Bubbles are frequently encountered during esophagogastroduodenoscopy (EGD) and may impair adequate mucosal visualization (MV). The primary objective of this study was to evaluate the effect of pre-endoscopic simethicone administration on mucosal visibility using the GRACE (Gastroscopy Rate of Cleanliness Evaluation) scale. Secondary objectives included assessment of procedure duration, endoscopist satisfaction, and the detection rate of endoscopic findings.

This was a prospective, single-center, randomized, blinded study including patients undergoing elective EGD between December 2024 and November 2025. Patients were randomized into three groups: A (100 mg simethicone ≤10 minutes before EGD), B (100 mg simethicone >10 minutes before EGD), and C (50 mL water, placebo). All received a total volume of 50 mL. Patients with gastroparesis, achalasia, or prior gastrointestinal surgery were excluded. MV was assessed using the GRACE scale (validated in 2024), which scores each segment (esophagus, stomach, duodenum) from 0 to 3 based on bubble quantity, resulting in a total score from 0 (inadequate) to 9 (excellent). Endoscopist satisfaction was subjectively assessed on a scale from 0 (not satisfied) to 10 (highly satisfied). 

A total of 142 patients were included (33 in group A, 54 in group B, and 55 in group C). Overall, 87 patients received 100 mg of simethicone and 55 received placebo. Median administration times were 9 minutes in group A and 20 minutes in group B. Simethicone significantly improved MV compared with placebo (mean GRACE score: 5.71 ± 1.70 vs 7.70 ± 1.50; p < 0.001), with significant improvements in all segments (esophagus: 2.00 (1-3) vs 3.00 (2-3), p < 0.001; stomach: 1.00 (1–2) vs 2.00 (2–3), p < 0.001; duodenum: 2.00 (2–3) vs 3.00 (2–3), p < 0.001). No correlation was observed between timing of simethicone administration and total GRACE score (Pearson r = –0.079; p = 0.469). Endoscopist satisfaction was higher in the simethicone group (6.25 ± 1.82 vs 8.01 ± 1.76; p < 0.001). No significant differences were found in median procedure duration (7.00 min (5-9) vs 7.00 min (5-9); p = 0.948) or diagnostic yield (χ²(1) = 1.114; p = 0.291). Among patients receiving simethicone, early administration showed no significant advantages over late administration: median EGD duration was 7.00 min (6–8) vs 8.00 min (6–10), and diagnostic findings 75.8% vs 83.3%, respectively (χ²(1) = 0.748; p = 0.387).

Pre-endoscopic simethicone significantly improved mucosal visibility across all upper GI segments, independent of administration timing. No statistically significant differences were observed between early and late administration with respect to mucosal visualization, procedure duration, or diagnostic yield. High endoscopist satisfaction and consistent improvements in visibility support the routine use of simethicone prior to EGD.