The aim of this sudy is to investigate the prevalence of colorectal cancer (CRC) in patients with nonalcoholic fatty liver disease (NAFLD) and evaluate whether NAFLD is a risk factor for CRC.

As one of the most common cancer worldwide, colorectal cancer (CRC) is a major cause of cancer death in Asian countries. And during the past three decades, the incidence of CRC has been increasing rapidly in china. Many studies supported that cigarette smoking, obesity and insulin resistance were associated with CRC. In recent years, metabolic syndrome (MetS) - Including glucose tolerance, dyslipidemia, obesity, hypertension and chronic inflammation - and its individual components have been proven to be the risk for colorectal neoplasm. Colonoscopy is the most accurate technique for diagnosis, surveillance and exclusion of colorectal neoplasm for high-risk CRC groups. Therefore, improved risk stratification knowledge of the target population is necessary to improve CRC patients' prognosis.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide and cause a wide spectrum of liver damage, such as steatohepatitis, cirrhosis, even end-stage liver disease and hepatocellular carcinoma. NAFLD has been found to be associated with obesity, insulin resistance, hypertension and dyslipidemia, and is considered as a liver manifestation of MetS. Although it has been also well established that MetS and its individual components are risk factors for colorectal neoplasm, as above, there is paucity of research looking at the relation between NAFLD and CRC. Therefore, the investigators aimed to investigate the prevalence of CRC in patients with NAFLD and evaluate whether NAFLD is an independent risk factor for CRC.

Inclusion Criteria:

• Patients had colonoscopy and
• Patients had conventional inspections(blood routine, liver function test and abdomen B ultrasonography)

Exclusion Criteria:

• Patients were excluded with history of colorectal cancers or polyps, other extraintestinal malignancies and contraindications to colonoscopy.
• Patients were excluded who had viral hepatitis, cirrhosis, liver cancer or other liver disease.
• Patients ere excluded who drank more than 20g alcohol per day.

The study population consisted entirely of outpatients. Patients were offered to perform colonoscopy for CRC screening according to the American College of Gastroenterology recommendations. Based on blood tests and abdomen B ultrasonography, patients without NAFLD were regarded as healthy controls and those with NAFLD constituted the community NAFLD cohort. Patients were included only if they had colonoscopy and conventional inspections (blood routine, liver function test and abdomen B ultrasonography). Among them who with history of colorectal cancers or polyps, other extraintestinal malignancies and contraindications to colonoscopy were excluded. Besides, we excluded patients who had viral hepatitis, cirrhosis, liver cancer or other liver disease.Patients who drank more than 20g alcohol per day were also excluded.