What is the initial request and workup for a patient presenting with hematochezia (passage of fresh blood per anus), considering their age, past medical history, and potential underlying causes such as diverticulosis, angiodysplasia, inflammatory bowel disease, or colorectal cancer?

Initial Assessment and Workup for Hematochezia

Begin with immediate hemodynamic assessment including vital signs, complete blood count, coagulation parameters, and establish two large-bore IV access if severe bleeding is present. 1

Immediate Resuscitation and Stabilization

• Check vital signs immediately to assess hemodynamic stability—look for tachycardia (HR >100), hypotension (SBP <100 mmHg), or orthostatic changes indicating significant blood loss 1
• Obtain blood typing and cross-matching for patients showing signs of severe bleeding 1
• Draw initial laboratory tests: complete blood count (hemoglobin/hematocrit), serum electrolytes, BUN, creatinine, coagulation studies (PT/INR, aPTT), and albumin 2, 1
• Perform pregnancy testing in all women of childbearing age before any imaging or intervention 2, 1
• Establish two large-bore IV access (18-gauge or larger) for fluid resuscitation and potential blood product administration in severe bleeding 1
• Target hemoglobin >7 g/dL and mean arterial pressure >65 mmHg while avoiding fluid overload 1
• Insert urinary catheter to monitor hourly urine output (target >30 mL/hr) in severe cases 1

Critical History Elements

• Timing and character of bleeding: bright red blood versus maroon stools versus melena (10-15% of severe hematochezia originates from upper GI sources despite red appearance) 1, 3, 4
• Medication history: anticoagulants (warfarin, DOACs), antiplatelet agents (aspirin, clopidogrel), NSAIDs 2, 1
• Comorbidities: liver disease, portal hypertension, inflammatory bowel disease, prior radiation therapy, cardiovascular disease 2, 1
• Red flag symptoms: unexplained weight loss ≥5 kg, iron deficiency anemia, fever, severe abdominal pain, or systemic symptoms 5
• Personal and family history: colorectal cancer, polyps, inflammatory bowel disease, diverticulosis 2

Physical Examination

• Digital rectal examination is mandatory to assess for anorectal pathology (hemorrhoids, fissures, masses), confirm presence of blood, and evaluate stool color 2, 1, 5
• Anoscopy should be performed as part of the physical examination whenever feasible and well tolerated 2
• Abdominal examination: assess for tenderness, masses, peritoneal signs, or stigmata of liver disease 1

Risk Stratification

Apply risk stratification scores that incorporate vital signs, hemodynamic parameters, presence of blood on rectal exam, laboratory values (hematocrit, creatinine, albumin), comorbidities, and anticoagulant/antiplatelet use 2

Diagnostic Algorithm

For Hemodynamically Stable Patients:

1. Urgent colonoscopy within 24 hours is the first-line diagnostic approach after hemodynamic stabilization 1
2. Ensure thorough bowel preparation to improve visualization—poor preparation leads to incomplete evaluation and missed lesions 1
3. Consider upper endoscopy first if there are risk factors for upper GI bleeding (hemodynamic instability, history of peptic ulcer disease, liver disease) since 10-15% have an upper GI source 1, 3, 4

For Hemodynamically Unstable Patients:

1. CT angiography may be performed first to rapidly localize the bleeding site before endoscopy 1
2. Upper endoscopy should be performed early to exclude an upper GI source in patients with severe hematochezia and hypovolemia 3

If Initial Colonoscopy is Inconclusive:

1. Repeat colonoscopy with thorough bowel preparation if initial study suggests bleeding around the ileocecal valve 1
2. Radionuclide imaging with 99Tcm-labeled red blood cells can detect active bleeding at rates of 0.1-0.5 mL/min 1
3. Angiography should be performed only after positive scintigraphy or in patients with severe unremitting bleeding (requires bleeding rate ≥1 mL/min for detection) 1

Imaging Considerations

• CT scan, MRI, or endoanal ultrasound should only be performed if there is suspicion of concomitant anorectal disease (abscess, inflammatory bowel disease, neoplasm) 2, 1
• Medical history and physical examination are key factors driving diagnostic workup, as imaging has limited role in uncomplicated hemorrhoidal bleeding 1

Critical Pitfalls to Avoid

• Never delay resuscitation to perform diagnostic procedures—stabilization takes absolute priority 1
• Never attribute hematochezia to hemorrhoids without complete colonic evaluation—hemorrhoids alone do not cause positive fecal occult blood tests, and anemia from hemorrhoidal disease is rare (0.5 per 100,000 population) 3, 5
• Avoid inadequate bowel preparation leading to poor visualization during colonoscopy 1
• Avoid over-transfusion, which may increase portal pressure and potentially worsen bleeding in patients with portal hypertension 1
• Do not prematurely resort to surgery without attempting to localize bleeding through radiological and/or endoscopic modalities first 1
• Correct any coagulopathy before invasive procedures 1