Kidney stone pain typically starts in the flank, the area on either side of your lower back just below the rib cage. From there, it can radiate downward into the lower abdomen, groin, and even the genitals, depending on where the stone is sitting in your urinary tract. The pain doesn’t stay in one place because the stone doesn’t stay in one place. As it moves, the location of your pain moves with it.
Where the Pain Starts
Most people first feel kidney stone pain in the flank. This is the soft area between your lower ribs and your hip, toward the back. The pain hits on whichever side the stone is on. A stone in the left kidney causes left-sided flank pain; a stone in the right kidney causes right-sided pain. At this stage, the stone is either still inside the kidney or has just entered the upper portion of the ureter, the narrow tube that connects each kidney to the bladder.
The pain is sharp, cramping, and intense. It comes in waves that can last anywhere from 20 to 60 minutes, with the worst of it typically hitting one to two hours after it begins. Between waves, you may feel a persistent dull ache. Unlike a pulled muscle or a stiff back, this pain doesn’t ease when you shift positions. Most people with kidney stones can’t get comfortable no matter how they sit, stand, or lie down.
How Pain Shifts as the Stone Moves
A kidney stone follows a predictable path: from the kidney, down the ureter, and into the bladder. As the stone travels, pain tends to migrate downward and forward. Patients commonly describe it as a flank pain that radiates toward the front of the abdomen, then into the pelvis and groin. The progression can take hours, days, or sometimes weeks, depending on the size of the stone and how quickly it moves.
When a stone reaches the middle section of the ureter, the pain often shifts to the lower abdomen. At this point, it can feel surprisingly similar to a stomachache or even appendicitis if the stone is on the right side. This is one reason kidney stones sometimes get misdiagnosed on the first visit to an emergency room.
Once a stone reaches the lowest part of the ureter, near where it connects to the bladder, you may notice new symptoms on top of the pain. Urinary urgency, difficulty urinating, and blood in the urine are common at this stage. The pain itself often settles deep in the groin or pelvis.
Referred Pain in the Groin and Genitals
One of the more alarming aspects of kidney stone pain is that it can be felt in areas that seem completely unrelated to the urinary tract. Men sometimes feel intense pain in the testicle or scrotum. Women may feel it in the labia. This happens because of shared nerve pathways: the same spinal nerves that supply sensation to the ureter also supply the genital area. When the brain receives pain signals along those shared nerves, it can misinterpret where the pain is coming from.
In some cases, a small stone lodged in the lower ureter causes pain felt only in the testicle, with no flank pain at all. This can lead to a confusing diagnostic picture, since testicular pain on its own doesn’t immediately suggest a kidney stone. If you’re experiencing sudden, unexplained pain in the groin or genitals along with any urinary changes, a stone in the lower ureter is a real possibility.
How to Tell It Apart From Back Pain
Because kidney stone pain often starts in the back, many people initially assume they’ve pulled a muscle or tweaked a disc. The differences are fairly distinct once you know what to look for.
- Position doesn’t help. Musculoskeletal back pain usually improves or worsens depending on how you move or sit. Kidney stone pain stays intense regardless of position.
- The pain moves. A sore muscle stays in one spot. Kidney stone pain migrates downward over time, from the flank toward the abdomen and groin.
- Accompanying symptoms differ. Back injuries often come with stiffness, muscle spasms, or tingling in the legs. Kidney stones come with nausea, blood in the urine, and urinary urgency.
- The quality is different. Musculoskeletal pain is typically a dull ache or soreness. Kidney stone pain is sharp, comes in waves, and can be severe enough to send you to the emergency room.
Why the Pain Is So Intense
Kidney stone pain isn’t caused by the stone cutting or scraping tissue, which is a common misconception. The real source of pain is pressure. When a stone blocks the ureter, urine backs up behind it, stretching the kidney and the tube itself. That stretching triggers intense spasms in the smooth muscle lining the ureter as it tries to push the stone along. The combination of pressure, swelling, and muscle spasm is what produces the waves of severe pain known as renal colic.
This also explains why small stones can hurt just as much as large ones. A tiny stone that perfectly plugs a narrow section of the ureter creates the same backup of pressure as a larger stone. The level of blockage matters more than the size of the stone.
Pain Locations at a Glance
- Stone in the kidney or upper ureter: Flank pain below the ribs on the affected side, often radiating to the back.
- Stone in the mid-ureter: Lower abdominal pain, sometimes mimicking gastrointestinal problems.
- Stone in the lower ureter near the bladder: Deep groin or pelvic pain, often with urinary urgency and frequency.
- Referred pain: Testicle, scrotum, or labia pain from shared nerve pathways, sometimes occurring without obvious flank pain.
Signs That Need Immediate Attention
Kidney stone pain on its own, while agonizing, is usually not dangerous. The stone will often pass with time, fluids, and pain management. But certain combinations of symptoms signal something more serious, like an infection behind a blocked stone. Fever or chills alongside kidney stone pain suggest a possible urinary tract infection that can escalate quickly. If the pain becomes truly unbearable and unmanageable, or if you stop being able to urinate, those are reasons to go to an emergency department rather than waiting it out.