NMC: Bowel-cleansing methods affect PET/CT image interpretation

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Avoiding contact laxatives is necessary to decrease intestinal artifacts in PET/CT image interpretation and a low-residue diet is not beneficial for colonic preparation, according to a study published in the April issue of Nuclear Medicine Communications.

The objective of the study was to evaluate bowel-cleansing methods for colonic preparation, based on the findings of PET/CT scans, explained Dom-Gene Tu, MD, from the department of nuclear medicine at Chia-Yi Christian Hospital in Chia-Yi, Taiwan, and colleagues.

A total of 175 patients were enrolled in the study. Patients with histories of colorectal cancer, abdominal operation or abdominal malignancies were excluded from the study.

The patients were divided into three groups according to the three kinds of bowel-cleansing methods used: no laxatives or dietary restriction (control group), dietary restriction (low-residue diet) and a combination of contact laxatives (Dulcolax) and dietary restriction (low-residue diet).

Colonic standardized uptake value data were recorded by Tu and colleagues. The hot spots that influenced the interpretation of images or the localization of true lesions were classified as positive, while data that did not influence clinical diagnosis were classified as negative by the researchers.

In the first group with no laxatives or dietary restriction, 22.2 percent of the patients with positive colonic hot spots were detected in whole-body PET/CT scans. In the dietary restriction group, 34.9 percent of colonic hot spots were visible. The third group, with a combination of contact laxatives and dietary restriction, yielded a 73.5 percent positive rate. The positive rate in the third group was significantly higher than the percentages detected in the first and the second groups, stated Tu and colleagues.

The findings indicated that a low-residue diet is not beneficial to colonic preparation. Moreover, contact laxatives cause diagnostic confusion when PET/CT images are interpreted. Therefore, although PET/CT scans are capable of adding precision to functional imaging and to focal localization, Tu and colleagues concluded that avoiding contact laxatives is necessary to decrease intestinal artifacts.