PubMed · 8442321
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R G Hahn. 1993. Measuring irrigating fluid absorption during TURP.. https://doi.org/10.1016/0090-4295(93)90583-v
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OBJECTIVE: The lactulose H2-breath test is the most widely used non-invasive approach for evaluation of orocoecal transit time (OCTT). In the present study, doubly-labelled lactose-[13C, 15N]ureide (DLLU) was synthesized to investigate the OCTT in comparison to the conventional lactulose H2-breath test. Additionally the bacterial breakdown rate (BBR) and rate of elimination and the metabolic pathways of the cleavage products of DLLU (13CO2, [15N]urea, and 15NH3) were investigated. DESIGN AND SUBJECTS: In a first study, DLLU was administered as a single oral-pulse-labelling (dosage: one gram) either without and after pretreatment of five grams of unlabelled lactoseureide (LU) on the day prior to the study to twelve healthy adult volunteers after breakfast. Breath and urine were collected in one and two hour-intervals, respectively, over a one-day period. 13C-enrichment in breath as well as 15N-enrichment in urine fractions were measured by continuous flow-isotope ratio mass spectrometry (CF-IRMS). In a second study, lactulose was administered to the same subjects (dosage: ten grams). Breath was collected in quarter, half and one hour-intervals over a ten hour-period. Hydrogen concentration in breath was analysed using an electrochemical detector. RESULTS: The comparison of the lactose-[13C]ureide 13CO2-breath test and the lactulose H2-breath test showed that the mean increase of the 13C-enrichment in CO2 occurred 1.18 h later than the mean increase of H2 in breath. The resulting OCTTs derived from the two methods were 3.02 +/- 1.4 and 1.84 +/- 0.5 h (P < 0.05) and the corresponding BRs were 9.63 +/- 3.4 and 6.07 +/- 1.7 h (P < 0.01), respectively. The 15N-enrichment of urinary urea and ammonia without and after pretreatment with LU started between two and three hours after DLLU-administration. The cumulative percentage urinary excretion of the 15N- and 13C-tracer was 29.9% and 13.6% respectively, and was slightly increased after LU-pretreatment to 32.1% and 14.6% of the dose administered. A total of 35.2% of the 13C was found to be exhaled and remained approximately constant after LU-pretreatment (36.2%). CONCLUSIONS: The use of the lactulose H2-breath test for evaluation of the OCTT showed a statistically significant shortening of 1.18 h in comparison to the lactose-[13C]ureide 13CO2-breath test in healthy adults. The most important limitations of the lactulose H2-breath test are its low specificity and sensitivity due to dose-dependent accelerations of OCTT, interfering H2-rise from malabsorbed dietary fibre and H2-non-producers. In contrast, our lactose-[13C]ureide 13CO2-breath test was confirmed to avoid these disadvantages and to yield reliable results. This test is recommended especially if higher sensitivity and specificity is required, if IRMS-technique is available and if lactulose H2-tests lead to insufficient results.
A breath test employing 14C-urea is commonly used to detect the presence of Helicobacter pylori in the stomach of patients with peptic ulcer. 14C-urea is not available commercially as a radiopharmaceutical. It is available only as non-pharmaceutical grade material. A technique for preparing individual patient doses was therefore validated and methods for demonstrating the quality of the 14C-urea raw material and final product were developed. Individual patient doses, each containing 100 kBq 14C and 350 mg urea in 1 ml, were prepared and stored at -20 degrees C. Each batch consisted of approximately 400 doses. The activities of samples from each batch were measured by liquid scintillation counting immediately after preparation (99.6 +/- 4.9 kBq) and 6 months later (98.2 +/- 4.7 kBq). The chemical identity of the 14C-urea was demonstrated by a thin-layer chromatographic technique in which the 14C was shown to have the same Rf value as stable urea. The high radiochemical purity of the final product was demonstrated by the presence of only one peak on the thin-layer chromatogram. The radionuclide identity of the 14C-urea was demonstrated by beta-ray spectroscopy. This technique of preparing individual patient doses of 14C-urea results in a product that is stable for at least 6 months.