This proposed study aims to extend from previous study by increasing examinee population to include all adult PD patients as a cross sectional observational study. We will utilize previously published sonographic examination method on PD patients (both B-mode and Doppler ultrasonography). We will collect the blood, urine and peritoneal effluent sample at the same time. We hope that through this large-scale survey we can elucidate more clearly the relationship between morphology and functional/transport characteristics of the parietal peritoneum during the natural course of renal replacement therapy with peritoneal dialysis. The results will form our basis of future longitudinal serial follow-ups for the adult PD patients. Besides, for those PD patients with suspected peritonitis, we will also perform non-invasive ultrasonographic examinations and collect relevant samples on the initial days of hospitalization in order to establish an "early predicting model" of severe, medical-refractory peritonitis by using transabdominal ultrasonography.