Nephrolithiasis: Multiple choice questions!
A 50 year old patient presents with symptomatic nephrolithiasis. He reports that he underwent a jejunoileal bypass for morbid obesity when he was 39. Which of the following is a complication of jejunoileal bypass?
a. Pseudohyperparathyroidism
b. Hyperuric aciduria
c. Hungry bone syndrome
d. Hyperoxaluria
e. Sporadic unicameral bone cysts
The answer is d. (Greenfield, pp 769-770)
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 can subsequently develop due to excessive absorption of oxalate from the colon.
Normally, fatty acids are absorbed by the terminal ileum, and calcium and oxalate combine to form an insoluble compound that is not absorbed.
In the absence of the terminal ileum, unabsorbed fatty acids reach the colon, where they combine with calcium, leaving free oxalate to be absorbed.
Unabsorbed fatty acids and bile acids in the colon also promote oxalate uptake by the colon.
Subsequently, the excess oxalate is excreted by the kidneys, promoting calcium oxalate stone formation.
Hungry bone syndrome refers to rapid remineralization of bone leading to hypocalcemia and can be seen postoperatively in patients with secondary or tertiary hyperparathyroidism.
Pseudohyperparathyroidism refers to hypercalcemia associated with production of parathyroid-related peptide.
A unicameral bone cysts is a benign lesion found in children.
pretest surgery p.1, 19 | 
