【Abstract】ObjectiveTo evaluate the main CT features, the morbidity of CT signs and the anatomic-pathologic bases of secondary pyogenic peritonitis (SPP). MethodsTwentyfour patients of the SPP were retrospectively studied. Emphasis was placed on the spiral CT manifestations of the SPP correlating with their anatomic-pathologic bases and the occurrence as well as the signs of primary lesions which resulted in the SPP. ResultsThe main CT manifestations of SPP revealed as follows: the thickened peritoneum, 16 in 24 cases (66.7%), of which 14 cases were smooth and 2 cases were irregular; the ascites, 15 in 24 cases (62.5%); the free air within peritoneal cavity, 9 in 24 cases (37.5%); the edema and thickening involved in the greater omentum, 8 in 24 cases (33.3%); the small bowel mesentery, 5 in 24 cases (20.8%); and the bowels’ wall, 5 in 24 cases (20.8%); the adhesions of bowels, 6 in 24 cases (25.0%). The CT manifestation of the promary lesions, which caused SPP, and the complications were shown as follows: the signs of primary lesion, 13 cases (54.2%); the inflammatory changes in retroperitoneal cavity 13 cases (54.2%); the involvements of chest 13 cases (54.2%); and the abscess in peritoneal and pelvic cavity 6 cases (25.0%). ConclusionThe main significant CT signs of SPP could be concluded as follows: thickened peritoneum, ascites, free air within peritoneal cavity, edematous and thickened greater omentum, the small bowel mesentery, and the bowels’ wall, as well as the adhesions of bowels. So, the CT scan can present plenty of CT signs, which are significant and very helpful for making an appropriate diagnosis of SPP.