Colonoscopy is a complex procedure requiring both technical and non-technical skills. Performing colonoscopy also requires manual and visuospatial skills, interpretation of pathology, patient communication and a wide range of advanced therapeutic technologies. The clinical intention of colonoscopy must be individualised, and diagnostic and/or therapeutic intent rationalised, given the procedures invasive nature and associated risks. Furthermore, each colonoscopy differs due to patient factors, sedation strategy, anatomical configuration, technical challenges and endoscopist skills. Endoscopists must, therefore, demonstrate a wide range of expertise whilst working effectively in a team to manage the patient safely. It is not, therefore, surprising that mistakes in colonoscopy can occur. This article focuses on six common mistakes in colonoscopy that can be avoided to improve the procedure's safety and deliver a high-quality procedure. This, in turn, can reduce the rates of post-colonoscopy colorectal cancer (PCCRC) and improve patient experience and adherence to colonoscopy surveillance programmes. This article is based on evidence in conjunction with our collective clinical and research experience of errors in endoscopy and patient safety.

Upper and lower gastrointestinal endoscopy examinations are performed daily as routine diagnostic procedures in a large number of patients with nonspecific indications, such as heartburn, pain, anaemia, bleeding, workup of portal hypertension and so on. Most of the examinations will point to a classic diagnosis (e.g. peptic disease, cancer, variceal management), but sometimes we see patients who've had multiple diagnostic endoscopic procedures in the previous few months with nonconclusive findings. The diagnostic mistakes discussed here are those that sprang to mind based on our endoscopic experience and they are discussed in an evidence-based approach. For therapeutic endoscopic procedures (e.g. ERCP and resections), we present the most important mistakes that are often seen in our practice and have major consequences for the patient. We propose, from our experience, a simple approach to avoid these mistakes.

Examination of the pancreas and biliary and digestive structures by endoscopic ultrasonography (EUS) can be tricky and using it to make a diagnosis can be challenging. Understanding anatomical variations and postoperative modifications is vital when undertaking EUS, as is choosing the correct linear echoendoscope for the structures being examined (e.g. the hilum of the liver versus the tail of the pancreas). There can also be difficulties with tissue acquisition related to tumour location and internal structures, and there are situations when sampling is contraindicated. Consideration also needs to be given to the use of contrast with special settings and difficulties in differential diagnosis (pancreatic solid lesions, indeterminate biliary strictures, gastric neuroendocrine tumours). The role of EUS assessment after neoadjuvant therapy should also be considered. Here we discuss the most frequent mistakes that are made in pancreatobiliary and digestive EUS imaging.