Chemotherapy is a systemic treatment designed to target rapidly dividing cells, making it a powerful tool in cancer care. Chemotherapy can cause gastrointestinal (GI) bleeding, a potentially serious complication stemming from several mechanisms. Any instance of blood in the stool during treatment requires immediate medical review from the oncology team.
Chemotherapy’s Direct Impact on the Digestive Tract
Chemotherapy agents attack fast-growing cells, including the healthy cells lining the GI tract. This non-selective targeting causes gastrointestinal mucositis, the direct toxic effect of the drugs on the digestive lining. Chemotherapy drugs induce DNA damage and cell death in the basal-epithelial cells responsible for renewing the mucosal surface. This destruction of the intestinal villi and the inability to repair the barrier results in inflammation and ulceration throughout the digestive system.
When the protective mucosal lining breaks down, open sores form that can bleed, causing blood to appear in the stool. If bleeding originates higher up, the blood may be digested and appear as black, tarry stools (melena). Bleeding lower down, such as in the colon or rectum, typically presents as bright red or maroon blood mixed with the stool or on the toilet paper.
Another significant mechanism contributing to bleeding is chemotherapy-induced thrombocytopenia (CIT), a reduction in the number of platelets. Chemotherapy suppresses the bone marrow where platelets are produced, decreasing the blood’s ability to clot. Cytotoxic agents are known to suppress megakaryocyte progenitors, leading to elevated bleeding risks. With a low platelet count, even minor GI tract injuries caused by mucositis can bleed more heavily and persistently.
Other Possible Sources of Gastrointestinal Bleeding
Bleeding in a patient undergoing chemotherapy can also stem from other causes exacerbated by the therapy itself. Common mechanical issues, such as hemorrhoids and anal fissures, frequently cause bright red blood in the stool. Chemotherapy often causes severe diarrhea or constipation, which strains the bowel and worsens these pre-existing conditions, leading to bleeding. While this type of bleeding is usually minor, it must still be reported to the healthcare team for proper assessment.
A more serious indirect cause of bleeding is neutropenic enterocolitis, also known as typhlitis, which involves infection and inflammation of the bowel wall. Chemotherapy often causes neutropenia, a severe drop in the white blood cell count that highly compromises the immune system. In this state, bacteria or viruses can invade the damaged mucosal lining, causing severe inflammation, ulceration, and hemorrhage in the colon. This condition is characterized by fever, abdominal pain, and bloody diarrhea, requiring immediate, aggressive medical intervention.
Gastrointestinal bleeding may also signal disease progression, depending on the patient’s underlying cancer type. If the primary tumor or a metastatic site is located within the GI tract, bleeding could indicate the growth or recurrence of the malignancy. Determining the source of the hemorrhage requires a thorough evaluation to differentiate between drug toxicity, infection, and disease activity.
When Immediate Medical Attention is Necessary
Any instance of blood in the stool during chemotherapy must be treated as a medical emergency requiring immediate contact with the oncology care team. Patients risk severe complications, such as sepsis from infection or uncontrolled hemorrhage due to suppressed bone marrow function. Waiting for the symptom to resolve is not advised, as early treatment prevents escalation into a life-threatening crisis.
Specific warning signs require an immediate visit to the emergency room for professional assessment and intervention:
- Passing a large volume of blood.
- Experiencing black or tarry stools (melena).
- Feeling symptoms of significant blood loss, such as dizziness or faintness.
- A fever of \(100.4\) degrees Fahrenheit or higher, especially combined with abdominal pain or bloody diarrhea, signaling a potential severe infection.
When seeking care, clearly communicate the color and amount of blood, whether it is mixed with stool or on the toilet paper, and any accompanying symptoms. Due to the high risk of severe infection and rapid decline in an immunocompromised patient, the medical team often initiates broad-spectrum antibiotics and supportive care immediately. Prompt intervention manages the bleeding, stabilizes the patient, and reduces the risk of complications that could interrupt the cancer treatment schedule.