Bowel preparation for CT colonography: blinded comparison of magnesium citrate and sodium phosphate for catharsis.
OBJECTIVE
To compare colonic cleansing and fluid retention of double-dose magnesium citrate with those of single-dose sodium phosphate in patients undergoing computed tomographic (CT) colonography.


METHODS
This retrospective HIPAA-compliant clinical study had institutional review board approval; informed consent was waived. The study included 118 consecutive patients given single-dose sodium phosphate for bowel catharsis and 115 consecutive patients at risk for phosphate nephropathy, who were instead given double-dose magnesium citrate. The bowel preparation regimen was otherwise identical. Four-point scales were used to assess residual stool and fluid in the six colonic segments, and attenuation of residual fluid was measured. An a priori power analysis was performed, and unpaired t tests with Welch correction were used to compare the two groups on stool and fluid scores and fluid attenuation.


RESULTS
Both cathartic regimens offered excellent colon cleansing, with no significant difference for residual stool in any of the six segments. Stool scores of 1 or 2 (ie, no residual stool or residual stool <5 mm) were recorded in 88.6% (627 of 708) of colonic segments in the sodium phosphate group and in 88.1% (608 of 690) in the magnesium citrate group. No clinically important differences were seen in residual fluid scores in any of the six segments, with the only significant difference seen in the sigmoid colon (2.17 for sodium phosphate vs 2.44 for magnesium citrate; P< 0.01). Fluid attenuation was significantly different between magnesium citrate and sodium phosphate groups (790 HU +/- 216 vs 978 HU +/- 160; P <.001).


CONCLUSIONS
Both sodium phosphate and magnesium citrate provided excellent colon cleansing for CT colonography. Residual stool and fluid were similar in both groups, and fluid attenuation values were closer to optimal in the magnesium citrate group. Since bowel preparation provided by both cathartics was comparable, magnesium citrate should be considered for CT colonography, particularly in patients at risk for phosphate nephropathy.
Borden
Zachary S
ZS
Department of Radiology, University of Wisconsin School of Medicine and Public Health, 600 Highland Ave, G3/310 CSC MC 3252, Madison, WI 53792-3252, USA.
Pickhardt
Perry J
PJ
Kim
David H
DH
Lubner
Meghan G
MG
Agriantonis
Demetrios J
DJ
Hinshaw
J Louis
JL
D002400:Cathartics / Q000008:administration & dosage*; D019343:Citric Acid / Q000008:administration & dosage*; D003106:Colon / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds / Q000008:administration & dosage*; D010710:Phosphates / Q000008:administration & dosage*; D012189:Retrospective Studies
D002400:Cathartics; D009942:Organometallic Compounds; D010710:Phosphates; D019343:Citric Acid; C110422:magnesium citrate; C018279:sodium phosphate