I took her to the vet on Saturday 'cause they would n't give me antibiotics w/o seeing her . It was all rather easy considering what a pain Trigger at the vet is . Well unfortunately the antibiotics have made her have the runs again . And for some reason when she has the runs she can not do it in the litter box .

Based on the preceding passage, answer the following question Why did their cat need to see the vet ?
Their cat was suffering from diarrhea .