Renal Artery Variants in Patients with Normal Renal Function

3D volume rendered CT image shows a 2nd right renal artery (arrows) arising from the right common iliac artery

Facts

• "Normal" renal arterial arrangement = single bilateral renal arteries with hilar segmental branching. This occurred in 46% of cases in a landmark angiographic report published in 1978
• Normally, no intrarenal arterial anastomoses are present. Each artery represents an end artery -- interruption results in infarction of that segment
• Variations include double renal arteries, triple renal arteries, pre-hilar segmental branching, fetal lobulation and exaggerated size difference (greater than 2 cm). 
• Most common variations are multiple renal arteries followed by pre-hilar segmental branching

Knowledge of Renal Vascular Variations is Important For:

• Renal transplantation
• Renovascular hypertension
• Vascular reconstruction for congenital and acquired lesions
• Reconstructive surgery for abdominal aortic aneurysms

Our case: Double right renal artery with the smaller branch originating from the common iliac artery

Reference:

- Harrison, Jr., et al. Incidence of anatomical variants in renal vasculature in the presence of normal renal function. Ann Surg 1978;188:83-89.

- Ozkan U, et al. Renal artery origins and variations: angiographic evaluation of 855 consecutive patients. Diagn Interv Radiol 2006;12:183-6.

Vertebral Artery Hypoplasia

Curved reformat of the normal-caliber right vertebral artery showing all 4 segments of the artery. 

Curved reformat of the left vertebral artery shows diffuse, small caliber of the artery.

Facts:

• Operational definitions are either 1) asymmetrical ratio of or greater than 1:1.7, or 2) discrepancy of greater than 2 mm diameter
• Prevalence 2%-6% of population (from autopsy and angiographic series)

Clinical Relevance

• Posterior circulation ischemia: hypoplasia leads to reduction of posterior circulation blood flow velocity therefore has a negative role in occlusion of major cerebral arteries
• Migraine with aura and vestibular neuronitis: hypoplasia is believed to be associated with regional hypo perfusion and complex neurovascular consequences

Reference:

Chuang YM, Chan L, Wu HM, et al. The clinical relevance of vertebral artery hypoplasia. Acta Neurol Taiwan 2012;21:1-7.