Kidney pain typically hits in your back and side, in the area between your lower ribs and your hip. This region is called the flank, and it sits deeper than the muscles along your spine. Most people feel it on one side only, though both sides can hurt at the same time. Depending on the cause, the pain can stay in that spot or travel downward toward your lower belly, groin, or even your inner thigh.
Exact Location of Kidney Pain
Your kidneys sit just below your ribcage, one on each side of your spine, tucked behind your other organs. The spot where your lowest ribs meet your spine is called the costovertebral angle, and this is the epicenter of most kidney pain. If you reach behind you and press on either side of your back just below the ribs, you’re touching the area right over your kidneys.
Pain from a kidney stone or infection often starts at this costovertebral angle and radiates forward and downward. When a stone moves through the ureter (the tube connecting your kidney to your bladder), the pain can sweep around your side into your lower abdomen and down into your groin or, in men, the testicle. This traveling pattern is one of the clearest signs that the pain is coming from your urinary tract rather than from a muscle or spinal problem.
How It Feels Compared to Back Pain
The overlap between kidney pain and regular back pain trips a lot of people up. Musculoskeletal back pain usually centers over the spine in the middle or lower back, and it often gets worse or better when you change position, stretch, or press on the muscles. It can also radiate down your legs if a nerve is involved.
Kidney pain behaves differently. It tends to feel deeper, like it’s coming from inside rather than from the surface muscles. It doesn’t usually change when you shift positions or stretch. Back pain from a pulled muscle might ease when you lie down; kidney pain generally won’t. And kidney pain is more likely to come with other symptoms: changes in your urine, fever, nausea, or pain that wraps around toward your belly or groin.
What Different Kidney Problems Feel Like
Kidney Stones
Kidney stone pain is often described as one of the most intense pains a person can experience. It comes on suddenly, produces sharp or stabbing waves, and can shift location as the stone moves. The classic pattern starts in the flank and radiates down into the lower abdomen and groin. You may also notice blood in your urine (pink, red, or cola-colored) and a sharp, stabbing pain when urinating. The pain tends to come in waves because the tube carrying the stone contracts in spasms, temporarily spiking the pressure.
Kidney Infection
A kidney infection (pyelonephritis) produces a more constant, deep ache in the flank rather than sharp waves. It almost always comes with systemic symptoms: fever, chills, nausea or vomiting, and sometimes cloudy, dark, bloody, or foul-smelling urine. You may also feel a burning sensation when urinating and need to go frequently. The combination of flank pain plus fever is a strong signal that infection has moved beyond the bladder and into one or both kidneys.
Kidney Swelling From a Blockage
When urine can’t drain properly, fluid backs up and stretches the kidney, a condition called hydronephrosis. This typically causes a constant, dull ache in the flank from the stretching of the kidney’s outer capsule. Intermittent episodes of sharper pain can layer on top as the urinary tract contracts to try to push fluid past the blockage. Some people with hydronephrosis have no pain at all and only discover the swelling on an imaging scan done for something else.
Polycystic Kidney Disease
People with polycystic kidney disease, where fluid-filled cysts grow on the kidneys over time, report a wider spread of pain. The most commonly reported locations are the low back (about 71% of patients) and the abdomen (about 61%). Pain from a specific cyst tends to feel like a steady, nagging discomfort that worsens with standing and walking. Some people can point to the exact spot with one finger, often in the front of the abdomen rather than the back. The pain is typically described as dull, aching, or a sense of fullness, rated moderate on a pain scale, and lasting hours to days.
Why Kidney Pain Radiates
The kidney itself doesn’t have the same dense network of pain sensors that your skin does. Instead, the pain you feel comes primarily from the stretching of the kidney’s outer capsule or the walls of the ureter. These structures share nerve pathways with the lower chest and upper lower back, which is why kidney problems create pain in the flank. When a stone or blockage moves lower in the urinary tract, it activates nerve fibers that connect to areas progressively further down, which is why the pain can travel from your back all the way to your groin. This referred pain pattern is the reason kidney problems sometimes masquerade as hip, abdominal, or even testicular pain.
Signs the Pain Is Serious
Some combinations of symptoms with flank pain warrant prompt attention. Fever alongside flank pain raises concern for a kidney infection that could progress. Blood visible in your urine, whether pink, red, or dark brown, points toward a possible stone or other kidney issue. Pain so severe you can’t sit still or find a comfortable position is characteristic of a stone actively passing. Nausea and vomiting paired with flank pain can signal that the pain is visceral (organ-based) rather than muscular. And an inability to urinate despite the urge suggests a blockage that needs to be evaluated quickly.
A Quick Self-Check
You can get a rough sense of whether your pain lines up with kidney location by placing your hands on your back, just below the bottom edge of your ribcage, a few inches out from your spine on each side. That’s roughly where your kidneys sit. If pressing there or lightly tapping with a fist reproduces or worsens your pain, there’s a reasonable chance the kidneys are involved. Doctors use a more precise version of this same test during a physical exam to check for kidney tenderness.
Keep in mind that the flank is a busy neighborhood. Your lower ribs, spinal muscles, colon, and other structures share the space. Pain in this region isn’t automatically kidney-related. But pain that sits deep, doesn’t change with movement, and comes with urinary symptoms or fever is much more likely to be kidney-related than a simple muscle strain.