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Renal & Urology

Rhabdomyolysis

Skeletal muscle necrosis floods the circulation with creatine kinase, myoglobin, potassium and phosphate: myoglobin obstructs and poisons the renal tubules, while potassium can stop the heart within hours.

In a nutshell

Rhabdomyolysis is skeletal muscle necrosis releasing creatine kinase, myoglobin and potassium; a creatine kinase above 950 units/L, five times the upper limit of normal, makes the diagnosis. Treat hyperkalaemia first, then give 500 mL crystalloid boluses titrated to reassessment, and examine the limbs hourly for compartment syndrome.

Classic presentation

A patient found after an overnight lie has tender swollen legs, cola-coloured urine, a creatine kinase in the tens of thousands and a potassium of 6.8 mmol/L.

Key points

  • Potassium release is steepest in the first 12 to 36 hours after muscle injury, so an acceptable result on arrival settles nothing.
  • Calcium falls early as it deposits in necrotic muscle, then rebounds to hypercalcaemia in recovery. Do not correct mild early hypocalcaemia.
  • Creatine kinase does not determine prognosis, and a peak level is a delayed and unreliable predictor of kidney injury.
  • Send a full blood count and clotting screen in every case: disseminated intravascular coagulation occurs and carries a poor prognosis.
  • Serum myoglobin can return to normal within 1 to 6 hours, so normal-coloured urine never excludes the diagnosis.
  • Creatinine rises disproportionately to urea, because damaged muscle releases creatine directly into the circulation.
  • Skeletal muscle tolerates warm ischaemia for about 2 hours; beyond that the damage is usually irreversible.
  • Non-operative management of a late-presenting compartment syndrome is an option, but only alongside renal assessment and protection.

First-line investigation

Serum creatine kinase, alongside an immediate 12-lead ECG and a potassium on a blood gas analyser, because hyperkalaemia is what kills first.

Management

Step 1: the potassium, before the fluid

  • ABCDE (airway, breathing, circulation, disability, exposure) assessment with continuous cardiac monitoring. Immediate 12-lead ECG and a potassium on a blood gas analyser.2,8
  • Potassium is mild at 5.5 to 5.9 mmol/L, moderate at 6.0 to 6.4, severe at 6.5 or more. Any hyperkalaemic ECG change is an emergency at any level.2
  • With ECG changes give calcium gluconate 10% 30 mL IV over 10 minutes. Repeat if the ECG has not improved within 5 to 10 minutes.2,10
  • In cardiac arrest or peri-arrest use calcium chloride 10% 10 mL over 5 minutes instead. Calcium protects the myocardium and removes no potassium.2,8
  • Potassium 6.0 mmol/L or more: 10 units soluble insulin in 50 mL glucose 50% (25 g) IV over 5 to 15 minutes into a large vein, then flush.2
  • If pre-treatment glucose is below 7.0 mmol/L, follow with glucose 10% at 50 mL/hour for 5 hours. Repeat potassium measurements at 1, 2, 4, 6 and 24 hours.2

Step 2: restore circulating volume

  • Resuscitate if systolic blood pressure is below 100 mmHg, heart rate above 90, capillary refill over 2 seconds, respiratory rate above 20, or NEWS 5 or more.5
  • NEWS is the National Early Warning Score, the standard UK observation chart score, where a higher total means a sicker patient.5
  • Give 500 mL crystalloid containing sodium 130 to 154 mmol/L in under 15 minutes; sodium chloride 0.9%, containing 150 mmol/L, meets that range.5,6,11
  • While hypovolaemia persists, reassess after each repeated bolus. Several litres may be required, occasionally as much as 10 litres.3,1
  • No UK guideline sets a rhabdomyolysis fluid rate or a urine-output target. Catheterise and chart hourly output; oliguria is under 0.5 mL/kg/hour.1,4
  • Stop and get help if breathlessness or pulmonary oedema develops during the infusion. NICE classes that as a critical incident.5
  • Stop the culprit: a statin or other myotoxic drug, or a constricting cast. Treat sepsis, seizures, heat illness or overdose on their own pathways.1,9

Step 3: the limb, and the kidney

  • Examine at-risk limbs hourly and document the findings each time. Pain out of proportion to the injury and pain on passive movement are the key signs.7
  • Release all circumferential dressings down to skin, elevate the limb, then re-examine within 30 minutes. Inconclusive signs mean senior surgical review.7
  • Diastolic blood pressure minus compartment pressure below 30 mmHg, or an absolute compartment pressure above 40 mmHg, means decompression.7
  • Once compartment syndrome is diagnosed, decompression is immediate. Discuss with plastic surgery within 24 hours and re-explore within 72 hours.7
  • Refer immediately for renal replacement therapy if hyperkalaemia, acidosis, uraemic pericarditis or encephalopathy, fluid overload or pulmonary oedema are not responding.4
  • Discuss stage 3 acute kidney injury, or any case with no clear cause, with nephrology within 24 hours.4

Step 4: what not to give, and what to watch

  • Do not give sodium bicarbonate, mannitol or loop diuretics to force urine output. None is recommended for rhabdomyolysis.4,1,3
  • The BNF lists no rhabdomyolysis indication for mannitol, and its only alkalinisation indication is oral, for urinary-tract discomfort.12,13
  • A separate indication still stands: bicarbonate for severe metabolic acidosis, a loop diuretic for fluid overload while awaiting dialysis.4,13
  • Detect acute kidney injury by a creatinine rise of 26 micromol/L within 48 hours, a 50% rise within 7 days, or urine output under 0.5 mL/kg/hour for over 6 hours.4
  • Repeat creatine kinase, potassium, calcium, phosphate and creatinine until falling. Watch for rebound hypercalcaemia during recovery.1,4
  • Investigate recurrent unexplained episodes for inherited or metabolic myopathy, and safety-net for dark urine, weakness or reduced urine output.1

Exam traps

  • A haem-positive dipstick with no red cells on microscopy is myoglobin, not blood. Dipsticks cannot tell the two haem pigments apart.
  • Most patients never show the complete classic triad, and dark urine is often absent. Its absence does not lower the suspicion.
  • Calcium is the right treatment for hyperkalaemic ECG changes here, but check the calcium first: it may already be rebounding upwards.
  • Sodium bicarbonate and mannitol are traditional, unproven and not licensed for this. Large bicarbonate doses can worsen the hypocalcaemia.
  • Regional anaesthesia and patient-controlled opiates mask compartment syndrome. A rising analgesia requirement is the warning sign.
  • Renal replacement therapy is triggered by refractory complications and the whole clinical picture, never by an isolated creatine kinase or creatinine.
  • Creatine kinase is the diagnostic test, not the severity test. Escalation is driven by potassium, urine output and creatinine, never by the creatine kinase number.

Illustrations

Dark urine in rhabdomyolysisA urine specimen with the dark tea-brown appearance of myoglobinuria in rhabdomyolysis.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. Royal College of Emergency Medicine, RCEMLearning: Acute Rhabdomyolysis (UK emergency medicine reference. Source of the creatine kinase definition (a rise to more than five times the upper limit of normal; reference range 30 to 190 units/L, so above 950 units/L is diagnostic), that creatine kinase does not determine prognosis, the 12 to 36 hour peak of potassium release, early hypocalcaemia with later hypercalcaemia, the myoglobin half-life of 1 to 6 hours, the requirement for a full blood count and clotting screen in every case, and the statements that sodium bicarbonate and mannitol are unproven)Published 11 Feb 2022 | Updated 16 Mar 2026
  2. UK Kidney Association, Clinical Practice Guideline: Treatment of Acute Hyperkalaemia in Adults (Final version October 2023, published 19 December 2023. Source of the severity bands (mild 5.5 to 5.9, moderate 6.0 to 6.4, severe 6.5 mmol/L or more), the calcium salt doses in guidelines 16.2a and 16.2b, the insulin-glucose regimen in guidelines 16.3.1 to 16.3.3, and the schedule of potassium rechecks at 1, 2, 4, 6 and 24 hours in guideline 17.1.2. Same document and thresholds as the hyperkalaemia chapter)Published 19 Dec 2023
  3. British Consensus Guidelines on Intravenous Fluid Therapy for Adult Surgical Patients (Recommendation 28 is the only formal UK recommendation identified for this condition: patients at risk of acute kidney injury secondary to rhabdomyolysis must receive aggressive fluid resuscitation with an isotonic crystalloid to correct hypovolaemia, with insufficient evidence to recommend a specific crystalloid. It also states there is limited evidence for alkalinising the urine. It specifies no volume or rate. Cited only for these points: its hydroxyethyl starch recommendations are superseded, starch having been withdrawn from UK use)
  4. NICE NG148, Acute kidney injury: prevention, detection and management (Published 18 December 2019, last updated 16 October 2024. Recommendation 1.1.1 for oliguria as urine output under 0.5 mL/kg/hour, 1.3.1 for the detection criteria, 1.4.2 for urine dipstick, 1.5.3 and 1.5.4 for loop diuretics, 1.5.8 and 1.5.9 for renal replacement therapy, and 1.5.15 for nephrology referral within 24 hours. Linked to the NICE PDF, which is where every one of those numbers was read. NG148 defers acute kidney injury staging to the (p)RIFLE, AKIN and KDIGO definitions rather than publishing its own stage bands)Published 18 Dec 2019 | Updated 16 Oct 2024
  5. NICE CG174, Intravenous fluid therapy in adults in hospital (Published 10 December 2013, last updated 5 May 2017. Recommendation 1.2.1 for the indicators of a need for urgent resuscitation, 1.2.4 and 1.2.5 for the monitoring schedule, and table 1 which classes pulmonary oedema during intravenous fluid as a critical incident, all read on this page. The resuscitation recommendation 1.3.1 is cited separately to the NICE surveillance report below, which prints its number alongside its text)Published 10 Dec 2013 | Updated 5 May 2017
  6. NICE, 2020 exceptional surveillance of intravenous fluid therapy in adults in hospital (NICE guideline CG174) (Reproduces CG174's resuscitation recommendation with its number: the resulting recommendation (1.3.1) was to use crystalloids that contain sodium in the range 130 mmol/L to 154 mmol/L for intravenous fluid resuscitation. Cited so that the 1.3.1 locator used in this chapter can be checked on a page that carries it; the full wording, including the bolus of 500 mL over less than 15 minutes, is reproduced in CG174's key priorities for implementation)
  7. British Orthopaedic Association Standard, Diagnosis and Management of Compartment Syndrome of the Extremities (Revised July 2025; replaces the archived Compartment Syndrome of the Limbs standard. Standard 5 for hourly documented assessment, standard 7 for releasing circumferential dressings and re-evaluating within 30 minutes, standard 9 for immediate decompression on diagnosis, standard 11 for plastic surgery discussion within 24 hours and re-exploration within 72 hours, and the footnote giving a diastolic-minus-compartment pressure difference below 30 mmHg and an absolute pressure above 40 mmHg)Published 1 Jul 2025
  8. Resuscitation Council UK, 2025 Resuscitation Guidelines: Special circumstances (UK emergency treatment of hyperkalaemia and hyperkalaemic cardiac arrest, including the ECG changes and the calcium and insulin-glucose steps. Same document cited by the hyperkalaemia chapter)Published 27 Oct 2025
  9. NICE NG253, Suspected sepsis in people aged 16 or over (Published 19 November 2025, last reviewed 5 December 2025. Partially updates and replaces NG51. Cited for the sepsis arm when infection is the precipitant)Published 19 Nov 2025
  10. BNF, Calcium gluconate (Acute severe hyperkalaemia (plasma-potassium concentration 6.5 mmol/litre or greater, or in the presence of ECG changes): 30 mL of calcium gluconate 10% by slow intravenous injection, repeated if there is no improvement in the ECG within 5 to 10 minutes)
  11. BNF, Sodium chloride (Prescribing and dispensing information: sodium chloride 0.9% intravenous infusion contains sodium and chloride each 150 mmol/litre, which places it inside the 130 to 154 mmol/litre range NICE CG174 specifies for resuscitation fluid)
  12. BNF, Mannitol (The intravenous indications are cerebral oedema and raised intra-ocular pressure only. Rhabdomyolysis and pigment nephropathy are not listed indications, and anuria and severe dehydration are contra-indications to intravenous use)
  13. BNF, Sodium bicarbonate (Alkalinisation of urine is an oral indication for relief of discomfort in mild urinary-tract infections, not a rhabdomyolysis indication. The intravenous indication is severe metabolic acidosis, dosed to the body base deficit)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.