Most importantly, all actions of collection for past due amounts should cease immediately upon notice of the bankruptcy. If you are using an outside source for collections, be sure they are aware of the bankruptcy and take the appropriate action. An attempt to collect the unpaid fees is a violation of a court order and can cost you plenty in attorney fees, court costs and punitive damages.
Generally, a provider can discharge a patient when the doctor/patient relationship has become broken.  However, keep in mind that refusing to give the patient any more appointments based on non-clinical reasons (e.g. past due accounts) could be considered constructive abandonment and should be avoided. Regardless of whether the debt is discharged in bankruptcy, the provider should not be obligated to treat someone for free.  Consult a bankruptcy lawyer to confirm if that rationale is correct in your jurisdiction.  And, depending on the type of bankruptcy, some debts may still be paid, again, your attorney can advise you further on your options such as filing a claim with the court.
The healthcare provider should keep in mind that standards of care still need to be adhered to, even if a bankruptcy is involved. Once a healthcare provider has undertaken a course of treatment, the healthcare provider should not discontinue that treatment without giving the patient adequate notice and the opportunity to obtain the services of another provider. Care should be taken that the patient’s health is not jeopardized in the process.