Understanding the Spectrum
Constipation is very common — it affects about one in five Australians at any given time. In the vast majority of cases, it comes down to everyday factors: not enough fibre or fluid, too little activity, stress, or a medication side effect. This kind of constipation, though genuinely unpleasant, is not a sign of anything sinister. It responds well to dietary changes and, if needed, laxatives.
But constipation can occasionally be the first outward sign of something more serious — including bowel cancer, a blockage in the bowel, or another medical condition. The good news is that you do not need to be anxious about every episode of constipation. You just need to know which warning signs mean "see your doctor soon" — and which situations mean "go now." That is what this page covers.
Red Flag Symptoms: Seek Prompt Medical Attention
Please see your GP promptly — ideally within a few days — if you have constipation along with any of these:
• Blood that is mixed through your stool (not just on the paper), or stools that are dark, black, or tarry
• Unexplained weight loss — losing 3–5 kg or more without trying, over the past few months
• Constipation that is new for you, or a persistent change in your usual bowel habit, if you are over 50
• A family history of bowel cancer — particularly a parent or sibling diagnosed before age 55
• Constipation accompanied by severe abdominal pain that is getting worse
• Symptoms that wake you from sleep at night
• A feeling that there is a lump or heaviness in your lower abdomen or back passage
• Persistent nausea or vomiting alongside the constipation
• Significant bloating that is not going away on its own
Any one of these symptoms on its own is enough reason to make a GP appointment soon. If you have several of them together — or if you are older — it is worth going sooner rather than later.
Blood in the Stool
Blood in or from the back passage is the symptom people most often try to explain away — and understandably so. Haemorrhoids (piles) are the single most common cause of bright red rectal bleeding, and most of the time that is all it is. But bowel cancer also causes rectal bleeding, and it cannot be identified without proper assessment. It is not a symptom to sit on.
The features that are more worrying include blood that is mixed through the stool itself (rather than just coating the outside or appearing on the paper), dark brown, maroon, or black-coloured stools (which can mean the bleeding is coming from higher up), and blood that comes with mucus or slime. That said, even bleeding that looks exactly like haemorrhoids should be properly checked — particularly if you are over 45 and have not had a colonoscopy recently.
One more thing to be aware of: sometimes bowel bleeding is so slow and gradual that you never see any blood at all — but it still shows up on a blood test as anaemia (low iron or low red blood cells). If your GP finds unexplained anaemia, investigating your bowel is part of working out why.
New-Onset Constipation After 50
Most adults have a reasonably predictable bowel pattern. When someone over 50 notices a new, unexplained change in that pattern — whether things have slowed down, become looser, become more frequent, or the shape or size of the stool has changed — that change deserves investigation. A colonoscopy (a camera examination of the bowel) is the most reliable way to check whether a tumour or a large polyp is causing any narrowing of the bowel.
This does not mean every person over 50 who has a constipated week after a holiday needs a colonoscopy. Context matters. If there is an obvious explanation — a change in diet, travel, illness, or a new medication — that is usually reassuring. But if your diet and lifestyle have not changed and your bowels have, that is the conversation to have with your GP.
Unexplained Weight Loss
Losing weight without trying — especially if it is more than about 5% of your body weight over six months — is a symptom that doctors take seriously across the board, not just in bowel conditions. When unexplained weight loss happens at the same time as a change in your bowel habit, the combination raises the level of concern and calls for prompt investigation.
It is especially worth noting if you have also lost your appetite around the same time — that combination in particular tends to be associated with cancer-related changes in the body. This is different from losing weight because you have been eating less deliberately. If the weight is coming off on its own and you are not sure why, please tell your doctor.
Family History of Bowel Cancer
Family history matters. If a parent, sibling, or child has been diagnosed with bowel cancer — particularly before age 55 — your own lifetime risk is meaningfully higher than average. Having two or more close relatives with bowel cancer raises it further. This does not mean you will definitely develop it, but it does mean you should start bowel cancer screening earlier and have it more often than the general population.
Some families carry specific inherited conditions — such as Lynch syndrome or familial adenomatous polyposis (FAP) — that carry a much higher lifetime risk of bowel cancer and require close, specialist monitoring from a young age. If you have concerns about your family history, your GP can refer you to a colorectal surgeon or a genetics service who can work out your individual risk and put a surveillance plan in place. It is much better to know.
When to Go to the Emergency Department
Most constipation can wait for a GP appointment — but some situations cannot. Go straight to the nearest emergency department, or call 000, if you have:
- Not been able to pass stool or wind for several days, and your abdomen is becoming more bloated, hard, and painful — this can mean a bowel obstruction (a blockage)
- Severe vomiting alongside constipation — especially if the vomit starts to smell faecal (like stool), which is a sign the blockage is high up
- A rigid, board-like abdomen with severe, widespread pain and fever — these are signs of peritonitis, which means something may have perforated (burst) in your abdomen
- Sudden onset of very severe abdominal pain that is constant (not coming and going in waves)
- Inability to keep any fluids down, with signs of dehydration such as dizziness, dry mouth, or not passing urine
Please do not wait for a GP appointment if you have any of these. These are surgical emergencies — the emergency department is the right place to be.
Constipation That Does Not Respond to Treatment
If you have genuinely tried — more fibre (aiming for 25–30 g daily), more water (1.5–2 litres a day), regular physical activity, and fibre supplements — for four to six weeks, and your constipation has not improved, it is worth seeing a doctor even if you have none of the red flag symptoms above. Stubborn constipation that does not respond to lifestyle changes deserves a proper explanation.
Your GP will usually start with a few blood tests to check for medical causes — thyroid problems, high calcium, and anaemia are the most common things to exclude. If the tests come back normal and you are still struggling, referral to a colorectal surgeon is the next step. There are physical causes of constipation — like rectal prolapse (where the bowel slides down on itself), a rectocele (a bulge in the rectal wall), or a bowel that moves too slowly — that can only be identified with specialist testing. These include anorectal manometry (a test of how the bowel muscles work) and imaging studies of defaecation. These tests are not as uncomfortable as they sound, and they often provide the answer that finally explains what has been happening.
Frequently Asked Questions
Yes, if it is severe or goes on for a long time. The main complication to be aware of is faecal impaction — where a hard lump of stool gets stuck in the rectum and cannot come out. This can cause overflow diarrhoea (where liquid stool leaks around the blockage — which can be confusing), urinary retention, and in rare cases a perforation if the pressure builds too high. Chronic straining can also contribute to haemorrhoids, anal fissures (small tears), and over time, rectal prolapse. None of these is something you have to just live with — they are all treatable — but they are reasons why persistent constipation is worth addressing properly rather than hoping it sorts itself out.
Occasionally, yes — particularly if you have been travelling, unwell, or eating differently. But regularly going five or more days between bowel motions, especially if it is accompanied by discomfort, bloating, or abdominal pain, is constipation that should be addressed. If you have not gone in five days and you are uncomfortable, try a gentle laxative — and if things are not moving within a day or two, see your GP.
No — not for ordinary constipation. A colonoscopy is appropriate when there are red flag symptoms, when the constipation is new for you and you are over 45–50, when you have a significant family history of bowel cancer, or when treatment has not worked. Your GP will look at the full picture and decide whether a colonoscopy or other investigation is the right next step.
It can. A tumour growing in the left side of the bowel or the rectum can slowly narrow the passage, making it harder to pass stool. Over time, this can cause worsening constipation, stools that become unusually narrow, and eventually a blockage if it goes undetected. This is one of the reasons why new-onset constipation in an older adult should not simply be put down to diet without at least checking in with a doctor.
Australian guidelines recommend that people at average risk start screening at 45–50, using the free National Bowel Cancer Screening Program test (a simple stool test done at home every two years). If you have a significant family history — a parent or sibling with bowel cancer, especially diagnosed young — you should start earlier, typically from age 40–45 or ten years before the youngest affected relative. Speak to your GP about where you sit on that spectrum; it is a really worthwhile conversation.
Bowel cancer is predominantly a condition of older adults, but it does occur in younger people too — and rates in under-50s have been slowly rising. The reassuring truth is that functional constipation (the everyday, non-dangerous kind) is far more common in young adults than anything serious. But that does not mean ignoring symptoms. If you have persistent change in your bowel habit, rectal bleeding, or any of the red flag symptoms listed above, please get checked — do not let your age talk you out of it.
Something does not feel right about your bowel symptoms?
If you have any of the red flag symptoms above, or if your constipation has simply not responded to everything you have tried, please do not keep waiting. Mr Ba Nguyen is a specialist colorectal surgeon who can assess what is going on and help you get the right answer. A GP referral is required. Call (03) 9816 3951 or ask your GP to refer you to admin@northeasternsurgical.com.au.