Anal bleeding (bleeding from the bottom) may be caused by a
swollen blood vessel or a small tear around the anus, but it can have a
more serious cause and should never be ignored.
Rectal bleeding (known medically as
hematochezia) refers to the passage of red blood from the anus, often mixed with stool
and/or blood clots. (It is
called rectal bleeding because the rectum lies immediately above the anus, and
although red blood in the stool indeed may be coming from the rectum, as
discussed later, it also may be coming from other parts of the gastrointestinal
tract.) The severity of rectal bleeding (i.e., the quantity of blood that is
passed) varies widely. Most blood in the stool or rectal bleeding are mild and
stop on their own. Many patients report only passing a few drops of fresh blood
that turns the toilet water pink or observing spots of blood on the tissue
paper. Others may report brief passage of a spoonful or two of blood.
Generally, mild rectal bleeding can be evaluated and treated in the doctor's
office without hospitalization or the need for urgent diagnosis and treatment.
Bleeding also may be moderate or
severe. Patients with moderate bleeding will repeatedly pass larger quantities
of bright or dark red (maroon-colored) blood often mixed with stools and/or
blood clots. Patients with severe bleeding may pass several bowel movements or
a single bowel movement containing a large amount of blood. Moderate or severe
rectal bleeding can quickly deplete a patient's body of blood, leading to
symptoms of weakness, dizziness,
near-fainting or fainting, and signs
of low blood pressure or
orthostatic hypotension
(a drop in blood pressure when going from the sitting or lying position to the
standing position). Rarely, the bleeding may be so severe as to cause shock from the loss of blood. Moderate
or severe rectal bleeding usually is evaluated and treated in the hospital.
Patients with signs and symptoms of reduced volume of blood often require
emergency hospitalization, and transfusion of blood.
Most
people with rectal bleeding will see small amounts of bright-red blood on the
toilet paper after they have been to the toilet, or a few droplets that turn
the water in the toilet pink. These are typical signs of piles (haemorrhoids) or
a small tear (anal fissure) in the
skin of your anus, the opening through which stools pass.
Both
of these are very common problems, but you should not assume they are the cause
of your rectal bleeding. You should still see a GP if you have these symptoms.
In general,
bright-red blood means the bleeding has come from somewhere near your anus.
If the
blood is darker in colour and sticky, the bleeding may have
occurred higher up your digestive system. This type of bleeding
can turn your faeces black or plum-coloured (known as melaena).
Having plum-coloured,
dark and sticky faeces may be a medical emergency – you should see your GP immediately.
Is it cancer?
Many
people with rectal bleeding worry they may have bowel cancer. While rectal
bleeding can be a sign of early-stage bowel cancer, other factors may also be
present for your doctor to think you're at risk.
You should
be urgently referred to a specialist with suspected bowel cancer if you have
rectal bleeding and:
- you are aged 40 or older and have passed looser or more frequent stools for the last six weeks
- you are aged 60 or older and the bleeding has lasted for six weeks or more
- your GP has found an abnormality (such as a lump) after examining you
- you also have anaemia, a reduced number of red blood cells
- you have a family history of bowel cancer
- you have ulcerative colitis
Common causes of rectal bleeding
Some
of the most common causes of visible rectal bleeding in adults are outlined
below. However, do not try to diagnose yourself, and always see your GP
for a proper diagnosis.
Click
on the links for more information about these causes.
Piles (haemorrhoids)
Piles are swollen
blood vessels in and around the rectum. They can bleed when you have a bowel
movement, which can leave streaks of bright-red blood in your stools
and on the toilet paper. Piles may also cause itchiness around your anus.
They often heal on their own.
Anal fissure
An anal fissure is a
small tear in the skin of the anus, which can be painful as the skin is very
sensitive. The blood is usually bright red and the bleeding soon
stops. You may feel like you need to keep passing stools, even when your
bowel is empty. It often heals on its own within a few weeks.
Anal fistula
An anal fistula is a
small channel that develops between the end of the bowel, known as the anal
canal or back passage, and the skin near the anus (the opening where waste
leaves the body). They are usually painful and can cause bleeding
when you go to the toilet.
Angiodysplasia
Angiodysplasia
is a condition in which the blood vessels in the colon (part of the large
bowel) become enlarged. It is more common in older people and can cause
painless rectal bleeding.
Gastroenteritis
Gastroenteritis is
a viral or bacterial infection of the stomach and bowel, which your immune
system will usually fight off after a few days. It can cause diarrhoea that
contains traces of blood and mucus, as well as other symptoms such as vomiting and stomach cramps.
Diverticula
Diverticula is
where small bulges form in the lining of your lower bowel. These contain
weakened blood vessels that can burst and cause sudden, painless bleeding (you
may pass quite a lot of blood in your stools).
Colon cancer and polyps
Colon
cancer (a type of bowel cancer) is a
common cancer and the reason why you should always get checked by your GP if
you have rectal bleeding. The only symptom may be rectal bleeding in the early
stages, so don't ignore it. Colon cancer can be more easily treated if
diagnosed at an early stage.
Colon
cancer starts as little growths called polyps, removing
these early can prevent the cancer taking hold.
Cancer of the rectum
Cancer
of the rectum is a type of bowel cancer that
usually affects older people, but can only be ruled out after seeing your GP.
Less common causes of rectal bleeding
Some
of the more unusual causes of rectal bleeding include:
- Anticoagulant drugs, such as warfarin or aspirin, which are taken to reduce your chance of a blood clot but can sometimes cause internal bleeding.
- Inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis. These long-term conditions cause the lining of the bowel to become inflamed. Crohn’s disease affects the gut higher up, whereas ulcerative colitis affects the large bowel and rectum, further down. Both tend to cause bloody diarrhoea.
