| Lung clearance of inhaled 99mTc-DTPA by urine excretion ratio. |
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G Y Suh, K Y Park, M P Jung, C G Yoo, D S Lee, Y W Kim, S K Han, J K Jung, M C Lee, Y S Shim, K Y Kim, Y C Han |
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Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea |
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| Abstract |
Background
Lung clearance of inhaled 99mTc-DTPA reflects alveolar epithelial permeabilty and it had been reported as more sensitive than conventional pulmonary function tests in detecting lung epithelial damage. However, measuring lung clearance of inhaled 99mTc-DTPA by gamma camera may not always reflect alveolar epithelial permeability exactly because it is influenced by mucociliary clearance depending on the site of particle deposition. Moreover, this method takes much time and patient’s effort because he has to sit or lie still in front of the camera for a prolonged period. Most of the absorbed DTPA is excreted in urine within 24 hours and the amount of excreted DTPA in urine during the first few hours after inhalation is influenced by absorption rate which is correlated with the alveolar-epithelial permeability suggesting that the urinary excretion, especially in first few hours, may be an alternate index for lung clearance. The purpose of this study was to evaluate the usefulness of ratio of excreted 99mTc-DTPA in 2 hour and 24 hour urine as an index of alveolarepithelial damage.
Methods
Pulmonary function tests including diffusing capacity and lung clearance of 99mTc_DTPA measured by gama camera (T1/2) and 2hr/ 24hr urine excretion ratio (Ratio) of inhaled 99mTc-DTPA in 8 normal subjects and 14 patients with diffuse interstitial lung disease were compared.
Results
1) In the normal control , there was significant negative correlation between the T1/2 and the Ratio (r= -0.77, p1/2 and Ratio(r= -0.63, p1/2 was 38 .65 ± 11. 63 min which was significantly lower than that of normal control, 55.53 ± 11.15 min and the Ratio was 52.15 ± 10 .07% also signifantly higher than that of the normal control, 40.43 ± 5.53% (p<0 .05).
3) There was no significant correlations between T1/2 or Ratio and diffusing capactiy of lung in both patients and controls (p> 0.05).
Conclusion
These results suggests that 2hr/ 24hr urine excretion ratio of inhaled 99mTc-DTPA is a useful simple bedside test in assessing alveolar epithelial permeabi1ity and that it may be used as an additive fo llow-up test in patients with diffuse interstitiallung disease complementing conventional pulmonary function tests. |
| Key Words:
99mTc-DTPA, Lung clearance, Urine, DILD |
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