Glomerular Diseases

Glomerular diseases are a group of disorders that directly affect the main filtering unit of the kidney, [Page 745]which is called the glomerulus. The glomeruli are groups of blood vessels in the body that clear extra fluid and waste substances from the body. The glomeruli are attached to a series of small tubes (tubules), which also contribute the filtration process by controlling sodium and water concentrations in the body. Glomerular diseases damage the glomeruli and cause leaking of protein and other cells. This leakage disturbs the fragile environment of the kidney and without this balance; it is harder for the body to rid of wastes and extra fluid.

There are two main groups of glomerular diseases: nephrotic syndromes and nephritic syndromes. Both of these syndromes affect the glomerulus in different ways and show different symptoms. Nephrotic syndrome has a more insidious onset and commonly occurs in association with systemic diseases that affecting multiple organs in the body. This includes illnesses like diabetes mellitus, systemic lupus erythematous, or amyloidosis. Nephritic syndrome has a quicker onset and occurs in association with infections of single organ systems. An example of this is a bacterium in untreated strep throat, which can damage the kidneys or a virus like chicken pox.

Proteinuria, protein in the urine, is the hallmark finding of glomerular disease. Normally, the glomerular wall sorts blood proteins based on the size and charge and blocks proteins that are too large or charged from entering the urinary tubules. With glomerular damage this sorting ability is hindered, so large and charged proteins are allowed into the urine. Proteinuria is present in both nephrotic and nephritic syndrome so to differentiate the amount of 3.5 grams/deciliter is the cutoff, above this level is considered nephrotic and below it is nephritic. Nephrotic syndrome also shows low levels or blood protein, which manifests as swelling in face and extremities that occurs gradually over time. Another sign of nephrotic syndrome is high levels of blood cholesterol and triglycerides, which can show as fatty casts in the urine.

Hematuria, blood in the urine, is a common finding in nephritic syndromes. Hematuria can be defined as gross, or visible to the naked eye, or microscopic, only seen by high-power microscopy. In nephrotic syndrome, hematuria is due to disturbance and damage to glomerular cells caused by inflammation. The presence of blood in the urine can also been seen by the presence of bloody casts in a urinary specimen. Other symptoms of nephritic syndrome include generalized aches and pains in joints and muscles, swelling in extremities and face, lethargy, blurry vision, and fatigue or malaise.