Chronic inflammatory response in the rat lung to commonly used contrast agents for videofluoroscopy

Abstract

Objectives Contrast agents (CAs) are essential for upper gastrointestinal and videofluoroscopic swallow studies (VFSSs). Recently, we reported that small amounts of Ba aspiration caused severe acute lung inflammation in a rodent model. However, the underlying molecular biological mechanisms of chronic response to CA aspiration remain unclear. The aims of this study were to explore the underlying molecular biological mechanisms of the chronic response to three kinds of CA aspiration on the lung. Study Design Animal model. Methods Eight‐week‐old male Sprague Dawley rats were divided into five groups (n = 6, each group). Three groups underwent tracheal instillation of one of three CAs: barium sulfate (Ba), ionic iodinated contrast agent (ICA), and nonionic iodinated contrast agent (NICA). A sham group was instilled with air and a control group was instilled with saline. All animals were euthanized 30 days after treatment and histological and gene analyses were performed. Results No animal died after CA or sham/control aspiration. Ba particles remained after 30 days and caused histopathologic changes and inflammatory cell infiltration. Iodinated ICA and NICA did not result in perceptible histologic change. Expression of Tnf, an inflammatory cytokine was increased in only Ba aspirated rats ( P = .0076). Other inflammatory cytokines and fibrosis‐related genes did not alter between groups. Conclusion Aspirated Ba particles did not clear from the lung within a month and caused mild chronic pulmonary inflammation. ICA and NICA did not cause any inflammatory responses in the lungs, suggesting that ICA and NICA may be safer CAs for VFSS than Ba. Level of Evidence NA

Unexpected Barium Aspiration

“…Within 30 days, histopathological findings showed thickened bronchiolar walls with staining positive for CD3+ lymphocytes and thickened alveolar walls staining positive for myeloperoxidase (MPO) (+) granulocytes and macrophages for continued chronic inflammation of the respiratory system. 3,4 Although incidence of barium aspiration can be rare with varying prognosis, prevention should always be considered. Alternative diagnostic work up in those with risk factors for aspiration include ultrasound, endoscopy, magnetic resonance imaging (MRI), CT, positron emission tomography (PET) scan, functional endoscopic evaluation of swallowing, or even video fluoroscopic modified barium swallow.…”

“…Barium is a foreign body in the lung, which causes chronic pulmonary inflammation. 3 Barium studies are indicated for any digestive complaints centering around dysphagia. Barium sulfate is an insoluble agent that is used to visualize the gastrointestinal (GI) tract via a bolus that is ingested and later excreted in the feces undigested.…”

“…With the long-term residence of barium deposition, the question remains if it continues to act as a foreign body within the body system. In Ueha et al’s study, 3 60 uL of 60% weight/volume barium suspension was injected to mimic aspiration in rats which is equivalent to 10 mL barium aspiration in humans to study the effects of barium after 30 days. Within 30 days, histopathological findings showed thickened bronchiolar walls with staining positive for CD3+ lymphocytes and thickened alveolar walls staining positive for myeloperoxidase (MPO) (+) granulocytes and macrophages for continued chronic inflammation of the respiratory system.…”

Risk Factors for Aspiration Pneumonia After Receiving Liquid‐Thickening Recommendations

“…Iohexol (Omnipaque; Daiichi-Sankyo) was used as a contrast agent in VFSS since it has low pulmonary toxicity when aspirated into the lung. 22 , 23 To add viscosity to the contrast agent, a thickener (Toromeiku SP; Meiji) was used. First, 5 mL of a moderately thickened liquid (200 mPaċs) was administered, followed by 5 mL of mildly thickened liquid (100 mPaċs) and 5 mL of thin liquid (10 mPaċs).…”

“…Videofluorographic studies were performed and recorded in the lateral view. Iohexol (Omnipaque; Daiichi‐Sankyo) was used as a contrast agent in VFSS since it has low pulmonary toxicity when aspirated into the lung 22 , 23 . To add viscosity to the contrast agent, a thickener (Toromeiku SP; Meiji) was used.…”