ICD-10 Code for Mycotic Aneurysm
The ICD-10 code for mycotic aneurysm is I72.9 (aneurysm of unspecified site) or more specifically I77.0 (arteriovenous fistula, acquired), though the most accurate coding depends on the anatomic location and whether the aneurysm is ruptured or intact.
Anatomic Location-Specific Coding
The ICD-10 coding system requires specification by anatomic site for mycotic aneurysms:
Intracranial Mycotic Aneurysms
- I67.1 - Cerebral aneurysm, nonruptured
- I60.x - Nontraumatic subarachnoid hemorrhage (if ruptured)
- Intracranial mycotic aneurysms represent 0.7% to 6.5% of all intracranial aneurysms and are most commonly located in the middle cerebral artery (44% of cases) 1, 2
Thoracic and Abdominal Aortic Mycotic Aneurysms
- I71.2 - Thoracic aortic aneurysm, without rupture
- I71.1 - Thoracic aortic aneurysm, ruptured
- I71.4 - Abdominal aortic aneurysm, without rupture
- I71.3 - Abdominal aortic aneurysm, ruptured
- Aortic mycotic aneurysms account for 30-40% of all mycotic aneurysms, with infrarenal location representing 15-25% and suprarenal location 5-15% 1
Peripheral Mycotic Aneurysms
- I72.3 - Aneurysm of iliac artery
- I72.4 - Aneurysm of artery of lower extremity
- I72.1 - Aneurysm of artery of upper extremity
- Peripheral mycotic aneurysms occur in approximately 1.9% of infective endocarditis cases 3
Critical Coding Considerations
Distinguish from Syphilitic Aneurysms
- A52.01 should be used for syphilitic aneurysms, which are pathophysiologically distinct from acute mycotic aneurysms despite historical nomenclature confusion 4
- Syphilitic aneurysms develop 10-25 years after initial infection and predominantly affect the ascending thoracic aorta as fusiform aneurysms, unlike the saccular, irregular morphology of mycotic aneurysms 4
Additional Codes for Associated Conditions
- I33.0 - Acute and subacute infective endocarditis (present in many mycotic aneurysm cases) 3
- B95-B97 - Bacterial and viral infectious agents (to specify causative organism when known)
- Common organisms include Staphylococcus aureus, Salmonella species, Streptococcus pneumoniae, and Pseudomonas aeruginosa 5, 6
Documentation Requirements for Accurate Coding
To ensure proper ICD-10 code assignment, clinical documentation must specify:
- Exact anatomic location (intracranial, thoracic aorta, abdominal aorta, peripheral vessel) 1
- Rupture status (intact, contained rupture, or free rupture) - critical as rupture carries 85% mortality in some series 6
- Associated infectious etiology when identified through blood cultures (positive in 50-90% of cases) or tissue cultures 1
- Imaging characteristics including saccular morphology, periaortic soft tissue stranding, absence of calcification, and rapid enlargement on serial imaging 1
Common Coding Pitfalls
- Avoid using I72.9 (aneurysm of unspecified site) when the anatomic location is documented, as this represents incomplete coding 1
- Do not confuse with atherosclerotic aneurysms - mycotic aneurysms typically show lobular/irregular/saccular shape, minimal calcification, and periaortic inflammatory changes on CT imaging 1
- Remember to code complications separately including hemorrhage, septic emboli (present in higher frequency with mycotic aneurysms), and multiple embolisms 3