Makindo Medical Notes

Related Subjects: |Hyperuricaemia |Acute and Chronic Gout |Allopurinol

Above the threshold of 6.8 mg/dl (410 µmol/l) the risk of serum UA crystallization increases significantly

About

• High levels of urate

Aetiology

• Increased cell turnover or Reduced excretion
• Urate is poorly solube so precipitates out
• Can happen in renal tubules - urate crystals

Normal Values

• 3.5 to 7.0 mg/dl (208–416 µmol/l) in men and postmenopausal women
• 2.6–5.7 mg/dl (155–339 µmol/l) in premenopausal women

Causes

• Renal failure
• Drugs: Cytotoxins, thiazides, loop diuretics, pyrazinamide.
• Increased cell turnover: Lymphoma, leukaemia, psoriasis, haemolysis
• Cell damage: muscle death (rhabdomyolysis, tumour lysis syndrome)
• Impaired excretion: Gout, CKD, lead nephropathy, hyperparathyroidism, pre-eclampsia
• Lesch–Nyhan syndrome (disorder of purine metabolism)

Clinical

• Underlying condition
• Renal colic

Investigations

• U&E : AKI
• Urate levels: elevated

In critically ill patients in ITU, hyperuricemia is an early marker of the severity of sepsis, as well as a predictor of AKI, ARDS and need for mechanical ventilation use and mortality

Management: Guidelines

• ACR (2012, 2020), 3E Initiative (2014) and EULAR (2016) recommendations for management of hyperuricemia in patients with acute and chronic gout
  • Start acute gout treatment in the first 24 hours: Use colchicine p.o. or NSAIDs p.o., or GCS p.o. i.a. as first-line agents in acute gout
  • Start ULT only after resolution of acute gout phase; however, if ULT was started before acute gout episode, do not discontinue
  • Use long-term ULT only in selected cases, i.e. in case of tophi/ chronic gouty arthropathy
  • Use allopurinol, febuxostat and probenecid as first-line agents and pegloticase as a second-line drug
  • Start allopurinol at a low dose and gradually escalate to a minimal effective dose Monitor UA levels during ULT
  • Treat to target (until all symptoms’ resolution and UA target level are achieved)
  • Maintain UA target level lifelong
  • Consider secondary gout prophylaxis with colchicine or NSAIDs
  • Screen patients with gout for common comorbidities associated with hyperuricemia
• Prevent High Uriac acid (UA): Allopurinol/Raburicase before chemotherapy
• Manage Urate induced AKI: IV fluids +/- IV Furosemide to get a good diuresis. If oliguria then consider haemodialysis.
• Renal Urate stones: 10% radiolucent. Commoner in hot climates. Risks are acid/concentrated urine. Commoner with chronic diarrhoea, distal small bowel disease, ileostomy, obesity, DM, chemotherapy, dehydration. Needs hydration. Potassium citrate or potassium bicarbonate raise pH > 6.7 dissolves some urate stones. Consider allopurinol (xanthine oxidase inhibitor).

References

• Pathophysiology of hyperuricemia and its clinical significance – a narrative review