ICD-10-CM and ICD-10-PCS Coding Updates Effective April 1, 2026

Overview of the April 1 ICD-10-CM and MS-DRG Updates

The release of updates for ICD-10-CM and for grouper V43.1 are now available from CMS and the CDC. The new updates will take effect on April 1,2026. Let’s break down three important changes for the CDI professional.

ICD-10-CM Index Update: Parkinson’s Disease Coding Revision

The release of the April 1, ICD-10-CM update includes a significant revision affecting how Parkinson’s disease is indexed. A new subterm “Parkinson’s disease – see Disease, Parkinson’s” has been added under the main term Parkinsonism, along with a new subterm “due to.” Additionally, the previous main term “Parkinson’s disease, syndrome, or tremor – see Parkinsonism” has been deleted and replaced with two clearer, more specific main terms:

• Parkinson’s disease – See Diseases, Parkinson’s
  
• Parkinson’s syndrome or tremor – See Parkinsonism

Why this matters: A documented diagnosis of Parkinson’s disease will now direct coders to G20.A1, rather than the former path that led to G20.C. This distinction improves clinical specificity but makes accurate provider terminology more critical than ever.

CDI Takeaways:

• Parkinsonism and Parkinson’s disease are not interchangeable—verify that documentation reflects the correct diagnosis.
  
• Look for causal language such as “due to meds,” “vascular,” or “secondary to…” to support appropriate code assignment.
• Query when documentation is vague (e.g., “Parkinsonian features,” “Parkinsonism”) and clinical indicators support confirmed Parkinson’s disease.
• Treatment clues such as levodopa/carbidopa may support clarification.
• The updated indexing impacts severity capture and risk adjustment, making specificity essential.

ICD-10-CM Update: Respiratory Failure Excludes1 Note Changed to Excludes2

• In Chapter 10 (J00–J99) Diseases of the Respiratory System, a key revision has been made involving respiratory failure coding. The Excludes1 note that previously prevented assigning J96.- Respiratory failure, not elsewhere classified alongside J95.82 Postprocedural respiratory failure has been changed to an Excludes2 note.

What this means: Clinically appropriate cases may now report both J96.- and J95.82 together, allowing more accurate capture of situations where a patient has pre-existing acute/chronic respiratory failure and develops postprocedural respiratory failure during the same admission.

CDI Takeaways:

• Ensure the provider clearly documents timing: Was respiratory failure present prior to surgery, or did it arise after a procedure?
• Look for clinical indicators that support dual diagnoses, such as baseline hypoxemia, NIV use, reintubation, increased ventilatory support, or ABG changes.
• Query when documentation is vague (e.g., “respiratory failure” in a postop patient without clarification).
• Distinguish between postoperative respiratory insufficiency and postoperative respiratory failure—they are not interchangeable.
• Remember that accurate documentation of both types of respiratory failure may impact PSI-09, SOI/ROM, and overall severity capture.

ICD-10-CM Index Update: Neuroendocrine Tumor Coding Change

• A notable ICD-10-CM update affects code assignment for neuroendocrine tumors. The Index entry previously directing coders from the terms “Tumor” and “neuroendocrine” to D3A.8 Other benign neuroendocrine tumors has been revised. The Index now points to C7A.- Malignant neuroendocrine tumors.

Why this matters: Codes in category C7A.- are CCs, whereas D3A.8 is not. This update means documentation that indexes to neuroendocrine tumors will now capture a CC, improving severity and accuracy in reporting when clinically appropriate.

CDI Takeaways & Tips:

• Verify provider intent: benign vs. malignant.
• The term “neuroendocrine tumor” can represent a spectrum—from benign NETs to malignant neuroendocrine carcinomas.
• If the provider’s intent is unclear, a query may be required.
• Confirm whether the tumor represents a malignancy, carcinoma, or low-grade malignant NET, as this affects correct C7A.- assignment.
• Watch for grade, differentiation, and terminology changes. Providers may use terms such as:
• “well-differentiated NET”
  
• “Carcinoid tumor”
• “Neuroendocrine carcinoma (NEC)"
• These phrases may indicate malignant behavior even if “malignant” is not explicitly stated.
• Review pathology reports carefully.
• Pathology often determines tumor behavior. Look for descriptors such as:
• Low-, intermediate-, or high-grade
• Ki-67 index
• mitotic rate
• If pathology confirms malignancy but the operative/progress notes do not reflect it, consider sending a query.
• Distinguish primary vs. metastatic sites.
• C7A.- codes require identification of the primary site when possible.
• If documentation only lists a “neuroendocrine tumor” of a secondary location (e.g., liver), verify whether there is:
• A known primary tumor OR
• True primary hepatic NET (rare)



Alyce Reavis, RN,MSN,CCDS,CCS 

Senior CDI Educator, Consulting Services at UASI

Drawing on clinical experience in adult, pediatric, and neonatal acute care, Alyce brings valuable insight to CDI education and documentation improvement. She holds an MSN in Leadership/Education along with CCDS, CCS, and AHIMA’s outpatient CDI micro credential, supporting health systems in strengthening documentation accuracy, quality reporting, and reimbursement integrity. Passionate about truthful, clinically aligned health records, she helps organizations ensure documentation reflects true patient acuity. She is a past presenter for the ACDIS National Convention, Local chapter meetings, and the ACDIS Virtual Best Practices conference. 



Works Cited

Centers for Medicare & Medicaid Services. (2026). ICD-10 MS-DRGs Version 43.1 effective April 1, 2026. Available at: https://www.cms.gov

Greenwood, C. (2026). ICD-10-CM code updates – April 1, 2026. hiacode Industry News. Available at: https://hiacode.com/blog/icd-10-cm-code-updates-april-1