Urolithiasis

Question 1

Explain the gross anatomy of the kidneys and ureters

Answer 1

• Kidneys are paired retroperitoneal organs located between T12 and L3, covered in Gerota’s fascia.
• Ureters are 30cm long with 3 segments and 4 layers

Question 2

Where are the physiological narrowing’s of the ureters?

Answer 2

1. Pelvi-ureteric junction,
   - Crossing iliac vessels at pelvic brim,
   - VU junction

Question 3

What are the intrinsic and extrinsic risk factors for urolithiasis

Answer 3

Intrinsic - Age, sex (males>females because men have high oxalate production), genetics
Extrinsic factors - Geography (hot>cold climates), more common in summer, dehydration, diet high in animal protein, salt and low in calcium salts and sedentary lifestyle

Question 4

What are kidney stones commonly made up of?

Answer 4

• Most commonly calcium oxalate.
• Uric acid stones (form due to chronic dehydration)
• Calcium phosphate and calcium oxalate.
• Pure calcium phosphate (rare)
• Struvite (infection stones)
• Cysteine (rare, occur due to inherited disorder)

Question 5

Why do renal stones form?

Answer 5

• Supersaturation of solute with absence of inhibitors this is an unstable state when stones form.
• In a metastable state there is supersaturation of solute but with the presence of inhibitors

Question 6

What are factors which will increase risk of renal stone formation?

Answer 6

• Low volume, low pH, low citrate and low magnesium (citrate and magnesium are stone formation inhibitors).
• High uric acid, high calcium and high oxalate

Question 7

How do patients with renal stones present?

Answer 7

• Can be asymptomatic so incidental finding.
• Renal colic pain which radiates from loin to groin, very severe pain.
• Restless
• Haematuria (often non visible but can be visible)
• Sepsis (uncommon)

Question 8

hat are the initial investigations for a patient with kidney stones?

Answer 8

• History and exam,
• Bloods (U+Es, CRP and FBC)
• Urinalysis,
• Imaging - Gold standard is CT KUB (non contrast)

Question 9

What are the biochemical workup investigations for patients with their first kidney stone vs recurrent stones?

Answer 9

• First stone - U&Es, calcium, parathyroid hormone, Vitamin D, urate, urine dip, MSSU, stone analysis.
• If patient presents with recurrent stones then do U&Es, calcium, urate, venous bicarbonate and 24 urine analysis

Question 10

What are the different imaging used in investigation of kidney stones?

Answer 10

• CT KUB (gives info on stone diameter, skin to stone distance, no contrast used and lower radiation dose)
• Ultrasound (benefits young patients by avoiding radiation)
• Xray KUB (lower radiation dose and better for following up a known stone)

Question 11

What are the medical therapies for kidney stones?

Answer 11

• Analgesia with NSAIDs as they reduce pain due to reduced glomerular filtration, reduced renal pressure and reduced ureteric peristalsis.

Question 12

What are the surgical options for kidney stones?

Answer 12

• Ureteroscopy and basket or fragmentation.
• Flexible ureteroscopy
• Extracorporeal shockwave lithotripsy,
• Percutaneous nephrolithotomy
• Emergency stent or nephrostomy

Question 13

When is admission required for kidney stones?

Answer 13

• Uncontrollable pain,
• fever/signs of sepsis,
• Solitary kidney with a ureteric stone (only one kidney)
• Bilateral ureteric stone,
• Renal failure caused by an obstructive stone

Question 14

What are the differentials for an emergency presentation of kidney stones?

Answer 14

• Abdominal aortic aneurysm,
• Appendicitis,
• Gyn pathology such as ectopic pregnancy or torsion
• Testicular pain

Question 15

What is the management of a patient with sepsis and an obstructing kidney stone?

Answer 15

• Urological emergency
• Implement the sepsis 6 ensuring to take cultures and give antibiotics after.
• Check bloods, renal function and inflammatory markers.
• Urgent imaging with ultrasound or CT

Question 16

What is the presentation of an elective kidney stone and their options for treatment?

Answer 16

• Pain, recurrent UTIs, haematuria, incidental finding of acute/chronic KD.
• Can just keep patient under observation or undergo surgical intervention

Question 17

What is extracorporeal shockwave lithotripsy?

Answer 17

• Use of shockwaves to directly breakdown the kidney stone or to cause a microbubble which causes microjets that cause fragmentation of stone

Question 18

What is a staghorn Calculi?

Answer 18

• A branched kidney stone which fills up all/part o the renal pelvis.
• Most commonly struvite (magnesium ammonium phosphate)