Urinary tract calculi

Question 1

Define and types of stones

Answer 1

•	Crystal deposition within the urinary tract. Also known as nephrolithiasis.
•	Types of Stone:
o	Calcium oxalate - MOST COMMON
o	Calcium phosphate – 20%
o	Uric acid – 10-20%
o	Struvite – 1-5%
o	Cysteine - 2%

Question 2

What are the causes?

Answer 2

•	Metabolic Causes
o	Hypercalciuria
o	Hyperuricaemia 
o	Hypercystinuria
o	Hyperoxaluria
•	Infection
o	Hyperuricaemia
•	Drugs
o	Indinavir

Question 3

What are the risk factors?

Answer 3

o Low fluid intake

o Structural urinary tract abnormalities (e.g. horseshoe kidney)

Question 4

Epidemiology

Answer 4

• COMMON
• 2-3% of general population
• 3 x more common in MALES
• Age group affected: 20-50 yrs
• Bladder stones more common in developing countries
• Upper urinary tract stones more common in industrialised countries
• The prevalence and incident risk of nephrolithiasis are directly correlated with weight and BMI in both genders

Question 5

What are the presenting symptoms?

Answer 5

• Often ASYMPTOMATIC (if in kidney)
• SEVERE loin to groin pain
• Nausea and vomiting
• Urinary urgency, frequency or retention
• Haematuria
• Previous episodes of stones (more than 50% of patients with renal stones will have another episode)

Question 6

What are the signs?

Answer 6

• Loin to lower abdominal tenderness
• NO signs of peritonism
• Leaking AAA is the main differential to consider in older men
• Signs of systemic sepsis if there is an obstruction and infection above the stone

Question 7

What are the appropriate investigations?

Answer 7

•	Bloods
o	FBC - high WCC if infection 
o	U&Es - check renal function
o	Calcium
o	Urate 
o	Phosphate 
•	Urine
o	Dipstick - haematuria is common (may be normal; dipstick positive for leukocytes, nitrates, blood; microscopic analysis positive for WBCs, RBCs, or bacteria)
o	MC&S
•	Urine pregnancy test – exclude ectopic pregnancy and prior to radiation exposure
•	Non-enhanced Spiral CT
o	Can also be used to image stones 
•	X-Ray KUB

o 80% of kidney stones are radio-opaque
• Intravenous Urography (IVU)
o Allows visualisation of the kidneys and ureters
• Ultrasound
o May show hydronephrosis and hydroureter

Question 8

How can you manage an acute presentation?

Answer 8

o Analgesia
o Bed rest
o Antiemetics
o Fluid replacement
o Urine collection to try and retrieve any stone that has passed
• NOTE: most stones < 5 mm will pass spontaneously
o An obstructed, infected kidney is an EMERGENCY and should be treated as soon as possible to relieve the obstruction (e.g. by placing a percutaneous nephrostomy)
o If stone confirmed and bacteriuria: antibiotic therapy and surgical decompression (stent or nephrostomy)

Question 9

What are the treatments?

Answer 9

o Urethroscopy

• A scope is passed into the bladder and up the ureter to visualise the stone
• It can then be removed by a basket or broken up with a laser
• If the stone cannot be removed, a JJ stent should be placed to allow urine drainage
o Extracorporeal Shock-Wave Lithotripsy (ESWL)

• Non-invasive
• An electromagnetic shockwave is focused onto the calculus to break it up into smaller fragments that can pass spontaneously
o Percutaneous Nephrolithotomy (PCNL)
• Performed for large, complex stones (e.g. staghorn calculi)
• After making a nephrostomy tract, a nephroscope is inserted, which allows disintegration and removal of stones

o Depends on the cause (e.g. parathyroidectomy if hypercalcaemia due to hyperparathyroidism, allopurinol if hyperuricaemia)

Question 10

What are the possible complications?

Answer 10

•	Of Stones
o	Infection (PYELONEPHRITIS)
o	Septicaemia 
o	Urinary retention 
•	Of Ureteroscopy
o	Perforation
o	False passage 
•	Of Lithotripsy
o	Pain
o	Haematuria

Question 11

What’s the prognosis?

Answer 11

• GOOD
• However, infection of the calculus could lead to irreversible renal scarring
• Recurrence of about 50% over 5 yrs