Image-guided interventions in neonates

European Journal of Radiology 60 (2006) 208–220 Image-guided interventions in neonates Brian D. Coley ∗ , Mark J. Hogan Department of Radiology, Columbus Children’s Hospital, 700 Children’s Drive, Columbus, OH 43205, USA Received 10 July 2006; received in revised form 10 July 2006; accepted 12 July 2006 Abstract Minimally invasive interventional radiological procedures can be invaluable in the care of neonates and infants. These procedures have proven to be useful in a wide variety of clinical situations, improving patient care, comfort and safety. Most techniques in adult interventional radiology have been adapted for use in pediatric patients, covering the spectrum of diagnostic and therapeutic intervention. Procedural techniques are similar, but require considerations of patient size, sedation, and support personnel in order to render optimal care. Proper physician training is imperative to provide the necessary confidence and expertise, and post-procedural follow-up is required to maximize positive outcomes. This paper discusses many of the procedures that may be performed in neonates, and offers suggestions and techniques for successful outcomes. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Interventional; Percutaneous; Drainage; Biopsy; Dilation; Embolization 1. Introduction Interventional radiology has dramatically changed the nature of patient care over the last three decades. Image-guided procedures have proven to be useful in a wide variety of clinical situations, improving patient care, comfort and safety. Most techniques in adult interventional radiology have been adapted for use in paediatric patients. Interventional radiology is now part of standard paediatric practice [1–3], even in the neonate. Procedural techniques are similar, but neonates require special consideration with regard to patient (and parent) preparation, sedation and analgesia, equipment selection, and appropriate support personnel [4,5]. These techniques and their modifications are used for conditions found in all ages, as well as unique pathology found in infants. 2. Patient care and equipment In preparing for an interventional procedure, the paediatric radiologist has two patients: the child and the parent. Both require the radiologist’s attention, for both need to be comfortable and secure to allow a successful procedure. Parents are justifiably nervous about their child’s procedure, and are often ∗ Corresponding author. Tel.: +1 614 722 2375; fax: +1 614 722 2332. E-mail addresses: [email protected] (B.D. Coley), [email protected] (M.J. Hogan). 0720-048X/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2006.07.024 coping with stressful medical events of which the interventional radiology procedure is but a small part. They need and deserve explanations of the procedure, its risks, and possible complications. Parents need to see the interventionalist as one of their child’s physicians, not as just an anonymous technician. The person actually performing the procedure, after appropriate parental discussion, should obtain informed consent. Prior to the patient’s arrival in the interventional suite, the radiologist should have reviewed the pertinent diagnostic studies, have a clear idea of the diagnostic or therapeutic intervention required, and be aware of the patient’s clinical status and laboratory values [6]. Coagulation profiles should be known prior to biopsy procedures, and any coagulopathy corrected. Pre-procedural antibiotics should be administered prior to abscess drainage, biliary intervention, and nephrostomy tube placement [7,8]. Much patient (and parental) anxiety can be relieved by a competent staff comfortable with children, distraction techniques, and keeping the parents with the child until sedation has taken effect. Care of ill neonates should be a team approach with the neonatologist, radiologist, surgeon, anaesthesiologist, and ancillary staff all working together. 2.1. Sedation and analgesia The goal of sedation is to provide a level of patient comfort that allows performance of the procedure with the greatest margin of safety possible. There is a wealth of experience with paediatric sedation for both diagnostic and interventional B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 radiology procedures, and clear guidelines have been put forth [9–11]. Radiologists should also become familiar with the conscious sedation protocols and guidelines at their particular hospital. Personnel familiar with the medications and appropriate monitoring equipment must be present. Resuscitation equipment should always be immediately available. There are many choices of sedative medication protocols for paediatric radiology that have proven to be safe and effective, and the choice depends upon the needs of the patient, the complexity of the planned procedure, and the experience of the physician. Sedation should be provided by an experienced physician. This may include the radiologist, the neonatologist, a dedicated sedation team, or an anaesthesiologist. For complex or lengthy procedures in neonates, general anaesthesia and the presence of anaesthesiology or intensive care unit staff is preferred to maximise patient comfort and safety. The importance of the appropriate use of local anaesthesia cannot be overemphasised. Well-delivered local anaesthetic can greatly minimize a procedure’s discomfort, thus minimizing the depth of sedation required. With ultrasound (US) guidance, local anaesthesia can be placed directly along the path that subsequent needles will take and provides very effective local pain control. Remember that organ capsules, periosteum, pleura, and peritoneum are all richly innervated and produce the most pain when transgressed. Local anaesthetics often produce a strong burning sensation when first injected, which can be minimized by injecting very slowly. A common error is to introduce local anaesthetic and then immediately begin the procedure. Local anaesthetics take 1–2 min to take effect, and a short wait can result in a more comfortable procedure for the patient and physician. The maximum dose of each anaesthetic should be known to avoid overdose. 2.2. Equipment The array of equipment available to the interventional radiologist is vast, growing, and changing yearly. The interventionalist should evaluate and select those devices most suited to the procedures performed in his or her practice, and those that perform best for that individual operator. 2.2.1. Needles Almost every interventional procedure starts with placing a needle into a target. The choice of needle should be dictated by the procedure requirements. Coaxial systems with a removable stylet are often useful, as they tend to be echogenic, do not core tissue as they are advanced, and allow aspiration or guidewire passage after stylet removal. Small gauge needles (20- or 22-gauge) of varying length are commonly used for a variety of procedures, especially aspirations of thin fluid collections and injection of contrast. Guide wires (0.018 in.) can be passed through 22-gauge needles (and some 24-gauge angiocatheters) to facilitate subsequent catheter placement. Larger gauge sheathed needles are commonly used for non-vascular interventional access and will accept a 0.035- or 0.038-in. guide wire, which allows greater stability for subsequent manipulation than working over a 0.018-in. wire [12]. 209 2.2.2. Wires Once the desired target has been reached by a needle, placement of a guide wire allows subsequent tract dilatation and catheter placement (Seldinger technique). Small 0.018-in. wires are typically used for vascular access or for access into structures where it would be inappropriate to place a large needle primarily (such as biliary work). Mandril wires provide a very stiff shaft for support with a very flexible tip to prevent trauma to the target structure. Unlike conventional wires, however, one cannot simply feed a long length into the target as the wire will tend to buckle out and access will be lost. As long as one remains aware of wire position, the advantage gained is a very secure working tract that allows dilatation and access into even very tough noncompliant structures. If subsequent dilatation to facilitate larger calibre working wires is needed, a combined sheath-dilator can be placed that allows this exchange in a single step. 2.2.3. Drainage catheters Drainage catheters are available in a variety of materials and sizes, generally from 5 to 14 French. Catheters typically have a locking loop (“pigtail”) that helps to secure the catheter in place. For neonatal drainages, a 5 or 6 French catheter is typically used. Drainage catheters with small pigtail loops are available, which facilitates placement in small collections or neonatal kidneys. Proper catheter fixation is as important as proper size selection and placement. If a catheter becomes prematurely dislodged, it does not matter how dexterous the placement was. The first line of fixation is the internal locking loop of the catheter itself. Secondly, the external portion of the catheter needs to be secured to the skin. Directly suturing the catheter to the skin is one acceptable method, and is very secure. There are also a number of retention devices available that adhere to the skin and then secure the catheter, thus avoiding suturing directly to the patient [13]. However, these devices may be too large for a neonate. A sterile bio-occlusive dressing is generally applied which further helps to secure the catheter. To prevent children from grabbing and pulling at catheters, it may be necessary to further cover the site by a wrapping with gauze or an elastic bandage. 2.2.4. Biopsy devices Biopsy needles are typically constructed with an inner slotted stylet and outer cutting cannula, which yields a core of tissue from the organ sampled. Either manually operated or an automated biopsy “gun” may be used. The depth of penetration into the tissue (the “throw”) varies depending upon the manufacturer. While longer throw devices provide more consistent samples than short throw devices [14], short throw devices may be required in small neonates. Some needles allow selectable throw lengths, and can be adjusted depending on the needs of the case. 2.2.5. Vascular catheters In patients needing long-term vascular access for nutrition, antibiotics, or other therapy, peripherally inserted central catheters (PICC) are often placed. These are available in many sizes, but for neonates 1.9–3 F catheters are most common. Catheters smaller than 3 F need constant infusion to avoid 210 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 occlusion. Larger multilumen catheters are sometimes required, but have increased risks, and are reserved for central venous lines (CVL’s) placed via a jugular, femoral, or subclavian vein. Totally implanted ports can be placed in infants, although this is unusual [15]. ECMO-lines are a special type of “heavy duty” catheters; usually a relatively large lumen is necessary. Diagnostic angiography catheters for neonates are usually 3–4 F, although the 3 F catheters are not widely available. Some 4 F catheters accept a 0.038′′ wire or a 3 F microcatheter. Coaxial systems allow insertion of microcatheters ranging from 1.2 to 3 F for superselective therapeutic interventions such as embolisation or thrombolysis. All angiographic procedures should be performed through a sheath to avoid vascular injury during catheter exchange and manipulation [16,17]. 3. Clinical applications 2.3. Guidance methods 3.1.1. Peritoneal cavity In neonates, the most common reason for abdominal drainage is ascites, or abscess from either necrotizing enterocolitis or after The mainstay of image-guidance in neonatal intervention is US. Sonography is well suited for paediatric work, as children generally have a body habitus favourable for US imaging. US is portable, efficient, and economical, as well as avoiding ionising radiation to the young patient. The portability is important as procedures may be performed in the NICU, and even within an incubator in a critically ill neonate. Structures can be visualised directly, and devices guided to their target under real-time control [18]. Unlike CT, visualisation of the needle is not confined to the axial plane. US is often coupled with fluoroscopy after initial needle placement, to allow visualization of guide wires, catheters, and the instillation of contrast [4,5,19]. Just as accurate diagnoses require the best available equipment, efficient and precise interventional guidance requires optimal imaging. This is particularly true in paediatric work because of the precision required due to small patient size, small target size, and the relatively superficial location of many lesions. Multiple transducers should be available to allow proper visualisation of the structure of interest (i.e. the “target”). Procedures in small neonates usually permit the use of high-frequency linear or curved linear array transducers. When working within a limited acoustic window (such as intercostal approaches), small footprint sector transducers are invaluable. The interventional US machine should be equipped with colour and pulsed Doppler to facilitate recognition of vascular structures [20]. 3.1. Aspiration and drainage Aspiration and drainage of fluid collections is a basic procedure well suited to US guidance. Aspiration may be purely diagnostic, or may be the preliminary procedure prior to placing drainage catheters [22–24]. US can also disclose characteristics of the fluid collection (turbidity, debris, presence of septations), which may influence the procedure and choice of equipment used. While drainage can be performed with US only, fluoroscopy is often useful to properly place catheters without wire or catheter kinking, and to help avoid loss of access during dilatation and catheter deployment. 2.4. Post-procedural care While it is gratifying to have a procedure go smoothly in the interventional suite, the responsibility of the interventional team does not necessarily end once the patient is taken back to the ward. Biopsy patients need to be monitored and checked for postbiopsy haemorrhage. Any time an indwelling catheter is placed, it is the responsibility of the interventional radiology service to ensure its proper care and function. To perform optimally, catheters may need to be irrigated or repositioned, and this is best assessed by those that placed the catheter [21]. Performing daily rounds on patients and communicating openly with the primary clinical service provides better patient care and improves results from radiological intervention. Fig. 1. Abdominal abscess. (A) Longitudinal sonogram from a preterm infant with fevers after episode of NEC shows a complex fluid collection in the left abdomen. (B) US-guided aspiration revealed infection (arrows = needle). B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 211 Fig. 2. Lung abscess. (A) Frontal chest radiograph from an infant with bronchopulmonary dysplasia, fevers, and respiratory distress shows airspace disease in the left upper lobe and right lower lobe (arrows). A central lucency is present (arrowhead) in the right lower lobe. (B) Contrast-enhanced CT scan shows a thick-walled right lower lobe collection (arrowheads) with internal fluid and air representing a lung abscess. (C) Image during portable US-guided drainage shows the catheter being placed within the right lower lobe abscess. The left upper lobe abscess was also drained. (D) Frontal chest radiograph after treatment shows no residual airspace disease. surgical procedures (Fig. 1). Paracentesis is performed for diagnostic purposes (is the fluid infected, bilious, chylous, etc.) and for therapeutic indications (respiratory compromise, abdominal compartment syndrome, abscess). For simple aspirations in neonates, 22-gauge needles and angiocatheters are generally sufficient. For therapeutic drainage of abdominal fluid collections, needle or catheter placement should be in the most dependent part of the peritoneal cavity possible to facilitate proper drainage of the entire collection. The procedure begins the same as for simple aspiration. After a small sample is aspirated for microbiological studies, a guidewire is introduced through the needle or sheath into the collection. The tract is dilated up to the size of catheter to be finally placed, and the catheter itself finally deployed. Once in place, the abscess should be completely aspirated. The completeness of drainage can be assessed by US, and the need for an additional or larger catheter determined. Bleeding is not uncommon as the abscess cavity is collapsed and should cease when aspiration is halted. Irrigation of the abscess cavity is controversial, but should probably be limited as infected material may be forced into the circulation. Similarly, there is little value in performing contrast studies of abscess cavities acutely. If there is suspicion of fistulous communication with another structure due to persistent drainage, this can be investigated after the acute infection has subsided. Catheters are left in place until drainage ceases and the patient becomes afebrile. Followup imaging prior to catheter removal is sometimes required if the patients symptoms do not improve, to evaluate for untreated collections. 3.1.2. Thoracic cavity Thoracentesis is performed for both diagnostic and therapeutic indications. In neonates, pleural effusions may result from 212 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 Fig. 3. Liver abscess. (A) Frontal radiograph from a 26-week preterm infant with fevers and hepatomegaly after an umbilical venous catheter was removed shows an enlarged liver with displacement of bowel to the left. (B) Longitudinal sonogram of the right hepatic lobe shows a complex intrahepatic collection (cursors). (C) Image during bedside US-guided drainage shows a 6 F catheter (arrows) being deployed into the liver abscess. (D) Frontal radiograph shows the drainage catheter in place, and marked reduction in hepatomegaly. chylothorax, congenital heart disease, hydrops, after surgery, and infection. Needles should be placed so that they go just over the top of a rib, avoiding the neurovascular bundle that runs below. If a thoracic collection is obviously infected at aspiration, a drainage catheter should be placed. The catheter should be placed in the most dependent position possible to facilitate thorough drainage. However, care should be taken in placing the catheter immediately on top of the diaphragm, as irritation and shoulder pain may develop. Fibrinolytic therapy should be considered if US suggests multiple septations, if the output is below that expected based on preprocedural imaging, if the follow-up radiographs are not improved, or if the patient does not clinically B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 improve. The various regimens employing streptokinase, urokinase, and tissue plasminogen activator are beyond the scope of this discussion, but all have been employed with success. US is valuable in assessing the need for fibrinolytic therapy by showing whether or not the collection is septated or loculated [25–27]. If there are no septations, or just a few which are thin and mobile, simple drainage is usually effective. If the collection has multiple compartments or thick septations, adjunctive lytic therapy or even surgical intervention will likely be necessary. Lung abscesses may result from necrotizing pneumonias or from haematogenous spread. Percutaneous aspiration is effective for both diagnosis and treatment [28], and can be accomplished with US guidance if the abscess abuts a pleural surface (Fig. 2). For recurrent or large collections, catheter drainage can help to avoid thoracotomy, or at least delay it until the acute infection has been treated. 3.1.3. Liver and biliary tract Focal liver collections are uncommon in neonates, and are often related to complications of umbilical venous catheterization [29,30]. Patients may have hepatomegaly and hepatic enzyme abnormalities. Fevers and sepsis may ensue if the collections become infected [31]. US is highly accurate for the diagnosis of intrahepatic collections, and allows guided aspiration and/or drainage (Fig. 3). Acalculous cholecystitis and gallbladder hydrops are not common in the neonate, but may require percutaneous intervention when they occur [32]. Percutaneous cholangiography is also useful to investigate the status of the biliary tree in neonates with persistent hyperbilirubinemia, and to evaluate choledochal cysts. In neonates, cholangiography can be performed by direct puncture and injection of the gallbladder (percutaneous cholecystocholangiography) (Fig. 4). The study is usually successful even with contracted, small gallbladders, and percutaneous liver biopsy can be performed at the same time. This can obviate open surgical biopsy and cholangiography. Fig. 4. Percutaneous cholecystocholangiogram. Image from an 8-week-old with hyper-bilirubinaemia shows the needle (arrow) entering the gallbladder (GB). Contrast opacifies the common bile duct (arrowhead) and intrahepatic bile ducts, effectively excluding biliary atresia. There is good flow of contrast into the duodenum (D) as well as filling of the pancreatic duct (P). 213 3.1.4. Genitourinary tract Within the genitourinary tract, percutaneous nephrostomy is a common procedure in the neonate to relieve obstruction, to assess the recoverable function of a hydronephrotic kidney, to provide access for endourological procedures, and for drainage of infection [25,33–36]. In the setting of obstruction, administration of pre-procedural antibiotics is prudent. The patient is placed in a prone position, and an appropriate site for renal access is chosen. For simple drainage, a lower pole calyx can be used. If further intervention is anticipated, such as stent placement, placement in a middle or even upper pole calyx may provide a better path for subsequent procedures. If possible, access should be subcostal, as intercostal tube placement produces more patient discomfort and a risk for pneumothorax. For neonates, 5 or 6 F catheters are sufficient for simple drainage. 8 F catheters may be used in older infants, or in those with pyonephrosis, fungal infection, or renal abscesses. The catheter can be used for instillation of antifungal agents or fibrinolytics, or the access can be used for mechanical removal [37–39]. In the infant with hydronephrosis, often with some concomitant renal dysplasia, it is tempting to access the kidney with a small needle and 0.018 in. wire to prevent renal injury. However, it is often very difficult to perform the subsequent dilatation required for catheter placement, as the renal parenchyma can be tough and unyielding, and the smaller guidewire inadequate. With proper technique and direct US visualization, a larger sheathed needle can be placed on a single pass (Fig. 5), the final working wire placed directly, and the procedure completed less traumatically [12]. Other genitourinary interventions include percutaneous cystostomy for bladder outlet obstruction in which a urethral catheter cannot be passed. This allows bladder decom- Fig. 5. Neonatal hydronephrosis. Longitudinal sonogram during US-guided percutaneous nephrostomy shows a 19G access needle (arrow) safely placed through a dilated calyx (arrowhead) into the renal pelvis. 214 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 Fig. 6. Cloacal malformation and obstruction. (A) Longitudinal sonogram shows a dilated obstructed cloaca (*) posterior to the bladder. (B) Image during US-guided drainage shows the access needle tip (arrow) within the collection (*). Drainage was complete after catheter placement. pression, relief of ureteric pressure and frequent concomitant hydronephrosis, as well as providing access for antegrade studies to better define the anatomy of the obstruction. In cloacal malformations and other Mullerian developmental abnormalities, an obstructed cloaca, vagina or uterine horn sometimes requires percutaneous drainage prior to definitive surgical treatment (Fig. 6). Neonatal ovarian cysts are common, and while usually asymptomatic they are prone to torsion when over 4 cm in size. Surgical resection has been the traditional treatment, although US-guided aspiration of simple cysts is a viable alternative [40]. 3.2. Biopsy Prior to any biopsy procedure, it is important to consult with the pathologist about the type, size, and quantity of sample needed. The goal of the procedure is to make a diagnosis, and the pathologist needs to be provided with the requisite material. US-guided biopsy provides a safe and minimally invasive Fig. 7. Liver biopsy. (A) Image from an US-guided liver biopsy shows an outer guiding cannula (arrowheads) with tip within the liver parenchyma. (B) Through the cannula, an automated biopsy device was passed and deployed into the liver (arrow). (C) Because of concern about hemostasis, gelatin sponge was placed through the cannula into the biopsy tract. Air within the material (arrowheads) produces increased echogenicity. B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 215 Fig. 8. Percutaneous gastrostomy. (A) Fluoroscopic image shows that one gastric fastener has already been deployed (arrow). The needle (arrowhead) for the second fastener has been passed and contrast injection confirms placement within the stomach (S). The colon (C) is opacified with barium given orally the night before the procedure. (B) After the fasteners are placed, needle is reinserted and directed toward a snare (arrow) and a wire (arrowhead) passed. The wire is subsequently pulled up and out of the mouth to provide secure access for the remainder of the procedure. (C) Dilators (arrow) are passed over the wire to enlarge the gastrostomy tract. (D) Lastly, the gastrostomy tube is passed and the retention balloon (B) inflated. alternative to open surgical and blind percutaneous biopsy [41]. Most solid visceral lesions are visible with US, allowing accurate tissue sampling. Muscle biopsies, soft tissue masses, head and neck lesions, and primary tumours [42–45] can be successfully sampled percutaneously. Chest and mediastinal masses can be sampled, provided that the lesions abut the chest wall and have no intervening lung to obscure the acoustic window [46,47]. Liver biopsy is performed for characterisation of diffuse disease and for focal hepatic lesions, and is best performed with US guidance [48]. For general tissue sampling, the right lobe is generally biopsied, as it contains the greatest volume of liver parenchyma and allows easy avoidance of vascular structures. Once the area of interest is localized with US, an appropriate site is chosen for skin entry, preferably below the costal margin. Local anaesthetic should be placed liberally adjacent to the peritoneum and liver capsule to minimize pain. Two 16G core biopsies are generally sufficient for routine histologic studies, but occasionally 18G samples are sufficient, or larger 14G specimens may be required. If multiple specimens are needed, a guiding needle can be placed into the liver to avoid multiple puncture holes in the capsule. The needle is directed at the area of interest, away from vascular structures. The biopsy needle tip should be placed deep to the liver capsule, to prevent undo trauma to the capsule when the needle is deployed. This is especially true when using biopsy guns, as the needles tend to bounce and deflect off the capsule. Bleeding complications are minimal with appropriate attention to coagulation profiles and correction of any abnormalities prior to the procedure. If an outer guiding cannula is used, haemostatic materials (such as gelatin sponge) can be placed in the biopsy tract to promote haemostasis (Fig. 7). Renal biopsy is seldom required in neonates and infants. In older children, large sample volumes, typically 14G or 15G, are 216 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 217 often required for evaluation of renal architecture. However, adequate specimens can be obtained with 18G automated devices [49,50]. The preferred site for kidney biopsy is the lower pole lateral to the collecting system. To minimise bleeding complications, the hilar vessels and medullary region should be avoided. Complications include bleeding and arteriovenous fistula formation [35]. 3.3. Gastrointestinal intervention Percutaneous gastrostomy tube placement is most commonly performed in neonates with neurological dysfunction preventing safe or adequate oral intake, or in neonates with high caloric or specific nutritional requirements [51]. Gastrostomy tubes may be placed surgically, via endoscopic techniques, or via interventional radiological techniques. Endoscopic techniques can be difficult in small neonates, and the imaging technique decreases (but does not eliminate) the risk of injury to the colon, liver, and spleen. Interventional techniques have the advantage of being less traumatic and allowing rapid institution of enteric feeding. Placement of gastro-jejunostomy tubes, often required in these patients due to gastro-oesophageal reflux, can be performed at the same time. The details of this procedure are well described in the literature, and both retrograde and anterograde techniques are available [51,52]. Briefly, the location of the liver, spleen, colon and small intestine are determined, an appropriate site below the left costal margin and to the left of the rectus musculature chosen, the stomach inflated, and percutaneous fasteners placed to secure the stomach to the anterior abdominal wall. An enteric access tube appropriate for the patient can then be placed (Fig. 8). Complications include gastric leak and infection, most of which are treatable non-surgically [51]. Bowel dilatation of enteric strictures offers a safer alternative to blind dilatations and surgical excision. The most commonly performed dilatation is the oesophagus, usually after tracheooesophageal fistula or oesophageal atresia repair, although oesophageal strictures from epidermolysis bullosa or gastrooesophageal reflux may also be dilated [53]. After stricture localisation, a guide wire is passed through the stricture and appropriate dilatation performed with fluoroscopic monitoring (Fig. 9). A contrast study is performed after dilatation to exclude oesophageal perforation. While most commonly performed transorally, if the patient has a gastrostomy tube retrograde access offers a safe access route that is often better tolerated. Other enteric strictures are amenable to balloon dilatation, although the more distant from a site of access the difficult they become [51]. Balloon catheters are relatively stiff and cannot be manipulated around very many turns within the GI tract. However, for those strictures that can be reached, successful dilatation can be performed, such as after necrotizing enterocolitis or bowel anastamoses. Fig. 10. Lumbar puncture. Longitudinal sonogram during lumbar puncture shows the spinal needle passing under an unossified spinous process (P) with the needle tip (arrow) within the cerebrospinal fluid within the thecal sac (T). 3.4. Lumbar puncture Lumbar puncture is a routine part of sepsis evaluation in neonates. When attempts by clinicians are unsuccessful, the interventional radiologist is often consulted for assistance. However, after such attempts US often shows compression of the thecal sac by epidural collections that preclude cerebrospinal fluid sampling. If clear fluid is visible, US provides a means of guided lumbar puncture free from radiation exposure in neonates Fig. 11. Hepatic venous sampling in an infant with persistent hypoglycaemia. Arteriogram image shows a sampling catheter within a hepatic vein (black arrow). A reverse curve catheter is at the origin of the celiac axis (black arrowhead). Contrast injection through a selective catheter (white arrow) placed into the gastroduodenal artery fills branches supplying the pancreatic head and the right gastroepiploic artery. Fig. 9. Oesophageal dilatation. (A) Oesophagram from an infant with feeding difficulties after oesophageal atresia repair shows a narrow anastomotic stricture (arrow) and dilatation of the proximal oesophageal pouch (arrowhead). (B) During inflation of an 8 mm angioplasty balloon, a waste (arrow) is seen at the stricture site. (C) With continued inflation, the balloon fully expands and the stricture is dilated. (D) Contrast injection after dilatation shows no contrast extravasation and reduced dilatation of the upper oesophagus. 218 B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 and young infants with incompletely ossified vertebral posterior elements (Fig. 10) [54]. 3.5. Vascular intervention Long-term central venous vascular access is a crucial part of many neonatal therapies, and interventional radiologists are increasingly the providers of this service. Peripherally inserted central catheters (PICC) are commonly placed to provide vascular access lasting from weeks to months. US guidance for venopuncture allows optimum site selection and relatively atraumatic access using Seldinger technique. While some authors avoid the lower extremities [55], others report no greater complication than with upper extremity access [56], and the lower extremities are often the preferred sight in post-operative cardiac patients to avoid thrombotic complications in surgically created shunts. The relative ease of interventional access has increased the utilization of PICC lines. These lines are not, however, without risk, especially in very small infants. Even small catheters fill a greater area of the vein than in adults. This may produce venous congestion of the involved extremity (although this is typically transient), or lead to eventual thrombosis. Thromboses occur in up to 30% of patients [57], and venous stenoses are common, especially in patients who have received multiple lines. When thrombosis occurs, PICC lines typically occlude the peripheral veins only, while CVL’s usually cause central venous occlusion. Delayed infectious complications are equivalent to other forms of venous access [55,57], and early infections can be avoided with strict adherence to sterile technique during line placement [55]. With modern imaging, arteriography is seldom necessary for diagnosis. However, some neonatal conditions are best treated by arteriographic intervention or transvascular therapy. Transcatheter therapeutic procedures can be performed via transfemoral approaches, or via umbilical access in the newborn. The smaller the child, the greater the potential for local vascular complications, such as thrombosis, which can result in vascular compromise to the limb and long-term growth complications. Fig. 12. Haemangioendothelioma embolisation. (A) Gadolinium-enhanced T1-weighted axial MR image from a 10-month-old with a left chest wall haemangioendothelioma and consumptive coagulopathy shows a large infiltrating mass. (B) Selective arteriogram demonstrates marked vascularity (C = clavicle). (C) After embolisation with polyvinyl alcohol particles, the vascularity is markedly reduced. (D) After further embolisation and placement of vascular coils, the tumour is nearly avascular. Note the secondary hypertrophic changes in the clavicle. B.D. Coley, M.J. Hogan / European Journal of Radiology 60 (2006) 208–220 Systemic heparinisation, (Doppler) monitoring of pulses distal to the puncture site, and aggressive treatment of any resulting access thrombosis can minimize this complication. In neonates with persistent hypoglycaemia, blood sampling can help differentiate between diffuse nesidioblastosis and an isolated insulinoma. Two techniques have been described: direct percutaneous transhepatic portal, mesenteric, and splenic vein sampling, and transarterial stimulation with hepatic venous sampling (Fig. 11) [58,59]. Haemangioendotheliomas and haemangiomas are benign vascular neoplasms common in neonates. They can occur anywhere in the body. These tumours generally undergo a period of growth in early infancy before regressing in early childhood. Most are asymptomatic, but children may present with hepatomegaly (when intra-hepatic), cardiac overcirculation from arterio-venous shunting within the mass, or consumptive coagulopathy (Kasabach–Merritt syndrome in the Kaposiform variant). While generally amenable to medical therapy, some patients will not respond and benefit from transcatheter treatment. Selective catheterization of hepatic arterial feeders allows embolisation with particles, glue, or coils (Fig. 12). Patients typically respond rapidly, but some very large tumours or those with significant portal–systemic venous shunting may prove refractory, and embolisation of the arterial supply to the liver in the setting of severe portal–systemic shunting may cause liver necrosis [60]. Peripheral vascular malformations can be from arterial, capillary, venous, or lymphatic origin. Embolisation of AVMs is indicated if organ compromise or high output cardiac failure are present. Large venous, lymphatic, or mixed malformations may present in the neonatal period with airway compromise. Emergent drainage and subsequent sclerotherapy may be indicated. Vein of Galen vascular malformations are a complex of various anomalies ranging from single to multiple arterio-venous fistulae to arterio-venous malformations with a defined vascular nidus. Patient presentation is variable, ranging from asymptomatic cranial bruits, to congestive heart failure from arteriovenous shunting, to hydrocephalus and neurologic abnormalities from brain ischemia. Whether and when to intervene is controversial, especially in the neonatal period. Transcatheter intervention aims to treat medically refractory cardiac failure and to reduce arterial steal and subsequent ischemic brain injury. The results can be dramatic, but a high morbidity and mortality exists, which must be honestly conveyed to the parents prior to treatment [61,62]. 4. Summary Minimally invasive interventional radiological procedures can be invaluable in the care of neonates and infants by offering less physiologically stressful diagnostic and therapeutic options. Most diagnoses and interventions can be performed with US. To provide optimal care, there needs to be a dedicated team of physicians, technologists and nurses to attend to each case. 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