Circulatory, pregnancy, and injury-related coding
Coding for the circulatory system
Providers use a wide variety of terms and phrases to identify components of the circulatory system. To code disorders of the circulatory system accurately, the coder must carefully review all inclusions, exclusions, conventions, guidelines, and instructional notations associated with each potential code selected.
Myocardial infarction
A myocardial infarction (MI) is coded as follows:
- As acute, if it is documented as such in the diagnostic statement or has a stated duration of 4 weeks (28 days) or less.
- As old or healed, if the MI is more than 4 weeks old and the patient has no current symptoms related to it.
Other MI coding considerations include the following:
- If an MI is specified as “old” or “healed” without any current or presenting symptoms, it is coded I25.2 Old myocardial infarction, not to category I21 - category I21 is reserved for an MI that is still acute.
- A history of an MI also uses code I25.2 Old myocardial infarction. This code is used when the old MI was diagnosed by ECG or other investigation and the patient currently has no symptoms.
- If the patient has a current, symptomatic acute MI and the site of the infarction is not documented, assign I21.3 ST elevation (STEMI) myocardial infarction of unspecified site.
Hypertensive disease
A distinction is made in the ICD-10-CM between “elevated” and “high” blood pressure. High blood pressure is defined as hypertension [I10 Essential (primary) hypertension]. If a diagnostic statement does not contain the word hypertension or the phrase high blood pressure, the condition is coded as elevated blood pressure [R03.0 Elevated blood-pressure reading, without diagnosis of hypertension], not hypertension.
Hypertension frequently is the cause of various forms of heart and vascular disease; however, the mention of hypertension in the diagnostic statement does not mean that a combination code for hypertensive heart disease should be used. If a cause-and-effect relationship exists between hypertension and heart disease, it should be clearly documented in the clinical record or diagnostic statement.
The hypertension table in the ICD-9-CM was not included in the ICD-10-CM. Heart conditions classified to category I50 Heart failure or subcategories I51.4-I51.9 are assigned to a code from category I11 Hypertensive heart disease when a causal relationship is stated in the health record (“as a result of hypertension”) or implied (“hypertensive”). Use an additional code from category I50 to identify the type of heart failure in patients with heart failure.
The same heart conditions (category I50 or subcategories I51.4-I51.9) with hypertension, but without a stated causal relationship, are coded separately. The codes should sequence according to the circumstances of the admission or encounter.
Coding for chronic kidney disease
Assign codes from category I12 Hypertensive chronic kidney disease when both hypertension and a condition classifiable to category N18 Chronic kidney disease (CKD) are present. Unlike hypertension with heart disease, the ICD-10-CM presumes a cause-and-effect relationship and classifies chronic kidney disease with hypertension as hypertensive chronic kidney disease.
The appropriate code from category N18 should be used as a secondary code with a code from category I12 to identify the stage of chronic kidney disease.
If a patient has hypertensive chronic kidney disease and acute renal failure, an additional code for acute renal failure is required.
Coding for atherosclerotic cardiovascular disease
The ICD-10-CM has combination codes for atherosclerotic heart disease with angina pectoris. The subcategories for these codes are I25.11 Atherosclerotic heart disease of native coronary artery with angina pectoris and I25.7 Atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris.
When you use one of these combination codes, you do not need to use an additional code for angina pectoris. A causal relationship can be assumed in a patient with both atherosclerosis and angina pectoris unless the documentation indicates that the angina is due to something other than atherosclerosis.
If a patient with coronary artery disease is admitted because of acute myocardial infarction (AMI), the AMI should be sequenced before the coronary artery disease.
Coding for skin ulcers
Codes from category L89 Pressure ulcer are combination codes that identify the site of the pressure ulcer and the stage of the ulcer. The ICD-10-CM classifies pressure ulcer stages based on severity, which is designated by stages 1 to 4; unspecified stage; or unstageable. Unspecified and unstageable codes are used for pressure ulcers when the stage cannot be clinically determined (e.g., the ulcer has been treated with a skin or muscle graft). These codes are also used for pressure ulcers documented as deep tissue injuries, but not documented as being due to trauma. The modifying term defines each stage, depending on the location of the ulcer.
Coding for complications of pregnancy, childbirth, and the puerperium
Coding for the obstetric patient is like using a specialty codebook within the ICD-10-CM coding manual. This is challenging for coders who do not code obstetrics often. Here are some important clinical terms regarding pregnancy:
- antepartum: Pregnancy (applies as soon as a pregnancy test result is positive)
- childbirth: Delivery
- postpartum: The puerperium, or first 6 weeks after delivery
- peripartum: The period from the last month of pregnancy to 5 months postpartum
Obstetrics cases use codes from Chapter 15, Pregnancy, Childbirth, and the Puerperium (O00-O9A). Additional codes from other chapters may be used in conjunction with Chapter 15 codes to further specify conditions.
If the provider documents that the pregnancy is incidental to the encounter, code Z33.1 Pregnant state, incidental should be used instead of any Chapter 15 codes. This would be the case if the patient were being seen for a sprained ankle. The sprained ankle is not related to the pregnancy but is an incidental diagnosis. It is the provider’s responsibility to state that the condition being treated is not affecting the pregnancy. Codes from Chapter 15 are documented only in the maternal health record; they are never used in the health record of the newborn.
Most of the codes in Chapter 15 have a character (the final character before any seventh-character extension) that indicates the trimester of pregnancy. Assignment of the final character for the trimester should be based on the provider’s documentation of the trimester (or number of weeks) for the encounter. This applies to the assignment of trimester for preexisting conditions, in addition to those that develop during or are due to the pregnancy. The provider’s documentation of the number of weeks may be used to assign the appropriate code identifying the trimester. The seventh character in this chapter is used to identify the fetus when there is more than one.
Outcome of delivery and liveborn infant codes
When a delivery occurs, the principal diagnosis should correspond to the main circumstances or complications of the delivery. In cases of cesarean delivery, the selection of the principal diagnosis should be the condition assigned after the encounter that was responsible for the patient’s admission. If the patient was admitted with a condition that resulted in the performance of a cesarean procedure, that condition should be selected as the principal diagnosis. If the reason for the admission was unrelated to the condition resulting in the cesarean delivery, the condition related to the reason for the admission/encounter should be selected as the principal diagnosis.
For example, a maternity patient was admitted to the hospital for pneumonia, but because of complications, a cesarean section was performed. In this case, the pneumonia would be the primary diagnosis. A code from category Z37 Outcome of delivery should always be included in the maternal health record when a delivery has occurred.
Code O80 Encounter for full-term uncomplicated delivery should be assigned when a woman is admitted for a full-term vaginal delivery and delivers a single, healthy infant without any complications antepartum, during the delivery, or postpartum during the delivery episode. Code O80 is always a principal diagnosis.
Newborn coding
Chapter 16, Certain Conditions Originating in the Perinatal Period (P00-P96), also is used for coding and reporting purposes. The perinatal period extends from just before the birth through day 28 after the birth. When you code the birth episode in a newborn’s health record, assign a code from category Z38 Liveborn infants according to place of birth and type of delivery as the principal diagnosis. A code from category Z38 is assigned only once to a newborn at the time of birth. Codes from categories Z37 and Z38 are never used in the newborn’s own health record or in any subsequent record after the initial birth episode - for example, if a newborn is transferred to another institution, the receiving hospital does not assign a Z38 code. When a newborn is admitted to another hospital, the newborn’s admitting diagnosis is the health condition that requires the hospital transfer.