Many lymphatic diseases are intractable, but in recent years, research into them has been progressing, helping to clarify the disease and develop treatment. In basic research, the molecular mechanism of lymphangiogenesis was gradually elucidated, and the causative genes of lymphedema were listed. In addition, studies on mutant gene mutations such as PIK3CA in various diseases are advancing, and new therapeutic agents such as sirolimus are being developed. In the future, the classification of diseases would be further organized by type of gene mutation. On the other hand, techniques for visualizing lymphatic vessels, such as ICG lymphangiography and MR lymphangiography, are rapidly developing in clinical practice. As an application, it has become possible to approach the lymphatic vessels, which has been difficult until now, and embolization for lymphatic leakage is being established as an effective treatment method. It is hoped that the development of wide-angle research will further advance understanding and eventually lead to an optimal treatment method.

Fluorescent lymphangiography using indocyanine green (ICG lymphangiography) has high resolution and reproducibility, enabling evaluation of lymph fluid reflux in skin in detail and identification of lymphatic position effectively. Also, it can be safely performed even in pediatric patients, as it requires no radiation exposure, and allergic reactions risks are low. In fact, as lymphatic venous anastomosis has become a popular treatment for lymphedema, ICG lymphangiography has become widely used in clinical practice. Furthermore, the indications have expanded and been applied to lymphatic diseases other than lymphedema, and individual lymphatic flow is becoming unveiled. In this chapter, I will outline the practice of the method, which plays an important role in the diagnosis of various lymphatic diseases.

One of the crucial functions of the lymphatic system is maintenance of fluid balance. However, due to a lack of clinical imaging and interventional techniques, the lymphatic system has remained under the radar of the radiology community. The recently developed intranodal lymphangiography and MR lymphangiography have opened the door for lymphatic imaging and intervention.

Lymphatic disorders include lymphedema and lymphorrhea. Among them, idiopathic or secondary lymphatic leakage is a rare condition but can become potentially life-threatening. Postoperative lymphatic leakage is the leading cause of traumatic lymphatic leakage and can arise anywhere within the lymphatic system. Therefore, an appropriate lymphangiography technique is essential for identifying the leakage point.

Recently, interventional radiology has become available for the treatment of lymphatic leaks represented by chylothorax and abdominal lymphatic leakage associated with surgery. In the field of pediatrics, plastic bronchitis and protein losing enteropathy associated with congenital heart disease are also reported to be associated with lymphatic leakage, which can be treated by intervention.

This article comprehensively reviews the clinically relevant lymphatic anatomy, lymphangiography techniques and criteria for their selection, and treatment strategies for various kinds of lymphorrhea.

The pathogenesis of infantile chylothorax (IC) varies widely and is very complicated. Frequently it causes difficulties in treating such patients. The recent improvements in imaging technology have made it possible to evaluate the central lymphatic system and clarify some previously unknown pathophysiologies. Additionally, with marked progress in therapeutic techniques, it is becoming increasingly important to evaluate the underlying condition of patients with IC, and radiologists can contribute to it. Herein, we are going to review the pathophysiologies of IC with imaging findings.

Pediatric patients often need sedation because they cannot understand and cooperate with the examination. Especially, infants and young children have to stay still during MRI examination and always need sedation. Sedative drugs influence general conditions such as respiration and circulation. Committee of the Japan Pediatric Society, the Japanese Society of Pediatric Anesthesiology, and the Japanese Society of Pediatric Radiology published “Recommendations on Pediatric Sedation for MRI Examination” in 2013 and its revised edition in 2020. We decided to manage sedation of pediatric patients undergoing MRI examination under one-day hospitalization. The safety of MRI examination improved by monitoring vital signs in a hospital ward and the dosage of sedative drugs was reduced due to being in a calm single room. On the other hand, some patients awoke during waiting or moving to an examination room after they were sedated with sedative drugs. Issues such as cooperation with the radiology technicians should be resolved. The medical fee increased from 3000 to 4000 points.

Pyomyositis occurs mostly in the trunk and lower extremities, and there are few reports of it occurring in the upper extremity in the absence of predisposing factors such as trauma or immunocompromised conditions. We report a case of a previously healthy three-year-old girl who developed left triceps muscle pyomyositis. She presented with left upper limb immobility due to pain and fever. Laboratory data showed an elevated white blood cell count and C-reactive protein level. MRI revealed no abnormal findings in the bone marrow; however, there were inflammatory findings in the triceps muscle and the surrounding fatty tissue. Although the blood cultures were negative, she improved after treatment with intravenous antibiotics and was discharged without any sequelae. If the diagnosis is delayed and the disease progresses to abscess formation, it may require surgical treatment and even leave sequelae. We believe that this condition should also be considered as a differential diagnosis in patients with fever accompanied by local limb pain. Early diagnosis using MRI at an appropriate time is essential for preventing invasive procedures.

Sialolithiasis commonly occurs unilaterally, in the submandibular gland and duct of adults, causing transient swelling and pain in the salivary gland during eating. A 13-year-old girl presented with swelling, redness, and pain on her right cheek. Computed tomography (CT) showed bilateral parotid sialolithiasis with right suppurative parotitis. The inflammation spread from the right parotid duct to parotid gland due to the right stone blocking the duct at the distal end. Intravenous antibiotic therapy, bougie insertion, and salivary gland massage were administered. She recovered immediately; however, we continue to observe subclinical sialoliths in the bilateral parotid glands. Although sialolithiasis is uncommon in children, we must be aware of salivary stones when a patient shows swelling and pain of the salivary gland that is not only transient during eating, but also occurs continuously.