In Figure 17.1 the differential diagnosis is arranged in order of likelihood in a woman of this age, with more likely diagnoses in larger font and less likely diagnoses in smaller font. Pathologies that should be excluded at the earliest possible opportunity are shown in bold. There are a number of gynaecological pathologies that can cause acute LIF pain. Some, such as ectopic pregnancy, mittelschmerz (mid-cycle pain), or haemorrhage into a functional ovarian cyst, can only occur in menstruating women. Others, such as pelvic inflammatory disease or torsion/rupture of an ovarian cyst, are far more likely to be seen in women younger than Mrs Hamilton, but can be kept in mind as rare differentials for someone of her age. Testicular torsion can cause referred pain to either the left or right iliac fossa and tends to occur in boys and young men. Haemorrhage into a testicular tumour can also cause left or right iliac fossa pain. Thus, don’t forget to examine the testes. You should ask the standard array of questions about the pain—remember the mnemonic SOCRATES: Site: Where is the pain, and has it always been there? Pain that is initially poorly localized, midline, and colicky but which then migrates to the LIF and becomes constant is highly suggestive of acute diverticulitis (akin to left-sided appendicitis). Pain that migrates down the left flank and iliac fossa is more consistent with the migration of a ureteric stone. Onset: Gradual or sudden? Sudden onset of pain is suggestive of perforation of a viscus, or of acute haemorrhage (e.g. into an ovarian cyst or from a ruptured AAA) or torsion (of an ovary or testis). Character: Is the pain colicky or constant? Is it sharp or dull? Acute diverticulitis is often preceded by colicky midline pain. Ureteric calculi may result in colicky pain. Established diverticulitis, and the other differential diagnoses from our list would all produce constant abdominal pain. Sharp pain is most suggestive of haemorrhage, perforation, or torsion. Radiation: Does the pain radiate to the groin (typical of ureteric pain)? Alleviating factors: Does anything make the pain better? Discomfort due to irritable bowel syndrome (IBS) may be relieved by defecation.