After adjusting for sex, age, source of peritonitis, and APACHE II score in the logistic regression models, only the NOS3 c.-786T>C TT genotype remained significantly associated with a higher likelihood of developing MOF (p = 0.006, OR = 4.86, 95% CI = 1.56–15.13) and MODS (p = 0.047, OR = 3.67, 95% CI = 1.02–13.19). Here, NOS3 is linked to peritonitis.