December 19, 1999
Question from Georgia, USA:
My daughter, age 11, has had Type 1 for 4 years. Her annual urinalysis had trace protein and a microalbumin of 100, so her physician ordered a 24 hour urine for protein and microalbumin. While waiting for the results to come back, I'm searching for reasons why she should be showing signs of nephropathy so early. Her blood glucose control has never been ideal (HgbA1c average 7.6-7.9), but not terrible either. What other conditions could be causing these signs of kidney damage?
Answering your question involves a small digression into the history of microalbumin measurements. About twenty years ago physicians began to be concerned about the early detection and management of the vascular complications of diabetes. At that time this consisted for the most part of retinal examination and the careful measurement of resting blood pressures. It then became evident that early intervention in the treatment of high blood pressure, especially with a group of drugs called ACE inhibitors, was beneficial. Many of these patients with high blood pressure were also noted to have small amounts of albumin in the urine, amounts less than could be detected by the usual dipsticks. In time it was realised that the microalbumin was also important prognostically and that it could also be successfully treated with ACE inhibitors in the absence of coexisting hypertension.
True microalbuminuria in an 11 year old diabetic would be very uncommon indeed and her doctor is absolutely right to start by confirming this. Normally an eight hour overnight specimen is sufficient where the normals are <7.6 mcg/min, 7.7 -20 mcg/min borderline and >20 mcg/min abnormal. These figures are for adults and would need to be adjusted on a weight or surface area basis for an 11 year old. Even if the figures are abnormal they would at this age with a history of really rather good control not necessarily represent diabetic nephropathy. It would be much more likely that this in fact represents a different process, subclinical glomerulonephropathy that may have taken place years ago. The only way to solve this would be to do a renal biopsy and in one or two Centers (e.g. Minneapolis), that is what they do. My own inclination would be to make very sure that there is absolutely no evidence of a urinary tract infection, something that can be quite silent, to watch carefully and try for meticulous control, but not to do a biopsy or to use ACE inhibitors for now. That decision is of course up to you and her doctor.
Additional comments by Dr. Tessa G. Lebinger
Small amounts of protein excreted in the daytime only are common in children (with or without diabetes) and do not necessarily represent kidney problems. That is why an overnight urine collection as suggested by Dr. O’Brien or even a first morning urine might be more accurate.
In addition to ruling out a urine infection which could cause transient increase in protein, I have also found that vaginal yeast infections (which are very common in girls with diabetes) can cause a temporary increase in protein in the urine unrelated to kidney disease. I usually suggest that if there is any question of a yeast infection, that a topical antifungal cream be used for a week, then a first morning urine collected after a bath (as normal external excretions can also contaminate the collection). I have “cured” many a patient collecting the urine specimen in this fashion.