A catheter assembly and related methods for preparing and assembling catheter assemblies. The catheter assembly includes main and side balloons. The main balloon includes side portions that are folded in opposite directions toward a bottom surface of the main balloon to place the main balloon in a folded state. The side balloon is typically positioned along a top surface of the main balloon. The folded balloons can be retained in a folded state with various retaining structures during further preparation and assembling of the catheter assembly.