In a retroperitoneal infection, which artery is most likely to be affected?

Renal Artery is Most Likely Affected in Retroperitoneal Infections

In retroperitoneal infections, the renal artery is most commonly affected due to its anatomical location and the frequent involvement of perirenal tissues in retroperitoneal pathologies. 1

Anatomical Basis and Evidence

Retroperitoneal infections commonly involve the perinephric space, leading to what's described as a "hairy kidney" appearance on imaging. This infiltrative perinephric soft tissue thickening is seen in 50-60% of cases 1. The infiltration can extend to involve:

• The renal pelvis
• Renal ureters (potentially causing hydronephrosis)
• Renal vessels

The periarterial involvement of renal vessels is particularly significant because:

1. Perinephric infiltrates can extend to involve the renal artery adventitia 1
2. This periarterial fibrosis can lead to renal artery stenosis 1
3. The resulting stenosis often causes resistant hypertension in affected patients 1

Clinical Implications of Renal Artery Involvement

When retroperitoneal infections affect the renal artery, several important clinical consequences may occur:

• Renovascular hypertension: Occurs in approximately 20% of patients with periarterial involvement of renal vessels 1
• Renal function impairment: Can progress to requiring dialysis in severe cases
• Need for intervention: Renal artery stenosis from periarterial fibrosis often responds well to endovascular stenting 1

Pathophysiology

The mechanism of arterial involvement in retroperitoneal infections follows several patterns:

1. Direct extension: Infection from the retroperitoneal space extends to involve the arterial adventitia
2. Inflammatory response: The inflammatory process leads to fibrosis around the vessel
3. Circumferential thickening: Most commonly described pattern of arterial involvement 1

Differential Considerations

While the renal artery is most commonly affected, other arteries can also be involved in retroperitoneal infections:

• Abdominal aorta: Often involved in mycotic aneurysms, but these typically affect the suprarenal portion rather than being primarily retroperitoneal in origin 1
• Superior mesenteric artery: Rarely involved in retroperitoneal infections, though it can be affected in visceral mycotic aneurysms 1
• Celiac artery: Can be involved in periarterial fibrosis but less commonly than renal arteries 1

Diagnostic Approach

CT with IV contrast or CT angiography is the preferred imaging modality for evaluating retroperitoneal infections and associated vascular involvement 2. These studies can detect:

• Periarterial thickening
• Arterial stenosis
• Active bleeding if present
• Extent of retroperitoneal involvement

Management Considerations

When renal artery involvement is detected in retroperitoneal infections:

• Monitor for renovascular hypertension
• Consider endovascular stenting for significant stenosis 1
• Address the underlying infectious process with appropriate antibiotics and drainage if needed
• Follow up imaging to assess response to treatment

Conclusion

The renal artery is the most commonly affected artery in retroperitoneal infections due to the frequent involvement of perinephric tissues and the anatomical relationship between the kidneys and the retroperitoneal space. This involvement can lead to significant clinical consequences including renovascular hypertension and may require specific interventions such as endovascular stenting.