Why is my patient leaving?

I'm in Scenario 2, trying to run the General Surgery department. I had a patient who was unable to be treated, because he needed Shock wave lithotripsy. I hovered over the treatment, said it required a Sonography Unit and said the hospitalization for the treatment was not available. So, I added a Sonography Unit, and the guy ended up leaving.

What happened?

Because they need shock wave lithoscopy and hospitalisation to treat their condition. Reading the grey box tells me you don't have hospitalisation available.

Does that mean HDU or ICU? I'm not always sure which beds a patient needs.

ICU is a separate department.

Select the department type related to that condition (it shows up if you hover over the condition symbol), then click management mode (the three cog symbol). Any rooms or staff types with a red number next to them are rooms you need to open hospitalisation.