BACKGROUND: To develop a simple method for simultaneous solid and liquid gastric emptying assessment using a dual isotope labelled breath test.
MATERIAL AND METHODS: 13 patients were given 100 g ground beef labelled with 25 MBq ^99mTc sulphur colloid and 74 KBq ¹⁴C octanoic acid, and 150 ml 10% glucose drink labelled with 8 MBq ⁶⁷Ga citrate and 150 mg ¹³C acetate. 10 normal volunteers were given the same test meals but labelled with ¹⁴C and ¹³C only. Breath was collected at baseline and regularly for 4 hours. The ¹⁴CO₂ and ¹³CO₂ activity was measured with liquid scintillation counting and mass spectroscopy. The times to maximum ¹⁴CO₂ and ¹³CO₂, were determined. Comparison was made between times to maximum ¹⁴CO₂ with scintigraphic retention of ^99mTc at 100 minutes and times to maximum ¹³CO₂ with the scintigraphic half-clearance time of ⁶⁷Ga.
RESULTS: For the solid meal, the times to maximum ¹⁴CO₂ were: 60–120 minutes in the 8 patients with normal gastric emptying of ^99mTc; 75–145 minutes for the 10 healthy volunteers; 75–180 minutes for the remaining 5 patients with abnormal gastric emptying of ^99mTc. There was a weak but significant correlation (r = 0.56, p < 0.025) between the time to maximum ¹⁴CO₂ and gastric retention of ^99mTc at 100 minutes. For the liquid meal, times to maximum ¹³CO₂ were: 20–35 minutes for the 4 with normal gastric emptying of ⁶⁷Ga; 15–40 minutes for the 10 healthy volunteers; 20–75 minutes for the remaining 9 patients with abnormal gastric emptying of ⁶⁷Ga. There was a strong and significant correlation (r = 0.88, p < 0.005) between times to maximum ¹³CO₂ and gastric half-clearance time of ⁶⁷Ga.
CONCLUSIONS: Breath tests utilising test meals labelled with *C isotopes are valid alternatives to scintigraphic studies using ^99mTc and ⁶⁷Ga for the simultaneous assessment of gastric emptying of solids and liquids.