In a 60-year-old woman with massive maroon-colored stool, pallor, tachycardia, and a soft, non‑tender abdomen, what is the most appropriate next diagnostic and therapeutic intervention?

Management of Acute Massive Lower Gastrointestinal Bleeding with Hemodynamic Instability

In this 60-year-old woman with massive maroon-colored stool, pallor, and tachycardia (indicating hemodynamic instability with shock index >1), CT angiography should be performed immediately as the first diagnostic test, followed by catheter-directed embolization if a bleeding source is identified—colonoscopy is contraindicated in unstable patients and nasogastric tube placement is unnecessary when maroon stool indicates a lower GI source. 1, 2

Immediate Hemodynamic Assessment and Resuscitation

• Calculate the shock index immediately (heart rate ÷ systolic blood pressure)—a value >1 defines hemodynamic instability and predicts poor outcomes requiring ICU admission 1, 2
• Initiate aggressive IV fluid resuscitation with crystalloids (normal saline or Ringer's lactate) to normalize blood pressure and heart rate before any diagnostic procedure 3, 1
• Use restrictive transfusion thresholds: maintain hemoglobin >7 g/dL for patients without cardiovascular disease, or >8-9 g/dL for those with cardiovascular disease or massive bleeding 3, 1
• Correct coagulopathy immediately: transfuse fresh frozen plasma if INR >1.5 and platelets if platelet count <50,000/µL 3, 2

Why Each Answer Choice Is Right or Wrong

B. Angiography (CORRECT)

CT angiography is the single most appropriate initial diagnostic intervention for this hemodynamically unstable patient 1, 2:

• CTA detects active bleeding with 94% sensitivity and can identify bleeding rates as low as 0.3 mL/min, making it the fastest and least invasive localization tool 1, 2
• CTA requires no bowel preparation, allowing immediate diagnosis in unstable patients who cannot tolerate colonoscopy preparation 2
• Following positive CTA, catheter angiography with embolization should be performed within 60 minutes to achieve immediate hemostasis in 40-100% of cases 3, 1, 2
• Transcatheter embolization provides time to stabilize the patient and prepare the bowel if surgery ultimately becomes necessary 3, 2

C. Colonoscopy (INCORRECT)

Colonoscopy is explicitly contraindicated in hemodynamically unstable patients 1, 2:

• Colonoscopy requires 4-6 liters of polyethylene glycol bowel preparation over 3-4 hours, which is not feasible in unstable patients 2
• Sedation required for colonoscopy can worsen shock and hemodynamic instability 2
• Urgent colonoscopy (<24 hours) does not improve rebleeding, mortality, or length of stay compared to elective colonoscopy in stable patients 3, 2
• Colonoscopy should be reserved for hemodynamically stable patients (shock index ≤1) after adequate bowel preparation on the next available inpatient list 3, 2

**A. NGT (Nasogastric Tube) (INCORRECT)

Nasogastric tube placement is inappropriate in this clinical scenario 1, 2:

• Maroon-colored stool strongly indicates a lower GI source, making NGT placement unnecessary 3, 1, 2
• NGT should be reserved only when an upper GI source is strongly suspected—approximately 10-15% of severe hematochezia originates from the upper GI tract, but this typically presents with hematemesis, melena, or risk factors such as peptic ulcer disease or portal hypertension 1, 2, 4
• NGT lavage results can be misleading: clear fluid without bile does not reliably exclude upper GI bleeding 2
• Routine NGT placement does not improve clinical outcomes and is technically difficult in up to one-third of patients 2

D. Barium Enema (INCORRECT)

Barium enema has no role in acute lower GI bleeding management 5, 6:

• Barium enema is contraindicated in acute bleeding because it obscures subsequent CT angiography and angiographic visualization 6
• Barium enema cannot provide therapeutic intervention and delays definitive diagnosis 6
• Modern guidelines do not recommend barium studies for acute lower GI bleeding evaluation 5, 6

Diagnostic and Therapeutic Algorithm for Hemodynamically Unstable Lower GI Bleeding

Step 1: Immediate Resuscitation (Simultaneous with Diagnostic Workup)

• Calculate shock index (HR/systolic BP) 1, 2
• Initiate IV crystalloid resuscitation 3, 1
• Transfuse PRBCs to maintain Hb >7 g/dL (or >8-9 g/dL if cardiovascular disease) 3, 1
• Correct coagulopathy: FFP for INR >1.5, platelets for count <50,000/µL 3, 2

Step 2: Immediate CT Angiography

• Perform CTA immediately as the first diagnostic test in unstable patients (shock index >1) 1, 2
• CTA sensitivity 94% for active bleeding, detects rates as low as 0.3 mL/min 1, 2

Step 3: Catheter Angiography with Embolization (If CTA Positive)

• Proceed to catheter angiography within 60 minutes if CTA identifies bleeding source 3, 1, 2
• Embolization achieves immediate hemostasis in 40-100% of cases 3, 1, 2

Step 4: Upper Endoscopy (If CTA Negative for Lower GI Source)

• Perform upper endoscopy if CTA fails to identify lower GI bleeding, as 10-15% of severe hematochezia originates from upper GI tract 1, 2, 4

Step 5: Surgery (Last Resort Only)

• Surgery is indicated only after failure of endovascular control or when patient continues to deteriorate despite maximal resuscitation and angiographic attempts 3, 2
• Blind segmental resection or emergency subtotal colectomy without prior localization carries rebleeding rates up to 33% and mortality 33-57% 3, 2
• Emergency total colectomy mortality is 27-33% versus ~10% when bleeding is first localized 3, 2

Critical Pitfalls to Avoid

• Do not delay CTA to perform colonoscopy in unstable patients—this delays definitive localization and potential life-saving embolization 1, 2
• Do not assume maroon stool always indicates lower GI bleeding—up to 15% of severe hematochezia originates from upper GI tract, especially with hemodynamic instability, but maroon stool makes this less likely 1, 2, 4
• Do not proceed to laparotomy without attempting radiological localization—surgery without localization has prohibitively high mortality and rebleeding rates 3, 2
• Do not place NGT routinely—it is indicated only when upper GI source is strongly suspected based on clinical features (hematemesis, melena, peptic ulcer history, portal hypertension) 1, 2

Anticoagulation Management (If Applicable)

• If patient is on warfarin, interrupt immediately and reverse with prothrombin complex concentrate plus vitamin K for unstable hemorrhage 3, 2
• If patient is on aspirin for primary prophylaxis, permanently discontinue; if for secondary prevention, do not routinely stop and restart as soon as hemostasis is achieved 1, 2

Mortality Context

• Overall in-hospital mortality for lower GI bleeding is 3.4%, but rises to 18% for inpatient-onset bleeding and 20% for patients requiring ≥4 units of red cells 1, 2
• Mortality relates more to comorbidities than exsanguination, emphasizing the importance of aggressive management of underlying conditions 1, 7