Abstract: Objective To explore the topography and anatomical nature of the retroperitoneal fascia and fascial space in laparoscopic left colectomy，right colectomy，or nephrectomy and to set up methodologies to identify surgical planes. Methods Five unembalmed adult cadavers were observed laparoscopically. In addition, totally 30 patients undergoing laparoscopic left or right colectomy，as well as 95 patients undergoing laparoscopic nephrectomy were observed on the fusion fascia and fusion fascial space with reference to location，distribution and topography. Results Between the visceral and parietal peritoneum, lateral to the ascending or the descending colon，there was a yellowwhite borderline，along which cutting into the peritoneum and extraperitoneal tissue unveiled the fusion fascia. The fusion fascia and prerenal fascia enclosed a fusion fascia space full of loose connective tissue. Dissection along the fusion fascial space easily mobilized the ascending and descending colon and their primitive mesocolon， and also unveiled the prerenal fascia posteriorly. The anterior pararenal spaces were delineated by the prerenal fascia，the lateroconal fascia and the lateral extension of the fusion fascia，and the posterior pararenal space by the posterior layer of renal faascia，the lateroconal fascia and the lumbar quadrate muscular fascia. Mobilization of the kidney was also achieved by dissecting into the anterior and the posterior pararenal spaces to the renal hilum. Conclusion The yellowwhite borderlines can be regarded as landmarks to access the

Key words: Retroperitoneal fascia space, Surgical plane, Laparoscopy, Human