26th June 2023

Renal Calculi

Clinical Presentation

Renal calculi most commonly present as renal colic accompanied by microscopic haematuria. Renal colic is typically an abrupt onset of severe unilateral abdominal pain originating in the loin or flank and radiating to the labia in women or to the groin or testicle in men. It occurs in intervals lasting minutes to hours, often accompanied by nausea and/or vomiting.

Fever and rigors might indicate a concurrent urinary tract infection. Whereas intermittent urine stream may suggest obstruction.

Risk factors for stone formation

• Age and gender – highest risk is in men aged 40-60 years
• Ethnicity – urinary stones primarily occur in white people, followed by Hispanics, black people, and Asians
• Diet – excessive intake of oxalate, urate, sodium and animal protein
• Chronic dehydration
• Obesity
• Family history

There are also medical conditions which can predispose to stone formation, including:

• Anatomical abnormalities of the urinary tract, e.g. horseshoe kidney, ureteral stricture, vesico-uretero-renal reflux
• Gastrointestinal conditions, e.g. jejunoileal bypass, intestinal resection, Crohn’s disease, malabsorptive conditions
• Genetic conditions, e.g. cystinuria, primary hyperoxaluria, renal tubular acidosis, cystic fibrosis
• Conditions altering urinary volume or pH, e.g. hyperparathyroidism, nephrocalcinosis, diabetes, hypertension, polycystic kidney disease, gout, sarcoidosis, neurogenic bladder, spinal cord injury, increased levels of vitamin D

Management

The most useful imaging to confirm diagnosis is a non-contrast CT Kidney Ureter and Bladder (KUB).
First line management of pain associated with renal calculi is with NSAIDs, e.g. diclofenac.
Further management of renal calculi depends on the size of stone, location, severity of symptoms and age. Options include:

• Watchful waiting if stone is less than 5mm
• Medical expulsive therapy – using an alpha blocker to help stone passage if it is in the distal ureter and less than 10mm
• Surgical options are offered when pain is ongoing or stone is unlikely to pass. Options include:
  • Shock wave lithotripsy
  • Percutaneous nephrolithotomy
  • Ureteroscopy
  • Open surgery

Biochemical composition of renal calculi

• Calcium oxalate stones – most common and most opaque. Oxalate from food is found in urine, and it forms a salt with calcium that precipitates out of solution very easily, thus even mild dehydration can predispose the individual with high urine oxalate levels to develop renal stones.
• Calcium phosphate
• Uric acid – radiolucent
• Struvite stones – magnesium ammonium phosphate, typically in patients with multiple UTIs
• Cysteine – often in a patient with the rare genetic disorder cystinuria