Patients with peritonitis had a lower level of S1P than that of patients without peritonitis (1.3 ng/mL IQ 0.8, 3.6 ng/mL vs. 2.8 ng/mL IQ1.5, 5.4 ng/mL, p = 0.018) (Figure 1). Here, MBTPS1 is linked to peritonitis.