Methods for Estimation of Peritoneal Dialysate Volume and Reabsorption Rate Using Macromolecular Markers

Reabsorption of fluid and solutes from the peritoneal cavity poses several problems for the correct estimation of peritoneal dialysate volume and ultrafiltration rate with macromolecular volume markers. Although physiological mechanisms of peritoneal reabsorption (direct lymphatic absorption vs reabsorption to the peritoneal tissue) are being currently discussed, many experimental and clinical studies have demonstrated that peritoneal reabsorption of the marker is mainly a bulk “backflow” out of the peritoneal cavity. Theoretical bases for the estimation of peritoneal dialysate volume and cumulative ultrafiltration of fluid including the correction for peritoneal reabsorption are reviewed. A widely applied simplified method which, however, neglects the impact of ultrafiltration on marker concentration is also discussed. The systematic errors involved in the application of the simplified method are usually less than 10% in the standard conditions; however, in specific cases they may be much higher. Therefore, the correct method is suggested for practical applications.

Factors Affecting Lymphatic Absorption in Chinese Patients on Continuous Ambulatory Peritoneal Dialysis (CAPD)

The pathways and physiology of lymph absorption (LA) from the peritoneal cavity are well documented; however, much uncertainty still exists as to the various clinical and demographic factors affecting LA. We studied LA measured by the albumin instillation method, in adult Chinese CAPD patients, and showed that it was independent of age, sex, body surface area, duration of dialysis, intrinsic renal disease, use of intraperitoneal drugs (heparin/antibiotics/deferroxamine) and frequency of past bacterial peritonitis. High lymph absorbers had a relatively highertranscapillary cumulative ultrafiltration than low lymph absorbers. An enhanced LA was associated with a high initial intraperitoneal volume. Assessment of diaphragmatic strength by the decrement in vital capacity on changing from an erect to a supine position failed to distinguish patients with high and low LA.