Exercise-Induced Proteinuria

Exercise-induced proteinuria is the release of proteins in an athlete’s urine. Although it was studied decades ago, it’s still being investigated. Find out more in this article!

When protein concentration in the urine of an athlete increases, we’re dealing with a case of exercise-induced proteinuria. This is a temporary and transitory condition that experts discovered more than a century ago. What should you know about it?

The protein in the athlete’s urine disappears after a day or two, and the effect is benign. In general, it doesn’t cause complications or significant kidney disorders.

The first cases of exercise-induced proteinuria were recorded in 1878. It wasn’t found in athletes but in a group of soldiers who were analyzed during a training day. Soon after, the scientific investigations continued, as it wasn’t clear if there was kidney damage or not.

The hypotheses varied in history. While some doctors attributed exercise-induced proteinuria to trauma, others believed that blood pressure changes cause it. To this day, the accurate origin is still unclear.

Why does exercise-induced proteinuria appear?

Exercise causes its own metabolism and hemodynamic modifications. Those non-durable changes include the onset of exercise-induced proteinuria.

Strictly speaking, the protein that’s detected in the urine of athletes doesn’t differ from that found in some kidney patients. This doesn’t mean that the phenomenon is pathological among athletes, but rather that the released substances are the same.

When you exercise intensely, blood flow changes direction to distribute itself to the areas of your body that need it the most. Instead of regularly supplying all the organs, muscle irrigation is increased during exercise, which leads to the reduction of urine volume, according to a study published by Biology of Sport.

The lower amount of blood to filter in the renal glomeruli alters the renin-angiotensin system, which plays a role in blood pressure. Furthermore, sports stimulate the activity of the sympathetic nervous system, mediated by norepinephrine.

In short, there’s less urine volume, with higher local blood pressure and a sympathetic effect. This translates into a renal funnel, through which the proteins make an effort to pass through the filter and out.

The effect is almost immediate. It begins 30 minutes after a person starts exercising. The intensity of sports is more determining than the duration. Thus, experts assume that sports such as boxing or soccer are more likely to cause exercise-induced proteinuria than others.

The role of cylindruria

Cylindruria is a special type of exercise-induced proteinuria. The mucoproteins can leak through the kidney filter and appear in the urine of athletes. Another more technical name they receive is the Tamm-Horsfall mucoprotein.

In particular, marathoners and runners are more likely to suffer from cylindruria among athletes. This is because they stop their urinary flow for prolonged times, which would force certain proteins to pass through the kidney filter.

In addition, dehydration is another trigger factor, which is why it’s associated with marathoners who don’t plan their fluid replacement correctly. However, these cylinders themselves aren’t a risk but a sign of other internal modifications.

Sports trauma and exercise-induced proteinuria

The first hypothesis of sports traumas that lead to exercise-induced proteinuria shouldn’t be left out. We should remember that this effect is most common in boxing.

It’s common for the proteinuria of athletes exposed to trauma to be accompanied by hematuria. In other words, blood in the urine. Experts have come to talk about “athlete’s kidney” when they detect both findings in a urine test.

This condition doesn’t cause pain and the blood medical professionals detect is microscopic. Thus, the person only sees a darkening of urine and nothing else. Also, there are no changes in the volume of urine.

If the athlete has congenital disorders in the renal route, it’ll be more likely for them to present proteinuria due to trauma. However, this isn’t linked to permanent organ damage. Similarly to the proteinuria, we’ve been talking about, the findings are usually temporary and benign.

Do I have to worry if I have exercise-induced proteinuria?

If a medical professional detected protein in your urine after exercising and they monitor you again after 48 hours and you don’t have that proteinuria, then there’s no need to worry. Perhaps you should review the hydration plan for your sport, nothing more.

On the other hand, if proteinuria is persistent, doesn’t disappear, or increases its concentration as the days pass, the doctor will request new tests. Your doctor will have to find a cause, which is likely unrelated to sports.