Photoacoustic (PA) endoscopy (PAE) has exhibited potential for providing the complementary contrast to available optical endoscopy methods, particularly for deep vessel imaging. In this Letter, a prototype PA endoscope with shape imaging was developed for the first time, to the best of our knowledge, which utilized the water-balloon-based adapting boundary recognition technique to extract panoramic vascular networks layer by layer. Interestingly, the PA endoscopic probe consists of a low-colored, high-transparency balloon and a 20 MHz ultrasound transducer, which can identify the boundary and construct holonomic vascular networks layer by layer based on the boundary of the balloon with enhanced axial resolution. Phantoms and in vivo rabbit colorectal tests were performed to characterize and inspect the PAE performance. The imaging results demonstrated that the shape-adapting panoramic PAE opens a new avenue for improving the endoscopic imaging capability, holding potential into the colorectal disease detection and guiding treatment in clinical applications.