Rippe Bengt, Venturoli Daniele
Department of Nephrology, University Hospital of Lund, S-211 85 Lund, Sweden.
Am J Physiol Renal Physiol. 2007 Mar;292(3):F1035-43. doi: 10.1152/ajprenal.00251.2006. Epub 2006 Nov 7.
Ultrafiltration failure (UFF) is a common complication of long-term peritoneal dialysis (PD). Functionally UFF is in most cases characterized by an enhanced peritoneal mass transfer area coefficient for glucose (PS(g)) combined with a largely unchanged peritoneal glucose osmotic conductance (L(p)Ssigma(g)). Morphologically, marked UFF occurs with fibrosis of the submesothelial zone in the peritoneum, combined with vasculopathy and vascular proliferation in deeper tissues. To computer simulate UFF, changes both in the vasculature and in the interstitium have to be taken into account. For that purpose, we used a three-pore membrane/fiber matrix serial barrier model, applying the three-pore model to the capillaries and the fiber-matrix model to the interstitium. The parameters of the three-pore model have been published previously. The interstitial fiber density was set at 0.5% (vol/vol) and the fiber radius (r(f)) at 6 A during control. If the interstitial fiber density was increased from 0.5 to 3%, and r(f) to 7.5 A (cf. collagen) while the capillary surface area was increased by 40% from control, then PS(g) increased from 9.3 to 11.5 ml/min, while the UF coefficient (L(p)S) was largely unchanged. Further increases in vascular surface area combined with further increases in fiber density caused further increments in PS(g), whereas L(p)S remained unchanged. It is concluded that a matrix of fibers coupled in series with a three-pore membrane may be used for simulating the pathophysiological alterations occurring in the peritoneum in UFF, explaining the commonly observed "uncoupling" of small solute transport (PS) from the peritoneal UF coefficient (L(p)S) in this condition.
超滤失败（UFF）是长期腹膜透析（PD）的常见并发症。在功能上，UFF在大多数情况下的特征是葡萄糖的腹膜质量传递面积系数（PS(g)）增加，而腹膜葡萄糖渗透传导率（L(p)Sσ(g)）基本不变。在形态学上，明显的UFF表现为腹膜间皮下层纤维化，同时伴有更深层组织的血管病变和血管增生。为了通过计算机模拟UFF，必须考虑血管系统和间质的变化。为此，我们使用了三孔膜/纤维基质串联屏障模型，将三孔模型应用于毛细血管，将纤维基质模型应用于间质。三孔模型的参数此前已发表。在对照期间，间质纤维密度设定为0.5%（体积/体积），纤维半径（r(f)）设定为6埃。如果间质纤维密度从0.5%增加到3%，r(f)增加到7.5埃（参照胶原蛋白），同时毛细血管表面积比对照增加40%，那么PS(g)从9.3增加到11.5毫升/分钟，而超滤系数（L(p)S）基本不变。血管表面积的进一步增加与纤维密度的进一步增加导致PS(g)进一步升高，而L(p)S保持不变。得出的结论是，与三孔膜串联的纤维基质可用于模拟UFF时腹膜发生的病理生理改变，解释在这种情况下小溶质转运（PS）与腹膜超滤系数（L(p)S）常见的“解偶联”现象。
