Blood in stools may indicate range of chronic diseases

Faecal bleeding may be a marker of a range of chronic disease, including several cancers, previously thought to be unrelated, according to new research from the University of Dundee.

The presence of blood in stools has long been associated with colorectal cancer. The new study, led by Professor Bob Steele of Dundee’s School of Medicine, has shown that patients who recorded a positive faecal occult blood test (FOBT) were much more likely to die not only from colorectal cancer but also a range of other diseases.

Professor Steele and his team looked at data for 134,000 patients who have participated in FOBT screening in Scotland since 2000 and linked their test results with mortality data from the National Records of Scotland over the same period. Not only were those who had a positive result more likely to die of colorectal cancer, their risk of dying from all other causes was also higher.

Furthermore, faecal bleeding was significantly associated with increased risk of dying from circulatory disease, respiratory disease, digestive diseases, neuropsychological disease, blood and endocrine disease and non-colorectal cancer.

While further research into the links between faecal bleeding and these diseases is required, Professor Steele hopes it could one day be used to reduce the risk of premature mortality and to explore the underlying reasons for different patterns of mortality across the world. 

“This is the first observational study to demonstrate a link between faecal bleeding and increased risk of death from a range of diseases other than colorectal cancer,” he said.

“Over the past 18 years, we have operated a bowel screening programme that looks for traces of blood in faeces and this has been very successful in detecting the disease in its earliest stages and increasing survival rates. Anyone with a positive FOBT result then receives a colonoscopy to look for tumours or polyps that could explain the bleeding but there are quite a number of patients for whom blood in their stool turns out to be a false positive and who do not have colorectal cancer.

“We were always curious as to why this should be so we went back to the early cohorts to examine outcomes for those with positive compared to negative FOBT results. What we found that is that if you had a positive test you were more likely to die from colorectal cancer, which is what we expected, but we also found that all-cause mortality was higher.

“We then linked this data with specific causes of death and found that the risk of dying from a series of other diseases such as heart attacks, circulation disorders, respiratory disease and many other cancers was also higher.

“The reason for this is not clear as yet, but we think that it might be related to levels of inflammation throughout the body as this is a marker of general ill-health and chronic inflammation is a driving factor behind whole series of whole host of other diseases. In any event, if someone is found to have unexplained blood in their faeces, it may mean that they are at risk of developing chronic disease and may benefit from attention to their lifestyle.”

Faecal bleeding is associated with the male sex, age, and deprivation. After adjusting for these factors, the risk of dying from colorectal cancer remained higher among those with a positive FOBT result, as did all-cause mortality and many specific diseases.

Professor Steele was also able to link the data with a unique database of prescribing information that exists in Tayside to prove that these results were not caused by medicines that can cause bleeding.

He continued, “At present, if somebody with blood in their stool who goes on to have a colonoscopy that doesn’t show any tumour or polyps in the bowel we don’t investigate further. It is only recently that we’ve become interested in other causes of death that are unlikely to directly cause blood in stool but are somehow linked.

“The next stage is to carry out prospective studies to see if there is a link between lifestyle diseases and faecal bleeding and whether it is reversible. Perhaps in future we should be saying in these instances that we need to look at risk factors for other diseases, such as smoking or obesity, to see if interventions can be implemented at this stage to help prevent premature death.”

Professor Steele holds a Chair in Surgery at the University is one of the UK’s leading authorities on cancer screening. He is Director of the Scottish Colorectal Cancer Screening Programme, having acted as clinical lead for the UK demonstration pilot that was used to inform the decision to introduce national screening programmes throughout the UK.

He is a Fellow of The Royal Society of Edinburgh and was elected a Fellow of Academy of Medical Sciences earlier this year.