Renal oedema usually accumulate in dependent part,as after long time sleeping, it

accumulates in the eyelids(in the loose CT) after awakening in the morning, again it also accumulates around the ankle after long standing and around sacrum after lying prolong time.

In patients with congestive cardiac failure, orthopnea prevents patients lying supine and the headrest is often elevated, preventing periorbital edema since the head is not the dependent area. However, nephrotic syndrome patients do not have orthopnea and can therefore ly supine without the need to elevate the head.

The reason for palpebral edema in nephrotic syndrome in the morning has two causes: the position of the head with nighttime rest and the laxitus of the eyelid tissue that makes it easier to accumulate fluid at that level

Although salt and water retention due to renin-angiotensin-aldosterone system (RAAS) derangement explains all transudative edemas, the exact reason why children with nephrotic syndrome develop edema mainly under lower eyelids is not exactly known.

If it is laxity of the tissues, this is present even in the upper eyelids and may explain the edema in angioedema during anaphylactic reactions involving both upper and lower eyelids. Why it occurs with nephrotic syndrome mainly in children and not in adults is also intriguing?

If nighttime rest causes palpebral edema in children, why such edema does not develop in children with cirrhosis liver or heart failure is an enigma.