Nephrolithiasis/Urolithasis (Kidney Stones)

Overview

3% of population have renal stones. Renal stones is the commonest reason for emergency urological admissions. Its peak presentation is during the summer months (dehydration). 90% of urinary calculi are radio-opaque and so are able to be visualised through imaging.

Ureter Anatomy and Phsyiology

Sites of Contriction in the ureter

• Pelvi-ureteric junction – at its origin
• Pelvic brim – as it passess the external iliac artery
• Vesico-ureteric junction – before it enters the bladder

Risk Factors

Clinical Manifestation

Clinical Presentation

• Severe intermittent, stabbing pain radiating from loin to groin
• Microscopic haematuria (rarely macroscopic)
• Nausea/vomiting
• Fever

Examination

• Fever
• Tachycardia
• loin or renal angle tenderness
• Iliac fossa tenderness if the calculus has passed into the distal ureter

Differential Diagnosis

• Bladder carcinoma
• Aortic aneurysm
• Myocardial Infarction
• Acute Cholecytitis
• Ectopic pregnancy
• Mesenteric Ischaemia
• Appendicitis
• Acute pancreatitis

Investigations

• Urinalysis and MCS – Microscopic haematuria is seen in the majority of patients with renal stones. Assess level of calcium, uric acid, oxalate and citrate
• FBC and differential – Raised WBCs may suggest pyelonephritis/UTI/pyonephrosis (infection above obstructed stone).
• EUC
  • Include sodium, potassium, chloride, bicarbonate, creatinine, urea, calcium, uric acid, and phosphorus.
  • Assesses renal function
  • Hypercalcaemia may suggest hyperparathyroidism as an underlying aetiology
  • Hyperuricaemia may indicate gout
• Urine b-HCG (female) – exclude ectopic
• Plain abdominal X-ray: calculi that contain calcium are radiodense
• Renal ultrasound
• Non-contrast helical CT

Renal Stone

• Renal stones are crystalline mineral depositions that form from microscopic crystals in the loop of Henle, distal tubules, or the collecting duct.
• This is usually in response to:
  1. Elevated levels of urinary solutes such as calcium, uric acid, oxalate, and sodium.
  2. Decreased levels of stone inhibitors such as citrate and magnesium.
  3. Low urinary volume
  4. Abnormally low or high urinary pH.
• All of these can lead to urine supersaturation with stone-forming salts and subsequent stone formation.
• Calcareous stones account for more than 80% of stones. Uric acid stones represent about 5–10%, trailed by cystine, and struvite.

Pathophysiology

The driving force behind stone formation is the supersaturation of urine.

• Ureteric colic from nephrolithiasis is secondary to obstruction of the collecting system by the stone.
• If the stone is sharp or larger than the normal lumen of the ureter (approximately 3 mm), it causes excessive distension of this muscular tube.
• The stretching of the collecting system or ureter is due to an increase in intraluminal pressure.
• This causes nerve endings to stretch and therefore the sensation of renal colic.
• The pain is referred to the cutaneous areas innervated by spinal cord segments and sensory ganglia, which also receive visceral afferents from the ureter, mainly T11- L2.
• A stone in the upper ureter typically causes pain in the loin, while a stone in the lower ureter typically causes pain in the loin and iliac fossa, with radiation to the testis or labia, or groin.
• The pain passes inferoanteriorly “from the loin to the groin” as the stone progresses through the ureter.
• Pain can also be due to local inflammatory mediators, oedema, hyperperistalsis, and mucosal irritation.
• Stones may collect anywhere from the collecting ducts to the urethra, but most common are:
  • Pelvi-ureteric junction
  • Pelvic brim
  • Vesico-ureteric junction

Treatment

It is not necessary to treat every kidney stone. As a rule of thumb, the younger the patient, the larger the stone and the more symptoms it is causing, the more inclined we are to recommend treatment.

Treatment options for kidney stones

• Extracorporeal lithotripsy
• Percutaneous nephrolithotomy
• Open stone surgery

Acute management for ureteric stones 

• NSAIDs or opioids
• Watchful waiting
• Emergency temporary relief
  • Stent insertion
  • Percutaneous nephrostomy (if infection)

Treatment for ureteric stones

• Extracorporeal lithotripsy
• Ureteroscopy
• Percutaneous nephrolithotomy
• Open ureterolithotomy
• Laparoscopic ureterolithotomy
• Percutaneous antegrade ureteroscopy

Treatment of bladder stones

• Removed via cystoscopy

Prevention of future stones

• Education about risk factors
• Drink more water
• Eating foods and drinks in calcium is good, rather high calcium intake is associated with a low risk of stone formation
• ↓sodium intake
• ↓animal proteins
• ↓alcohol
• ↑vegetables
• ↓thiazide diuretics

Complications and Prognosis

Complications

• Recurrent UTI
• Recurrent calculi
• Obstruction
• Trauma

References

Australian Doctor – renal stones
Australian Family Physician – Urinary stone disease
BMJ: http://bestpractice.bmj.com.ipacez.nd.edu.au/best-practice/monograph/225/diagnosis/history-and-examination.html
Davidson’s Principles and Practices of Medicine
NEJM: http://www.nejm.org.ipacez.nd.edu.au/doi/full/10.1056/NEJMcp030813