Aneurysm is an abnormal, focal outward bulging or dilation of a blood vessel wall — most commonly an artery — resulting from a structural weakness or thinning of the tunica media (the middle muscular layer of the vessel wall). Unlike atherosclerosis, which involves plaque buildup causing narrowing (stenosis), an aneurysm represents expansion of the lumen; it should also be distinguished from dissection, in which blood forces between the vessel wall layers without true ballooning. The underlying mechanism involves degradation of elastin and collagen in the medial layer, often driven by hemodynamic stress, chronic hypertension, connective tissue disorders (e.g., Marfan syndrome, Ehlers-Danlos syndrome), or inflammatory/infectious processes (mycotic aneurysm). Aneurysms may be physiologically incidental (small, stable, discovered incidentally on imaging) or pathologically dangerous (rapidly enlarging or ruptured), with rupture leading to life-threatening hemorrhage — particularly subarachnoid hemorrhage in cerebral aneurysms (I60.7) or hemorrhagic shock in aortic rupture. The most clinically relevant subtypes for coding include: aortic aneurysms (thoracic I71.20-I71.23, abdominal I71.40-I71.43, thoracoabdominal I71.60-I71.62), cerebral aneurysm nonruptured (I67.1), coronary artery aneurysm (I25.41), pulmonary artery aneurysm (I28.1), and other peripheral arterial aneurysms (I72.0-I72.9**). Aneurysm is commonly confused with pseudoaneurysm (false aneurysm) — a key distinction: a true aneurysm involves all three vessel wall layers, while a pseudoaneurysm is a contained rupture where blood pools outside the vessel wall, contained only by surrounding tissue.
Greek εὐρύς (eurús), from PIE *wer- (“wide, broad”)
“wide,” “broad,” “spacious”
-isma / -ysm
Greek -ισμα (-isma) / -υσμα (-usma)
Noun-forming suffix — “result of an action,” “condition produced by”
The word entered English in the early 1400s (early 15c.) as aneurysm (noun), from Medieval Latin aneurisma, from Greek ἀνεύρυσμα (aneúrusma) — “a widening, a dilation” — from the verb ἀνευρύνειν (aneurúnein), “to widen out,” literally “to widen up/open wide.” The adjectival form aneurysmal emerged in the 18th-19th centuries in clinical literature. The root eurys (“wide”) connects aneurysm to the broader eury- root family: euryopia (eury- + -opia → wide field of vision), eurythermal (eury- + thermal → tolerating wide temperature range), and Eurasia (eury- + Asia → “the wide continent”). The prefix ana- is highly productive in medical terminology, appearing in anatomy, anaphylaxis, anastomosis, and anabolism.
🔀 ALIASES / ALTERNATE TERMS
Aneurysmal(adjective form — seen in clinical collocations: “aneurysmal dilation,” “aneurysmal subarachnoid hemorrhage,” “aneurysmal bone cyst”)
Aneurysmic(less common adjective form; used interchangeably with aneurysmal in some radiology and vascular surgery reports)
Berry aneurysm(small, round saccular aneurysm — the most common type of cerebral aneurysm; classic cause of non-traumatic subarachnoid hemorrhage; coded I67.1 when nonruptured, I60.7 when ruptured)
Saccular aneurysm(spherical, asymmetric outpouching involving only one side of the vessel wall; most common in cerebral circulation — coded under I67.1 or aortic subcategories depending on site)
Fusiform aneurysm(circumferential, spindle-shaped dilation involving the entire circumference of the vessel wall; more common in aorta and vertebrobasilar system)
Pseudoaneurysm | False aneurysm (pseudoaneurysm)(contained rupture of the vessel wall with hematoma formation — NOT a true aneurysm; classified under I72.0-I72.9 or traumatic vascular injury codes depending on etiology)
Mycotic aneurysm(infectious/inflammatory etiology — misnomer, not always fungal; caused by septic emboli seeding vessel wall; requires code for underlying infection sequenced first)
Dissecting aneurysm(blood enters and tracks through vessel wall layers — now more precisely called aortic dissection and coded I71.0x; distinct from true aneurysm)
AAA (Abdominal Aortic Aneurysm)(dilation of the infrarenal aorta ≥3 cm; leading cause of vascular surgery emergencies; coded I71.40-I71.43 without rupture, I71.30-I71.33 with rupture)
Intracranial aneurysm(includes all aneurysms within the skull — saccular, fusiform, or giant; nonruptured coded I67.1; ruptured cerebral coded I60.7)
Giant aneurysm(cerebral aneurysm >25 mm diameter; higher rupture risk; coded I67.1 if nonruptured — no separate ICD-10-CM code for size specificity)
Coronary artery aneurysm(dilation of a coronary artery, often post-Kawasaki disease or atherosclerosis; coded I25.41 — note: I25.4 is the parent/non-billable header)
🔗 RELATED TERMS
Stenosis — the opposite of aneurysmal dilation; abnormal narrowing of a vessel lumen due to plaque, fibrosis, or spasm — reduces blood flow distally rather than expanding the vessel
Dissection — shares the aorta/artery anatomic site; involves blood forcing between vessel wall layers (intima and media) without a true sac; coded separately under I71.0x (aortic) or I67.0 (cerebral)
Atherosclerosis — major risk factor and frequent underlying cause of aortic and peripheral aneurysms; involves intimal plaque formation weakening the medial layer over time
Subarachnoid hemorrhage — most feared complication of ruptured cerebral aneurysm; coded I60.7 (nontraumatic SAH from ruptured cerebral aneurysm); hemorrhage fills the subarachnoid space
Marfan syndrome — inherited connective tissue disorder (FBN1 gene mutation) causing defective fibrillin → weakened aortic media → high risk of aortic root aneurysm and dissection (Q87.410)
Pseudoaneurysm — false aneurysm; involves only the adventitia or surrounding hematoma rather than all three vessel layers; commonly post-procedural (femoral access site) or traumatic
Thrombosis — frequent secondary complication within aneurysm sac; sluggish flow promotes mural thrombus formation → risk of distal embolization
Embolization — thrombus from an aneurysm sac may dislodge and occlude downstream vessels (e.g., renal, mesenteric, lower extremity arteries)
Kawasaki disease — inflammatory vasculitis causing coronary artery aneurysms in children (M30.3); most common acquired cause of coronary aneurysm in pediatric patients
Ehlers-Danlos syndrome — connective tissue disorder affecting collagen synthesis; vascular type (hEDS) associated with spontaneous arterial rupture and aneurysm formation
CT angiography (CTA) — primary diagnostic imaging modality for detecting, sizing, and monitoring aortic and peripheral aneurysms; guides surgical vs. surveillance decision-making
Endovascular repair (EVAR/TEVAR) — minimally invasive stent-graft deployment for aneurysm exclusion; standard of care for elective infrarenal AAA
CODING CORNER
🏥 ICD-10-CM CODES
Aortic Aneurysm (I71.xx — Site and Rupture Status Required)
Code
Description
I71.010
Dissection of ascending aorta
I71.011
Dissection of aortic arch
I71.012
Dissection of descending thoracic aorta
I71.019
Dissection of thoracic aorta, unspecified
I71.10
Thoracic aortic aneurysm, ruptured, unspecified
I71.11
Aneurysm of the ascending aorta, ruptured
I71.12
Aneurysm of the aortic arch, ruptured
I71.13
Aneurysm of the descending thoracic aorta, ruptured
I71.20
Thoracic aortic aneurysm, without rupture, unspecified
I71.21
Aneurysm of the ascending aorta, without rupture
I71.22
Aneurysm of the aortic arch, without rupture
I71.23
Aneurysm of the descending thoracic aorta, without rupture
I71.30
Abdominal aortic aneurysm, ruptured, unspecified
I71.31
Pararenal abdominal aortic aneurysm, ruptured
I71.32
Juxtarenal abdominal aortic aneurysm, ruptured
I71.33
Infrarenal abdominal aortic aneurysm, ruptured
I71.40
Abdominal aortic aneurysm, without rupture, unspecified
I71.41
Pararenal abdominal aortic aneurysm, without rupture
I71.42
Juxtarenal abdominal aortic aneurysm, without rupture
I71.43
Infrarenal abdominal aortic aneurysm, without rupture
Nontraumatic subarachnoid hemorrhage from unspecified intracranial aneurysm (ruptured cerebral aneurysm)
Coronary & Cardiac Aneurysm
Code
Description
I25.41
Coronary artery aneurysm
I25.3
Aneurysm of heart (ventricular aneurysm)
Pulmonary Aneurysm
Code
Description
I28.1
Aneurysm of pulmonary artery
Peripheral Arterial Aneurysm (I72.xx — Site Specificity Required)
Code
Description
I72.0
Aneurysm of carotid artery
I72.1
Aneurysm of artery of upper extremity
I72.2
Aneurysm of renal artery
I72.3
Aneurysm of iliac artery
I72.4
Aneurysm of artery of lower extremity
I72.5
Aneurysm of other precerebral arteries (includes basilar, vertebral)
I72.6
Aneurysm of vertebral artery
I72.8
Aneurysm of other specified arteries
I72.9
Aneurysm of unspecified site
Syphilitic Aneurysm (Code First Syphilis)
Code
Description
A52.01
Syphilitic aneurysm of aorta — code first when syphilis is the documented etiology
🔧 COMMON CPT CODES (Aneurysm-Related Diagnosis & Treatment)
CPT Code
Description
61700
Surgery of simple intracranial aneurysm, intracranial approach; carotid circulation
61702
Surgery of intracranial aneurysm, intracranial approach; carotid circulation (complex/giant)
61703
Surgery of intracranial aneurysm, intracranial approach; vertebrobasilar circulation
61710
Surgery of intracranial aneurysm, intracranial approach; by flow-directed technique (e.g., balloon)
35081
Direct repair of aneurysm, open; abdominal aorta (infrarenal)
35082
Direct repair of ruptured abdominal aortic aneurysm, open
35091
Direct repair of aneurysm, open; abdominal aorta involving visceral vessels (mesenteric/renal)
35102
Direct repair of aneurysm, open; abdominal aorta involving iliac arteries (aorto-iliac)
34701
Endovascular repair of infrarenal aorta (EVAR), including unilateral iliac artery, with deployment of aorto-aortic tube endograft
34702
EVAR of infrarenal aorta; for rupture including temporary aortic/iliac balloon occlusion, when performed
34703
Endovascular repair of infrarenal aorta with deployment of aorto-uni-iliac endograft
34704
EVAR with aorto-uni-iliac endograft; for rupture
34705
Endovascular repair of infrarenal aorta with deployment of aorto-bi-iliac endograft
34706
EVAR with aorto-bi-iliac endograft; for rupture
35001
Direct repair of aneurysm; carotid or subclavian artery, by neck incision
93978
Duplex scan of aorta, iliac vasculature, or bypass grafts; complete study (surveillance imaging for AAA)
⚠️ Coding Note: Aortic aneurysm codes under I71 require site AND rupture status specificity — unspecified codes (e.g., I71.40, I71.9) should be queried when documentation supports a more specific subsite (ascending, arch, descending, infrarenal, juxtarenal, etc.), as payers increasingly scrutinize unspecified codes on inpatient claims. For sequencing, when an aneurysm is the reason for surgery or admission, it is sequenced as the principal diagnosis; if syphilis or another underlying etiology is documented, that condition must be sequenced first per instructional notes (e.g., A52.01 before the aortic aneurysm code). A high-yield undercoding alert for inpatient profee: ruptured AAA — documentation of “abdominal aortic aneurysm” without explicit “ruptured” or “without rupture” defaults to unspecified (I71.40 range), potentially missing the rupture code (I71.30-I71.33) — query the provider when operative notes reference hemorrhage, hematoma, or emergent repair. For cerebral aneurysms, note that I67.1 captures nonruptured aneurysm only — a ruptured cerebral aneurysm with subarachnoid hemorrhage is coded to I60.7, not I67.1; this is a common sequencing error on neurosurgery inpatient claims. CPT codes for intracranial aneurysm repair (61700, 61702, 61703) have a 90-day global period — post-op visits within 90 days are included; modifier -24 or --79 is required for unrelated E/M or procedures within that global window.
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