Nephrotic Syndrome I : Introduction

Nephrotic syndrome results from glomerular injury, particularly affecting podocytes—specialized cells lining the glomeruli. This damage increases the permeability of the glomerular filtration barrier, allowing large proteins like albumin to leak into the urine. The compromised barrier is the fundamental mechanism driving proteinuria and subsequent clinical manifestations of the syndrome.

Significant proteinuria causes hypoalbuminemia, reducing blood oncotic pressure. This pressure drop forces fluid to shift from the bloodstream into surrounding tissues, causing edema. Morning periorbital edema typically appears first around the eyes but can progress to generalized swelling called anasarca in severe cases.

In adults, focal segmental glomerulosclerosis is the most common primary cause. Secondary causes include diabetes mellitus, infections such as HIV and hepatitis B and C, and medications like NSAIDs. Understanding the underlying etiology is essential for determining appropriate syndrome assessment and medical management strategies.

The liver compensates for hypoalbuminemia by increasing lipoprotein synthesis, resulting in hyperlipidemia characterized by elevated cholesterol and triglycerides. This compensatory mechanism occurs as the body attempts to restore plasma proteins and maintain oncotic pressure despite ongoing protein loss through the urine.

Nephrotic syndrome typically presents with morning periorbital edema that may extend to the face, limbs, and abdomen. Additional signs include frothy urine from proteinuria, weight gain, fatigue, and reduced appetite. Severe cases develop generalized edema or anasarca, reflecting significant fluid accumulation from hypoalbuminemia.

Nephrotic syndrome weakens immune defenses through loss of immunoglobulin G in the urine, making infections more likely. Additionally, the loss of anticoagulant proteins increases the risk for thromboembolic events. These complications, combined with malnutrition from protein loss, significantly compromise patient health and require careful monitoring.

Proteinuria in nephrotic syndrome is defined as the loss of more than 3.5 grams of protein per day in adults. This severe protein loss, primarily albumin, results from increased glomerular permeability and is a crucial diagnostic feature. The resulting hypoalbuminemia triggers the cascade of fluid retention and metabolic complications characteristic of the syndrome.