GI tumours are cancerous growths that can appear anywhere in the digestive tract, including the oesophagus, stomach, small intestine, colon, and rectum. These tumours can cause bleeding for various reasons, depending on where they are located, their size, and how they interact with nearby tissues. Here’s how this happens:

• Tumour growth and tissue invasion

• • Erosion of blood vessels: As tumours grow, they can invade nearby blood vessels. The walls of these blood vessels are relatively fragile, and when tumours disrupt them, it can cause bleeding directly into the GI tract.
  • Ulceration: Tumours, especially in the stomach and oesophagus, can lead to ulceration, where the mucosal lining gets damaged and forms ulcers. These ulcers are prone to bleeding.

• Local inflammation and infection

• • Inflammation: Tumours can trigger an inflammatory response in the body. This inflammation can weaken blood vessels and the lining of the GI tract, making them more susceptible to bleeding.
  • Infection: Tumour tissue can become ulcerated or necrotic (dead), leading to secondary infections. These infections can worsen inflammation and further damage blood vessels and surrounding tissues, increasing the risk of bleeding.

• Mechanical obstruction and increased pressure

• • Obstruction: Tumours can block parts of the GI tract, causing increased pressure. This pressure can cause dilated blood vessels (varices), particularly in the oesophagus, to rupture and bleed.
  • Increased intratumoral pressure: As tumours grow, the pressure inside them increases, which can cause the blood vessels within the tumour to rupture, leading to bleeding into the GI tract.

• Effects of chemoradiotherapy 

• • Radiation and chemotherapy: These treatments can damage the mucosal lining of the GI tract, leading to inflammation (mucositis) and ulceration. This damage makes the lining more prone to bleeding.
  • Tumour lysis syndrome: In some rare cases, effective chemotherapy can cause rapid tumour breakdown, leading to sudden bleeding from the tumour site.

• Genetic and molecular factors

• • Genetic mutations: Certain genetic mutations found in tumours, such as in gastrointestinal stromal tumours (GISTs), can lead to aggressive tumour growth and higher risks of bleeding. 
  • Molecular pathways: Abnormalities in molecular pathways that regulate the formation of new blood vessels (angiogenesis) can result in the formation of fragile blood vessels within tumours, which are prone to bleeding.

• Coagulation disorders

• • Tumour-associated coagulopathy: Some tumours produce substances that affect blood clotting. These substances can either cause excessive clotting (leading to a condition known as disseminated intravascular coagulation) or impair clotting, both of which can result in bleeding.
  • Paraneoplastic syndromes: These are conditions caused indirectly by tumours through the production of biologically active substances. They can include disorders that affect blood clotting, increasing the risk of bleeding.

In Singapore, there are several factors that can increase the risk of developing gastrointestinal tumours and experiencing bleeding. Here's who might be at higher risk:

• Smokers: Smoking is known to increase the risk of developing tumours in the digestive system, which can lead to bleeding.
• People who frequently use NSAIDs: Medications like aspirin and ibuprofen can damage the stomach and intestines, causing ulcers and bleeding if used often.
• Heavy drinkers: Excessive alcohol consumption can lead to serious conditions like esophageal varices (swollen veins in the oesophagus) and tears in the oesophagus, both of which can cause bleeding.
• Individuals with chronic liver disease: Those with advanced liver conditions are more likely to experience complications like esophageal varices, which can bleed.
• People with chronic kidney problems: Chronic renal failure can also contribute to the risk of gastrointestinal bleeding.
• Those with H. pylori infections: This bacteria can cause peptic ulcers, a common source of upper gastrointestinal bleeding.
• Patients with inflammatory bowel disease: Conditions such as ulcerative colitis and Crohn’s disease can cause significant inflammation and bleeding in the digestive tract.
• Older adults: As people age, the risk of gastrointestinal issues, including tumours and bleeding, increases.
• Cancer patients: Those undergoing treatments like chemotherapy and radiotherapy, especially for cancers like pancreatic cancer, may experience bleeding as a complication.
• People with certain genetic factors: Some individuals may have a genetic predisposition to conditions like GIST and other digestive cancers.

Being aware of these risk factors can help with early detection and prevention. Regular medical check-ups and taking steps to manage these risk factors can go a long way in reducing the risk of gastrointestinal tumours and bleeding.

Diagnosing gastrointestinal tumours and bleeding involves several steps and different procedures to identify the source and nature of the problem. Here’s how it’s usually done:

• Medical history and symptoms review: The doctor will start by asking about your symptoms and medical history. This helps in understanding the severity and possible causes of the bleeding.
• Stool sample: A stool sample might be requested to check for the presence of blood, which can indicate bleeding somewhere in the gastrointestinal tract.
• Gastroscopy: For upper GI bleeding, a gastroscopy is commonly used. This procedure involves inserting a flexible tube with a camera down your throat to look inside your oesophagus, stomach, and the first part of your small intestine.
• Enteroscopy: If the cause of the bleeding isn’t found with a gastroscopy, an enteroscopy might be performed. This is similar to a gastroscopy but includes a balloon to help open up the small intestine for better viewing.
• Colonoscopy: For lower GI bleeding, a colonoscopy is used. This involves inserting a flexible tube with a camera into your rectum to examine the entire length of your colon. During this procedure, a biopsy might be taken if abnormal areas are found.
• Radionuclide scan: A scan using a harmless radioactive tracer can be performed. This tracer is injected into your veins and helps locate the source of the bleeding on an X-ray.
• CT angiography: A CT scan is used to get detailed images of the abdomen and pelvis, helping to locate the source of the GI bleeding more precisely than an X-ray.
• Capsule endoscopy: If other methods fail to find the source of the bleeding, capsule endoscopy might be done. You swallow a pill containing a small camera that takes pictures as it moves through your bowel, identifying any bleeding areas.

These diagnostic tools help doctors accurately identify the location and cause of gastrointestinal tumours and bleeding, guiding them to the most appropriate treatment plan.