There are several medical issues that can interfere with potty training. Dogs with a urinary tract infection (UTI) will urinate frequently in small amounts, and will not have much control. You may also notice excessive licking of their genital region. If you notice a change in the consistency of their stool, the cause could be a gastrointestinal issue. Some common causes in puppies are intestinal parasites, having eaten something not in their normal diet, or a sudden food change. If a food change is necessary, do it gradually over 5 to 7 days. If you suspect any of these issues could be a problem, you should consult with your veterinarian.
The process is the exactly same for older dogs as it is for puppies; prevent accidents from happening by using baby gates and a crate if possible, create a predictable schedule, learn to recognize your dog’s potty signals, accompany your dog outside and immediately reward for all outdoor elimination, properly clean any accidents and supervise your dog until you’re sure that he understands the rules.