Angiodysplasia

Slide 1 · Angiodysplasia

Vascular architecture, bleeding and clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning outcomes

Identify angiodysplasia as a vascular malformation of intestinal mucosa and submucosa.

Explain the proposed venous-outflow mechanism without presenting it as proven.

Relate vessel structure to chronic or major intestinal hemorrhage.

Distinguish pathology from clinical diagnosis and management.

Slide 3 · The intestinal wall provides the anatomic context

Mucosa

Submucosa

Muscularis propria

The mucosa faces the lumen and includes epithelium and lamina propria.

The submucosa contains vessels that communicate with the mucosal microcirculation.

Vessels pass through muscularis propria to reach the submucosal plexus.

Slide 4 · Normal blood vessels are structurally supported

Luminal epithelium

Muscularis mucosae

Fine caliber vessels (conceptual)

Original schematic — not a photomicrograph

Capillaries lie within connective tissue beneath the epithelium.

Venules and veins carry blood away from mucosal capillary networks.

Vessel caliber and supporting layers influence susceptibility to injury.

Slide 5 · Angiodysplasia: The defining structural lesion

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Malformed blood vessels occupy mucosa and submucosa.

The affected channels are abnormally dilated and thin walled.

The entity is a vascular malformation, not an epithelial tumor.

Slide 6 · Angiodysplasia is a nonneoplastic vascular lesion

Angiodysplasia / ectasia

Vascular neoplasm

Dilation and malformation of existing vessels; No true neoplastic mass.

True vascular tumors show endothelial proliferation; Biologically distinct from ectasia.

Morphologic distinction: Ectatic channels do not imply endothelial malignancy.

Slide 7 · Angiodysplasia and angioectasia: Practical vocabulary

Angiodysplasia is the pathology term used.

Angioectasia is frequently used in GI endoscopy and bleeding guidance.

Neither term alone establishes current bleeding or proves lesion causality.

Slide 8 · Anatomic predilection: Cecum and right colon

Cecum / ascending

Transverse

Descending

Sigmoid / rectum

Most common location ≠ exclusive location

This site preference is linked to the mechanical hypothesis.

Slide 9 · Age distribution: Predominance after 60 years

Usual clinical recognition after the sixth decade.

Older age increases the relevance of angiodysplasia in lower GI bleeding.

Younger age does not categorically exclude a vascular lesion.

Slide 10 · Prevalence: A relatively uncommon adult lesion

<1%

Adult prevalence reported by Robbins

This denominator is adults overall, not patients undergoing colonoscopy for bleeding.

A population prevalence must not be confused with a proportion of bleeding etiologies.

Slide 11 · Disproportionate contribution to major bleeding

20%

Major lower intestinal bleeding episodes in older groups (Robbins)

The estimate applies to a specified clinical population and severity.

Do not generalize this number to all patients or all GI bleeding.

Slide 12 · Why prevalence and bleeding burden differ

Uncommon lesion

Thin-walled ectatic channels

Clinically important bleeding

Population prevalence and cause-of-bleeding proportion answer different questions.

The malformed, superficially located vessels are vulnerable to disruption.

Slide 13 · Pathogenesis is not established

Robbins explicitly describes the mechanism as undefined.

Mechanical and congenital factors are proposed contributors.

A plausible model must not be converted into a confirmed causal chain.

Slide 14 · The mechanical model begins with normal motility

Distention / contraction

Transient venous compression

Repeated outflow disturbance

Distention and contraction repeatedly alter the geometry of the bowel wall.

Penetrating submucosal veins may be intermittently compressed.

Slide 15 · Venous traversal of muscularis propria matters

Mucosa

Submucosa

Muscularis propria

Submucosal veins traverse the muscularis propria during drainage.

These traversing veins as sites of intermittent occlusion.

Mechanical location links bowel-wall motion to superficial vascular change.

Slide 16 · Intermittent venous obstruction: A proposed trigger

Penetrating vein compressed

Transient outflow restriction

Overlying vessel dilation

Temporary obstruction impedes venous drainage from the overlying plexus.

Repeated episodes could alter vessel diameter and configuration.

Slide 17 · Progression toward dilated and tortuous channels

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Focal dilation is the proposed consequence of repetitive venous obstruction.

Mucosal and submucosal channels become tortuous.

Tortuosity and ectasia together produce the characteristic vascular nest.

Slide 18 · Cecal caliber provides a regional hypothesis

Cecum / ascending

Transverse

Descending

Sigmoid / rectum

Most common location ≠ exclusive location

Greater diameter may increase wall tension during distention.

Slide 19 · Wall tension is an explanatory link, not proof

Larger cecal caliber

Greater wall tension

Possible venous compression

The mechanical model connects wider cecal caliber with greater wall tension.

Wall tension is a conceptual contributor to transient venous compression.

Slide 20 · Integrating the proposed pathogenesis

Motion + wall tension

Venous outflow disturbance

Ectatic mucosal channels

Bowel motion may intermittently obstruct penetrating veins.

Outflow disturbance may yield focal mucosal and submucosal ectasia.

Slide 21 · Congenital mechanisms remain possible

Robbins also mentions congenital factors.

It does not specify a causal gene or developmental pathway for typical colonic lesions.

Avoid assigning hereditary hemorrhagic telangiectasia mechanisms to sporadic angiodysplasia.

Slide 22 · Macroscopic–microscopic distinction

Surface assessment

Tissue assessment

Surface endoscopy reveals ectatic vascular patches and possible current bleeding.

Microscopy demonstrates dilated thin-walled vessels within mucosa and submucosa.

The two modalities assess different features of the same clinical problem.

Slide 23 · Histology: Ectatic vascular nests

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Nests of tortuous vascular channels.

Veins, venules and capillaries contribute to the lesion.

The vessels lie in mucosal and submucosal compartments.

Slide 24 · Histology: Veins and venules

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Dilated veins and venules are conspicuous components.

Their thin walls distinguish them from thick-walled muscular arteries.

Venous morphology fits the proposed outflow-disturbance model.

Slide 25 · Histology: Capillary ectasia

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Capillaries are also involved, extending the lesion toward the mucosal surface.

Superficial ectasia places delicate vascular channels near luminal contents.

Location is integral to the risk of hemorrhage.

Slide 26 · The epithelial covering may be attenuated

Luminal epithelium

Muscularis mucosae

Dilated, irregular vascular channels (conceptual)

Original schematic — not a photomicrograph

Channels covered only by vessel wall and attenuated epithelium.

The remaining interface can be extremely thin.

This configuration makes minor mucosal trauma consequential.

Slide 27 · Bleeding vulnerability follows from structure

Thin epithelial covering

Minor surface injury

Channel disruption / bleeding

The luminal surface may be separated from blood by little protective tissue.

Even minor injury can disrupt a dilated, thin-walled channel.

Slide 28 · Why angiodysplasia can bleed intermittently

The clinical course may include symptom-free intervals.

Minor injury can produce episodes separated by periods without visible loss.

Absence of hemorrhage at a single examination does not exclude past bleeding.

Slide 29 · Clinical spectrum: Chronic to massive hemorrhage

Chronic / intermittent

Acute / major

Long symptom-free intervals or repeated blood loss may occur.

A minority may present with an acute major lower intestinal hemorrhage.

A chronic clinical history does not exclude clinically important bleeding.

Slide 30 · Chronic blood loss: Anemia is a clinical consequence

Repeated blood loss can lead to iron deficiency and falling hemoglobin.

Anemia requires a bleeding-source evaluation; Lesion presence alone is insufficient.

Trend, stool history and endoscopic findings must be integrated.

Slide 31 · Acute blood loss: Recognize the higher-risk phenotype

Major lower GI hemorrhage may present with overt hematochezia.

Assess hemodynamic consequences before concentrating on lesion classification.

Large-volume bleeding is possible even from a nonneoplastic lesion.

Slide 32 · Lesion presence is not identical to lesion culpability

Angioectasia may be an incidental endoscopic finding.

Link the lesion to the bleeding phenotype and exclude competing sources.

Current bleeding stigmata provide stronger attribution than lesion morphology alone.

Slide 33 · Endoscopic appearance: Recognize the vascular pattern

Luminal epithelium

Muscularis mucosae

Schematic surface vascular pattern

Original schematic — not a photomicrograph

Colonic angioectasia typically appears as a superficial erythematous vascular patch.

Branching or fern-like ectatic vessels may be visible.

An endoscopic pattern is not the same as histologic proof of etiology.

Slide 34 · Two complementary diagnostic views

Endoscopy

Histopathology

Surface inspection can identify vascular lesions and bleeding stigmata.

Tissue examination, when available, characterizes abnormal vessel architecture.

Both findings require linkage to the patient’s actual bleeding phenotype.

Slide 35 · A negative snapshot may miss intermittent bleeding

Bleeding episode

Intermittent cessation

Later quiet examination

Bleeding may have stopped before a diagnostic examination.

The underlying malformation may persist despite a quiet clinical interval.

Slide 36 · Lower GI bleeding: Keep a differential diagnosis

Diverticular hemorrhage, ischemic colitis and neoplasia also require consideration.

The patient’s pain, bowel symptoms and examination modify pretest probability.

Do not close the diagnostic process after finding a single vascular lesion.

Slide 37 · Ischemic colitis has a different injury mechanism

Ischemic colitis

Angiodysplasia

Impaired intestinal perfusion with epithelial damage; Often cramps and bloody diarrhea.

Superficial ectatic vessels can bleed without primary ischemic tissue injury.

Acute pain and mucosal injury shift suspicion toward colonic ischemia.

Slide 38 · Hereditary hemorrhagic telangiectasia is distinct

HHT

Sporadic colonic lesion

Multisite inherited disease; Autosomal dominant, endothelial TGF-β pathway defects.

Usually recognized in older adults; Typical colonic lesion has no defined inherited mechanism.

Do not treat a single colonic angioectasia as proof of a systemic genetic disorder.

Slide 39 · Gastric antral vascular ectasia is a related differential

GAVE

Right-colonic angiodysplasia

Antral longitudinal red stripes; Reactive gastropathy, ectatic capillaries and fibrin thrombi.

Cecal/right-colonic predominance; Ectatic tortuous mucosal–submucosal veins and capillaries.

Location and accompanying mucosal changes are discriminating features.

Slide 40 · Dieulafoy lesion: A different vascular source

Dieulafoy lesion

Angiodysplasia

Abnormal submucosal arteriole, classically along the gastric lesser curvature.

Nests of dilated veins, venules and capillaries, classically in right colon.

The two vascular bleeding sources should not be conflated.

Slide 41 · The clinical priority is bleeding severity

Assess stability

Stabilize / risk-stratify

Localize and manage source

Unstable patients require immediate assessment and resuscitative care.

Definitive lesion characterization follows stabilization as appropriate.

Slide 42 · Colonoscopy evaluates suspected colonic bleeding

Colonoscopy permits direct inspection of mucosa for angioectasia.

A suspected lesion should be interpreted with blood distribution and other findings.

The 2023 ACG guideline generally favors nonurgent inpatient colonoscopy over routine colonoscopy within 24 hours.

Slide 43 · CT angiography in significant ongoing hemorrhage

Severe ongoing bleed

CT angiography

Targeted intervention when indicated

CTA has an increasing role in severe lower GI bleeding.

It is principally a bleeding-localization strategy during active hemorrhage.

Slide 44 · Why colonoscopy can miss small-bowel disease

Angiodysplasia can involve sites beyond the accessible colon.

A negative colonic examination does not exclude a small-intestinal source.

The next test follows the pattern of persistent or recurrent bleeding.

Slide 45 · Capsule endoscopy: First-line small-bowel survey

The ESGE 2022 update recommends capsule endoscopy first in suspected small-bowel bleeding.

It offers mucosal visualization beyond conventional upper/lower endoscopy.

The capsule identifies lesions but cannot deliver hemostatic therapy.

Slide 46 · Timing matters for overt small-bowel bleeding

≤48 h

Ideal timing after overt suspected small-bowel bleeding (ESGE)

The guideline specifies ideally within 48 hours when feasible.

This recommendation concerns diagnostic yield, not the pathogenesis of lesions.

Slide 47 · Device-assisted enteroscopy enables treatment

Capsule localization

Device-assisted enteroscopy

Targeted therapy

Deep enteroscopy can investigate a lesion localized by prior testing.

Unlike capsule endoscopy, it can facilitate endoscopic therapy.

Slide 48 · Therapy targets bleeding, not merely lesion visibility

A visible ectatic area without clinical blood loss may not need ablation.

When attributable hemorrhage is present, endoscopic hemostasis is a principal option.

The therapeutic decision is individualized to bleeding burden.

Slide 49 · Argon plasma coagulation: Noncontact ablation

Endoscopic localization

Controlled APC ablation

Assess hemostatic response

APC delivers thermal energy to superficial bleeding vascular lesions.

It is a commonly used endoscopic approach for colonic angioectasia.

Slide 50 · Rebleeding remains an important outcome

Successful local therapy does not necessarily eliminate all lesions.

Additional or previously unrecognized foci may contribute to recurrence.

Follow-up is guided by symptoms, hemoglobin and treatment requirements.

Slide 51 · Refractory disease changes the management question

Persistent transfusion or parenteral iron needs define clinically important burden.

Repeated procedures may be insufficient for some patients.

Systemic therapies have trial evidence in selected severe/recurrent bleeding populations.

Slide 52 · OCEAN trial: The studied population

A 2024 open-label multicenter RCT enrolled 62 patients with angiodysplasia-related anemia.

Patients had substantial prior RBC transfusion or parenteral iron needs.

Octreotide long-acting release was compared with standard care over one year.

Slide 53 · OCEAN trial: Transfusion requirement decreased

0

6

12

18

24

11.0

Octreotide

21.2

Standard care

Combined RBC / parenteral iron units

Adjusted between-group difference: 10.2 composite units (95% CI 2.4–18.1).

The result concerns severe angiodysplasia-related anemia, not all incidental ectasias.

Slide 54 · OCEAN trial: Implications and constraints

The intervention group required fewer endoscopic procedures.

The trial was open label and small, with selected transfusion-dependent patients.

This is supplementary management evidence, not a Robbins morphologic criterion.

Slide 55 · Thalidomide RCT: A separate clinical phenotype

A 2023 placebo-controlled RCT enrolled 150 patients with recurrent small-intestinal bleeding.

Patients were assigned to 100 mg/day, 50 mg/day or placebo for four months.

The primary endpoint assessed at least 50% fewer bleeding episodes during follow-up.

Slide 56 · Thalidomide RCT: Primary response

0

20

40

60

80

68.6

100 mg

51.0

50 mg

16.0

Placebo

Patients with effective response (%)

The trial showed a reduction in recurrent bleeding in its selected population.

It does not establish routine use for all patients with colonic angiodysplasia.

Slide 57 · Benefits must be interpreted alongside harms

Thalidomide adverse events included constipation, somnolence and peripheral symptoms.

Teratogenic risk and neurotoxicity demand specialist safeguards and careful selection.

Evidence of efficacy is not equivalent to unrestricted treatment recommendation.

Slide 58 · Case study: Intermittent occult blood loss

An older adult has recurrent iron-deficiency anemia without dramatic hematochezia.

Colonoscopy reveals right-colonic ectatic vascular patches.

Interpretation: Lesion location fits Robbins, but competing causes of anemia must be assessed.

Slide 59 · Case study: Brisk overt lower GI bleeding

An older adult presents with repeated hematochezia and hemodynamic compromise.

Immediate priorities are severity assessment and stabilization.

Localize active hemorrhage before attributing it to a suspected angioectasia.

Slide 60 · Case study: Persistent anemia after endoscopic care

A patient with repeated treatment still requires transfusions or intravenous iron.

Reassess bleeding sources and cumulative burden rather than assuming cure.

Selected patients may merit specialized discussion of evidence-supported systemic options.

Slide 61 · Mechanism–morphology–clinical correlation

Proposed outflow disturbance

Superficial vascular ectasia

Intermittent / major bleeding

Proposed venous compression explains a plausible route to vascular ectasia.

Dilated, tortuous superficial channels explain bleeding susceptibility.

Slide 62 · Five diagnostic distinctions that prevent error

Malformation is not a vascular tumor.

Right-colonic preference is not right-colon exclusivity.

Proposed pathogenesis is not experimentally established causation.

Incidental angioectasia is not always the active bleeding source.

Small-bowel disease requires a different diagnostic route.

Slide 63 · References and source boundaries

Core morphology, distribution and mechanism: Robbins, Cotran & Kumar, 11th edition, Ch. 17, pp. 712–713.

Vascular ectasias and mimics: Robbins Ch. 11 and Ch. 17.

Clinical investigation: ACG lower GI bleeding guideline (2023); ESGE small-bowel guideline (2022 update).

Therapy trial context: OCEAN (Gastroenterology, 2024); Chen et al. (NEJM, 2023).