Background and Aims: Complicated intra-abdominal infection (cIAI) is the second most common infection after surgery. Despite the increasing improvement of the diagnostic and treatment techniques, the mortality rate of cIAI is still high. The cIAI developed during hospitalization not only endangers the patients’ lives, but also exerts a negative impact on their long-term prognosis. This study was conducted to investigate the risk factors for healthcare-associated cIAI (HA-cIAI) in adults, so as to provide basis for implementation of appropriate intervention measures in clinical practice, and thereby reduce the incidence of HA-cIAI. 
Methods: The clinical data of 359 adult patients whose ascitic fluid samples were collected and positive for rapid aerobic bacterial culture during hospitalization and with clinical diagnosis of cIAI from November 2011 to July 2016 in Xiangya Hospital of Central South University were retrospectively analyzed. Of the patients, 143 cases were community-acquired cIAI (CA-cIAI group) and 216 cases were HA-cIAI group (HA-cIAI group). The general conditions, treatments and laboratory indicators of the two groups of patients were compared, and the risk factors for HA-cIAI were analyzed.
Results: Compared with CA-cIAI group, the patients in HA-cIAI group showed a high proportion of cases with age ≥60, prolonged average length of hospital stay, high proportions of cases with abdominal malignancy and undergoing abdominal surgery during hospitalization, low hemoglobin and procalcitonin levels and high alamine aminotransferase level (all P<0.05). Among patients undergoing abdominal surgery during hospitalization, the proportions of the surgery duration ≥3 h, intraoperative blood loss ≥200 mL, the retention time of abdominal drainage tube ≥10 d, the indwelling urethral catheter and its retention time ≥7 d, as well as preoperative use of antibiotics in HA-cIAI group were significantly higher than those in CA-cIAI group (all P<0.05). The results of Logistic regression analysis showed that the length of hospitalization ≥15 d (OR=6.946, 95% CI=3.786–12.743, P<0.05) and abdominal malignancy (OR=2.880, 95% CI=1.538–5.390, P<0.05) were independent risk factors for HA-cIAI. 
Conclusion: Middle and old age, abdominal malignancy, long hospital stay and surgery duration, large amount of intraoperative bleeding, long retention time of abdominal drainage tube, indwelling urethral catheter and long retention time of urethral catheter, and use of antibiotics before operation, especially the length of hospitalization ≥15 d and abdominal malignancy are the high-risk factors for HA-cIAI. For patients with above factors, effective preventive measures should be taken according to the specific condition, to prevent the occurrence of HA-cIAI.