Advanced nurse practitioners (ANPs) need to be equipped with the skills to assess, investigate, diagnose, treat and discharge patients with a variety of clinical presentations. As a trainee ANP working in a primary care centre under the supervision of a GP, the author of this article encountered a female patient who presented with intermittent abdominal pain and was eventually diagnosed with cholecystitis. The patient’s presentation was atypical and mild, which led to a short inconsequential delay in her referral to secondary care for imaging and consideration of surgery. Using this patient’s case as an example of how complex decision-making can be for ANPs, the author conducts an in-depth reflection on his practice, putting the case in the context of the existing guidelines and considering professional and ethical issues.