Urate Metabolism & Pathogenesis
Gout is a crystal-induced arthropathy caused by monosodium urate (MSU) crystal deposition in joints, soft tissues, and kidneys. It results from sustained hyperuricaemia.
Purine Pathway
- Dietary & endogenous purines → hypoxanthine → xanthine
- Xanthine oxidase converts xanthine → uric acid
- Uric acid is the final metabolite in humans (no uricase enzyme)
- Excreted predominantly by the kidney (~70%) and GI tract (~30%)
Hyperuricaemia Thresholds
- Serum urate >360 μmol/L in women
- Serum urate >420 μmol/L in men
- MSU supersaturation → crystal nucleation
- Crystals trigger NLRP3 inflammasome → IL-1β cascade → acute inflammation
Triggers & Risk Factors
Dietary
- Red meat & organ meats (offal)
- Shellfish & oily seafood
- Beer & spirits (ethanol increases urate production)
- High-fructose corn syrup / sugary drinks
Medications
- Diuretics (thiazide & loop) — reduce renal urate excretion
- Low-dose aspirin (<2g/day) — reduces urate excretion
- Ciclosporin — reduces GFR, raises urate
- Pyrazinamide, ethambutol, niacin
Other Factors
- Dehydration (acute or chronic)
- Male sex, older age, post-menopausal women
- Obesity, metabolic syndrome, CKD, hypertension
- Rapid weight loss / starvation (ketoacidosis competes with urate excretion)
Clinical Presentation — Acute Attack
- Sudden onset, often nocturnal (temperature drop promotes crystallisation)
- Exquisitely tender — patient cannot bear weight or touch
- Overlying erythema, warmth, swelling
- Resolves spontaneously over 7–14 days if untreated
Joint Distribution
- First MTP joint (podagra) — 50% of first attacks; pathognomonic
- Ankle, mid-foot (tarsal joints)
- Knee
- Wrist, elbow, finger joints (later disease)
Disease Stages
- Asymptomatic hyperuricaemia
- Acute intermittent gout
- Intercritical gout (symptom-free intervals)
- Chronic tophaceous gout
Diagnosis
Gold Standard
Joint aspiration + polarised light microscopy
- Needle-shaped crystals
- Negatively birefringent
- Yellow when parallel to axis of slow vibration
- Also confirms absence of septic arthritis
Serum Urate
- May be falsely normal during acute attack (acute phase response lowers urate)
- Check 4–6 weeks after attack settles
- Elevated urate ≠ gout diagnosis alone
Imaging
- Dual-energy CT (DECT): urate deposits coded in colour
- Ultrasound: double-contour sign (urate on cartilage)
X-Ray (Late Disease)
- "Punched-out" erosions
- Sclerotic margins
- Overhanging edge (Martel sign)
- Preserved joint space (differentiates from RA)
- Soft tissue tophi with calcification
Tophi
Subcutaneous deposits of MSU crystals. Found on ear helix, finger pads, olecranon bursa, Achilles tendon. Chalky-white discharge if they ulcerate. Indicates chronic disease requiring aggressive ULT.
Exam tip: Serum urate can be NORMAL during an acute gout attack. Do not rule out gout based on a normal urate during the flare.
Critical Rule: Do NOT start allopurinol (or any urate-lowering therapy) during an acute attack — it can prolong or precipitate a new attack. Do NOT stop existing allopurinol if the patient is already on it.
First-Line Analgesia: NSAIDs
First-line if no contraindications
- Naproxen 500 mg BD (twice daily)
- Indomethacin 50 mg TDS (three times daily) — highly effective but more GI/CNS side effects
- Use for 5–7 days or until attack resolves
Contraindications / Cautions
- Renal impairment (AKI risk)
- Cardiac failure / hypertension (fluid retention)
- Active peptic ulcer / GI bleed
- Anticoagulant use
Always co-prescribe a PPI (e.g., omeprazole 20 mg OD) when prescribing NSAIDs for gastroprotection.
Second-Line: Colchicine
- 500 mcg BD–TDS orally
- Anti-inflammatory: inhibits microtubule polymerisation → neutrophil migration inhibition
- Most effective within first 24 hours of attack
Side Effects
- Diarrhoea, nausea, abdominal cramps (most common — dose-dependent)
- Myopathy with prolonged use
- Bone marrow suppression (rare)
Cautions
- Avoid in severe renal impairment (eGFR <10) — reduce dose in moderate CKD
- Avoid with strong CYP3A4/P-gp inhibitors (clarithromycin, ciclosporin)
- Hepatic impairment
Third-Line: Corticosteroids
Use when NSAIDs and colchicine are contraindicated or not tolerated.
Systemic
- Prednisolone 30–40 mg/day for 5 days, then stop (no taper needed for short course)
- Effective and well-tolerated for short-term use
- Monitor blood glucose (hyperglycaemia risk — especially in diabetes)
Intra-articular Injection
- After joint aspiration (therapeutic + diagnostic)
- Triamcinolone injection into large joints (knee, ankle)
- Rapid, localised relief
- Ensure septic arthritis excluded before injecting corticosteroid
Non-Pharmacological Acute Measures
Ice Packs
Apply wrapped ice to affected joint 20–30 min, 3–4 times daily. Reduces inflammation and pain. Do NOT apply ice directly to skin.
Rest & Elevation
Elevate affected limb to reduce oedema. Avoid weight-bearing on affected joint. Use crutches if first MTP / ankle involved.
Hydration
Encourage oral fluids >2 L/day. Promotes renal urate excretion. IV fluids if oral intake impaired or hospitalised.
Summary: Acute Attack Management Algorithm
1
Confirm diagnosis — consider joint aspiration (gold standard, also therapeutic)
2
Assess contraindications to NSAIDs (renal/cardiac/GI) and colchicine (renal)
3
NSAIDs (naproxen 500 mg BD or indomethacin 50 mg TDS) + PPI if no contraindications
4
If NSAID contraindicated → Colchicine 500 mcg BD–TDS (reduce dose in CKD)
5
If both contraindicated → Prednisolone 30–40 mg/day × 5 days or intra-articular steroid
6
Ice, elevation, rest, adequate hydration
7
Do NOT start ULT during attack. Do NOT stop existing allopurinol/febuxostat
8
Plan ULT initiation 2–4 weeks after attack settles (if indicated)
Indications for Urate-Lowering Therapy (ULT)
- ≥2 attacks per year
- Tophi (any site)
- Urate nephropathy / renal urate stones
- Chronic gouty arthritis with joint damage
- First attack with: CKD, urate >480 μmol/L, young patient (<40 years)
- First attack with radiographic damage
ULT is a lifelong commitment. Stopping ULT allows urate to rise and attacks to recur. Counsel patients thoroughly before starting.
Urate Targets
<360 μmol/L
Standard target
(most patients)
(most patients)
<300 μmol/L
Tophaceous gout
(accelerated crystal dissolution)
(accelerated crystal dissolution)
Treat to target: titrate dose monthly until target is achieved. Check serum urate 4–6 weeks after each dose change.
Allopurinol — First-Line XO Inhibitor
Mechanism
Purine analogue that competitively inhibits xanthine oxidase → reduces conversion of xanthine to uric acid → lowers serum urate.
Dosing Protocol
- Start 100 mg/day (50 mg/day in CKD)
- Increase by 100 mg every 4 weeks
- Maximum dose: 900 mg/day
- Titrate to serum urate target
Timing
- Do NOT start during acute attack
- Wait 2–4 weeks after attack settles
- Cover with colchicine prophylaxis when starting (see Tab 4)
Side Effects
- Rash (common) — can be mild or life-threatening
- GI upset
- Elevated liver enzymes
Severe Reactions
Allopurinol Hypersensitivity Syndrome (AHS)
Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)
Strongly associated with HLA-B*58:01 allele
Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)
Strongly associated with HLA-B*58:01 allele
HLA-B*58:01 Screening
- Screen before starting in: Han Chinese, Thai, Korean
- Also relevant: Indian, Sri Lankan, other South/Southeast Asian
- If positive → avoid allopurinol → use febuxostat
Febuxostat — Second-Line XO Inhibitor
Mechanism
Non-purine, non-competitive xanthine oxidase inhibitor — different structure to allopurinol, no cross-reactivity in most cases.
Indications
- Allopurinol intolerance or hypersensitivity
- Inadequate response to maximum tolerated allopurinol
- CKD (some evidence for use)
Dosing
- Start 40 mg/day, increase to 80 mg/day if target not reached
- Maximum 120 mg/day
Cardiovascular Warning
CARES trial (2018): febuxostat associated with increased cardiovascular mortality vs allopurinol (all-cause CV death).
Caution in patients with established cardiovascular disease. Discuss benefit–risk with patient.
Caution in patients with established cardiovascular disease. Discuss benefit–risk with patient.
Side Effects
- Liver function abnormalities — monitor LFTs
- Rash (less severe than allopurinol)
- Nausea, arthralgia
Uricosuric Agents
Increase renal excretion of uric acid by blocking URAT1 transporter in proximal tubule.
| Drug | Indications | Contraindications | Notes |
|---|---|---|---|
| Benzbromarone | Allopurinol-intolerant; effective in mild-mod CKD | Urate nephrolithiasis, severe renal impairment | Hepatotoxicity risk — monitor LFTs; widely used in Asia/Middle East |
| Probenecid | Second-line uricosuric; hyperurate excreters | Urate stones, eGFR <30, uric acid overproducers | Ensure high fluid intake; drug interactions |
Ensure adequate hydration (≥2 L/day) with uricosurics to reduce risk of urate crystal precipitation in renal tubules.
Why Flares Occur When Starting ULT
Starting ULT (especially allopurinol) causes mobilisation of urate deposits from tissues and joints as serum urate falls rapidly. This releases MSU crystals into the joint space, triggering acute flares — often within the first 3–6 months.
Key patient message: "The medication is working — your body is clearing the urate crystals. This is expected. Do NOT stop your allopurinol even if you get an attack."
Flare Prophylaxis Regimens
Colchicine Prophylaxis (Preferred)
- 500 mcg once or twice daily
- Duration: 3–6 months after starting ULT
- Continue until urate target achieved AND no tophi
- Reduce dose in CKD (consider 500 mcg every other day)
Low-Dose NSAID Alternative
- Naproxen 250 mg BD or similar low-dose
- If colchicine not tolerated
- Less preferred due to GI/renal/CV risks
- Use with PPI gastroprotection
Patient Education — Key Points
1
Explain flare risk: Attacks may worsen in the first weeks of ULT — this is normal and does not mean treatment is failing.
2
Never stop allopurinol during an attack — stopping causes urate to rebound and prolongs total disease burden.
3
Diet: Limit red meat, offal, shellfish. Avoid beer. High-fructose drinks elevate urate independently of purines.
4
Hydration: Aim for ≥2 L/day fluid intake. Dehydration is a major precipitant — especially relevant during fasting, hot weather, and exercise.
5
Weight loss: Gradual weight loss reduces urate. Avoid crash diets — rapid weight loss causes ketosis which competes with urate excretion and can precipitate attacks.
6
Medication review: Report all medications — diuretics and low-dose aspirin raise urate. Discuss with prescribing doctor.
7
Lifelong treatment: Allopurinol is a long-term medication. Stopping leads to urate rise and recurrence of attacks and tophi.
Pseudogout (Calcium Pyrophosphate Deposition — CPPD)
Pseudogout is a distinct crystal arthropathy caused by calcium pyrophosphate dihydrate (CPPD) crystals — different from MSU gout. Clinically similar presentation but key differences on microscopy and imaging.
Gout (MSU Crystals)
- Crystal shape: Needle-shaped
- Birefringence: Negatively birefringent
- Colour (parallel): Yellow
- Colour (perpendicular): Blue
- X-ray: Punched-out erosions, tophi
- Joints: 1st MTP, ankle, knee
- Serum urate: Elevated (usually)
- Treatment: NSAIDs/colchicine + allopurinol
Pseudogout (CPPD Crystals)
- Crystal shape: Rhomboid (rectangular)
- Birefringence: Weakly positively birefringent
- Colour (parallel): Blue
- Colour (perpendicular): Yellow
- X-ray: Chondrocalcinosis (calcification of cartilage)
- Joints: Wrist & knee most common
- Serum urate: Normal
- Treatment: NSAIDs/colchicine/aspiration — no specific ULT
CPPD — Clinical Notes
- Associated with: hyperparathyroidism, haemochromatosis, hypothyroidism, hypomagnesaemia — check metabolic screen
- Chondrocalcinosis on X-ray: calcification of menisci (knee), triangular fibrocartilage (wrist)
- Manage acute flare like acute gout: NSAIDs, colchicine, or intra-articular steroids
- No equivalent of ULT for CPPD — no drug to reduce CPP crystal deposition
Urate Monitoring Schedule
| Phase | Timing | Action |
|---|---|---|
| Starting allopurinol | Baseline serum urate, renal function, LFTs, FBC | Establish baseline; check HLA-B*58:01 if appropriate ethnicity |
| Dose titration phase | Serum urate 4–6 weeks after each dose increase | Increase by 100 mg/month until target reached |
| Target achieved | 3-monthly for first year | Confirm sustained target; monitor renal function |
| Stable long-term | Every 6 months | Annual renal function, LFTs; reassess CV risk factors |
Gout in Chronic Kidney Disease (CKD)
CKD is both a cause and consequence of gout. Urate is nephrotoxic. Careful drug selection essential.
Drug Adjustments in CKD
| Drug | CKD Guidance |
|---|---|
| NSAIDs | Avoid — nephrotoxic, worsen CKD |
| Colchicine | Reduce dose: eGFR 10–50 → max 500 mcg BD; eGFR <10 → avoid |
| Prednisolone | Safe — preferred in severe CKD for acute flares |
| Allopurinol | Start 50 mg/day; titrate cautiously (GFR-adjusted). Max dose guided by eGFR |
| Febuxostat | Can use in mild-moderate CKD — no renal dose adjustment needed |
| Uricosurics | Avoid if eGFR <30 — ineffective and risk of tubular precipitation |
Cardiovascular Risk Management
Gout is an independent cardiovascular risk factor. Adequate urate lowering is associated with reduced CV events.
Preferred Antihypertensives in Gout
- Losartan (ARB) — has uricosuric properties; preferred first-line antihypertensive in gout with hypertension
- Amlodipine (CCB) — neutral effect on urate; safe to use
Agents That Worsen Urate
- Thiazide diuretics (bendroflumethiazide, hydrochlorothiazide) — reduce renal urate excretion → worsen hyperuricaemia
- Loop diuretics (furosemide, bumetanide) — similar mechanism
- Low-dose aspirin — blocks tubular urate secretion
If diuretics essential (e.g., heart failure), optimise ULT to compensate. Do NOT withhold diuretics for heart failure management.
Chronic Tophaceous Gout — Advanced Management
Tophi indicate sustained hyperuricaemia with large urate burden. Require aggressive ULT with target <300 μmol/L.
Rasburicase
- Recombinant uricase enzyme (converts uric acid → allantoin, which is more soluble)
- Rapid and marked urate reduction
- Used for: tumour lysis syndrome, rapid tophus reduction
- IV administration, short course
- Contraindicated in G6PD deficiency (haemolysis risk)
Pegloticase
- Pegylated recombinant uricase
- For refractory chronic tophaceous gout
- IV infusion every 2 weeks
- Dramatic urate reduction and tophus regression
- Risk: infusion reactions, immunogenicity (anti-drug antibodies)
- Monitor urate: if rising >360 → may indicate antibody formation → stop
Tophi on ears, finger pads, olecranon, Achilles tendon — document size and number. Regression of tophi is a therapeutic goal and marker of ULT success.
Gout in the GCC — Epidemiology & Risk Factors
Gout is highly prevalent in the Gulf Cooperation Council region due to a convergence of dietary, metabolic, and genetic factors.
Dietary Triggers — GCC Context
- High purine meats: lamb, camel, beef, offal (liver, kidney, sweetbreads)
- Seafood & shellfish: widely consumed in coastal GCC populations
- Fructose drinks: high per capita consumption of sugar-sweetened beverages
- Traditional feasts (Eid, weddings) can precipitate acute attacks
Metabolic Factors
- Metabolic syndrome epidemic: obesity, T2DM, hypertension, dyslipidaemia
- High prevalence of CKD (diabetic nephropathy)
- Widespread use of thiazide diuretics for hypertension
Ramadan Considerations
Ramadan dehydration is a significant trigger for gout attacks in GCC. Reduced fluid intake during daylight hours + hot climate = concentrated urine + rising serum urate.
- Advise increased fluid intake during non-fasting hours (iftar to suhoor)
- Pre-Ramadan ULT optimisation
- Consider if colchicine prophylaxis should be adjusted during Ramadan
Alcohol
- Alcohol is restricted in GCC — beer-triggered gout less common than in Western populations
- Fructose and dehydration are the dominant triggers in GCC
HLA-B*58:01 & Allopurinol — GCC Nursing Relevance
The HLA-B*58:01 allele strongly predicts risk of severe allopurinol hypersensitivity reactions including Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN).
High-Risk Populations in GCC
- South Asian expats: Indian, Sri Lankan, Pakistani, Bangladeshi — large population in UAE, Qatar, Kuwait, Saudi Arabia, Oman, Bahrain
- Southeast Asian expats: Thai, Filipino, Vietnamese
- Han Chinese, Korean populations
Nursing action: Before initiating allopurinol, identify patient ethnicity. For South/Southeast Asian patients, advocate for HLA-B*58:01 screening or discuss alternative ULT (febuxostat) with the prescriber.
SJS/TEN Red Flags
- Widespread blistering skin rash
- Mucous membrane involvement (mouth, eyes, genitalia)
- Fever + skin pain/tenderness
- STOP allopurinol immediately and escalate urgently
DHA / DOH / SCFHS Exam Prep — High-Yield Points
Q
Urate target for standard gout?
<360 μmol/L. For tophaceous gout: <300 μmol/L.
<360 μmol/L. For tophaceous gout: <300 μmol/L.
Q
When to start allopurinol after acute attack?
Wait 2–4 weeks after the attack has fully settled. Never start during an acute attack.
Wait 2–4 weeks after the attack has fully settled. Never start during an acute attack.
Q
Patient on allopurinol gets an acute attack — what do you do?
Continue allopurinol (do NOT stop). Treat the attack with NSAIDs/colchicine/steroids.
Continue allopurinol (do NOT stop). Treat the attack with NSAIDs/colchicine/steroids.
Q
Colchicine dose in acute gout?
500 mcg BD–TDS. Reduce in CKD. Avoid in severe renal impairment.
500 mcg BD–TDS. Reduce in CKD. Avoid in severe renal impairment.
Q
How to differentiate gout from pseudogout on microscopy?
Gout: negatively birefringent needle-shaped crystals.
Pseudogout: weakly positively birefringent rhomboid crystals.
Gout: negatively birefringent needle-shaped crystals.
Pseudogout: weakly positively birefringent rhomboid crystals.
Q
Gold standard diagnosis of gout?
Joint aspiration with polarised light microscopy showing negatively birefringent needle-shaped MSU crystals.
Joint aspiration with polarised light microscopy showing negatively birefringent needle-shaped MSU crystals.
Q
Preferred antihypertensive in a gout patient with hypertension?
Losartan (has uricosuric properties). Avoid thiazide diuretics.
Losartan (has uricosuric properties). Avoid thiazide diuretics.
Q
Why give prophylaxis when starting ULT?
ULT mobilises urate deposits, triggering acute flares. Colchicine 500 mcg OD–BD × 3–6 months prevents these.
ULT mobilises urate deposits, triggering acute flares. Colchicine 500 mcg OD–BD × 3–6 months prevents these.
Genetic & Population Factors in GCC
- Arab Gulf nationals may have genetic susceptibility to hyperuricaemia and gout
- South Asian expat population (the largest demographic group in many GCC states) at risk for HLA-B*58:01-associated allopurinol reactions
- Metabolic syndrome genetics interact with dietary triggers in GCC populations
- Awareness of cultural dietary habits is essential for personalised gout counselling
Key Nursing Responsibilities in GCC Gout Care
- Screen for HLA-B*58:01 before allopurinol in at-risk ethnicities
- Educate patients about Ramadan hydration strategies
- Counsel on GCC-specific dietary purine sources (lamb, offal, camel)
- Review antihypertensive drugs — change thiazides to losartan where possible
- Monitor urate at each dose titration
- Reassure patients that flares during early ULT are expected
- Document and monitor tophi regression
- Address metabolic syndrome comprehensively (BP, lipids, glucose, weight)
Gout Attack vs Septic Arthritis Differentiator
Clinical Decision Support Tool — Enter findings to get differential diagnosis guidance
Red Flags for Septic Arthritis
Immediate Management Recommendation
Aspiration Guidance