A stomach AVM is a tangle of vessels where arteries connect straight into veins, which leaves fragile vessels sitting close to the stomach lining where they can bleed. The cause depends on which kind of lesion you have, because doctors often use “AVM” for two quite different things.1Techniques in Gastrointestinal Endoscopy. Mallory–Weiss Tears, Angiodysplasia, Watermelon Stomach, and Dieulafoy’s: A Potpourri Most lesions found in adults developed slowly over the years, while a rarer kind is present from birth. Neither kind comes from diet, alcohol, or anything a person did.
Born With It or Developed Later
Doctors have used the terms angiodysplasia, vascular ectasia and arteriovenous malformation to describe similar-looking lesions.2Techniques in Gastrointestinal Endoscopy. Mallory–Weiss Tears, Angiodysplasia, Watermelon Stomach, and Dieulafoy’s: A Potpourri Angiodysplasia means small widened vessels in or just under the stomach lining, with thin muscle in their walls.3Techniques in Gastrointestinal Endoscopy. Mallory–Weiss Tears, Angiodysplasia, Watermelon Stomach, and Dieulafoy’s: A Potpourri The labels blur because the naming of vessel problems has long been inconsistent, and treatment depends on the exact type.4PubMed Central. Classification of Vascular Anomalies: An Update
On an endoscopy report you may also see GIVM (short for gastrointestinal vascular malformation). It is fair to ask which type your doctor means, since cause and outlook differ.
The acquired type usually appears as several small, flat, bright red patches in the lining, often a few millimeters across, rather than one large tangle. Because they are so small and flat, they are easy to overlook if the stomach is not fully inflated or if blood hides them. A true AVM lies deeper and is more likely to be a single lesion, though that is a tendency, not a rule. Appearance is one clue among several, alongside age, other conditions and family history.
True AVMs of the gut are developmental defects: a lasting, direct link between arteries and veins beneath the lining.5American Journal of Gastroenterology. Gastric Arteriovenous Malformation: A Unique Case of a Rare Phenomenon They bypass the tiny capillaries that normally slow blood down.6PubMed Central. Intestinal arteriovenous malformation managed with palliative ligation and division of the feeding artery: a case report High-pressure arterial blood therefore pours into thin-walled veins. Even so, true AVMs are a rare cause of stomach bleeding.7Video Journal and Encyclopedia of GI Endoscopy. Endoscopic and Angiographic Diagnosis and Management of a Gastric Arteriovenous Malformation
A lesion present since birth can stay silent for decades, because vessels can carry blood for years before a wall gives way. When it does bleed, the loss is often slow, showing up as anemia and tiredness rather than sudden blood loss. Discovery often comes from tests for unexplained low iron.
Acquired lesions tend to appear later in life, which reflects how long these vessels take to develop and how aging affects the stomach lining. A congenital lesion was set in place before birth, so lifestyle could not have created it.
How Low Oxygen Grows New Fragile Vessels
Tissue right next to acquired stomach lesions makes about 8 times more of a vessel-growth signal than normal lining.8American Journal of Gastroenterology. Increased Vascular Endothelial Growth Factor and Hypoxia Inducible Factor-1α Transcription in Acquired Sporadic Gastric Angiodysplasia It also makes about 3 times more of a low-oxygen alarm signal that triggers that growth.9American Journal of Gastroenterology. Increased Vascular Endothelial Growth Factor and Hypoxia Inducible Factor-1α Transcription in Acquired Sporadic Gastric Angiodysplasia Both signals fade with distance from the lesion.10American Journal of Gastroenterology. Increased Vascular Endothelial Growth Factor and Hypoxia Inducible Factor-1α Transcription in Acquired Sporadic Gastric Angiodysplasia That pattern suggests the lesions sprout where the lining is short of oxygen.11PubMed Central. HIF-1α and HIF-2α induced angiogenesis in gastrointestinal vascular malformation and reversed by thalidomide This points to a likely cause, not a proven one.12American Journal of Gastroenterology. Increased Vascular Endothelial Growth Factor and Hypoxia Inducible Factor-1α Transcription in Acquired Sporadic Gastric Angiodysplasia
In plain terms, the lining senses it lacks oxygen and sends out a call for more vessels. The new vessels are thin-walled and leaky, and over years these clusters enlarge and can ooze blood.
Age matters because lowered blood flow to the stomach lining is a known trigger for vessel growth.13PubMed Central. HIF-1α and HIF-2α induced angiogenesis in gastrointestinal vascular malformation and reversed by thalidomide Conditions that reduce oxygen delivery, which are common with age, may raise the chance of lesions. Aging can narrow the arteries that supply the stomach, and heart and lung conditions that become more common over time can lower the oxygen in the blood that reaches it. Lesions accumulate slowly, so the acquired type is mostly a finding in older adults.
A drug that blocks this pathway, thalidomide, has reduced these signals, which supports the link.14PubMed Central. HIF-1α and HIF-2α induced angiogenesis in gastrointestinal vascular malformation and reversed by thalidomide Still, the signals being higher near lesions shows an association and does not by itself prove that low oxygen came first. The oxygen explanation is the best current understanding, not a settled mechanism for every case.
No food, drink or habit has been shown to create these vessels. The realistic lever is managing related heart or liver conditions.
The Heart Valve Connection
In one large clinic’s records, about 32% of people with gut AVMs also had a narrowed aortic valve.15PubMed Central. Aortic stenosis and Heyde’s syndrome: A comprehensive review Heyde’s syndrome is the name for the trio of a narrowed aortic valve, gut AVM bleeding and a clotting problem.16PubMed. Perspectives on Heyde’s Syndrome and Calcific Aortic Valve Disease How often the full syndrome occurs is still debated.17PubMed. Perspectives on Heyde’s Syndrome and Calcific Aortic Valve Disease
The 32% figure comes from one clinic, so it describes the patients seen there and may not match every population. Both conditions become more common with age, so some of the overlap may simply reflect older patients having both. Most people with a narrowed aortic valve do not have a bleeding gut lesion, so the link is no reason for alarm if you have only a valve problem.
The clotting piece works like this. Blood forced through a tight valve stretches a clotting protein called von Willebrand factor.18PubMed Central. Aortic Stenosis Complicated by Gastrointestinal Arteriovenous Malformations: It is not Always Heyde Syndrome An enzyme then cuts it up, and the body clears it too early.19PubMed Central. Aortic Stenosis Complicated by Gastrointestinal Arteriovenous Malformations: It is not Always Heyde Syndrome Small vessel leaks therefore clot poorly and keep bleeding. Not every person with both conditions has Heyde’s syndrome.20PubMed Central. Aortic Stenosis Complicated by Gastrointestinal Arteriovenous Malformations: It is not Always Heyde Syndrome
Von Willebrand factor helps platelets stick to a damaged vessel wall, the first step in plugging a leak. When too much of it is cut up early, the plug forms poorly, even if the platelet count is normal. This is an acquired clotting weakness caused by the valve, not an inherited bleeding disorder.
Many people with valve disease take aspirin or anticoagulants. These do not cause lesions, but they make existing ones bleed more. Never stop them without asking your doctor.
If you have a heart murmur, ask whether your valve has been checked with an echocardiogram, and mention any stomach bleeding to your cardiologist. It is also worth asking whether valve treatment could affect future bleeding. Bring a list of the blood thinners you take.
Family Conditions That Cause Them
Hereditary hemorrhagic telangiectasia (HHT) is an inherited disorder that causes fragile vessel clusters in the nose, gut and sometimes brain.21PubMed. Hereditary hemorrhagic telangiectasia: an overview of diagnosis, management, and pathogenesis These usually show up as bleeding.22PubMed. Hereditary hemorrhagic telangiectasia: an overview of diagnosis, management, and pathogenesis At least five genes can cause it, with two genes behind about 85% of cases.23PubMed. Hereditary hemorrhagic telangiectasia: an overview of diagnosis, management, and pathogenesis Faulty growth-signal pathways in vessel walls lead to malformed vessels.24PubMed. Deregulated TGF-β/BMP Signaling in Vascular Malformations
Nosebleeds are often the earliest sign, and may begin in childhood or the teen years, long before any stomach problem.25PubMed. Hereditary hemorrhagic telangiectasia: an overview of diagnosis, management, and pathogenesis Stomach and intestinal lesions tend to cause trouble later, often in adulthood, as slow bleeding that leads to iron-deficiency anemia. Vessel malformations can also occur in the lungs, liver and brain, which is why HHT is considered a whole-body disorder.
Nosebleeds plus a stomach lesion should prompt questions about family history. Genetic testing is available for the main genes. Other clues include red pinpoint spots on the lips, tongue or fingertips, relatives with repeated nosebleeds or unexplained anemia, and a relative with a lung or brain vessel malformation. A referral to an HHT clinic is worth asking about.
People with HHT often have lesions earlier in life and have other signs, such as nosebleeds, that the acquired type does not bring. A stomach lesion alone is much more likely to be the acquired type.
The distinction matters for relatives. Children of a person with HHT have a one in two chance of inheriting it. Screening can find hidden brain or lung lesions before they bleed, and treatment options differ from those for sporadic lesions.
Liver Disease and Look-Alike Lesions
High pressure in the liver’s vein system can cause portal hypertensive gastropathy, a congested, bleeding stomach lining.26PubMed Central. Portal hypertensive gastropathy: A systematic review of the pathophysiology, clinical presentation, natural history and therapy High pressure alone is not enough, since many people with it never develop this.27PubMed Central. Portal hypertensive gastropathy: A systematic review of the pathophysiology, clinical presentation, natural history and therapy It becomes more common with more severe and longer-lasting liver disease.28PubMed Central. Portal hypertensive gastropathy: A systematic review of the pathophysiology, clinical presentation, natural history and therapy
On endoscopy the lining often looks mosaic-like or snakeskin-patterned, with red marks across the upper stomach. Many people have mild forms that cause no bleeding, and the bleeding that does occur is usually slow and chronic. It usually appears in someone already known to have significant liver disease, which sets it apart from an isolated acquired lesion in a person with a healthy liver.
Watermelon stomach is widened vessels running in stripes along the folds of the lower stomach.29Yamada’s Textbook of Gastroenterology. Gastrointestinal vascular malformations and neoplasms: arterial, venous, arteriovenous, and capillary It looks different on endoscopy and is managed differently. The red stripes converge toward the stomach’s outlet. It can cause slow bleeding and iron-deficiency anemia, and some patients need repeated treatment. It is seen more often alongside certain other conditions, so doctors may look for those once it is found.
A Dieulafoy lesion is a single unusually large artery just under the lining that can bleed massively.30PubMed. Dieulafoy’s disease: a distinctive arteriovenous malformation causing massive gastric haemorrhage It is tiny and easy to miss unless it is actively bleeding.31PubMed. Dieulafoy’s disease: a distinctive arteriovenous malformation causing massive gastric haemorrhage It was first described in the upper stomach but can occur anywhere in the gut.32Yamada’s Textbook of Gastroenterology. Gastrointestinal vascular malformations and neoplasms: arterial, venous, arteriovenous, and capillary
The exact label changes your care. Liver-related changes improve by lowering liver pressure. Ask your doctor to confirm which one you have.
Repeat endoscopies are common. Lesions can be missed when they are not bleeding, and a second look may be needed if bleeding returns. That is not a sign of error.
How Doctors Find and Treat Them
Endoscopy is the main test, with CT angiography and angiography saved for hard-to-find cases.33Radiologia Brasileira. Gastric arteriovenous malformation: treatment by embolization Some true AVMs are missed on endoscopy and barium X-rays.34PubMed Central. Exsanguinating upper GI bleeds due to Unusual Arteriovenous Malformation (AVM) of stomach and spleen: a case report A dye scan of blood vessels may be needed when bleeding persists.35PubMed Central. Gastric Arteriovenous Malformation with Characteristic Endoscopic Findings
A standard endoscopy passes a thin flexible camera through the mouth into the stomach while you are sedated, so most people feel little. The doctor looks for bleeding points and for the red flat patches typical of the acquired type. If a lesion is seen, it can often be treated in the same procedure. Fasting beforehand matters because food in the stomach can hide lesions.
If bleeding continues and the stomach looks clear, the source may lie in the small intestine, which a standard endoscope does not reach. A swallowed camera capsule can photograph it as it passes through. CT angiography uses dye and scanning to find a bleeding vessel, and it works best when blood is actively flowing. These tests are for people whose bleeding persists, not routine steps for everyone.
Bleeding vessels can be sealed with clips during endoscopy.36Video Journal and Encyclopedia of GI Endoscopy. Endoscopic and Angiographic Diagnosis and Management of a Gastric Arteriovenous Malformation A radiologist can also block the feeding artery with tiny coils through a catheter.37Video Journal and Encyclopedia of GI Endoscopy. Endoscopic and Angiographic Diagnosis and Management of a Gastric Arteriovenous Malformation A Dieulafoy lesion can be removed surgically if other steps fail.38PubMed. Dieulafoy’s disease: a distinctive arteriovenous malformation causing massive gastric haemorrhage Hormone therapy has been tried to reduce gut vessel bleeding, with mixed results.39PubMed. Hormonal therapy for bleeding gastrointestinal mucosal vascular abnormalities: a promising alternative
Iron tablets or infusions often treat the resulting anemia. Acquired lesions can recur, so follow-up blood counts matter, and treating heart valve or liver problems may cut recurrence.
Black, tarry stools need prompt medical review. Vomiting blood or dizziness needs emergency care. Growing tiredness can signal slow blood loss.