Cullen’s sign is bruising and swelling around the belly button that signals internal bleeding in the abdomen. It appears when blood tracks from deep within the abdomen to the surface of the skin, and it’s considered a red flag for serious conditions, most commonly severe acute pancreatitis. The sign is rare, showing up in only about 1% of pancreatitis cases, but when it does appear, it carries a mortality rate of up to 40%.
What Cullen’s Sign Looks Like
The hallmark is discoloration of the skin in the area immediately surrounding the belly button. The color depends on how much internal bleeding is present and how long it’s been occurring. Mild bleeding tends to produce yellow or greenish-yellow bruising, while more severe bleeding causes darker discoloration: brown, deep blue, purple, or even black. These color changes follow the same pattern as any bruise, shifting as red blood cells break down over time.
Along with the color change, the skin in that area often feels swollen and puffy. The bruises may be tender or painful to the touch. Because the blood has to travel from deep inside the abdomen to reach the surface, Cullen’s sign doesn’t appear instantly. It typically develops hours to days after the internal bleeding begins, which means it’s a delayed indicator rather than an early warning.
How Blood Reaches the Skin Surface
The bruising isn’t caused by a direct injury to the belly button area. Instead, blood or enzyme-rich fluid leaks from an organ deep in the abdomen (most often the pancreas) into the space behind the abdominal lining. From there, the fluid tracks along a specific anatomical route: it follows a ligament that connects the liver to the abdominal wall and runs directly to the belly button. This ligament acts like a highway, funneling the hemorrhagic fluid to the fatty tissue just beneath the skin around the navel, where it becomes visible as a bruise.
This pathway explains why the bruising is so specifically located. The belly button is a natural weak point in the abdominal wall where ligaments converge, making it the place where internal bleeding is most likely to show through.
Conditions That Cause It
Thomas Cullen first described this sign in 1918 in a patient with a ruptured ectopic pregnancy, and it’s still most commonly taught in the context of acute pancreatitis. But the common thread across all reported cases is the same: blood collecting in the retroperitoneal space, the area behind the abdominal lining.
Conditions linked to Cullen’s sign include:
- Severe acute pancreatitis, particularly necrotizing pancreatitis where pancreatic enzymes destroy surrounding tissue and cause hemorrhage
- Ruptured ectopic pregnancy, where a pregnancy outside the uterus bleeds into the abdominal cavity
- Rectus sheath hematoma, a collection of blood within the abdominal wall muscles
- Splenic rupture
- Perforated duodenal ulcer
- Abdominal trauma, including injury to the pancreas
- Complications of blood-thinning medications
Rarer causes include amoebic liver abscess, massive ovarian enlargement, and certain abdominal cancers. Despite the wide range of possible causes, all share the same underlying mechanism of blood leaking into or through the retroperitoneal space.
Cullen’s Sign vs. Grey Turner’s Sign
Grey Turner’s sign is the closely related counterpart to Cullen’s sign, and the two are often mentioned together. While Cullen’s sign appears around the belly button, Grey Turner’s sign shows up as bruising along the flanks, the sides of the abdomen near the lower back. The difference comes down to the route the blood takes. In Grey Turner’s sign, blood spreads from behind the kidneys to the muscles along the side of the body rather than traveling forward along the liver’s ligament to the navel.
Both signs point to the same basic problem: significant internal bleeding in the abdomen. They can appear separately or together in the same patient. When either one shows up in someone with acute pancreatitis, it signals that the disease has progressed to a severe, necrotizing form. Together, they appear in roughly 1% of pancreatitis patients but are associated with mortality as high as 40%, making them markers of a particularly dangerous course.
What It Means for Severity
Cullen’s sign is not a diagnosis on its own. It’s a physical finding that tells clinicians the situation is serious. In pancreatitis specifically, its presence indicates that pancreatic enzymes have escaped the organ and caused hemorrhagic destruction of surrounding tissue, a process called necrotizing pancreatitis. This is the most dangerous form of the disease.
Because the sign takes time to develop, it won’t be present during the earliest hours of an illness. By the time bruising becomes visible around the belly button, the internal bleeding has been underway for a while. This is why Cullen’s sign is considered a prognostic indicator (a clue about how bad things are likely to get) rather than a diagnostic tool for catching disease early. Imaging, blood tests, and other assessments are far more useful for initial diagnosis. Cullen’s sign adds a visible, unmistakable confirmation that internal hemorrhage is occurring and that aggressive medical care is needed.