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Protein in Urine

When considering protein in the urine, it is be helpful to consider how the urinary system works.The kidneys, one on each side, sit high in the upper abdomen partially underneath the rib cage. They filter the blood to extract excess waste products and fluid to form the urine. Urine, once formed in the kidneys, travels through a tube on each side, the ureter, down to the bladder. There may be disorder within the kidney, which interferes with the filtering system, which results in protein slipping though the filter to end up in the urine.

The urinalysis is a study of voided urine. There are two parts to a urine study – the chemical dipstick and the microscopic examination of the urine. For the dipstick, a chemical strip with special reagents is dipped into a sample of voided urine. The reagents are able to assess for a variety of conditions in the urine, including the presence of red bloods cells (blood in the urine, also know as hematuria), protein, sugar, white cells (which can indicate infection) and substances that may indicate impaired liver function.

The microscopic portion of the urine study is carried out by inspecting a sample of urine under the microscope, which can allow the visual identification of red blood cells, white blood cells, bacteria and other elements.

When the dipstick text is positive for protein in the urine, there are several considerations. Sometimes, protein may be present only on a temporary basis, as can occur in the setting of fever, exercise and stress. In these cases, the protein may be present in the urine for a short period of time, but will not persist.

When protein is persistently present, and identified on several urinalysis over the course of time, further investigation is warranted. A 24-hour urine collection is carried out. All of the urine voided over a 24-hour period is collected, so that the total amount of protein excreted during the 24-hour period can be measured. The level of creatinine is typically measured also. Creatinine is a waste product that is cleared in the urine, and the measurement of it offers the opportunity to assess the overall level of kidney function.

In addition to a 24 hour urine collection, an assessment of the anatomic structure of the urinary system may be made with an imaging study, such as an ultrasound CT scan, which can show if there is anatomical abnormality within the urinary system such as growth, blockage or stone.

Blood tests to measure the level of BUN and creatinine may be done, which are another way to assess the overall level of kidney function.

When there is significant protein within the urine, the next step is evaluation by a nephrologist. Nephrologists are physicians who specialize in evaluation and treatment of the way the kidney functions, and they are different from urologists who are specialists that manage disorders related to the structure of the urinary system (such as growth, blockage or stone) that may require surgical intervention.

A nephrologist can carry out additional tests to determine the reason for impaired kidney function that has caused protein in the urine, and may make appropriate treatment recommendations.

The table below offers a guide to the correlation between dipstick test and the amount of protein may be present in a 24 hours urine collection.

Dipstick urinalysisAmount of protein in the urine
0Normal
1+30 mg/dL
2+100 mg/dL
3+300 mg/dL
4+1000 mg/dL
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