Glossary of Kidney Diseases


RPGN RPGN is usually classified as types 1, 2 and 3. Under each type there are specific diseases and the idiopathic form.

For example, patients with type 2 RPGN can have a specific diagnosis such as IgA disease, lupus or MPGN (any of the 3 types of MPGN!). If the biopsy shows type 2 RPGN but the patient doesn't have IgA, lupus, MPGN or another specific cause of type 2 RPGN then it would be called "idiopathic" type 2 RPGN. Remember that most patients with IgA, lupus and MPGN don't have RPGN. Rather, they have a less aggressive form of the disease. So your daughter had type II RPGN due to type II MPGN.

Idiopathic really means that we don't know what causes the disease. Some people with MPGN have it due to a specific disease (such as an infection) and thus it is not idiopathic MPGN. Most MPGN in American children is idiopathic. Thus your daughter's RPGN was not idiopathic since it was due to MPGN. However, her MPGN was idiopathic since it wasn't due to a specific cause. (L.G.)

Chronic Renal Insufficiency (CRI) CRI just stands for chronic renal insufficiency, which means mildly to moderately decreased renal function--I usually use it for kidney function between 50 and 80% of normal (80% of normal is normal, if that makes any sense), and then CRF (chronic renal failure) is renal function below 50%--some say that the cut off between the two is 40%--I don't know of any hard and fast rule. CRI and CRF only indicate the amount of renal dysfunction--and just the filtration part of function, with no distinction of how the function got low. (S.C)
Posterior Urethral Valves (PUV) No one knows why posterior urethral valves happen--it happens in the first
trimester and is a sporadic defect--not familial. It has not been
associated with any drugs mother took or anything she did. (S.C.)
Renal Tubular Acidosis Renal tubular acidosis is a condition or disease in which the kidney does not take acid out of blood and put it into urine like it should.  Protein is broken down to yield energy and amino acids, and the amino acids are used to make new proteins.  Acid is generated as a waste product in this process, and the part of the kidney called the tubule takes the hydrogen ions, the acid molecules, out of the blood and puts them into the tubular fluid, which ultimately becomes urine. The kidney defect is limited to this, although along with it comes some decrease in the ability to concentrate the urine, meaning the ability to put a large amount of waste products into a small amount of urine.  This ability is crucial in times of decreased fluid intake, or during increased fluid losses, like during episodes of diarrhea and vomiting.  So the child with RTA becomes more easily dehydrated under these circumstances.  Sometimes parents or doctors will be fooled about the dehydration, because lack of urinary concentrating ability means that the child keeps urinating fairly frequently.  Frequency and amount of urination cannot be used as a marker of hydration.