Differential diagnosis
The differential diagnosis of lower abdominal pain in a young woman includes the following:
• Ectopic pregnancy—pregnancy should always be excluded in women suspected of having PID.
• Acute appendicitis—anorexia is more commonly associated with appendicitis than PID. Nausea and vomiting also occur in most patients with appendicitis but only 50% of those with PID. Cervical movement pain will occur in about a quarter of women with appendicitis (59).
• Endometriosis—the history is usually one of chronic, recurrent pain, typically related to early menstruation, but can occur at any stage of the menstrual cycle. Menorrhagia and dyspareunia are common symptoms of endometriosis. A history of pain radiating to the sacrum or pain on defecation (dyschezia) may be useful discriminators.
• Complications of an ovarian cyst (e.g. torsion or rupture). The pain is often of sudden onset and unilateral.
• Urinary tract infection—usually associated with dysuria, urinary frequency, and haematuria.
• Gastrointestinal origin such as gastroenteritis, irritable bowel syndrome, or diverticulitis—usually associated with a disturbance in bowel habit and cramping abdominal pain.
• Functional pain (Mittelschmerz), or pain with ovulation—a diagnosis of exclusion, usually occurring mid cycle, characterized by unilateral pelvic pain lasting for less than 24 hours.