When Does a Hernia Bleed? Causes and Warning Signs

Hernias bleed through several distinct mechanisms depending on their type and location, and the bleeding ranges from a slow, invisible trickle that shows up only as anemia to a sudden, life-threatening hemorrhage. The most well-documented cause is the hiatal hernia, where the stomach pushes through the diaphragm and develops small erosions called Cameron lesions that can ooze blood for months or years without obvious symptoms. But abdominal wall hernias can bleed too, whether from trapped bowel losing its blood supply or, less commonly, from surgical mesh eroding into nearby organs long after a repair. Understanding when and why a hernia bleeds matters because the warning signs are easy to miss.

How Hiatal Hernias Cause Bleeding

A hiatal hernia forms when part of the stomach slides upward through the opening in the diaphragm where the esophagus passes. This is the hernia type most closely linked to gastrointestinal bleeding, and the culprit is usually a set of shallow ulcers or erosions along the folds of the stomach lining where it gets pinched by the diaphragm. These are called Cameron lesions, named after the physician who first described them in the 1980s.

The damage happens because the diaphragm squeezes the stomach folds trapped in the hiatal opening, creating mechanical trauma and reducing blood flow to those folds. That local ischemia weakens the protective lining of the stomach, and stomach acid then attacks the vulnerable tissue, deepening the erosion.¹ It is a combination of physical pressure, restricted blood supply, and acid injury working together.²

The result is chronic, low-grade bleeding that most people never see. Blood seeps into the stomach and passes through the digestive tract in quantities too small to change the color of stool noticeably, at least at first. Over weeks and months, this steady loss depletes iron stores and drives down hemoglobin levels. Many Cameron lesion cases are diagnosed only after someone is worked up for unexplained iron-deficiency anemia, not because they noticed any bleeding at all.³

How Common Are Cameron Lesions

Among people who have a hiatal hernia, roughly 3 in 100 will have Cameron lesions if someone looks for them with an endoscope. But the risk rises sharply with hernia size. In one large endoscopy series, Cameron lesions turned up in about 13% of patients whose hiatal hernia measured five centimeters or larger, compared with much lower rates in smaller hernias.⁴ Frequent use of anti-inflammatory painkillers like ibuprofen also increases the odds, since these drugs thin the stomach’s protective mucus layer and make the already stressed tissue even more vulnerable to acid injury.⁵

A prospective study of patients being evaluated for iron-deficiency anemia found that a large hiatal hernia was the likely explanation in about 9% of them. In that group, hemoglobin levels at diagnosis were strikingly low, and Cameron erosions were found in a third of those patients on endoscopy.⁶ In other words, a sizable minority of people with unexplained anemia turn out to have been slowly bleeding from a hernia nobody suspected.

When Hiatal Hernia Bleeding Becomes Acute

Most Cameron lesion bleeding is occult, meaning hidden. But it can turn acute. In the same endoscopy series mentioned above, overt GI bleeding was actually more common than occult bleeding as the presenting complaint, and Cameron lesions were significantly more likely to be found in patients presenting with visible bleeding than in those without it. About one in five patients with Cameron lesions had high-risk features on endoscopy, including active bleeding, visible blood vessels at the ulcer base, or overlying clots.⁴ These cases can require endoscopic treatment with clips, cautery, or injection to stop the bleeding.

There is another route to acute bleeding from a hiatal hernia that has nothing to do with Cameron lesions. When a large paraesophageal hernia causes repeated forceful vomiting or retching, the mechanical strain can tear the lining at the junction between the esophagus and stomach. This is a Mallory-Weiss tear, and it can produce dramatic bleeding. A reported case in an infant as young as nine months illustrated this: the child presented with vomiting, coffee-ground material, and severe anemia, ultimately traced to a Mallory-Weiss tear caused by a type IV paraesophageal hernia that had pushed both stomach and colon into the chest cavity.⁷

Beyond Cameron lesions and mucosal tears, the hernia itself can provoke bleeding from hemorrhagic esophagitis, gastritis, or even a gastric or duodenal ulcer that develops in the herniated portion of the stomach. A retrospective study of 32 patients who bled from hiatal hernias found that hemorrhagic esophagitis was the single most common source, with ulcers and gastritis accounting for additional cases.⁸

When Abdominal Wall Hernias Lead to Bleeding

Hiatal hernias get the most attention for bleeding, but inguinal, ventral, and incisional hernias can cause it too, usually through a different and more dangerous pathway: strangulation. When a loop of bowel gets trapped in the hernia opening and its blood supply is cut off, the tissue starts dying. This process, called ischemic necrosis, can produce bleeding into the bowel lumen even before the bowel perforates. Giant paraesophageal hernias carry the same strangulation risk and can progress to gastric mucosal necrosis, perforation, and erosive ulcers.⁹

Even without full strangulation, intermittent trapping can cause repetitive ischemic injury. One reported case involved a man with an inguinal hernia whose bowel slid in and out of the hernia sac repeatedly. Colonoscopy showed inflammation of the cecum and ascending colon, ulceration of the terminal ileum, and a polyp with abnormal blood vessels. Once the hernia was repaired, all of these changes resolved, confirming that the trauma of repeated herniation had been the cause.¹⁰

Bleeding After Hernia Surgery

Hernia repair is one of the most common operations worldwide, and postoperative bleeding is a recognized complication. This can happen in two distinct ways: a hematoma forming in the surgical wound, or delayed bleeding caused by implanted mesh eroding into surrounding structures.

Surgical-site hematomas tend to show up in the first few days after the operation. The strongest predictors are warfarin use and repair of a recurrent hernia, both of which independently raised the odds of developing a hematoma after inguinal hernia repair in a large analysis.¹¹ Data from the Herniamed Registry, a large European hernia database, found that patients on blood thinners or with clotting disorders had roughly double the rate of postoperative bleeding after incisional hernia repair compared with patients at normal clotting risk, and they were more than twice as likely to need a reoperation to control that bleeding.¹² A separate study found that continuing antithrombotic medications through inguinal hernia repair increased the rate of minor postoperative bleeding, though most cases could be managed without another surgery.¹³

Mesh erosion is rarer but more alarming. The synthetic material used in tension-free hernia repairs can slowly migrate through tissue and erode into the bowel wall. When it does, the result can be episodic GI bleeding, bowel obstruction, or perforation. In one case, mesh from an inguinal hernia repair eroded through the sigmoid colon wall and caused acute lower GI bleeding.¹⁴ In another, a ventral hernioplasty mesh migrated into the small bowel and produced life-threatening hemorrhage that was only diagnosed during emergency surgery.¹⁵ These complications can appear years after the original repair, which makes them particularly difficult to diagnose since the hernia operation may be far from the patient’s mind.

Bleeding can also follow less conventional hernia-related procedures. After transoral incisionless fundoplication, a procedure sometimes used to address gastroesophageal reflux associated with hiatal hernias, an ulcer developed at the suture site on the gastric cardia and bled, requiring repeat endoscopy and cauterization to resolve.¹⁶

Warning Signs You Should Not Ignore

The tricky part about hernia-related bleeding is that the most common form is invisible. Chronic occult bleeding from a hiatal hernia tends to announce itself through consequences rather than through obvious signs of blood loss. Here is what to watch for:

• Unexplained fatigue and pallor: Iron-deficiency anemia builds gradually. You may feel increasingly tired, short of breath on exertion, or notice that your skin or nail beds look pale. If you have a known hiatal hernia and these symptoms appear, anemia from Cameron lesions should be on the list.
• Black or tarry stools: Blood that has been digested turns stool dark and sticky. This is called melena, and it indicates bleeding from the upper GI tract. It can signal that a Cameron lesion or gastric erosion has progressed.
• Vomiting blood or coffee-ground material: This suggests active upper GI bleeding and warrants urgent medical attention. In the context of a hiatal hernia, it could indicate a Cameron ulcer with a high-risk feature, a Mallory-Weiss tear, or hemorrhagic esophagitis.
• Bright red blood from the rectum: Less typical for hiatal hernias but possible with abdominal wall hernias where mesh has eroded into the colon or where intermittent bowel trapping has caused mucosal damage.
• Iron-deficiency anemia that does not respond to iron supplements: If you are taking iron but your levels are not recovering, ongoing blood loss is likely. In people with large hiatal hernias, this pattern is well documented and tends to resolve after surgical hernia repair.¹⁷

For abdominal wall hernias, the warning signs of dangerous bleeding overlap with the signs of strangulation: sudden severe pain at the hernia site, a bulge that becomes hard, tender, or discolored, nausea and vomiting, and inability to push the hernia back in. These indicate trapped bowel losing its blood supply and constitute a surgical emergency.

How Hernia Bleeding Gets Diagnosed

Upper GI endoscopy is the primary tool for finding Cameron lesions and other bleeding sources related to hiatal hernias.¹⁸ The challenge is that these erosions are easy to overlook. They sit on the folds of the stomach at the level of the diaphragm, and an endoscopist who is not specifically looking for them, or who does not retroflect the scope to view the area from below, may miss them entirely. The fact that other conditions often coexist makes things harder still: peptic ulcer disease, reflux esophagitis, and gastritis are all common in people with hiatal hernias, and any of these can be mistakenly identified as the bleeding source while Cameron lesions go unnoticed.⁵

When an abdominal wall hernia is suspected of causing bowel ischemia, CT imaging is the go-to test. Multi-detector CT scans can identify signs of strangulation with high accuracy. Bowel wall thickening and engorgement of the blood vessels in the mesentery are among the most reliable indicators.¹⁹ Reduced enhancement of the bowel wall on CT is especially specific for ischemia, though not all ischemic bowel shows that finding.²⁰

Blood lactate levels can offer a useful clue in the emergency department. In patients with incarcerated hernias, elevated lactate suggests that bowel tissue is not getting enough oxygen and may already be dying. Studies have found that lactate values above roughly 1.5 to 2.0 mmol/L predict the need for bowel resection with moderate sensitivity and specificity.^{21 22} A normal lactate level does not guarantee that the bowel is fine, but it does significantly lower the probability of needing surgery for dead tissue.

Parastomal Hernias and Variceal Bleeding

People who have had bowel diverted to an ostomy, or stoma, are at risk for developing a hernia around the stoma site. These parastomal hernias are common and usually cause more nuisance than danger. But in patients who also have portal hypertension, typically from liver disease, a parastomal hernia can create a dangerous setup for variceal bleeding. The hernia compresses veins near the stoma, and the elevated pressure in the portal venous system forces blood into dilated, fragile parastomal veins. When those varices rupture, the bleeding can be severe and difficult to control with standard measures. In one case, CT imaging revealed varices within a large parastomal hernia that were fed by a branch of the superior mesenteric vein, and the bleeding was ultimately treated by threading a catheter to the varices and blocking them off with embolization material.²³ This is a niche scenario, but it underscores how hernias can interact with other medical conditions to produce bleeding that neither condition would typically cause on its own.

Who Is at Highest Risk

Several factors stack the odds in favor of a hernia eventually causing bleeding. For hiatal hernias, size matters most. A small hiatal hernia that is barely detectable on a barium swallow is unlikely to produce Cameron lesions, while a large one occupying several centimeters of the hiatal opening carries meaningfully higher risk. Regular NSAID use amplifies that risk because it strips away the stomach’s mucosal defenses, and alcohol use can muddy the diagnostic picture by producing its own gastritis and esophageal injury.⁵

For abdominal wall hernias, the risk of bleeding is tied mainly to incarceration and strangulation. Hernias that are large, irreducible, or have narrow necks are more prone to trapping bowel. Older adults and people with multiple comorbidities are more likely to present late, by which point the bowel may already be compromised.

If you are taking blood thinners, any type of hernia repair comes with elevated bleeding risk. The decision about whether to continue or pause anticoagulation before surgery involves balancing the clotting risk against the bleeding risk, and this is a conversation your surgeon and prescribing doctor need to have together. The evidence is clear that continuing these medications increases minor surgical bleeding, but stopping them is not always safe either, especially in patients on anticoagulants for mechanical heart valves or recent clots.

Why Cameron Lesions Get Missed

Despite being a well-known entity in gastroenterology textbooks, Cameron lesions remain underdiagnosed. Part of the reason is that many patients with hiatal hernias have overlapping conditions like reflux disease, peptic ulcers, and gastritis, all of which can independently cause bleeding and may satisfy the endoscopist’s search for an explanation without prompting a careful look at the diaphragmatic pinch point. Alcohol use, NSAID use, and acid reflux are so common in these patients that the initial differential diagnosis is crowded, and a subtle linear erosion on a gastric fold can easily be passed over.⁴

The other issue is that Cameron lesions do not always look dramatic. Peptic ulcers tend to be obvious craters; Cameron erosions are often shallow, linear, and confined to the tops of mucosal folds. Occult bleeding from them can go on for years, with the patient cycling through iron supplements and transfusions without anyone identifying the source. The diagnosis is usually made during an upper endoscopy specifically requested because of refractory anemia, and it requires the endoscopist to examine the hernia sac carefully with retroflexion. If the hernia is large enough and the anemia severe enough, surgical repair of the hernia itself tends to resolve the bleeding and restore hemoglobin levels over time.¹⁷