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.

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

Clinical Presentation

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

Flank PainUreteric/renal colic

Examination

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

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

• 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 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.

• 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

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