Poster Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Introduction: With the increasing application of OLIF surgery, how to reduce intraoperative complications is becoming important. During the approach for OLIF surgery, the presence of the retrorenal colon is often encountered. Colon injury is one of the complications associated with OLIF surgery. A thorough understanding of its incidence and risk factors before surgery can help reduce the probability of colon injury during OLIF procedures.

Methods:  A retrospective analysis was conducted on the clinical data of patients who underwent OLIF surgery at Sir Runrun Shaw hospital from January 2022 to July 2024. The retrorenal colon was diagnosed as being located posterior to the retro-kidney line, while the postero-lateral colon was diagnosed as being located between the retro-kidney line and the mid-kidney line. This study involved 238 patients, including 96 males and 142 females, aged 27 to 85 years, with an average age of 64 years. Patients were divided into two groups by age: ≤65 years and ＞65 years; and into two groups by body mass index (BMI): ≤24 kg/m² and ＞24 kg/m². The Cobb angle of lumbar curvature was measured on lumbar X-rays, and patients were categorized into ≤25 degrees and ＞25 degrees groups based on the Cobb angle. The incidence of retrorenal colon and postero-lateral colon was analyzed based on different age, gender, and BMI groupings. Multivariate logistic regression analysis was performed to assess the associated risk factors for retrorenal colon and postero-lateral colon.

Results:  Among the 238 patients, 7 (2.9%) were confirmed to have retrorenal colon including 1 male and 6 females. Sixty-two patients (26.05%) were confirmed to have postero-lateral colon, with 45 females and 17 males. The average age of the retrorenal colon and postero-lateral colon group was 67.09±8.41 years, while the control group was 63.14±9.26 years. The incidence in patients over 65 years old was higher than that in patients aged 65 years or younger. The incidence in patients with BMI ≤24 was higher than that in patients with BMI >24. Among patients with a Cobb angle >25 degrees, the incidence of retrorenal colon and postero-lateral colon was higher than that in those with a Cobb angle ≤25 degrees. The results of the multivariate logistic regression analysis showed that the incidence of retrorenal colon and postero-lateral colon was associated with gender, age, BMI, and Cobb angle.

Discussion: The incidence of retrorenal colon and postero-lateral colon in patients undergoing OLIF surgery is 29%. Low body weight, advanced age, and spinal scoliosis are risk factors for the occurrence of retrorenal colon and postero-lateral colon. For patients with BMI ≤24, age >65 years, and Cobb angle ＞25 degrees undergoing lateral lumbar fusion surgery, preoperative CT examination should be performed to confirm the presence of retrorenal colon and postero-lateral colon.