What are the recommended initial investigations for a patient presenting with unexplained abdominal pain?

For a patient presenting with unexplained abdominal pain, the recommended initial investigations in primary care include a thorough clinical assessment and targeted tests based on age, sex, and associated symptoms. For women aged 18 and over, especially those 50 and over with persistent or frequent abdominal or pelvic pain, serum CA125 testing is recommended to assess for ovarian cancer. In adults aged 40 and over with unexplained abdominal pain and weight loss, quantitative faecal immunochemical testing (FIT) should be offered to evaluate for colorectal cancer. Adults aged 50 and over with unexplained abdominal pain should also be offered FIT to assess colorectal cancer risk. In patients aged 55 and over presenting with upper abdominal pain and weight loss, urgent referral via a suspected cancer pathway is advised for oesophageal or stomach cancer. For those aged 55 and over with upper abdominal pain accompanied by low haemoglobin, raised platelet count, nausea, or vomiting, consider non-urgent direct access upper gastrointestinal endoscopy. Adults aged 60 and over with abdominal pain and weight loss or diarrhoea/constipation should be considered for urgent direct access CT scan or ultrasound to investigate pancreatic cancer. In cases of abdominal distension in women 50 and over, serum CA125 measurement is recommended. Physical examination findings such as ascites, pelvic or abdominal masses in women warrant urgent referral via a suspected cancer pathway. Unexplained hepatosplenomegaly requires a very urgent full blood count within 48 hours to assess for leukaemia. In suspected acute appendicitis, emergency hospital admission is recommended, but if suspicion is low, additional investigations such as ultrasound or CT may be arranged in primary care to exclude alternative diagnoses. These investigations should be guided by clinical judgement and the presence of red flag symptoms such as weight loss, rectal bleeding, anaemia, or palpable masses.