A comparative study of the pancreas in paediatric patients with cystic fibrosis and healthy children using two‑dimensional shear wave elastography
Ferhat Can Piskin, Sibel Yavuz, Sevgul Kose, Cagla Cagli, Dilek Dogruel, Gokhan Tumgor, Kairgeldy Aikimbaev
J Ultrasound 2020 Dec;23(4):535-542. doi: 10.1007/s40477-020-00432-3. Epub 2020 Feb 7.
Cystic fibrosis (CF) is a monogenic disease [1] with an incidence of 1/2500 live births, characterised by an autosomal recessive inheritance caused by mutations in the CFTR gene on chromosome 7. The deficiency of the cystic fibrosis transmembrane regulator (CFTR) protein leads to clinical manifestations of CF [2]. This protein is expressed on the surface of membrane of secretory and absorptive epithelial cells of several organs like pancreas, liver, intestine, airway and sweat gland [3]. In particular, pancreatic insufficiency affects about the 85% of the CF patients and results in the malabsorption of fat and protein [4]. In CF disease the progressive loss of acinar tissue caused by enzyme autodigestion of pancreas parenchyma starts in the intrauterine life and leads to inflammation and fibrosis [5, 6]. Ultrasound is a methodical frequently used in patients with CF due to absence of radiation exposure and due to large access to the methodical. Has been described in literature that CF patients frequently have ultrasonographic alteration in pancreatic parenchyma [7]. In particular, the severely affected pancreas appears hyperechoic and small, as expression of pancreatic atrophy and replacement of the pancreatic parenchyma by fibrous tissue and fat [8]. However, the majority of studies in literature only describe qualitative ultrasounds pancreatic characteristics of CF patients.
The aim of the authors of the present study is to compare quantitative sonographic values obtained with shear wave elastography (SWE) on paediatric patients with already diagnosed cystic fibrosis, with healthy paediatric cohort. They conducted their study on 38 CF and 38 healthy children who underwent a first evaluation through conventional B-mode and a second 2D-SWE evaluation. Some parenchymal characteristics of pancreas such as echogenicity (compared to the liver echogenicity), homogeneity, stiffness, size of the head, body and tail and capsule sharpness were evaluated during B-mode evaluation. During the 2D-SWE evaluation 2D elastography colour maps were obtained and circular ROIs of 5x5 mm were placed in, during a single breath-hold. This was repeated five time separately for the head, body and tail. Then, mean values were recorded. For the CF group, on the conventional US evaluation the mean diameters of the head, body, and tail of the pancreas were significantly higher in the health children group than in the CF group (p = 0.016, p < 0.005, and p < 0.005, respectively). The mean 2D-SWE values of the patients with CF were 1.01 ± 0.16 m/s for the head, 1.03 ± 0.05 m/s for the body, and 1.02 ± 0.05 m/s for the tail, while those of the healthy control group were 1.31 ± 0.01 m/s for the head, 1.28 ± 0.08 m/s for the body, and 1.30 ± 0.10 m/s for the tail. On 2D-SWE evaluation, pancreatic values of the CF group were significantly lower than those of the healthy control group (all p < 0.005 for the pancreatic head, body, and tail, respectively). Using ROC values the threshold value for the head, body, and tail of the pancreas were determined as 1.19, 1.13, and 1.12 m/s respectively and the sensitivity of the test was determined as 81.5%, 76.3%, and 73.3%, while the specificity was 97.3%, 100%, and 100%, respectively.
The study carried out and the results obtained could be very relevant in the CF scenario because literature lacks quantitative information about pancreatic status in the evolution of CF in children. Engjom T. et al. assessed some qualitative pancreatic parenchymal characteristics in patient with CF > 15 years old, such as hyper-echogenicity and lipomatosis, which are related to the exocrine insufficiency. Nevertheless they only performed a qualitative evaluation, based on a visual analogue scale (VAS), with an acceptable inter-observer variability [9].
Some limitations of the study included a significant difference found by the authors in BMI between the two groups that can affect SWE values and a minimum threshold age of 5 years old of the population included, due to patient incompatibility. Further study with wider age range would be advisable to confirm these interesting results in order to detect a pancreatic involvement in early period.
In conclusion, the authors found a non-invasive quantitative evaluation of pancreas damage with a high sensitivity and specificity, establishing some cut-off values of SWE. This could be decisive for therapy management and follow-up of CF patients.
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Dr. Benedetta Bracci is a radiology resident at the University of Rome "Sapienza" - Sant'Andrea University Hospital in Rome, attending the third year of residency. Her main field of interest is paediatric radiology, with a particular attention to the Abdominal area. During the years she trained 7 months at the Paediatric Hospital “Bambino Gesù” in Rome to gain experience in this field. She has also been actively involved in clinical imaging research, and she has contributed as a co-author in some publications.
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