A number of washrooms do exit at the park. Always make sure you talk to your guide and explain your condition to him. There is a toilet at the park visitor center as you just enter; these are public washrooms, and you’re free to use them before you start the game drive.
Another washroom room does exist at the hippo pool, where a stopover is always made for lunch hours. Do not expect these washrooms to look as luxurious as one you use at home, and you’re advised to carry toiletries as you head to the park. Toilets are at Muyumbu, Shakani, and Mutumba campsites, and Nyungwe (north) and Kiyonza (south) gates.
Other washrooms are located at the northern gate as you exit the park. These locations are ideal for everyone who could use them.
Make sure you visit the washroom before the start of your long-day game drive to see if you’re in good shape to enjoy your safari without any interruption.