What is the differential diagnosis and plan of care for an 82-year-old patient presenting with melena (black stools) and abdominal pain?

Differential Diagnosis and Management for 82-Year-Old Female with Black Stools and Abdominal Pain

This patient requires immediate CT scan with IV contrast and urgent hospitalization given the high-risk presentation of melena with abdominal pain in an elderly patient, where mortality can reach 30-90% if serious pathology is missed. 1, 2

Critical Initial Assessment

Obtain immediate vital signs and assess for hemodynamic instability, as elderly patients with abdominal pain often present with deceptively benign physical examinations even with catastrophic conditions. 3 The combination of melena (black stools) and abdominal pain in an 82-year-old demands urgent evaluation for:

High-Priority Life-Threatening Diagnoses

• Upper GI bleeding with hemodynamic compromise - melena indicates upper GI source or slow right colon bleeding 1
• Mesenteric ischemia - presents with pain out of proportion to examination findings and carries 30-90% mortality if missed 2
• Perforated viscus - including perforated peptic ulcer, diverticulitis, or malignancy 4
• Bowel obstruction with ischemia - adhesions, hernias, or malignancy causing obstruction in 90% of small bowel cases 4

Common Diagnoses in This Age Group

• Diverticulitis (left-sided most common) - responsible for ~30% of large bowel pathology in elderly 4
• Colorectal cancer - accounts for 60% of large bowel obstructions 4, 1
• Ischemic colitis - particularly in patients with cardiovascular risk factors 4, 1
• Peptic ulcer disease with bleeding - especially if NSAID use 1
• Inflammatory bowel disease - up to 15% of new IBD diagnoses occur after age 60 4, 1

Less Common but Important Considerations

• Small bowel lymphoma - can present with pain, weight loss, and melena 5
• Angiodysplasia with bleeding - common in elderly 1
• Medication-induced colitis (including collagenous colitis) - can rarely present acutely with melena 6

Immediate Diagnostic Workup

Laboratory Tests (Obtain Immediately)

• Complete blood count - assess for anemia and leukocytosis 4, 1
• Comprehensive metabolic panel - evaluate renal function, electrolytes, and liver enzymes 4
• Coagulation studies - PT/INR if on anticoagulation 1
• Lactate level - elevated in mesenteric ischemia or sepsis 2
• Type and cross-match - prepare for potential transfusion 1
• Stool for Clostridium difficile - mandatory in all elderly patients with diarrhea regardless of antibiotic history 4, 1

Imaging (Priority Based on Clinical Presentation)

CT scan with IV contrast is the gold standard imaging modality for this presentation - it evaluates for diverticulitis, perforation, ischemia, obstruction, and malignancy with high sensitivity and specificity. 4, 1, 2

• If patient cannot receive IV contrast due to renal disease or allergy, use ultrasound, MRI, or non-contrast CT as alternatives 4
• CT angiography specifically if mesenteric ischemia suspected (pain out of proportion to exam, elevated lactate) 2

Do not delay imaging for endoscopy in an unstable patient or when surgical pathology is suspected. 1

Initial Management Plan

Resuscitation and Stabilization

• NPO status immediately 4
• Two large-bore IV lines for resuscitation 1
• Aggressive IV fluid resuscitation with crystalloids 1
• Blood transfusion if hemoglobin <7 g/dL or symptomatic anemia 1
• Nasogastric tube placement if bowel obstruction or severe vomiting 4
• Foley catheter to monitor urine output 1

Empiric Treatment Pending Imaging

• Hold anticoagulation/antiplatelet agents if active bleeding 1
• Proton pump inhibitor IV (e.g., pantoprazole 80mg bolus then 8mg/hr infusion) for presumed upper GI bleeding 1
• Broad-spectrum antibiotics if fever, leukocytosis, or peritoneal signs suggest infection (covers gram-negatives and anaerobes) 4

Consultation Strategy

• Immediate surgical consultation - elderly patients with abdominal pain and melena require early surgical evaluation given high morbidity/mortality 3
• Gastroenterology consultation for endoscopy once stabilized if upper GI bleeding confirmed 1
• Interventional radiology if abscess drainage or angiography needed 4

Disposition Based on CT Findings

If Uncomplicated Diverticulitis (WSES Stage 0)

• Outpatient management possible in immunocompetent patients without sepsis 4
• Avoid antibiotics if no systemic signs 4

If Complicated Diverticulitis (Abscess, Perforation)

• Hospital admission mandatory 4
• Broad-spectrum antibiotics for 3-5 days after source control 4
• Percutaneous drainage if abscess >4cm 4
• Urgent surgery if diffuse peritonitis (WSES stage 3-4) 4

If Bowel Obstruction

• Hospital admission with surgical consultation 4
• Conservative management initially unless signs of ischemia or perforation 4

If Mesenteric Ischemia or Perforation

• Immediate operative intervention - delay increases mortality dramatically 2

If Upper GI Bleeding Source

• ICU admission if hemodynamically unstable 1
• Urgent endoscopy within 24 hours for risk stratification and intervention 1

Critical Pitfalls to Avoid

• Do not be falsely reassured by benign physical examination - elderly patients often have minimal peritoneal signs even with perforation or ischemia 3
• Do not attribute symptoms to "gastroenteritis" without imaging in elderly patients with abdominal pain 3
• Do not delay imaging - older patients are triaged as "emergent" at only half the rate of younger patients despite higher surgical rates 7
• Do not discharge without colonoscopy follow-up - early colonic evaluation is essential after acute episode to exclude malignancy 4, 1