Diarrhoea

Diarrhoea can be a side effect of treatment, caused by an infection or medication you are taking.

It’s important to know how to manage diarrhoea and when to tell your treating team about it. If diarrhoea is not controlled, it can lead to dehydration, electrolyte imbalance and kidney problems.

Definition of diarrhoea

Diarrhoea is when you poo (have bowel motions) 3 or more times in a day that are loose or watery. 

Sometimes people also have stomach pain or cramping and nausea and weakness.

Causes of diarrhoea

Causes of diarrhoea include: 

• some chemotherapy drugs. These may damage the healthy cells that line the small and large bowel, causing diarrhoea.
• some targeted therapies
• immunotherapy
• infections
• drugs used to treat constipation.

When to seek medical advice

It can be difficult to know when to report diarrhoea, especially if you're not seeing your specialist or nurse regularly.

You should let your oncologist, nurse or GP know immediately if:

• you experience more than 4 watery diarrhoea episodes in 24 hours
• diarrhoea continues for more than 24 hours and does not get better after you take anti-diarrhoea medications or change your diet.

You should also seek medical advice if you have diarrhoea and any of these symptoms at the same time:

• fever of 38°C or higher
• moderate to severe abdominal cramping, pain, straining, or bloating
• dizziness or a severe headache
• dark (concentrated) urine
• a dry mouth
• black stools or blood in stools
• sudden or rapid heartbeat.

Treatment for diarrhoea

Before you take any medication, you should check with your treating team that it is suitable for you.

Treatment aims to stop the diarrhoea and replace any fluids you have lost. If diarrhoea is not controlled, you may become dehydrated.

What to do if you have diarrhoea:

• Replace the fluid you have lost. Slowly drink extra water, sports drinks such as Powerade, diluted soft drinks, cordial, or clear soup.
• Eat regular, small meals that you can digest easily, such as clear soup, dry biscuits or cheese. Banana, rice, apple sauce/puree and toast (known as the BRAT diet) are also recommended for short periods.
• Try to avoid alcohol, fresh juices and drinks with caffeine.
• Avoid foods that are spicy, fatty or high in fibre.
• Take any medication your doctor or nurse suggest to stop or reduce diarrhoea. They may recommend drugs such as Imodium or Gastro-Stop (loperamide or Lomotil).
• Consider taking rehydration fluids such as Gastrolyte and Hydralyte. You can buy these from your pharmacy and some supermarkets. These replace the lost fluid and salts, such as sodium and potassium.