Urinary Tract Calculi

Question 1

Definition of nephrolithiasis

Answer 1

Refers to the presence of crystalline stones (calculi) within the urinary system (kidneys, ureter, bladder and urethra)

Question 2

Aetiology of nephrolithiasis

Answer 2

There are different types of renal stone:
◦ Calcium Oxalate (75%)- Most COMMON
◦ Struvite
◦ Urate

• Renal stones are crystalline mineral depositions that usually form in the collecting ducts
• This is usually due to elevated levels of urinary solutes such as:
◦ Calcium
◦ Uric acid
◦ Oxalate
◦ Sodium
• Low urinary volume or high urinary pH can also contribute to this process

Question 3

Pathophysiology of nephrolithiasis

Answer 3

• The renal colic from nephrolithiasis is secondary to obstruction of the collecting system by the stone.
• There would be stretching of the system or the ureter due to an increased intraluminal pressure
• This would cause nerve endings to stretch; hence the renal colic sensation

Question 4

History and Examination nephrolithiasis

Answer 4

• Asymptomatic: Can be asymptomatic is un-obstructing
• Acute, severe flank pain:
• Very severe loin to groin pain
• Acute onset
• Usually no tenderness on palpating
• Nausea/Vomiting
• Cannot lie still
• Haematuria: Usually microscopic, but can be macroscopic
• Urinary frequency/urgency: If stoke lodged in distal ureter, may lead to bladder irritation which can manifest like this
• Risk factors:
• Dehydration
• Diet (high salt intake)
• White
• Male
• Obesity
• Previous episodes of nephrolithiasis
• Medication: diuretics, antacids, corticosteroids etc

Question 5

Investigations for nephrolithiasis

Answer 5

• Non-Contrast CT (non pregnant): Request urgent CT (within 24 hours of presentation) for suspected renal colic. Has high sensitivity and specificity (can determine the size and location of stones). Would be able to see the calcification/stone
• Urinalysis: Likely to see micro haematuria
• FBC: may have a raised WCC if infection is present
• Electrolytes and U&Es: may see hypercalcaemia
• Pregnancy test: exclude pregnancy and see if contraindication for CT

Question 6

Treatment for nephrolithiasis

Answer 6

1) Hydration and Analgesia: Give NSAIDs as first line, and IV fluids for hydration
• Oral antibiotics if sign of infection
• Medical expulsive therapy: For stones <10mm you can use alpha blockers (e.g tamsulosin) to promote stone passage

• Consider surgical intervention:
◦ If <5mm then wait for stone to pass spontaneously
◦ For larger stones (>10mm) and smaller stones that remain despite conservative therapy, you can consider Shock wave lithotripsy (non-invasive, electromagnetic shockwave breaks up the calculus into smaller fragments so they can pass)
◦ If this fails, you would try ureteroscopy: scope passed into bladder and up ureter

Question 7

Prevention and prognosis of nephrolithiasis

Answer 7

• Prevent nephrolithiasis is adequate hydration
• Decreased sodium intake but normal calcium intake
• Secondary: Maintain adequate hydration, eat fibre, eat things in moderation

• Is a lifelong disease process. 50% risk of recurrence in the next 5 years

Question 8

Complications of nephrolithiasis

Answer 8

• Infection (pyelonephritis) due to stones
• Septicaemia
• Urinary retention
• Pain and haematuria from lithotripsy