A 50-year-old patient presents with symptomatic nephrolithiasis. ..

A 50-year-old patient presents with symptomatic nephrolithiasis. He reports that he underwent a
jejunoileal bypass for morbid obesity when he was 39.
One would expect to find
a. Pseudohyperparathyroidism
b. Hyperuric aciduria
c. “Hungry bone” syndrome
d. Hyperoxaluria
e. Sporadic unicameral bone cysts

Answer:
d. Hyperoxaluria

Discussion: Any patient who has lost much of the ileum (whether from injury, disease, or elective surgery) is at high risk of developing enteric hyperoxaluria if the colon remains intact.
Calcium oxalate stones will develop in at least 10% of these patients. The condition results from excessive absorption of oxalate from the colon through two related synergistic mechanisms:

1. unabsorbed fatty acids combine with calcium, which prevents the formation of insoluble calcium oxalate and allows oxalate to remain available for colonic absorption; and
2. unabsorbed fatty acids and bile acids also increase the permeability of the colon to the oxalate.