Lower Gastrointestinal Bleeding

Introduction

Lower gastrointestinal bleeding (LGIB) is a common and potentially life-threatening condition that Canadian medical students must thoroughly understand for the MCCQE1 exam. This comprehensive guide will cover the essential aspects of LGIB, focusing on Canadian guidelines and practices to help you excel in your MCCQE1 preparation.

Epidemiology in the Canadian Context

Understanding the epidemiology of LGIB in Canada is vital for MCCQE1 preparation:

• Incidence: Approximately 33 per 100,000 person-years in Canada
• Age: More common in older adults (>65 years)
• Gender: Slightly more prevalent in males
• Risk factors specific to the Canadian population:
  • Increased prevalence in Indigenous populations
  • Higher rates in urban areas compared to rural regions

Etiology

Understanding the common causes of LGIB is crucial for MCCQE1 success. Here's a mnemonic to help you remember the most frequent etiologies:

"DIAPERS"

• Diverticular disease
• Ischemic colitis
• Angiodysplasia
• Polyps/neoplasms
• Enteritis (inflammatory bowel disease)
• Radiation proctitis
• Small bowel sources

Clinical Presentation

Recognizing the clinical presentation of LGIB is essential for the MCCQE1 exam:

1. Hematochezia (bright red blood per rectum)
2. Maroon stools
3. Melena (less common, usually indicates upper GI source or right-sided colonic bleeding)
4. Associated symptoms:
   • Abdominal pain
   • Change in bowel habits
   • Weakness, dizziness, or syncope (in severe cases)

Diagnostic Approach

A systematic diagnostic approach is crucial for managing LGIB effectively:

Management

The management of LGIB should follow Canadian guidelines and practices:

1. Resuscitation: Prioritize hemodynamic stability

   • IV fluid resuscitation
   • Blood transfusion if necessary (target Hb >70 g/L)

2. Medical Management:

   • Correct coagulopathy if present
   • Consider proton pump inhibitors (PPIs) if upper GI source suspected

3. Endoscopic Management:

   • Colonoscopy within 24 hours of presentation (after adequate bowel prep)
   • Therapeutic options: clip placement, thermal coagulation, injection therapy

4. Interventional Radiology:

   • Angiographic embolization for persistent bleeding

5. Surgical Management:

   • Reserved for cases refractory to other treatments or specific indications (e.g., cancer)

Complications and Prognosis

Understanding potential complications and prognosis is crucial for comprehensive patient care:

• Hypovolemic shock
• Acute kidney injury
• Recurrent bleeding (occurs in 10-40% of cases)
• Mortality rate: 2-4% (higher in elderly patients and those with comorbidities)

Key Points to Remember for MCCQE1

1. LGIB is more common in older adults and slightly more prevalent in males in Canada.
2. The "DIAPERS" mnemonic helps recall common etiologies.
3. Hematochezia is the most common presentation, but melena can occur with right-sided colonic bleeding.
4. Early colonoscopy (within 24 hours) is recommended by Canadian guidelines.
5. The Oakland Score can be used for risk stratification in LGIB.
6. Management prioritizes hemodynamic stability, followed by diagnostic and therapeutic interventions.
7. Consider population health aspects, such as higher prevalence in Indigenous populations and urban areas.

Sample Question

# Sample Question

A 68-year-old man presents to the emergency department with bright red blood per rectum for the past 6 hours. He has a history of hypertension and diabetes. His vital signs show BP 100/60 mmHg, HR 110 bpm, and RR 18/min. Physical examination reveals pale conjunctiva and bright red blood on digital rectal exam. Laboratory results show Hb 85 g/L and BUN 8 mmol/L. Which one of the following is the most appropriate next step in management?

- [ ] A. Immediate colonoscopy
- [ ] B. CT angiography
- [ ] C. Intravenous fluid resuscitation and blood transfusion
- [ ] D. Nuclear scintigraphy
- [ ] E. Urgent surgical consultation

Explanation

The correct answer is:

• C. Intravenous fluid resuscitation and blood transfusion

Explanation: In this case of acute lower gastrointestinal bleeding, the patient shows signs of hemodynamic instability (tachycardia and hypotension) and significant anemia (Hb 85 g/L). The most appropriate initial step is to stabilize the patient with intravenous fluid resuscitation and blood transfusion. This aligns with Canadian guidelines, which prioritize hemodynamic stability before proceeding with diagnostic interventions.

Options A (immediate colonoscopy) and B (CT angiography) are premature without first stabilizing the patient. Option D (nuclear scintigraphy) is not typically a first-line investigation in acute LGIB. Option E (urgent surgical consultation) may be necessary later but is not the most appropriate initial step.

Canadian Guidelines

The Canadian Association of Gastroenterology (CAG) provides specific guidelines for managing LGIB:

1. Early risk stratification using validated tools (e.g., Oakland Score)
2. Colonoscopy within 24 hours of presentation for most patients
3. Use of CT angiography as the first-line radiological investigation for patients with active bleeding
4. Consideration of angiographic embolization before surgery in patients with positive CT angiography

References

1. Strate, L. L., & Gralnek, I. M. (2016). ACG Clinical Guideline: Management of Patients With Acute Lower Gastrointestinal Bleeding. The American Journal of Gastroenterology, 111(4), 459-474.

2. Barkun, A. N., Almadi, M., Kuipers, E. J., et al. (2019). Management of Nonvariceal Upper Gastrointestinal Bleeding: Guideline Recommendations From the International Consensus Group. Annals of Internal Medicine, 171(11), 805-822.

3. Oakland, K., Jairath, V., Uberoi, R., et al. (2019). Derivation and validation of a novel risk score for safe discharge after acute lower gastrointestinal bleeding: a modelling study. The Lancet Gastroenterology & Hepatology, 4(9), 704-714.

4. Canadian Association of Gastroenterology. (2018). Clinical Practice Guidelines for the Management of Nonvariceal Upper Gastrointestinal Bleeding. Journal of the Canadian Association of Gastroenterology, 1(2), 47-58.

5. Statistics Canada. (2021). Health Characteristics, Annual Estimates. Retrieved from https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310009601 (opens in a new tab)