Your kidneys are on both sides of your body. You have two kidneys, one on the left and one on the right, positioned toward the back of your abdomen just below your rib cage. They sit against the back muscles on either side of your spine, roughly between the lowest rib and the waist.
Exact Position in the Body
Both kidneys are tucked behind the abdominal cavity in a region called the retroperitoneal space, which is the area behind the tissue lining your abdomen. This means they’re closer to your back than your belly button. Specifically, they sit between the level of your lowest thoracic vertebra (the bottom of your rib cage) and your third lumbar vertebra (upper lower back).
Each kidney is about the size of a fist. The left kidney measures roughly 11.2 cm long, while the right is slightly smaller at about 10.9 cm. They’re partially shielded by your 11th and 12th ribs, which is why kidney pain tends to show up in the flank area just below the ribs rather than in the lower back where people often expect it.
Why the Right Kidney Sits Lower
Although both kidneys are roughly at the same height, the right kidney typically sits a little lower than the left. The reason is straightforward: your liver, a large organ, sits directly above the right kidney and pushes it down slightly. The left kidney doesn’t have this pressure from above, so it stays a bit higher.
This small difference is completely normal and doesn’t affect how either kidney functions. It does mean that on imaging scans, your two kidneys won’t line up perfectly, which is expected.
What Surrounds Each Kidney
Each kidney is surrounded by a cushion of fat and wrapped in a tough, elastic sheath of connective tissue. This fat layer is thickest along the kidney’s edges and helps absorb shock. On top of each kidney sits a small adrenal gland, which produces hormones like cortisol and adrenaline but is a completely separate organ.
The right kidney’s front surface is in close contact with the liver, part of the small intestine, and a section of the colon. The left kidney neighbors the stomach, spleen, pancreas, and descending colon. These relationships explain why problems in the kidneys can sometimes produce symptoms that feel like they’re coming from the stomach or digestive tract.
How to Tell Kidney Pain From Back Pain
Because the kidneys sit against the back muscles, kidney pain and muscular back pain can feel confusingly similar. The key differences come down to location, behavior, and what makes it better or worse.
Kidney pain is typically felt in the flank, the area on either side of your spine just beneath the ribs and above the hips. It tends to stay in one spot, though it can spread to the lower abdomen or inner thighs. Importantly, kidney pain does not get worse or better when you move, stretch, or change positions. It also doesn’t improve on its own without treatment.
Muscular back pain, by contrast, usually shifts with movement. Bending, twisting, or pressing on the sore area changes the intensity. It also tends to respond to rest, ice, or over-the-counter pain relief. If you have pain in the flank area that stays constant regardless of how you move, that pattern points more toward a kidney issue like a stone or infection than a pulled muscle.
Anatomical Variations
Not everyone has two kidneys in the standard position. About 1 in 400 to 1 in 700 people are born with a horseshoe kidney, where the two kidneys are fused together at the bottom, forming a U-shape. This usually sits lower in the abdomen than typical kidneys and is often discovered incidentally during imaging for something else. Most people with a horseshoe kidney have no symptoms and need no treatment.
In rarer cases, a kidney can develop in an unusual location (called an ectopic kidney), sitting in the pelvis or even on the same side as the other kidney. Some people are born with only one kidney. These variations are usually harmless, though they’re worth knowing about if you ever need abdominal surgery or imaging.