Ultrafiltration Failure (UFF)

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UFF is the inability to achieve adequate fluid balance.  It is defined based on the net UF obtained after a standard dialysis dwell.  The expected amount of UF varies depending on the glucose concentration of the PDF used.  A glucose concentration of 4.25% is recommended for identification of this complication due to the frequent overestimation when lower concentrations are used.  A diagnosis of UFF is made when net UF < 100 ml after a 4-hour dwell with 2.5% glucose PDF or < 400 ml with 4.25% glucose PDF, in the absence of catheter malfunction, fluid leaks or extensive intraperitoneal adhesions^1-4. 

There are three types of UFF:

• Type I membrane failure – associated with rapid solute transport
• Type II membrane failure – associated with impaired solute transport
• Type III membrane failure – associated with excessive lymphatic absorption

Type I membrane failure is the most common cause of UFF.  The increased transport of low molecular weight solutes and rapid glucose absorption with loss of the osmotic gradient is due to increased effective peritoneal surface area through vascular neoproliferation or increased vascular permeability.  Another proposed mechanism is impaired aquaporin mediated water transport⁵.  The prevalence of UFF increases with time on PD and may be the result of increased reactive carbonyl compounds (RCOs) and glucose derived substances⁶ related to the use of conventional PDF.  Type I UFF also occurs during peritonitis.  In contrast to chronic UF failure, the large pore size is also increased during peritonitis, resulting in an increased loss of proteins, possibly related to the release of inflammatory mediators^7,8.  The loss of UF during peritonitis is usually reversible. 

Type II membrane failure is relatively rare and mostly seen in patients with peritoneal sclerosis.  Although solute transport is frequently intact, the peritoneal surface area reduction due to extensive adhesions or fibrosis can result in an overall decrease in fluid and solute removal.

Increased resorption of dialysate from the peritoneal cavity due to increased lymphatic flow is an important factor in type III membrane failure.  Mechanical problems (leaks and catheter dysfunction) are part of the differential diagnosis of low UF and normal membrane function.

Treatment of UFF mostly depends on the type of membrane failure.  In the case of increased solute transport the mainstay of therapy is shortening the dwell time and providing more frequent exchanges.  The elimination of the long dwell exchanges of CAPD or CCPD are highly recommended.  Temporary discontinuation of PD to allow a rest period has been reported to restore membrane function^9,10.  The use of intraperitoneal heparin has also been reported to reduce peritoneal permeability and to increase UF¹¹.  If reduced lymphatic absorption is suspected, avoiding large dialysate volumes may be beneficial.  The therapeutic recommendations for sclerosing peritonitis are less clear and the prognosis significantly worse (see Peritoneal Sclerosis).

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References:

1. Twardowski ZJ, Nolph KD, Khanna R, Prowant BF, Ryan LP, Moore HL, Nielsen MP. Peritoneal equilibration test. Perit Dial Bull 7:138-147, 1987
2. Davies SJ, Brown B, Bryan J, Russell GI. Clinical evaluation of the peritoneal equilibration test: A population-based study. Nephrol Dial Transplant 8:64-70, 1993
3. Ho-dac-Pannekeet MM, Atasever B, Struijk DG, Krediet RT. Analysis of ultrafiltration failure in peritoneal dialysis patients by means of standard peritoneal permeability analysis.  Perit Dial Int 17:144-150, 1997
4. Krediet RT, Imholz AL, Struijk DG, Koomen GC, Arisz L. Ultrafiltration failure in continuous ambulatory peritoneal dialysis. Perit Dial Int 13 (Suppl 2)S59-S66, 1992
5. Monquil MC, Imholz AL, Struijk DG, Krediet RT. Does impaired transcellular water transport contribute to net ultrafiltration failure during CAPD? Perit Dial Int 15:42-48, 1995
6. Buemi M, Aloisi C, Cutroneo G, Nostro L, Favaloro A: Flowing time on the peritoneal membrane. Nephrol Dial Transplant 19:26-29, 2004
7. Krediet RT, Zuyderhoudt FM, Boeschoten EW, Arisz L. Alterations in the peritoneal transport of water and solutes during peritonitis in continuous ambulatory peritoneal dialysis patients. Eur J Clin Invest 17:43-52, 1987
8. Panasik E, Pietzak B. Characteristics of peritoneum after peritonitis in CAPD patients.  Adv Perit Dial 4:42-43, 1988
9. Rodrigues A, Cabrita A, Maia P, Guimaraes S. Peritoneal rest may successfully recover ultrafiltration in patients who develop peritoneal hyperpermeability with time on continuous ambulatory peritoneal dialysis. Adv Perit Dial 18, 78-80, 2002 
10. Zareie M, Keuning ED, ter Wee PM, Beelen RH, van den BJ: Peritoneal dialysis fluid-induced changes of the peritoneal membrane are reversible after peritoneal rest in rats. Nephrol Dial Transplant 20:189-193, 2005
11. Sjoland JA, Pedersen RS, Jespersen J, Gram J. Intraperitoneal heparin reduces peritoneal permeability and increases ultrafiltration in peritoneal dialysis patients.  Nephrol Dial Transplant 19:1264-1268, 2004