Kidney Stones (Urolithiasis)
NICE guideline [NG118] Renal and ureteric stones: assessment and management. Published: Jan 2019.
NICE CKS Renal or ureteric colic – acute. Last revised: Oct 2024.
Background information added accordingly.
Date: 15/12/25
Background Information
Definition
Urolithiasis: formation of stones in any part of the urinary tract:
- Kidney – most prevalent form
- Ureter – most frequent cause of symptomatic stone disease (renal colic)
- Bladder – uncommon
Anatomy
There are 3 physiological narrowings of the ureter, where stones most commonly obstruct:
- Ureteropelvic junction (UPJ) – between the renal pelvis and ureter
- Pelvic brim – where the ureter crosses over the iliac vessels
- Ureterovesical junction (UVJ) – entry point into the bladder
The ureterovesical junction (UVJ) is the narrowest, thus the most common site for stone impaction.
Aetiology
General risk factors for stone formation:
- Low fluid intake → chronic dehydration
- Dietary factors (excess dietary intake of sodium / oxalate / urate / animal protein)
- 40-50 y/o = peak incidence
- Male > females
- White > Hispanic > black > Asian
Certain medical conditions increase the risk of stone formation
- Urinary tract anatomical abnormalities (e.g. horseshoe kidney, ureteral stricture, vesico-uretero-renal reflux, medullary sponge kidney)
- Enteric hyperoxaluria causes
- Crohn’s disease (ileal involvement / ileal resection) – classic association
- Short bowel syndrome
- Post-bariatric surgery (esp. Roux-en-Y gastric bypass)
- Chronic pancreatitis / pancreatic exocrine insufficiency
- Conditions that alter urinary pH
Drugs that increase the risk of stone formation:
- Loop diuretics
- Carbonic anhydrase inhibitors (→ alkaline urine → favours calcium phosphate precipitation)
- Orlistat (→ fat malabsorption → enteric hyperoxaluria)
- Allopurinol (→ xanthine stones) (rare but classic)
Also see the section on kidney stone composition overview for type-specific risk factors
Kidney Stone Composition Overview
Calcium stones make up ~80% of kidney stones (80%: calcium oxalate, 20%: calcium phosphate)
| Stone type | Visibility on X-ray | Typical urine pH | Key causes / associations |
|---|---|---|---|
| Calcium oxalate (most common) | Radiopaque | Acidic |
|
| Calcium phosphate (2nd most common) | Radiopaque | Alkaline |
|
| Uric acid (~10%) | Radiolucent | Acidic |
|
| Struvite (magnesium ammonium phosphate) (1-5%) | Radiopaque | Alkaline |
|
| Cystine (~1%) | Faintly radiopaque | Acidic |
|
| Xanthine | Radiolucent | Variable (often acidic) |
|
Learning aid:
- Visibility on X-ray (NB that plain X-rays are NOT the investigation of choice for diagnosing kidney stones, but are often featured in exams)
- Most stones are radiopaque (white on X-ray)
- Except for uric acid stones (and less commonly: xanthine stones), which are radiolucent (invisible on X-ray)
- “Uric acid” = “radiolUcent”
- Urine pH
- Most kidney stones are precipitated by acidic urine pH
- Except for calcium phosphate and struvite stones, which are precipitated by alkaline urine pH
Complications
Acute complications mainly arise from urinary flow obstruction:
- Infection of the obstructed renal unit → obstructive pyelonephritis → sepsis
- Acute kidney injury
- Hydronephrosis / pyonephrosis
Diagnosis
Clinical Features
Urinary stones are often asymptomatic but may cause pain when they move or obstruct urine flow through the ureter
| Stone location | Features |
|---|---|
| Kidney (renal) |
Renal stones often do not cause the classic renal colic |
| Ureteric | Stones in the ureter most commonly cause symptomatic stone disease
Classic presentation: renal colic
Patient may also experience dysuria, urinary frequency, and urgency (due to the stone irritating the detrusor muscle when it reaches the ureterovesical junction)
Patients with renal colic are typically restless and unable to lie still (due to the severe pain)
|
| Bladder | Bladder stones typically present as:
Bladder stones can cause acute urinary retention |
Ureteric obstruction activates visceral afferent fibres travelling with T10–L2 sympathetic nerves.
This causes the pain to radiate to the flank, lower abdomen, groin, or even testicle / labia (loin-to-groin)
Investigation and Diagnosis
Initial Tests
The following tests are adjuncts to definitive diagnostic investigations (see below) and are commonly performed as initial bedside tests to support clinical suspicion and help exclude important differential diagnoses:
| Pregnancy test | A urinary pregnancy test should be performed in ALL women of childbearing potential who present with abdominal/pelvic pain to exclude ectopic pregnancy |
| Urinalysis | Interpretation:
|
Diagnostic Tests
Choice of diagnostic imaging:
- Adults → low-dose non-contrast CT KUB (within 24 hours of presentation)
- Children and young people / pregnant women → ultrasound KUB
Imaging findings
| Imaging modality | Findings indicative of renal / ureteric stone |
|---|---|
| CT KUB | Gold standard test
|
| US KUB |
NB that ultrasound may miss tiny stones |
Management
Acute Management
Initial Management – Analgesia
Choice of analgesia:
- 1st line: NSAID by any route
- 2nd line: IV paracetamol
- 3rd line: opioids
Although not explicitly mentioned in the guidelines, PR / IM diclofenac is most commonly used in practice due to its rapid onset and good efficacy for severe renal colic pain.
Oral NSAIDs are typically reserved for those with less severe pain and who can tolerate oral medications.
Do not offer antispasmodics to adults, children and young people with suspected renal colic.
Definitive Management
If urolithiasis is associated with signs of infection (e.g. fever) → offer IV antibiotics + urgent renal decompression with: [Ref1][Ref2]
- Percutaneous nephrostomy, OR
- Ureteric stent (preferred: retrograde stent, alternative: anterograde stent)
Urgent renal decompression is also indicated in the following scenarios (apart from infection): [Ref]
- AKI due to obstruction
- High-grade obstruction in a solitary / transplanted kidney
If urgent renal decompression is not indicated, see below for the choice of definitive management.
Ureteric Stones
| Stone property | Management |
|---|---|
| <10 mm |
Also consider alpha blockers if the stone is distal (and <10 mm) as an adjunct to shockwave lithotripsy |
| 10-20 mm |
Only consider percutaneous nephrolithotomy if there are proximal stones and ureteroscopy has failed |
Shockwave lithotripsy is contraindicated in pregnancy
NICE do not recommend watchful waiting for ureteric stones (even if <5mm), because of:
- Higher risk of obstruction and complications like hydronephrosis and infection
- More severe renal colic
- Lower spontaneous passage rate
Renal Stones
| Stone property | Management |
|---|---|
| Asymptomatic + <5mm |
|
| 5-10 mm |
|
| 10-20 mm |
|
| >20 mm and staghorn stones |
|
Shockwave lithotripsy is contraindicated in pregnancy
Long Term Management (Secondary Prevention)
Metabolic Investigations
- Measure serum calcium (to identify primary hyperparathyroidism)
- Consider stone analysis in adults (to identify treatable conditions like cystinuria, uric acid stones and primary hyperparathyroidism)
Conservative / General Management
Advise the following:
- Drink sufficient water (2.5-3 L for adults, and 1-2L for children and young people)
- Add fresh lemon juice to drinking water
- Avoid carbonated drinks
- Restrict daily salt intake (<6g in adults, 2-6g in children and young people)
- Do not routinely restrict calcium intake (one should maintain normal calcium intake)
Note that excess vitamin C intake, especially from supplements is associated with increased risk of kidney stones, due to increased urinary oxalate from ascorbic acid metabolism.
Lemon juice is recommended for renal stone prevention because they are rich in citrate, which inhibits calcium stone formation by increasing urinary citrate and alkalinising urine. The vitamin C content in lemon juice is substantially lower than its citrate content, therefore would not have a negative impact.
Pharmacological Management
Consider the following if there is recurrent stone disease that is made up of >50% calcium oxalate:
- Potassium citrate
- Thiazide diuretic (after restricting their sodium intake to <6g / day)