The National Institutes of Health name the following symptoms as the first indicators that something has gone wrong:
Bleeding. Bleeding can occur anywhere in the digestive tract, from the mouth to the anus, The Merck Manuals remind us. Blood in vomit reveals bleeding in the upper part of the digestive system, and blood in the stools from the lower part. Blood in the stools can be either bright red, or can turn the stools tarry and black. The higher up in the tract the bleeding occurs, the darker the stools.
Bloating. This is a condition in which the stomach appears swollen and feels full, because of a build-up of gas, fluid or ingested food in the small intestine. This could occur in isolation, or in conjunction with other intestinal disorders, according to the Merck Manuals. Read more on bloating and Irritable Bowel Syndrome.
Diarrhoea. This describes the frequent passing of watery stools. Many people experience this from time to time, and often it is not a symptom of a serious disease, especially if it clears within a day or two. But chronic diarrhoea could point to a more serious condition and definitely warrants medical attention sooner rather than later. Read more on diarrhoea.
Heartburn. When acid reflux spills into the oesophagus, the burning sensation it causes is called heartburn. Symptoms can include a burning feeling in the throat, and possible chest pain. Most people get heartburn occasionally, especially after a heavy, spicy or fatty meal, but if it happens several times a week, you could have gastro-oesophageal reflux disorder (GORD).
Incontinence. This term is used to describe leakage of faeces from the bowel due to poor bowel control, says the Continence Foundation of Australia. Some medications such as certain antibiotics could cause this on a temporary basis. Or it could be a symptom of bowel diseases, such as coeliac disease or certain nerve disorders.
Nausea and vomiting. Vomiting describes the process when the contents of the stomach are forced up out of the oesophagus and out of the mouth, says the National Institutes of Health. Nausea is the feeling of abdominal discomfort that precedes the act of vomiting. It can be a symptom of a wide range of conditions from an allergy, to kidney stones to cancer or a tumour. If the nausea and vomiting persist, medical attention must be sought.
Abdominal pain. This refers to a pain anywhere between your chest and your groin. It can be localised, general, cramp-like or come in waves according the National Institutes of Health. The intensity of the pain is not always proportionally related to the seriousness of the condition by which it is caused. Abdominal pain is a symptom of the majority of digestive diseases, and it is advisable to go to a doctor if the pain does not resolve itself in a day or two.
Swallowing problems. This is also known as dysphagia. This refers to the feeling of difficulty in passing food or liquid from the mouth to the stomach, according to the American Academy of Otolaryngology. This is mostly not a symptom of serious disorders, but can cause a fair amount of discomfort. All cases should be examined by a medical doctor to exclude sinister causes.
Weight loss or gain. Weight gain for no apparent reason could be the result of poor digestion, or because of a metabolic disorder, or because of taking certain medications, or because of the shortage or malabsorption of certain nutrients. Unexplained weight loss can be the result of something such as flu or an oral ulcer, but could also be a more serious warning sign of conditions such as diabetes or cancer.
Reviewed by Dr Estelle Wilken (MBChB) (MMed Int) ,Senior Specialist, Internal Medicine and Gastroenterology, University of Stellenbosch and Tygerberg Hospital. February 2016.