Date Published: June 22, 2020
Publisher: Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia
Author(s): Ítalo Medeiros Azevedo, Robson Macedo, Keyla Borges Ferreira Rocha, Cláudia Nunes Oliveira, Aldo Cunha Medeiros.
The objective of this study was to investigate the accuracy of 18F-FDG-PET in the diagnosis of multibacterial abdominal sepsis by cecum ligation and puncture (CLP) in rats.
Adult Wistar rats ( Rattus norvegicus ), weighing 227±35g, were allocated into a sepsis group by CLP (n=10) and sham group (n=10). 18F-FDG-PET using microPET was performed on all rats after 24 hours.
All animals survived for postoperative 24h. The abdomen/liver ratio of the standardized uptake value (SUV) percentage was significantly higher in the sepsis group than in the sham (p=0.004). The ROC curve showed an accuracy of 18F-FDG-PET to detect abdominal sepsis of 88.9% (p=0.001), sensitivity of 90% and specificity of 88.9%. When a cut-off point of 79% of the ratio between the SUV on the abdominal region and liver was established, the sensitivity was 90%, specificity of 88.9%; positive and negative predictive values of 90.0% and 88.9%, respectively.
The diagnostic accuracy of 18F-FDG-PET in rats with abdominal sepsis was significantly high. It was also demonstrated the predictive ability of the abdomen/liver SUV ratio to diagnose abdominal sepsis. These findings may have implications for the clinical setting, locating septic foci with PETscan.
Abdominal sepsis results in the systemic inflammatory response syndrome, as an inflammatory response due to intra-abdominal infection, trauma, and various diseases1 . Sepsis is considered to involve physiological changes in the body towards high metabolism. Characteristic changes include excessive metabolism of proteins and lipids, increased energy consumption, negative nitrogen balance, excessive production of glycogen levels and hyperglycemia2 . Hyperglycemia is an important causal factor for increased metabolism in sepsis and is responsible for high morbimortality3 .
The project was submitted to the institutional Animal Use Ethics Committee, and it was approved under protocol 003/2015. All experimental procedures were performed based on the guidelines of Brazilian Law No. 11,794/08.
All animals survived until the end of the observation period. At this time, the weight of the animals in the sepsis group was lower (224.0±29.35g) than the sham (234.5 ± 36.57g), but the difference was not significant (p = 0.503). Table 1 summarizes the average values and variability of the injected dose of 18F-FDG (MBq), weight (g) of the animals and blood glucose (mg / dL), in addition to inferential tests.
The present study investigated the action of 18F-FDG-PET on the diagnostic accuracy of abdominal sepsis in rats. In this study, blood glucose was measured before the 18F-FDG-PET was performed. Hyperglycemia is frequently seen in septic patients, associated with the great severity of the disease, with high morbidity and mortality. In response to an acute injury, high levels of serum hormones, such as glucocorticoids and catecholamines, are released, increasing liver gluconeogenesis and insulin resistance. In addition, during sepsis, pro-inflammatory cytokines participate in its pathogenesis13 . Several studies have shown that hyperglycemia can result in reduced FDG uptake in tissues, presumably due to the competitive inhibition of Glut-1 and 3 and hexokinase activity14 – 16 .
The diagnostic accuracy of 18f-FDG-PET in rats with abdominal sepsis was significantly high. It was also demonstrated the high predictive ability of the abdomen/liver SUV ratio, making it easier to locate abdominal sepsis.