The University of California, San Francisco, Committee on Human Analysis and the institutional review panel at each participating site authorized the study. All participants gave written informed consent. Initial Imaging Point-of-treatment ultrasound examinations had been performed by emergency doctors who had had teaching as recommended by the American College of Emergency Doctors. Radiology ultrasound examinations had been performed in radiology departments according to the suggestions of the Culture of Radiologists in Ultrasound or the American Institute of Ultrasound in Medicine.Statistical Analysis We assumed a 50 percent decrease in the recurrence price with penicillin in comparison with placebo on the basis of a log-rank check for time-to-event data, with 80 percent power at a two-sided significance degree of 5 percent and an expected 20 percent rate of reduction to follow-up. Previous studies have shown possible recurrence rates of 30 to 50 percent, with respect to the populace and the duration of follow-up.13,14 For the relapse rate in the placebo group, we used a conservative estimate of 35 percent over a period of three years. These calculations led to a sample size of 260 individuals. All analyses were prespecified in the statistical analysis plan.