Acute Renal / Ureteric Colic & Urinary Tract Stones ✅

📖 About

• Renal/ureteric colic: Sudden-onset, severe, intermittent colicky pain from ureteric obstruction, typically radiating from loin/flank to groin, scrotum/labia, or inner thigh.
• Pain often causes extreme restlessness (“cannot keep still”), unlike peritonism (where patients lie still).
• Red flags — always exclude: ruptured AAA, appendicitis, ectopic pregnancy, ovarian torsion, obstructed solitary/transplant kidney, urosepsis.

Typical radiation pattern of renal/ureteric colic pain (loin to groin).

📊 Epidemiology

• Annual incidence: ~1–2 per 1000 population; lifetime risk 10–15% (higher in men and certain regions/climates).
• Peak age: 20–60 years; male:female ratio ~2–3:1 (though gap narrowing).
• Recurrence rate: 30–50% within 5–10 years without prevention.

🧬 Pathophysiology of Pain

• Ureteric obstruction → increased intraluminal pressure → distension of renal capsule and ureteric smooth muscle.
• Triggers prostaglandin release → smooth muscle spasm and intense colicky pain.
• Associated nausea/vomiting from vagal/GI stimulation; ileus possible.
• Prolonged obstruction → hydronephrosis → potential renal impairment.

⚠️ Differential Diagnosis / Causes of Obstruction

• Most common: urinary tract calculi.
• Other: sloughed papilla (e.g., papillary necrosis in diabetes, sickle cell, analgesics), blood clot (trauma/tumour), stricture/PUJ obstruction, external compression (e.g., tumours), rare foreign bodies.

🧪 Stone Composition (Approximate %)

• 🧂 Calcium-based (oxalate/phosphate): 70–80% — linked to hypercalciuria, hyperoxaluria, hyperparathyroidism, hypocitraturia.
• 🦠 Struvite (magnesium ammonium phosphate): 10–15% — infection-related (urease-producing bacteria e.g., Proteus, Klebsiella), alkaline urine, often staghorn.
• 🧬 Cystine: 1–2% — genetic cystinuria; recurrent, often bilateral/large.
• 💡 Uric acid: 5–10% — hyperuricosuria (gout, high purine diet, tumour lysis), acidic urine.
• Rare: xanthine, drug-induced (e.g., indinavir, atazanavir).

Examples of different kidney stone types: calcium oxalate (top-left), uric acid (top-right), struvite (bottom-left), staghorn (bottom-right).

🎯 Risk Factors

• Low fluid intake / dehydration / hot climates.
• Family history / genetic predisposition.
• Metabolic: primary hyperparathyroidism, gout, obesity, diabetes.
• GI: inflammatory bowel disease (Crohn’s), ileal resection, chronic diarrhoea (enteric hyperoxaluria).
• Drugs: topiramate, acetazolamide, loop diuretics, protease inhibitors, vitamin C/D excess.
• Dietary: high salt, high animal protein, low citrate (low fruit), high oxalate (spinach, nuts), sugary drinks.

🩺 Clinical Features

• Severe colicky flank pain radiating to groin/genitalia; episodic every few minutes.
• Restlessness, diaphoresis; nausea/vomiting common (50–80%).
• Haematuria (micro/macro) in ~80–90%.
• LUTS: frequency, urgency, dysuria if distal stone.
• Red flags: fever/rigors, hypotension, AKI, anuria/oliguria → urgent admission.

🔎 Investigations (NICE NG118 Aligned)

• Bloods: FBC, U&E (check AKI), CRP, calcium, phosphate, urate; consider PTH if hypercalcaemia.
• Urinalysis: dipstick + MC&S; haematuria common; infection markers if febrile.
• Imaging:
  • Low-dose non-contrast CT KUB: gold standard (>95% sensitivity/specificity); urgent (within 24 hours) for suspected renal colic in adults.
  • Ultrasound: first-line in pregnancy, children/young people (assess hydronephrosis); consider CT if diagnostic uncertainty.
  • Plain KUB X-ray: limited (misses uric acid/cystine); useful for radio-opaque stone follow-up.
• Stone analysis: mandatory for all passed/removed stones.
• Metabolic evaluation (recurrent stones): 24-hour urine (volume, pH, Ca, oxalate, citrate, urate, etc.); consider in first-time stone formers with risk factors.

Example low-dose CT KUB: calcified stone in ureter with proximal hydronephrosis (dilated collecting system).

🚑 Indications for Admission / Urgent Urology Review (NICE-aligned)

• Suspected/confirmed urosepsis (fever, rigors, hypotension, elevated CRP/WBC).
• Uncontrolled pain despite analgesia or intractable vomiting.
• Solitary kidney, bilateral obstruction, or transplanted kidney.
• Acute kidney injury / rising creatinine.
• Diagnostic uncertainty (e.g., possible AAA, appendicitis).
• Stone >10 mm with ongoing symptoms or proximal location.

💊 Acute Management (NICE NG118 / CKS)

• Pain relief: NSAID first-line (e.g., diclofenac 75 mg IM/IV/PR/PO); any route effective.
• If NSAIDs contraindicated/not enough: IV paracetamol.
• Opioids (e.g., morphine) only if above fail; avoid routinely.
• Do not use antispasmodics.
• IV fluids if dehydrated/vomiting (monitor for overload).
• Antiemetics: e.g., ondansetron 4–8 mg IV, cyclizine, metoclopramide.
• MET: Consider alpha-blocker (e.g., tamsulosin 400 μg OD) for distal ureteric stones <10 mm (off-label; discuss risks/benefits).
• Watchful waiting: Appropriate for small stones likely to pass; monitor symptoms, renal function, repeat imaging if needed.
• Urgent intervention: Sepsis/obstruction → percutaneous nephrostomy or ureteric stenting; then definitive treatment.

🔨 Definitive Stone Management (NICE NG118)

• Extracorporeal shockwave lithotripsy (SWL): Non-invasive; good for <20 mm renal/upper ureteric stones.
• Ureteroscopy & laser lithotripsy (URS): Preferred for ureteric stones; high success.
• Percutaneous nephrolithotomy (PCNL): For large renal stones (>20 mm) or staghorn calculi.
• Open/laparoscopic: Very rare.
• Timing: Offer intervention within 48 hours if pain ongoing/not tolerated or stone unlikely to pass.

🛡️ Prevention & Long-term Management (NICE NG118)

• General advice (all stone types): Fluid intake to achieve urine output >2–2.5 L/day; limit salt (<6 g/day) and animal protein; normal dietary calcium; increase citrus fruits (↑ citrate).
• Avoid excess vitamin C, sugary drinks; maintain healthy weight.
• Stone-specific:
  • Calcium oxalate: potassium citrate if hypocitraturia; thiazides if hypercalciuria + low-salt diet.
  • Uric acid: allopurinol if hyperuricosuria; urinary alkalinisation (potassium citrate/sodium bicarbonate).
  • Struvite: treat/prevent UTIs; acetohydroxamic acid rare.
  • Cystine: high fluid + chelating agents (e.g., tiopronin) if needed.
• Manage underlying conditions (e.g., parathyroidectomy for hyperparathyroidism).
• Follow-up: imaging/biochemistry for recurrent stone formers.