The participants of this retrospective study were selected from patients in the Endoscopic Center of the Gastroenterology Department at Meizhou People’s Hospital who underwent complete colonoscopy and first-time removal of colorectal polyps from January 2018 to June 2019. The inclusion criteria were a histological diagnosis of colorectal polyps, at least one follow-up colonoscopy performed at more than 6 months later after polyp removal, and sufficient baseline clinical and laboratory data. Patients were excluded if they had present/previous gastrointestinal tumors or cardiac or pulmonary disease. The study was approved by the Ethics Committee of Meizhou People’s Hospital Affiliated to Sun Yat-Sen University.
A total of 3,980 patients underwent an initial colonoscopy examination and removal of colorectal polyps during the study period. Of these 3,980 patients, 3,207 were excluded because they did not undergo follow-up colonoscopy. Of the remaining 773 patients, 314 lacked follow-up colonoscopy data > 6 months after removal and 24 lacked baseline lipid data. Finally, 435 patients were included in the analysis (Fig. 1).
Patients were required to consume a liquid diet for 24 hour before the examination, and polyethylene glycol was used for standard bowel preparation. A complete colonoscopy including a good bowel preparation, colonoscopy reaching the cecum, and removing visualized lesions by endoscopic mucosal resection (EMR) was performed by experienced physicians. Biopsy specimens were inspected under a microscope by experienced pathologists.
Polyp classification and definition of polyp recurrence
The pathologic characteristics of the colorectal polyps were obtained from the patients’ pathology reports. The polyps were classified into hyperplastic polyps, inflammatory polyps, tubular adenoma, or tubulovillous adenoma. Advanced polyps were diagnosed if one or more of the following conditions were met: tubular adenoma of ≥10 mm in diameter, tubulovillous adenoma, or the presence of high-grade dysplasia . The location of the polyps was defined as proximal (cecum, ascending colon, hepatic flexure, transverse colon, and splenic flexure) or distal (descending colon, sigmoid colon, and rectum). In patients with multiple polyps, the histologic type, size, and location was based on the largest and/or most advanced adenoma.
Polyp recurrence was defined as the discovery of any polyp in the follow-up colonoscopy examination performed at least 6 months after the initial removal, whether at the same location or at other locations [12, 24].
Lipid profile testing and clinical data collection
Peripheral venous blood samples were collected within 24 hour after admission. The fasting lipid profiles, including the levels of total cholesterol, TG, high-density lipoprotein cholesterol (HDL-C), and LDL-C, were examined by selective solubilization (AU5800 analyzer; Beckman Coulter, Brea, CA, USA). The apolipoprotein A1 (ApoA1) and apolipoprotein B(ApoB) levels were tested using standard turbidimetric immunoassays (AU5800 analyzer; Beckman Coulter). Baseline characteristics including sex, age, BMI, drinking/smoking history, hypertension, and diabetes mellitus were collected from the medical records.
Drinking was defined as positive when alcohol consumption amounted to >30 g/day. Hypertension was defined as blood pressure of ≥130/85 mmHg and/or current use of antihypertensive medication. Diabetes mellitus was diagnosed if the patient had a fasting blood glucose level of ≥ 126 mg/dL, a random glucose level of ≥ 200 mg/dL, or was taking an antidiabetic medication . Dyslipidemia was defined as a total cholesterol level of ≥ 5.17 mmol/L, TG level of ≥ 1.7 mmol/L, HDL-C level of < 1.04 mmol/L, LDL-C level of ≥ 4.14 mmol/L, or current treatment with antidyslipidemic medication.
Statistical analyses were performed using SPSS software version 22.0 (IBM Corp., Armonk, NY, USA). Continuous variables are expressed as mean ± standard deviation, and categorical variables are expressed as proportion. The normality of the distribution of continuous variables was evaluated with the Kolmogorov–Smirnov test. Continuous variables were tested by Student’s t test, whereas categorical variables were analyzed by the chi-square (χ2) test or Fisher’s exact test. Bonferroni correction was used for multiple comparisons. Logistic regression analysis was used to investigate the association of serum lipids and polyp recurrence. Odds ratios (ORs) were calculated by adjusting for variables that were distributed differently between patients with and without recurrence. All tests were two-sided, and a P value of < 0.05 was considered statistically significant.