Why does gastroenteritis cause blood in stool?

Blood in Stool is a common presentation of Gastroenteritis. Certain infections can cause more intense inflammation of the intestine, which may lead to red blood or mucus mixed with loose stool.

Fresh red blood may come from bleeding lower in the digestive tract, while dark, black, tar-like stool can suggest bleeding higher up. Blood can also be caused by conditions other than gastroenteritis, including problems around the anus or bowel inflammation.

The colour, amount, frequency, and accompanying symptoms give a clinician useful clues. Blood in stool should not be self-diagnosed as an infection.

Contact a clinician promptly for advice, particularly if blood is new or occurs with diarrhoea. Keep drinking fluids in small frequent amounts and note whether you also have fever, cramps, vomiting, recent travel, or a change in the amount of blood.

Avoid taking anti-diarrhoea medicine unless a clinician or pharmacist says it is appropriate when blood is present. Careful handwashing after toilet use helps reduce spread if an infection is involved.

Seek urgent medical care for a large amount of blood, black tar-like stool, severe or worsening abdominal pain, fainting, confusion, a very unwell appearance, or inability to keep fluids down.

Children, older adults, pregnant people, and people with weakened immunity can become unwell more quickly with diarrhoea and bleeding, so they should be assessed without delay.

Ask whether a stool test, blood test, or examination is needed and whether any medicine should be avoided. Tell the clinician about recent antibiotics, travel, sick contacts, long-term bowel conditions, and any medicines that affect bleeding.