Lesson 17

Question 1

What are the two different types of metabolic lithogenesis

Answer 1

By nucleation (hetergeneous nucleation)
By supersaturation (homogeneous nucleation)

Question 2

Metabolic lithogenesis by nucleation

Answer 2

Heterogeneous nucleation

• Cellular debris
• Calcified fragments of papillae
• Other substances act as crystal nucleus.

Question 3

Metabolic lithogenesis by supersaturation

Answer 3

• A solid phase appears when the solute concentration exceeds the saturation level.
• Favoured by dehydration, excessive solute excretion and a urinary pH below 5.5
• Facilitates uric acid and cystine precipitation.
• Decreases phosphate crystallization.
• Oxalate solubility does not depend on pH.

Question 4

Infectious lithogenesis

Answer 4

Ureolytic bacteria hydrolyse urea into CO2 and NH3

This generates an alkaline pH that favours the precipitation of:

• phosphate ammoniac-magnesium (PAM)
• hydroxyapatite carbonate.
• Stones thus formed tend to be calix-like or “deer antler”

Question 5

Main bacteria involved in infectious lithogenesis

Answer 5

• Proteus mirabilis.
• Corynebacteryum urealyticum.
• Staphylococcus saprophyticus.
• Pseudomonas
• Klebsiella.
• Serratia.
• Enterobacter.