LIS, RIS & PACS
The departmental systems behind the EHR — laboratory, radiology and imaging archives. The EHR is the hub; these are the specialist engines that actually run the lab bench and the reading room.
In one line
LIS (Laboratory Information System), RIS (Radiology Information System) and PACS (Picture Archiving and Communication System) are the departmental systems that run lab and imaging work. The EHR places the order and shows the result; these systems do the specialist work in between.
How they connect
An order placed in CPOE travels to the LIS or RIS — classically over HL7 v2 messages (ORM/OML for the order, ORU for the result). Radiology adds DICOM for the images and a Modality Worklist so the scanner pulls verified patient data instead of re-typing it. Practise the imaging side in the Imaging Informatics lab.
Why they stay separate from the EHR
Lab and imaging have deep, specialised workflows — instrument interfaces, quality control, image storage measured in petabytes — that a general EHR doesn't do well. So they remain best-of-breed systems, integrated with the EHR rather than absorbed into it. Increasingly a VNA (Vendor Neutral Archive) stores images independently of any one PACS vendor.
Watch for — the integration seams
Most failures here are at the interfaces: an order that never reaches the LIS, a result that lands on the wrong encounter, an image study with a mismatched patient ID. This is exactly why the integration engine and Modality Worklist exist — the value is in the reliable plumbing between systems, not any one box.