A 45-year-old man is involved in an automobile accident and sustains severe injuries with
considerable blood loss and hypotension. He is transferred from the emergency department to an
intensive care unit, where he develops multiorgan failure. During the first 2 days in the intensive
care unit, his plasma phosphate was within normal limits. Subsequently, it began to rise,
eventually reaching 6.0 mg/dL. Failure of which of the following organs would most likely have
this effect?
A. Heart
B. Kidneys
C. Liver
D. Lungs
E. Pancreas
Explanation:
The correct answer is B. The usual cause of hyperphosphatemia is advanced renal insufficiency
that destroys the kidneys’ ability to excrete phosphate, thereby leading to hyperphosphatemia.
Other causes include hypoparathyroidism, pseudohypoparathyroidism, and excessive oral
phosphate administration. Acute transcellular shifts of phosphate into the extracellular space can
also occur in the settings of diabetic ketoacidosis, crush injuries, rhabdomyolysis, systemic
infections, and tumor lysis syndrome.
Failure of the heart (choice A), liver (choice C), or lungs (choice D) has no direct effect on
phosphate metabolism.
Pancreatic failure (choice E) has no direct effect on phosphate metabolism. Diabetic ketoacidosis
can cause a transcellular shift of phosphate into the extracellular space.