Rectal bleeding

When to get help straight away

Most rectal bleeding is not an emergency. The list above is short on purpose, because those are the situations where waiting for an appointment is the wrong move.

What causes it

The bowel bleeds for a long list of reasons, and the common ones are not the dangerous ones.

• Haemorrhoids, by far the most frequent cause. Bright red blood on the paper or in the bowl, often painless, often with constipation or straining behind it.
• Anal fissure, a small tear in the anal lining. Sharp pain during and after opening the bowels, with blood on the paper.
• Polyps, which can bleed intermittently and which matter because some of them are on the way to becoming cancer. They are removed when found, at colonoscopy.
• Bowel cancer, which often bleeds in small amounts over a long period rather than dramatically.
• Inflammatory bowel disease, where bleeding usually comes with diarrhoea, urgency, mucus and abdominal pain.
• Diverticular bleeding, which is painless and can be sudden and heavy, and usually stops on its own.
• Angiodysplasia, fragile small blood vessels that become more common with age.
• Ischaemic colitis, where a segment of colon briefly loses its blood supply. It typically causes sudden crampy pain followed by bleeding, most often in older adults.
• Infection, after food poisoning or travel.
• Bleeding higher up, from the stomach or duodenum, which turns the stool black and tarry rather than red.

The mix looks different depending on who is bleeding and how much. In people admitted to hospital with significant bleeding from the lower bowel, the commonest cause by some margin is a bleeding diverticulum. Next come problems at the anus and rectum such as haemorrhoids and fissures, then ischaemic colitis, then polyps and bowel cancer. Less often it is bleeding after a procedure such as polyp removal, inflammatory bowel disease, or an abnormal cluster of small vessels in the bowel wall. In general practice and in the rooms, where the bleeding is minor, haemorrhoids and fissures dominate that list by a wide margin.

What the colour and pattern suggest

Colour is a clue rather than a diagnosis, and it is worth taking notice of before an appointment.

• Bright red on the paper or on the surface of the stool usually comes from the anus or the lowest part of the bowel. Haemorrhoids and fissures behave this way.
• Darker red, or blood mixed through the stool, suggests a source further up the colon.
• Black and tarry, with a strong smell, suggests bleeding from the stomach or small bowel. This needs same-day assessment. Iron tablets and some foods also darken the stool, which is worth mentioning rather than assuming either way.
• Blood mixed with mucus and diarrhoea points towards inflammation or infection.

There is one important exception to all of this. Bleeding that is brisk enough can travel through the bowel too fast to darken, so a heavy bleed from the stomach or duodenum can arrive as bright red blood from the back passage. In around 15 per cent of people presenting with brisk rectal bleeding the source turns out to be in the upper gut. That is part of why someone bleeding heavily is assessed for both ends rather than one.

Slow bleeding is the other end of the same spectrum. Losing small amounts over months may never be visible at all, and shows up instead as iron deficiency anaemia on a blood test. That is a reason to investigate in its own right.

Two other things are worth noting: whether the bleeding happens every time or occasionally, and whether anything has changed in your bowel habit over the same period. Both change how the symptom is interpreted.

How it is assessed

The consultation starts with the history, because the pattern usually narrows the list before any test is done. Then an examination, which includes examining the anus and, where appropriate, a look at the anal canal with a small scope in the rooms. This is quick and it identifies haemorrhoids and fissures without anything further.

Blood tests check the full blood count and iron stores, because iron deficiency alongside bleeding changes the urgency. Stool tests are used where there is diarrhoea.

For most adults the definitive test is a colonoscopy, which looks at the whole colon and allows polyps to be removed and biopsies to be taken in the same procedure. Where the stool has been black, a gastroscopy is done as well or instead.

Heavier bleeding, and what happens in hospital

Most rectal bleeding is dealt with in general practice and in the rooms. A smaller group bleed heavily enough to need hospital, and that situation has its own name and its own pathway. Bleeding from the colon or rectum is called lower gastrointestinal bleeding, and it is one of the commonest reasons people are admitted to hospital with a digestive problem.

It is largely a condition of older adults. In the largest British audit the median age was 74, and admissions have been rising, most clearly in people over 80, at the same time as admissions for bleeding from the stomach and oesophagus have been falling. Part of that is simply an ageing population. Blood thinners matter too: in that same audit nearly a third of those admitted were taking an antiplatelet medicine such as aspirin and about one in six was on an anticoagulant. Those medicines do not usually create the bleeding point. They make an existing one bleed more, and for longer.

The reassuring part is that most lower gastrointestinal bleeding stops on its own without anything being done to it, and most people admitted with it go home well. Among those admitted with major bleeding, between 3 and 4 in every 100 die in hospital. Those deaths are driven by age and other serious illnesses rather than by the bleeding itself, and the risk is much lower again in otherwise well people whose bleeding turns out to come from haemorrhoids or a polyp. That figure describes hospital care for a large bleed. It is not the risk that attaches to blood on the paper.

What the assessment involves

• Blood tests including a full blood count, clotting and a cross-match, with clotting corrected where it is abnormal.
• A careful look at the medicine list, particularly antiplatelet and anticoagulant medicines, which are reviewed rather than automatically stopped.
• An examination that includes the rectum, which sounds basic and often gives the answer.
• Ruling out an upper gut source where the bleeding is brisk or the picture is unstable, because that changes the whole approach.
• A risk score. Several validated tools exist, and they are used to separate people who can safely go home with an outpatient plan from those who need admission. This is not rationing. It is a way of not keeping someone in hospital for a problem that has already stopped.

Where investigation is needed, a colonoscopy after bowel preparation is usually the main test, because it can identify the source and treat it in the same sitting. Where the bleeding is very fast, a CT angiogram can pinpoint the bleeding vessel first, and an interventional radiologist can sometimes block it off. Surgery is now rarely needed for bleeding alone.

Who needs a colonoscopy, and how quickly

The starting point is that visible rectal bleeding needs an explanation, and the explanation has to actually fit. The question is not whether someone is old enough to warrant investigating. It is whether anything short of a colonoscopy has genuinely accounted for the blood.

A colonoscopy is recommended when the bleeding is mixed through the stool rather than sitting on the surface, when it has persisted or kept coming back over weeks, when bowel habit has changed, when there is iron deficiency, weight loss or abdominal pain, when there is a family history of bowel cancer or polyps, or when the examination does not fully account for the bleeding. Age adds to the case for it. It never subtracts from it.

Assessment is not optional. What follows it can vary

Every episode of visible rectal bleeding needs to be assessed. That part is not a judgement call, and it does not depend on age, on how much blood there was or on whether it has already stopped. What can reasonably differ is what happens after that assessment.

In some people a careful history and examination find a clear anorectal cause, such as a fissure or haemorrhoids, with a plausible precipitant like constipation, blood only on the paper and nothing else of concern in the history, the examination or the blood tests. For them it is reasonable to treat the cause and review rather than proceed straight to a colonoscopy. That is a decision made at the end of a proper assessment. It is not a reason to skip one, and it is not something to decide at home.

Where that course is taken, two things keep it safe. The review is booked rather than left open-ended, and the timeframe is a few weeks rather than months. If the bleeding has not settled, or it returns, or it changes in any way, the colonoscopy happens.

Two things are worth saying plainly, because both cause delay. Finding haemorrhoids explains the blood that can be seen, not the blood that cannot, and almost everyone examined for bleeding has some. And a home screening test is not a way to decide whether someone with symptoms needs a colonoscopy. It is designed for people with no symptoms, and a negative result in someone who is visibly bleeding is falsely reassuring.

How quickly

Urgency is decided in the New South Wales public system by the colonoscopy categorisation clinical practice guide, which sorts referrals into a procedure within 30, 90 or 365 days depending on the indication. Rectal bleeding sits high in that order. A/Prof Kariyawasam was a member of the working group behind that guide and is clinical co-chair of the Agency for Clinical Innovation's Gastroenterology Network, and there is more on how the categories work in the news section.

The mistake worth avoiding

The commonest error with rectal bleeding, made by patients and occasionally by clinicians, is to stop at the first explanation. Haemorrhoids are so common that almost anyone being examined for bleeding will have some. Finding them does not prove they are the source.

Most people who have rectal bleeding do not have cancer, and saying so is not a reason to skip the assessment. The reason bowel cancer is so treatable when it is found early is that it announces itself in small, unremarkable ways, and bleeding is the commonest of them. Blood that has been put down to haemorrhoids for a year is the story behind a good number of late diagnoses.

If bleeding was investigated and explained, and then changes in amount, colour or pattern, it needs looking at again rather than being filed under the old answer.

Where rectal bleeding is assessed in Sydney

A/Prof Viraj Kariyawasam is a consultant gastroenterologist and hepatologist. Rectal bleeding is triaged as a priority and is assessed at consultation in Norwest, Rouse Hill, Pennant Hills and Macquarie Park.

The colonoscopy is performed at Norwest Private Hospital, Macquarie University Hospital and Pennant Hills Day Surgery. A referral from your GP is needed for a consultation.