Nephrotic syndrome is a set of symptoms characterized by proteinuria, hypoalbuminemia, hyperlipidemia, and edema. There are also several other symptoms that are reported by patients that result from these primary changes in the blood and urine. The main symptoms of the syndrome will be covered in more detail below.
Proteinuria refers to the presence of protein in the urine. In healthy individuals, protein molecules are too large to pass through the glomerulus and be excreted in the urine. For patients with nephrotic syndrome, protein is able to pass through and is present in the urine, giving it a foamy appearance.
In adults, proteinuria is classified as more that 3.5g/17.73m2 surface area of the body per day. In children, it is classified as more than 40mg/m2 surface area of the body per hour.
Lipiduria, which involves the presence of lipids in the urine, can also affect patients with nephrotic syndrome.
Hypoalbuminemia, or low concentration of albumin protein in the blood, is classified as less than 2.5g/dl. This occurs due to the increased quantity of protein that passes into the kidney through the glomerulus to be excreted in the urine. It is also associated with causing other symptoms of the condition, such as edema.
Other changes evident in the blood may include hyponatremia, or low levels of sodium.
Severe changes in the levels of protein and electrolytes in the blood have the potential to disrupt the function of the brain and may cause seizures, in rare cases.
Hyperlipidemia involves high levels of cholesterol and triglycerides in the blood in respect to normalized levels. In patients with nephrotic syndrome, this occurs due to two main reasons:
- Low levels of protein in the blood stimulate the synthesis of protein in the liver, leading to increased production of lipoproteins.
- Decreased catabolism of lipids due to reduced concentration of lipoprotein lipase in the blood, which is a primary enzyme involved in this process
Edema usually first becomes evident in the face and may also affect other areas of the body, such as the legs and the arms. It occurs due to excess fluid in the body, which is linked to low levels of protein in the blood.
Patients with hypoalbuminemia have lower serum oncotic pressure, leading to the accumulation of fluid in the interstitial tissue around the body. Edema can affect many areas of the body, including:
- Eyes: puffiness around the eyes, most prominentin the morning.
- Legs: swelling in the legs and retains the indentation when pressure is applied to a small area (pitting edema).
- Pleural cavity: effusion in the pleural cavity.
- Peritoneal cavity: fluid in the cavity leading to ascites.
Anasarca is the general term used to describe the accumulation of fluid throughout the body.
There are various other symptoms that may be associated with some cases of nephrotic syndrome. These may include:
- Excess fluid in the body
- Dyspnea (shortness of breath)
- Poor appetite
- Frothy urine
- Unintentional weight gain
Most of these symptoms are linked to one of the main signs and symptoms highlighted in the above section. Increased levels of protein in the urine and lack of protein in the blood can have a significant impact on the function of many areas of the body.