Rhabdomyolysis and Renal Problems

The typical presentation is significant muscle pain and weakness after unaccustomed or very intense exercise or heavy eccentric loading, made worse by heat and dehydration. Dark, cola-coloured urine is a classic sign but is present in only a minority. Diagnosis rests on significant muscle symptoms after exercise together with a raised serum creatine kinase (CK), commonly at least five times the upper limit of normal, rather than on a creatine kinase level in isolation. Myoglobin is released too but is cleared rapidly and is not a reliable marker.

A urine dipstick that is positive for blood but shows few or no red cells on microscopy indicates pigmenturia, which may be myoglobin or haemoglobin; the clinical setting supports myoglobinuria but does not prove it. Alongside the creatine kinase, renal function and electrolytes are checked, looking for acute kidney injury (AKI), a raised potassium, and disturbances of calcium and phosphate. The main complications are AKI, hyperkalaemia, and, less often, compartment syndrome and disseminated intravascular coagulation. Importantly, kidney risk depends on renal function, hydration, electrolytes, comorbidity and the overall clinical condition, and in exertional cases it may not correlate closely with the height of the creatine kinase, so a single very high value is interpreted in context rather than as an automatic marker of harm.

The cornerstone of management is fluids, given as individualised isotonic fluid resuscitation with monitoring of urine output, renal function, electrolytes and for fluid overload; routine urinary alkalinisation with bicarbonate is not recommended. Outpatient management is appropriate when the athlete is clinically well, can maintain oral hydration, has normal renal function and electrolytes, has no high-risk features and has reliable early follow-up, rather than being decided by the height of the creatine kinase alone.

Certain features are red flags that the episode is more than a one-off response to hard exercise, and prompt referral and investigation: recurrent episodes, a creatine kinase out of proportion to the exercise done or that fails to fall, a personal or family history of muscle problems or anaesthetic reactions, exertional collapse, and drug triggers such as statins. These point towards an underlying metabolic myopathy or malignant hyperthermia susceptibility. Sickle cell trait deserves separate mention: exertional sickling is a distinct cause of exertional collapse, which may coexist with rhabdomyolysis, and it is reduced by gradual conditioning and acclimatisation, adequate hydration, recovery between maximal efforts and stopping promptly if unusual weakness or cramping develops. There is no single validated return-to-sport protocol; low-risk athletes can return gradually once clinically recovered, with normal renal function and urinalysis and a substantial fall in creatine kinase, commonly below five times the upper limit or near their baseline, while recurrent or disproportionate cases need specialist assessment first.

Beyond rhabdomyolysis, exercise commonly produces changes in the urine that need careful interpretation. Blood on a dipstick after intense exercise is often benign, but benign exercise haematuria is not diagnosed from a single post-exercise dipstick: urinalysis is repeated after a period without exercise, and infection, renal symptoms and risk factors are assessed. Foot-strike haemolysis causes haemoglobinuria rather than true red-cell haematuria, and exercise proteinuria is usually transient and benign. Unexplained visible (macroscopic) haematuria is treated more urgently: in an adult aged 45 or over it warrants urgent referral on a suspected cancer pathway, and visible haematuria at any age needs appropriate assessment to exclude stones, infection and tumour.

Medicines matter too. Routine or prophylactic use of a non-steroidal anti-inflammatory drug (NSAID) during prolonged endurance exercise is avoided, because with dehydration it reduces renal blood flow and increases the risk of acute kidney injury; this does not mean every clinically indicated dose is prohibited, but rather that non-essential use around endurance events is discouraged. Fluid balance problems such as exercise-associated hyponatraemia are a separate endurance issue and are addressed on their own page. Overall, most exercise-related urinary changes are benign, but persistent or disproportionate findings, and visible haematuria, are assessed rather than dismissed.

• •Diagnosis needs significant muscle symptoms after exercise plus a raised creatine kinase (commonly at least five times the upper limit), not a creatine kinase level alone; dark urine occurs in only a minority.
• •A dipstick positive for blood with few red cells indicates pigmenturia (myoglobin or haemoglobin); check renal function, potassium, calcium and phosphate.
• •Fluids are the cornerstone, as individualised isotonic resuscitation with monitoring for urine output, renal function, electrolytes and fluid overload; alkalinisation is not routine.
• •Outpatient care suits a well athlete with oral hydration, normal renal function and electrolytes, no high-risk features and reliable follow-up; kidney risk may not track the creatine kinase.
• •Red flags (recurrent, disproportionate or non-falling creatine kinase, family history, exertional collapse, drug triggers) prompt referral; exertional sickling is a distinct cause of collapse.
• •Do not diagnose benign exercise haematuria from one dipstick; unexplained visible haematuria in an adult aged 45 or over needs urgent suspected-cancer-pathway referral, and routine NSAID use during endurance exercise is avoided.