Why can cancer cause gastrointestinal bleeding?

Gastrointestinal bleeding due to cancer is a medical emergency due to vascular lesions of tumors of the gastrointestinal tract, biliary tract or liver. If not treated promptly, it can cause an acute blood loss syndrome and can even lead to death.

Gastrointestinal bleeding includes high and low gastrointestinal bleeding, caused by cancer such as esophageal cancer, gastrointestinal cancer, anal cancer, colorectal cancer,... This is a grade In medical and surgical studies, the cause of bleeding is due to vascular damage, gastrointestinal or biliary tract tumors, liver causing acute blood loss syndrome in clinical. If the patient is not treated promptly, it can lead to death in the setting of hypovolemic shock. Therefore, the treatment method needs to combine intensive resuscitation, hemostatic treatment and treatment of the cause.
The patient will have the following symptoms:
The patient vomits bright red blood in case of new bleeding, vomits black blood in case of bleeding for a long time. Black stools: common in patients with lower gastrointestinal bleeding due to cholangiocarcinoma, gastrointestinal cancer, liver cancer with cirrhosis causing esophageal varices. Blood in stools bright red or dark red: caused by low gastrointestinal cancer such as colorectal cancer, anal canal cancer... Abdominal pain: continuous or intermittent. Systemic manifestations in patients depend on the degree of blood loss such as blue skin, pale mucous membranes. After placing a gastric tube, there was fresh blood coming out of the tube. Rectal examination: bloody stools, black stools. In case of acute blood loss with a large amount, the patient will fall into a state of hemorrhagic shock with manifestations such as: dizziness, small rapid pulse difficult to catch, fainting, blood pressure drop even unmeasured, respiratory failure ,... It is necessary to place a nasogastric tube to check, but not to exclude the case of no blood, early rectal examination to find black stools, sometimes acute gastroduodenal endoscopy to determine in some cases of acute blood loss without hematemesis or melena.

The paraclinical methods used in the diagnosis of gastrointestinal bleeding due to cancer include:
Acute gastroduodenal endoscopy: is a measure to give a direct image of the lesion location and the cause of the bleeding. bleeding, and at the same time can coordinate hemostasis. Colonoscopy to look for hemorrhagic lesions Anemia: decreased red blood cells, decreased hemoglobin (Hb), decreased hematocrit (Hct). In addition, there may be coagulation disorders accompanied by thrombocytopenia, decreased PT,... Renal dysfunction: blood creatinine and blood urea are elevated in case of severe blood loss. CT scan of the abdomen, magnetic resonance or PET/CT to determine the cause and metastatic lesions. Other tests include: blood group, HIV, HbsAg...

Need to perform differential diagnosis of gastrointestinal bleeding in the following cases:
Bleeding gums. Bleeding in the oropharynx, coughing up blood: the patient may cough up blood, then swallow and then vomit again. Cases of using iron-containing drugs, licorice causing black stools, or taking rifampicin causing red stools, ...

Many types of cancer can cause gastrointestinal bleeding, so a diagnosis should be made to find the cause:
Esophageal cancer. Stomach-intestinal cancer. Bile duct cancer. Liver cancer with dilated or ruptured esophageal veins. Colon and rectal cancer. Cancer of the anal canal.

Hemodynamic instability: manifestations include cold extremities, pale skin and mucous membranes, orthostatic hypotension, hemorrhagic shock (systolic blood pressure <90 mmHg or a decrease of more than 40 mmHg compared with systolic blood pressure in hypertensive patients), urinary oliguria <30ml/hour, irritability and even coma due to cerebral ischemia). An estimated blood loss of more than 500ml or a transfusion of >5 units of blood in 24 hours is required to ensure hemodynamics. The patient has bright red bleeding when inserting a gastric tube or passing red blood in the stool, which is a serious sign. Hematocrit <0.2L/L, red blood cells <2.0T/L, hemoglobin <70G/L. Some factors increase the severity: >60 years old, heart failure In summary, gastrointestinal bleeding includes high and low gastrointestinal bleeding due to cancer such as esophageal cancer, gastrointestinal cancer, cancer. anal, colorectal cancer, ... This is a medical emergency, the cause of bleeding is due to damage to blood vessels, tumors of the gastrointestinal tract or biliary tract, liver causing a syndrome clinical acute blood loss. If not treated promptly, the patient may die in the setting of hypovolemic shock.