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ICD-10 Update Changes Coders’ Thinking

By Leigh Poland, RHIA, CCS, CDIP, CIC

The 2026 ICD-10 update from the CMS and the National Center for Health Statistics, which took effect April 1, appears uneventful on the surface. The ICD-10-CM diagnosis code set saw no additions, deletions, or revisions, and the Official Coding Guidelines stay unchanged. However, focusing only on the code count misses the real story.

The April update is fundamentally structural. Rather than expanding the diagnosis code set, it modifies the logic governing how diagnoses relate to one another within the classification system. Using targeted revisions to instructional notes, exclusions, and sequencing guidance, the update shifts how coders arrive at answers rather than what answers are available.

The ICD-10-PCS procedure classification expands by 80 new procedure codes and removes two existing ones. This reflects persistent innovation in cardiac pacing technologies, hepatobiliary endoscopic drainage techniques, reconstructive urologic surgery, rehabilitation therapies, and emerging biologic treatments.

For inpatient coding teams, clinical documentation integrity leaders, and revenue integrity professionals, the operational ramifications, such as coding variability, reimbursement shifts, and new compliance challenges, are more significant than the update’s modest appearance suggests.

Reshaped Sequencing Logic
The most consequential ICD-10-CM changes involve revisions to sequencing instructions embedded in the tabular list. Across several diagnostic categories, instructions that previously required coders to “code first” an underlying condition or “use additional code” have been replaced with the more flexible instruction “code also.”

“Code first” and “use additional code” established an embedded sequencing hierarchy within the classification. “Code also” removes that hierarchy entirely. Sequencing is no longer determined by the tabular list. It is now guided by the principal diagnosis definition and the clinical circumstances of the encounter. Previously sequenced and grouped conditions are now variable, potentially introducing volatility into MS-DRGs.

Hypertensive Emergency
Category I16.1, hypertensive emergency, illustrates this shift clearly. Previously, associated organ dysfunction was captured through a “use additional code” instruction, strengthening the expectation that the hypertensive crisis would drive sequencing. That assumption no longer holds. With the move to “code also,” coders must now determine whether the hypertensive emergency or the resulting complication represents the condition chiefly responsible for the admission.

In practice, that means evaluating whether the clinical focus—and resource consumption—centers on the hypertensive crisis itself or on complications such as acute kidney injury, myocardial infarction, encephalopathy, heart failure, or cerebral infarction. Sequencing hypertensive emergency first vs sequencing a major complication or comorbidity (MCC)-level condition, such as acute renal failure or cerebral infarction, can shift the case into a different MS-DRG, changing both severity assignment and reimbursement.

Secondary Angle-Closure Glaucoma
A similar shift occurs in category H40.84, neovascular secondary angle-closure glaucoma. The instructional note change from “code first” to “code also” removes the requirement to sequence the underlying condition, such as diabetes, before the glaucoma diagnosis.

Coders must now determine which condition represents the primary reason for the encounter. This creates DRG variability depending on whether the admission focuses on ophthalmologic management or systemic disease control, leading to inconsistent outcomes across similar cases.

Exclusion Note Revisions
The April update also converts multiple Excludes1 notes to Excludes2 notes across several ICD-10-CM chapters. Within ICD-10 logic, this is a fundamental shift. An Excludes1 note is a “pure exclusion.” Conditions cannot be reported together. An Excludes2 note signals that conditions are distinct and may coexist. Converting Excludes1 to Excludes2 expands the set of clinically valid code combinations. Several high-impact areas illustrate the operational implications.

Hematologic and Immune Disorders
Revisions affecting vitamin B12 deficiency anemia, disseminated intravascular coagulation (DIC), neutropenia, and decreased white blood cell counts allow concurrent reporting when documentation indicates distinct conditions. For example, a patient with a tubal pregnancy complicated by DIC may now have both conditions reported—an outcome previously restricted under Excludes1 logic.

Respiratory Failure
The revision to J95.82 (postprocedural respiratory failure) is especially important. Under prior Excludes1 logic, coders could not report postprocedural respiratory failure alongside other respiratory failure diagnoses. With conversion to Excludes2, both may now be coded when clinically appropriate.

For example, a patient admitted with chronic respiratory failure who develops acute postprocedural respiratory failure following surgery may have both conditions reported. This creates new DRG implications. Depending on sequencing and present-on-admission status, these diagnoses may influence CC/MCC assignment and shift case severity.

Medication Status and Substance Use
Revisions to Z79.891 (long-term opiate use), including the reclassification of methadone-related exclusions, introduce additional flexibility in reporting combinations involving medication use and substance-related disorders. Operationally, these changes expand coding opportunities—but also increase the risk of scrutiny. Coders who rely on legacy exclusion logic may miss valid operational reporting opportunities. Meanwhile, newly permitted code combinations increase the risk of payer review unless documentation robustly confirms clinical coexistence, thereby affecting coding accuracy and audit exposure.

Alphabetic Index Revisions
Changes to the Alphabetic Index further reinforce that this update is about classification pathways, not just code sets. One important revision redirects neuroendocrine tumor indexing to malignant codes in category C7A rather than benign codes. This shift has direct reimbursement implications.

Because C7A codes qualify as complications or comorbidities, cases involving these diagnoses may now be grouped differently, which may affect the case mix index and reimbursement outcomes. Index changes are often overlooked because they do not alter code descriptions. However, they can materially change how coders arrive at a diagnosis and, therefore, how cases are reimbursed.

Advanced Cardiac Pacing
New codes capture intracardiac lead placement within the ventricular septum, supporting conduction system pacing techniques designed to preserve physiologic cardiac activation. Accurate coding requires precise documentation of device type, anatomical placement, and approach—details that may not have been consistently required under prior coding structures.

Hepatobiliary and Pancreatic Drainage
New qualifiers distinguishing transpapillary and transmural approaches allow coders to differentiate advanced endoscopic techniques used in endoscopic retrograde cholangiopancreatography and endoscopic ultrasound-guided procedures. These distinctions are critical in complex cases involving pancreatic fluid collections, biliary obstruction, or hepatic duct drainage, where multiple access routes and devices may be used.

Urologic Reconstruction
A new PCS table enables reporting of bladder transfer procedures to the ureter, such as the Boari bladder flap, improving specificity for reconstructive urologic surgery.

Stem Cell Therapy Reclassification
The reclassification of embryonic stem cell administration from Transfusion to Introduction aligns the procedure with PCS definitions describing the administration of therapeutic substances rather than blood products. This is a structural correction that affects how these therapies are conceptually categorized within the system.

Rehabilitation and Wound Care
Expansion within the Physical Rehabilitation and Diagnostic Audiology section introduces new codes for electrotherapeutic treatments, including microcurrent stimulation, along with greater anatomical specificity.

New Technology Section Growth
The New Technology section continues to expand, capturing emerging therapies such as venous stent systems, tissue-engineered vascular scaffolds, intracochlear gene therapy infusion, immunotherapies, and enzyme replacement treatments. These codes allow hospitals to report innovative procedures during early adoption, supporting both reimbursement and longitudinal data tracking.

Operational Implications
Although the April update is smaller than a typical annual revision, its operational impact is substantial, particularly on scheduling and resource allocation. This is not a documentation-only change or a code-addition cycle. It is a change to the classification system's internal logic.

Ultimately, these logic changes demand decisive attention from coding and revenue integrity teams. The April update is an opportunity for organizations to review workflows, educate staff, and proactively align coding practices with updated logic. Failure to act risks serious financial and compliance consequences. This update is an urgent call to act—ensure your coding strategies, education, and audit processes reflect the new structural reality.

Early auditing will be critical. Organizations should prioritize review of hypertensive emergency and secondary glaucoma cases, where sequencing variability is most likely to emerge under the revised structure.

At the same time, coding teams must be educated on newly permitted diagnosis combinations resulting from Excludes2 conversions, and encoder systems must be validated to ensure that updated PCS tables and qualifiers are functioning correctly.

Quiet Updates That Carry Real Risk
By removing embedded sequencing hierarchy, expanding permissible diagnosis combinations, and adding new procedural specificity, the April 2026 ICD-10 update shifts more responsibility to coder judgment and documentation clarity. Organizations that treat this as a “no-change” update risk coding inconsistency, DRG instability, and increased audit exposure. Those who recognize it for what it is, a logic shift, will be better able to maintain both compliance and financial accuracy.

— Leigh Poland, RHIA, CCS, CDIP, CIC, is vice president for coding services, clinical quality, and education with AGS Health, responsible for managing the continuous coding education and certification preparatory programs for more than 3,500 coders. With more than 25 years of coding experience, she is the company’s coding expert, is a key advisor to the AGS Health International Coding Training Academy, and offers mentoring and guidance to its internal auditing team.