AIM To investigate the association between a recent gastrointestinal(GI) endoscopy and the subsequent risk of pyogenic liver abscess(PLA).METHODS We designed a nested case control study. Using the Taiwan National Health Insurance Research Database, 2135 patients with a first diagnosis of PLA were identified from 1998 to 2011. Another 10675 patients without PLA matched by age and sex were selected as reference controls. We identified and compared the possible risk factors for PLA and GI endoscopies performed before the index date(when PLA was diagnosed) between the two cohorts. Multivariate analysis was conducted to examine the risk of PLA within the 90 d after the GI endoscopies.RESULTS Patients with a history of diabetes [adjusted odds ratio(a OR) = 4.92, 95%CI: 1.78-13.61], end-stage renal disease(a OR = 3.98, 95%CI: 1.45-10.91), biliary tract infection(a OR = 2.68, 95%CI: 2.11-3.40), liver cirrhosis(a OR = 2.19, 95%CI: 1.39-3.46), GI malignancies(a OR = 5.68, 95%CI: 4.23-7.64), appendicitis(a OR = 3.16, 95%CI: 2.27-4.41), diverticulitis(a OR = 1.64, 95%CI: 1.01-2.64), and recent endoscopic retrograde cholangiopancreatography(a OR = 27.04, 95%CI: 11.65-62.72) were significantly associated with an increased risk of PLA. After adjusting for the above risk factors and the frequency of outpatient department visits and abdominal ultrasounds during 90 d before the index date, an upper GI panendoscopy(a OR = 2.75, 95%CI: 2.05-3.69) but not a lower GI endoscopy(a OR = 1.07, 95%CI: 0.62-1.86) was significantly associated with PLA.CONCLUSION An upper GI panendoscopy performed before 90 d may increase the risk of PLA. AIM To investigate the association between a recent gastrointestinal (GI) endoscopy and the subsequent risk of pyogenic liver abscess (PLA). METHODS We designed a nested case control study. Using the Taiwan National Health Insurance Research Database, 2135 patients with a first diagnosis of PLA were identified from 1998 to 2011. Another 10675 patients without PLA matched by age and sex were selected as reference controls. We identified and compared the possible risk factors for PLA and GI endoscopies performed before the index date (when PLA was diagnosed) between the two cohorts. Multivariate analysis was conducted to examine the risk of PLA within the 90 d after the GI endoscopies. RESULTS Patients with a history of diabetes [adjusted odds ratio (a OR) = 4.92, 95% CI: 1.78-13.61], end biliary tract infection (a OR = 2.68, 95% CI: 2.11-3.40), liver cirrhosis (a OR = 2.19, 95% CI: 1.39 -3.46), GI malignancies (a OR = 5.68, 95% CI: 4.23-7.64), appe ndicitis (a OR = 3.16, 95% CI: 2.27-4.41), diverticulitis (a OR = 1.64, 95% CI: 1.01-2.64), and recent endoscopic retrograde cholangiopancreatography (a OR = 27.04, 95% CI: 11.65-62.72 After adjusting for the above risk factors and the frequency of outpatient department visits and abdominal ultrasounds during 90 d before the index date, an upper GI panendoscopy (a OR = 2.75, 95% CI: 2.05-3.69) but not a lower GI endoscopy (a OR = 1.07, 95% CI: 0.62-1.86) was significantly associated with PLA. CONCLUSION An upper GI panendoscopy performed before 90 d may increase the risk of PLA.