How do I determine when to refer a patient with acute diarrhoea for specialist assessment or further investigation?

Refer a patient with acute diarrhoea for specialist assessment or further investigation if there are signs suggesting an alternative serious diagnosis, such as severe or localised abdominal pain, blood and/or mucus in stool, or bilious vomit ¹.

Hospital assessment should be considered if there are red flag symptoms indicating severe dehydration, shock, or other serious complications, including intractable vomiting, high-output diarrhoea, or suspected life-threatening conditions ².

Children with symptoms or signs suggesting shock, dehydration, or an alternative serious diagnosis should be transferred urgently to secondary care, with follow-up and safety netting for red flag symptoms ³.

In adults, referral for urgent investigation or specialist assessment is indicated if there is suspicion of cancer (e.g., positive FIT with unexplained weight loss, rectal bleeding, or iron deficiency anaemia), or if the diagnosis remains uncertain after primary assessment ¹.

Additionally, consider specialist advice if there is uncertainty about the need for admission in cases with microbiological causes or travel-related diarrhoea, or if there are risk factors such as immunosuppression or recent antibiotic use ².