Neuroimaging of pediatric central nervous system infections and acute encephalopathy has been transformed by advances in vaccination, evolving epidemiology (notably post-COVID-19), new disease concepts, and imaging technology. This review highlights recent developments, including the characteristics and latest findings concerning fetal inflammatory response syndrome (FIRS) and congenital cytomegalovirus (CMV) infection. We also discuss the establishment of infection-triggered encephalopathy syndromes (ITES) as a new conceptual framework.

Pediatric lower respiratory tract infections are among the most common conditions encountered in pediatric practice. Clinical decision-making often focuses on the presence of pneumonia, evaluation of the causative pathogen, and the appropriateness of antibiotic therapy. Routine chest radiography for pediatric lower respiratory tract infections is not recommended by the World Health Organization or other international guidelines, but imaging findings can provide valuable pathophysiological information in selected clinical settings. In this review, pediatric community-acquired lower respiratory tract infections are broadly categorized into viral and bacterial infections, and the relationships between characteristic disease processes and chest radiographic findings are summarized. Typical imaging features of bronchiolitis, viral interstitial pneumonia, alveolar (lobar) pneumonia, bronchopneumonia, round pneumonia, necrotizing pneumonia, and Mycoplasma pneumonia are described with reference to their pathological backgrounds. Chest imaging should not be regarded as a tool for identifying specific causative pathogens, but rather as a modality for understanding the underlying disease processes occurring in the lungs. Appropriate interpretation of imaging findings requires integration with patient age, epidemiological trends, and clinical course.

Children presenting with abdominal pain and diarrhea are encountered on a daily basis in pediatric emergency practice. Imaging is not required for diagnosis of infectious enteritis itself, but computed tomography (CT) is frequently performed in clinical practice to assess patients with a poor general condition or to evaluate potentially severe complications. Therefore, radiologists need to recognize the characteristic imaging findings of infectious enteritis and to differentiate this condition from non-infectious enteritis and surgical abdominal diseases. In this article, we first review the basic imaging findings for pediatric abdominal infections based on the underlying pathophysiology of viral and bacterial enteritis. We then summarize the clinical features, disease distribution, characteristic imaging findings, and important complications associated with common pathogens, including Campylobacter, Salmonella, Yersinia, enterohemorrhagic Escherichia coli, and viral gastroenteritis. Furthermore, we discuss conditions of non-infectious enteritis that should be considered in the differential diagnosis, including eosinophilic gastroenteritis, IgA vasculitis, lupus enteritis, and Crohn disease, and highlight key imaging features that help distinguish these entities from infectious causes. In imaging evaluation of pediatric enteritis, a comprehensive and systematic assessment of bowel wall layering, disease distribution, and extraintestinal findings is required for accurate diagnosis and appropriate clinical management.

Endoscopic retrograde cholangiopancreatography (ERCP) in children is limited by factors such as the technique, a scope diameter that is larger than the pediatric intestine, and the need for general anesthesia. In recent years, advances in imaging technology have enabled acquisition of more detailed images of the hepatobiliary and pancreatic ducts, leading to decreased use of pediatric ERCP. However, in small children, we have experienced cases in which images obtained by CT and MRCP may lead to diagnostic uncertainty. For adult cases, development of ERCP devices has progressed and endoscopic treatment for walled-off necrosis following severe acute pancreatitis has become feasible. Application of devices used for ERCP in adult cases is possible in the pediatric field, and pediatric ERCP may be useful for diagnosis and treatment of various hepatopancreatic diseases and injuries. In this article, we discuss diagnosis and treatment of pediatric hepatobiliary and pancreatic diseases, as well as main pancreatic duct injuries, using ERCP.

The diagnostic approach for central nervous system (CNS) tumors is undergoing a transformation, with the WHO Classification of CNS Tumours, 5th Edition (WHO CNS5), placing a strong emphasis on molecular genetic diagnosis. A clear separation has been established through recognition of the distinct molecular biological bases of pediatric and adult brain tumors. This review outlines the key changes in WHO CNS5, particularly the classification of pediatric-type diffuse gliomas (pLGG/pHGG) and the characteristic pediatric molecular alterations (e.g., H3, BRAF mutations). The redefinition of the highly aggressive diffuse midline glioma (DMG), H3 K27-altered, and the latest molecular-targeted therapies, such as BRAF inhibitors, ONC201 targeting H3K27M, and CAR-T cell therapy, are also discussed. Finally, the review emphasizes the crucial role of the diagnostic radiologist as a “navigator of precision medicine” through a radio-genomics approach and multidisciplinary collaboration in molecular diagnosis and treatment monitoring.

Neuronal migration disorders are characterized by disruption of cortical layer architecture and the appearance of ectopic gray matter or heterotopia. Identification of LIS1 (PAFAH1B1) and DCX revealed that agyria, pachygyria, and band heterotopia form a continuum. ARX, which is involved in interneuron development, causes lissencephaly/agenesis of the corpus callosum due to loss-of-function mutations. In contrast, gain-of-function mutations involving polyalanine tract expansion cause functional disorders, such as epilepsy, intellectual disability, and motor impairment. Onset age and severity increase proportionally to the expansion length of polyalanine residues, which is referred to as interneuronopathy. Tubulinopathies are caused by microtubule abnormalities, and characterized by an indistinct anterior crus of the internal capsule. Channel abnormalities identified in polymicrogyria, as well as in epileptic disorders, have revealed the relationship between structural and functional abnormalities at the molecular level. Thus, mTOR activation causes focal cortical dysplasia and megalencephaly-related disorders, whereas reduced mTOR activity leads to lissencephaly (pachygyria). Molecularly targeted therapies are emerging as potential treatments for functional abnormalities like seizures and intellectual disability in neurodevelopmental disorders such as neuronal migration disorders.

Background: Imaging modalities involving radiation exposure, such as plain abdominal X-ray and contrast studies, remain the standard approach for diagnosis of neonatal gastrointestinal disorders. In contrast, gastrointestinal ultrasonography in neonates has yet to become widely adopted.

Rationale: Because neonates have small body sizes and minimal adipose tissue, the distance between the body surface and the gastrointestinal tract is short. This allows for detailed visualization of the bowel with excellent spatial resolution using high-frequency ultrasound probes. Numerous studies have reported the usefulness of gastrointestinal ultrasound in diagnosis of neonatal gastrointestinal diseases, including its value in assessing intestinal blood flow using Doppler techniques.

Challenges: Doppler evaluation in neonates often poses difficulties: it is challenging to suppress body movement and crying, breath-holding cannot be performed, and high-frequency oscillatory ventilation (HFOV) frequently causes artifacts that interfere with accurate assessment.

Objective: In this context, we aim to investigate the utility and limitations of Doppler blood-flow assessment in neonatal gastrointestinal ultrasonography.

A medical device utilizing laser speckle imaging has been developed to evaluate blood flow. This non-contact method enables real-time visualization of microcirculatory blood flow dynamics and has many clinical applications. We evaluated the effects of procedures and surgical manipulation on tissue blood flow using a laser speckle blood flow imaging system. (1) In orchidopexy procedures on mobile and retractile testicles, testicular blood flow decreased more significantly after dissection of perivascular tissues in retractile testicles, which required more extensive dissection. (2) During reduction of a prolapsed liver back into the abdominal cavity in a giant umbilical hernia, blood flow was maintained even when grossly abnormal coloration was observed on the liver surface, allowing the reduction to proceed while monitoring blood flow changes. Decreased tissue blood flow during procedures or after surgery can influence outcomes. A laser speckle blood flow imaging device can visualize microcirculatory blood flow dynamics non-invasively in real time, as a potential indicator for the required extent of procedural or surgical intervention.

Testicular torsion is a urological emergency that requires prompt detorsion. At our hospital, diagnosis is established with ultrasonography, followed by manual detorsion. Ultrasonographic findings for testicular torsion include enlargement of the affected testis and epididymis, asymmetry of the testicular longitudinal axis, absent or diminished intratesticular flow, a whirlpool sign, and alterations within the intratesticular parenchymal echotexture. Manual detorsion is typically attempted to detort toward outward rotation. Successful reduction is indicated by recanalization of blood flow within the intratesticular hyperperfusion and disappearance of the whirlpool sign. If hyperperfusion is absent or recanalization is not absent, reduction failure should be considered, due to residual torsion despite correct rotation or incorrect detorsion. Manual detorsion alone achieves only “detorsion”, whereas surgical detorsion can include detorsion, orchiopexy and/or tunica albuginea incision. Ideally, surgical exploration should follow promptly after manual detorsion.

A 4-year-old girl with a history of trichotillomania and trichophagia presented with recurrent abdominal pain. Abdominal ultrasonography revealed a partial twinkling artifact (TA) in the stomach. Rapunzel syndrome with trichobezoar in the stomach was diagnosed, and surgery was performed, during which additional trichobezoars were found in the duodenum and small intestine. All were removed. There has been no recurrence after her hair was shortened.

TA is associated with coarse-surfaced, highly reflective objects that cause irregular reflection or scattering of ultrasound waves, resulting in time and phase shifts that are misinterpreted by color Doppler devices as velocity. This phenomenon is useful for diagnosis of stones or calcifications. It is of note that a partial TA was observed in this case. Therefore, a phantom experiment using sewing thread as a hair substitute was conducted, and this successfully reproduced the partial TA.

Based on the above, TA on ultrasonography of the upper abdomen may be a finding suggestive of gastrolithiasis, while partial TA suggests hair gastroliths. These findings can help clinicians determine the appropriate treatment in such cases.