Kidney Stones: Causes, Symptoms and Treatment

Kidney stones (urolithiasis or nephrolithiasis) are hard mineral and salt crystals that form within the urinary tract — the kidneys, ureters, bladder, or urethra. They affect approximately 10% of adults in developed countries over a lifetime, with recurrence rates of 50% within 5–10 years without preventive treatment. Kidney stones cause some of the most intense pain in medicine — renal colic from a stone passing through the ureter is frequently described as worse than labour.

Beyond the immediate episode, recurrent stone formers are at increased risk of chronic kidney disease, hypertension, and cardiovascular disease. However, the majority of stones are preventable with appropriate dietary and pharmacological measures.

How Kidney Stones Form

Urinary stones form when the concentration of stone-forming substances in the urine exceeds their solubility threshold — a process called supersaturation. Crystal nucleation begins, and if supersaturation persists and inhibitors of crystal growth (citrate, magnesium, Tamm-Horsfall protein) are insufficient, crystals aggregate into stones.

Key factors promoting stone formation:

• Low urine volume — dehydration concentrates all urinary solutes
• High urinary excretion of stone-forming ions (calcium, oxalate, uric acid, cystine)
• Low urinary citrate (citrate inhibits calcium crystal growth)
• Abnormal urinary pH (acidic urine promotes uric acid stones; alkaline urine promotes calcium phosphate and struvite stones)
• Anatomical abnormalities — stasis in horseshoe kidney, medullary sponge kidney, ureteropelvic junction obstruction

Stone Types

Calcium Oxalate (Most Common — 75–80%)

Calcium oxalate monohydrate (COM) or dihydrate (COD) stones are the most common. Calcium oxalate supersaturation depends on urinary calcium and oxalate concentrations. Risk factors:

• Hypercalciuria — the most common metabolic abnormality in stone formers: absorptive (excessive calcium absorption from gut), renal leak (kidney fails to reabsorb filtered calcium), or resorptive (hyperparathyroidism driving bone calcium release)
• Hyperoxaluria — primary (rare genetic enzyme deficiency), enteric (fat malabsorption in IBD/short bowel → increased colonic oxalate absorption → hyperoxaluria), or dietary (excessive spinach, nuts, rhubarb, chocolate)
• Hypocitraturia — reduced citrate (renal tubular acidosis, hypokalemia, high-meat diet)

Calcium Phosphate (5–10%)

Associated with renal tubular acidosis (alkaline urine promotes calcium phosphate precipitation), hyperparathyroidism, and distal tubular defects.

Uric Acid (5–10%)

Formed in persistently acidic urine (pH <5.5) with hyperuricosuria. Associated with:

• Gout and hyperuricaemia
• High purine diet (red meat, shellfish, organ meats)
• Type 2 diabetes and metabolic syndrome (insulin resistance causes impaired ammonium excretion → acidic urine)
• Chronic diarrhoea (stool bicarbonate loss → acidic urine)

Uric acid stones are radiolucent — invisible on plain X-ray but visible on CT. Importantly, they can dissolve completely with urinary alkalinisation (potassium citrate tablets to raise urine pH to 6.5–7.0) — medical dissolution is possible without surgery.

Struvite (Infection Stones — 5–10%)

Composed of magnesium ammonium phosphate; form only in the presence of urease-producing bacteria (Proteus, Klebsiella, Pseudomonas) that hydrolyse urea to produce ammonia, alkalinising urine. Form rapidly, often growing to fill the renal collecting system (staghorn calculi). Associated with recurrent UTIs; treatment requires both stone removal and antibiotic sterilisation.

Cystine (1%)

Rare genetic disorder (cystinuria) causing excessive cystine excretion; forms highly recurrent stones; requires urinary alkalinisation and high fluid intake; often requires specialist management.

Symptoms

Renal Colic

The classic presentation when a stone enters the ureter:

• Severe flank pain — sudden onset colicky (comes in waves) pain in the loin (between ribs and hip); may radiate to the groin, inner thigh, or genitalia as the stone descends
• Nausea and vomiting — severe, accompanying the pain
• Haematuria — blood in urine (macroscopic — visible; or microscopic); present in approximately 80–90% of ureteric stones
• Restlessness — patients cannot find a comfortable position (contrasts with peritonitis where the patient lies still)
• Dysuria and frequency — when the stone reaches the vesicoureteric junction (VUJ — junction of ureter and bladder)

Pain severity depends on degree of ureteric obstruction and rate of onset — a small stone causing complete acute obstruction may be more painful than a large stone with partial obstruction.

Large kidney stones within the renal pelvis may be asymptomatic ("silent stones") until they pass into the ureter.

Complications

• Obstructive uropathy — complete ureteric obstruction causes hydronephrosis (dilation of the kidney) and, if prolonged, irreversible kidney damage
• Infection + obstruction — infected hydronephrosis (pyonephrosis) is a urological emergency requiring urgent decompression (ureteric stent or nephrostomy) and IV antibiotics; can rapidly progress to urosepsis
• Chronic kidney disease — recurrent obstruction or bilateral disease

Diagnosis

CT Urography (Non-contrast CT KUB)

The gold standard and first-line investigation for suspected renal colic. Non-contrast CT detects virtually all stone types (calcium, uric acid, cystine, struvite) regardless of composition, precisely localises the stone, measures stone size and density, and identifies complications (hydronephrosis, perirenal stranding).

Stone size on CT is the most important predictor of spontaneous passage:

• ≤4 mm: 80% pass spontaneously
• 5–6 mm: 50–60% pass spontaneously
• ≥7 mm: unlikely to pass without intervention
• ≥10 mm: require active stone treatment

Ultrasound

Can detect renal stones and hydronephrosis; radiation-free; preferred in pregnancy and children; less sensitive for small ureteric stones.

Plain Abdominal X-ray (KUB)

Detects calcium-containing (radio-opaque) stones ≥3 mm; misses uric acid and cystine stones; useful for follow-up of known radio-opaque stones.

Metabolic Stone Work-up

After the first recurrent stone or high-risk first stone (young patient, bilateral, large, or metabolic disease):

• 24-hour urine collection: calcium, oxalate, uric acid, citrate, creatinine, sodium, magnesium, phosphate, pH
• Serum: calcium, phosphate, urate, bicarbonate, creatinine, PTH (if hypercalcaemia)
• Stone analysis: if the stone is retrieved, chemical composition guides prevention

Treatment

Acute Management — Pain Relief

• NSAIDs (diclofenac, ketorolac IM/IV) — first-line analgesics; reduce prostaglandin-mediated ureteric spasm and oedema; superior analgesia to opioids for renal colic
• Opioids (morphine, pethidine) — for NSAID-contraindicated patients; IV in severe colic
• Antispasmodics (hyoscine) — reduce ureteric spasm
• IV fluids — for vomiting and dehydration; not shown to accelerate stone passage
• Alpha-blockers (tamsulosin) — relax ureteric smooth muscle (particularly at VUJ); recommended to facilitate passage of stones 5–10 mm; increases spontaneous passage rate by approximately 20%

Expectant Management (Watchful Waiting)

For small ureteric stones (≤6 mm) without fever, urinary infection, or solitary kidney — 4-week trial of conservative management with analgesia, alpha-blocker, and high fluid intake (target urine output >2 litres/day). Most ≤4 mm stones pass within 2–4 weeks.

Shock Wave Lithotripsy (SWL / ESWL)

Non-invasive: focused acoustic shock waves generated externally, targeted at the stone under fluoroscopic or ultrasound guidance; fragment the stone into small pieces that pass spontaneously.

• Effective for stones ≤2 cm in the kidney or upper ureter
• Day-case procedure; conscious sedation or analgesia
• 70–80% stone-free rate at 3 months for 1–2 cm renal stones
• Requires radio-opaque stone, good renal function, no obstruction distal to stone, no coagulopathy
• Contraindicated in pregnancy; less effective for hard stones (calcium oxalate monohydrate, cystine)

Ureteroscopy + Laser Lithotripsy (URS)

A thin flexible or semi-rigid ureteroscope is passed through the urethra → bladder → ureter to the stone. A holmium laser (or thulium fibre laser — most modern) fibre is passed through the scope and fragments the stone, with fragments retrieved or left to pass. The gold standard for ureteric stones and increasingly for renal stones <2 cm.

• 90% stone-free rate for ureteric stones; 80–90% for renal stones <2 cm

• Day-case or overnight procedure; general or spinal anaesthetic
• A ureteric stent may be placed for 1–2 weeks post-procedure to prevent ureteric oedema obstruction

Percutaneous Nephrolithotomy (PCNL)

For large renal stones (≥2 cm), staghorn calculi, or stones not suitable for URS/SWL. A percutaneous tract is created through the back into the kidney collecting system under fluoroscopic/ultrasound guidance; a nephroscope is passed and the stone is fragmented and removed.

• Most effective treatment for large/complex renal stones; single-stage stone clearance
• Minimally invasive PCNL (mini/ultra-mini PCNL) uses smaller tracts with equivalent efficacy and less bleeding
• 85–95% stone-free rate for large stones

Medical Stone Dissolution

Uric acid stones: urinary alkalinisation with potassium citrate (target urine pH 6.5–7.0); complete dissolution over weeks to months; can avoid surgical intervention entirely.

Cystine stones: high fluid intake + alkalinisation + D-penicillamine or tiopronin to reduce cystine excretion.

Prevention

Dietary and pharmacological measures dramatically reduce recurrence:

For all stone types:

• High fluid intake — target urine output >2.5 litres/day; the single most important preventive measure; reduces recurrence by approximately 50%
• Dietary sodium restriction (<5 g NaCl/day) — excess sodium increases urinary calcium excretion
• Normal dietary calcium intake — paradoxically, low-calcium diets increase oxalate absorption; adequate calcium (1000–1200 mg/day from diet) binds gut oxalate

For calcium oxalate stones:

• Thiazide diuretics (hydrochlorothiazide, chlorthalidone) — reduce urinary calcium excretion; prescribed for hypercalciuria
• Potassium citrate — for hypocitraturia; increases citrate (crystal inhibitor) and alkalinises urine
• Reduce high-oxalate foods (spinach, rhubarb, nuts, chocolate) only if hyperoxaluria confirmed

For uric acid stones:

• Urinary alkalinisation (potassium citrate)
• Allopurinol — reduces uric acid production; for hyperuricosuria or recurrent uric acid stones

Urology and Kidney Stone Care in China

China's urology centres offer:

• Assessment and imaging: CT urography, renal ultrasound, urine analysis, and metabolic work-up
• Holmium and thulium laser ureteroscopy: flexible URS with modern laser platforms; high stone-free rates; day-case surgery
• Mini-PCNL: minimally invasive percutaneous surgery for large stones; experienced teams performing hundreds of procedures annually
• ESWL (shock wave lithotripsy): outpatient session
• 24-hour urine metabolic profiling: comprehensive prevention analysis
• Cost: care in China is generally less expensive than UK private treatment, but the hospital prices each case individually — ask us for the written quote before you commit.
• Full English care navigation from diagnosis through treatment and prevention planning

Contact a ChinaMedicalTour care navigator to arrange a kidney stone assessment, imaging, or surgical treatment.

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Medical content based on MSD Manuals and international urolithiasis guidelines (EAU, AUA). Evidence reviewed 2025.

Frequently Asked Questions

What imaging is reviewed to evaluate kidney stones before scheduling treatment?

Non-contrast helical CT scans of the urinary tract (KUB CT) and renal ultrasound reports are reviewed by urologists to evaluate stone size, location, density (Hounsfield units), and hydronephrosis.

What minimally invasive kidney stone procedures are performed in China?

Chinese tertiary urology centers evaluate flexible ureteroscopy with holmium laser lithotripsy (RIRS), mini-percutaneous nephrolithotomy (mini-PCNL), and extracorporeal shock wave lithotripsy (ESWL).

How is kidney stone day surgery or inpatient care arranged for visitors?

Depending on stone complexity and surgical approach, treatment is scheduled as day surgery or a short hospital stay, with clear hospital fee quotations confirmed in advance.