External iliac artery endofibrosis (EIAE) is an uncommon disease that affects a large number of athletes. The pathogenesis of EIAE is unclear. We offer an additional possible cause, with a direct relationship between EIAE and psoas muscle hypertrophy.

Objective: Avid competition bicycling may be associated with the development of external iliac artery stenosis. European studies have documented endofibrosis that primarily has affected young men. Our objective was to review the histopathologic features of obstructed external iliac arteries resected from avid competition bicyclists at a single institution. 

Method: Medical records and microscopic slides were reviewed from all competitive bicyclists who had undergone resection and graft placement for segmental external iliac artery disease at Mayo Clinic (Rochester, Minn) between 1991 and 2001. 

Results: Of seven patients (five female, two male) seen with external iliac obstructive disease, four underwent resection and graft placement and thus had specimens available for histopathologic review. Ages of these four patients, all of whom were women, ranged from 31-40 years (mean, 36 years). Claudication was the primary symptom in all four women. There were five iliac arteries involved in the four women, and pre-operative arteriography showed stenotic disease in these arteries, ranging from subtle stenosis to occlusion. Gross examination of the five resected arteries showed wall thickening and luminal narrowing, without aneurysm formation. Microscopically, luminal thrombus was observed in two arteries (one old and one recent). Intimal thickening affected four specimens (symmetric in three and asymmetric in one). Thickening was the result of smooth muscle hyperplasia, with only mild collagen or elastin deposition. Medial hypertrophy was present in three specimens (symmetric in two and asymmetric in one), one of which also contained focal calcification. Adventitial thickening was prominent in four (symmetric in two and asymmetric in two) and was due to smooth muscle hyperplasia. There was no intimal, medial, or adventitial inflammation. 

Conclusions: In contrast to previous reports, iliac arteriopathy among competition bicyclists may occur in women. The microscopic lesions responsible for stenosis are more varied than the “endofibrosis” that has been previously documented. In addition to the intimal fibrosis and luminal thrombosis noted by others, we describe medial and adventitial responses to repetitive trauma. Accordingly, we favor the term “external iliac arteriopathy” for this disease entity.

External iliac stenosis due to endofibrosis is a rare condition that predominantly affects top level cyclists. Short term symptomatic relief is reported in an Olympian after percutaneous transluminal angioplasty, which was performed to allow the patient to return to training without delay.