Rationale:

There is no high-level-of-evidence data to support the general notion that a fat-free diet is beneficial to patients with gallstone disease. Herein, we assess the feasibility and safety of a randomized study to assess the effect of recommending a fat-free diet versus a balanced-WHO diet on the quality of life (QoL) in symptomatic patients with gallstones (RADIGAL-1) and in patients undergoing cholecystectomy for gallstone disease (RADIGAL-2).

Methods:

This is a multicenter, randomized, single-blind, parallel-arm, non-inferiority trial. Patients presenting with biliary colic or acute cholecystitis or undergoing cholecystectomy for gallstones are randomly assigned to recommending either a fat-free or a balanced WHO diet. A follow-up at 3 months will appraise patient adherence and outcomes. A validated quality-of-life questionnaire (GIQLI) will be administered both at baseline and during follow-up. A total of 136 patients will be recruited for RADIGAL-1 and 106 for RADIGAL-2 according to sample size calculation based on the mean clinically important difference of GIQLI scores.

Results:

The rate of recruitment in the participating centers is eight patients per month for RADIGAL-1 and twenty for RADIGAL-2. In RADIGAL-1, full compliance was recorded in 87.8% of the patients. Additionally, 2.4% of the patients followed the diet for more than 50% of the follow-up time, while 4.8% followed it for less than 50% of the time. In RADIGAL-2, full compliance was recorded in 88.3% of the patients. Moreover, 8.3% of the patients followed the diet for more than 50% of the follow-up time, and 3.3% followed it for less than 50% of the time. Drop-off rates are 2.4% for RADIGAL-1 and 1.7% for RADIGAL-2. No adverse events such as hospital admissions or biliary colic have occurred in excess in the control groups.

Conclusion:

These data support the safety and the feasibility of the RADIGAL trial (NCT06405906).