- A patient is admitted for dehydration secondary to acute gastroenteritis. The gastroenteritis resolves, but the dehydration continues to require IV fluid therapy. Which condition is the principal diagnosis at discharge?
Answer: Dehydration
The principal diagnosis is determined after study as the condition chiefly responsible for the admission. The gastroenteritis resolved while the dehydration persisted and required ongoing IV fluid treatment. Dehydration is therefore the condition that remained the focus of care and is sequenced as the principal diagnosis. If both conditions were still active and equal at discharge, either could be listed first.
- A patient intentionally takes an overdose of acetaminophen in a suicide attempt and is admitted for treatment of liver toxicity. How are the poisoning and manifestation codes sequenced?
Answer: The poisoning code (with intent 7th character) first, followed by the manifestation (liver toxicity)
For poisoning (incorrect drug, wrong dose, wrong route, or intentional overdose), the poisoning code from the T36-T65 range is sequenced first, with the 7th character indicating intent (intentional self-harm). The manifestation (liver toxicity) is then reported as a secondary code. This is the reverse of adverse effect sequencing, where the manifestation comes first.
- A patient takes a prescribed medication at the correct dose and develops an allergic reaction. The coder must report an adverse effect. How are adverse effect codes sequenced?
Answer: The manifestation (e.g., allergic reaction) is sequenced first, followed by the adverse effect code
For adverse effects (correct drug, correct dose, correct route — patient had an unexpected reaction), the manifestation (the nature of the adverse reaction, e.g., allergic urticaria, anaphylaxis) is sequenced first. The adverse effect code from the T36-T65 range (with the appropriate 7th character for adverse effect) is then reported as an additional code to identify the responsible drug.
- An outpatient patient presents with chest pain. After evaluation, the physician's final assessment is "chest pain, rule out myocardial infarction." What is the correct first-listed diagnosis for this outpatient encounter?
Answer: Chest pain
For outpatient coding, "rule out" conditions are not coded as if confirmed. The ICD-10-CM Official Guidelines instruct outpatient coders to report the sign or symptom (chest pain) rather than the unconfirmed condition being ruled out. This differs from inpatient coding, where a rule-out condition may be coded as if established when it is still under investigation at discharge.
- A patient is admitted following a myocardial infarction that occurred 5 weeks ago and is now presenting with ongoing complications. Which ICD-10-CM code category applies?
Answer: I25 — Chronic ischemic heart disease
ICD-10-CM category I22 (Subsequent myocardial infarction) applies only when a new MI occurs within 4 weeks of a prior MI. An MI that occurred 5 weeks ago falls outside this window; the appropriate category is I25 (Chronic ischemic heart disease), specifically I25.2 (Old myocardial infarction), used when the patient is no longer receiving active care for the original event. I21 is for an acute MI currently under treatment; I23 is for specific complications arising during the acute phase.
- A patient with a known primary malignant neoplasm of the colon presents with a pathologically confirmed metastasis to the liver. The patient is admitted for treatment of both sites. Which condition is sequenced first?
Answer: Primary malignant neoplasm of the colon
Per ICD-10-CM Official Guidelines, when treatment is directed at both a primary and secondary (metastatic) malignancy, the primary malignancy is sequenced first. The secondary malignancy (metastasis to the liver, C78.7) is reported as an additional diagnosis. If treatment were directed only at the metastasis and the primary was no longer under active treatment, the metastasis would be sequenced first.
- A patient is seen in the outpatient clinic for a pre-operative physical examination before an elective knee replacement. The physician finds no new problems. Which is the correct first-listed diagnosis?
Answer: Pre-operative examination (Z01.818)
For a pre-operative examination in the outpatient setting, the appropriate Z code is sequenced as the first-listed diagnosis. Z01.810 is specifically limited to the pre-procedural cardiovascular examination. Z01.818 covers all other pre-procedural examinations — including orthopedic pre-operative evaluations — and is the correct code for this encounter. The condition necessitating the upcoming surgery (osteoarthritis of the knee) is reported as a secondary diagnosis.
- A patient is admitted for chemotherapy for primary malignant neoplasm of the breast. The patient receives the chemotherapy without complication. Which diagnosis is sequenced as the principal diagnosis?
Answer: The chemotherapy encounter code (Z51.11)
Per ICD-10-CM Official Guidelines, when a patient is admitted solely to receive chemotherapy, the encounter for antineoplastic chemotherapy (Z51.11) is sequenced as the principal diagnosis. The malignancy being treated is then reported as a secondary diagnosis. This is an exception to the general rule of sequencing the underlying condition as principal.
- A patient is admitted for surgical repair of a hip fracture. The fracture occurred as a result of a fall from a ladder at a construction site. How are the fracture and external cause codes sequenced?
Answer: Fracture code first, followed by the external cause codes for mechanism, place, and work status
The injury code (fracture) is always sequenced as the principal or first-listed diagnosis. External cause codes provide supplemental information and are never sequenced as the principal diagnosis. For this scenario, W11.XXXA (fall on and from ladder, initial encounter) captures the mechanism, Y92.61 (construction area as place of occurrence) captures the location, and Y99.0 (civilian activity done for income or pay) captures the work status. These are all reported as additional codes.
- A patient is diagnosed with anemia due to chronic kidney disease. The ICD-10-CM Tabular List shows "code also" instructions linking these conditions. Which sequencing is correct?
Answer: CKD first, then anemia (D63.1), per the manifestation sequencing convention
D63.1 is anemia in chronic kidney disease — this is a manifestation code. Per the etiology/manifestation convention, the underlying disease (CKD) is sequenced first, followed by D63.1 for the anemia manifestation. Manifestation codes cannot serve as the principal diagnosis. The CKD code is the etiology and belongs first in the sequence.
- A patient with type 2 diabetes is admitted for diabetic chronic kidney disease, stage 3. The ICD-10-CM Tabular List shows an instructional note under the diabetes code stating "Use additional code to identify stage of CKD." How are these conditions sequenced?
Answer: Diabetes with CKD (E11.22) first, then CKD stage 3 (N18.3)
ICD-10-CM combination code E11.22 covers type 2 diabetes mellitus with diabetic chronic kidney disease. E11.22 is sequenced first as the principal or first-listed diagnosis, with N18.3 (CKD, stage 3) reported as an additional code per the Tabular List instruction "Use additional code to identify stage of CKD." The use additional code instruction always follows the primary code. E11.65 covers type 2 DM with hyperglycemia and does not capture the diabetes-CKD relationship.
- A patient is admitted with acute systolic heart failure and is also found to have chronic atrial fibrillation and type 2 diabetes, both stable and managed during the admission. Which condition is the principal diagnosis?
Answer: Acute systolic heart failure
The principal diagnosis is the condition determined after study to be chiefly responsible for the hospital admission. Acute systolic heart failure is the acute condition that necessitated the admission. Chronic atrial fibrillation and type 2 diabetes are comorbidities coded as secondary diagnoses because they were managed but did not drive the admission.
- A patient with HIV disease is admitted for Pneumocystis jirovecii pneumonia (PCP). How are these conditions sequenced?
Answer: HIV disease (B20) first, then PCP (B59)
Per ICD-10-CM Official Guidelines, when a patient with HIV disease is admitted for an HIV-related condition, B20 (HIV disease) is always sequenced as the principal diagnosis, followed by the HIV-related condition (B59 for PCP). B20 takes sequencing priority over all HIV-related manifestations and complications. Z21 (asymptomatic HIV status) is used only when the patient has no documented symptoms or opportunistic infections.
- A patient undergoes an elective total hip replacement for osteoarthritis of the left hip. The postoperative note documents the procedure as status post left total hip arthroplasty, no complications. For the surgical inpatient admission, which condition is the principal diagnosis?
Answer: Primary osteoarthritis of the left hip (M16.12)
The principal diagnosis for a surgical admission is the condition that prompted the need for surgery — the osteoarthritis of the left hip (M16.12). Z96.641 (presence of left artificial hip joint) is a status code reported after surgery to indicate the implanted device. Z48.89 is a follow-up code not appropriate as the principal diagnosis for the surgical encounter itself.
- The ICD-10-CM Tabular List instructs "Code first underlying disease" beneath a manifestation code. Which sequencing rule does this instruction reflect?
Answer: The etiology code is sequenced first, followed by the manifestation code
The etiology/manifestation convention in ICD-10-CM requires that the underlying disease (etiology) be sequenced first, followed by the manifestation code. Manifestation codes (often shown in italics in the Tabular List) cannot be used as principal or first-listed diagnoses. The "Code first" and "Use additional code" instructions enforce this required sequencing.
- A patient is admitted to the hospital with fever, cough, and shortness of breath. After workup, the physician documents a final diagnosis of community-acquired pneumonia due to Streptococcus pneumoniae. Which diagnosis is reported as the principal diagnosis?
Answer: Pneumonia due to Streptococcus pneumoniae (J13)
For inpatient coding, the principal diagnosis is the condition established after study to be chiefly responsible for the admission. Once a definitive diagnosis is established, signs and symptoms (fever, cough, shortness of breath) that are integral to the condition are not reported separately. J13 is the correct and only principal diagnosis.
- Two conditions that meet the definition of principal diagnosis are both present at discharge and either could have been selected. The ICD-10-CM Official Guidelines address this situation. What is the correct action?
Answer: Either condition may be sequenced as the principal diagnosis
The ICD-10-CM Official Guidelines state that when two or more interrelated conditions each meet the definition of principal diagnosis and are equally responsible for occasioning the admission, either may be sequenced first. The coder may use clinical judgment and available documentation but is not required to seek physician clarification in this specific circumstance.
- A patient presents with acute-on-chronic respiratory failure. Both the acute and the chronic components are documented. How are these conditions coded?
Answer: A combination code for acute-on-chronic respiratory failure is used
ICD-10-CM provides a combination code for acute-on-chronic respiratory failure. For example, J96.20 covers acute and chronic respiratory failure, unspecified. When a combination code exists that captures both the acute and chronic components, it should be used rather than reporting two separate codes. Coders should always check for available combination codes before assigning multiple codes.
- A coder encounters the ICD-10-CM instructional note "Use additional code, if applicable, to identify." What does this instruction require?
Answer: The additional code is reported only when the condition or factor is present and documented
The instruction "Use additional code, if applicable" means the secondary code is reported only when the stated condition is present and documented in the medical record. It is not a mandatory requirement unless the condition exists. This contrasts with "Code first" instructions, which are mandatory sequencing requirements when both conditions are present.
- A patient receives outpatient radiation therapy for primary lung cancer. Which is the correct first-listed diagnosis for this encounter?
Answer: Encounter for radiation therapy (Z51.0)
Per ICD-10-CM Official Guidelines, when a patient is admitted or seen for the sole purpose of receiving radiation therapy, Z51.0 (encounter for antineoplastic radiation therapy) is sequenced as the first-listed diagnosis. The malignancy being treated is reported as a secondary diagnosis. This is analogous to the chemotherapy encounter sequencing rule.
