A healthy human spleen is a soft, dark purple organ roughly the size and shape of an avocado or a clenched fist. It sits tucked behind your left ribcage, nestled between your stomach and your left kidney, where you’d never see or feel it under normal circumstances. Despite being one of the less talked-about organs, it has a distinctive appearance both on the outside and when cut open.
Size, Shape, and Color
A normal adult spleen measures up to about 12 centimeters long (roughly 5 inches) and weighs around 70 grams, or about 2.5 ounces. It’s oblong and slightly curved, with a smooth outer surface covered by a thin but tough capsule. The color is a deep reddish-purple, reflecting the enormous volume of blood flowing through it at any given moment. The texture is spongy and soft, somewhat like a dense piece of liver.
Men tend to have slightly larger spleens than women across all age groups. The organ also changes size over a lifetime. In a 3-month-old baby, the spleen is no more than 6 centimeters long. It grows steadily through childhood, reaching about 11 centimeters by age 10. By the mid-teens, it tops out at roughly 12 to 13 centimeters. After age 60, splenic weight gradually decreases.
What It Looks Like Inside
If you slice a spleen open, you’ll see two distinct types of tissue. The bulk of the interior is called red pulp, which is exactly what it sounds like: a deep red, spongy network of blood vessels and tissue that filters your blood, removing old or damaged red blood cells. Woven throughout the red pulp are small, pale, whitish-gray clusters called white pulp. These are patches of immune tissue, essentially tiny lymph nodes embedded inside the organ. They detect and respond to infections circulating in your bloodstream.
The white pulp appears as scattered pale dots against the deep red background, each one centered around a tiny artery. When your immune system is actively fighting something off, these white pulp clusters can enlarge and develop visible lighter centers where immune cells are multiplying rapidly.
How It Appears on Imaging
Most people wondering what a spleen looks like will encounter it on an ultrasound or CT scan rather than in person. On ultrasound, a healthy spleen appears as a smooth, uniformly gray crescent shape. Higher-resolution ultrasound can sometimes reveal a subtle speckled pattern created by the alternating red and white pulp, but on a standard scan it looks homogeneous.
On a CT scan with contrast dye, the spleen often shows a striking striped or mottled pattern during the first pass of dye through the organ. This “zebra spleen” appearance is completely normal and happens because blood flows through different parts of the spleen at different speeds. Within a minute or two, the contrast evens out and the spleen looks uniform again. Radiologists expect this pattern, so it’s not a sign of disease.
What an Enlarged Spleen Looks Like
When the spleen swells beyond its normal size, a condition called splenomegaly, it can change dramatically. A mildly enlarged spleen may simply look like a bigger version of itself. But in severe cases, the organ can grow to 30 times its normal size, expanding downward out of the ribcage and across the abdomen. At that point, it’s large enough to press against the stomach (causing you to feel full after just a few bites) and even crowd the left kidney.
Doctors check for an enlarged spleen during a physical exam by pressing below the left ribs. A normal spleen can’t be felt at all. If it’s palpable more than 8 centimeters below the rib margin, the enlargement is considered massive. The color of an enlarged spleen can shift depending on the cause, sometimes appearing more congested and darker due to trapped blood, or paler if infiltrated by abnormal cells.
Accessory Spleens
About 1 in 7 people (roughly 14.5%) have one or more accessory spleens, which are small extra nodules of splenic tissue located near the main organ. These are usually round, pea-sized, and the same dark reddish-purple color as the spleen itself. Most sit right at the point where blood vessels enter and exit the spleen. They function identically to the main organ and are almost always discovered incidentally on imaging done for unrelated reasons. On a CT scan, they look like miniature versions of the spleen and can occasionally be mistaken for enlarged lymph nodes.
After Injury or Rupture
Because the spleen is so blood-rich and relatively fragile, it’s the most commonly injured abdominal organ in blunt trauma. A damaged spleen looks visibly different depending on severity. Minor injuries produce small tears in the outer capsule less than a centimeter deep, with a thin layer of blood collecting just beneath the surface. This subcapsular blood collection, or hematoma, appears as a dark, fluid-filled crescent hugging the organ’s surface.
More severe injuries create deeper lacerations that expose the spongy interior, with active bleeding turning the surrounding area a deep crimson. In the most extreme cases, the spleen can be completely shattered into fragments, losing its recognizable shape entirely. On a CT scan, these injuries show up as irregular dark areas within or around the normally uniform organ, with free blood appearing as bright white streaks when contrast dye is used.