Kidney Stones and Renal Colic: Diagnosis and Treatment

Kidney stones (urolithiasis) are hard deposits that form in the urinary tract. They are very common in hot climates, including Pakistan, where dehydration is frequent. A stone passing down the ureter causes renal colic, one of the most severe pains a person can experience.

Types of stones

• Calcium oxalate (with or without calcium phosphate) — the most common type.
• Uric acid — associated with gout, a high-purine diet and dehydration. These stones are radiolucent on plain X-ray.
• Struvite (magnesium ammonium phosphate) — associated with infection by urease-producing bacteria such as Proteus; can form large "staghorn" stones.
• Cystine — in the inherited condition cystinuria.

Risk factors

• Low fluid intake and hot climates.
• Previous stones.
• Family history.
• Obesity.
• Diets high in salt and animal protein.
• Hypercalciuria and hyperparathyroidism.
• Gout.
• Inflammatory bowel disease.
• Some medicines.
• Anatomical abnormalities.

Clinical features

• Renal colic: sudden, severe, colicky pain in the loin, often radiating to the groin or genitals. The patient is restless and cannot lie still.
• Nausea and vomiting.
• Blood in the urine (often microscopic).
• Urinary frequency or urgency when the stone is near the bladder.
• Fever with these symptoms suggests an infected, obstructed kidney. This is an emergency.

In older patients, a leaking abdominal aortic aneurysm can mimic renal colic and must be considered.

Investigations

• Urine dipstick: blood. Send a culture if infection is possible.
• Blood tests:
  • kidney function
  • full blood count
  • CRP
  • calcium and urate
• Imaging: non-contrast CT of the kidneys, ureters and bladder (CT KUB) is the investigation of choice in most adults. Ultrasound is preferred in pregnancy and children, and useful to look for hydronephrosis.
• After recovery: stone analysis and a metabolic work-up for recurrent stone formers.

Management

• Analgesia: NSAIDs (for example diclofenac) are first-line for renal colic if there are no contraindications. Paracetamol and opioids are alternatives.
• Watchful waiting: many stones under 5 mm pass by themselves.
• Medical expulsive therapy: an alpha-blocker (for example tamsulosin) may help distal ureteric stones of about 5–10 mm pass.
• Procedures for larger stones, ongoing pain or failure to pass:
  • extracorporeal shock wave lithotripsy (ESWL)
  • ureteroscopy with laser fragmentation
  • percutaneous nephrolithotomy (PCNL) for large renal stones
• Emergency decompression (nephrostomy or ureteric stent) plus antibiotics for:
  • an obstructed infected kidney
  • a solitary kidney
  • bilateral obstruction
  • uncontrolled pain

Prevention

• Drink enough fluid to pass about 2–2.5 litres of urine a day.
• Reduce salt and excess animal protein.
• Keep a normal calcium intake. Restricting calcium can increase oxalate stones.
• Specific treatment based on stone type and metabolic tests:
  • potassium citrate
  • thiazides for hypercalciuria
  • allopurinol for uric acid stones

Exam pearls

• Fever plus an obstructing stone means urgent drainage. Antibiotics alone are not enough.
• Uric acid stones are radiolucent on plain X-ray but visible on CT.
• Always consider a leaking aortic aneurysm in an older patient with "renal colic".

See also Urinary Tract Infection and the urology part of our Surgery Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Imaging of choice for suspected renal colic in non-pregnant adults:

   1. MRI
   2. IV urogram
   3. Ultrasound only
   4. Plain X-ray KUB
   5. Non-contrast CT KUB
   Show answer

   Answer: E. Non-contrast CT KUB
   Non-contrast CT KUB is the most sensitive test; ultrasound in pregnancy and children.

2. Which stones are radiolucent on plain X-ray?

   1. Cystine only
   2. Uric acid
   3. Calcium phosphate
   4. Struvite
   5. Calcium oxalate
   Show answer

   Answer: B. Uric acid
   Uric acid stones are radiolucent on plain film but seen on CT.

3. First-line analgesia for renal colic without contraindications:

   1. Paracetamol only
   2. Oral codeine
   3. Buscopan only
   4. No analgesia
   5. An NSAID such as diclofenac
   Show answer

   Answer: E. An NSAID such as diclofenac
   NSAIDs are first-line for renal colic.

4. Staghorn calculi associated with Proteus infection are made of:

   1. Xanthine
   2. Cystine
   3. Struvite
   4. Uric acid
   5. Calcium oxalate
   Show answer

   Answer: C. Struvite
   Urease-producing bacteria raise urine pH and form struvite (magnesium ammonium phosphate).

5. An older man with 'renal colic' and hypotension. Which diagnosis must be excluded?

   1. Gastritis
   2. Appendicitis
   3. Gallstones
   4. Leaking abdominal aortic aneurysm
   5. Hernia
   Show answer

   Answer: D. Leaking abdominal aortic aneurysm
   A ruptured AAA can mimic renal colic and is rapidly fatal.

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• Chronic Kidney Disease (CKD): Stages, Complications and TreatmentCKD G and A staging, causes, complications such as anaemia and bone disease, ACE inhibitors, SGLT2 inhibitors and planning for kidney failure.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.