Rhabdomyolysis: a case-based approach

The presentation

Imagine an adult who has taken up intense exercise after a long break and pushed themselves very hard. Over the next day or two they develop severe muscle pain and stiffness, the muscles feel swollen and tender, and they are unusually weak. Then they notice their urine has turned a dark cola or tea colour. They may feel sick, feverish or generally unwell. The same picture can follow a fall in which someone lies unable to move for many hours, a crush injury, a serious infection, or a reaction to certain drugs. The combination of marked muscle pain and weakness with dark, brown or reddish urine is the classic warning pattern of rhabdomyolysis, and it is quite different from the ordinary aching that comes on after normal exercise and settles within a couple of days.

Why muscle breakdown is dangerous

Muscle cells are packed with proteins and minerals. When they break down in large numbers, these contents spill into the bloodstream. One protein, myoglobin, colours the urine dark and can clog and injure the kidneys, sometimes causing kidney failure. At the same time, potassium leaks out of the damaged muscle; a very high potassium level can upset the heart's rhythm dangerously. Fluid can also shift into the swollen muscle, leaving the rest of the body short of fluid and worsening the strain on the kidneys. This is why rhabdomyolysis is treated urgently, usually with fluids given into a vein to protect the kidneys and flush the myoglobin through, alongside blood tests to watch the potassium and kidney function closely and treatment of whatever triggered it.

When to call 999

Call 999 or go straight to A&E if someone has severe muscle pain and weakness together with dark, brown or reddish urine, or if they are passing very little or no urine. Also seek emergency help if there is chest pain, palpitations or an irregular heartbeat, breathlessness, confusion, fainting, or severe swelling and tightness of a limb, which can signal a dangerous build-up of pressure in the muscle. These features suggest the kidneys or heart may be affected and need urgent hospital treatment. Milder muscle aching after normal exercise, with pale urine and no weakness, is not an emergency. Do not try to 'flush it out' at home with extreme amounts of fluid and wait — if you have the warning pattern, get assessed, because the kidneys can be protected best when treatment starts early.

Common triggers and who is at risk

Several things can trigger rhabdomyolysis. Very intense or unaccustomed exercise is a well-known cause, especially in hot conditions or when someone is dehydrated. A crush injury or a long period lying still and unable to move — for example after a fall, a collapse, or being trapped — presses on muscle and starves it of blood. Some infections, very high temperatures, heavy alcohol or drug use, and rarely certain prescribed medicines can also injure muscle. People are more vulnerable if they are dehydrated, older and frail, or have an inherited muscle condition. Knowing these triggers helps: an older person found on the floor after many hours, or someone with severe muscle pain and dark urine after an extreme workout or a binge, should be checked rather than assumed to be simply stiff or tired.

The safe pathway

The practical rule is to watch the urine and the weakness, not just the ache. Ordinary muscle soreness after exercise is common, comes on within a day, eases with rest, and does not turn the urine dark. Rhabdomyolysis causes severe pain, genuine weakness, swollen tender muscles and dark brown or reddish urine, and needs urgent assessment with blood and urine tests. Severe features — very little or no urine, chest pain, palpitations, breathlessness, confusion or a tight, swollen limb — are a 999 emergency. Preventing it means building up exercise gradually, staying well hydrated especially in the heat, and seeking help early after a fall in which someone has been down for a long time. Most people recover well when it is caught early and the kidneys are protected in time.