A new imaging modality in detection of caustic oesophageal injury: Technetium-99m pyrophosphate scintigraphy

Abstract

Early oesophagoscopy is usually recommended in children after caustic ingestion to assess the severity of the initial digestive lesions. An oesophagoscopic procedure in children always demands to be performed under sedation and bears a certain risk of iatrogenic injury. The purpose of the study is to determine the value and sensitivity of Tc-99m pyrophosphate (99mTc-PYP) scintigraphy for the detection of caustic oesophageal injury. The caustic oesophageal burns were created with 25% NaOH in an experimental rat model. Seventeen rats were divided into two groups. The BURN group (n=9) included caustic oesophageal burning rats. Non-BURN group (n=8) included sham-operated rats. All animals underwent 99mTc-PYP scintigraphy 72 h after the burning experiment. Anterior static and single-photon emission computed tomography images were obtained using a low-energy all-purpose collimator, 2.55 zoom factor, 3h after intravenous injection of 10 mCi 99mTc-PYP. After the imaging, all the oesophagi were explored for external determination of the injury sites and macroautoradiographic scintigraphy as well. Rectangular region of interest were placed in the visually determined lesion of oesophagus (O) as well as non-lesion area (N), and an ON ratio was created. The severity and extension of oesophageal burn were assessed 3 days after burning by histopathologic evaluation. The injuries were graded according to the ulcer depth, ulcer width, thrombus formation, and the development of perivascular fibrinoid necrosis. The oesophageal burning areas were demonstrated by visual evaluation of the Tc-99m PYP scintigraphy on all animals. The mean ON ratio of 99mTc-PYP was 21.61+/-7.01 in the BURN group and in the non-BURN group, was 2.25+/-0.24 (p<0.001). The best cut-off point of the ON ratio for caustic oesophageal injury was 5.45, with sensitivity and specificity of 100%. PYP scan findings were also confirmed by histological evidence of ulcer depth, ulcer width, thrombus formation, and perivascular fibrinoid necrosis in the same areas. The caustic oesophageal injuries have been demonstrated by 99mTc-PYP scintigraphy in burning experiment. 99mTc-PYP scintigraphy is sensitive for detection of caustic oesophageal injury. This new imaging tool is found to be sensitive and specific for the detection of caustic oesophageal injury in the rats.