What is postural proteinuria and what causes it?

Orthostatic proteinuria is proteinuria caused by changes in body activity. Generally, urine protein is negative when lying down, but positive when standing or walking upright. Why does this happen? What are the symptoms of orthostatic proteinuria?

1. Causes of postural proteinuria

When standing upright, the spine is lordotic, the liver rotates forward and downward, compressing the inferior vena cava, increasing the renal venous pressure, causing renal congestion, and increasing the hydrostatic pressure of the renal capillaries, resulting in proteinuria. The increase in renal blood flow leads to an increase in the total amount of protein flowing through the renal unit, which also increases the total amount of protein in the final urine. When the renal blood flow returns to normal, proteinuria disappears.

Common triggers include: cold, strenuous exercise, tension, sympathetic nerve excitement, and the use of vasoactive drugs.

2. Symptoms of postural proteinuria

① No history of kidney disease or clinical manifestations;

②No other systemic diseases related to kidney disease;

③No hypertension;

④No abnormal urine sediment;

⑤Normal kidney function;

⑥ Blood biochemistry and serology tests are normal;

⑦ Urinary tract X-ray examination is normal;

⑧24-hour urine protein is generally less than 1g, occasionally up to 2-3g, but the total amount of supine urine protein for 12 hours should be less than 75mg.