Percutaneous Abscess Drainage 

Updated: Aug 03, 2018
Author: Evan J Samett, MD; Chief Editor: Kyung J Cho, MD, FACR, FSIR 

Overview

Background

One definition of an abscess is an infected fluid collection that is drainable. A common dictum is as follows: "If it will not go through a catheter, it cannot be drained; if it is not infected, it is not an abscess."

Differentiating a phlegmon from an abscess can be difficult. A phlegmon may be defined as a vascularized infection that still has perfusion. Some nonsuppurative lymphadenitis may not demonstrate enhancement on imaging studies (eg, computed tomography [CT], magnetic resonance imaging [MRI], or amplitude Doppler ultrasonography [US]), but other collections that do not show central enhancement suggest the presence of an abscess, hematoma, or necrosis.

A phlegmon is an undrainable infection. A viscous abscess without significant debris may be difficult to aspirate through a needle but should be drainable through catheters of appropriate caliber. Irrigation with saline or fibrinolytic agents may be necessary for successful drainage of an abscess with significant debris, blood, or viscous elements.[1]

Percutaneous abscess drainage (PAD),[2]  once revolutionary, has evolved into a routine procedure, replacing open surgical abscess drainage in all but the most difficult or inaccessible cases.[3] It was originally believed that only patients with simple fluid collections were candidates for PAD; however, researchers subsequently demonstrated that both septated and viscous fluid collections could be successfully treated percutaneously, particularly with the adjunctive use of lytic agents. The simpler the abscess, the more likely it is that PAD will be rapidly successful.

An aggressive practical approach with relatively simple devices and techniques may yield a high success rate with few complications.

Technical Considerations

Best practices

Certain basic medicolegal principles apply to all invasive radiology, and thus to PAD as well.[4] Invasive radiology lawsuits are usually related to procedure complications rather than to misdiagnosis. Complaints stem from the following five general causes:

  • Performance of a procedure that was not indicated - It is usually alleged that a less invasive or less risky procedure could have been performed; when appropriate, there should be chart documentation of the indication of the procedure performed (vs alternative approaches) by the radiologist and referring physician
  • Failure to obtain informed consent - The physician must provide the patient with a general understanding of the procedure, its risks and hazards, and the medically acceptable alternatives, and consent for all potential procedures must be obtained in advance before a patient receives sedation-analgesia; for underage or incompetent patients, the responsible consenting person must be known; the physician must recognize when a patient is withdrawing consent during a procedure and comply
  • Failure to perform the procedure in a reasonable manner and deviation from the standard of care - The radiologist should have documentation of adequate training, including a logbook of procedures, successes, and complications, and there should be documentation of adequate training and continuing medical education (CME) for new procedures and technology
  • Failure to promptly recognize and react to a complication - Satisfactory and unsatisfactory results of procedures must be promptly and adequately noted in the chart, and follow-up care should be documented
  • Failure to adequately treat the complication according to an adequate standard of care - The radiologist must be familiar with the recognition and treatment of contrast reactions; basic life support and/or advanced cardiac life support certification should be kept current; there should be documentation of consultations obtained (eg, surgical) in the treatment of complications

Complication prevention

Successful PAD depends on correct initial placement of the drainage device and on the device remaining in place for the duration of treatment. Accordingly, the greatest complication risk for PAD, as for all catheter placement procedures, is catheter dislodgment.

No ideal fixation device or technique is available. Locking sutures on drainage catheters may not reduce the incidence of catheter dislodgment but are indicated for maintaining a catheter in a cavity removed from the access (as in transhepatic cholecystostomy or transrectal pelvic abscess drainage).[5] Torque generated by a patient rolling over in bed overcomes any catheter fixation system. A catheter fixator is merely a catheter position reminder.

The author has had some success using two catheter fixation devices in tandem. However, even this aggressive approach will not prevent all catheter dislodgments. Debilitated, confused, and uncooperative patients are at risk. Patients often do well in a home setting with well-motivated caregivers.

It is important to educate the patient, as well as clinical nursing and physician staff, to monitor the catheter carefully for possible dislodgment. Catheter dislodgment is reflected in a change in the length of catheter visible outside of the patient. When this is noticed, the catheter should be secured to the skin, and radiographs should be obtained for comparison with the baseline study.

Catheter dislodgment may be noticed only when the catheter is leaking (coiled under the bandage) or on the floor. If it is detected early enough (usually < 8 hours), replacement catheters may be placed along the existing tract by using a 5-French dilator, contrast, and a hydrophilic guide wire.

The realities of health care reimbursement and reform have led to patients being discharged from the hospital sooner than before, either to home or skilled nursing facilities. These patients are still in the active phase of PAD but are no longer in a septic state and are cleared for discharge and transfer. As a result, the intensive follow-up that is optimal for abscess resolution may not be as easy to achieve as it once was.

The authors have encountered anecdotal cases of patients returning from skilled nursing facilities with larger, more extensive abscesses than they had when they were discharged. This can be attributed to fragmentation of care, with different teams taking over at each facility. In the best of situations, communication with the new treatment team or outpatient follow-up with the original treatment team continues until abscess resolution.

Outcomes

In a study of CT-guided percutaneous catheter drainage for acute necrotizing pancreatitis, Mortelé et al found that primary CT-guided percutaneous drainage was successful in approximately 50% of patients.[6] The presence of multisystem organ failure appeared to be a more important indicator of outcome than the presence of infection.

In all, 17 of the 35 patients in this study were treated successfully with CT-guided percutaneous catheter drainage alone.[6] The effectiveness of this approach in patients with sterile necrosis was not significantly different from that in patients with infected necrosis. Of 11 patients with multisystem organ failure (10 with sterile necrosis, one with infected necrosis), only four were treated successfully with CT-guided drainage alone; five patients died. Of 24 patients without multisystem organ failure, 13 were treated successfully with CT-guided percutaneous drainage alone; one patient died.

According to Weber et al in a German study, percutaneous transhepatic biliary drainage (PTBD) should be considered the treatment of choice in patients with benign anastomotic stricture after bilioenterostomy, especially after stricturing of a hepatojejunostomy.[7]

Between 1996 and 2006, the authors studied 44 patients with benign anastomotic stricture after bilioenterostomy, and in 27 of the patients (successful treatment, 61.4%), the percutaneous transhepatic biliary drain was successfully removed after 19.9±16.1 months.[7] During follow-up (mean, 53.7 ± 28.4 months after removal of the drain), there was no evidence of recurrent strictures. Permanent drains were necessary in 10 of the 44 patients. In seven of the 44, repeat operation was necessary because of PTBD failure.

Kloek et al compared the outcomes of endoscopic biliary drainage (EBD) and PTBD in 101 patients with resectable hilar cholangiocarcinoma (HCCA) between 2001 and July 2008, 90 of whom underwent EBD and 11 PTBD.[8] The technical success rates were 81% for EBD and 100% for PTBD. Stent dislocation was similar in the EBD and PTBD groups; infectious complications were significantly more common in the EBD group; and patients in the EBD group underwent more drainage procedures and had a significantly longer drainage period until laparotomy. In 30 patients, EBD was converted to PTBD because of EBD failure.

Yamakado et al evaluated the safety, feasibility, and clinical utility of percutaneous transhepatic drainage under real-time CT guidance in 12 patients with inaccessible abdominal abscesses.[9, 10] (Abscesses were considered inaccessible because they were surrounded by the liver and other organs.) In this study, an 8-French catheter was advanced into the abscess cavity through the liver parenchyma. Drainage catheters were placed with no complications in all patients, and all abscesses were drained, shrinking immediately after catheter placement.

Pugmire et al assessed the success rate of PAD for abscesses related to Crohn disease in 25 pediatric patients, paying particular attention to end points relevant to biologic therapy.[11] Success was classified as either technical (ie, catheter placement within the abscess with reduction in abscess size on posttreatment imaging) or clinical (either no surgery within 1 year of drainage or surgical resection following drainage with no residual abscess at surgery or on preoperative imaging). All cases were classified as technical successes, and 19 were considered clinical successes.

Ye et al, in a study comparing the outcomes of posterior and anteroposterior approaches to percutaneous drainage of tubercular psoas abscesses, found that the posterior approach appeared to have the same clinical efficacy as the anteroposterior approach but was associated with a shorter average hospital stay and a lower complication rate.[12]

 

Periprocedural Care

Preprocedural Evaluation

Diagnostic imaging

Occasionally, an abscess is noted as an incidental finding on computed tomography (CT) or ultrasonography (US) in a patient without clear stigmata of sepsis or systemic infection (eg, an older patient with failure to thrive). More often, a diagnostic study is performed for a suspected abscess in a patient with clinical sepsis or infection syndrome (fever and leukocytosis). The patient usually has risk factors for abscess, such as recent surgery, infection, perforated viscous, or immunosuppression.

Serious local infection can be categorized on the basis of location, viscosity, complexity, contents, etiology, or surrounding structures. It can occur in solid organs (eg, liver or muscle),[13, 14] potential spaces (eg, pleural or peritoneal cavity), or in preexisting or physiologic fluid collections or organs (eg, gallbladder or urinary tracts).

Computed tomography and ultrasonography

CT and US are excellent at identifying potential abscess areas. In the proper clinical setting, strong signs are a well-circumscribed fluid collection, thickened membranes or septations, gas bubbles, contrast enhancement, and debris. Weaker signs are nonloculated or thin-walled nonenhancing collections that have alternative pathophysiologic explanations, such as peritoneal or pleural fluid.

The choice between CT and US depends on physician preference and/or issues of logistics or convenience. The availability of multiplanar reformatted (MPR) imaging and CT fluoroscopy, as well as advances in US image quality, make either option excellent in the right hands.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is most useful in identifying abscesses in the musculoskeletal system. Subtle infection from streptococci may cause erysipelas, which usually manifests as a spreading cellulitis. However, deeper infection in the fascia between the subcutaneous tissue and muscle or between muscle layers or at the periosteum also can be associated with streptococci and imaged well with short-axis contrast-enhanced MRI.

MRI is the best way to find intraosseous and subperiosteal abscesses associated with osteomyelitis. CT or US may be needed to determine if a process contains sufficient fluid elements to benefit from percutaneous abscess drainage (PAD).[14]

Categorization of local infection

The spectrum of infected tissue ranges from infected viable organs with no significant degradation of physical integrity to total liquefactive necrosis. Main determinants of ease of drainage are viscosity and complexity (ie, septation, loculation, and debris). Viscosity ranges from near-water to near-solid. Abscess complexity ranges from unilocular to innumerable septations and loculations. Typical examples of complex viscous abscesses include infected pancreatic abscesses or infected retroperitoneal hematomas. These processes are challenging to treat percutaneously and may require multiple interventions over a prolonged recovery period.

Abscesses associated with a perforated bowel (high- and low-flow fistulas) are also challenging to treat. The presence of a low- or high-flow enteric fistula dramatically increases the expected duration of therapy. Successful treatment requires the understanding and cooperation of the patient and referring physician. Knowledge of abscess etiology occasionally may guide therapy. A patient with a history of ruptured viscus is at high risk for enteric organisms. Infection with Echinococcus species must be treated cautiously because of the risk of anaphylaxis.

Viscosity and complexity are difficult to assess with imaging alone. Viscosity cannot be readily predicted unless debris or suspended bubbles are seen. Fine septations are easily missed on CT because of partial volume averaging on routine scans. As an example, a patient had a large intrahepatic pseudocyst infected with fungus. CT demonstrated a simple cyst appearance, a sharply demarcated isodense unilocular collection. US demonstrated innumerable fine septations. The complex nonviscous abscess was successfully treated with PAD.

As another example, a patient with sepsis syndrome had a minimally irregular unilocular abscess appearance on CT. US revealed a well-demarcated hyperechoic mass with central lucency, possibly a hemangioma or necrotic malignancy. The patient was later found to have a perirectal abscess as the source for infection.

Differentiating bowel from pathologic intra-abdominal fluid collections is important. This may be difficult in patients with scant body fat, postsurgical abdomen, or unopacified bowel loops. Multislice spiral CT with gastrointestinal (GI) preparation and intravenous (IV) contrast media is a helpful tool. Thin-slice, coronal, or sagittal reformatted images may help the practitioner understand the anatomy. Delayed or prone imaging with additional oral contrast preparation may be considered in challenging cases. This is particularly true in the frail patient with poor fat-plane differentiation.

Patient selection and preprocedural workup

PAD is generally a safe and effective treatment. The preprocedural evaluation assists procedure planning and risk assessment. Clinical factors increase or decrease complication risks. (See the image below.)

Radiology procedure preassessment form. Radiology procedure preassessment form.

Safe PAD depends on an intact clotting system. In some practices, coagulation abnormalities are sufficiently common that the international normalized ratio (INR), the prothrombin time (PT), and platelet counts are routinely obtained before the procedure.

Bleeding risk depends on the etiology, the degree of coagulopathy, and the reversibility of coagulopathy. The risk is nominal as long as the PT/INR and platelet counts are stable after correction. The risk is increased if coagulopathy recurs quickly. Recurrent or irreversible coagulopathy is caused by synthetic failure (eg, liver or bone marrow) or consumption (eg, hypersplenism or disseminated intravascular coagulation [DIC]).

A common practice is to correct recurrent coagulopathy for the duration of a procedure. A risk of delayed hemorrhage may be present if the coagulopathic state recurs in the early postprocedural period. Anecdotal reports describe of fatal bleeding more than 24 hours after the procedure in this situation. The extensive amount of transfusion required to achieve this level of protection is expensive and burdens blood bank resources. If a patient cannot be treated noninvasively, manage coagulopathy as follows:

  • INR < 1.8 - Perform examination with radiology attending approval, or correct prior to procedure
  • INR ≥1.8 - Correct coagulopathy prior to examination, and verify repeat INR at less than 1.8
  • INR >2.5 - Patients on warfarin or severe liver disease may require 24 hours or more for correction of the INR, depending on the clinical condition and treatment given; adequate correction may be difficult in patients with synthetic failure; patients with severe coagulopathy requiring procedures may need coagulation support after the procedure

Concurrent anticoagulant and/or antithrombotic medication use can also increase risk of bleeding complications. Aspirin and clopidogrel can have clinical effects lasting up to 5 days or longer. Traditional anticoagulants heparin and warfarin have the benefit of an available blood test to monitor therapeutic effects—namely, partial thromboplastin time (PTT) and PT/INR. The newer medications do not have similar clinical assays available, and appropriate clinical correlation is required.

Preprocedural Planning

CT is an excellent modality for planning the PAD access path. Position, angle, and depth can be assessed along with the presence of intervening or adjacent vital structures (eg, bowel, lung, spleen, and liver), which increase the overall risk of PAD.[15] If abscess suspicion is high, and one must traverse intervening structures, then a Seldinger technique may be planned to confirm the presence of an abscess with a needle aspiration before dilating the tract for catheter placement.

US may be used for large or superficial collections or for bedside procedures. Advantages of US include real-time imaging of the needle and catheter path, reduced radiation, and the ability to perform the procedure in the interventional radiology suite in concert with conventional fluoroscopy.

Risk assessment helps determine whether the treatment plan is appropriate and reasonable. Decisions are based on the risk of complication, the expectation of clinical benefit, the overall prognosis, and the availability of treatment alternatives. The more likely it is that a fluid collection is infected, the more likely it is that drainage will be clinically beneficial. One may be less aggressive with nonloculated fluid, such as free ascites or pleural effusion. For these collections, a diagnostic aspiration may be warranted before attempted catheter drainage.

A white blood cell (WBC) count with differential and vital signs helps determine the infection's seriousness. One should consider treatment alternatives when fluid collections are in proximity to vital structures, have a difficult access route, or are found in a severely coagulopathic patient. Neurologic and psychological factors impact a patient's ability to tolerate the procedure without sedation and the risk of postprocedure catheter dislodgment.

Consider medical and surgical treatment alternatives. For example, if an abscess is small and close to or in the spine, the drainage procedure could spread the infection to the cerebrospinal fluid (CSF) and spinal cord. These infections may benefit from an initial trial of IV antibiotics.

A risk-benefit categorization can be adapted from angioplasty guidelines for all invasive procedures. This uses an ordinal scale from 1 through 4 (the higher the number, the less ideal the procedure), as follows:

  • Category 1 - The proposed treatment or procedure is the procedure of choice; a high technical success rate is expected and generally results in complete relief of symptoms or normalization of abnormal clinical conditions or provides diagnostic clinical information
  • Category 2 - Lesions or processes are well suited for the proposed treatment or procedure; a high technical success rate is expected and generally results in complete relief or significant improvement or provides relevant clinical information; this includes lesions and processes that are treated with adjunctive surgery or other modalities
  • Category 3 - Lesions or processes are amenable to the proposed treatment or procedure; a moderate technical success rate is expected, and because of disease severity, type or location, or procedure risk, there is a moderate expectation of obtaining long-term benefit or relevant clinical information; the procedure may be indicated because of other patient risk factors or because of the lack of alternative treatment options
  • Category 4 - The procedure has limited utility because of a low technical success rate, high risk, or poor long-term benefit; the patient has extensive, possibly comorbid disease; the procedure may be indicated in high-risk situations when no treatment alternative is available

Marginal procedures (categories 3 and 4) require close interdisciplinary consultation. Serious clinical conditions warrant an aggressive approach with an attendant increase in risk. Potentially helpful procedures must be differentiated from those with a low expectation of durable clinical benefit. Difficult PAD procedures generally are well tolerated if performed with a minimum of needle passes. Solid organ, even intrasplenic, abscess may be drained. Consider drainage of a high-probability abscess in a salvageable patient with coagulopathy.

Equipment

Needles

Typical abscess fluid is readily aspirated through an 18-gauge needle, which has approximately one 20th the resistance to fluid flow that a 21- to 22-gauge needle does. Viscous or debris-laden fluid is more likely to cause a false-negative aspirate with a 21-gauge needle, in that only clear supernatant may return through the needle. An 18-gauge needle is easier to control and image and accepts a 0.038-in. guide wire. Neff and Accustick sets first require a 0.018-in. mandrel wire followed by a coaxial dilator. The 18-gauge needle costs less than the Neff access set.

There is no clinically significant difference in needle trauma between the 18- and 22-gauge needles when a catheter is placed through the same tract. (This has been demonstrated for arteriotomy.) The 21-gauge needle may be used to minimize trauma for a challenging localization, low-probability fluid collection, or personal preference.

Other supplies

For the trocar technique, all that is required is a trocar-type drainage catheter, a drainage bag, and a minor procedure tray containing preparations, local anesthesia, a scalpel, and draping material. For the Seldinger technique, additional supplies include a guide wire and fascial dilators. Heavy-duty guide wire and hydrophilic dilators with Coons taper (Cook) may be helpful. Careful attention must be paid to securing the PAD catheter.

Drainage catheters and securing devices

The drainage catheter's effectiveness is determined chiefly by its inner diameter and kink resistance. Determine the catheter choice with the needle aspiration test (NAT). If the fluid can be easily aspirated (1 mL in 1 s) by a 10-mL syringe through an 18-gauge needle, then the abscess is drained with the 8.5-French catheter. Gobien and Park's published data support this approach. The catheter may be used for 3-6 months.

Most abscess fluid should pass the NAT. Viscous or debris-laden fluid necessitates the use of larger-diameter catheters: 10-14 French for complex abscesses and 24-30 French for severe pancreatic necrosis. If no significant fluid can be aspirated, biopsy should be considered.

Viscous collections require larger-diameter catheters and more aggressive flushing. Septations may be disrupted with a guide-wire maceration technique once initial drainage subsides. Multiple catheters may be required. Some authors have had success using thrombolytic agents (urokinase, tissue plasminogen activator [t-PA]) for complex abscesses. Thrombolytics may disrupt fibrin and bacterial cell structures.

Commercial drainage catheters come in a wide variety of sizes and materials. Factors to evaluate are cost, comfort, flexibility, ease of tracking (ability to follow the guide wire), kink resistance, inner diameter, side-hole diameter, durability, tip configuration, securing mechanism, and catheter coating.

Most drainage catheters are placed with an inner-stiffening cannula using an over-the-wire technique. There is usually an option to use a traditional metal cannula or a newer flexible plastic cannula. When the metal cannula is used, the catheter-cannula combination is advanced as a unit until the abscess is entered. The cannula is unlocked from the catheter. The catheter is deployed much as an IV catheter: the cannula is held steady while the catheter is advanced into the abscess.

The disadvantage of the metal cannula is that the catheter is more likely to kink once it is disconnected from the cannula. The author prefers to use a flexible plastic cannula that remains connected to the drainage catheter until the final position is achieved. Once the catheter is in place, remove the cannula.

In cost-containment environments, the author has used a custom 35-cm, 7.1-French polyethylene pigtail catheter (Cook). The P7.1-38 series catheter has a 0.062-in. inner lumen and is adequate for most abscess fluids. The catheter is easy to track and has good kink resistance. It is durable enough to use for approximately 2 weeks. It does not have a locking-pigtail suture, which is a minor disadvantage. Its low cost makes it ideal for short-term drainage procedures in cooperative patients or as a bridging catheter in a patient who will undergo multiple treatment stages. This catheter does not have a locking pigtail, and extra care is needed when securing it to avoid accidental dislodgment.

Many drainage catheters come with the option of being deployed as a trocar by putting in an inner stylet. The author uses the trocar technique only for percutaneous cholecystostomy procedures that require a catheter with a small locking loop to facilitate the catheter traversing the often leatherlike gallbladder wall.

With regard to preventing inadvertent catheter dislodgment, the author has had good results using two adhesive-type catheter securing devices in tandem. One is placed where the catheter leaves the skin, and a second is situated closer to the catheter hub if room is available.

Place all extrathoracic drainage catheters to gravity drainage or bulb suction. The author has had good results with the Tru-Close system (Uresil), which comes either with or without a built-in suction bellows. Consider a Pleur-Evac–type device for intrapleural collections to prevent tension pneumothorax. The catheter is flushed at least once per nursing shift with 10-20 mL of normal saline. Adjust the volume and frequency of catheter flush based on cavity size, drainage quality, and quantity.

Guide wires

Various guide wires are available for PAD, with different properties and prices. Guide wires should have the following characteristics:

  • Stiff enough to guide dilators and catheter into abscess
  • Not so stiff as to prevent easy coiling of wire shaft within the abscess
  • Floppy-tipped enough to encourage the wire to coil within the abscess and not perforate the abscess wall
  • Short enough to make use convenient

These requirements usually are satisfied by a 145-cm-long "heavy-duty" stainless steel wire with an outside diameter of 0.038 in., such as the Coons Interventional wire (THSF-38-145-COONS, Cook). Its shaft stiffness is between that of a standard angiographic wire and that of an Amplatz Extra/Super Stiff (Cook/Boston Scientific). It has a long floppy tip and costs less than $20.

Guide-wire stiffness depends on construction, material, and diameter. Stainless steel is cheaper and stiffer than nitinol but does not have nitinol's kink resistance. Wire stiffness is related by the fourth power of the radius. A guide wire's stiffness is derived from the inner mandrel, not the outer wire coiling. Most rigid guide wires are constructed as a solid mandrel with a thin outer coating. Stainless steel Lunderquist Exchange wire (Cook) and the newer nitinol-based Nitrix (EV3) are examples.

 

Technique

Percutaneous Drainage of Abscess

PAD technique

The technique used for percutaneous abscess drainage (PAD) depends on case specifics and personal preference. The location of the fluid collection and the likelihood that it is infected must be taken into account, as well as the patient's overall condition.

The optimum access route is determined by the following:

  • Shortest pathway
  • Easiest angulation or localization
  • Avoidance of intervening or adjacent structures - Bowel (peritonitis risk), vital organs (bleeding risk, especially for the spleen), and sterile pleural effusions (secondary empyema risk)
  • Most convenient catheter location for patient
  • For a solid organ abscess (eg, liver), access path should traverse a small amount of normal organ to reduce the risk of peritoneal spillage and bleeding

Bowel transgression is of concern, particularly when it involves the colon. One may traverse bowel when the alternatives have a higher risk-to-benefit ratio. Bowel transgression is generally tolerated when multiple needle punctures are avoided, and the catheter is left in for at least 2 weeks to create a mature tract. The referring/surgical service should be aware of the increased PAD risk in these situations. One should avoid aspiration of "low-probability" collections through the colon.

PAD is performed by using standard aseptic technique and local lidocaine anesthesia. The procedure begins with a diagnostic aspiration, followed by catheter placement if fluid is purulent. Alternatively, a trocar technique may be used. Simple abscesses smaller than 5 cm in diameter may be treated with aspiration (and lavage) alone.

Localization techniques

The choice of localization technique is influenced by individual and institutional preference. Any modality may be used to assist needle placement.

Computed tomography (CT) fluoroscopy is increasingly available and facilitates "one-stop shopping," allowing diagnostic CT and PAD to be performed readily in a single setting.[16] If CT fluoroscopy is not available, patient assessment may be performed with CT, and the PAD procedure may be performed with ultraonographic (US) localization. Conventional fluoroscopy can be used as an adjunct to US.[17]  US guidance allows real-time imaging and does not involve radiation exposure.[18, 19]

Large abscesses are amenable to "point-and-shoot" US localization. The transducer is manipulated to determine the puncture site, angle, depth, and margin for error. The site is marked by indenting the skin with the hub end of a needle. Entry is memorized, a one-blade-diameter skin incision is made with a No 11 scalpel, and the needle is placed without further imaging.

Real-time US may be used for small or deep abscesses or those that are otherwise difficult to access. A HiLiter needle (Inrad) may assist real-time guidance. In addition, US guidance hardware and software may make a difficult access much easier for those operators who are less experienced at free-hand US guidance.

An 18-gauge, 15-cm trocar needle (DTN-18-15.0, Cook) with an 8.5-French general-purpose locking pigtail catheter (ULT8.5-38-25-P-6S-CLM-RH, Cook) is recommended. A 21- to 22-gauge needle or a 12- to 14-French drainage catheter are not usually required for safety, efficacy, or fluid dynamics. When indicated, the Accustick (Boston Scientific) needle or the Neff Percutaneous Access set (NPAS-100-RB-NT, Cook) may be used. Larger-diameter drainage catheters are available from various vendors. Exceptions include viscous fluids and collections of necrotic tissue such as pancreatic infections or some empyemas.

Pearls

Maintaining guide-wire access

It is critical to never lose guide-wire access during any portion of a drainage procedure. When access is lost, reentry may be difficult because of spontaneous decompression of the abscess or difficulties in imaging from disruption of the region. An advantage of the Accustick system is that it retains the 0.018-in. wire as the 0.038-in. wire is passed. If the larger wire becomes dislodged, then the smaller wire can be used for repeat access.

The author uses Teflon dilators with a Coons modification in which the tip tapers over a length of 5 cm rather than the standard 1 cm. The Coons modification allows the author to use only even-size French dilators. The author always overdilates to the next even dilator size to ease catheter passage.

If it proves difficult to pass the dilator or catheter, the skin incision should be checked first. There may be a remaining strand of subcutaneous connective tissue, or the incision may be too small. The easiest way to assess this is to gently pull back on the dilator or catheter (without losing guide-wire access). If the skin tents up as the catheter is withdrawn, the incision should be enlarged and passage reattempted. Hydrophilic coated dilators are now available (Cook) that greatly ease dilator passage; they use similar technology to that seen in the popular hydrophilic guide wires and are slippery only when wet.

Dealing with resistance to dilator or catheter

When there is resistance to passing the dilator or catheter, the assembly may kink under the skin. This is best determined with fluoroscopy. When it occurs, the wire and catheter should be gently withdrawn as a unit to undo the kink, then readvanced slowly. An assistant should hold the guide wire straight to prevent buckling or accidental withdrawal. The tissues are buttressed with a free hand, the catheter is held close to the skin, and the catheter or dilator is advanced in short firm strokes. This increases the radius of curvature (reducing buckling) and increases the effective rigidity of the unit.

If this fails, either the catheter/dilator or the guide wire must be exchanged. If there is sufficient catheter or dilator in the abscess, then the wire may be exchanged for a more rigid or nitinol variety. If not, the dilator or catheter may be exchanged for a hydrophilic 5-French dilator, whereupon a stiffer wire may be exchanged. Occasionally, either the tract must be balloon-dilated or an alternate access route must be chosen. These issues occur more frequently in scarred areas (eg, in patients who have had multiple nephrostomy procedures).

Postprocedural Care

Management of the patient with an abscess drainage catheter is best performed in a cooperative fashion with referring and surgical services. The quality and quantity of drainage is monitored along with signs of patient recovery. Clinical follow-up care may be augmented by CT, US, fluoroscopy, and plain-film contrast studies if the infection is not resolving. Additional catheter manipulation or placement is based on these results.

Simple abscess treatment usually is complete within 1-2 weeks. A complex abscess or enteric fistula may require weeks to months. Over the course of therapy, catheters may have to be revised, replaced, or repositioned. There are different approaches to post-PAD catheter management. Some prefer to remove the catheter as soon as drainage diminishes below 10 mL/shift. The author prefers to keep the catheter in until the cavity begins to close. Depending on the case, treatment is complete within a matter of days to weeks. Patients usually receive concurrent antibiotic therapy.

Complications

Significant complications of PAD are rare.

One significant complication at the author's institution occurred in a patient with a pancreatic-region abscess when the catheter entered the duodenum. Although the patient did well clinically, the high volume of gastric juice drainage prompted surgery. Given the location of the patient's original abscess, this complication was not unexpected.[18]

Zhang et al reported a case of hepatic rupture occurring as a complication of percutaneous drainage of a pyogenic liver abscess.[20]