Over the last 20—30 years, interventional radiology has made an essential contribution to patient management. The speciality has developed from angiographic techniques, with guidewires and catheters as key ingredients. The parallel developments in cross-sectional imaging have provided enhanced guidance for interventional procedures and radiology has evolved from providing purely diagnostic information to therapy, offering effective alternatives in the treatment of abdominal and thoracic disorders. In some instances, interventional radiology techniques have replaced the conventional surgical approach, removing the need for a general anaesthetic with consequent decreased morbidity and length of hospital stay, with similar patient outcome. The increasing complexity and sophistication of both surgery and available intetventional techniques requires close liaison in decision making between the surgeon and radiologist to choose the optimum method of treatment.
Percutaneous biopsy is possible for most radiologically detected abnormalities. Small lesions immediately adjacent to major vessels or a biopsy path that traverses the colon may be regarded as relative contraindications but the decision often depends on local expertise. In general, the shortest route from skin to lesion is chosen if no vital structure intervenes. Fluoroscopy usually provides suitable guidance for biopsy of large parenchymal or peri hilar masses in the chest. CT guidance may be necessary for small lesions. Ultrasound or CT guidance is most commonly employed in the abdomen. Ultrasound is quick and flexible and allows the needle path to be followed in real time without additional radiation burden to the patient. Small lesions and lesions which cannot be adequately imaged with ultrasound, particularly within the retroperitoneum, are more appropriately biopsied under CT control (Fig. 2.30).
A platelet count of less than 80 000 or an international normalised ratio (INR) of greater than 1.3 should be corrected where possible, by the administration of fresh frozen plasma and/or vitamin K, where appropriate, prior to biopsy. Gross ascites should be drained prior to liver biopsy unless biopsy via a transjugular approach is available. The choice of needles is wide. In general, an 18G automatic spring-loaded cutting needle provides an excellent core biopsy. Larger 14G needles may be useful where architectural assessment is required in patchy disease, e.g. cirrhosis. Cytological analysis via 22G needle is often adequate for the diagnosis of malignancy. Accuracy rates exceed 80 per cent. Negative biopsies may be due to faulty needle placement. Complications are unusual, occurring in less than 2 per cent of patients and include haemorrhage, pancreatitis, pneumothorax and occasional seeding of the needle track by tumour.
Drainage of abscesses and fluid collections
Almost any fluid collection in the chest, abdomen or pelvis may be considered for percutaneous catheter drainage, which has largely replaced surgery as the treatment of choice. Initially percutaneous drainage was confined to large superficial postoperative collections, but use has broadened to include complex multilocular collections, multiple abscesses and collections in difficult locations (e.g. presacral space, psoas muscle).
CT or ultrasound is used to define a safe access route avoiding the penetration of major vessels or bowel. Ultrasound is adequate for superficial collections and may be preferable where an angled approach is required, e.g. subphrenic collections (Fig. 2.31). Superficial collections, where there is little risk of misdirection, may be safely drained via a simple one-step trochar catheter system. More complex or deep collections often require the more precise guidance of CT, using the needle guidewire and catheter exchange system originally devised by Seldinger for arterial puncture (Fig. 2.32). Diagnostic fine needle aspiration should be performed before drainage to determine the nature and viscosity of the collection. Nonviscous fluid — ascites, cysts, seromas, biliomas, urinomas — can be satisfactorily drained via an 8—10 French catheter. Thick, inspissated, infected material often requires a larger bore catheter (10—14 French) with multiple side holes and, ideally, a double lumen for cavity irrigation. At catheter insertion, the cavity should be evacuated as completely as possible. Saline irrigation may help to decrease the viscosity of the contents and encourage drainage. Patients should be given broad-spectrum antibiotic cover before and after the procedure. Following catheter placement, regular saline irrigation (10—20 ml tds) is important to maintain catheter patency. The catheter should be left in situ for several days until drainage ceases. Continued drainage of 50 ml or more suggests possible fistulous communication which may be confirmed by a contrast study via the catheter. Prolonged catheter drainage over several weeks may be necessary in such cases to allow fistulae to close. Successful catheter drainage of simple postoperative collections or localised abscesses can be achieved in over 90 per cent of cases. The cure rate for more complex collections such as pancreatic abscesses, abscesses caused by leak from enteric, biliary or urinary anastomosis and thoracic empyaema is lower, between 70 and 85per cent. The multilocular nature of many of these collections makes complete evacuation difficult. However, in many patients percutaneous drainage achieves palliation and allows the patient to undergo delayed, elective, single-stage surgery in a more stable condition with a relatively clean operative bed.
Percutaneous biliary procedures
Drainage of an obstructed biliary system is usually achieved by ERCP.Endoscopic cannulation of the ampulla allows the passage of guidewires and catheters, and the majority of strictures can be bypassed and stented by this approach. In gallstone obstruction of the common bile duct, endoscopic stone removal can be achieved following sphincterotomy by basket retrieval, mechanical lithotripsy or balloon sweepage of the duct. A proportion of patients with obstructive jaundice is not suitable for this endoscopic approach, because of previous gastric surgery, difficulties with cannulation of the ampulla or a tight stricture which cannot be negotiated from below In these patients, a percutaneous transhepatic approach is required. Percutaneous transhepatic cholangiography involves puncture of an intrahepatic bile duct with a fine needle from a right intercostal approach. Successful visualisation of the ducts is achieved in almost all patients with dilated ducts and over 85 per cent of patients with nondilated ducts (Fig. 2.33).
Dilated systems require drainage to reduce the risk of sepsis and relieve jaundice. A peripheral duct with a direct line of approach to the common hepatic duct is chosen for cannulation. Teflon-coated hydrophilic guidewires are particularly useful in traversing even the tightest strictures. Subsequent management depends on the nature of the obstruction demonstrated.
Options include the following:
• balloon dilatation;
• simple external drainage;
• external/internal drainage;
• endoprosthesis — plastic or expanding metal.
Over 90 per cent of benign biliary structures are postoperative, the remainder resulting from sclerosing cholangitis or pancreatitis. If there is biliary sepsis, balloon dilatation should not be attempted until this has been treated with antibiotics and a period of external biliary drainage. A 7—9 French balloon-tipped catheter is placed in the strictured segment with fluoroscopic guidance and the balloon inflated until the ‘waist’ of the balloon within the strictured segment is obliterated. Results suggest that 75—8 0 per cent of strictures will remain patent for at least 3 years.
The majority of biliary strictures is malignant and is due to carcinoma of the pancreas, primary bile duct tumours, nodal enlargement at the porta hepatis or encroachment on the major bile ducts by hepatic metastases. Treatment is aimed at palliation. If there is hilar obstruction, it is usually sufficient to drain only one side of the system as drainage of 30 per cent or more of the liver parenchyma will relieve the obstructing symptoms. If a stricture cannot be bypassed, a catheter may be left in situ with external biliary drainage. This will decompress the system, control the risk of sepsis and will result in resolution of oedema such that a second delayed attempt to traverse the stricture is often successful. A percutaneous catheter is manipulated through the obstruction, into the normal distal common duct or duodenum. Side holes in the catheter that are located above and below the obstruction permit the re-establishment of enterohepatic circulation of bile such that the catheter may be clamped (Fig. 2.34).
An endoprosthesis may be placed into the bile duct to remove the inconvenience of a catheter protruding from the skin and reduce the risks of infection. Percutaneous placement of plastic endoprostheses requires a transhepatic track of 12 French or greater, which carries an increased morbidity (Fig. 2.35).
The recent introduction of self-expanding metallic prostheses means that a smaller percutaneous track is sufficient and the stent can often be inserted immediately without a period of external drainage. Often a percutaneous approach with guidewire manipulation through a stricture is combined with an endoscopic approach. The guidewire is ‘grabbed’ in the duodenum and a stent placed endoscopically. Stent occlusion, by either bile encrustation or tumour ingrowth or overgrowth, remains a problem, although the expanding metal stents have a longer life span than plastic endoprostheses (Fig. 2.36).
Major complications in these patients who generally have severe underlying disease have been observed in 2—5per cent of patients (death, sepsis, haemorrhage).
Minor complications (pain, fever, catheter blockage or leakage) occur in 20—40 per cent of patients.
Gall bladder drainage
Percutaneous gall bladder puncture and drainage may be beneficial in acute calculous or acalculous cholecystitis, or gall bladder empyema in patients who are high risk for surgery or whose medical condition is unstable. The procedure is usually performed under ultrasound guidance. A transhepatic route is advocated to reduce the risk of biliary peritonitis, although a transperitoneal approach is acceptable as the complication rate does not appear to be significantly increased. In severely ill patients the procedure can be performed at the bedside. Ideally, a self-retaining catheter with a locking loop should be left within the gall bladder. In septic patients, recovery is usually rapid and can be followed 2—3 weeks later by elective cholecystectomy. Complications are uncommon although vagal effects (bradycardia and hypotension) do occur and may be treated with atropine and intravenous fluid. Percutaneous gall bladder puncture and aspiration has been advocated in intensive therapy unit (ITU) patients who are pyrexial, without a demonstrable cause, in whom the gall bladder is distended and contains sludge, raising the possibility of acalculous cholecystitis. Approximately 50 per cent of such patients may improve following gall bladder drainage.
Percutaneous renal intervention
Percutaneous drainage of obstructed kidneys, percutaneous nephrostomy, is performed in patients who are septic or in renal failure due to ureteric obstruction by neoplasm, calculi or stricture. Other percutaneous techniques have evolved from this, including antegrade ureteric stent placement, balloon dilatation of ureteric strictures and the creation of a track for percutaneous stone removal (nephrolithotomy) in patients not suitable for lithotripsy.
In a patient presenting with renal failure, it is vital not to miss the presence of bilateral obstruction or an obstructed solitary kidney, and an ultrasound examination is mandatory. The decision to drain the kidney is usually straightforward, particularly in the presence of sepsis. In bilateral obstruction, the better functioning kidney (larger, thicker parenchyma) should be drained first to enable the uraemia and hyperkalaemia to be corrected. If known malignant pelvic disease is resulting in bilateral obstruction, then discussion and consideration of the likely prognosis of the underlying disease process is advisable before proceeding. The indications for percutaneous nephrostomy are shown in (Fig. 2.37. )
Nephrostomy tube placement may be performed under fluoroscopic or ultrasound guidance. The aim is usually to puncture a lower pole calyx rather than a direct central puncture which is more likely to cause vascular damage. A middle calyx approach may be preferred if antegrade stent
Urgent (within 12—24 hours)
• Obstructed infected kidney
• Obstructed solitary kidney with deteriorating renal function
• Obstruction with severe pain
• Obstruction with renal failure
• Pressure—flow studies — obstruction?
• Percutaneous access for stone removal or ureteric procedures, e.g. stent insertion
placement is contemplated. Using a flexible sheathed needle and guidewire with dilatation of the track, final placement of a small pigtail catheter is achieved with minimal trauma to the kidney and discomfort to the patient (Fig. 2.38). The use of self-locking catheters reduces the risk of subsequent catheter dislodgement. Haemorrhage is usually venous and mild, lasting for up to 24 hours. Significant haemorrhage occurs in 1—2 per cent of patients and may occasionally require arteriography to identify a bleeding point or false aneurysm, which may then be treated with selective embolisation. Septic complications occur in 1—2 per cent. They can be minimised by appropriate prophylactic and antibiotic cover and minimising catheter/guidewire manipulation.
Ureteric J-J pigtail stent insertion is usually approachedretrogradely by cystoscopy. It is of value where long-term drainage is required. Indications include calculous obstruction, often in relation to extracorporeal shock wave lithotripsy (ESWL) which produces many small fragments which may block the ureter; benign or malignant ureteric strictures and to allow ureteric perforations to heal. If a retrograde approach fails then an antegrade approach is possible. Most strictures can be traversed with modern flexible hydrophilic guidewires.
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