Diagnosis of this disease is essentially how the disease gets its name. The third layer of the glomeruli, the podocytes, are visible under a regular standard light microscope, but it is nearly impossible to see detail and the way that the foot processes fit together. So under this microscope, all elements are seen and the glomerulus shows minimal change.
Glomerulus under a light microscope
However, if the same cells are put underneath an electron microscope,
which will magnify cells to one million times their normal size, you can
see the podocytes and their foot processes clearly. It is very easy to
see the way that they should uniformly fit together to form filtration
slits..and as shown below, and the way that they look when they don't.
Normal glomerulus under an electron microscope
A - close up of normal foot processes under electron microscope
B - close up of fused, raised and thinned foot processes under electron microscope
So once the symptoms start occuring the biopsy is taken and viewed and the abnormal podocyte fusion is discovered. At this point, all symptoms can be attributed to MCD. It is important to state here that MCD can be put into remission fairly easily once it is discovered.
However, biopsying a kidney is a fairly invasive procedure, so researchers are currently working on different methods of diagnosing MCD including the presence of certain proteins in urine, specifically transmembrane proteins that are present in large numbers in podocytes and low molecular weight proteins. However, these diagnosis techniques are still in the early stage of research and kidney biopsy is currently the best way to make a certain diagnosis.
References:
http://link.springer.com.offcampus.lib.washington.edu/article/10.1007/s00467-014-2915-3/fulltext.html
http://europepmc.org/abstract/med/10878397
