Phys · renal
Nephrolithiasis
Also known as kidney stones · renal calculi · ureteric colic · renal colic · urolithiasis · calcium oxalate stone · struvite stone · infection stone · staghorn calculus · uric acid stone · cystine stone · brushite stone · nephrocalcinosis · enteric hyperoxaluria · cystinuria
Consultant-physician-depth guide to nephrolithiasis — stone types (calcium oxalate, calcium phosphate, uric acid, struvite, cystine), epidemiology, risk factors, pathophysiology (Randall plaque, supersaturation), clinical presentation of renal colic, investigation strategy (non-contrast CT KUB, ultrasound, metabolic evaluation), acute management (NSAIDs, medical expulsive therapy, ESWL, ureteroscopy, PCNL), prevention (fluid, diet, thiazides, citrate, allopurinol), and systemic associations. Structured for FRACP DWE and DCE, MRCP, and ABIM preparation.
On this page
Study tools
Your progress
Saved on this device.
Practise this topic
Target exams
Red flags
- Obstructive pyelonephritis — fever and rigors with an obstructing stone, a urological emergency requiring urgent decompression
- Bilateral ureteric obstruction or obstruction of a solitary kidney causing AKI
- Haemodynamic instability or septic shock from an infected obstructed system
- Suspected abdominal aortic aneurysm in the older patient presenting with flank pain
- Intractable pain or vomiting despite maximal analgesia
- Stone above 10 mm — unlikely to pass spontaneously, requires intervention
- Anuria from bilateral obstruction — emergency decompression required
Nephrolithiasis
The answer first
Nephrolithiasis (kidney stones) is a common condition with a lifetime risk of approximately 10 per cent, a male-to-female ratio of 2:1, and a recurrence rate of about 50 per cent at 10 years without preventive measures [7]. Stone formation occurs when urinary solutes — calcium, oxalate, uric acid, cystine, or struvite — exceed their solubility product (supersaturation), leading to crystal nucleation, growth and retention [1].
The five major stone types and their key features: [1]
| Stone type | Frequency | Radiograph | Urine pH | Key association |
|---|---|---|---|---|
| Calcium oxalate | ~75 per cent | Radiopaque | Variable | Hypercalciuria, hyperoxaluria, hypocitraturia |
| Calcium phosphate | 5 to 10 per cent | Radiopaque | High (alkaline) | Distal RTA, hyperparathyroidism |
| Uric acid | 5 to 10 per cent | Radiolucent | Low (acidic) | Gout, myeloproliferative, low urine pH |
| Struvite (Mg ammonium phosphate) | 5 to 15 per cent | Radiopaque | High (alkaline) | Proteus, urease-producing organisms, staghorn |
| Cystine | 1 to 2 per cent | Faintly opaque | Low | Cystinuria (autosomal recessive), hexagonal crystals |
The management mandate: [1]
- Acute renal colic — NSAIDs first-line (diclofenac IM), fluids if dehydrated, antiemetics.
- Assess stone size — below 5 mm passes spontaneously in about 80 per cent; above 10 mm unlikely to pass.
- Medical expulsive therapy — tamsulosin for selected larger distal ureteric stones (contested evidence).
- Intervention when needed — ESWL (stones below 2 cm), ureteroscopy with laser, PCNL (large or staghorn).
- Urgent decompression — obstructed pyelonephritis, AKI from bilateral obstruction or solitary kidney.
- Prevent recurrence — fluid above 3 L/day, normal calcium, reduced sodium and protein, targeted pharmacotherapy. [1]
The single most important exam principle: a low-calcium diet is wrong. Normal calcium intake reduces stone risk because calcium binds intestinal oxalate. The Borghi 2002 NEJM trial proved this definitively [2].
References7ShowHide
- [1]Moe OW Kidney stones: pathophysiology and medical management Lancet, 2006.PMID 16443041
- [2]Borghi L, Schianchi T, Meschi T, et al. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria N Engl J Med, 2002.PMID 11784873
- [3]Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis N Engl J Med, 2014.PMID 25229916
- [4]Pickard R, Starr K, MacLennan G, et al. Medical expulsive therapy in adults with ureteric colic: a multicentre, randomised, placebo-controlled trial Lancet, 2015.PMID 25998582
- [5]Fink HA, Wilt TJ, Eidman KE, et al. Medical management to prevent recurrent nephrolithiasis in adults: a systematic review for an American College of Physicians Clinical Guideline Ann Intern Med, 2013.PMID 23546565
- [6]Hollingsworth JM, Canales BK, Rogers MA, et al. Alpha blockers for treatment of ureteric stones: systematic review and meta-analysis BMJ, 2016.PMID 27908918
- [7]Curhan GC Epidemiology of stone disease Urol Clin North Am, 2007.PMID 17678980