Membranous Nephropathy
Patient Information from The Center for Glomerular Disease at Columbia University

 

Pictures of Deposits on Wall of the Filters


Membranous Nephropathy is a disorder that damages the filters (the glomeruli) of the kidney. It is one of the most common forms of glomerular diseases (glomerulonephritis) that results in leakage by the kidney of large amounts of protein into the urine (referred to as proteinuria). When very large amounts of protein are lost in the urine, it is often called the Nephrotic Syndrome.

The term “membranous” reflects how the kidney filters appear when looked at underneath a special high powered microscope. The walls of the filters appear thicker than normal due to the abnormal accumulation of immune deposits. The reason that these deposits accumulate is not known. Nevertheless, it causes the filters to be damaged and they are unable to properly perform their normal function of filtering the blood.

Membranous Nephropathy can develop as an isolated kidney disease. In these cases, the cause of the kidney disease is unknown. In some, the disorder may be associated with other diseases including autoimmune diseases (such as lupus), certain infections (such as Hepatitis B and C), rarely cancer and due to some medications.

Membranous Nephropathy affects patients of all ages but it is more frequently diagnosed in middle age (40-50
years old). Although it is more common amongst Caucasians, it occurs in all races.

Symptoms:

Some people with Membranous Nephropathy develop swelling (edema) of the eyelids in the morning, and of the legs late in the day. This is due to retention of salt and fluid and this is what leads them to seek medical attention. Some notice foamy or bubbly urine when they urinate due to the protein in the urine. In others, the urinary protein may first be discovered on a urine test (urinalysis) done by the doctor as part of the routine physical exam or as part of evaluation of another problem. Sometimes, blood tests reveal abnormal kidney function.

Diagnosis:

A kidney biopsy is done to establish the diagnosis of Membranous nephropathy and to distinguish it from other diseases that may also cause protein (and blood) losses in the urine. The doctor will usually order blood tests to look for evidence of infections or autoimmune disorders that may be associated with this kidney problem. Additional screening tests such as a chest x-ray and mammogram (in females) may also be recommended by your doctor.

Prognosis:

The natural history of membranous nephropathy varies a great deal. A percentage of individuals (approximately 30%) will improve completely without any treatment (spontaneous remission). Another 30 % with improve, but to a lesser extent, and show some decrease in urine protein losses (partial remission). Approximately 30% of individuals with continue to slowly lose kidney function over many years and may need to be on dialysis or require a kidney transplant.

It is difficult to predict with certainly how a particular person will do. However, there are certain factors that may help the doctor to determine which category an individual will likely be in. Knowing this information helps to guide treatment. For example, young females with lower levels of urine protein losses, normal kidney function (based on blood creatinine levels) and good blood pressure often do well without any specific treatment. These individuals may just need to be monitored by the nephrologists very closely to make sure that blood and urine tests continue to improve and the blood pressure remains under excellent control. On the other hand, males over the age of 50 with higher levels of urine protein losses, abnormal kidney function and poorly controlled blood pressure appear to be at higher risk for developing further kidney damage.

Treatment:

The decision to treat and the exact treatment regimen will, in part, depend on the risk factors present (as discussed above) and needs to be individualized. Some treatment is used to control the symptoms associated with the disease as well as slow down the progression of the disease. Diuretics (“water pills”) are used to rid the body of excess salt which causes the swelling (edema). Other medications are used to control the blood pressure, particularly a group of drugs called angiotensin converting enzyme inhibitors (ACE inhibitors) and angiotensin receptor blockers (ARBs). These same medications also help to decrease the amount of protein that is lost by the kidney. Other drugs (such as “statins) are often used to help reduce the high blood cholesterol. In most cases, a moderate protein diet is usually recommended.

In some individuals, if the amount of a specific protein (albumin) in the blood is very low, the doctor may recommend starting blood thinners such as warfarin. This is because low blood albumin may increase the risk of clots forming in the lungs, extremities or in the kidney. It is important to talk about the potential risks (such as easy bleeding) and benefits of this type of treatment with your doctor.

In those individuals at higher risk of developing progressive kidney damage or who have severe protein losses from the kidney, more specific treatment may be used to alter the immune system and to try to cure the disease. There are several treatments available. The physicians at the Glomerular Center at Columbia University are very interested in determining which treatments are best for people with Membranous nephropathy and have the least side effects (toxicity). Steroids (such as prednisone) are often tried for several months, usually given in combination with other immunosuppression drugs including cyclosporine (which is a medication frequently used after transplants) or cyclophosphamide (cytoxan). Mycophenolate mofetil (MMF) has also been used. We have also had success using a new intravenous medication called Rituximab (rituxan). Each of these treatments have different side effects associated with them which should be discussed with your nephrologist. All can increase the risk of infections and this too must be discussed with the physicians caring for individuals with membranous nephropathy.