Renal and Ureteric Stones

Question 1

What is a Nephrolithiasis/Urolithiasis?

Answer 1

Urinary tract calculi - crystal aggregates and stones that form in the collecting ducts.

Question 2

How are renal and ureteric stones classified? (3).

Answer 2

Based on site of impaction :

1. Pelviureteric Junction (Renal Pelvis - Ureter).
2. Pelvic Brim (Ureters arch over Iliac Vessels).
3. Vesicoureteric Junction (Ureter - Bladder) : commonest.

Question 3

Epidemiology of Renal and Ureteric Stones (3).

Answer 3

1. 3x commoner in Males.
2. Peak Age : 20-40.
3. Lifetime Incidence : 15%; 50% of them have renal colic again within 5 years.

Question 4

What is the main presenting complaint in a symptomatic stone (4)?

Answer 4

RENAL COLIC :

1. Colicky (fluctuating pain severity based on motion of stone).
2. Unilateral.
3. Loin-to-Groin.
4. Excruciating Pain.

Question 5

Clinical Features of Stones (5).

Answer 5

1. Asymptomatic.
2. Renal Colic.
3. Microscopic Haematuria.
4. Oliguria.
5. Nausea and Vomiting.

Question 6

What is a Staghorn Calculus?

Answer 6

A stone involving the renal pelvis and extending into at least 2 calyces.

Question 7

What conditions can predispose Staghorn Calculus development? (3)

Answer 7

1. Alkaline Urine.
2. Struvite (recurrent UTIs - bacteria hydrolyse urea into Ammonia which creates Struvite).
3. Ureaplasma Urealyticum and Proteus Infections.

Question 8

Calcium Oxalate Stones Profile :-

• Proportion of Stones.
• Risk Factors (3).
• Imaging.

Answer 8

Proportion : 85%.
Risk Factor : Hypercalciuria (Main); Hyperoxaluria and Hypocitraturia.
Imaging : Radio-opaque (less than Calcium Phosphate).

Question 9

Why is Hypocitraturia a cause of stones?

Answer 9

Citrate usually forms complexes with Calcium which makes it more soluble.

Question 10

What are the 3 main causes of hypercalcaemia?

Answer 10

1. Calcium Supplementation.
2. Hyperparathyroidism.
3. Cancer e.g. Myeloma, Breast, Lung

Question 11

Cystine Stones Profile :-

• Proportion of Stones.
• Aetiology.
• Imaging.

Answer 11

Proportion : 1%.
Aetiology : Inherited AR Disorder of Transmembrane Cystine Transport leading to reduced absorption of Cystine from the intestine and renal tubule.
Imaging : Radiodense - contain Sulphur; semi-opaque with ground-glass appearance.

Question 12

Uric Acid Stones Profile :-

• Proportion of Stones.
• Risk Factors (2).
• Aetiology.
• Imaging.

Answer 12

Proportion : 5-10% of Stones.
Risk Factors : Gout & Ileostomy (loss of HCO3- and fluid so urine is more acidic).
Aetiology : Uric acid is a product of purine metabolism - precipitating when urinary pH is low e.g. disease with extensive tissue breakdown (malignancy) and kids with inborn errors of metabolism.
Imaging : Radiolucent (not visible on X-Ray).

Question 13

Calcium Phosphate Stones Profile :-

• Proportion of Stones.
• Aetiology.
• Imaging.

Answer 13

Proportion : 10% of Stones.
Aetiology : High Urinary pH causes supersaturation of urine with Calcium and Phosphate = RTA Type I and III.
Imaging : Radio-opaque like bone.

Question 14

Struvite Stones Profile :-

• Proportion of Stones.
• Aetiology.
• Imaging.

Answer 14

Proportion : 2-20% of Stones.
Aetiology : Result of Urease-producing bacteria (chronic infection).
Imaging : Radio-opaque.

Question 15

Give 4 drugs that promote the formation of Calcium stones.

Answer 15

LAST :-

1. Loop Diuretics.
2. Acetazolamide.
3. Steroids.
4. Theophylline.

Question 16

Why do Thiazide Diuretics prevent the formation of Calcium stones?

Answer 16

Increased distal tubular Calcium resorption.

Question 17

Investigations of Renal Stones.

Answer 17

1. Urine Dipstick - Microscopic Haematuria.
2. Urine pH (types of stones).
3. CT KUB (Gold-Standard) within 14 hours of admission.

Question 18

How does urine pH change after a meal?

Answer 18

1. Normal Range = 5-7.
2. Post-prandially (after a meal) - purine metabolism produces uric acid (pH should fall).
3. Alkaline Tide - urine becomes more alkaline later.
4. Look at urine pH for indication of different types of stones.

Question 19

What is CT KUB?

Answer 19

Non-Contrast CT of Kidney, Ureters and Bladder.

Question 20

Alternative of CT KUB.

Answer 20

US KUB - useful in pregnant women and kids.

Question 21

Symptomatic Management of Stones (3).

Answer 21

1. NSAIDs - analgesia of choice e.g. PR/IM Diclofenac (or Paracetamol).
2. Antiemetics - N&V.
3. Antibiotics - Infection.

Question 22

Passage of Stones (2).

Answer 22

1. Less than 6mm = 50% chance of passing without intervention (4 weeks).- WATCH & WAIT.
2. Tamsulosin (a-Blocker) can help spontaneous passage.

Question 23

Surgical Management of Stones (4).

Answer 23

1. Extracorporeal Shock Wave Lithotripsy.
2. Uteroscopy and laser Lithotripsy.
3. Percutaneous Nephrolithotomy.
4. Open Surgery.

Question 24

What is Extracorporeal Shock Wave Lithotripsy (2)?

Answer 24

1. Direct shock wave at stone under X-ray guidance to break it down.
2. Shock waves can cause solid organ injury - analgesia pre and post-procedure.

Question 25

What is Uteroscopy and Laser Lithotripsy (3)?

Answer 25

1. Insert Camera via Urethra, Bladder and Ureter to identify stone and use targeted laser to break it down. 2. Indication : ESWL is contraindicated e.g. pregnancy, complex stone disease. 3. Leave stent in situ for 4 weeks.

Question 26

What is Percutaneous Nephrolithotomy (2)?

Answer 26

1. Insert Nephroscope via small incision in back through kidney to assess ureter. 2. General anaesthesia in theatre.

Question 27

Immediate Emergency Management of Renal Stones (3).

Answer 27

1. Bypass obstruction via Nephrostomy and remove stone using Ureteroscopy. 2. Ureteric Obstruction due to Stones + Infection = Emergency. 3. Decompress using Nephrostomy Tube Placement, Ureteric Catheter and Ureteric Stent.

Question 28

Main Complications of Renal Calculi (2).

Answer 28

1. Obstruction - AKI. | 2. Infection with Obstructive Pyelonephritis.

Question 29

Risk Reduction of Future Episodes of Renal Stones (7).

Answer 29

1. Dehydration - Increase Oral Fluids. 2. Fresh Lemon Juice (Hypercitraturia). 3. Avoiding Carbonated Drinks (Phosphoric Acid promotes Calcium Oxalate stone). 4. Reducing Dietary Salt (6g/day). 5. Reducing Oxalate-Rich Food (Spinach, Nuts, Rhubarb, Tea). 6. Reducing Urate-Rich Food (Kidney, Liver, Sardines). 7. Medications : Potassium Citrate, Thiazide Diuretics e.g. Indapamide.