How should I differentiate between uncomplicated diverticulitis and complicated diverticulitis in a primary care setting?

In primary care, differentiate between uncomplicated and complicated diverticulitis by assessing symptoms and signs as follows:

• Uncomplicated diverticulitis is suspected if the patient presents with constant abdominal pain, usually severe and localising in the left lower quadrant, possibly with fever or a change in bowel habit. Tenderness in the left lower quadrant may be present, but there are no signs of systemic illness or peritonitis NICE CKS.
• Complicated diverticulitis should be suspected if there are signs of intra-abdominal abscess (abdominal mass or peri-rectal fullness), bowel perforation and peritonitis (abdominal rigidity and guarding), sepsis (altered mental state, raised respiratory rate, low blood pressure, low urine output), fistula formation (faecaluria, pneumaturia, pyuria, passage of faeces through vagina), or intestinal obstruction (colicky pain, constipation, vomiting, distention) NICE NG147.

In addition, the presence of systemic features such as uncontrolled pain, dehydration, or immunosuppression warrants urgent hospital assessment for suspected complicated diverticulitis NICE CKS.