論文

The umbilicus is a scar of the umbilical cord containing various embryonic remnants that can lead to postnatal diseases. It is the collection point for blood and lymphatic flow and other structures. Hence, various diseases and conditions can occur. In this review, we aimed to categorize umbilical diseases based on the embryonic remnants, including urachal remnants, omphalomesenteric duct anomalies, and complications of the umbilical arteries and veins. The urachus, formed from the allantois, can result in anomalies such as patent urachus and urachal cysts, with infections being the most common complication. Radiologists must note that urachal carcinoma is a rare complication presenting with characteristic imaging findings. The omphalomesenteric duct can lead to Meckel’s diverticulum, the most prevalent gastrointestinal anomaly. In addition, obliterated umbilical arteries and veins can cause various conditions, including hernias and abscesses. This review also summarizes the umbilical ring lesions, such as gastroschisis and omphalocele, and iatrogenic lesions associated with laparoscopic procedures and catheter placement. Imaging techniques such as ultrasound, computed tomography, and magnetic resonance imaging are crucial for diagnosing and managing these conditions. Understanding the embryological basis and imaging features of umbilical diseases is vital for timely diagnosis and treatment.

Currently, no three-dimensional reference data exist for the normal coccyx in the standing position on computed tomography (CT); however, this information could have utility for evaluating patients with coccydynia and pelvic floor dysfunction. Thus, we aimed to compare coccygeal parameters in the standing versus supine positions using upright and supine CT and evaluate the effects of sex, age, and body mass index (BMI) on coccygeal movement. Thirty-two healthy volunteers underwent both upright (standing position) and conventional (supine position) CT examinations. In the standing position, the coccyx became significantly longer and straighter, with the tip of the coccyx moving backward and downward (all p < 0.001). Additionally, the coccygeal straight length (standing/supine, 37.8 ± 7.1/35.7 ± 7.0 mm) and sacrococcygeal straight length (standing/supine, 131.7 ± 11.2/125.0 ± 10.7 mm) were significantly longer in the standing position. The sacrococcygeal angle (standing/supine, 115.0 ± 10.6/105.0 ± 12.5°) was significantly larger, while the lumbosacral angle (standing/supine, 21.1 ± 5.9/25.0 ± 4.9°) was significantly smaller. The migration length of the tip of the coccyx (mean, 7.9 mm) exhibited a moderate correlation with BMI (r = 0.42, p = 0.0163). Our results may provide important clues regarding the pathogenesis of coccydynia and pelvic floor dysfunction.

CT performed in the supine position has been highly effective in diagnosing organic diseases such as cancer, arteriosclerosis, and infections, significantly contributing to increased life expectancy. In an ageing society, extending healthy life expectancy becomes more critical, requiring early diagnosis of functional disorders. We have led the industry-academia collaboration in developing an upright MDCT system. Although this system maintains the same physical specifications as conventional MDCT, it differs significantly in imaging configuration—allowing supine, upright, and sitting positions—and offers improved workflow while requiring only two-thirds of the installation space. Unlike conventional MDCT, it allows for the assessment of anatomical changes under gravity. It also enables the objective diagnosis and grading of functional diseases, in which findings were not apparent on conventional CT, and enable the study of the pathogenesis of functional diseases which worsen symptoms in the upright position. Furthermore, it allows for noninvasive evaluation of dynamic functions such as swallowing and voiding, which can only be assessed in standing or sitting positions.

Purpose: To investigate the utility of radiomics features of diffusion-weighted magnetic resonance imaging (DW-MRI) to differentiate fat-poor angiomyolipoma (fpAML) from clear cell renal cell carcinoma (ccRCC). Materials and methods: This multi-institutional study included two cohorts with pathologically confirmed renal tumors: 65 patients with ccRCC and 18 with fpAML in the model development cohort, and 17 with ccRCC and 13 with fpAML in the external validation cohort. All patients underwent magnetic resonance imaging (MRI) including DW-MRI. Radiomics analysis was used to extract 39 imaging features from the apparent diffusion coefficient (ADC) map. The radiomics features were analyzed with unsupervised hierarchical cluster analysis. A random forest (RF) model was used to identify radiomics features important for differentiating fpAML from ccRCC in the development cohort. The diagnostic performance of the RF model was evaluated in the development and validation cohorts. Results: The cases in the developmental cohort were classified into three groups with different frequencies of fpAML by cluster analysis of radiomics features. RF analysis of the development cohort showed that the mean ADC value was important for differentiating fpAML from ccRCC, as well as higher-texture features including gray-level run length matrix (GLRLM)_long-run low gray-level enhancement (LRLGE), and GLRLM_low gray-level run emphasis (LGRE). The area under the curve values of the development [0.90, 95% confidence interval (CI) 0.80–1.00] and validation cohorts (0.87, 95% CI 0.74–1.00) were similar (P = 0.91). Conclusion: The radiomics features of ADC maps are useful for differentiating fpAML from ccRCC. Graphical abstract: [Figure not available: see fulltext.]

The World Health Organization classification of renal cell tumors was updated to its fifth edition in 2022 and incorporated significant changes with contributions from pathologists and radiologists. In the 2022 updated classification, epithelial renal tumors are now divided into six categories. Four of these six categories represent the major subtypes of renal tumors: clear cell renal tumors, papillary renal tumors, oncocytic and chromophobe renal tumors, and collecting duct tumors. Two additional categories, representing relatively rare renal tumors, termed other renal tumors and molecularly defined renal carcinomas, have been introduced. While neoplasms in the other renal tumors category are classified on the basis of their histopathologic features, similar to the major subtypes, molecularly defined renal carcinomas represent a new category based on molecular characteristics. In recent years, the number of these rare subtypes has increased significantly. Many of these relatively rare renal tumors represent conventional subtypes that have been reclassified or renamed. Notably, papillary renal cell carcinoma (pRCC) type 2 has been reclassified as other renal tumors or molecularly defined renal carcinomas. As a result, many tumors in these two categories demonstrate gradual enhancement, similar to the enhancement of pRCCs. However, one or more of the following features may differ from those of typical pRCCs: patient age, growth pattern, nonenhanced attenuation at CT, degree of enhancement, homogeneity, T2 signal intensity, and presence of metastases. Careful evaluation of these features can raise suspicion for a rare subtype and is essential for guiding urologists in determining the surgical strategies and guiding pathologists in selecting appropriate immunohistopathologic and/or genetic tests for accurate diagnosis. ©RSNA, 2026 Supplemental material is available for this article. See the invited commentary by Davenport and Pedrosa in this issue.

＜文献概要＞PUCは,浸潤性尿路上皮癌の稀なサブタイプで,病理組織学的には,形質細胞腫,悪性リンパ腫,印環細胞癌,転移性乳癌や胃癌と類似している.

＜文献概要＞放射線科読影レポートは形式よりも,依頼医に意図と判断が正確に伝わることが重要である。本稿では,筆者の基本的な考え方,施設における運用ルール,実践上の工夫を整理し,若手放射線科医が日常診療で活用できる実践的なレポート作成の指針を提示する。

われわれは全身撮影可能な立位CTを企業と共同開発した．従来の臥位CTと同等の物理特性をもち，設置面積は従来のCTの3分の2で済み，X線撮影のようなワークフローで検査が行える．健常人での検討では，これまで位置が変化しないとされてきた脳や骨盤が立位で下垂していることがわかり，重力下の人体構造が少しずつ明らかになっている．特に，静脈は立位と臥位での容量変化が部位により異なっており，画像での静脈学を構築する端緒についた．また，骨盤底の緩みや躯幹・大腿などの部位ごとの筋肉量の評価も可能であり，個々の筋萎縮に応じた運動の仕方を示唆することができる．疾患としては，ヘルニア・臓器脱などは定量的に評価可能であり，変形性膝関節症のような運動器疾患の早期発見も可能である．さらに，嚥下・呼吸・排尿・歩行機能などの動態機能の評価とそれに関連する病態の早期発見が可能である．立位CTを通して，健康長寿の時代のニーズに貢献できることを目指したい．