According to this article, someone who fits this bill:

Problem patients may exhibit traits that include lengthy care histories from many providers, courses of care dominated primarily by emergency visits, constant complaints about past or current care, ongoing failure to pay for services, and consistent failures to adhere to advice and instructions. These traits are common in plaintiffs and litigious patients. Prudent practitioners who identify these traits early may discharge or not accept these patients. Often, such decisions save time, money, and aggravation. If you care for such a patient, document the care and issues of the problem.

(via The Patient’s Doctor)