Beatty, John S.

Merchen, Todd D.

Paulson, William D.

Pollock, David M.

Pollock, Jennifer S.

Wach, Paul F.

White, John J.

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resorption of our animal model was further repressed than
those used in Lomashvili’s experiments.4
The mechanism of FMC generation remains uncertain.
Although the formation of FMC might be just a
physicochemical phenomenon related to ambient
phosphate and calcium levels, we speculate that some
other factors should participate in FMC formation because
of the following two findings. First, using mass spectro-
metry, we found similar FMC in the serum of a
hemodialysis patient whose adjusted serum calcium and
phosphate levels were only 10.6mg per 100ml and 6.0mg
per 100ml, respectively. Second, the maneuver of
centrifugation reduced the level of fetuin-A from
0.807 g/l to 0.211 g/l in the sera of 20 diabetic chronic
kidney disease stage 4 patients who had coronary
artery calcification detected by computed tomography,
suggesting the presence of FMC even in normal ranges of
calcium and phosphate. (Mikami et al. American Society
of Nephrology 2007 presentation; J Am Soc Nephrol 18.
747A, 2007).
1. O’Neill WC. Mineral complexes and vascular calcification. Kidney Int 2009;
76: 915.
2. Mikami S, Hamano T, Fujii N et al. Serum osteoprotegerin as a screening
tool for coronary artery calcification score in diabetic pre-dialysis patients.
Hypertens Res 2008; 31: 1163–1170.
3. Matsui I, Hamano T, Mikami S et al. Fully phosphorylated fetuin-A forms a
mineral complex in the serum of rats with adenine-induced renal failure.
Kidney Int 2009; 75: 915–928.
4. Lomashvili KA, Monier-Faugere MC, Wang X et al. Effect of
bisphosphonates on vascular calcification and bone metabolism
in experimental renal failure. Kidney Int 2009; 75: 617–625.
Isao Matsui1, Takayuki Hamano1, Satoshi Mikami1, Yoshitaka Isaka1
and Hiromi Rakugi1
1Department of Geriatric Medicine and Nephrology, Osaka University, Suita,
Osaka, Japan
Correspondence: Takayuki Hamano, Osaka University, Geriatric Medicine
and Nephrology, 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan.
E-mail: hamatea@medone.med.osaka-u.ac.jp
Enterovesical fistula and
roundworms
Kidney International (2009) 76, 916; doi:10.1038/ki.2009.276
Gupta et al.1 describe a man with urinary obstruction due to
the presence of Ascaris lumbricoides. No further investigation
was conducted to determine why such roundworms were
present in the urinary system. The life cycle of A. lumbricoides
in humans is spent only in respiratory and gastrointestinal
tracts.2 Enterovesical fistula is possible, and the common
causes for such fistulas, e.g. colon cancer and sigmoid
diverticulitis, may present in the patient.3 Failure to perform
further investigations on this aspect would delay the
diagnosis and management of a treatable disorder.
1. Gupta P, Sundaram V, Abraham G et al. Obstructive uropathy from Ascaris
lumbricoides. Kidney Int 2009; 75: 1242.
2. Ascariasis. http://www.dpd.cdc.gov/dpdx/html/Ascariasis.htm (accessed
15 May 2009).
3. Naguib NN, Sharaf UI. Vesicorectal fistula, case report and review of
literature. Curr Urol 2008; 2: 211–213.
Weekitt Kittisupamongkol1
1Faculty of Medicine, Chulalongkorn University, Patumwan, Bangkok,
Thailand
Correspondence: Weekitt Kittisupamongkol, Faculty of Medicine,
Chulalongkorn University, Bangkok 10330, Thailand.
E-mail: weekitti@gmail.com
Complications impair the
usefulness and validity of the rat
tail arteriovenous fistula model
Kidney International (2009) 76, 916; doi:10.1038/ki.2009.311
To the Editor: We wish to follow up the report of a new rat
tail model of the hemodialysis arteriovenous fistula (AVF).1
Such models are potentially important because maturation
failure of AVFs is a major unsolved problem. Lin et al.1
reported 5/5 successful operations in which the lateral vein
was anastomosed end-to-side to the ventral artery. We report
our experience in creating 27 such AVFs.
We have found that technical problems limit the
usefulness of this model. Sample tail fistulas were dissected
several weeks after AVF, and dense scar tissue (adhesions)
encased the arteries and veins. These adhesions compressed
the vessels and likely altered the flow characteristics.
Other obstacles encountered included thrombosis and
dessication. We found that systemic heparinization before
the procedure and minimization of vessel occlusion time
reduced the risk of thrombosis. Compromise of the
wound closure, anastamotic compression, and alteration
of blood vessel elasticity resulted when meticulous attention
was not paid to ensuring that the tissue was sufficiently
moist.
We concur that the tail fistula is technically feasible;
however, a technically successful tail fistula is subjected to
external forces that compromise flow characteristics, thereby
calling into question the validity of this model. Turbulence
and low shear stress are believed to induce stenosis in
AVFs, rendering adhesion avoidance crucial to the applica-
tion of the tail fistula as a model of hemodialysis access
dysfunction.
1. Lin T, Horsfield C, Robson M. Arteriovenous fistula in the rat tail:
a new model of hemodialysis access dysfunction. Kidney Int 2008; 74:
528–531.
John S. Beatty1, Paul F. Wach2, William D. Paulson3,
Todd D. Merchen1, David M. Pollock2, Jennifer S. Pollock2
and John J. White3
1Department of Surgery, Medical College of Georgia, Augusta, Georgia, USA;
2Vascular Biology Center, Medical College of Georgia, Augusta, Georgia, USA
and 3Department of Nephrology, Medical College of Georgia, Augusta,
Georgia, USA
Correspondence: John S. Beatty, Medical College of Georgia, Department
of Surgery, 1120 15th Street, BB 4516, Augusta, Georgia, 30912, USA.
E-mail: jbeatty@mcg.edu
916 Kidney International (2009) 76, 911–917
l e t te r to the ed i to r


Complications impair the usefulness and validity of the rat tail arteriovenous fistula model 

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Complications impair the usefulness and validity of the rat tail arteriovenous fistula model

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