Condition Deep-Dives 10 min read·Updated 22 July 2026 Clinician-reviewed

Cystinuria

A UK Consultant Nephrologist on cystinuria — an inherited tubular transporter defect causing recurrent, often disabling, kidney stones from childhood. The right early diagnosis and a hydration + alkalinisation + thiol-drug regimen preserves kidney function for life.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

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Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

Cystinuria is autosomal recessive (SLC3A1, SLC7A9). Hexagonal urinary crystals are pathognomonic. Treatment: high fluids (>3 L/day, including overnight), potassium citrate to urine pH 7.0–7.5, low-sodium diet, and tiopronin if needed. Long-term joint nephrology–urology care prevents CKD.

Key recommendation: Autosomal recessive; SLC3A1 / SLC7A9 (NHS R256 panel).

Quick answer

✓ Best choices

  • 2.5–3 L of fluid a day (mostly water), spread across the day
  • Normal dietary calcium with meals (≈ 1000 mg/day) — it binds oxalate in the gut
  • Lemon water and citrus fruit for natural citrate
  • Vegetables, fruit and whole grains (DASH-style)

✓ Foods to limit

  • Added salt and salty processed foods
  • Very high-oxalate foods if you are an oxalate-stone former: spinach, rhubarb, beetroot, almonds, dark chocolate
  • Sugary drinks and excessive animal protein

Key takeaway

Cystinuria is autosomal recessive (SLC3A1, SLC7A9). Hexagonal urinary crystals are pathognomonic. Treatment: high fluids (>3 L/day, including overnight), potassium citrate to urine pH 7.0–7.5, low-sodium diet, and tiopronin if needed. Long-term joint nephrology–urology care prevents CKD.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Cystinuria

Genetics & diagnosis

INHERITANCE: autosomal recessive. SLC3A1 (rBAT) → type A. SLC7A9 (b⁰,⁺AT) → type B. Compound type AB exists. Heterozygotes are usually asymptomatic but may have modest hyperexcretion.

Presentation

  • Recurrent renal colic from childhood / young adulthood
  • Often bilateral, often staghorn
  • Family history common
  • Most patients have > 5 stone events by age 30 if untreated

Diagnostic Tests

  • Hexagonal cystine crystals on first-morning urine microscopy (pathognomonic)
  • 24-h urinary cystine > 400 mg/day (homozygotes typically > 600)
  • Stone composition analysis (FTIR) — cystine
  • Urine cyanide-nitroprusside test (qualitative; rarely used now)
  • NHS National Genomic Test Directory R256 (cystinuria panel)
  • Imaging: low-dose CT KUB; cystine stones are MODERATELY radio-opaque (less than calcium) but visible on CT

KEY DIFFERENTIAL: any recurrent stone disease in childhood/young adulthood — also consider primary hyperoxaluria, distal RTA, Dent disease, hypercalciuria.

Conservative management

1. HYDRATION (the most important intervention):

  • > 3 L/day in adults; weight-adjusted in children
  • Target urine output > 3 L/24h
  • Include overnight intake — patients should drink 500 mL before bed and set an alarm to drink overnight (cystine solubility falls when urine is concentrated for hours)
  • Carry water bottles, set hourly reminders
  • Aim urinary cystine concentration < 250 mg/L (the saturation point in alkaline urine)

2. Urinary Alkalinisation

  • Potassium citrate 30–60 mEq/day in divided doses
  • Target urine pH 7.0–7.5 (cystine solubility rises 3–4× above pH 7)
  • Patients should self-monitor with urine dipstick pH twice daily
  • Sodium bicarbonate is an alternative but adds sodium (raises cystinuria) — citrate preferred
  • Acetazolamide rarely used (raises urine pH but causes acidosis)

3. Dietary

  • Low sodium (< 2 g/day Na, < 5 g salt) — sodium drives cystinuria
  • Moderate protein (avoid high methionine — egg, chicken, fish, dairy if excessive)
  • Adequate fluid throughout day
  • Limit cranberry juice (acidifies urine)

4. Avoid

  • Vitamin C megadoses
  • Loop diuretics (concentrate urine)
  • Dehydration (alcohol, exercise without rehydration)

Pharmacological & surgical care

THIOL DRUGS (when conservative fails — typically 24h cystine still > 250 mg/L):

  • TIOPRONIN (Thiola) 250–500 mg tds — UK first-line; better tolerated than D-penicillamine
  • D-PENICILLAMINE 0.5–2 g/day — older; nephrotic syndrome, marrow suppression, taste loss limit use
  • Both bind cystine to form soluble cysteine-drug disulphides
  • Add pyridoxine (B6) 25–50 mg/day to prevent neuropathy
  • Monitor: FBC, U&E, urine protein every 3 months (membranous nephropathy is a recognised complication of penicillamine)

Surgical

  • Standard urology — flexible ureteroscopy and laser preferred (cystine stones are HARD and respond poorly to shockwave lithotripsy)
  • PCNL for large or staghorn stones
  • Repeated PCNL is the main driver of long-term CKD — minimise where possible
  • Specialist UK stone centres offer percutaneous chemolysis with tromethamine-E (THAM-E) irrigation for residual fragments

Monitoring

  • Quarterly: clinic review, urine pH diary, 24h urine cystine
  • Annual: low-dose CT KUB, U&E, eGFR, ACR, BP
  • Lifelong joint nephrology–urology care

Pregnancy

  • Stone risk rises; alkalinisation safe (potassium citrate compatible)
  • Tiopronin / penicillamine — specialist decision (penicillamine fetal risk)
  • Increase hydration even further; serial USS to monitor for hydronephrosis

Family

  • Sibling testing; cascade through R256
  • Genetic counselling for couples both carrying SLC variants

Prognosis

  • Well-managed cystinuria is compatible with normal life expectancy and preserved eGFR
  • Poorly adherent patients may reach ESKD by middle age, typically driven by repeated stone surgery
  • Transplant outcomes are good — cystinuria does not recur in the graft (the donor kidney does not carry the defect, and the bladder/intestinal defect is irrelevant)
Kidney Stones — Deep Dive
Related reading: Kidney Stones — Deep Dive.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Aim for pale-straw urine throughout the day
  • Don't take calcium supplements between meals — take them with food
  • Ask for a stone analysis so your diet can be matched to the stone type

Clinical guidance

TL;DR summary

Cystinuria is autosomal recessive (SLC3A1, SLC7A9). Hexagonal urinary crystals are pathognomonic. Treatment: high fluids (>3 L/day, including overnight), potassium citrate to urine pH 7.0–7.5, low-sodium diet, and tiopronin if needed. Long-term joint nephrology–urology care prevents CKD.

Key takeaways
  • Autosomal recessive; SLC3A1 / SLC7A9 (NHS R256 panel).
  • Hexagonal crystals on urine microscopy = pathognomonic.
  • Hydration + citrate to urine pH 7.0–7.5 is the foundation.
  • Tiopronin > D-penicillamine for tolerability.
  • CKD risk comes from repeated stone surgery — minimise it.
Kidney Diet & Nutrition Considerations for Stones

For calcium-oxalate stones — the most common type in the UK — three dietary levers matter most: drink enough fluid, keep dietary calcium normal (don't cut it), and moderate oxalate, salt and animal protein. Citrate from citrus fruit and lemon water is genuinely protective. The DASH pattern halves stone recurrence in trials.

Foods to prioritise

  • 2.5–3 L of fluid a day (mostly water), spread across the day
  • Normal dietary calcium with meals (≈ 1000 mg/day) — it binds oxalate in the gut
  • Lemon water and citrus fruit for natural citrate
  • Vegetables, fruit and whole grains (DASH-style)

Foods to limit

  • Added salt and salty processed foods
  • Very high-oxalate foods if you are an oxalate-stone former: spinach, rhubarb, beetroot, almonds, dark chocolate
  • Sugary drinks and excessive animal protein

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What causes cystinuria?

Cystinuria is an autosomal recessive defect in the proximal tubular and intestinal dibasic amino-acid transporter, encoded by SLC3A1 (type A) or SLC7A9 (type B). Cystine is poorly soluble in acidic urine and crystallises into recurrent, often staghorn, kidney stones from childhood.

How is it diagnosed?

Suspect in any child or young adult with recurrent stones, a family history, or pathognomonic hexagonal cystine crystals on urine microscopy. Confirm with a 24-hour urinary cystine excretion > 400 mg/day (normal < 30) and stone composition analysis. The NHS National Genomic Test Directory R256 confirms SLC3A1 / SLC7A9 variants.

What is the cornerstone of treatment?

Three pillars: (1) very high fluid intake (>3 L/day, including overnight) to keep urinary cystine concentration < 250 mg/L; (2) urinary alkalinisation with potassium citrate to target a urine pH of 7.0–7.5 (cystine solubility rises sharply above pH 7); (3) low-sodium, moderate-protein diet. Thiol-binding drugs (tiopronin, D-penicillamine) are added when conservative measures fail.

What is the long-term outlook?

With good adherence, recurrent stone events can be reduced from yearly to once every several years, and major CKD is preventable. Repeated stone surgery is the main driver of long-term CKD — about 5–10% reach advanced CKD. Lifelong joint nephrology + urology + stone-clinic care is standard UK practice.

What foods help prevent kidney stones?

Plenty of fluid (2.5–3 L/day), a DASH-style diet with normal dietary calcium taken with meals, citrate sources such as lemon water and citrus fruit, and reduced salt and animal protein are the most evidence-based dietary steps for preventing calcium-oxalate kidney stones.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK guidance

Aligned with British Association of Urological Surgeons (BAUS) stone pathways, NHS National Genomic Test Directory R256, and UK Kidney Association rare disease guidance.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Joint nephrology + urology care

Practical hydration regimens, pH targets, thiol-drug selection and surgical decision-making for lifelong stone prevention.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

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Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

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View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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