...attended/attended to the patient.

The doctor (gave medical care ) to the patient.

The doctor (paid attention to ) the patient.

We can conventionally use the word "attend" (alone) to say that a doctor or nurse visited the patient in a professional capacity and, if necessary, treated them.

The phrase "attended to" does not mean that.

Punkey is correct and should not have been voted down.

Thanks, Punkey and contrex.