The purpose of this study is to determine whether the use of antibiotic prophylaxis is appropriate when performing a pancreatic cyst fine needle aspiration guided by endoscopic ultrasonography.

The incidence of infection after a pancreatic cyst fine needle aspiration guided by endoscopic ultrasonography (EUS-FNA) is not well known. Antibiotic prophylaxis is recommended in clinical guidelines despite the lack of evidence of its usefulness.

Our hypothesis is that the risk of infection will not be higher with placebo, and risks associated to the use of antibiotics might even increase with the use of prophylaxis.

The main objective of the project is to assess the risk of infection after the procedure and to determine whether the use of antibiotic prophylaxis is appropriate. The study is a phase IV, multicenter, double-blinded, randomized, placebo-controlled, and non-inferiority trial . We have designed a study with two parallel treatment groups. Patients will be randomized to the prophylaxis or to the placebo group. All patients will be followed for 21 days or until resolution of complications. To evaluate this primary objective with a non inferiority study, we have estimated that a total of 218 patients will be needed (109 per group) .

The main secondary objective is to assess the incidence of complications related to the use of antibiotic prophylaxis (i.e. allergic reactions, secondary infections or drug-resistant infections).

Inclusion Criteria:

• Patients with a pancreatic cyst requiring EUS-FNA to complete evaluation.
• Participant is willing and able to give informed consent for participation in the study.
• Age 18 years or older.
• Ability to understand study procedures and to comply with them for the entire length of the study.

Exclusion Criteria:

• Patients with other co-morbidities requiring antibiotic prophylaxis for endoscopic invasive procedures (such as those with cardiac valve prosthesis).
• Cystic lesion of the intestinal wall (foregut or duplication cyst).
• Use of antibiotic treatment for any other indication during the 5 days prior to the procedure.
• Pregnant woman.
• Known allergy/sensitivity to ciprofloxacin.
• Inability or unwillingness of individual or legal guardian/representative to give written informed consent.