Percutaneous Nonvascular Procedures

Many of the procedures in Vascular and Interventional Radiology are done outside of the vascular system. Among these are both invasive diagnostic and therapeutic procedures. Many of these procedures, particularly in the biliary system and urinary tract, are performed through catheters, while others are done directly through a percutaneously inserted needle under imaging guidance.

Imaging Guided Biopsy

"There is no part of the human body inaccessible to a strong arm and a 14 gauge needle". While the words of the Fat Man in The House of God are true, interventional radiologists have refined the technique and rarely, if ever, resort to using anything so menacing as a 14 gauge needle. Using imaging guidance (CT, ultrasound or fluoroscopy) and 18 to 22 gauge needles, virtually every tissue outside of the calvarial vault can be biopsied. While fine needle aspiration has been the mainstay of imaging guided percutaneous biopsy, refinements in the design and manufacture of biopsy needles have resulted in devices as small as 21 gauge that routinely obtain both cytology specimens and small cores for histological study.

Imaging guided percutaneous biopsy is used most often for work-up of primary malignancy or metastatic disease in the lung, liver, pancreas, and adrenal glands. Accurate histologic diagnosis can be made in about 85% of malignancies. Nonmalignant lesions are a more difficult problem, and failure to obtain malignant cells on percutaneous biopsy will usually necessitate an open biopsy procedure.

There are few contraindications to percutaneous biopsy. An uncorrected coagulopathy is considered to be the only absolute contraindication for these procedures. Relative contraindications are inability of the patient to cooperate (i.e., lie prone, hold still, suspend respiration) during the procedure, massive ascites in the case of abdominal biopsy, and pulmonary hypertension and bullous disease in the case of lung biopsy.

The primary risk of percutaneous biopsy in the abdomen is hemorrhage. Bleeding complications occur most often with liver biopsy, especially when the lesion is superficial and not covered by normal liver parenchyma. Other complications, such as infection, are very uncommon despite the fact that the needle will occasionally traverse bowel. Seeding of the needle tract with tumor cells is extremely rare except in cases of renal cell carcinoma.

In percutaneous biopsy of the chest, pneumothorax is the most common complication, occurring in about 25% of patients. However, pneumothorax requiring tube thorocostomy occurs in only 10% of percutaneous lung biopsies. Significant hemorrhage from a percutaneous lung biopsy is unusual, although a small amount of hemoptysis will occur in about 5% of cases. A few fatalities from lung biopsy have occurred from puncturing through a tense bulla into an adjacent pulmonary vein. Decompression of the bulla into the vein resulted in nitrogen embolism to the CNS in these cases. Therefore, areas of bullous disease adjacent to the target lung lesion constitute a relative contraindication for percutaneous biopsy.

Nephrostomy

The indications for percutaneous nephrostomy have expanded over the years as advanced interventional and endourological techniques have become available. While percutaneous drainage of an obstructed kidney or ureter is still the most common indication, percutaneous nephrostomy is commonly used for diversion of urine in cases of urinary tract injury, and as a means of access to the urinary tract for stone manipulation and removal, dilatation and stenting of strictures, nephroscopic endopyelotomy for ureteropelvic junction obstruction, laser therapy for urothelial tumors, and a number of other urological problems. Emergency percutaneous nephrostomy may be life saving in cases of urosepsis with obstruction.

The only contraindication to percutaneous nephrostomy is an uncorrected coagulopathy. Patients with bladder outlet or bilateral ureteral obstruction due to malignancy are candidates for nephrostomy drainage. Ultrasound and nuclear medicine studies are useful in such patients to document obstruction, measure residual parenchyma and function, and estimate a prognosis for recovery of function. These studies may also direct salvage efforts to only one kidney and avoid a useless procedure on the contralateral side.

Drainage catheters placed for urinary tract obstruction may be of either the simple nephrostomy or the nephroureterostomy type. Simple nephrostomy catheters, such as the Cope Loop, are 8 to 14 Fr. in size, with multiple sideholes in a pigtail configuration at the catheter tip. A suture passes through the catheter tip and loops back through a proximal sidehole. Traction on the suture forms the pigtail in the renal pelvis. When the suture is either tied or secured in a locking mechanism, the pigtail shape is relatively fixed and thus reduces the risk of accidental dislodgment. Generally, simple nephrostomy catheters are placed initially in all patients referred for urinary obstruction. Depending on the site of obstruction, the nephrostomy catheter may be exchanged later for a nephroureterostomy tube to allow internal drainage to the bladder.

Nephroureterostomy catheters are advanced into the bladder after traversing the renal pelvis and ureter. These catheters have two pigtails segments; a self retaining proximal loop as described above, and a non-retaining distal loop for the bladder. Sideholes are present in both loops and may be present throughout the ureteral portion of the catheter. The primary advantage of a nephroureterostomy catheter is internal drainage which obviates the need for an external collection bag. These catheters also serve as a ureteral stent balloon dilatation of the ureter or endopyelotomy. Finally, these catheters are occasionally placed in externally draining patients who have repeatedly dislodged simple nephrostomy catheters. In such patients a margin of safety is gained by the length of catheter traversing the ureter.

Significant complications from nephrostomy are unusual and occur in less than 5% of patients. Significant complications include hemorrhage requiring transfusion, embolization or operation, renal pelvis perforation with urinoma requiring separate drainage, and severe sepsis. Low to moderate grade fever and blood tinged urine for one to two days following nephrostomy are common minor complications.

Care of a nephrostomy catheter consists of keeping the dressing clean and dry, and by adequately securing the drainage bag. The most common cause of a dislodged nephrostomy catheter is a collection bag that is dropped when full of urine. After 1 week patients may shower with the site covered by plastic wrap, submersion in water should be avoided. Patients are generally kept on PO antibiotics for several days following the initial nephrostomy, and antibiotic coverage should start 2-3 days before, and continue 3 days after a catheter change or other intervention. Good hydration will reduce the rate of salt deposition on and in the catheter. Nevertheless, salt deposition cannot be avoided and catheter changes are required at 3-6 month intervals.

Nephrostomy catheter malfunction will result in a decrease or cessation of urine output. This may be accompanied by leakage around the drainage catheter, flank pain, and/or fever. Any of these signs should be promptly evaluated by nephrostogram and treated with either catheter manipulation or replacement.

Percutaneous Biliary Drainage

Biliary obstruction is a frequent problem in clinical practice. The common etiologies of obstructive jaundice are cholelithiasis, malignancy, and iatrogenic duct injury. In many cases, the area of obstruction can be crossed and stented by endoscopic means. Endoscopic biliary stenting is often unsuccessful in cases of high biliary obstruction and in patients with previous choledochoenteric anastomoses. In cases where endoscopic techniques are unsuccessful, percutaneous biliary drainage (PBD) offers a reliable and safe alternative to surgical management.

PBD is contraindicated only in cases of uncorrected coagulopathy, and moderate to severe ascites. Percutaneous transhepatic cholangiography (PTC) in jaundiced patients should not be done by physicians who lack the training and equipment for completing a drainage procedure. Injection of contrast medium into an obstructed biliary system will frequently result in cholangitis and sepsis if a drainage catheter is not left in place. Similarly, ERCP in the setting of obstructive jaundice may result in biliary sepsis if a stent cannot be placed. ERCP in such patients should only be undertaken in centers having the facilities for PBD.

Major complications of PBD occur in less than 5% of patients, and include biliary or generalized sepsis, bleeding (subcapsular, peritoneal or hemobilia), bile leak with bile peritonitis or biloma formation, and, rarely, pneumothorax or pleural effusion.

PBD can be used for either external or internal drainage of bile, depending on the nature of the occlusion and patency of the bowel distal to the second portion of the duodenum. Initial drainage is always external, even when the obstructing lesion has been crossed with an internal/external drainage catheter. External drainage promotes a more rapid decrease in elevated serum bilirubin levels. The nature of the internal/external drainage catheters is such that, even when opened to external drainage, some portion of the bile will drain internally. This is often a point of confusion for the physician caring for the patient, as decreased external bile output may be interpreted as obstruction of the catheter. Drainage catheter malfunction results in the relatively rapid onset of symptoms which include fever, rigors, and pain. Often there will be bile leakage around the drainage catheter. Any of these signs should prompt an immediate tube cholangiogram with catheter replacement, if necessary.

The PBD tract allows access into the biliary tree for a number of endobiliary procedures. These include balloon dilatation of strictures, insertion of permanent metallic stents, stone manipulation and extraction, biliary duct biopsy, and endoluminal radiation therapy with radioactive seeds. Some cases of stone extraction and stenting require a combined procedure utilizing both interventional radiology and endoscopic techniques.

Care of a biliary drainage catheter is similar to that described for nephrostomy tube. The dressing should be kept clean and dry, and the drainage bag(s) should be adequately secured to prevent dropping. Once the bilirubin level has stabilized, most patients can be placed on internal drainage. Patients may shower after the first week, but the site should be covered with plastic wrap and submersion in water is to be avoided. Patients are generally kept on IV or PO antibiotics for several days following the initial procedure, and antibiotic coverage should start 2-3 days before, and continue 3-5 days after a catheter change or other intervention. Good hydration will reduce the rate of encrustation on and in the catheter. Nevertheless, encrustation cannot be avoided and catheter changes are required at 2-4 month intervals.

Permanent metallic biliary stents have supplanted indwelling drainage catheters in some patients with biliary obstruction. Metallic stents have been available in the U.S. since about 1990. Currently, three such devices have FDA approval: WallStents for malignant obstruction only; Palmaz and Gianturco stents for benign or malignant disease. All of the metallic stents are prone to obstruction. In malignant obstruction, the tumor will eventually overgrow the end of the stent, and may occasionally grow through the stent interstices. In benign conditions the stent lumen will eventually become narrowed by inspissated bile concretions. Recent studies of metallic stents in liver transplant recipients at the University of Nebraska and University of Florida indicate an average patency of less than two years. No metallic stent remained patent after 48 months without some secondary intervention. Therefore, many interventional radiologists reserve these devices for malignant obstruction in patients with limited survival potential.

Abscess Drainage

Abdominal, pelvic, and retroperitoneal abscesses and other abnormal fluid collections are often amenable to percutaneous catheter drainage. Post operative abscesses and collections occur in the pericolic gutters, pelvic cul-de-sac, lesser sac, subphrenic and subhepatic spaces, as interloop collections, and adjacent to incisions. Hepatic abscesses occur as a result of hematogenous spread of pathogens from the GI tract. In pancreatitis, fluid rich in digestive enzymes can penetrate tissue boundaries and result in pseudocysts in diverse locations. Urine and bile leakage following percutaneous or open surgery results in urinoma or biloma formation. Pericolic abscess may develop in cases of diverticulitis. Lymphoceles are relatively common following lower urinary tract or gynecological surgery. Percutaneous drainage of fluid collections and abscesses is done under imaging guidance following many of the technical principles discussed in the section on percutaneous biopsy. That is, imaging guidance is used to insert a small needle (usually 21 gauge) into the collection. However, the technique differs from biopsy in that the needle must not traverse bowel or vital organs in most cases. Two exceptions to this rule are collections in the porta hepatis, which are sometimes drained via a transhepatic route, and noninfected collections in the lesser sac such as pancreatic pseudocyst, which may be drained by a transgastric approach.

Once the collection has been entered with the needle, a small (.018") guide wire is inserted and the needle is removed. A coaxial dilator then allows introduction of a heavier (.038") guide wire over which the remainder of the procedure is done. Drainage catheter selection is dependent on the character of the fluid. Thin serous collections are drained with 6 to 10 Fr. single lumen catheters. Thicker materials require large bore catheters with sump ports, such as the vonSonnenberg catheter. Loculated collections may require several separate catheters for satisfactory drainage. The fluid collections are then aspirated as completely as possible and the drains are connected to bulb suction.

Management of percutaneously placed abscess drains is relatively easy, although the duration of treatment may be prolonged, particularly in cases of GI tract fistulae and pancreatic pseudocyst. Catheter irrigation should be done two or three times per day with small (10-20 cc) volumes of sterile saline. Specific antibiotic coverage should be continued for the duration of treatment.. Once the drainage has decreased to about 10 cc per day, the catheter is backed out slowly over several days to allow the cavity and tract to seal.

Catheter drainage is highly successful for simple fluid collections and abscesses without fistulous connection to bowel. Success in cases of fistulae is variable, requires placement of the catheter tip into the fistula, and is dependent on the underlying disease. Fistulae due to malignancy or inflammatory bowel disease do poorly. Nevertheless, catheter drainage is still useful in such patients in order to avoid the morbidity and mortality of emergency surgery, and allow time to improve the metabolic and nutritional status of the patient prior to definitive therapy.

Placement of a drain for intermittent removal of free abdominal fluid is often requested for patients with both liver failure and malignant ascites. Drains of 6 to 8 Fr. in size having a self retaining pigtail tip are usually sufficient for this purpose. Intermittent gravity drainage to a dependent collection bag may be controlled by a one-way stopcock. Intermittent catheter drainage is also useful in malignant and other recurrent pleural effusions. Either bulb or wall suction, or gravity through a thistle valve (Heimlich valve) to prevent entry of air into the pleural cavity may be used. Multiloculated pleural collections are difficult to treat without surgical intervention. In some cases, urokinase can be instilled into the collection to dissolve the septa if they are composed predominately of fibrin. However, if the septa have become fibrotic, fibrinolytic agents will have little effect.

Percutaneous Gastrostomy

Feeding gastrostomy is useful in many clinical settings where a patient with a functioning GI tract requires nutritional support. Many of the patients requiring gastrostomy suffer from either neurological impairment, mental disorders, or severe esophageal disease including carcinoma.

Gastrostomy tubes may be placed surgically, endoscopically or percutaneously under radiological guidance. The latter is the least invasive method of placement, and can often be done as an outpatient procedure.

Percutaneous gastrostomy entails first passage of a nasogastric catheter. In a patient with a compromised esophagus, a 6 to 8 Fr. pediatric feeding tube will suffice and can often be manipulated down with the aid of a guide wire. Once the NGT is in place, the stomach is insufflated with air. A puncture is made under fluoroscopy through the anterior abdominal wall into the distended stomach. A guide wire is introduced and coiled in the stomach. For a simple gastrostomy, the tract is dilated and the gastrostomy catheter inserted. The gastrostomy tube is placed to low suction for 24-48 hours before tube feeding may commence.

Gastrojejunal (GJ) catheters have certain advantages over simple gastrostomy tubes. These devices are unaffected by impaired gastric emptying, they are more difficult to dislodge, and jejunal feeding reduces the risk of aspiration. Placement of a GJ tube requires a guide wire and catheter to be introduced through the gastrostomy puncture and manipulated across the pylorus, through the duodenum and beyond the ligament of Treitz. Following dilatation of the puncture wound, a sheath is placed and the GJ tube is inserted through the sheath and advanced over the guide wire to the proximal jejunum. Tube feedings may begin immediately following the procedure since the catheter tip is in the proximal jejunum.

For patients with neurologic impairment or other conditions that place them at high risk of aspiration, a double lumen catheter may be used. This catheter has a proximal port in the stomach for aspiration of secretions, and a distal feeding port in the duodenum or proximal jejunum.