Hyponatremia is a marker of different underlying diseases and it can be a cause of morbidity itself; this implies the importance of a correct approach to the problem. The syndrome of inappropriate antidiuresis (SIAD) is one of the most common causes of hyponatremia: it is a disorder of sodium and water balance characterized by urinary dilution impairment and hypotonic hyponatremia, in the absence of renal disease or any identifiable non-osmotic stimulus able to induce antidiuretic hormone (ADH) release; according to its definition, it is diagnosed through an exclusion algorithm. SIAD is usually observed in hospitalized patients and its prevalence may be as high as 35%. The understanding of the syndrome has notably evolved over the last years, as reflected by the significant change in the name, once the syndrome of inappropriate secretion of ADH (SIADH), today SIAD. This review is up to date and it analyses the newest notions about pathophysiological mechanisms, classification, management and therapy of SIAD, including vaptans.

Pre-transplant donor biopsy (PTDB)-based marginal-donor allocation systems to single or dual renal transplantation could increase the use of organs with Kidney Donor Profile Index (KDPI) in the highest range (e.g. >80 or >90), whose discard rate approximates 50% in the US. To test this hypothesis, we retrospectively calculated the KDPI and analyzed the outcomes of 442 marginal kidney transplants (340 single transplants: 278 with a PTDB Remuzzi score <4 [median KDPI:87; interquartile range(IQR):78-94] and 62 with a score =4 [median KDPI:87; IQR:76-93]; 102 dual transplants [median KDPI: 93; IQR:86-96]) and 248 single standard transplant controls [median KDPI:36; IQR:18-51]. PTDB-based allocation of marginal grafts led to a limited discard rate of 15% for kidneys with KDPI of 80-90 and of 37% for kidneys with a KDPI of 91-100. Although 1-year eGFRs were significantly lower in recipients of marginal kidneys (-9.3, -17.9, and -18.8ml/min, for dual transplants, single kidneys with PTDB score <4, and =4, respectively; P<0.001), graft survival (median follow-up 3.3 years) was similar between marginal and standard kidney transplants (hazard ratio: 1.20 [95% confidence interval: 0.80 to 1.79; P=0.38]). In conclusion, PTDB-based allocation allows the safe transplantation of kidneys with KDPI in the highest range that may otherwise be discarded.

Pre-existing CKD, intra-arterial administration and CM volume are the most important risk factors for CI-AKI. Since risk factors for CI-AKI are well defined, and the timing of renal insult is known, patients should be carefully stratified before the administration of CM, in order to reduce the negative impact of modifiable risk factors on renal function. The intravenous administration of moderate amounts of isotonic saline solution or bicarbonate solution still represents the principal intervention with documented and acceptable effectiveness for CI-AKI prevention. More data are needed on aggressive volume expansion strategies along with diuretics, targeting forced diuresis with high urinary output. The role of antioxidant agents remains controversial, and only moderate evidence exists in favour of N-acetylcysteine. Statins could contribute to reducing the incidence of CI-AKI, although their mechanism of action is not fully ascertained. No robust data demonstrate a reduction of CI-AKI incidence by peri-procedural hemodialysis/hemofiltration; renal replacement therapies may carry instead unnecessary risks. Remote ischemic preconditioning might represent a simple, non-invasive and cost effective preventive measure for CI-AKI prevention, but few data are currently available about its clinical application in patients at high risk of CI-AKI.

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