Urinary tract calculi (stones)
Urinary tract stones are crystalline mineral deposits that form in the kidneys and may migrate into the ureters, causing obstruction.
Stones <5 mm (especially distal ureteric) usually pass spontaneously within 4 weeks.
Stones 5โ10 mm may pass with medical expulsive therapy (MET) such as Tamsulosin 400 ฮผg OD.
Larger stones (>10 mm) often need surgical intervention.
๐ About
- Renal colic: Acute, severe, intermittent flank/loin pain caused by obstruction of urine flow, typically radiating โloin to groinโ.
- Ureteric colic: Pain radiating to groin, scrotum, labia, or inner thigh due to stone migration.
- Common surgical referral. Always exclude other serious causes (e.g. ruptured AAA, appendicitis).
๐ Epidemiology
- Annual incidence: 1โ2 per 1000 people; lifetime risk ~10โ15%.
- Peak: men aged 20โ50; men affected 2โ3ร more than women.
- Recurrence rate: 30โ50% within 10 years.
๐งฌ Pathophysiology of Pain
- Stone obstructs urinary flow โ โ intraluminal pressure โ stretching of renal capsule and ureteric wall.
- Stimulates prostaglandin release โ smooth muscle spasm and vasodilation.
- Results in severe, colicky pain + nausea/vomiting via vagal stimulation.
โ ๏ธ Causes of Renal/Ureteric Obstruction
- Renal calculus (most common)
- Sloughed papilla (e.g. papillary necrosis in diabetes, sickle cell)
- Blood clot (trauma, renal tumour)
- Ureteric stricture or PUJ obstruction
- Rare: tumour, foreign body
๐งช Types of Stones
- ๐ง Calcium oxalate/phosphate (70โ80%): Hypercalciuria, hyperoxaluria, hyperparathyroidism.
- ๐ฆ Struvite (Mg ammonium phosphate): Infection with urease-producing bacteria (Proteus, Klebsiella).
- ๐งฌ Cystine stones: Due to cystinuria, rare, recurrent, often large.
- ๐ก Urate stones: Idiopathic, gout, hyperuricosuria, chemotherapy (tumour lysis).
๐ธ Images
๐ฏ Risk Factors
- Chronic dehydration, hot climates
- Family history of stones
- Metabolic: hyperparathyroidism, gout, obesity
- GI disease: Crohnโs, ileal resection, malabsorption
- Medications: protease inhibitors, acetazolamide, loop diuretics, topiramate
- Diet: high sodium, animal protein, vitamin C/D excess
๐ฉบ Clinical Features
- Pain: Sudden, severe, colicky, radiates loin โ groin/scrotum/labia.
- Behaviour: Patients restless, unable to lie still (contrast with peritonitis).
- Haematuria (microscopic or macroscopic).
- Lower urinary tract symptoms (frequency, hesitancy, weak stream).
- Fever, rigors, tachycardia, hypotension โ red flag for urosepsis.
- Nausea, vomiting, ileus.
๐งพ History to Elicit
- Past episodes of stones or UTI.
- Family history of nephrolithiasis.
- History of fractures, immobility (hypercalciuria).
- Dietary intake: milk/alkali, high salt, vitamin supplements.
- Medications (esp. antiretrovirals, diuretics, antiepileptics).
๐ Investigations
- Bloods: FBC, U&E, Ca, phosphate, urate, PTH, CRP, glucose.
- Urinalysis: Haematuria (80โ90%), pyuria ยฑ bacteriuria if infected.
- Imaging:
- CT KUB (non-contrast): Gold standard, >95% sensitive; perform within 24 h (ambulatory if stable).
- USS: First-line in pregnancy, children, young adults.
- Plain KUB X-ray: Limited (misses urate/cystine stones), but useful for follow-up.
- Stone analysis: All passed/removed stones should undergo biochemical analysis.
- 24h urine collection: Assess calcium, oxalate, urate, citrate, cystine (recurrent formers).
๐งพ Differential Diagnosis
- Abdominal aortic aneurysm (AAA) โ MUST exclude.
- Appendicitis.
- Diverticulitis.
- Gynaecological causes: ovarian torsion, ectopic pregnancy.
๐ Indications for Admission
- Sepsis/urosepsis (fever, hypotension, rigors).
- Uncontrolled pain or vomiting.
- Solitary kidney or transplanted kidney.
- Worsening renal function/AKI.
- Diagnostic uncertainty (AAA, appendicitis).
- Suspected bilateral obstruction.
๐ Management
- Supportive:
- Analgesia: NSAIDs (diclofenac 75 mg IV/PR) are first-line; opioids second-line if NSAIDs contraindicated.
- IV fluids: 2L/day if dehydrated or vomiting.
- Antiemetics: ondansetron, cyclizine.
- Medical expulsive therapy (MET):
- Tamsulosin 400 ฮผg OD for distal ureteric stones โค10 mm.
- Increases stone passage rates and reduces analgesic requirements.
- Indications for urgent urology: sepsis + obstruction โ nephrostomy or ureteric stent.
- Observation (watchful waiting): stones <5 mm likely to pass; larger stones may be trialled if pain controlled.
๐จ Surgical Treatment
- โก Shockwave lithotripsy (SWL): Non-invasive, outpatient; fragments stones with shockwaves.
- ๐ Ureteroscopy (URS): Endoscopic laser fragmentation + retrieval.
- ๐ฉป Percutaneous nephrolithotomy (PCNL): For large (>20 mm) or staghorn calculi.
- โ๏ธ Open/laparoscopic surgery: Rare; reserved for complex or failed minimally invasive options.
๐ก๏ธ Prevention
- Hydration: target urine output 2โ3 L/day.
- Dietary: reduce salt/protein, normal calcium intake, avoid cola (phosphoric acid), add citrus (โ citrate, alkalinises urine).
- Specific:
- Potassium citrate for recurrent calcium oxalate stones with hypocitraturia.
- Thiazides for recurrent calcium stones with hypercalciuria (with low Na diet).
- Allopurinol for uric acid stones with hyperuricosuria.
- Address underlying causes: hyperparathyroidism, metabolic disorders.
๐ References
