Association of gallbladder fossa depth ratio with catheter trajectory during percutaneous transhepatic gallbladder drainage

Purpose This study evaluated whether conventional ultrasound-guided percutaneous transhepatic gallbladder drainage (PTGBD) consistently traverses the perimuscular connective tissue (PMCT) within the gallbladder fossa, aiming to explore a quantitative trajectory-related imaging parameter associated with computed tomography (CT)-defined catheter dislodgement. Methods A single-center investigation was conducted in two sequential phases: (1) a retrospective analysis of 100 patients who underwent PTGBD for acute cholecystitis from 2021 to 2024, assessing catheter position, depth ratio of the gallbladder fossa (DRGF), projected ratio of the gallbladder length (PRGL), and gallbladder dimensions on CT and ultrasound. Receiver operating characteristic (ROC) analysis estimated an exploratory DRGF cutoff for discriminating the CT-defined endpoint. (2) A prospective intraoperative evaluation was performed in 50 patients undergoing laparoscopic cholecystectomy to characterize PMCT distribution and dimensions. Results A CT-defined catheter configuration suggestive of PMCT non-traversal was identified in 8 of 100 patients (8.0%). DRGF was significantly lower in the properly positioned catheter group ( P < 0.001), whereas PRGL and gallbladder dimensions showed no significant differences. ROC analysis demonstrated an area under the curve (AUC) of 0.906 for DRGF in discriminating the CT-defined endpoint, with an exploratory cutoff of 65.69 (sensitivity, 87.5%; specificity, 83.7%). Intraoperative observations confirmed that PMCT was concentrated at the deepest portion of the gallbladder fossa. Conclusion Conventional PTGBD did not consistently produce a catheter trajectory with a CT appearance consistent with PMCT traversal. DRGF should be regarded as an exploratory trajectory-related imaging parameter. A lower DRGF was associated with a CT-inferred catheter trajectory consistent with PMCT traversal and a lower likelihood of CT-defined catheter dislodgement, although prospective validation is required.