In OLIF25 and OLIF51 approaches, the patient is positioned laterally and the peritoneal contents move anteriorly and contralaterally with gravity. A surgeon’s gloved fingers or blunt instruments are used to access the retroperitoneal space.
A finger or blunt instrument can protect the peritoneum as lighted retractors are placed.
The ureter is located anterior to the psoas and close to the posterior aspect of the peritoneum. It is usually attached by a small adventitial layer to the posterior wall of the peritoneum and will be swept forward along with peritoneum during an OLIF25 and OLIF51 approach. Risk of injury can be minimized by visualizing and protecting the ureter and peritoneum with a lighted retractor.
The location of the kidneys should be evaluated preoperatively with an axial MRI. In some patients, the kidneys are found in an unusual position (below the L2 vertebrae) as seen following a kidney transplant. In such patients, this could also alter the course of the ureter.