Which initial investigations should be performed in a patient presenting with acute abdominal pain to rule out serious conditions?

When a patient presents with acute abdominal pain, initial investigations should focus on excluding serious conditions, with actions varying based on clinical suspicion and associated symptoms.

• Suspected Acute Appendicitis: If acute appendicitis is suspected, the primary initial action is to arrange emergency hospital admission for specialist assessment and management ². A very low threshold for admission should be maintained for people with suspected complications, pregnant women, elderly people, infants, and young children ². If there is a low index of suspicion for acute appendicitis and immediate hospital admission is not considered necessary, additional investigations in primary care may be considered to exclude alternative conditions, based on clinical judgement ².
• Suspected Cancers:
  • Faecal Immunochemical Testing (FIT): Quantitative faecal immunochemical testing should be offered for unexplained abdominal pain in adults aged 50 and over, or in those aged 40 and over with unexplained weight loss, or in adults under 50 with unexplained abdominal pain and rectal bleeding [1. 3. 1]. It should also be offered for an abdominal mass or a change in bowel habit [1. 3. 1].
  • Serum CA125 and Ultrasound (for Ovarian Cancer): For women, particularly those aged 50 and over, presenting with persistent or frequent abdominal or pelvic pain (more than 12 times per month), tests should be carried out in primary care, including measuring serum CA125 [1. 5. 2, 1. 5. 6]. If serum CA125 is raised (35 IU/mL or greater), an urgent ultrasound scan of the abdomen and pelvis should be arranged ³. Similar tests should be considered for unexplained changes in bowel habit or new-onset irritable bowel syndrome symptoms in women aged 50 and over [1. 5. 3, 1. 5. 5, 1. 5. 6].
  • Full Blood Count (FBC): A very urgent full blood count (within 48 hours) should be considered for adults with unexplained hepatosplenomegaly, which may indicate leukaemia [1. 10. 1].
  • Direct Access Imaging:
    • An urgent direct access ultrasound scan (to be done within 2 weeks) should be considered for an upper abdominal mass consistent with an enlarged gall bladder or liver [1. 2. 10, 1. 2. 11].
    • An urgent direct access CT scan (to be done within 2 weeks), or an urgent ultrasound scan if CT is not available, should be considered for abdominal pain with weight loss, or diarrhoea or constipation with weight loss, in patients aged 60 and over, suggesting pancreatic cancer [1. 2. 5].
  • Direct Access Endoscopy: A non-urgent, direct access upper gastrointestinal endoscopy should be considered for upper abdominal pain with low haemoglobin levels or raised platelet count or nausea or vomiting in patients aged 55 and over, suggesting oesophageal or stomach cancer [1. 2. 3, 1. 2. 9].
• Physical Examination Findings Leading to Urgent Referral: If an abdominal or pelvic mass (not obviously uterine fibroids) or ascites is identified by physical examination in women, they should be referred using a suspected cancer pathway referral for ovarian cancer [1. 5. 1, 3]. A suspected cancer pathway referral should also be considered for a rectal mass [1. 3. 5] or an upper abdominal mass consistent with stomach cancer [1. 2. 6].
• General Unexplained Symptoms: For people with unexplained weight loss or unexplained appetite loss, an assessment for additional symptoms, signs, or findings should be carried out, and urgent investigation or a suspected cancer pathway referral should be offered [1. 13. 3, 1. 13. 4].