A 35 -year-old male with presents with spasmodic pain
radiating from his left loin to his left groin. He has previously had an
ileocolic resection for Crohn’s disease, which was well controlled on
On examination his abdomen was soft, there was tenderness
in the left loin. Urinalysis
Protein or Nitrates negative
X-ray KUB radio-opaque area over left ureter
What is the most likely cause of the renal stone?