Special Surgery 28. Symptomatics, Causes, and Treatments of Lower-Gastrointestinal Bleeding

I. Definition, Classification and Symptomatics

Definition

Lower gastrointestinal bleeding (LGIB) = bleeding from GI tract distal to ligament of Treitz
Practical clinical source: colon, rectum, anus, or small bowel distal to duodenum
Most acute LGIB comes from colon or anorectum
Small bowel bleeding is considered when upper endoscopy and colonoscopy do not find the source
First priority: hemodynamic stability → resuscitation → localization/treatment

Classification

By presentation

Overt bleeding → visible blood per rectum
Occult bleeding → positive fecal blood test / iron deficiency anemia
Acute massive bleeding → shock, transfusion need, urgent localization
Chronic intermittent bleeding → anemia, recurrent hematochezia

By source

Colonic: diverticulosis, angiodysplasia, cancer, polyps, colitis
Anorectal: hemorrhoids, fissure, rectal ulcer, tumor
Small bowel: angiodysplasia, tumor, Crohn disease, Meckel diverticulum, NSAID enteropathy
Brisk UGIB with rapid transit can mimic LGIB

Main Symptoms

Hematochezia:

Bright red or maroon blood per rectum
May be mixed with stool or passed separately
Bright red blood on toilet paper/bowl → often anorectal source
Maroon stool/clots → more proximal colon or brisk bleeding
Brisk UGIB can also cause hematochezia

Melena:

Less common in LGIB
May occur with slow right colon or small bowel bleeding
Always consider UGIB first if classic black tarry stool

Symptoms of anemia/hypovolemia:

Fatigue, dizziness, syncope
Shortness of breath, chest pain in coronary disease
Pallor, tachycardia, orthostatic hypotension
Shock in massive bleeding

Abdominal pain/cramps → ischemic, inflammatory or infectious colitis
Bloody diarrhea + urgency/tenesmus → colitis, IBD, infectious disease
Painless large-volume bleeding → diverticulosis or angiodysplasia
Weight loss, altered bowel habit, iron deficiency anemia → colorectal cancer until excluded

Clinical Clues

Finding	Likely source
Painless massive hematochezia in older patient	Diverticular bleeding
Painless recurrent occult/overt bleeding, right colon	Angiodysplasia
Blood on paper / dripping after stool, pruritus, prolapse	Hemorrhoids
Painful defecation with small bright red bleeding	Anal fissure
Crampy left-sided pain → bloody diarrhea	Ischemic colitis
Fever, diarrhea, systemic symptoms	Infectious colitis

II. Causes and Pathophysiology

1. Diverticular Bleeding

Most common cause of acute severe LGIB in older adults
Usually painless, intermittent, abrupt hematochezia
Can be massive and brisk
Mechanism:

Diverticulum forms where vasa recta penetrate bowel wall
Vessel becomes stretched/exposed at diverticular neck or dome
Erosion of artery → arterial bleeding → sudden hematochezia

Bleeding often stops spontaneously, but recurrence is common

2. Angiodysplasia / Angioectasia

Dilated, fragile, tortuous mucosal/submucosal vessels
Often in cecum and right colon
Associated with aging, chronic kidney disease, aortic stenosis, von Willebrand disease
Presentation: occult iron deficiency anemia or painless recurrent hematochezia
Pathomechanism: intermittent venous obstruction → mucosal hypoxia → fragile ectatic vessels

3. Anorectal Causes

Hemorrhoids:

Enlarged/displaced anal vascular cushions
Painless bright red bleeding, often after defecation
Blood on paper, in bowl, or coating stool
Important: hemorrhoids do not exclude proximal colorectal cancer

Anal fissure:

Tear in anoderm, usually posterior midline
Severe defecation pain + small bright bleeding

4. Colorectal Cancer and Polyps

Can cause occult bleeding, visible hematochezia, or iron deficiency anemia
Warning signs:

Weight loss
Change in bowel habit
Tenesmus or narrow stool
Unexplained iron deficiency anemia, especially in men/postmenopausal women

Polyps usually asymptomatic
Large adenomas and malignant polyps can bleed intermittently

5. Colitis

Inflammatory bowel disease:

Ulcerative colitis: rectal bleeding, bloody diarrhea, urgency, tenesmus
Crohn colitis: diarrhea, pain, perianal disease possible

Ischemic colitis:

Sudden crampy abdominal pain followed by bloody diarrhea
Often elderly / atherosclerosis / low-flow state / vascular disease
Common watershed areas: splenic flexure, rectosigmoid junction

Infectious colitis:

Bloody diarrhea, fever, cramps, systemic symptoms
Pathogens: Shigella, Salmonella, Campylobacter, enterohemorrhagic E. coli, C. difficile, amoebiasis

6. Iatrogenic and Small Bowel Causes

Post-polypectomy bleeding:

Immediate or delayed after endoscopic resection
Risk increased with large polyp, right colon, antithrombotics

Radiation proctitis → chronic rectal bleeding, telangiectasia
NSAID colopathy/enteropathy → ulcers, erosions, strictures
Small bowel tumors, Crohn disease, Meckel diverticulum → obscure bleeding

III. Diagnostics and Risk Stratification

Initial Assessment

ABCDE logic first if severe bleeding
Assess hemodynamic status:

Blood pressure, heart rate, shock index
Orthostatic symptoms
Urine output, mental status, peripheral perfusion

History:

Amount/color/timing of bleeding
Pain, diarrhea, fever, weight loss, bowel habit change
Previous colonoscopy, diverticulosis, IBD, cancer, vascular disease
NSAIDs, aspirin, anticoagulants, antiplatelet drugs
Symptoms suggesting UGIB: hematemesis, melena, epigastric pain, liver disease

Physical examination:

Abdominal tenderness/peritonitis
Digital rectal examination: confirm blood, stool color, mass, fissure, hemorrhoids
Anoscopy/proctoscopy if clear anorectal bleeding suspected

Laboratory Tests

CBC: hemoglobin, platelet count
Hemoglobin may be initially normal in acute bleeding
Coagulation: INR, PT/aPTT if anticoagulation/coagulopathy suspected
Renal function and electrolytes: dehydration, CKD, bowel prep safety
Liver tests if portal hypertension/coagulopathy possible
CRP/WBC if inflammatory or infectious colitis suspected
Type and screen / crossmatch if transfusion may be needed
Stool cultures / C. difficile toxin if infectious colitis suspected

Risk Stratification

Low-risk/self-limited bleeding:

Stable vital signs
No ongoing bleeding
No major comorbidity
No major hemoglobin drop
Can be considered for outpatient colonoscopy depending on risk score and local practice

High-risk/major bleeding:

Hemodynamic instability
Ongoing hematochezia
Syncope, shock, transfusion need
Anticoagulation/coagulopathy
Significant cardiovascular/renal/liver disease

Oakland score can help identify low-risk patients, but does not replace clinical judgment

Diagnostic Tools

Colonoscopy

Main diagnostic and therapeutic test in stable LGIB
Requires adequate bowel preparation when possible
Can identify diverticular stigmata, angiodysplasia, cancer, polyps, colitis, post-polypectomy bleeding
Allows endoscopic hemostasis or biopsy/resection when indicated
Most inpatient colonoscopy can be nonurgent after stabilization; routine urgent colonoscopy within 24 h does not clearly improve outcomes

CT Angiography (CTA)

Key test for severe ongoing bleeding or hemodynamic instability after resuscitation
Rapid, noninvasive localization of active bleeding
Shows contrast extravasation, vascular anatomy and possible tumor/inflammation
Positive CTA → interventional radiology embolization or targeted endoscopy/surgery
Limitation: needs active bleeding during scan

Catheter Angiography

Diagnostic and therapeutic
Used mainly after positive CTA or in ongoing severe bleeding
Allows selective embolization
Complication: bowel ischemia, especially with nonselective embolization

Radionuclide Scan

Very sensitive for intermittent/slow bleeding
Less precise localization than CTA
Limited role where CTA/endoscopy are available

Upper Endoscopy and Small Bowel Tests

Upper endoscopy if hematochezia with shock or features suggesting UGIB
Capsule endoscopy after negative upper endoscopy + colonoscopy when small bowel bleeding suspected
Device-assisted enteroscopy allows diagnosis and treatment of small bowel lesions
Meckel scan in young patient with unexplained painless bleeding

IV. Treatment

Initial Stabilization

Assess airway/breathing/circulation
Two large-bore IV lines or central access if severe
Crystalloid only until blood available; avoid excessive dilution
Type and crossmatch
NPO initially in severe bleeding
Monitor vitals, urine output, repeated hemoglobin and coagulation
Call gastroenterology/interventional radiology/surgery early in major bleeding

Transfusion and Hemostasis Correction

Restrictive RBC transfusion strategy in most stable patients:

Transfuse around Hb <= 7 g/dL if no major cardiovascular disease
Consider threshold around Hb <= 8 g/dL or higher target in significant cardiovascular disease / ongoing shock

Platelets if severe thrombocytopenia with active bleeding
Correct major coagulopathy in life-threatening bleeding
Temporarily stop anticoagulants in major LGIB
Reverse warfarin/DOACs only for life-threatening or uncontrolled bleeding after thrombotic risk assessment
Aspirin for secondary cardiovascular prevention is usually continued or restarted early after hemostasis
Primary-prevention aspirin should usually be stopped

Endoscopic Treatment

Indications:

Active bleeding site
Visible vessel / adherent clot / high-risk stigmata
Post-polypectomy bleeding
Angiodysplasia

Methods:

Mechanical therapy: clips, band ligation in selected lesions
Thermal coagulation: contact coagulation / argon plasma coagulation for angiodysplasia
Injection therapy: diluted adrenaline for temporary control, usually combined with definitive therapy
Polypectomy/EMR defect bleeding → clips, coagulation, injection, hemostatic powder in selected cases

Treatment by Cause

Cause	Treatment logic
Diverticular bleeding	Resuscitation; colonoscopy if stable; clips/band/coagulation if stigmata found; CTA → embolization if severe ongoing bleeding
Angiodysplasia	Endoscopic argon plasma coagulation or other coagulation; treat anemia; repeat therapy if recurrent
Hemorrhoids	Fiber, stool softening, avoid straining; rubber band ligation/sclerotherapy; hemorrhoidectomy for severe grade III-IV/recurrent disease
Anal fissure	Stool softening, topical anesthetic/vasodilator; lateral internal sphincterotomy for refractory chronic fissure in selected patients
Colorectal cancer	Biopsy and staging; oncological colectomy/rectal cancer pathway; emergency surgery/stenting if obstruction or uncontrolled bleeding
IBD flare	Medical treatment with gastroenterology; surgery for toxic megacolon, perforation, refractory severe colitis or cancer/dysplasia
Ischemic colitis	Supportive care, IV fluids, bowel rest, antibiotics if moderate/severe; surgery for peritonitis, gangrene, perforation or persistent bleeding
Infectious colitis	Fluids, stool testing, pathogen-directed treatment; avoid antimotility drugs in severe/invasive disease

Radiologic Intervention

Selective catheter angiography with embolization
Best when CTA localizes active bleeding
Useful for persistent/inaccessible bleeding or poor bowel preparation
Advantages: rapid control without laparotomy
Risks: bowel ischemia, rebleeding, contrast nephropathy

Surgical Treatment

Rarely needed because most LGIB stops spontaneously or is controlled endoscopically/radiologically
Indications:

Massive ongoing bleeding despite resuscitation
Failed endoscopic and radiologic control
Recurrent severe bleeding with localized source
Peritonitis, perforation, gangrenous ischemic bowel
Bleeding tumor requiring oncological resection

Operation depends on localization:

Localized colonic source → segmental colectomy
Unlocalized life-threatening colonic bleeding → subtotal colectomy may be required, but has high morbidity
Avoid blind segmental colectomy without localization

Exam-Focused Algorithm

Hematochezia → assess shock and resuscitate
Unstable or ongoing severe bleeding → CTA → embolization / targeted therapy
Stable patient → bowel prep → inpatient or outpatient colonoscopy based on risk
Negative colonoscopy + ongoing suspicion → upper endoscopy or small bowel evaluation
Cause-specific therapy: diverticular/angiodysplasia/endoscopic, colitis medical, cancer oncological, surgery only if uncontrolled/localized or complication

Exam focus: LGIB usually presents with hematochezia. Diverticulosis is the most common severe cause in older adults; angiodysplasia causes painless recurrent bleeding; cancer must be excluded with anemia or altered bowel habits. Initial management is resuscitation and risk assessment. Stable patients get colonoscopy after bowel preparation; unstable ongoing bleeding gets CTA first. Surgery is last-line unless bleeding is uncontrolled or there is perforation, ischemic necrosis or tumor.