Occult bleeding – causes and timely diagnosis

What occult bleeding is

If a person detects blood in his/her stool, that is always a sign of a problem. Such bleeding may be a symptom of any number of health complications, from entirely common problems to very serious illnesses.

If blood appears in the stool, it is always appropriate to seek medical assistance for the sake of certainty. The doctor will be particularly interested in knowing whether the blood is in liquid form or is an admixture in the stool, and whether it is dark, light or bright red in colour or a combination thereof.

• Dark blood (melena) – This usually indicates bleeding in the upper part of the digestive tract (from the mouth to the upper part of the small intestine). As it passes through the body, the blood is partially digested, darkening in colour to brown or even black, and having a strong odour.

• Bright red blood – Fresh blood in the stool (intestinal haemorrhage) usually appears in the case of bleeding from the lower third of the small intestine, the colon or the rectum. It isn’t digested, so it remains bright in colour and thus easily visible.

• Mixed bleeding – digested blood occurs in the stool simultaneously with bright red, undigested blood. This is an indication of certain problems in the small intestine, e.g. Meckel’s diverticulum.

The above-mentioned occurrences are easily visible to the naked eye. When the amount of blood in the stool is smaller, it is not apparent and can be detect only by means of a test for the presence of blood in the stool or a laboratory screening. This refers to occult bleeding. The fact that the amount of blood is small does not mean that this condition does not require attention.

Possible causes of (not only) occult bleeding

“The causes of visible and hidden, i.e. occult, bleeding may include any number of common issues (e.g. haemorrhoids or anal fissures), as well as serious illnesses such as colorectal cancer,” says MUDr. Lucie Valoušková, general practitioner for adults and physician at EUC PLS.

Our article is focused on occult bleeding, when there is a quantity of blood that is invisible to the naked eye present in the stool. Below, we provide a summary of the most common causes of the presence of any blood in the stool, though the amount of blood in the stool may vary in the case of individual causes, so it may occur in a hidden and visible way.

We will then briefly go over colon cancer, a typical symptom of which is, among other things, occult bleeding, and we will subsequently provide a brief description of the principles of testing the stool for occult bleeding.

• haemorrhoids – an entire article focused on this issue is available here.
• polyps in the colon – benign growths that, however, can develop into malignant tumours.
• anal fissures – tears in the area of the anus, the occurrence of which often involves haemorrhoids, constipation, a sedentary lifestyle or previous childbirth.
• oesophageal illness – e.g. inflammation, Mallory-Weiss syndrome, oesophageal varices.
• infection of the digestive tract or intestines – e.g. salmonella or dysentery.
• diverticulosis – inflammation in the colon caused by diverticula (protrusions), which can complicate the passage of stool and increase the propagation of bacteria.
• stomach and duodenal ulcers.
• autoimmune inflammation – e.g. Crohn’s disease, ulcerative colitis or coeliac disease.
• ischemic colitis and radiation colitis.
• vascular malformation of the intestines.
• rectal prolapse.
• conditions with high rates of bleeding – e.g. haemophilia, Von Willebrand disease.
• bleeding from the biliary tract.
• colorectal cancer – covered in greater detail below.

Colorectal cancer

Colorectal cancer is a disease in which a malignant tumour is, in most cases, preceded by the presence of polyps, which are small growths on the lining of the colon. The symptoms of colorectal cancer many include the following:

• diarrhoea and/or constipation, possibly frequently alternating.
• very thin stool
• abdominal pain.
• weight loss with no apparent cause.
• fatigue.
• blood in the stool – typically hidden, i.e. occult.

It often happens that a tumour develops over a long period of time without symptoms, but early detection of the disease is possible by means of recommended blanket screenings performed for people over the age of 50 (covered in greater detail below).

Treatment consists in surgical removal of the tumour, radiation therapy or chemotherapy, or possibly a combination of these methods. Again, it is necessary to add that the sooner colorectal cancer is detected, the greater the chance of successful treatment.

Faecal occult blood test (FOBT)

This examination is carried out particularly for the purpose of ruling out or confirming the occurrence of serious illnesses such as colorectal cancer, in the case of which timely diagnosis is absolutely crucial. An FOBT is recommended mainly for persons over the age of 50, once a year with a general practitioner for those aged 50 to approximately 50. For those over the age of 55, the test is performed once every two years, also by a general practitioner.

As an alternative to this relatively common stool test, a general practitioner may recommend a primary screening colonoscopy. This is a substitute for the stool test and, if the result is negative, the interval between primary screening colonoscopies is ten years.

In the Czech Republic, persons over the age of 50 are entitled to all of these examinations free of charge. Your general practitioner will provide you with more detailed information during a preventive check-up, for example.

Tests on a chemical (Haemoccult) or immunochemical (iFOBT) basis are used to detect occult bleeding. Tests for detecting occult bleeding are part of two-stage screening programmes, which means that an FOBT with a positive result is followed by a colonoscopy.

• Immunochemical test – This is currently the most frequently used screening test. In comparison to earlier tests, it is more pleasant, as no dietary measures are required and the result is not dependent on any pharmacological treatment and only one stool sample is sufficient. The sample is collected in a test tube, which is subsequently handed over to the doctor and sent for laboratory tests for detecting the presence of blood, even in the smallest quantity. The stool may not come into contact with water prior to taking a sample.

• Chemical test – This test uses a coloured chemical reaction, which may capture, for example, certain substances from food (dietary measures are thus necessary prior to the test). A newer version of the test uses the reaction of a specific antibody (dietary measures are not necessary in this case).

If blood is detected in the stool, the doctor will send the patient for a follow-up examination in order to determine the cause of bleeding. This most commonly involves an endoscopic examination of the colon (colonoscopy, gastroscopy). If a polyp is the cause of bleeding, it can be removed during the colonoscopy, thus preventing its possible eventual development into a malignant tumour.

Diagnosis of occult bleeding in brief

When blood is found in the stool, it usually does not have a very serious cause, especially when no other symptoms are present. If, however, blood in the stool is accompanied by other symptoms such as weight loss with no apparent cause, lack of appetite, alternating diarrhoea and constipation, high temperature and abdominal pain, caution is advised, as this may indicate colorectal cancer.

“The primary diagnosis is focused mainly on examining a stool sample using a faecal occult blood test to detect the presence of blood that is invisible to the naked eye. If the result of this test is positive, the patient will usually undergo a diagnostic gastroscopy or colonoscopy and follow-up treatment will be based on the particular cause of bleeding,” says MUDr. Lucie Valoušková.

In the event of any suspicious blood in the stool, seek medical attention. It is important to focus on prevention, as it is recommend that those over the age of 50 undergo regular testing for the presence of occult bleeding, ideally once per year. The test can be administered by a general practitioner or, in the case of women, by a gynaecologist.

You can also contact the specialists at EUC clinics.