The horseshoe kidney (HK) is a congenital anomaly in which the kidneys are fused in front of the anterior aortic wall in its most common form. The association of abdominal aortic aneurysm (AAA) and horseshoe kidney (HK) is a rare and challenging condition, occurring in less than 0.2% of all AAA cases. In these cases, open surgery is still widely practiced in many centers, with either a transperitoneal or retroperitoneal approach. Typically, several polar arteries arise from the distal abdominal aorta or the iliac arteries to perfuse the HK.

A key consideration for the surgery is whether or not to preserve the vascularization of the variant kidney. Preserving them can be challenging, but removing them can lead to a significant reduction in renal volume and subsequent loss of function. In open surgery repair, it is recommended to reanastomose as many arteries as possible to the prosthesis, even though this introduces additional technical challenges, especially in emergency situations. Computed Tomography Angiography (CTA) is the best diagnostic test for performing a preoperative vascular assessment.

The purpose of the present study is to develop a semi-automated model on preoperative CCTA to measure the volume of parenchyma perfused by each artery to determine whether or not these should be preserved. The model will be validated on post-surgical CCTA in patients with HK treated for AAA.

Customized use of this tool could be a valuable method in surgical decision making, determining which arteries can be made safe during surgery and addressing a rare but complex clinical need.

Inclusion Criteria:

• Adult subjects (≥18 years old) surgically treated for AAA with HK at San Raffaele Hospital between January 2019 and December 2023, with appropriate pre- and postoperative CTA, pre- and post CT.

Exclusion Criteria:

• Pediatric patients (age <18 years)
• Absence of pre- and postoperative CT images
• Performance of surgery other than open surgery.

All consecutive patients surgically treated for AAA with HK at San Raffaele Hospital between January 2019 and December 2023, with appropriate pre- and post-operative CTA