Introduction

Orthostatic proteinuria (OP), or postural proteinuria, is a medical condition characterised by excessive protein excreted in the urine when the patient is upright but not when they are lying down. This condition is commonly found in 2 to 5% of adolescents and is rare after age 30 and is more prevalent in people assigned male at birth (AMAB).^1,2

Research studies have thus far produced conflicting results regarding whether children who are obese or underweight are more prone to this condition. It is a benign condition that does not require any medical treatment. However, it is crucial to accurately diagnose OP to prevent unnecessary procedures, such as a renal biopsy, from being performed.

Therefore, it is important to seek medical attention if you suspect that you or someone you know might be experiencing OP. This article aims to go over what orthostatic proteinuria is and what symptoms to look out for.^1,2

Causes and mechanisms

OP  is a condition that causes uncertainty among healthcare providers and medical researchers about its specific causes. However, it is believed that the condition is closely related to renal conditions that may include:³

Kidney filter changes

Inside your kidneys, tiny filters called glomeruli clean your blood. In some people with OP, these filters might be slightly thicker than usual, affecting how well they work when you're not lying down.

Blood flow problems

A system in your body called the renin-angiotensin-aldosterone system (RAAS) helps control blood flow. If something goes wrong with this system, it might cause changes in blood flow to the kidneys, which could affect how proteins are handled.

Nutcracker syndrome

This is a condition in which the vein that drains blood from your left kidney can get squished, causing more pressure. This increased pressure might cause more protein to pass through the kidney filters when you're standing up.⁴

Gravity's role

Gravity can stress your kidneys when you stand or sit for a long time. This stress might cause them to leak protein into the urine, especially in people with OP.

These factors suggest that changes in kidney structure, blood flow, and the effects of gravity might play a role in OP. Doctors are still studying this condition to learn more and find better ways to treat it.

Symptoms and diagnosis 

OP can only be diagnosed through a urine test to measure protein levels. It is imperative to note that this condition shows no visible symptoms, and therefore, doctors must use specific tests to confirm the diagnosis.^1,4

Urine test

Urine test involves the doctors collecting your first-morning urine sample and checking for protein levels. If the protein is normal (less than 150 mg/day) and you don't have other symptoms, it's likely OP, and further tests for kidney disease may not be needed.

Urine protein-to-creatinine ratio

This test compares protein and creatinine levels in your urine. If the ratio is low when lying down (less than 0.2 mg/mg creatinine) but increases significantly when standing, it supports the diagnosis of OP.

Doppler sonography

Doppler sonography can be used to examine the blood flow in the veins of the kidneys in children with OP. By measuring the speed of blood flow and the size of veins, doctors check for signs of nutcracker syndrome. Thus, the primary aim of this simple, non-invasive test is to figure out if nutcracker syndrome is contributing to OP.⁴

Doctor's evaluation

Your doctor will ask about any symptoms, such as blood in your urine, high blood pressure, or kidney problems, which could suggest a different kidney condition.

When are more tests needed?

Generally, you likely won't need further tests if you only have OP and no other concerning symptoms. However, if there are signs of kidney issues like persistent blood in urine, high blood pressure, or kidney function problems, your doctor might consider more tests like a kidney biopsy to check for underlying problems.

Risk factors and associations

Activities involving prolonged standing or sitting, such as standing at work or sitting for long hours during a long-haul flight, may contribute to OP development.⁶ Additionally, family history and certain underlying health conditions, such as hypertension and diabetes, can increase the likelihood of OP.¹

Although OP is generally considered a benign condition, it is important to rule out potentially more serious kidney diseases. Therefore, it is recommended that patients undergo regular monitoring and follow-up care with a healthcare provider. This can help detect any changes in the condition and guide appropriate management if necessary. Moreover, early detection of kidney diseases is key to managing them effectively.

Orthostatic proteinuria in school-going children

A recent study has shown that this condition is rare, typically harmless, and often resolves independently over time.⁵

Researchers conducted a study involving 1,701 school-going children aged between 6 and 15. The results revealed that less than 1% of the participants were diagnosed with OP, and the condition was usually temporary, resolving independently without needing any special treatment.⁵

The study found no significant link between OP and factors such as age, weight, or gender. However, researchers found that it was slightly more common in underweight children than in overweight or obese children. However, further research is needed.⁵

Management and treatment 

OP is a harmless condition that can be detected in the urine when standing or sitting upright but not when lying down. It is commonly seen in children and adolescents and should not cause undue alarm. Here are some effective ways to manage it:¹

Regular monitoring

Your healthcare provider will recommend periodic urine tests, such as yearly check-ups, to monitor protein levels in the urine. Regular monitoring helps to track the stability of the condition over time.

Healthy lifestyle practices

Maintaining a balanced diet with nutritious foods and engaging in regular physical activity is part of a healthy lifestyle. However, there are usually no specific dietary restrictions associated with OP.

Education and reassurance

Educate yourself and your family about OP to understand that it's a benign condition and does not indicate kidney disease or require treatment. This knowledge can provide reassurance and reduce anxiety.

Follow-up visits

Attend follow-up appointments with your healthcare provider as recommended. This allows for ongoing assessment of protein levels and overall kidney health.

Treatment approach 

OP typically does not require medications or medical interventions. The condition often resolves on its own as you grow older.

Prognosis and outlook

If you have OP, please know that you're not alone. You can expect a positive long-term outlook. While persistent minor proteinuria is common, it doesn't typically lead to complications like high blood pressure or kidney problems. With regular check-ups and keeping in touch with your healthcare provider, you can effectively manage OP and maintain good kidney health.²

FAQs

How do you treat orthostatic proteinuria?

OP is a benign condition that doesn't require treatment. Modifying your diet or limiting physical activities is not necessary. Nevertheless, it's crucial to keep track of your protein levels if you or your child has this condition. Your healthcare provider may recommend a yearly urine test to control everything and prevent complications. So, make sure to stay vigilant and follow your healthcare provider's recommendations.

Who is affected by orthostatic proteinuria?

OP is commonly seen in children, adolescents, and young adults. It may occur more frequently during periods of rapid growth and development.

Summary 

OP is a medical condition where a person experiences protein in their urine only when they are standing up. Further research is necessary to understand better why this condition occurs and whether any other factors are involved. While the condition can be concerning for people, it is important to note that it is typically not a serious health issue and resolves independently over time.

In fact, there are no long-term complications associated with this condition. Therefore, people can be reassured that they can lead a healthy and normal life even with orthostatic proteinuria. However, monitoring the condition and seeking medical advice if any further changes occur is still important.