Cullen sign is a bluish-brown discoloration of the skin around the belly button, caused by blood leaking from deep inside the abdomen into the surrounding tissue. It’s relatively rare but clinically significant: when it appears alongside acute pancreatitis, it’s associated with mortality rates as high as 40%. The sign itself isn’t a disease but a visible warning that something serious is happening internally.
What It Looks Like
The discoloration typically starts as a faint blue or purple bruise surrounding the navel, then deepens to a brownish-blue over time. It can spread outward from the belly button in an irregular pattern. Unlike a bruise from an injury, there’s no tenderness at the skin surface because the bleeding originates deep within the abdomen. The color follows the same progression as any bruise, shifting from purple to green to yellow as the blood breaks down, but the location around the navel is what makes it distinctive.
How Blood Reaches the Skin Surface
The belly button isn’t just a surface feature. It’s connected to deeper abdominal structures by a band of tissue called the falciform ligament, which runs from the navel up to the liver. When bleeding occurs in the retroperitoneum (the space behind the abdominal organs, near the kidneys and pancreas), blood can track along this ligament like fluid following a channel. It eventually seeps into the fat and tissue just beneath the skin around the navel, producing the visible bruising.
This is why Cullen sign takes time to appear. In acute pancreatitis, the discoloration typically develops two to three days after the initial episode. The blood needs time to travel from its source deep in the abdomen to the surface tissue.
Conditions That Cause It
Acute pancreatitis is the most widely recognized cause, particularly severe necrotizing pancreatitis where the pancreatic tissue is actively breaking down and bleeding. But Cullen sign is not specific to pancreatitis. It shows up in only about 1% of pancreatitis cases, and in a large study of 770 patients, just nine had it. The sign tells you there’s internal bleeding, not where it’s coming from.
Other conditions that can produce Cullen sign include:
- Ruptured ectopic pregnancy: bleeding from a fertilized egg implanted outside the uterus
- Ruptured abdominal aortic aneurysm: a burst in the body’s largest artery, which can flood the retroperitoneum with blood
- Perirenal hemorrhage: bleeding around the kidneys, sometimes without an obvious cause
- Splenic rupture or abdominal trauma: any event that causes significant bleeding into the abdominal cavity
In one documented case, a ruptured aortic aneurysm (with the aorta dilated to 6 cm) presented with both Cullen sign and its companion sign on the flanks. Ruptured aneurysms are misdiagnosed roughly 30% of the time as other conditions like kidney stones or bowel problems, so visible signs like periumbilical bruising can be a critical clue.
Cullen Sign vs. Grey Turner Sign
These two signs often appear together and share the same underlying mechanism: internal bleeding that tracks to the skin surface. The difference is location. Cullen sign appears around the belly button because blood follows the falciform ligament forward. Grey Turner sign appears on the flanks (the sides of the abdomen between the ribs and hips) because blood spreads from the retroperitoneum backward, moving along the muscles of the lower back to reach the skin.
When both signs are present simultaneously, it generally indicates a larger volume of internal bleeding, since the blood has found multiple pathways to the surface. Both carry similar prognostic weight.
Why It Matters for Prognosis
Cullen sign is uncommon, but when it does appear, it signals trouble. In pancreatitis specifically, the combination of Cullen sign and Grey Turner sign is associated with up to 40% mortality. That number reflects the severity of the underlying bleeding rather than the bruising itself. Patients who develop enough internal hemorrhage for blood to visibly reach the skin surface are, by definition, dealing with a more dangerous version of whatever is causing it.
The sign is also a delayed indicator. Because it takes days to develop, it doesn’t help with early diagnosis. By the time the bruising is visible, the patient is typically already in a hospital setting being treated for the underlying condition. Its value lies in confirming that significant hemorrhage has occurred and in prompting more aggressive monitoring or imaging to assess the extent of damage.
How It’s Named
The sign is named after Thomas Cullen, a gynecologist who first described periumbilical discoloration in 1918 in the context of a ruptured ectopic pregnancy. It was only later associated with pancreatitis and other causes of retroperitoneal bleeding. Grey Turner independently described flank discoloration in 1920 in a patient with pancreatitis, and the two signs have been linked in medical teaching ever since.