Intrauterine Fluid Instillation and Transtubal Flow: A Randomized Controlled In vitro Trial Comparing Gel and Water

BACKGROUND: Possible transtubal spillage of malignant cells is a major concern in fluid instillation sonography, as it is in hysteroscopy. This study aims to compare the transtubal flow of gel and saline and validate the clinical hypothesis that application of fluids with higher viscosity causes less spillage. METHODS: Randomized controlled in vitro trial comparing gel and saline infusion on 15 tissue specimens after hysterectomy with bilateral salpingectomy. Instillations are performed with saline and gel dyed with a 1% ink solution. Qualitative assessment of tubal spill is investigated as primary outcome. Secondary outcomes are instillation-volume and -pressure, assessed by measuring endometrial cavity dilation at in vitro ultrasound examination and subjective numeric 10-point scoring of the instillation pressure by a dedicated examiner. RESULTS: Tubal flow was more often observed during saline instillation (odds ratio 4.88, P = 0.008). Median subjectively assessed instillation pressures were nine arbitrary units for gel and three for saline (P < 0.001). Tubal flow occurred from 2 cc onward in the saline group versus five cc in the gel instillation group. Cavitary dilation did not differ between both groups. CONCLUSION: Gel instillation sonography is in vitro associated with less tubal flow and therefore could be a safer diagnostic test compared to saline infusion sonography or hysteroscopy. In vivo studies are necessary to confirm these results.