The purpose of this study was to determine whether in vitro proton (1H) magnetic resonance spectroscopy (MRS) is useful for distinguishing between abdominal types of fluids.

Thirty fluid samples that were obtained from patients who were undergoing diagnostic or therapeutic percutaneous drainage of abdominal fluids were examined in this study. According to their gross appearance and smell, each sample was classified as either purulent fluid (n=12) or non-purulent fluid (n=18). The non-purulent fluids were subdivided into hemorrhagic fluid (n=2), serosanguinous fluid with debris (n=2), and serosanguinous fluid without debris (n=14). In addition, according to the cytologic analysis, each sample was classified as either benign fluid (n=23) or malignant fluid (n=7). A set of humoral pathological examinations that included biochemical analysis and culture of the fluid were performed for all the fluid samples. In vitro 1H MRS was performed by using a 1.5T MR system and a birdcage head coil. MR spectra were obtained by using point-resolved spectroscopy (PRESS) (TR/TE=2000/30 msec) with water suppression. The MR spectra were analyzed on the basis of agreement between a radiologist and a physicist who worked in consensus.

The MR spectra obtained from 30 samples could be classified into 8 different patterns, according to the presence of lipid (0.9/1.3 ppm), lactate (1.3 ppm), acetate (1.9 ppm), and succinate (2.4 ppm) peaks. The MR spectral patterns of the purulent fluids (n=12) were classified as follows: pattern-1 (n=7, 58%), pattern-2 (n=2, 17%), pattern-3 (n=1, 8%), pattern-6 (n=1, 8%) and pattern-8 (n=1, 8%). The MR spectral patterns of the non-purulent fluids (n=18) were classified as follows: pattern-4 (n=1, 6%), pattern-5 (n=5, 28%), pattern-6 (n=1, 6%), pattern-7 (n=3, 17%) and pattern-8 (n=8, 44%). The MR spectral patterns of the purulent fluids were significantly different from those of the non-purulent fluids (p < .05). The MR spectral patterns of benign fluids (n=23) were classified as follows: pattern-1 (n=7, 30%), pattern-2 (n=2, 9%), pattern-3 (n=1, 4%), pattern-4 (n=1, 4%), pattern-5 (n=3, 13%), pattern-6 (n=2, 9%), pattern-7 (n=1, 4%) and pattern-8 (n=6, 26%). The MR spectral patterns of malignant fluids (n=7) were classified as follows: pattern-5 (n=2, 29%), pattern-7 (n=2, 29%) and pattern-8 (n=3, 43%). No significant difference was found between the spectral patterns of the benign and malignant fluids (p= .300).

In vitro 1H MRS could be useful for differentiating between purulent fluid and non-purulent fluid.