Makindo Medical Notes

🪨 Urinary Tract Calculi (Renal & Ureteric 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 5–10 mm may pass with medical expulsive therapy (MET) such as Tamsulosin 400 μg OD. Larger stones (>10 mm) often need surgical intervention.

📖 About

• Renal colic: Acute, severe, intermittent flank/loin pain caused by obstruction of urine flow, typically radiating “loin to groin”.
• 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).

📊 Epidemiology

• Annual incidence: 1–2 per 1000 people; lifetime risk ~10–15%.
• Peak: men aged 20–50; men affected 2–3× more than women.
• Recurrence rate: 30–50% within 10 years.

🧬 Pathophysiology of Pain

• Stone obstructs urinary flow → ↑ intraluminal pressure → stretching of renal capsule and ureteric wall.
• Stimulates prostaglandin release → smooth muscle spasm and vasodilation.
• Results in severe, colicky pain + nausea/vomiting via vagal stimulation.

⚠️ 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

🧪 Types of Stones

• 🧂 Calcium oxalate/phosphate (70–80%): Hypercalciuria, hyperoxaluria, hyperparathyroidism.
• 🦠 Struvite (Mg ammonium phosphate): Infection with urease-producing bacteria (Proteus, Klebsiella).
• 🧬 Cystine stones: Due to cystinuria, rare, recurrent, often large.
• 💡 Urate stones: Idiopathic, gout, hyperuricosuria, chemotherapy (tumour lysis).

📸 Images

🎯 Risk Factors

• Chronic dehydration, hot climates
• Family history of stones
• Metabolic: hyperparathyroidism, gout, obesity
• GI disease: Crohn’s, ileal resection, malabsorption
• Medications: protease inhibitors, acetazolamide, loop diuretics, topiramate
• Diet: high sodium, animal protein, vitamin C/D excess

🩺 Clinical Features

• Pain: Sudden, severe, colicky, radiates loin → 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 → red flag for urosepsis.
• Nausea, vomiting, ileus.

🧾 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).

🔎 Investigations

• Bloods: FBC, U&E, Ca, phosphate, urate, PTH, CRP, glucose.
• Urinalysis: Haematuria (80–90%), pyuria ± 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).

🧾 Differential Diagnosis

• Abdominal aortic aneurysm (AAA) – MUST exclude.
• Appendicitis.
• Diverticulitis.
• Gynaecological causes: ovarian torsion, ectopic pregnancy.

🚑 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.

💊 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 μg OD for distal ureteric stones ≤10 mm.
  • Increases stone passage rates and reduces analgesic requirements.
• Indications for urgent urology: sepsis + obstruction → nephrostomy or ureteric stent.
• Observation (watchful waiting): stones <5 mm likely to pass; larger stones may be trialled if pain controlled.

🔨 Surgical Treatment

• ⚡ Shockwave lithotripsy (SWL): Non-invasive, outpatient; fragments stones with shockwaves.
• 🔍 Ureteroscopy (URS): Endoscopic laser fragmentation + retrieval.
• 🩻 Percutaneous nephrolithotomy (PCNL): For large (>20 mm) or staghorn calculi.
• ✂️ Open/laparoscopic surgery: Rare; reserved for complex or failed minimally invasive options.

🛡️ Prevention

• Hydration: target urine output 2–3 L/day.
• Dietary: reduce salt/protein, normal calcium intake, avoid cola (phosphoric acid), add citrus (↑ 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.

📚 References

• NICE CKS: Acute Renal/Ureteric Colic
• Campbell-Walsh Urology, 12th Edition
• Bailey & Love’s Short Practice of Surgery, 28th Edition