Chemotherapy-Induced Diarrhoea
Grading, emergency recognition, and clinical management of CID in oncology patients
Chemotherapy-induced diarrhoea (CID) affects up to 80% of patients receiving certain cancer treatment regimens and is one of the most common reasons for dose delays, reductions, and hospitalisation. Early recognition, accurate grading, and prompt management are essential to prevent life-threatening dehydration, electrolyte disturbance, and neutropenic sepsis.
What is Chemotherapy-Induced Diarrhoea?
CID results from direct cytotoxic damage to the intestinal mucosa, disrupting the normal balance of secretion and absorption in the gut. The small and large bowel epithelium has a high cell turnover rate, making it particularly susceptible to chemotherapy agents. Irinotecan causes both early (cholinergic) and late diarrhoea — the late phase (starting >24 hours after treatment) is the most clinically dangerous. Fluorouracil (5-FU) and capecitabine also commonly cause significant CID. Targeted therapies including EGFR inhibitors (cetuximab, erlotinib) are increasingly recognised causes of treatment-related diarrhoea.
Grading Severity
Standardised grading using the CTCAE v5 (Common Terminology Criteria for Adverse Events) scale guides treatment decisions. Grade 1: fewer than 4 stools per day above baseline — manage at home with loperamide and dietary modification. Grade 2: 4 to 6 stools per day above baseline — loperamide, close monitoring, oncology contact. Grade 3: 7 or more stools per day above baseline, or incontinence, or limiting self-care activities — hospital admission required. Grade 4: life-threatening consequences (haemodynamic instability, ischaemic colitis, perforation) — ITU admission. Any diarrhoea in the context of fever or neutropenia is treated as a medical emergency regardless of grade.
Emergency Recognition
The combination of diarrhoea and fever in a patient receiving chemotherapy must be treated as neutropenic sepsis until proven otherwise. A full blood count to check neutrophil count is mandatory. Stool culture should be sent to exclude infectious causes, including Clostridioides difficile — particularly if the patient has recently received antibiotics or been hospitalised. Severe dehydration can develop rapidly with high-volume diarrhoea, leading to acute kidney injury, hypotension, and electrolyte disturbance. A careful evaluation of fluid status, electrolytes, renal function, and clinical observations determines whether hospital admission and intravenous treatment are needed. Blood in the stool is a red flag requiring urgent oncological review.
Management & Patient Guidance
Loperamide remains the cornerstone of outpatient management for uncomplicated Grade 1-2 CID. Patients should be counselled to start it early, at full doses (4 mg initially, then 2 mg after each loose stool, maximum 16 mg/day), and to continue until they have been diarrhoea-free for 12 consecutive hours. Oral rehydration with electrolyte-containing fluids is essential. Patients must avoid laxatives and stool softeners during treatment. Hospital admission for IV fluids, octreotide, and electrolyte replacement is required for Grade 3-4 or loperamide-refractory CID. Dietary advice includes the BRAT approach (bananas, rice, applesauce, toast), avoiding dairy, caffeine, and high-fibre foods, and maintaining meticulous perianal skin care to prevent breakdown.