Update release notes for DICOM and API for FHIR

Author: cebundy-work

articles/healthcare-apis/azure-api-for-fhir/release-notes-2026.md

@@ -6,7 +6,7 @@ author: evachen96
 ms.service: azure-health-data-services
 ms.subservice: fhir
 ms.topic: reference
-ms.date: 1/1/2026
+ms.date: 04/10/2026
 ms.custom:
   - references_regions
   - build-2026
@@ -19,6 +19,11 @@ ms.author: evach
 
 Azure API for FHIR® provides a fully managed deployment of the Microsoft FHIR Server for Azure. The server is an implementation of the [FHIR](https://hl7.org/fhir) standard. This document provides details about the features and enhancements made to Azure API for FHIR.
 
+## April 2026
+
+### Bug fixes:
+**Improved monitoring accuracy for Azure API for FHIR**: An issue was identified and resolved that affected Azure Monitor metrics under Microsoft.HealthcareAPIs : CosmosDbThrottleRate, CosmosDbRequests, TotalErrors, and TotalRequests. There was an unsupported aggregation configuration that may have led to inconsistency in data associated with the metrics. This issue was limited to observability scenarios and did not impact service availability, performance, or data processing. After the fix, customers may now observe improved accuracy and consistency in monitoring experiences without requiring any action.
+
 ## March 2026
 ### FHIR service
 **Bulk Export cancellation behavior update**: Added updates to align the FHIR server to support [Bulk Data Access 2.0](https://hl7.org/fhir/uv/bulkdata/STU2/export.html#bulk-data-delete-request). This includes a change to bulk export cancellation behavior. Previously, cancellation request of an already completed, cancelled, or failed export job returned "200 OK." The behavior is now updated to return more informative operation outcomes:

articles/healthcare-apis/release-notes-2026.md

@@ -6,7 +6,7 @@ author: evachen96
 ms.service: azure-health-data-services
 ms.subservice: workspace
 ms.topic: reference
-ms.date: 1/1/2026
+ms.date: 04/10/2026
 ms.author: evach
 ms.custom:
   - references_regions
@@ -18,6 +18,11 @@ ms.custom:
 Release notes describe features, enhancements, and bug fixes released in 2026 for the FHIR® service and DICOM® service in Azure Health Data Services.
 
 ## April 2026
+
+### DICOM service
+
+**DICOM Bulk Update Enhancements**: Enhancements to the Bulk Update capability in the DICOM service now enable more efficient updates to Study, Series, and SOP Instance UIDs—without requiring re‑upload of imaging data. Updates are processed asynchronously, with original instances preserved and all changes recorded for new UIDs. For more information, visit [Update files in the DICOM service in Azure Health Data Services | Microsoft Learn](dicom/update-files).
+
 ### FHIR service
 
 **Improved processing for custom search parameters in bundles**: Implemented validation to detect and prevent conflicting search parameters within bundle requests to help improve search parameter processing. Error messages are returned in case conflicts are found, including: