Urinary indices during relapse of childhood nephrotic syndrome

Abstract

Sodium retention is the hallmark of idiopathic nephrotic syndrome (INS). Sodium retention could be secondary to activation of renin–angiotensin–aldosterone axis or due to an intrinsic activation of Na+K+ ATPase in the cortical collecting duct. Urine potassium/urine potassium + urine sodium (UK+/UK+ + UNa+) is a surrogate marker for aldosterone activity and can be useful in differentiating primary sodium retention from secondary sodium retention in children with INS. This was a cross-sectional study of children with INS, presenting to our center from June 2007 to June 2008. Children were categorized into those with steroid responsive and steroid nonresponsive nephrotic syndrome. One hundred and thirty-four children with nephrotic syndrome were analyzed. The FeNa+ was significantly lower during relapse than in remission but no such difference was observed with UK+/UK+ + UNa+. The values of FeNa+ and UK+/UK+ + UNa+ across various categories of nephrotic syndrome were similar. Correlating FeNa+ and UK+/UK+ + UNa+ with cut-off of 0.5 and 60%, respectively, we found 50% of steroid responsive children and 36% of steroid nonresponders having a corresponding UK+/UK+ + UNa+ of <60% along with low FeNa+ of <0.5%, favoring primary sodium retention. Urinary indices did not vary with the type of steroid response. In early relapse, the urinary indices revealed an overlap of both primary and secondary sodium retention in most stable edematous children with nephrotic syndrome.

Hypo- and hypervolemic edema in children with steroidsensitive nephrotic syndrome

“…They also suggested that the main determinant of sodium reabsorption is the proximal tubule, as in previous studies. In the early phase of NS, urinary indices reveal an overlap of primary and secondary sodium retention (18). FENa alone cannot be used to differentiate between primary and secondary sodium retention.…”

“…However, in children with NS, strong positive correlations were found between U K /U Na+K ratio and plasma aldosterone (19). It can be useful in differentiating primary sodium retention from secondary sodium retention in NS patients (18).…”

Edema in Renal Diseases – Current View on Pathogenesis

“…Patients with NS and hypovolemia typically show low FENa+ (often below 0.2%) and a high urinary K + /K + +Na + index (greater than 60%) (8,(39)(40)(41)(42)(43). Management of edema in such patients demands correction of the intravascular volume with infusion of albumin ore non-protein colloids before initiation of diuretic therapy.…”

“…Patients with edema and clinical and/or laboratory features of hypervolemia (FENa+>1% and urinary K + /K + +Na + index <60%) can safely be treated with diuretics (8,(39)(40)(41)(42)(43). Intravascular infusion of albumin and colloids in such patients put them at risk of volume overload and lung edema.…”

Urinary indices in nephrotic syndrome

“…Volume-expanded patients may benefit with diuretics while volume-contracted patients need volume expansion. [ 1 ] Clinically it is not possible to differentiate severely edematous nephrotic syndrome (NS) patients with intravascular volume expansion (VE) from those with intravascular contraction (VC). [ 2 ] Hence urine indices may have some role in elucidating the volume status.…”