Lower Gastrointestinal Bleeding (LGIB)
Introduction to LGIB for MCCQE1
Lower Gastrointestinal Bleeding is defined as blood loss originating from a site distal to the Ligament of Treitz. For the MCCQE1, understanding the approach to a patient with GI bleeding is a high-yield topic falling under the Medical Expert CanMEDS role. It requires a systematic approach involving rapid assessment of hemodynamic stability, resuscitation, and localization of the bleeding source.
Canadian Context: In Canada, LGIB accounts for approximately 20-30% of all major gastrointestinal bleeding episodes. The incidence increases significantly with age, a crucial factor given Canada’s aging population demographics.
Anatomic Definition
The Ligament of Treitz
The suspensory muscle of the duodenum marks the boundary between the Upper GI tract and the Lower GI tract.
- Upper GI Bleed (UGIB): Esophagus, stomach, duodenum.
- Lower GI Bleed (LGIB): Jejunum, ileum, colon, rectum, anus.
Etiology and Differential Diagnosis
For MCCQE1 preparation, it is essential to categorize causes based on patient demographics. The most common cause of significant LGIB in adults is diverticulosis.
Adults (>60 years)
Most Common Causes in the Elderly:
- Diverticulosis: (30-50%) Painless, hematochezia.
- Angiodysplasia: (20-30%) Painless, often right-sided (cecum/ascending colon).
- Malignancy: Colon cancer or polyps.
- Ischemic Colitis: Painful, bloody diarrhea, often in patients with cardiovascular risk factors.
Clinical Presentation
The clinical presentation guides the urgency of management.
- Hematochezia: Bright red blood per rectum (BRBPR). Indicates a lower GI source or a massive upper GI bleed with rapid transit.
- Maroon stools: Suggests right-sided colonic bleed or small bowel bleed.
- Melena: Black, tarry stools. Usually indicates UGIB (blood digested by acid), but can occur in slow small bowel or right-sided colonic bleeds.
Differentiating UGIB from LGIB
| Feature | Upper GI Bleed | Lower GI Bleed |
|---|---|---|
| Stool Appearance | Melena (90%), Hematochezia (if massive) | Hematochezia (90%), Melena (rare) |
| Nasogastric Lavage | Bloody or Coffee grounds | Clear or Bilious |
| BUN:Creatinine Ratio | Elevated (>30:1) due to blood digestion | Normal (<20:1) |
| Bowel Sounds | Hyperactive | Normal |
Management Approach for MCCQE1
The MCCQE1 emphasizes a prioritized approach: Resuscitation first, Diagnosis second.
Step 1: Initial Resuscitation (ABCs)
Assess hemodynamic stability immediately.
- Airway/Breathing: Protect airway if LOC is decreased.
- Circulation:
- Establish 2 large-bore IVs (18G or larger).
- Fluid resuscitation with crystalloids (Ringer’s Lactate or Normal Saline).
- Crossmatch blood products.
- Transfuse Packed Red Blood Cells (PRBCs) if Hemoglobin <70 g/L (or <80 g/L in patients with CAD).
- Correct coagulopathy (FFP, Platelets) if necessary.
Step 2: History and Physical Exam
While resuscitating, gather focused data.
- History: NSAID/aspirin use, anticoagulants, previous GI bleeds, liver disease, abdominal pain, weight loss.
- Physical:
- Digital Rectal Exam (DRE) is mandatory. Inspect for hemorrhoids, fissures, masses, and stool color.
- Abdominal exam for tenderness (ischemia/perforation) or masses.
Step 3: Rule Out Upper GI Bleed
10-15% of patients with severe hematochezia have an Upper GI source.
- If the patient is hemodynamically unstable, an Esophagogastroduodenoscopy (EGD) should be considered before colonoscopy to rule out a brisk UGIB.
- Nasogastric (NG) tube lavage is controversial but may be used to assess for blood in the stomach.
Step 4: Diagnostic Imaging & Intervention
The choice depends on the rate of bleeding and stability.
-
Stable Patient:
- Colonoscopy: The gold standard. Should be performed within 24 hours of presentation after adequate bowel preparation (rapid purge). Allows for therapeutic intervention (clipping, epinephrine injection, cautery).
-
Unstable Patient / Massive Bleed:
- CT Angiography (CTA): Rapid, non-invasive. Detects bleeding rates >0.3-0.5 mL/min. Can localize the site for interventional radiology.
- Angiography (Interventional Radiology): Diagnostic and therapeutic (embolization). Detects bleeding >0.5 mL/min. Used if colonoscopy fails or is feasible due to instability.
- Tagged RBC Scan (Nuclear Medicine): Detects very slow bleeding (0.1-0.5 mL/min). Less precise localization; generally used when other modalities fail to find the source.
Surgical Intervention
Surgery (segmental colectomy) is a last resort, reserved for patients who:
- Require massive transfusions (>4-6 units/24h).
- Have recurrent bleeding despite endoscopic/angiographic therapy.
- Have a clear bleeding site identified (blind subtotal colectomy has high morbidity).
Canadian Guidelines (CAG)
The Canadian Association of Gastroenterology (CAG) provides specific recommendations often tested on the MCCQE1:
- Risk Stratification: Use clinical scores (e.g., Oakland Score) to determine if outpatient management is safe for minor bleeds.
- Timing of Colonoscopy: For patients admitted with serious LGIB, colonoscopy should be performed within 24 hours.
- Bowel Prep: Oral PEG (polyethylene glycol) solution is preferred over enemas for better visualization.
- Anticoagulation: In patients on anticoagulants (Warfarin, DOACs), a multidisciplinary decision regarding reversal and resumption is required. Generally, hold the agent during the acute phase.
High-Yield Mnemonics for MCCQE1
To remember the causes of LGIB, use the mnemonic H-DRAIN:
- H - Hemorrhoids
- D - Diverticulosis (Most common major bleed)
- R - Radiation colitis / Rectal ulcers
- A - Angiodysplasia
- I - Infectious / Inflammatory / Ischemic colitis
- N - Neoplasm / Polyps
Key Points to Remember for MCCQE1
Exam Checklist
- ✅ Hemodynamic stability dictates the initial management (Resuscitate before Diagnosing).
- ✅ Diverticulosis is the #1 cause of LGIB; it is usually painless.
- ✅ Ischemic colitis presents with abdominal pain and bloody diarrhea, typically at “watershed” areas (splenic flexure).
- ✅ Rule out a massive Upper GI Bleed in patients with hemodynamic instability and hematochezia.
- ✅ Colonoscopy is the diagnostic and therapeutic modality of choice for stable patients.
- ✅ Do not forget the Digital Rectal Exam (DRE).
Sample Question
Clinical Scenario
A 72-year-old male presents to the Emergency Department with a 4-hour history of passing large amounts of bright red blood per rectum. He denies abdominal pain, nausea, or vomiting. His past medical history is significant for hypertension and constipation.
On examination, he appears pale. Vitals:
- BP: 100/60 mmHg
- HR: 110 bpm
- RR: 18/min
- Temp: 37.0°C
The abdomen is soft and non-tender with no masses. Rectal examination reveals bright red blood and clots but no anal fissures or hemorrhoids. Initial hemoglobin is 95 g/L. Two large-bore IVs are established, and fluid resuscitation is initiated.
Which one of the following is the most likely diagnosis?
Options
- A. Ischemic colitis
- B. Diverticulosis
- C. Angiodysplasia
- D. Colorectal cancer
- E. Internal hemorrhoids
Explanation
The correct answer is:
- B. Diverticulosis
Detailed Explanation: This clinical scenario describes a classic presentation of a diverticular bleed.
- Key Features: The patient is elderly (>60 years), presenting with significant, painless hematochezia. Diverticulosis is the most common cause of significant lower GI bleeding in this age group. The bleeding is arterial and can be brisk, leading to hemodynamic instability (tachycardia, borderline hypotension).
- Why A is incorrect: Ischemic colitis typically presents with abdominal pain (cramping) followed by bloody diarrhea. This patient has a painless abdomen.
- Why C is incorrect: Angiodysplasia is a common cause of LGIB in the elderly but usually presents with lower volume, venous oozing (melena or maroon stool) or occult bleeding causing anemia, rather than a massive acute bleed with clots, though it is a possibility. Diverticulosis is statistically more likely for massive acute bleeding.
- Why D is incorrect: Colorectal cancer usually presents with occult bleeding, anemia, change in bowel habits, or weight loss. Massive acute hemorrhage is a rare initial presentation for cancer.
- Why E is incorrect: While internal hemorrhoids cause painless bleeding, it is typically small volume (coating the stool or on toilet paper) and rarely causes hemodynamic instability or massive clot passage.
References
- Medical Council of Canada. MCCQE Part I Objectives: Gastrointestinal Bleeding. Available at: mcc.ca
- Barkun, A. N., et al. (2018). Management of Nonvariceal Upper Gastrointestinal Bleeding: Guideline Recommendations From the International Consensus Group. Annals of Internal Medicine. (Relevance: General approach to GI bleeding).
- Canadian Association of Gastroenterology. Clinical Practice Guidelines.
- Toronto Notes 2024. Gastroenterology: Lower Gastrointestinal Bleeding.
- Strate, L. L., & Gralnek, I. M. (2016). ACG Clinical Guideline: Management of Patients With Acute Lower Gastrointestinal Bleeding. American Journal of Gastroenterology. (Widely adopted in Canadian practice).