The assumption that sodium accumulation in the human body is always accompanied by water retention has been challenged by data showing that sodium can be stored nonosmotically. Here we investigated the contribution of nonosmotic sodium storage to short-term sodium homeostasis after hypertonic saline infusion in healthy individuals on a low-sodium diet. During four hours after infusion, we compared the observed changes in plasma sodium concentration and urinary cation excretion with changes that were calculated with the Adrogue-Madias and Nguyen-Kurtz formula, formulations widely implemented to guide the treatment of dysnatremias. We included 12 healthy non-smoking male individuals with normal blood pressure, body mass index, and kidney function. Right after infusion, the average observed plasma sodium change from baseline (3.5 mmol/L) was similar to the predicted changes by the Adrogue-Madias (3.3 mmol/L) and Nguyen-Kurtz formula (3.1 mmol/L). However, the observed plasma sodium concentration change after four hours (-1.8 mmol/L) was very different from the changes as predicted by the Adrogue-Madias (0.4 mmol/L) and the Nguyen-Kurtz formula (-0.9 mmol/L). Moreover, only 47% and 55%, respectively, of the expected sodium and potassium excretion were retrieved in the urine. Thus, healthy individuals are able to osmotically inactivate significant amounts of sodium after hypertonic saline infusion. Further research is needed to uncover factors that determine nonosmotic sodium storage.

The clinical epidemiology of BK virus (BKV) disease after allogeneic hematopoietic stem cell transplantation (HSCT) is not well defined. We evaluated 491 patients transplanted from January 2010 to December 2011 at a single transplant center to assess incidence, severity, and risk factors for BKV disease after HSCT. BKV disease was defined as BKV detection in urine by PCR testing in association with genitourinary symptoms without other concurrent genitourinary conditions. BKV disease occurred in 78 patients (15.9%), for an incidence rate of .47/1000 patient-days (95% confidence interval [CI], .37 to .59); BKV disease was considered severe in 27 patients (5.5%). In multivariate Cox modeling, time-dependent acute graft-versus-host disease (aGVHD) grades II to IV (adjusted hazard ratio [aHR] 4.25; 95% CI, 2.51 to 7.21), cord blood HSCT (aHR 2.28; 95% CI, 1.01 to 5.15), post-transplant mycophenolate use (aHR 3.31; 95% CI, 1.83 to 5.99), and high-dose cyclophosphamide conditioning (aHR 2.34, 95% CI 1.45 to 3.77) were significant predictors of BKV disease. Time-dependent aGVHD grades III to IV (aHR 10.5; 95% CI, 4.44 to 25.0) and cord blood HSCT (aHR 5.40; 95% CI, 1.94 to 15.0) were independent risk factors for severe BKV disease. BKV disease is common and is associated with significant and prolonged morbidity after HSCT. Prospective studies are needed to better define the morbidity of post-HSCT BKV disease and inform the design of prophylaxis and treatment trials.