Visual journey · Rhabdomyolysis
Rhabdomyolysis is the breakdown of muscle fibers. As the fibers break apart, they release myoglobin, a muscle protein, into the blood. Follow it from the thigh, marked in red, to the kidneys, marked in blue.
Body → muscle
At the top, a muscle cut open shows how it’s divided into fascicles, bundles wrapped in connective tissue. In the middle, an opened fascicle reveals its fibers. At the bottom is a single muscle fiber, a long, cylindrical cell.
Muscle → fiber
That membrane is called the sarcolemma. Inside the fiber is myoglobin, a protein that stores oxygen so the muscle can keep working. If the sarcolemma tears, myoglobin and other substances inside the fiber leak into the blood.
Blood → kidney
This is what a kidney affected by rhabdomyolysis looks like under the microscope: damaged tubules with material built up inside them. Below, you’ll see step by step how myoglobin gets there.
Follow the chain of eventsThe journey marks a thigh muscle and both kidneys on the body; shows how a muscle divides into fascicles and fibers; zooms in on one fiber to point out its membrane, the sarcolemma; and ends with damaged kidney tubules seen under the microscope.
How it happens, step by step
When many fibers break down, a lot of myoglobin reaches the bloodstream. The kidneys filter it out, and inside their tubules it can form plugs and damage the cells that line them.
Kidney damage is a common complication of rhabdomyolysis, but it doesn’t happen to everyone.
Necrotic fiberPale and granular: it has diedThis biopsy comes from the thigh of a person whose rhabdomyolysis was caused by a statin, a cholesterol-lowering medicine. It’s stained with hematoxylin and eosin, the routine stain that colors muscle pink and nuclei purple. The surrounding fibers keep their polygonal shape. The marked fiber is pale and granular: it’s a necrotic fiber, a muscle cell that has died.
GlomerulusEach nephron’s filterEach kidney contains many nephrons like the one in this drawing. Each nephron begins at a glomerulus, which filters the blood, and continues into a tubule that returns what the body needs to the bloodstream.
Myoglobin is a small protein, so it passes through the glomerulus and into the tubule. Normally the tubule takes it back up, but when too much arrives, the tubule can’t keep up.
The third step happens inside the tubule. See it under the microscope.
Inside the tubule
Switch between three microscope images: healthy tubules, damaged tubules, and the same damaged kidney treated with a stain that turns myoglobin brown.
The cortex of a normal human kidney, stained with hematoxylin and eosin. Cut crosswise, each tubule is a ring of pink cells with purple nuclei surrounding a small central space called the lumen.
Granular castMaterial filling the tubuleA kidney biopsy from a person with rhabdomyolysis. The tubules look dilated, and their cells are flattened. Inside is granular material: casts, which take the shape of the tubule as they form inside it and can block it.
Myoglobin castThe stain turns it brownOn the same biopsy, immunohistochemistry, a stain that uses antibodies, colors myoglobin brown. The casts filling the tubules stain brown, which shows that the material came from muscle.
Myoglobin binds to a protein made by the tubule itself, forming those casts. It also damages the tubule’s cells directly.
The damage starts in a muscle fiber. The evidence turns up in the kidney.
Key takeaways
Some habits lower your risk, and recognizing rhabdomyolysis early means treatment can start sooner. It’s worth knowing this before it happens to you.
Muscle pain or cramps far worse than you’d expect; dark urine the color of tea or cola, or urinating much less than usual; or weakness that keeps you from finishing activities you used to be able to do. These signs can appear hours or days after the muscle injury, and they can be mistaken for heat cramps or dehydration.
Symptoms alone can’t confirm it. Doctors measure creatine kinase (CK), an enzyme that leaks out of damaged muscle, and repeat the test to see whether the level is rising or falling. A urine dipstick can’t rule out rhabdomyolysis: myoglobin is cleared quickly and may not show up.
Intense exertion, such as running a marathon, can cause it. So can extreme heat, hard blows to the body, and certain drugs and medications, including statins.
Physically demanding work, some infections, and supplements such as creatine or ephedra also raise the risk.
Every medical claim and every image in this journey links to a source you can open.
In the diagrams and micrographs, printed labels, arrows, and letters were removed with code, without redrawing any tissue. Brightness was matched between the normal and damaged kidney images, and the markers you see on this page were drawn on top.
The normal kidney image comes from the Human Protein Atlas, from a normal-looking area of a human surgical specimen. It serves as a reference for what healthy tissue looks like, not as a before-and-after comparison. The hematoxylin and eosin image of the injury and the myoglobin stain come from the same published kidney biopsy, from a case of rhabdomyolysis associated with COVID-19. The muscle biopsy comes from a different published case, in which a statin caused the rhabdomyolysis.
This journey explains how rhabdomyolysis develops and what its warning signs are. It doesn’t diagnose the condition, replace a medical evaluation, or recommend treatment for any individual.
Open-access sources, verified on October 2, 2026.
