Background: Staged lavage was first introduced in the 1970s and now serves as a therapeutic option for septic patients with peritonitis. A central aspect of this treatment concept is leaving the abdomen open after a wide incision. To evaluate the influence of transverse vs. median access to the abdomen in staged lavage, data from the authors' patients were analyzed. Methods: To evaluate patients with peritonitis, prospective intensive care data were examined together with data on the surgical details. The main aspects covered here were the surgical details of the lavage (namely, transverse vs. median laparotomy), number of lavages, fascia closure, wound-healing disorders, and observed lethality, in combination with the preoperatively evaluated SAPS-II score, expected hospital lethality, patient age, and the Mannheim Peritonitis Index. Results: Between January 2008 and December 2018, 522 patients were treated with open abdomen and staged lavage. The mean age of the patients was 66.0 years (standard deviation (SD) 15.9 years). A median incision was used in 140 cases, and transverse laparotomy was performed in 382. The mean SAPS-II score was 46.5 (SD 15.7), expected lethality was 39.6% (SD 26.3%), and observed lethality was 19.9%. On average, two lavages were performed after the index operation. Transverse incision was significantly less likely to cause wound-healing disorder (p=0.03), and fascial dehiscence was observed less frequently in the transverse laparotomies group than in median incisions in the statistical trend (p=0.06). Conclusion: In summary, staged lavage reduced expected lethality in patients with peritonitis. Transverse incision caused wound-healing disorders and fascial dehiscence less often. Therefore, the indication for transverse laparotomy should be generous, as this form of treatment is advantageous in case of peritonitis.