Bowel displacement for ct-guided tumor radiofrequency ablation: Techniques and anatomic considerations

Purpose: To describe safety and efficacy of bowel displacement techniques and determine lesion characteristics that are likely to necessitate bowel displacement. Patients and Methods: A retrospective review of patients who underwent CT-guided renal tumor radiofrequency ablation (RFA) (January 2006-August 2008) was conducted. Techniques included hydrodissection, additional manual torquing of the RFA probe, and additional angioplasty balloon interposition. The goal was to displace bowel from the probe by at least 10 to 20mm. Air-filled balloon interposition was intended as a thermal barrier. Pre- and postbowel displacement distances were measured by CT. Saline volumes were recorded. Multivariate stepwise regression analysis was used to determine the influence of laterality, renal location, and morphology of renal lesions on their proximity to the colon and use of bowel displacement techniques. Results: RFA was performed on 57 consecutive patients. Eleven (19%) patients had bowel displacement attempts. Median pre-RFA lesion edge to colon distance for nondisplaced vs displaced was 43mm (range 10-100mm) vs 6mm (range 0-16mm), respectively (P<0.05). Two variables were significant for bowel displacement (F-ratio=4.681, P=0.006): Tumor position within the kidney in the craniocaudal plane (P=0.014) and anterior-posterior plane (P=0.007). Lower pole and posterior lesions tended to be closer to the colon and more likely to necessitate bowel displacement. Orientation in the medial-lateral plane (P=0.77) and exophytic nature of the lesion (P=0.83) were not significant features. Hydrostatic bowel displacement was always the first-line technique and was completely and partly successful in 8 (73%) and 1 (9%) attempts, respectively. Partial success was augmented by probe torquing (distance increased from 1mm to 16mm and then to 23mm with torquing). Mean saline injection: 105mL (range 55-440mL). There were two complete failures (18%) in which bowel was displaced only by 0 to 2mm despite injection of 280 to 440mL. Balloon interposition was attempted in these two cases. Five minor complications occurred in the nondisplaced cohort. No complications occurred in the bowel displacement cohort. Conclusion: Lower pole, posterior renal lesions are more likely to necessitate bowel displacement. Bowel displacement techniques are effective and safe in displacing bowel.