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Living well with cancer: Cancer and bowel changes

By July 19, 2023No Comments

Cancer treatments including chemotherapy, immunotherapy, targeted therapy, and hormone blocking therapy can all cause bowel changes such as diarrhoea and constipation. In these instances, the bowel changes are usually temporary whist undergoing treatment. Radiation therapy to the abdomen and pelvis, and surgery to the bowels can also cause bowel changes which can be temporary, and can be permanent.

Here are some simple tips and information that may offer some help with managing these symptoms.


Diarrhoea is passing loose or watery bowel motions more often than normal. Diarrhoea can be associated with abdominal cramping, increased flatulence/wind, pain in rectum.

Chemotherapy, immunotherapy and radiation to the abdomen or pelvis can cause diarrhoea. Other causes for diarrhoea include antibiotics, other medications, anxiety or stress, infection, food poisoning or food intolerances. It is important to determine the underlying cause of diarrhoea to ensure correct treatment and management.

If diarrhoea is severe you may lose too much water and become dehydrated. Signs of dehydration include:

  • Feeling thirsty
  • Dry mouth
  • Headache
  • Dizziness/lightheadedness
  • Dark and concentrated urine, or passing small amounts of urine.
  • Fast heartbeat

Tips to keep hydrated:

Drink plenty of fluids: about 8 glasses a day. The best fluids to consume are water, herbal teas, clear soups, non-fizzy drinks, and soy or lactose free milk such as Zymil or Lidells.

Consider taking oral rehydration solution such as Hydralyte or Gastrolyte which you can get from a chemist.



Diet tips:

Eat plain, easy to digest foods such as bananas, crackers, white rice and pasta, white bread, potatoes without skin, chicken without skin or fish. These foods can help firm stools.

Dairy free or soy-based products may be better tolerated than dairy.

Small frequent snacks can be easier to manage than big meals – try to eat every two hours.

Avoid fried, fatty or spicy foods. Limit or reduce milk and dairy products. Reduce caffeine drinks, reduce or avoid sugar free or diet products containing sorbitol, mannitol and xylitol.

Avoid or reduce high fibre foods such as raw fruit and vegetables, skins of fruit and vegetables, nuts, legumes, seeds and bran which can sometimes worsen diarrhoea and increase wind, bloating and cramping.

If your bottom is getting sore from diarrhoea then using wet wipes/baby wipes rather than toilet paper can be softer and gentler – there are flushable versions available. Pat your skin dry – do not rub. Apply a soothing gentle moisturiser to your bottom. A warm sitz bath can also be very soothing to a sore bottom (warm water with added salt).

There are some medicines that can help reduce diarrhoea – it is important to speak with your doctor first before taking these, and take these medications as directed.

If you have uncontrolled diarrhoea and signs of dehydration, severe abdominal pain, or blood in your bowel motions then it is important to see your doctor.



Constipation means difficulty opening bowels (having a poo). Bowel movements can be painful, and the stool itself small, hard and dry. It is not necessary to have bowel movements every day; it can be considered ‘normal’ anything from 3 times per day to 3 times per week. It is considered constipation if no bowel movement for 3 days in a row.

Some cancer treatments such as chemotherapy and targeted therapy can cause constipation. Surgery to the bowel can also cause constipation. Side-effects of other medications such as strong pain killers (opioids), anti-sickness medications, blood pressure medications and anti-depressants can also cause constipation.

Tips to help prevent or treat constipation:

Drink plenty of fluids. Your body needs lots of fluids to keep poos soft and easy to pass.

Include more fibre in your diet (unless you have been advised to be on low fibre diet). Fibre helps keep our bowels working regularly. There are two kinds of fibre:  Soluble fibre which gives stools bulk. Source of soluble fibre includes apples, bananas, barley, oats and beans. There are soluble fibre supplements such as Benefiber and psyllium husk.

Insoluble fibre which helps speed up food in the digestive tract. Sources include whole grains, most vegetables, wheat bran and legumes.

It is important to make sure you are drinking plenty of water if increasing fibre or taking a fibre supplement!


Exercise – not getting much exercise each day can slow down your digestive tract. Taking regular gentle exercise such as a daily walk, or swimming, yoga or Tai Chi can help keep bowels regular.

Try to establish a regular bowel routine. People who ignore or delay opening bowels when they first get the urge are at greater risk of constipation. This is because the stool sits in the rectum longer, and water is drawn out making the stool harder and difficult to pass. Its best to listen to your body, and try to go to the toilet when you feel the urge.

There are a number of medications that work in different ways to help treat constipation – these are called laxatives or aperients. It is very important to ask your doctor for advice, and only take these medications as directed.

If you are constipated and experience any of these symptoms then please seek urgent medical help:

  • Sudden, severe abdominal pain
  • Sudden vomiting
  • Blood in your poo
  • Uncontrolled diarrhoea or liquid motions after being constipated
  • Unable to pass wind (fart)


Helpful resources:

Cancer Council: Constipation or Diarrhoea

QLD health: Diarrhoea during cancer treatment

Constipation: managing different causes

Increasing dietary fibre

Please contact our Nurses on 07 5445 5794 or nurses@bloomhill.com.au if you have any questions.

The information in this document is based on resources from the Cancer Council Queensland, and the National Cancer Institute (America). All information provided by Bloomhill is based on research and best practice guidelines. Our model of care utilizes the Clinical Oncology Society of Australia (COSA)  domains of wellness along with available clinical evidence.  Always consult your care team regarding matters that affect your health. This is a guide intended for information only.