Diarrhoea

Diarrhoea refers to having bowel movements that are softer, looser or watery more often than normal. Diarrhoea may cause other discomforts such as nausea, vomiting, loss of appetite, abdominal pains, and weight loss. If diarrhoea is severe or lasts a long time, the body does not absorb enough water and nutrients leading you to become dehydrated or malnourished. 

Possible causes of diarrhoea include:  

• Certain anti-cancer treatments:
  • Chemotherapy such as irinotecan, 5-fluorouracil (5-FU), capecitabine and docetaxel
  • Immunotherapy such as pembrolizumab, atezolizumab and nivolumab
  • Targeted therapies such as gefitinib, alpelisib and abemaciclib
  • Radiotherapy to the abdomen and pelvis
  • Surgery if certain parts of the bowels are removed 

• Infections of the gastro-intestinal tract 
• Certain tumours themselves can secrete hormones causing diarrhoea such as neuroendocrine, pancreatic and thyroid cancers. 
• Thyroid malfunction  
• Certain medications such as antibiotics and laxatives 
• Mental stress and anxiety. 

You should keep a stool diary to record the colour, shape and quality of your own faeces, as well as the frequency of bowel movements every day. You should also monitor your urine as darker coloured urine or a reduce volume may be signs of dehydration. Sometimes diarrhoea can be severe and therefore it is important to tell the doctor if you develop diarrhoea at night or if you develop other symptoms like, blood in the stool, abdominal pains or not passing urine for 12hours or more. The doctor may perform further tests such as: 

• Blood tests 
• Stool culture 
• Abdominal X-ray 
• CT scan 
• Colonoscopy 

Doctors may prescribe medications for diarrhoea such as: 

• Anti-diarrhoea medications for example loperamide or codeine. 
• Electrolyte replacements for example slow K and sodium chloride. 
• Analgesia for example paracetamol may help with abdominal pain associated with diarrhoea. 
• In severe cases, hospital admission may be required for intravenous rehydration and electrolyte replacements. 

The best prevention and treatment options for diarrhoea depends on the cause and symptoms you are experiencing, so talk with your health care team about what is recommended for you. 

However, the following suggestions may help you manage diarrhoea: 

• Avoid drinking caffeinated drinks (e.g. coffee or tea) and alcohol. 
• Avoid medications such as laxatives and stool softeners. 
• Drink plenty of liquids (at least 2 litres a day) to replace the fluid loss with the diarrhoea. 
• Drink moderate amounts of low/sugar-free sports drinks to replace for electrolyte losses. 
• Eat small, frequent meals made from light foods. For example, white fish, poultry, well-cooked eggs, white breast, pasta or rice. 
• Eat less fibre (for example, cereals, raw fruits and vegetables) until the diarrhoea improves. 
• Avoid dairy products, greasy, fatty and spicy foods. 
• If there is irritation or pain in the perianal area due to diarrhoea, you could bath the perianal area in lukewarm water for 10-15 minutes to promote healing in this region. 

American Society of Clinical Oncology (ASCO): Diarrhoea  

Macmillan Cancer Support: Diarrhoea 

Queensland Health: Diarrhoea during cancer treatment 

Special thanks to Dr Matthew Chiu, Department of Clinical Oncology, the University of Hong Kong, for authoring this article.