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Bench Sciences |
Department of Biophysics and Nuclear Medicine1 and Nephrology Dialysis Transplantation Children's Unit,2 University Hospital; INSERM Unit 727,3 University Louis Pasteur Medical School, Strasbourg, France; Department of Nephrology and Physiology,4 Sahlgrenska University Hospital, Gothenburg, Sweden
Correspondence to: M. Fischbach, Nephrology Dialysis Transplantation Children's Unit, Hôpital de Hautepierre, Avenue Molière, 67098 Strasbourg Cedex, France. michel.fischbach{at}chru-strasbourg.fr
Peritoneal dialysis (PD) uses the dynamic dialysis properties of the
peritoneal membrane. The fraction of the anatomic peritoneal surface area
(PSA) recruited is of importance for maximizing exchanges and is potentially
impacted by parameters such as fill volume.
We describe an in vivo assessment of the contact surface area
by micro-computed tomography (µCT) using an iodinated contrast medium added
to the PD fluid, a contrast agent presumed without surfactant property. In the
isotropic volume (reconstructed voxel size 186 µm x 186 µm x
186 µm), the iodinated PD fluid is automatically selected, thanks to its
contrast difference with soft tissues, and its surface area is computed. The
method was first tested on phantoms showing the ability to select the PD fluid
volume and to measure its surface area. In vivo experiments in rat
consisted of µCT acquisition of rat abdomen directly after intraperitoneal
administration (10 mL/100 g rat body weight) of a dialysis fluid containing
10% by volume iodinated contrast agent. Fluorescein isothiocyanate albumin was
used as dilution marker.
We found a strong linear relationship (R2 = 0.98)
between recruited PSA (cm2) and rat weight (g) in the range of 235
to 435 g: recruited PSA = (1.61 weight + 40.5) cm2. Applying µCT
with a fill volume of 10 mL/100 g rat body weight, the in vivo
measured PSA was in the order of magnitude of the ex vivo anatomic
PSA as determined by Kuzlan's formula, considered in most instances as the
maximal surface area that can be recruited by PD fluid.
This new methodology was the first to give an in vivo
high-resolution isotropic three-dimensional (3-D) determination of the PSA in
contact with dialysate. Its sensitivity allows us to take into account the
recruitment of fine 3-D structures of the PSA membrane that were not
accessible to previous 2-D-based imaging methodologies. Its in vivo
application also integrates the physiological natural tensile stress of
tissues.
KEY WORDS: Peritoneal surface area; in vivo; micro-computed tomography (µCT); rats; small animal imaging.
Received 17 May 2007; accepted 10 October 2007.
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