Diagnosis of Proteinuria
Proteinuria and microalbuminuria are diagnosed by measuring the amount of protein excreted in the urine in a 24-hour period. Collecting urine for 24 hours can be difficult, so the physician often uses a spot urine test in which one sample of urine is analyzed. Healthy kidneys continually remove creatinine from the blood to maintain a stasis between blood levels and urine levels. The ratio of protein to creatinine in the urine can provide the physician with a good idea of how much protein is being excreted over 24 hours.
Albumin can be measured in the urine at relatively low amounts, which allows the physician to diagnose patients with early glomerular damage.
In people without diabetes, more than 1000 mg of protein in the urine in a 24-hour collection may warrant blood analysis and, possibly, a kidney biopsy.
It is necessary to treat the underlying condition that is causing proteinuria. For example, when diabetes or hypertension is present, treatment involves controlling blood pressure with the use of an angiotensin-converting enzyme (ACE-I) inhibitor, like captopril (capoten®). Ace inhibitors prevent the conversion of angiotensin I to angiotensin II, a substance that normally causes the veins to constrict. The result is a reduction in blood pressure.
The goal is to reduce blood pressure below 130 systolic and 80 diastolic. After bun, creatinine, and potassium are monitored for 7 to 10 days, ace inhibitors are gradually increased to avoid side effects. The degree of proteinuria is checked periodically and typically improves with every dose.
It is necessary to monitor blood sugar, salt intake, diet, and exercise.
Medication Side Effects
Dry cough develops in 3% to 5% of people who take ACE-I inhibitors. Patients may switch to new blood pressure medications known as angiotensin receptor blockers (ARB), which have effects similar to ACE-I inhibitors and are not associated with cough.
ACE inhibitors should not be discontinued abruptly; dosage is reduced gradually over a long period of time.
Dietary regulation of salt and protein is beneficial to some people with proteinuria. Many physicians recommend seeing a nutritionist to help determine a proper diet for their patients.