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Image-Guided Treatment of Abdominal and Pelvic Abscesses
Author’s Accepted Manuscript Image-Guided Treatment of Abdominal and Pelvic Abscesses Diamanto (Amanda) Rigas, Olga R. Brook
www.elsevier.com/locate/ro
PII: DOI: Reference:
S0037-198X(16)30020-7 http://dx.doi.org/10.1053/j.ro.2016.05.008 YSROE50561
To appear in: Seminars in Roentgenology Cite this article as: Diamanto (Amanda) Rigas and Olga R. Brook, Image-Guided Treatment of Abdominal and Pelvic Abscesses, Seminars in Roentgenology, http://dx.doi.org/10.1053/j.ro.2016.05.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Image-Guided Treatment of Abdominal and Pelvic Abscesses Diamanto (Amanda) Rigas MD, Olga R. Brook MD FSCBTMR Department of Radiology Beth Israel Deaconess Medical Center/Harvard Medical School
Address correspondence to: Olga R. Brook, M.D. Associate Director, CT Services Beth Israel Deaconess Medical Center Assistant Professor of Radiology, Harvard Medical School 1 Deaconess Rd, WCC-3 Boston, MA 02215 Tel: 617-667-1283 E-mail: [email protected]
Image-guided treatment of abdominal and pelvic abscesses Diamanto (Amanda) Rigas, Olga R Brook Introduction Many infectious etiologies may result in abdominal and pelvic fluid collections, such as diverticulitis, appendicitis, pancreatitis, and inflammatory bowel disease, as well as post-surgical states. These collections, usually diagnosed initially by CT or ultrasound, were previously often treated with immediate surgery, which was frequently a complex, multiple-stage procedure associated with high rates of morbidity and mortality. As a safe and effective way to treat these collections with minimal tissue trauma, diminished morbidity and mortality, and shortened hospital stays1-3, percutaneous drainage has become much more common than open surgical drainage. Indeed, a large population study showed that more than 80% of
abdominal abscesses were drained percutaneously in 20134. With appropriate preprocedure planning, percutaneous drainage is an effective and safe treatment approach, with success rates exceeding 90% for simple abscesses5. Proactive postprocedure care also helps to triage catheter-related issues promptly and appropriately. In the patient with an acute inflammatory process, percutaneous catheter drainage can be performed on an emergent basis, allowing definitive surgery to be postposed for several weeks until the patient’s overall condition has improved and focal inflammatory processes have subsided, allowing for safer surgery.
Pre-Procedure Assessment
The following should be considered when evaluating a patient for abscess drainage (see Table 1). The first step is to decide whether there is a drainable fluid collection. Care should be taken to distinguish a fluid collection from a distended bowel loop, which may require oral contrast in the infrequent equivocal case. Once a fluid collection has been documented, the next question is whether it should be drained. Small collections (< 2-3 cm) can frequently be treated with a trial of antibiotics without drainage. A sterile collection, such as a hematoma, should not be drained, because the placement of a catheter introduces skin flora that can colonize a previously sterile collection. However, aspiration for culture of small fluid collections can be helpful to identify the underlying pathogen. The combination of clinical history and specific imaging features, such as a well-defined, enhancing rim
and adjacent fat stranding, can indicate that the collection is infected. Nevertheless, some sterile fluid collections need to be drained because they are producing compressive symptoms of pain and obstruction of adjacent structures. Another important consideration is the complexity of the fluid collection. If it is highly loculated, a single drain is unlikely to achieve optimal drainage. Ultrasound or MRI can demonstrate septations and debris in fluid collections more clearly than CT.
Table 1: Factors to consider when initially evaluating a patient for abscess drainage. Pre Procedure Assessment 1) Is the fluid collection a true collection? Mimickers such as bowel loops should be excluded. 2) Is the fluid collection infected? 3) Is the fluid collection large enough for drainage? 4) Is the collection loculated/septated?
Contraindications Contraindications to percutaneous drainage are mostly relative and should be weighed against the alternatives of surgical drainage and conservative management. Patients should be hemodynamically stable enough to tolerate a procedure and able to assume an appropriate position for drainage and to cooperate as needed. At times, anesthesia support should be sought for procedure monitoring and sedation.
Coagulopathies should be corrected prior to the procedure to minimize the risk of bleeding. According to SIR guidelines,6 abdominal and pelvic drainages carry a moderate risk of bleeding. The recommended pre-preprocedure laboratory testing includes INR (international normalized ratio) in all patients and aPTT (activated partial thromboplastin time) if the patient is receiving intravenous unfractionated heparin. The INR should be corrected to < 1.5. There is no consensus for the aPTT value although some members of the panel argued for correction towards values > 1.5 times control. There is no recommendation for testing the hematocrit or platelet count, though the patient should be transfused if a known platelet count is < 50,000 x 109/L. If the patient is on anticoagulation, the recommendation is to hold clopidogrel for 5 days before the procedure and to withhold one dose of lowmolecular-weight heparin. In an urgent case, drainage can be performed while on clopidogrel, though the higher risk of bleeding should be taken into account. The SIR guidelines do not recommend withholding aspirin (regardless of dose) prior to a procedure.
It is important to exclude pregnancy in all women of childbearing age. The use of CT in a pregnant patient should be limited, and if possible the procedure should be performed under US-guidance. If CT is needed, the radiation dose should be reduced as much as possible.
The only true contraindication to percutaneous catheter drainage is lack of a safe route to the collection. This often can be overcome by utilizing certain techniques that are described below.
Procedure Planning While procedure modality is often dictated by operator preference, if a collection is easily visualized and accessible under ultrasound guidance, this modality generally should be used. Advantages to ultrasound guidance include portability of the ultrasound machine allowing for bedside procedures, real-time visualization, shorter procedure time, and lack of ionizing radiation.
If the collection is not well seen under ultrasound due to a deep location or overlying gas, CT is the preferred modality. The advantages of CT-guidance include good visualization of collections and better post-procedure imaging of the catheter position. In limited cases, such as catheter upsizing or repositioning, traditional fluoroscopy is preferred. Although MRI guidance is available in some institutions for biopsies, this modality is not widely used for drainage of abdominal and pelvic collections.
The appropriate route and patient position should be chosen prior to the arrival of the patient in the procedure suite to facilitate patient, equipment, and staff positioning and reduce pre-procedural time. In most cases, preference is given to the shortest route that avoids traversing vital structures, such as bowel, solid
organs, large vessels, and nerves. If possible, it is better to select a route that allows for a dependent position of the catheter to facilitate drainage. A subcostal approach is preferable to an intercostal approach because it is less likely to violate the parietal pleura and causes less patient discomfort and fewer pleural complications. The pleural reflection crosses the 8th rib anteriorly, the 10th rib laterally, and the 12th rib posteriorly. A recent study found a 26% rate of pleural complications with an intercostal approach and an 8% complication rate with a subcostal approach7. However, the risk of major complications, including empyema and large pneumothorax, was not statistically different between the two groups, so that an intercostal approach can be considered when other routes are limited.
While the route to a collection is often straightforward, certain locations can be challenging to access. One helpful technique is to switch to a blunt-tipped trocar after crossing the peritoneum to avoid puncturing bowel and visceral organs in the path to a collection (Fig 1). However, prior to puncturing a collection, a blunt- tipped trocar must be switched to a sharp-tipped needle to penetrate the collection wall. Curved needles can be used if a collection is inaccessible by a straight path. Gas or fluid also can be used to create a path to a lesion (aerodissection or hydrodissection) 8. While a transhepatic approach can be considered if there is no alternative path, this increases the risk of intra-abdominal bleeding due to the crossing the liver capsule at two sites.
Once the route is chosen, the patient should be appropriately positioned to allow for easy access. Sometimes, a change in patient positioning can result in additional potential routes (Fig 2). For example, placing the patient with the ipsilateral side down during drainage of an upper abdominal collection can assist in compressing the ipsilateral lung, which reduces the risk of pleural transgression. This also can move mobile structures, such as bowel and mesentery, out of the way. Gantry angulation to scan obliquely can be helpful when there are no optimal routes in the axial plane.
Equipment Percutaneous abscess drainage catheters can utilize sump or nonsump design. Sump catheters have a dual lumen, with the outer lumen designed to prevent side holes from becoming blocked when the catheter is adjacent to the wall of an abscess cavity. While these catheters are well suited for draining intra-abdominal abscesses, nonsump catheters with large sideholes are often adequate for drainage. We routinely use nonsump catheters for all drainage procedures with good success. Furthermore, a pigtail locking mechanism is frequently used to prevent catheter dislodgement. Catheters can be placed via either a trocar or Seldinger technique, and the choice of method is often dependent on operator preference. The trocar technique can be safely utilized under ultrasound guidance, as the sharp tip of the catheter is visualized in real-time during catheter placement. Under CT guidance, the Seldinger technique is preferred because it is safer since the imaging is intermittent even with CT fluoroscopy.
Sedation and pain management Sedation and appropriate pain management during the procedure improves patient comfort and cooperation. Moderate sedation, such as fentanyl and midazolam, is commonly utilized for percutaneous abscess drainage, because local anesthesia alone is often insufficient to ensure patient comfort. General anesthesia is usually not required.
Antibiotics Antibiotics often have been initiated by the primary physician prior to the procedure. If not, intravenous antibiotics should be given within an hour prior to a drainage procedure due to the risk of transient bacteremia from catheter placement. The choice of antibiotic ideally should be guided by blood culture results. If these are negative or not available at the time of the procedure, appropriate broadspectrum coverage is recommended. SIR practice guidelines for adult antibiotic prophylaxis can provide guidance9, as can the hospital Infectious Disease team.
Procedure Once the patient is in the procedure suite in the planned position, the first step is to reimage the patient to confirm that the abnormality is still present and accessible via the intended route. The planned entry site on the skin should be marked. A time out should be performed by all members of the team, including the technologist, nurse (if needed), and the radiologist performing the procedure. During the time
out, patient identity is confirmed using three identifiers, and the condition and procedure (including the side, if applicable) are confirmed with the team. Patient allergies are also reviewed, as well as medications stopped or started (including anticoagulants and antibiotics).
The skin of the patient is cleaned and an adequate sterile field created. A generous amount of local anesthesia should be delivered. At this point, the procedure steps differ depending on whether the Seldinger or trocar technique is utilized. With the Seldinger technique, an 18 or 20g needle is used initially to access the collection under continuous direct ultrasound or intermittent CT fluoroscopic guidance. Once in the collection, a sample can be aspirated and sent for laboratory analysis. If the aspirate appears cloudy or purulent on visual inspection, a catheter should be placed. If the aspirate appears clear, the operator can either wait for laboratory analysis or place a catheter at the time of the fluid sampling. Since the collection has already been accessed, there is often placement of a catheter that can be removed later if the collection is not infected. If the decision is made to place a catheter, an 0.035 inch wire is introduced through the needle into the collection. The tract is serially dilated to accommodate the size of the catheter. A risk with the Seldinger technique is loss of access at this time of serial dilations if tension is not held appropriately over the wire. The drainage catheter with a metal or plastic stiffener is advanced over the wire into the collection up to a predefined depth. The stiffener is removed and pigtail formed.
If using the trocar method, the collection is accessed directly with the drainage catheter, a metal stiffening cannula, and a sharp stylet using continuous ultrasound guidance. The trocar technique should be avoided under CT guidance, even with CT fluoroscopy, due to inability to visualize the sharp tip of the stylet in real-time. When the catheter tip is in the collection, the stylet is removed and a small amount of fluid is aspirated to confirm the location of the catheter. The catheter then is deployed over the stiffener into the collection. The stiffener is removed and pigtail formed. The primary disadvantage of this technique is the advancement of a large bore catheter directly into the collection. This may lead to significant complications in cases of inadvertent non-targeted access. Conversely, the trocar technique is quick and safe in experienced hands.
After catheter placement, the collection should be fully aspirated. The area should be reimaged to assess catheter position and any residual collection. The radiologist should search for loculated components that would remain undrained by the existing catheter. The catheter position can be difficult to assess by ultrasound, but a decrease in the size of the collection or its compete collapse indicates appropriate catheter placement.
The catheter should be secured to the skin by a suture or a non-suture fixation device to prevent dislodgement from the collection. A drainage bag or suction bulb is connected to the catheter.
Post-Procedure Management Post-procedure management is as essential as pre-procedure planning. Clear guidance should be provided detailing drain care, including flushing regimens (typically 10 cc, 3-4 times per day). The output of the drain should be recorded daily. A member of the Interventional Radiology team should evaluate the patient daily, to ensure that the drain is still appropriately positioned and secured, the skin around the drain is healthy, and the drain is functioning properly. A decrease in the catheter output could be due to: resolution of the collection; malposition of the drain; thick or loculated collection contents; or obstruction of the drain. Catheter obstruction can be caused by stopcock malfunction, clogging by blood or fibrinous material, kinking of the catheter, or damage to the catheter hub. Flushing the catheter regularly can often resolve clogging. If flushing does not improve the output, imaging is often needed to determine appropriate management. If the collection seems too thick to allow drainage, upsizing the catheter, or instilling fibrinolytics into the collection may resolve the issue. If the catheter output remains high, imaging should be performed to assess for a residual abscess or a fistulous connection to bowel. A bloody appearance of the catheter output may indicate erosion into an adjacent vessel, and this should be evaluated by catheter injection under fluoroscopy or CT.
It is not uncommon for patients to become transiently febrile during or immediately after the procedure, due to transient bacteremia associated with spillage of infected contents into the bloodstream. However, post-procedure fever should improve
within 24 hours after drainage. If the patient remains febrile or tachycardic, it is important to consider the possibility of an untreated infection or undrained collection.
The drain is usually removed within several days after the procedure, when the patient becomes clinically well with normal white cell count and drain output < 1015 cc per day. If the drain output drops but the patient is not well clinically, CT should be performed to evaluate for residual or additional fluid collection.
Complications Complications relating to percutaneous abscess drainage occur in less than 10% of all procedures1,10. A more common complication is transient post-procedure bacteremia; septic shock is rare. The patient should be closely monitored during and especially after the procedure for such signs of transient bacteremia and sepsis, rigors, tachypnea, and altered mental status. Treatment consists of intravenous fluids, intravenous antibiotics, and Demerol (meperidine). If the patient acutely deteriorates, intubation should be considered.
Superinfection of a sterile cavity is considered a major complication, which can result from bowel transgression or, more commonly, contamination with skin flora. Retaining the catheter for prolonged periods can result in local skin infections at the access site. These often can be managed conservatively, but may require removal
and repositioning of the catheter to a new skin entry site. Consultation with wound care specialists can be beneficial in these cases.
Another rare complication is hemorrhage, which may occur as a result of laceration of visceral arteries or such solid organs as the liver or spleen. The most sensitive indicator of intra-abdominal hemorrhage is pain, but this is very nonspecific. When there is a clinical suspicion for bleeding, hemodynamic stability should be assessed immediately. Frequently, cross sectional imaging (such as CT) is required to determine the cause of the bleeding and the best treatment approach. While hemorrhage from small vessels is often self-limited, there sometimes is need for blood transfusion. More significant hemorrhage can be treated by upsizing of the tube. In severe cases, transcatheter arterial embolization may be needed. Correcting any coagulopathy and careful attention to the safest route possible minimizes the risk of bleeding.
A subcostal or low intercostal approach should be used whenever possible to avoid pleural transgression, which can result in pneumothorax and contamination of pleural cavity with abscess contents. These complications can be treated by placement of a chest tube.
Non-target catheterization or traversal of the intestine, liver, and spleen has been reported. Oral contrast can identify bowel, but its use during the procedure precludes employing moderate sedation. Therefore, prior imaging with oral contrast
should be carefully evaluated. Administration of intravenous contrast during the procedure can be used to delineate difficult anatomy. Inadvertent catheter placement through the small bowel can be recognized by high output of bowel contents from the catheter, but this complication rarely needs surgical management. Conversely, a drain traversing the colon puts the patient at risk for peritonitis and sepsis and often requires surgery. Conservative measures such as bowel rest and broad-spectrum antibiotics should be attempted in stable patients, regardless of whether the small or large bowel is traversed. After several weeks to allow a mature tract to form, the catheter can be safely removed. Catheter placement through a solid parenchymal organ carries minimal risk and can be treated with tract embolization upon catheter removal.
Special Circumstances Refractory Collections Persistent fluid collections that are refractory to percutaneous catheter drainage may be due to septations within a complex fluid collection. In this setting, multiple catheters can be used to assist with drainage. A Bentson wire is sometimes successful in breaking septations within the collection. Viscous contents may impede adequate drainage despite appropriate catheter sizing. In these situations, fibrinolytic agents may be introduced into the cavity via the drainage catheter11. Tissue plasminogen activator (tPA) has largely replaced streptokinase and urokinase for this purpose and has been shown to improve drainage of abdominal and pelvic abscesses. A large study used 4-6 mg of tPA diluted in 25 ml of 0.9%
saline administered through the catheter, which was clamped for 30 minutes and then opened to gravity drainage. This was performed several times per day for several days. Efficacy rates of intracavitary thrombolysis for refractory fluid collections are almost 90%12. Complications are rare, and there does not appear to be an increased risk of bleeding in patients already on systemic anticoagulation.
Abscess-Fistula Complex More than 75% of abscess-fistula complexes result from surgery, endoscopy, or minimally invasive procedures13. Fistulas most commonly occur from the bowel, but can also originate from the bladder, pancreatic duct, or bile duct. Persistently high outputs (> 100 cc per day), or an increase in output several days after catheter placement, should raise suspicion for the presence of a fistula, which can be confirmed by the injection of contrast into the catheter under fluoroscopy or CT. Low-output abscess-fistula complexes, which have an output of < 200 cc per day, have a colonic origin, and drainage with bowel rest is often sufficient for fistula healing.
In high-output abscess-fistula complexes, which usually originate from the small bowel, the abscess catheter should be placed into the fistula when possible. The proximal bowel contents should be diverted, usually by nasogastric tube, and the patient put on bowel rest. Fluid and electrolyte imbalances should be corrected to promote fistula healing, which may require weeks to months. In these cases, the patient is discharged with the catheter in place and re-evaluated with fluoroscopy
every few weeks to determine whether the fistula persists. When the drainage slows to less than 30-40 cc/day, the catheter can slowly be withdrawn. Before completely removing the drain, the catheter should be clamped for 2-3 days, followed by CT to assess for re-accumulation of the abscess due to persistent fistula. Use of a fistula closure device may be considered, especially when a shorter indwelling catheter time is desired. High-output fistulas are less likely to heal successfully than lowoutput abscess-fistula complexes.
Pancreatic Collections Pancreatic collections also pose unique challenges, requiring a multidisciplinary approach for appropriate management. These collections can be difficult to access due to surrounding vital structures, and some collections are more easily drained by an endoscopic route with creation of a cyst gastrostomy rather than a percutaneous route. In certain cases, surgery is indicated. Pancreatic collections also can pose diagnostic challenges, since the various types require different treatment strategies14. According to the Revised Atlanta classification15, acute peripancreatic fluid collections do not require any intervention. Pseudocysts often resolve spontaneously, but catheter drainage may be considered in they are > 5 cm, increasing in size, or causing obstructive symptoms or pain. Walled-off pancreatic necrosis can be drained percutaneously, especially if sterile. However, infected necrosis, considered the most severe complication of pancreatitis, is traditionally treated with surgical debridement. Percutaneous drainage can be attempted, but
frequently is insufficient due to blockage of the catheter by necrotic material. Largebore catheters (up to 20Fr) should be used with frequent flushings.
Conclusions Percutaneous drainage is considered the first-line treatment for abdominal and pelvic fluid collections. Percutaneous abscess drainage has transformed patient care, improving outcomes for many patients by precluding the need for them to undergo complex surgical procedures.
References
1. Campbell JJ, Gervais DA: Percutaneous Abscess Drainage Within the Abdomen and Pelvis in Mauro MA, Murphy KPJ, Thomson KR, et al (eds) Image-Guided Interventions. Philadelphia, PA, Saunders, 2013, pp 923-931. 2. Lee MJ: Percutaneous Abscess and Fluid Drainage in Kaufman JA, Lee M (eds) Vascular and Interventional Radiology Requisites. Philadelphia, PA, Saunders, 2013, pp 401-424. 3. Lorenz T, Thomas JL: Complications of Percutaneous Drainage. Semin IR 23:194-204, 2006. 4. Levin DC, Eschelman D, Parker L: Trends in Use of Percutaneous Versus Open Surgical Drainage of Abdominal Abscesses. JACR 12:1247-1250, 2015. 5. VanSonnenberg E, Wittich GR, Goodacre BW: Percutaneous Abscess Drainage: Update. World J Surg 25:362-372, 2001. 6. Patel IJ, Davidson JC, Nikolic B: Consensus Guidelines for Periprocedural Management of Coagulation Status and Hemostasis Risk in percutaneous Image-guided Interventions. 23:727-726, 2012. 7. Preece SR, Nelson RC, Bashir MR: Safety of an Intercostal Approach for Image-Guided Percutaneous Drainage of Subdiaphragmatic Abscesses. AJR 202:1349-1354, 2014. 8. McDermott S, Levis DA, Arellano RS: Approaches to the Difficult Drainage and Biopsy. Semin in IR 29:256-263, 2012.
9. Venkatesan AM, Kundu S, Sacks D: Practice Guideline for Adult Antibiotic Prophylaxis during Vascular and Interventional Radiology Procedures. J Vasc Interv Radiol 21:1611-1630, 2010. 10. Shahnazi M, Khatami A, Jamzad A: Safety and Efficacy of Percutaneous CTGuided Drainage in the Management of Abdominopelvic Abscess. Iran J Radiol 11:1-4, 2014. 11. Shenoy-Bhangle AS, Gervais DA: Use of Fibrinolytics in Abdominal and Pleural Collections. Seminars in Interventional Radiology 29:264-269, 2012. 12. Beland MD, Gervais, DA, Levis, DA: Complex Abdominal and Pelvic Abscesses: Efficacy of Adjunctive Tissue-Type Plasminogen Activator for Drainage. Radiology 247:567-573, 2008. 13. Ballard DH, Jahromi AH, Li AY: Abscess-Fistula Complexes: A Systematic Approach for Percutaneous Catheter Management. J Vasc Interv Radiol 26:1363-1367, 2015. 14. Pryluck DS, Singh CK, Clark TWI: Management of Fluid Collections in Acute Pancreatitis in Mauro MA, Murphy KPJ, Thomson KR, et al (eds) ImageGuided Interventions. Philadelphia, PA, Saunders, 2013, pp 932-936. 15. Thoeni, R: Revised Atlanta Classification of Acute Pancreatitis: Its Importance for the Radiologist and Its Effect on Treatment. Radiology 262:751-764, 2012.
Figure 1
C
C
B
C
W
Fig. 1. A. Peripancreatic fluid collection. Axial contrast-enhanced CT shows the collection (C) with a surgical JP drain in place, which was not draining fluid. B. Preprocedure noncontrast image with the patient supine shows a small window to access the collection percutaneously. C. The blunt stylet (B) was used in the retroperitoneum to avoid injury to the left kidney. D. Final image shows the catheter and wire in the collection.
Figure 2
D C
A
Fig. 2. Right lower quadrant abscess. A: Axial image demonstrates a thick-walled, fluid-containing abscess (A), with colon anteriorly (C), preventing an anterior approach for access. B: By placing the patient in a left lateral decubitus position, this bowel loop moved out of the way, allowing for an anterior approach for drain placement (D).
www.elsevier.com/locate/ro
PII: DOI: Reference:
S0037-198X(16)30020-7 http://dx.doi.org/10.1053/j.ro.2016.05.008 YSROE50561
To appear in: Seminars in Roentgenology Cite this article as: Diamanto (Amanda) Rigas and Olga R. Brook, Image-Guided Treatment of Abdominal and Pelvic Abscesses, Seminars in Roentgenology, http://dx.doi.org/10.1053/j.ro.2016.05.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Image-Guided Treatment of Abdominal and Pelvic Abscesses Diamanto (Amanda) Rigas MD, Olga R. Brook MD FSCBTMR Department of Radiology Beth Israel Deaconess Medical Center/Harvard Medical School
Address correspondence to: Olga R. Brook, M.D. Associate Director, CT Services Beth Israel Deaconess Medical Center Assistant Professor of Radiology, Harvard Medical School 1 Deaconess Rd, WCC-3 Boston, MA 02215 Tel: 617-667-1283 E-mail: [email protected]
Image-guided treatment of abdominal and pelvic abscesses Diamanto (Amanda) Rigas, Olga R Brook Introduction Many infectious etiologies may result in abdominal and pelvic fluid collections, such as diverticulitis, appendicitis, pancreatitis, and inflammatory bowel disease, as well as post-surgical states. These collections, usually diagnosed initially by CT or ultrasound, were previously often treated with immediate surgery, which was frequently a complex, multiple-stage procedure associated with high rates of morbidity and mortality. As a safe and effective way to treat these collections with minimal tissue trauma, diminished morbidity and mortality, and shortened hospital stays1-3, percutaneous drainage has become much more common than open surgical drainage. Indeed, a large population study showed that more than 80% of
abdominal abscesses were drained percutaneously in 20134. With appropriate preprocedure planning, percutaneous drainage is an effective and safe treatment approach, with success rates exceeding 90% for simple abscesses5. Proactive postprocedure care also helps to triage catheter-related issues promptly and appropriately. In the patient with an acute inflammatory process, percutaneous catheter drainage can be performed on an emergent basis, allowing definitive surgery to be postposed for several weeks until the patient’s overall condition has improved and focal inflammatory processes have subsided, allowing for safer surgery.
Pre-Procedure Assessment
The following should be considered when evaluating a patient for abscess drainage (see Table 1). The first step is to decide whether there is a drainable fluid collection. Care should be taken to distinguish a fluid collection from a distended bowel loop, which may require oral contrast in the infrequent equivocal case. Once a fluid collection has been documented, the next question is whether it should be drained. Small collections (< 2-3 cm) can frequently be treated with a trial of antibiotics without drainage. A sterile collection, such as a hematoma, should not be drained, because the placement of a catheter introduces skin flora that can colonize a previously sterile collection. However, aspiration for culture of small fluid collections can be helpful to identify the underlying pathogen. The combination of clinical history and specific imaging features, such as a well-defined, enhancing rim
and adjacent fat stranding, can indicate that the collection is infected. Nevertheless, some sterile fluid collections need to be drained because they are producing compressive symptoms of pain and obstruction of adjacent structures. Another important consideration is the complexity of the fluid collection. If it is highly loculated, a single drain is unlikely to achieve optimal drainage. Ultrasound or MRI can demonstrate septations and debris in fluid collections more clearly than CT.
Table 1: Factors to consider when initially evaluating a patient for abscess drainage. Pre Procedure Assessment 1) Is the fluid collection a true collection? Mimickers such as bowel loops should be excluded. 2) Is the fluid collection infected? 3) Is the fluid collection large enough for drainage? 4) Is the collection loculated/septated?
Contraindications Contraindications to percutaneous drainage are mostly relative and should be weighed against the alternatives of surgical drainage and conservative management. Patients should be hemodynamically stable enough to tolerate a procedure and able to assume an appropriate position for drainage and to cooperate as needed. At times, anesthesia support should be sought for procedure monitoring and sedation.
Coagulopathies should be corrected prior to the procedure to minimize the risk of bleeding. According to SIR guidelines,6 abdominal and pelvic drainages carry a moderate risk of bleeding. The recommended pre-preprocedure laboratory testing includes INR (international normalized ratio) in all patients and aPTT (activated partial thromboplastin time) if the patient is receiving intravenous unfractionated heparin. The INR should be corrected to < 1.5. There is no consensus for the aPTT value although some members of the panel argued for correction towards values > 1.5 times control. There is no recommendation for testing the hematocrit or platelet count, though the patient should be transfused if a known platelet count is < 50,000 x 109/L. If the patient is on anticoagulation, the recommendation is to hold clopidogrel for 5 days before the procedure and to withhold one dose of lowmolecular-weight heparin. In an urgent case, drainage can be performed while on clopidogrel, though the higher risk of bleeding should be taken into account. The SIR guidelines do not recommend withholding aspirin (regardless of dose) prior to a procedure.
It is important to exclude pregnancy in all women of childbearing age. The use of CT in a pregnant patient should be limited, and if possible the procedure should be performed under US-guidance. If CT is needed, the radiation dose should be reduced as much as possible.
The only true contraindication to percutaneous catheter drainage is lack of a safe route to the collection. This often can be overcome by utilizing certain techniques that are described below.
Procedure Planning While procedure modality is often dictated by operator preference, if a collection is easily visualized and accessible under ultrasound guidance, this modality generally should be used. Advantages to ultrasound guidance include portability of the ultrasound machine allowing for bedside procedures, real-time visualization, shorter procedure time, and lack of ionizing radiation.
If the collection is not well seen under ultrasound due to a deep location or overlying gas, CT is the preferred modality. The advantages of CT-guidance include good visualization of collections and better post-procedure imaging of the catheter position. In limited cases, such as catheter upsizing or repositioning, traditional fluoroscopy is preferred. Although MRI guidance is available in some institutions for biopsies, this modality is not widely used for drainage of abdominal and pelvic collections.
The appropriate route and patient position should be chosen prior to the arrival of the patient in the procedure suite to facilitate patient, equipment, and staff positioning and reduce pre-procedural time. In most cases, preference is given to the shortest route that avoids traversing vital structures, such as bowel, solid
organs, large vessels, and nerves. If possible, it is better to select a route that allows for a dependent position of the catheter to facilitate drainage. A subcostal approach is preferable to an intercostal approach because it is less likely to violate the parietal pleura and causes less patient discomfort and fewer pleural complications. The pleural reflection crosses the 8th rib anteriorly, the 10th rib laterally, and the 12th rib posteriorly. A recent study found a 26% rate of pleural complications with an intercostal approach and an 8% complication rate with a subcostal approach7. However, the risk of major complications, including empyema and large pneumothorax, was not statistically different between the two groups, so that an intercostal approach can be considered when other routes are limited.
While the route to a collection is often straightforward, certain locations can be challenging to access. One helpful technique is to switch to a blunt-tipped trocar after crossing the peritoneum to avoid puncturing bowel and visceral organs in the path to a collection (Fig 1). However, prior to puncturing a collection, a blunt- tipped trocar must be switched to a sharp-tipped needle to penetrate the collection wall. Curved needles can be used if a collection is inaccessible by a straight path. Gas or fluid also can be used to create a path to a lesion (aerodissection or hydrodissection) 8. While a transhepatic approach can be considered if there is no alternative path, this increases the risk of intra-abdominal bleeding due to the crossing the liver capsule at two sites.
Once the route is chosen, the patient should be appropriately positioned to allow for easy access. Sometimes, a change in patient positioning can result in additional potential routes (Fig 2). For example, placing the patient with the ipsilateral side down during drainage of an upper abdominal collection can assist in compressing the ipsilateral lung, which reduces the risk of pleural transgression. This also can move mobile structures, such as bowel and mesentery, out of the way. Gantry angulation to scan obliquely can be helpful when there are no optimal routes in the axial plane.
Equipment Percutaneous abscess drainage catheters can utilize sump or nonsump design. Sump catheters have a dual lumen, with the outer lumen designed to prevent side holes from becoming blocked when the catheter is adjacent to the wall of an abscess cavity. While these catheters are well suited for draining intra-abdominal abscesses, nonsump catheters with large sideholes are often adequate for drainage. We routinely use nonsump catheters for all drainage procedures with good success. Furthermore, a pigtail locking mechanism is frequently used to prevent catheter dislodgement. Catheters can be placed via either a trocar or Seldinger technique, and the choice of method is often dependent on operator preference. The trocar technique can be safely utilized under ultrasound guidance, as the sharp tip of the catheter is visualized in real-time during catheter placement. Under CT guidance, the Seldinger technique is preferred because it is safer since the imaging is intermittent even with CT fluoroscopy.
Sedation and pain management Sedation and appropriate pain management during the procedure improves patient comfort and cooperation. Moderate sedation, such as fentanyl and midazolam, is commonly utilized for percutaneous abscess drainage, because local anesthesia alone is often insufficient to ensure patient comfort. General anesthesia is usually not required.
Antibiotics Antibiotics often have been initiated by the primary physician prior to the procedure. If not, intravenous antibiotics should be given within an hour prior to a drainage procedure due to the risk of transient bacteremia from catheter placement. The choice of antibiotic ideally should be guided by blood culture results. If these are negative or not available at the time of the procedure, appropriate broadspectrum coverage is recommended. SIR practice guidelines for adult antibiotic prophylaxis can provide guidance9, as can the hospital Infectious Disease team.
Procedure Once the patient is in the procedure suite in the planned position, the first step is to reimage the patient to confirm that the abnormality is still present and accessible via the intended route. The planned entry site on the skin should be marked. A time out should be performed by all members of the team, including the technologist, nurse (if needed), and the radiologist performing the procedure. During the time
out, patient identity is confirmed using three identifiers, and the condition and procedure (including the side, if applicable) are confirmed with the team. Patient allergies are also reviewed, as well as medications stopped or started (including anticoagulants and antibiotics).
The skin of the patient is cleaned and an adequate sterile field created. A generous amount of local anesthesia should be delivered. At this point, the procedure steps differ depending on whether the Seldinger or trocar technique is utilized. With the Seldinger technique, an 18 or 20g needle is used initially to access the collection under continuous direct ultrasound or intermittent CT fluoroscopic guidance. Once in the collection, a sample can be aspirated and sent for laboratory analysis. If the aspirate appears cloudy or purulent on visual inspection, a catheter should be placed. If the aspirate appears clear, the operator can either wait for laboratory analysis or place a catheter at the time of the fluid sampling. Since the collection has already been accessed, there is often placement of a catheter that can be removed later if the collection is not infected. If the decision is made to place a catheter, an 0.035 inch wire is introduced through the needle into the collection. The tract is serially dilated to accommodate the size of the catheter. A risk with the Seldinger technique is loss of access at this time of serial dilations if tension is not held appropriately over the wire. The drainage catheter with a metal or plastic stiffener is advanced over the wire into the collection up to a predefined depth. The stiffener is removed and pigtail formed.
If using the trocar method, the collection is accessed directly with the drainage catheter, a metal stiffening cannula, and a sharp stylet using continuous ultrasound guidance. The trocar technique should be avoided under CT guidance, even with CT fluoroscopy, due to inability to visualize the sharp tip of the stylet in real-time. When the catheter tip is in the collection, the stylet is removed and a small amount of fluid is aspirated to confirm the location of the catheter. The catheter then is deployed over the stiffener into the collection. The stiffener is removed and pigtail formed. The primary disadvantage of this technique is the advancement of a large bore catheter directly into the collection. This may lead to significant complications in cases of inadvertent non-targeted access. Conversely, the trocar technique is quick and safe in experienced hands.
After catheter placement, the collection should be fully aspirated. The area should be reimaged to assess catheter position and any residual collection. The radiologist should search for loculated components that would remain undrained by the existing catheter. The catheter position can be difficult to assess by ultrasound, but a decrease in the size of the collection or its compete collapse indicates appropriate catheter placement.
The catheter should be secured to the skin by a suture or a non-suture fixation device to prevent dislodgement from the collection. A drainage bag or suction bulb is connected to the catheter.
Post-Procedure Management Post-procedure management is as essential as pre-procedure planning. Clear guidance should be provided detailing drain care, including flushing regimens (typically 10 cc, 3-4 times per day). The output of the drain should be recorded daily. A member of the Interventional Radiology team should evaluate the patient daily, to ensure that the drain is still appropriately positioned and secured, the skin around the drain is healthy, and the drain is functioning properly. A decrease in the catheter output could be due to: resolution of the collection; malposition of the drain; thick or loculated collection contents; or obstruction of the drain. Catheter obstruction can be caused by stopcock malfunction, clogging by blood or fibrinous material, kinking of the catheter, or damage to the catheter hub. Flushing the catheter regularly can often resolve clogging. If flushing does not improve the output, imaging is often needed to determine appropriate management. If the collection seems too thick to allow drainage, upsizing the catheter, or instilling fibrinolytics into the collection may resolve the issue. If the catheter output remains high, imaging should be performed to assess for a residual abscess or a fistulous connection to bowel. A bloody appearance of the catheter output may indicate erosion into an adjacent vessel, and this should be evaluated by catheter injection under fluoroscopy or CT.
It is not uncommon for patients to become transiently febrile during or immediately after the procedure, due to transient bacteremia associated with spillage of infected contents into the bloodstream. However, post-procedure fever should improve
within 24 hours after drainage. If the patient remains febrile or tachycardic, it is important to consider the possibility of an untreated infection or undrained collection.
The drain is usually removed within several days after the procedure, when the patient becomes clinically well with normal white cell count and drain output < 1015 cc per day. If the drain output drops but the patient is not well clinically, CT should be performed to evaluate for residual or additional fluid collection.
Complications Complications relating to percutaneous abscess drainage occur in less than 10% of all procedures1,10. A more common complication is transient post-procedure bacteremia; septic shock is rare. The patient should be closely monitored during and especially after the procedure for such signs of transient bacteremia and sepsis, rigors, tachypnea, and altered mental status. Treatment consists of intravenous fluids, intravenous antibiotics, and Demerol (meperidine). If the patient acutely deteriorates, intubation should be considered.
Superinfection of a sterile cavity is considered a major complication, which can result from bowel transgression or, more commonly, contamination with skin flora. Retaining the catheter for prolonged periods can result in local skin infections at the access site. These often can be managed conservatively, but may require removal
and repositioning of the catheter to a new skin entry site. Consultation with wound care specialists can be beneficial in these cases.
Another rare complication is hemorrhage, which may occur as a result of laceration of visceral arteries or such solid organs as the liver or spleen. The most sensitive indicator of intra-abdominal hemorrhage is pain, but this is very nonspecific. When there is a clinical suspicion for bleeding, hemodynamic stability should be assessed immediately. Frequently, cross sectional imaging (such as CT) is required to determine the cause of the bleeding and the best treatment approach. While hemorrhage from small vessels is often self-limited, there sometimes is need for blood transfusion. More significant hemorrhage can be treated by upsizing of the tube. In severe cases, transcatheter arterial embolization may be needed. Correcting any coagulopathy and careful attention to the safest route possible minimizes the risk of bleeding.
A subcostal or low intercostal approach should be used whenever possible to avoid pleural transgression, which can result in pneumothorax and contamination of pleural cavity with abscess contents. These complications can be treated by placement of a chest tube.
Non-target catheterization or traversal of the intestine, liver, and spleen has been reported. Oral contrast can identify bowel, but its use during the procedure precludes employing moderate sedation. Therefore, prior imaging with oral contrast
should be carefully evaluated. Administration of intravenous contrast during the procedure can be used to delineate difficult anatomy. Inadvertent catheter placement through the small bowel can be recognized by high output of bowel contents from the catheter, but this complication rarely needs surgical management. Conversely, a drain traversing the colon puts the patient at risk for peritonitis and sepsis and often requires surgery. Conservative measures such as bowel rest and broad-spectrum antibiotics should be attempted in stable patients, regardless of whether the small or large bowel is traversed. After several weeks to allow a mature tract to form, the catheter can be safely removed. Catheter placement through a solid parenchymal organ carries minimal risk and can be treated with tract embolization upon catheter removal.
Special Circumstances Refractory Collections Persistent fluid collections that are refractory to percutaneous catheter drainage may be due to septations within a complex fluid collection. In this setting, multiple catheters can be used to assist with drainage. A Bentson wire is sometimes successful in breaking septations within the collection. Viscous contents may impede adequate drainage despite appropriate catheter sizing. In these situations, fibrinolytic agents may be introduced into the cavity via the drainage catheter11. Tissue plasminogen activator (tPA) has largely replaced streptokinase and urokinase for this purpose and has been shown to improve drainage of abdominal and pelvic abscesses. A large study used 4-6 mg of tPA diluted in 25 ml of 0.9%
saline administered through the catheter, which was clamped for 30 minutes and then opened to gravity drainage. This was performed several times per day for several days. Efficacy rates of intracavitary thrombolysis for refractory fluid collections are almost 90%12. Complications are rare, and there does not appear to be an increased risk of bleeding in patients already on systemic anticoagulation.
Abscess-Fistula Complex More than 75% of abscess-fistula complexes result from surgery, endoscopy, or minimally invasive procedures13. Fistulas most commonly occur from the bowel, but can also originate from the bladder, pancreatic duct, or bile duct. Persistently high outputs (> 100 cc per day), or an increase in output several days after catheter placement, should raise suspicion for the presence of a fistula, which can be confirmed by the injection of contrast into the catheter under fluoroscopy or CT. Low-output abscess-fistula complexes, which have an output of < 200 cc per day, have a colonic origin, and drainage with bowel rest is often sufficient for fistula healing.
In high-output abscess-fistula complexes, which usually originate from the small bowel, the abscess catheter should be placed into the fistula when possible. The proximal bowel contents should be diverted, usually by nasogastric tube, and the patient put on bowel rest. Fluid and electrolyte imbalances should be corrected to promote fistula healing, which may require weeks to months. In these cases, the patient is discharged with the catheter in place and re-evaluated with fluoroscopy
every few weeks to determine whether the fistula persists. When the drainage slows to less than 30-40 cc/day, the catheter can slowly be withdrawn. Before completely removing the drain, the catheter should be clamped for 2-3 days, followed by CT to assess for re-accumulation of the abscess due to persistent fistula. Use of a fistula closure device may be considered, especially when a shorter indwelling catheter time is desired. High-output fistulas are less likely to heal successfully than lowoutput abscess-fistula complexes.
Pancreatic Collections Pancreatic collections also pose unique challenges, requiring a multidisciplinary approach for appropriate management. These collections can be difficult to access due to surrounding vital structures, and some collections are more easily drained by an endoscopic route with creation of a cyst gastrostomy rather than a percutaneous route. In certain cases, surgery is indicated. Pancreatic collections also can pose diagnostic challenges, since the various types require different treatment strategies14. According to the Revised Atlanta classification15, acute peripancreatic fluid collections do not require any intervention. Pseudocysts often resolve spontaneously, but catheter drainage may be considered in they are > 5 cm, increasing in size, or causing obstructive symptoms or pain. Walled-off pancreatic necrosis can be drained percutaneously, especially if sterile. However, infected necrosis, considered the most severe complication of pancreatitis, is traditionally treated with surgical debridement. Percutaneous drainage can be attempted, but
frequently is insufficient due to blockage of the catheter by necrotic material. Largebore catheters (up to 20Fr) should be used with frequent flushings.
Conclusions Percutaneous drainage is considered the first-line treatment for abdominal and pelvic fluid collections. Percutaneous abscess drainage has transformed patient care, improving outcomes for many patients by precluding the need for them to undergo complex surgical procedures.
References
1. Campbell JJ, Gervais DA: Percutaneous Abscess Drainage Within the Abdomen and Pelvis in Mauro MA, Murphy KPJ, Thomson KR, et al (eds) Image-Guided Interventions. Philadelphia, PA, Saunders, 2013, pp 923-931. 2. Lee MJ: Percutaneous Abscess and Fluid Drainage in Kaufman JA, Lee M (eds) Vascular and Interventional Radiology Requisites. Philadelphia, PA, Saunders, 2013, pp 401-424. 3. Lorenz T, Thomas JL: Complications of Percutaneous Drainage. Semin IR 23:194-204, 2006. 4. Levin DC, Eschelman D, Parker L: Trends in Use of Percutaneous Versus Open Surgical Drainage of Abdominal Abscesses. JACR 12:1247-1250, 2015. 5. VanSonnenberg E, Wittich GR, Goodacre BW: Percutaneous Abscess Drainage: Update. World J Surg 25:362-372, 2001. 6. Patel IJ, Davidson JC, Nikolic B: Consensus Guidelines for Periprocedural Management of Coagulation Status and Hemostasis Risk in percutaneous Image-guided Interventions. 23:727-726, 2012. 7. Preece SR, Nelson RC, Bashir MR: Safety of an Intercostal Approach for Image-Guided Percutaneous Drainage of Subdiaphragmatic Abscesses. AJR 202:1349-1354, 2014. 8. McDermott S, Levis DA, Arellano RS: Approaches to the Difficult Drainage and Biopsy. Semin in IR 29:256-263, 2012.
9. Venkatesan AM, Kundu S, Sacks D: Practice Guideline for Adult Antibiotic Prophylaxis during Vascular and Interventional Radiology Procedures. J Vasc Interv Radiol 21:1611-1630, 2010. 10. Shahnazi M, Khatami A, Jamzad A: Safety and Efficacy of Percutaneous CTGuided Drainage in the Management of Abdominopelvic Abscess. Iran J Radiol 11:1-4, 2014. 11. Shenoy-Bhangle AS, Gervais DA: Use of Fibrinolytics in Abdominal and Pleural Collections. Seminars in Interventional Radiology 29:264-269, 2012. 12. Beland MD, Gervais, DA, Levis, DA: Complex Abdominal and Pelvic Abscesses: Efficacy of Adjunctive Tissue-Type Plasminogen Activator for Drainage. Radiology 247:567-573, 2008. 13. Ballard DH, Jahromi AH, Li AY: Abscess-Fistula Complexes: A Systematic Approach for Percutaneous Catheter Management. J Vasc Interv Radiol 26:1363-1367, 2015. 14. Pryluck DS, Singh CK, Clark TWI: Management of Fluid Collections in Acute Pancreatitis in Mauro MA, Murphy KPJ, Thomson KR, et al (eds) ImageGuided Interventions. Philadelphia, PA, Saunders, 2013, pp 932-936. 15. Thoeni, R: Revised Atlanta Classification of Acute Pancreatitis: Its Importance for the Radiologist and Its Effect on Treatment. Radiology 262:751-764, 2012.
Figure 1
C
C
B
C
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Fig. 1. A. Peripancreatic fluid collection. Axial contrast-enhanced CT shows the collection (C) with a surgical JP drain in place, which was not draining fluid. B. Preprocedure noncontrast image with the patient supine shows a small window to access the collection percutaneously. C. The blunt stylet (B) was used in the retroperitoneum to avoid injury to the left kidney. D. Final image shows the catheter and wire in the collection.
Figure 2
D C
A
Fig. 2. Right lower quadrant abscess. A: Axial image demonstrates a thick-walled, fluid-containing abscess (A), with colon anteriorly (C), preventing an anterior approach for access. B: By placing the patient in a left lateral decubitus position, this bowel loop moved out of the way, allowing for an anterior approach for drain placement (D).