, potential residual confounding, and the single-center design, but assert that the consistent results across PSM and IPTW analyses support the validity of their conclusions.

What Did They Find?

The Bottom Line

Technical Summary: Clinical Outcomes of 6-Fr vs. 8-Fr Catheters in PTGBD

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