When performing a dual-incision technique, the lateral incision is marked at the same location as above. A second incision is made posterior to this first mark at the lateral border the erector spinae muscles. Alternative blunt scissor and finger dissections are used to open the corridor through the abdominal muscles and fascia. This step should be made with caution to avoid inadvertent violation of the peritoneum. Once in the retroperitoneum, the index finger is used to sweep the peritoneum anteriorly and then to palpate the transverse process and the psoas muscle. Then, the finger dissection is continued upward and toward the lateral mark. A skin and fascial incision is made at this location, and the initial dilator is introduced. The index finger, which is in the retroperitoneal space through the posterior incision, is used to escort the initial dilator down to the psoas muscle (Fig. 13.2).