Bloody Stool (hematochezia) and Vomiting Blood (hematemesis): A Practical Guide to Diagnosing GI Bleeding in Clinical Settings and OSCE

“I just noticed some bright red blood in the toilet bowl… but maybe it’s just hemorrhoids.”
“My stool looked pitch black this morning… could it be the squid ink I had for dinner?”

These assumptions can sometimes be fatal.

Hematemesis and hematochezia are not just alarming—they can be signs of serious gastrointestinal bleeding. In OSCE exams and real-world clinical settings, it’s essential to determine the bleeding source based on stool color, consistency, and timing.

In this article, we’ll explore how to differentiate upper and lower GI bleeding, identify red flags, and make confident decisions from the first patient interview to appropriate investigations.

• How to distinguish hematemesis, melena, and hematochezia: Learn to identify the bleeding site based on the color, timing, and consistency of blood in stool or vomit.
• Key differentials—from benign to life-threatening causes: Understand how to work through common causes like hemorrhoids or infections, while also recognizing red flags for cancer, ulcers, or ischemic colitis.
• OSCE-ready interview and diagnostic skills: Master history-taking, physical exams (including rectal exam), and the rationale for choosing tests like FOBT and endoscopy.

🚪 Doorway Information

• Age/Sex: 65-year-old male
• Chief Complaint: Bright red blood in the stool
• Vital Signs: BP 110/68 mmHg, HR 96/min, SpO₂ 98% (RA), Temp 37.2°C

🗣️ Patient’s First Words:
“This morning I went to the toilet and saw bright red blood floating in the bowl… I was really shocked. My stomach doesn’t hurt, but should I be worried?”

Faced with this kind of complaint, how would you approach the situation?
In the next section, let’s walk through how to begin reasoning from the first impression.

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When a patient reports “passing blood,” the first question is: Where is the bleeding coming from?
Simply knowing that blood was present isn’t enough—we must determine whether it’s from the upper GI tract (esophagus, stomach, duodenum), lower GI tract (colon, rectum), or the anal region (e.g., hemorrhoids).

🔍 Clues from Color, Consistency, and Timing

• Bright red blood (hematochezia): Suggests bleeding near the anus or rectum
• Dark red or maroon-colored blood: Likely from the right or transverse colon
• Black, tarry stool (melena): Indicates upper GI bleeding where blood has been digested
• Coffee-ground vomit: Suggests older upper GI bleeding

Additionally, ask whether the blood was coating the stool or mixed throughout. These details can offer critical clues about the bleeding site.

⚠️ Don’t Miss These Red Flags

• Use of NSAIDs or antiplatelet medications increases bleeding risk
• Even 200 mL of upper GI bleeding can present as melena—don’t rely solely on quantity
• A negative fecal occult blood test does not rule out upper GI bleeding
• Even if previously diagnosed with hemorrhoids, anemia progression warrants re-evaluation

Bottom line: The key is identifying where the bleeding originates—is it vomited blood or bloody stool? Is it fresh or digested? Are there associated symptoms like pain or fever?

Let’s now structure our differential diagnosis using the FPH (Fact–Problem–Hypothesis) model in the next section.

📌 Fact (What the patient told us):

• 65-year-old male
• Noticed bright red blood floating in the toilet this morning
• No abdominal pain or fever
• Blood was not mixed with stool, but rather on the surface
• Previously told he has hemorrhoids, but unclear about treatment history

🧩 Problem (How we reinterpret the facts clinically):

• Acute onset of painless rectal bleeding
• Bright red blood, floating on stool surface → suggests rectal or anal origin
• No systemic signs → low suspicion for infectious or inflammatory bowel disease
• Hemorrhoids in history, but must rule out other significant causes

🧠 Hypothesis (Differential diagnosis using the VITAMIN CDE framework):

• Neoplastic: Colorectal cancer, rectal cancer (bleeding may be first sign)
• Degenerative: Internal hemorrhoids, anal varices
• Infectious: Infectious colitis (e.g., Campylobacter, EHEC)
• Vascular: Ischemic colitis (especially in elderly or with atherosclerosis)
• Iatrogenic: GI bleeding due to NSAIDs or antiplatelet agents

🏆 Top 3 Differentials

1. Internal hemorrhoids (Degenerative): Most likely based on color, location, and history
2. Rectal cancer (Neoplastic): Must rule out as bleeding may be initial symptom
3. Infectious colitis (Infectious): Possible if recent travel or dietary risk factors are present

📖 NTK (Need To Know – Key information to ask next):

• HPI: Frequency and pattern of bleeding, stool consistency, and color changes
• PMH: Prior colonoscopy, history and treatment of hemorrhoids
• Medications: Use of NSAIDs, anticoagulants, antiplatelet agents
• Social history: Alcohol intake, diet, recent travel
• Family history: Colorectal cancer or inflammatory bowel disease

Even when symptoms appear typical for hemorrhoids, it’s essential to consider broader differentials and avoid premature closure. Next, let’s explore how to gather this information efficiently through targeted history taking.

The primary goal of history taking is to distinguish whether the bleeding originates from the upper gastrointestinal (GI) tract or the lower GI tract.
By asking the right questions about bleeding direction, color, and associated symptoms, we can narrow the differential.

🩸 Key Initial Questions

• Was the blood in vomit? → Hematemesis → Suggests upper GI bleeding
• Was the stool black and tarry? → Melena → Likely upper GI bleeding
• Bright red blood on the stool or toilet paper? → Hematochezia → Suggests lower GI bleeding (anal or rectal)
• Blood with diarrhea? → Consider infectious colitis or IBD
• Use of NSAIDs or antiplatelet drugs? → Raises concern for peptic ulcers
• Recent travel or consumption of raw food? → Raises suspicion for infectious causes

Based on these answers, we then tailor further questions depending on whether upper or lower GI bleeding is more likely.

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🔼 Suspected Upper GI Bleeding – Key History Points

🕵️‍♂️ OPQRST

• Onset: Was the vomiting sudden or gradual?
• Provocation: Occurs on an empty stomach? After meals? After taking NSAIDs?
• Quality: Fresh blood or coffee-ground appearance? Any foul odor?
• Region: Epigastric discomfort or burning?
• Severity: Amount of bleeding? Dizziness? Fatigue?
• Time course: Any preceding heartburn or appetite loss?

📋 PAM HITS FOSS

• Previous: History of gastric or duodenal ulcers? Use of PPIs?
• Medications: NSAIDs, antiplatelets, bisphosphonates, potassium chloride, steroids
• Surgery: History of gastric surgery (e.g., marginal ulcers post-anastomosis)
• Family: Helicobacter pylori or gastric cancer in family

💡 Tips: Gastric vs. Duodenal Ulcers

• Hunger pain → Duodenal ulcer
• Post-meal pain → Gastric ulcer
• Poor response to PPIs or frequent recurrence → Consider secondary ulcers or malignancy

📌 Column: Atypical Ulcers to Remember

• Cushing ulcer: After head trauma
• Curling ulcer: After severe burns
• Marginal ulcer: At surgical anastomosis sites

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🔽 Suspected Lower GI Bleeding – Key History Points

🕵️‍♂️ OPQRST

• Onset: When did it start? Sudden or gradual?
• Provocation: During defecation? After straining? Post-exercise?
• Quality: Bright red? Mucus mixed? Darker red?
• Region: Lower abdominal pain? Rectal pressure or urgency?
• Severity: Volume of bleeding? Symptoms of anemia like dizziness?
• Time course: One-time or recurrent episodes?

📋 PAM HITS FOSS

• Previous: Hemorrhoids, polyps, colonoscopy history
• Hospitalization: Past admissions for GI infections or IBD
• Medications: Recent antibiotic use (→ C. difficile colitis?)
• Family: History of colorectal cancer or IBD
• Social: Hygiene, raw food, travel abroad

💡 Tips: Signs of Infectious Colitis in History

• Travel-associated bloody diarrhea → Campylobacter, Shigella, EIEC
• Recent antibiotics → Consider pseudomembranous colitis (C. difficile)

📌 Column: What is Traveler’s Diarrhea?

Traveler’s diarrhea is acute infectious diarrhea that occurs after travel to developing countries. Common pathogens include ETEC, EIEC, Campylobacter, and Salmonella. The presence of fever, bloody/mucoid stools, and dehydration helps determine the need for antibiotics.

🧠 Mnemonic: SHiCE – Bloody Causes of Traveler’s Diarrhea

Use the mnemonic “SHiCE” to recall pathogens that can cause bloody diarrhea in returning travelers:

• Shigella
• Hi – Enterohemorrhagic or Enteroinvasive E. coli (EHEC/EIEC)
• Campylobacter
• Entamoeba histolytica

These organisms are more likely to cause dysentery-like symptoms and may require different management approaches.

History taking can help localize the bleeding source, but physical examination is essential to assess severity and detect any red flags. Focus on vital signs, signs of anemia, abdominal findings, and—most importantly—the rectal exam.

🩺 General Assessment – Is the Patient Stable?

• Vital signs: Hypotension, tachycardia, or low SpO₂ suggest hemodynamic instability
• Peripheral signs: Cold extremities, pallor, delayed capillary refill → peripheral hypoperfusion
• Conjunctival pallor: High sensitivity for Hb ≤ 9 g/dL; high specificity for Hb ≤ 7 g/dL¹
• Shock Index (SI): HR / SBP > 1.0 suggests ≥ 1L blood loss

🫀 Cardiac & Pulmonary Examination

• Functional systolic murmur: Can occur with significant anemia due to increased flow
• Tachypnea: May result from anemia, aspiration, or infection

🩻 Abdominal Examination

Carefully assess for localized tenderness to guide the search for bleeding sources:

• Rebound or guarding: May indicate ulcer perforation, ischemic colitis, or active inflammation
• Bowel sounds: Hyperactive in infectious colitis, hypoactive in paralytic ileus
• Right lower quadrant tenderness: Consider lesions at the ileocecal region (e.g., Yersinia, Crohn’s, TB, lymphoma)

📌 Column: Diseases Affecting the Ileocecal Region

• Infectious enterocolitis (e.g., Yersinia, Salmonella, intestinal TB)
• Crohn’s disease
• Intestinal tuberculosis
• Primary small intestinal lymphoma
• Appendicitis (as a differential)
• Adult intussusception (rare but critical)

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🔍 Digital Rectal Examination (DRE) – Often the Most Critical Step

DRE is the only physical exam that allows direct visualization of active or recent GI bleeding. It can provide real-time information about stool color, bleeding characteristics, and palpable lesions.

What to assess:

• Blood color: Bright red, dark red, or tarry?
• Stool consistency: Formed, watery, mucoid, or mixed with blood?
• Palpable mass or ulcer: Consider cancer or polyps
• Internal hemorrhoids: Most often found at 3, 7, and 11 o’clock in supine position

📝 Example documentation:

“A soft, non-tender mass palpated at 6 o’clock with trace fresh blood on glove.”

💡 Tips:

• Don’t underestimate the diagnostic value of what’s on the toilet paper or in the bowl
• If the patient has a photo of the stool, it can be very informative—ask gently if available

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🚩 Red Flags to Watch For

• Profuse bleeding: bright red toilet water, repeated large-volume bleeding
• Vital sign abnormalities: hypotension, tachycardia, SpO₂ drop
• Conjunctival pallor + orthostatic dizziness = acute anemia
• Palpable mass or ulcer on DRE
• Bloody stool with mucus = suspicious for IBD or malignancy

These red flags are critical for deciding whether urgent endoscopy or transfusion is needed.

¹ Saudek CD, et al. JAMA. 1993;270(8):969-971.

By this stage, your clinical hypotheses should be taking shape. Now it’s time to select the appropriate tests—guided not by routine, but by “What are we trying to confirm or rule out?”

🧪 Blood Tests: What to Focus On

• Hemoglobin (Hb), Hematocrit (Ht): Assess bleeding severity and progression of anemia
• WBC, CRP: Supportive evidence for infectious or inflammatory causes
• BUN / Creatinine: Elevated BUN alone may suggest upper GI bleeding due to protein absorption
• PT-INR, aPTT: Evaluate bleeding tendency, especially in patients on anticoagulants or suspected DIC
• Blood type & crossmatch: For transfusion preparation in high-risk or unstable patients

🖼️ Imaging and Endoscopy: When and What to Choose

• Suspected upper GI bleeding: Prioritize esophagogastroduodenoscopy (EGD)
• FOBT-positive or lower GI bleeding: Consider colonoscopy (CS)—may defer in cases of massive bleeding
• CT with contrast: May detect active bleeding, ischemia, vascular malformations, or tumors
• Stool culture: Indicated if blood is accompanied by diarrhea or fever → infectious colitis

📌 Column: FOBT – Usefulness and Pitfalls

• FIT (Immunochemical method): Detects human hemoglobin, high sensitivity, no dietary restrictions
• Guaiac-based test: Prone to false positives, affected by diet or iron supplements
• Limitations: Cannot localize bleeding, may be negative in upper GI bleeding
• Implication: Positive result warrants endoscopic evaluation even if asymptomatic

💡 Tips: Always Ask Yourself Before Ordering Tests

• What is your leading hypothesis?
• What do you need to confirm or exclude with this test?
• Is the patient stable enough for colonoscopy, or is CT preferred first?
• FOBT-positive in an asymptomatic elderly patient? → Rule out malignancy
• Black stool + elevated BUN? → Consider upper GI bleeding
• Bright red stool but negative CT? → Rectal exam + sigmoidoscopy may be necessary

Now that we’ve reviewed the step-by-step approach from history to investigations, let’s apply that to the original case.

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🟢 Step 1: History Taking

Doctor: “What brought you in today?”
Patient: “This morning, I saw bright red blood floating in the toilet. It wasn’t really mixed with the stool—more like sitting on top of it.”

That already points me toward a distal source—possibly rectal or anal. The bright red color and absence of abdominal pain or systemic symptoms help narrow it down. He also mentioned a history of hemorrhoids, though treatment history is unclear.

He denies NSAID or antiplatelet use. No fever, no diarrhea. No recent travel or suspicious meals.

• Fact: Bright red blood in the toilet, no pain, blood not mixed with stool, past hemorrhoids
• Problem: Acute, painless hematochezia → suggests rectal or anal bleeding
• Hypotheses: Internal hemorrhoids, rectal cancer (asymptomatic bleeding), infectious colitis (less likely due to lack of GI symptoms)

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🟡 Step 2: Physical Examination

Vitals were stable. No signs of anemia. Conjunctiva were pink, Shock Index under 1.0. No orthostatic dizziness or pallor.

Abdominal exam was unremarkable—no tenderness, no mass, no bowel changes.

Rectal exam revealed a soft, compressible hemorrhoid at 6 o’clock with trace bright red blood on the glove. No masses or ulcers were felt, and stool was formed without mucus.

So far, the findings are consistent with internal hemorrhoids. No red flags like anemia, constitutional symptoms, or palpable mass. But due to the patient’s age, I still want to rule out malignancy.

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🔴 Step 3: Tests & Imaging

We ordered labs to assess for anemia and inflammation. Results showed:

• Hb: 13.8 g/dL
• WBC & CRP: within normal range
• BUN/Cr: normal

Although the bleeding was mild and self-limited, we scheduled an outpatient colonoscopy considering his age and incomplete prior screening.

Colonoscopy confirmed Grade II internal hemorrhoids from the sigmoid colon to rectum. No other bleeding sources were found.

This case reinforces the importance of not assuming “just hemorrhoids.” Instead, we must carefully assess bleeding characteristics and patient risk factors before ruling out other causes. Even mild hematochezia in older adults deserves further investigation.

Once you’ve assessed the bleeding source and severity, the next clinical decision is: Can this patient be managed as an outpatient, or do they require specialist referral? Here are the criteria for referral and the minimum workup to complete before handing over.

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📤 Indications for Specialist Referral

• Significant bleeding: Recurrent hematemesis or hematochezia, unstable vitals, shock index > 1
• Red flags: Conjunctival pallor, orthostatic dizziness, palpable mass, weight loss, bloody mucus
• High-risk patients: Elderly, on anticoagulants, history of ulcers or cancer, immunocompromised
• Unexplained findings: Positive FOBT with no symptoms, or unclear bleeding source

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✅ Minimum Evaluation Before Referral

• Bloodwork: Hb, WBC, CRP, BUN/Cr, PT-INR, aPTT
• Digital rectal exam: Describe blood color, consistency, presence of masses or hemorrhoids—use clock face terminology
• FOBT: Even if asymptomatic, should be done when bleeding is suspected
• Medication review: NSAIDs, antiplatelets, anticoagulants, and PPI use

Completing these steps makes the referral smoother and ensures appropriate urgency and prioritization at the receiving facility.

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🏥 Outpatient Management Tips

• Don’t stop at “It’s probably hemorrhoids”—explain the need for follow-up testing clearly
• Instruct patients to track bleeding color, quantity, and associated symptoms if re-bleeding occurs
• Discuss signs of anemia to watch for: lightheadedness, fatigue, palpitations
• When recommending endoscopy, explain that it’s to exclude more serious causes, even if symptoms seem mild

🔎 If you’d like to learn more about how to assess and manage anemia in the outpatient setting, see our article:
“A Symptom-Based Approach to Anemia: From History to Lab Interpretation”.

To reassure the patient: “It doesn’t seem life-threatening, but let’s investigate further just to be safe.”

⚠️ Caution: No Antibiotics for EHEC

Antibiotic treatment is contraindicated in EHEC (enterohemorrhagic E. coli, including O157:H7), as it may increase the risk of hemolytic uremic syndrome (HUS). Supportive care is the mainstay of management.

• Use antibiotics cautiously in patients with bloody diarrhea, especially if EHEC is suspected
• Look for warning signs: abdominal tenderness, bloody stools, lack of fever, or HUS risk (esp. in children)

🗣️ Tips for Interviewing

• Be specific: Ask, “Was the blood on the toilet paper or mixed in the stool?” This helps localize the source.
• Compare with baseline: “Was today’s stool different from your usual?” is often more effective than “Is something wrong?”
• Explore recent exposures: Ask about raw seafood, undercooked meat, or recent travel—especially for suspected infectious diarrhea.
• Medication review: Use the phrasing, “Are there any pills or supplements you take daily?” to uncover overlooked over-the-counter meds like NSAIDs or iron.

🖐️ Tips for Physical Examination

• Check conjunctiva in natural light: White lighting may mask pallor—go near a window if possible.
• Note blood characteristics on DRE: Ask yourself: Is it bright red? Dark red? Tarry?
• Use clock-face documentation: Record mass location and texture in terms like “a soft mass at 7 o’clock.”
• Calculate the shock index (HR ÷ SBP): Make it a habit—it’s quick and highly predictive of volume loss.

🧠 Think Out Loud

Verbalizing your clinical reasoning improves diagnostic clarity. Try to “think aloud” during exams:
“This looks like fresh blood… maybe distal.” “No NSAIDs—but is he taking steroids?”
These inner thoughts sharpen your clinical focus and help guide decision-making.

💎 Pearl of the Day

“Not all blood is the same—know where it came from, or you may miss the silent killer.”
— Dr. Atul Gawande

🗣️ OET Speaking Session – GI Bleeding (Hematochezia)

👥 Scenario

You are a doctor at a general outpatient clinic. A 65-year-old man presents after noticing bright red blood in the toilet this morning. He has no abdominal pain or systemic symptoms and is unsure if it’s something serious. He has a history of hemorrhoids but hasn’t been evaluated in years.

You suspect internal hemorrhoids but also consider colorectal cancer or other sources of bleeding.

🎯 Your Task

• Reassure the patient and assess the severity of the bleeding
• Explain the possible causes and rule out serious conditions
• Advise on the need for rectal examination and colonoscopy
• Provide a clear plan for follow-up and referral if needed

💬 Common Patient Cues & Suggested Doctor Responses

✉️ OET Writing Task – Sample Referral Letter

Today’s Date

Dr. Sarah Mitchell
Gastroenterology Department
Central Health Hospital

Re: Mr. Kenji Tanaka, 65 years old

Dear Dr. Mitchell,

I am referring Mr. Kenji Tanaka, a 65-year-old gentleman, for further evaluation of hematochezia of unclear origin.

Mr. Tanaka presented to our clinic this morning reporting bright red blood in the toilet bowl. He noted the blood was on the surface of the stool, with no accompanying abdominal pain, fever, or diarrhea. He has a known history of internal hemorrhoids but has not received recent treatment or follow-up.

On examination, his vital signs were stable, and conjunctivae were pink. Abdominal exam was unremarkable. Digital rectal examination revealed a soft hemorrhoidal mass at 6 o’clock with trace bright red blood. No masses or ulcers were palpated. Initial labs showed hemoglobin 13.8 g/dL and normal inflammatory markers.

Given his age and incomplete prior screening, we are arranging a colonoscopy to exclude neoplastic lesions and confirm the bleeding source. Your expertise in further assessment and management would be appreciated.

Please feel free to contact me should you require additional information.

Yours sincerely,

Dr. [Your Name]
General Practitioner

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🧾 Summary – Rethinking Black and Bloody Stool

When a patient presents with hematemesis or hematochezia, the first step is to ask: Where is the bleeding coming from?
Start by analyzing the color, timing, and stool consistency—these provide vital clues.

Melena typically indicates upper GI bleeding, but don’t forget that dark stools can also be caused by iron supplements, bismuth, or certain foods—this is called pseudo-melena.
In newborns, neonatal melena must be differentiated from swallowed maternal blood (via the Apt test).

Always approach with a clear hypothesis: consider blood loss, anemia severity, infectious causes, and medication history.
Don’t skip the basics—digital rectal exams, shock index, and medication review can save lives.

GI bleeding is not always dramatic—but even a small amount of bright red or black stool can point to a silent threat.
Never assume it’s “just hemorrhoids” until you’ve excluded the rest.

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📚 Related Articles (in English)

• How to Approach Fever: Red Flags & Diagnostic Strategy
• Managing Shock in the Emergency Room
• How to Evaluate and Treat Dehydration
• A Symptom-Based Approach to Anemia

🗾 日本語で読みたい方はこちら：

👉 【日本語版】吐血・下血の診かた：色・タイミング・危険徴候で見抜く消化管出血

1. Saudek CD, et al. The presence of conjunctival pallor as a sign of anemia. JAMA. 1993;270(8):969–971.
2. Laine L, Jensen DM. Management of patients with ulcer bleeding. Am J Gastroenterol. 2021;116(4):659–671.
3. van Zanten SV, et al. Global Guidelines on dyspepsia and PPI use. J Clin Gastroenterol. 2022;56(Suppl 1):S1–S26.
4. Ministry of Health, Labour and Welfare, Japan. Appropriate Use of Medications (PPI, VPZ). 2021 revision.