3 Tesla Na Magnetic Resonance Imaging During Acute Kidney Injury.

Rationale And Objectives: Sodium and proton magnetic resonance imaging (Na/H-MRI) have shown that muscle and skin can store Na without water. In chronic renal failure and in heart failure, Na mobilization occurs, but is variable depending on age, dialysis vintage, and other features. Na storage depots have not been studied in patients with acute kidney injury (AKI).

Materials And Methods: We studied 7 patients with AKI (mean age: 51.7 years; range: 25-84) and 14 age-matched and gender-matched healthy controls. All underwent Na/H-MRI at the calf. Patients were studied before and after acute hemodialysis therapy within 5-6 days. The Na-MRI produced grayscale images containing Na phantoms, which served to quantify Na contents. A fat-suppressed inversion recovery sequence was used to quantify HO content.

Results: Plasma Na levels did not change. Mean Na contents in muscle and skin did not significantly change following four to five cycles of hemodialysis treatment (before therapy: 32.7 ± 6.9 and 44.2 ± 13.5 mmol/L, respectively; after dialysis: 31.7 ± 10.2 and 42.8 ± 11.8 mmol/L, respectively; P > .05). Water content measurements did not differ significantly before and after hemodialysis in muscle and skin (P > .05). Na contents in calf muscle and skin of patients before hemodialysis were significantly higher than in healthy subjects (16.6 ± 2.1 and 17.9 ± 3.2) and remained significantly elevated after hemodialysis.

Conclusions: Na in muscle and skin accumulates in patients with AKI and, in contrast to patients receiving chronic hemodialysis and those with acute heart failure, is not mobilized with hemodialysis within 5-6 days.