Chapter guidance: infections, neoplasms and chronic disease

Where you are

You can move from the Index to the Tabular List and apply the outpatient certainty rule. Now add the chapter guidance that changes how related diagnoses fit together. The same general lookup method still applies, but a chapter may supply a sequencing rule, a required additional code or a distinction that an ordinary dictionary cannot explain.

Keep the April 2026 official guidelines open. This lesson is a guided route through five important topics, not a replacement for reading the applicable paragraph during a real selection. Label every example by setting before you decide which diagnosis comes first.

Build a chapter worksheet

Use five fields: documented condition, relevant relationship, reason for this encounter, chapter instruction and final Tabular check. A relationship might connect a disease to a complication, a cancer to a secondary site or a chronic condition to another affected system.

Do not create relationships merely because two diagnoses appear together. Some relationships are presumed by the classification; others need provider documentation. Check the specific rule and any statement that the conditions are unrelated. The general “with” convention and chapter guidance work together. [icd-guidelines, I.A.15; I.C.9.a]

HIV: distinguish status from disease

The HIV guidance requires confirmed cases. In this context the provider's diagnostic statement can establish confirmation; a coder does not independently demand positive serology before accepting that statement. This is also an exception to the inpatient uncertain-diagnosis rule. [icd-guidelines, I.C.1.a.1]

Separate documented asymptomatic HIV-positive status from documented HIV disease or an HIV-related illness. A patient with a prior HIV-related illness does not move back to the asymptomatic-status category simply because today's note says the patient feels well. Antiretroviral treatment alone does not erase the documented distinction. [icd-guidelines, I.C.1.a.2.a,e,g,j]

For a book drill, find the instructions for a patient with HIV disease admitted for a related condition and then for an unrelated injury. Explain why the reason for admission matters. Read the listed exception rather than memorizing “HIV always first.” Pregnancy adds its own chapter priority. [icd-guidelines, I.C.1.a.2.b,c,h]

Sepsis: do not diagnose from a list of findings

A fever, an elevated heart rate and an infection do not authorize a coder to establish sepsis. Start with the provider's diagnosis and the applicable guidance. The term “urosepsis” is nonspecific and has no default Index code; it requires clarification rather than automatic conversion to sepsis. [icd-guidelines, I.C.1.d.1.a.ii]

For severe sepsis, identify the systemic infection and the associated acute organ dysfunction. The guideline requires the systemic-infection code first, followed by the severe-sepsis code, with additional coding for associated acute organ dysfunction. If an acute organ dysfunction is clearly due to something else, it does not establish severe sepsis. If the relationship is unclear, query the provider. [icd-guidelines, I.C.1.d.1.a.iv–b]

Timing also matters in an inpatient example. Sepsis present on admission with a localized infection and sepsis that develops after admission for a localized infection do not have the same sequencing path. Read I.C.1.d.4 for each situation. Keep this inpatient comparison separate from an office question with an uncertain diagnosis. [icd-guidelines, I.C.1.d.3–4; IV.H]

Neoplasms: behavior, site and purpose of care

Before using the neoplasm table, identify the documented behavior and site. If a histological term is documented, look up that term first to find the correct route. Then verify the candidate in the Tabular List. A mass awaiting diagnosis is not automatically a neoplasm of uncertain histological behavior. Missing information and a documented behavior are different facts. [icd-guidelines, I.C.2, general guidance; IV.H]

For a malignant neoplasm, distinguish the primary site from a secondary, metastatic site. Also identify what receives treatment at this encounter. Treatment directed at the primary malignancy follows one rule; treatment directed only at a secondary site follows another. An encounter chiefly for antineoplastic chemotherapy, immunotherapy or external beam radiation has a specific sequencing instruction. Do not generalize that instruction to every cancer-related visit or to brachytherapy. [icd-guidelines, I.C.2.a–b; I.C.2.e.2]

A former primary site becomes a personal-history situation only when the relevant conditions are met: the malignancy has been excised or eradicated, no further treatment is directed to that site, and no existing primary malignancy remains there. A secondary malignancy can still be active. “History of cancer” in a copied problem list does not replace this review. [icd-guidelines, I.C.2.d]

Diabetes: type, complications and treatment

Diabetes categories use combination codes to describe the type, affected system and complications. More than one code from a category may be needed to describe the documented associated conditions. Sequence according to the encounter and the classification's instructions; do not stop after finding one familiar diabetes entry. [icd-guidelines, I.C.4.a]

Age alone does not establish type 1 diabetes. Insulin use alone does not establish it either. When the type is undocumented, the official default is type 2. Check additional long-term medication-status instructions when applicable. Temporary insulin used to control blood sugar during an encounter does not establish long-term insulin use. [icd-guidelines, I.C.4.a.1–3]

The FY2026 guidance also addresses documented type 2 diabetes in remission. Do not infer remission from a single result or treat “resolved” as a synonym. Query unclear documentation. This illustrates why an old notebook must be checked against the edition in use. [icd-guidelines, I.C.4.a.1.b]

Hypertension: use the relationship rules carefully

The classification presumes certain relationships between hypertension and heart or kidney involvement when linked by its relational terms. That is not permission to connect hypertension to every condition in the chart. Read the specified heart conditions and the chronic-kidney-disease guidance. Explicit documentation that conditions are unrelated changes the selection. [icd-guidelines, I.C.9.a.1–2]

For hypertension with chronic kidney disease, the hypertensive category and an additional code for the CKD stage work together. For hypertensive heart and chronic kidney disease, examine the combined category rather than reporting separate hypertensive heart and hypertensive kidney categories. Additional heart-failure and CKD-stage coding may be required. [icd-guidelines, I.C.9.a.2–3]

Worked comparison

Original fictional office record, August 26, 2026: the clinician manages hypertension and stage 3a chronic kidney disease. Both affect today's plan. No statement says they are unrelated. There is no documented heart disease.

Your worksheet should identify the hypertension/CKD relationship rule, investigate the hypertensive CKD category and retain the stage detail for the additional code. It should not invent heart disease or use a combined heart-and-kidney category. Verify the exact entries and sequencing in your book. [icd-guidelines, I.C.9.a.2]

Now change one fact: the provider explicitly states that the CKD is unrelated to hypertension. Reconsider the relationship rather than keeping the original selection. The clinical facts and the classification rule, together, control the answer.

Book drill

Create five tabs in your notes: HIV, sepsis, neoplasms, diabetes and hypertension. Under each, write one decision that can change coding and its guideline reference. For the worked record, explain the effect of the unrelated-condition statement aloud. Then compare the primary-site, secondary-site and therapy-only neoplasm rules without relying on memory.

Checkpoint

Explain which fact changes the decision in each of the five chapter topics. Identify the applicable guideline before checking your answers.

Check the main distinctions

Prior HIV-related illness matters even when current symptoms are absent. Severe sepsis requires attention to associated acute organ dysfunction. Cancer coding depends on behavior, site and purpose of care. Insulin alone does not establish type 1 diabetes. Hypertension relationships must follow the specific classification instruction and any documented exception.

Sources

1. CDC/NCHS and CMS — ICD-10-CM April 1 2026 Guidelines. FY2026 April. Accessed 2026-09-10.