Problem on how to split a multiclass medical dataset

Hello everyone, I am working on a problem trying to train a baseline image classification model to use it later as a feature extractor. However, my issue is that my data are very imbalanced, there are total 8 different lesion categories and a huge gap between the number of patients in each class. How would I ensure a correct way of splitting them into train,val and test sets and guaranteeing that each class appears in each set apart from doing it in a hardcoded way? Below is the number of data and patients in each class for your reference: TRAIN no_lesion: 542 0: 205 1: 131 2: 1393 3: 296 4: 2