Pediatric Interventional Radiology: Blurring the Lines Between Specialties

Abstract

Medical imaging has transformed the ease and speed of patient care with provision of detailed evaluation of anatomic structures and disease processes. Interventional radiology uses imaging guided techniques to further diagnose or treat diseases with minimally invasive methods. These techniques are particularly helpful in treating pediatric patients.

Introduction

The discovery of X-ray production and detection in 1895 by Wilhelm Rontgen marked the advent of the field of medical imaging. In the subsequent century, medical imaging advances would result in ever more sophisticated imaging techniques and insights that have had immeasurable impact for the collective benefit to patients. The magnitude of this benefit is substantiated by the fact that numerous scientists have been awarded Nobel Prizes for their contributions to the field of medical imaging over the past century.

Interventional radiology (IR) is a radiology subspecialty that involves the use of imaging methods such as x-ray, ultrasound, CT scans, and other innovative methods to diagnose and treat diseases involving almost every organ system. Interventional radiologists are trained both in diagnostic radiology and in the minimally invasive techniques using these imaging modalities for delivery of medications and devices in the most innovative fashion with unprecedented precision. It is obvious how minimally invasive techniques are beneficial to patients, and perhaps even more so for pediatric patients owing to their small size and desire to achieve therapies with the least possible disruption to growing patients. In this manuscript, we will briefly review the history of interventional radiology and highlight some of the contemporary ways IR is applied in innovative ways for pediatric patients.

After Rontgen’s X-ray discovery, the first angiogram of a cadaver arm was performed one year later in 1896. While the methods, including the use of mercury sulfide, lime and petroleum, seem crude by today’s standards, the value of such imaging modalities was evident to early medical professionals. Various other imaging techniques ensued over the next few decades including attempts to image the central nervous system by injecting air into the ventricles followed by radiographs to examine the brain for gross structural abnormalities and asymmetry of the ventricles which might suggest an intracranial mass. Not until 1927 was the first successful angiogram performed on a live human patient. Dr. Egas Moniz, a Portuguese physician, performed and documented the first angiogram of the cerebral vasculature performed with rudimentary contrast agents and direct carotid cut downs to access the arteries for injection.¹ After that time others went on to continue advancing the role of angiography and predictably multiple innovations arose in the next decades leading to techniques such as pulmonary, vena cava angiography, and the Seldinger technique for less traumatic access to vessels for subsequent angiography or intervention such as angioplasty or stent placement.

In the 1960s, a visionary radiologist and angiographer, Dr. Charles Dotter, imagined using the angiography catheter as a surgical instrument. In an address he delivered in Europe to a group of multinational radiologists, he described a future state where the catheter could be used as a delivery device for balloons, stents, medications, and other devices.² His vision was very prescient and sparked the next 50 years of development of the specialty of interventional radiology. During this time, there were concurrent advances in the design and manufacture of devices and catheters leading to ever-smaller devices and catheters. Then, in the mid-1980s, several pediatric radiologists began utilizing these imaged guided minimally invasive techniques in children with success.³ Today, the field of pediatric IR is growing and being utilized increasingly for our smallest patients with success in all organ systems.

Interventional Radiology Uses

IR physicians use their skill and training in imaging and imaged guided therapy to perform numerous diagnostic and therapeutic procedures. The most commonly performed IR cases involve placing needles, wires, and catheters under imaging guidance with ultrasound, fluoroscopy, and CT into organ systems and body cavities such as the vascular system, gastrointestinal tract, genitourinary system, biliary tract, peritoneum, pleural space, thecal space, and other fluid collections/abscesses for the purposes of medication administration, nutritional support, diagnostic imaging, laboratory sampling, and therapeutic treatment. In comparison to adult IR, most of these common procedures require only minor variations in technique and equipment to accommodate the smaller size and more delicate tissues of pediatric patients. However, there are other IR procedures that are more specific to pediatric practice based on the unique physiology of the pediatric patient. Additionally, pediatric IR cases also encompass treatment of a larger proportion of congenital lesions as compared to adults.

Sclerotherapy of vascular malformations (congenital malformations of lymphatic vessels, veins, and arteries) while not specific to pediatrics, is most commonly performed early in life. Lymphatic malformations contain serous fluid with varying amounts of internal hemorrhage and are often treated with drainage or aspiration and injection of sclerosant agents such as doxycycline or bleomycin (Figure 1). Venous malformations on the other hand are not aspirated and are generally injected with foamed sotradecol. Precise placement of the proper sclerosant agent is essential especially if the malformation is in a critical area such as in the orbit or near the airway. High flow malformations that involve connections to arterial supply are most commonly treated with precise navigation of a catheter or needle to inject ethanol or embolic agents to occlude the nidus. Following sclerotherapy, the vascular malformation often increases in size for a week or two due to inflammation. Follow-up is planned in a few months to give the lesion time to scar down and allow time for new or untreated areas to develop. Larger or more complex vascular malformations frequently require multiple treatments.⁴

Figure 1.

Newborn male with left axillary lymphatic malformation. A. T2 MR imaging in neonatal period demonstrates a large multilocular cystic lesion in the left axilla with predominantly high signal and heterogeneous areas of low signal suggesting hemorrhage. B. Flouroscopic image from initial sclerotherapy treatment demonstrates multiple drains (white arrows) with contrast (black arrows) in loculated cystic areas. Sclerotherapy was performed through the drains. C. Ultrasound Image from initial sclerotherapy demonstrates a needle (white arrow) advancing into the loculated cystic mass. D. T2 MR imaging 14 months post multiple sclerotherapy treatments demonstrates decreased cystic areas with residual scar tissue which was subsequently removed at surgical debulking.

In addition to congenital lesions, lymphatic collections may also be acquired due to disruption of lymphatic channels, most commonly following thoracic surgery for congenital cardiac anomalies. Lymphatic leaks are notoriously difficult to stop and the first step in treatment is defining the location of the leak. Recent advancements in fluoroscopic and MR lymphangiography provide excellent detail of the lymphatic system and often define the location of a leak. In some cases where the leak arises from small diffuse lymphatic channels, fluoroscopic lymphangiography with lipiodol may even be therapeutic as the viscous and mildly sclerotic contrast agent can occlude small lymphatic channels. Alternatively, after the leak is located, it can be occluded with glue or coils through a catheter placed percutaneously into the thoracic duct. In cases where the duct is too small to cannulate, imaging can help guide an open surgical closure.⁵

There is an ever-increasing role of the pediatric IR physician in the treatment of children with malignancies. This ranges from image guided biopsy procedures to procure necessary tissue for diagnosis to more advanced direct tumor therapies. Pediatric IR physicians also play an important role by placing vascular access devices in children such as PICCs, tunneled lines, and port catheters for oncology therapy. Pediatric types of cancer such as lymphoma also present unique challenges with opportunities for IR intervention. Lymphoma commonly results in mediastinal adenopathy which given the limited space of a child’s chest and pliable tissues may result in mass effect causing airway or mediastinal vessel compression. This presents a challenging clinical scenario in which a diagnostic biopsy is needed prior to treatment and yet treatment would be helpful in decreasing the mass effect to facilitate safer biopsy. These challenging cases require a multidisciplinary approach with IR, Hematology/Oncology, Critical Care, Surgery, Pathology, and Anesthesia. Often, biopsy is safely performed prior to treatment with ultrasound guidance, local anesthetic, and minimal sedation (Figure 2).

Figure 2.

Three year-old female with lymphoma resulting in anterior mediastinal mass. A. CT of the chest demonstrates a large anterior mediastinal mass resulting in mass effect on the major mediastinal vessels (white arrow) and mass effect on the left mainstem bronchus (black arrow). B. Ultrasound image from biopsy with minimal sedation to decrease risk of cardiopulmonary compromise demonstrates the biopsy needle (white arrow) within the mediastinal mass.

Metastatic disease in pediatrics has traditionally been treated with chemotherapy or surgery. However, percutaneous ablation and transarterial chemoembolization which are becoming more common in adult oncology are now being employed in cases of inoperative pediatric metastatic disease. In addition, nonmalignant lesions such as osteoid osteoma and pheochromocytoma may be treated with percutaneous thermal ablation resulting in decreased hospitalization and faster recovery (Figure 3). In the future, the indications for ablation and catheter directed chemoembolization in pediatric oncology will likely increase.

Figure 3.

14 year-old male with right femoral osteoid osteoma. A. Axial CT image with a grid to prepare for treatment demonstrates an osteoid osteoma with cortical sclerosis and central lucent nidus (black arrow). B. CT image with radiofrequency ablation probe in place demonstrates the tip positioned appropriately for treatment across the central nidus (black arrow).

Drainage of infectious or malignant fluid collections is another area that Pediatric IR physicians also contribute to pediatric care with minimally invasive, imaged guided techniques. Ultrasound is frequently employed as the preferred imaging modality to place needles and drains in children as it permits real time precise guidance without using radiation. Abscesses and other fluid collections are routinely drained percutaneously using these techniques sparing surgical intervention for many children (Figure 4). The treatment of parapneumonic effusion or empyema is one such example that has undergone a shift in treatment paradigm from surgical debridement with video assisted thoracoscopy (VATS) to image guided chest tube placement with intrapleural infusion of fibrinolytics such as tissue plasminogen activator. This approach has resulted in excellent results and now is the preferred treatment approach at our institution with success rates approaching 90% obviating the need for surgery.⁶

Figure 4.

13 year-old male with pelvic abscess post perforated appendicitis. A. Sagittal CT image shows a rim enhancing pelvic abscess (white arrow) posterior to the urinary bladder (black arrow). B. Sagittal ultrasound image during transrectal drainage demonstrates a needle and guidewire in the abscess (white arrow) posterior to the urinary bladder (black arrow).

Conclusion

In summary, the field of pediatric interventional radiology has flourished over the past decades due to the increasing development of imaging equipment, smaller devices, and technical innovations lending themselves to caring for the smallest patients. As is evident from this brief overview, the IR scope of practice overlaps with nearly every other specialty in the hospital providing unique opportunities for collaboration. With shorter treatment times, less invasive approaches, and frequent ability to treat and discharge in the same day, IR consults will undoubtedly continue to have growing impact in delivery of efficient, value added patient centered care to pediatric patients with complex medical diseases.

Biography

Douglas C. Rivard, DO, is Radiologist-in-Chief, Children’s Mercy Hospital, Associate Professor Pediatric Radiology, University of Missouri, Kansas City, Kansas City, Mo. Brenton D. Reading, MD, is Assistant Professor, Pediatric Radiology, Children’s Mercy, University of Missouri, Kansas City

Contact: dcrivard@cmh.edu