Interstitial fluid colloid osmotic and hydrostatic pressures in subcutaneous tissue of patients with nephrotic syndrome.

Colloid osmotic pressure in plasma (IIp) and in interstitial fluid from subcutaneous tissue (IIi) was measured in 13 patients with nephrotic syndrome and in 20 healthy volunteers. Interstitial fluid was sampled by nylon wicks, and interstitial fluid pressure was measured by the 'wick-in-needle' technique. In the persons with normal plasma proteins we found a mean IIp of 26.9 mmHg, a mean IIi of 15.8 mmHg on the thorax, and a mean IIi of 11.1 mmHg on the lower leg. A fall of IIp from normal values to 16.5 mmHg caused a fall in IIi of about 8 mmHg on the thorax and about 7 mmHg on the leg without oedema formation. In patients with IIp from 16.0 mmHg down to 8.0 mmHg, IIi did not change very much, and was about 5.5 mmHg on the thorax and 2.6 mmHg on the leg. These results support the view that reduction of IIi plays an important role as an oedema preventing factor in patients with hypoproteinaemia.