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Interventional Radiology Case Conferences |
1 All authors: Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, White 270, 55 Fruit St., Boston, MA 02114.
Received January 23, 2002;
accepted after revision February 11, 2002.
Address correspondence to B. C. Lucey.
Case History
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Within 2 days, the patient developed pain in the left lower quadrant and a fever of 101°F (38.4°C). A CT scan obtained with oral and IV contrast material revealed a 5 x 5 cm low-attenuation collection in the left lower quadrant. This collection was amenable to percutaneous drainage that was performed under CT guidance using a 12-French catheter (Cook, Bloomington, IN). Eighty milliliters of pus that subsequently grew gram-positive and gram-negative rods with gram-positive cocci was aspirated, and the collection flushed with normal saline. The procedure was uncomplicated, and the drain was removed 4 days later after the patient's pain and fever subsided. He improved and was discharged 12 days later and was prescribed a maintenance dose of hydroxyurea for the polycythemia rubra vera.
The patient was readmitted nearly 6 months later for an elective transverse colostomy take down with an end-to-end colorectal anastomosis. During the postoperative period, the patient developed fevers up to 101.5°F (38.6°C) with a WBC of 25,000/µL, suggesting an infectious source. A CT scan with oral contrast material was obtained that showed a large volume of extraluminal oral contrast material in the left paracolic gutter (Figs. 1A and 1B). This collection extended from the pelvis almost to the left subdiaphragmatic space.
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Dr. Mueller. It is sometimes difficult to differentiate a contrast-filled extraluminal collection from normal colon, especially when the collection lies in either paracolic gutter [1, 2]. The combination of gas and contrast material in an abscess located in close proximity to the bowel may lead one to misinterpret these findings as intraluminal contrast. Helpful signs that lead one to suspect an extraluminal collection include a pocket of gas in the collection that is dependent and a lack of haustra that are normally seen in the bowel. In the normal fluid- and gas-filled colon, the gas is nondependent and rises with the patient lying supine. Changing the window level of the CT image to lung windows often allows the identification of haustral folds in normal bowel and a lack of these folds in extraluminal leaks. More important, a high degree of suspicion is also necessary to avoid underinterpreting these cases.
Dr. Lucey. How do you best diagnose an anastomotic leak when one is suspected?
Dr. Boland. CT with administration of oral contrast material is the investigation of choice. If there is insufficient oral contrast material in the area in question, then rectal contrast material may need to be administered, particularly for suspected colonic leaks. If the findings from the CT scan are still confusing, then a Gastrografin ([meglumine diatrizoate] Bracco Diagnostics, Princeton, NJ) enema with fluoroscopy can be performed, although this method is generally less helpful.
In patients with a low anastamosis, a Foley catheter should be used rather than an enema tube, and the balloon should not be inflated. Inflating the balloon increases the risk of excessive colonic pressure with the potential to rupture. The level of the anastomosis may be apparent on the scout image if surgical staples are present. Once rectal contrast medium has passed the level of the anastomosis, images should be obtained in multiple planes. CT can define the extent of the collection more clearly than a Gastrografin enema and can depict the entire abdomen. CT may show the presence of further collections or may even reveal an alternative cause for the deterioration of the patient's condition.
Dr. Lucey. Could you describe the possible modalities and the technique used for draining a collection such as the one found in this patient?
Dr. Maher. The collection was large and located superficially, anterior and lateral to the descending colon. Any catheter drainage of an intraabdominal abscess must not violate the adjacent normal anatomic structures, and therefore the preferred method usually involves CT guidance [3]. Careful inspection of the catheter access route is made to avoid these anatomic structures. This may involve placing the patient in the prone, decubitus, or semidecubitus position. Occasionally, an angled CT gantry will delineate a safe route for catheter placement [4]. However, in large superficial collections such as in this patient, sonographic guidance alone, or combined with fluoroscopy, can be used (Fig. 1C).
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Using a standard aseptic technique and conscious sedation, we punctured the
collection with an 18-gauge needle under direct sonographic guidance. Purulent
material was aspirated and a 0.035-inch 3-mm J guidewire was manipulated under
fluoroscopy to pass into the cephalad aspect of the cavity. The 3-mm J
guidewire was then exchanged for a 0.038-inch Amplatz guidewire using a Kumpe
(Cook, Bloomington, IN) catheter. The tract was dilated to 10-French using
sequential dilators. Given the dimensions of the abscess, we decided to place
a second catheter using the Seldinger technique. A guidewire was placed
through the same track and positioned with the tip lying at the caudal end of
the collection (Fig. 1D). A
10-French (Medi-Tech Boston Scientific, Watertown, MA) multihole drainage
catheter was then passed over the cephalad guidewire with the tip positioned
in the left subphrenic region. Pus was aspirated and sent for culture and
sensitivity. An 8-French catheter was then placed with the tip lying in the
caudal aspect of the collection. Catheters were therefore placed in both the
cephalad and caudal components of the collection in an attempt to adequately
drain the collection (Fig. 1E).
Both catheters were aspirated, flushed with normal saline, and sutured to the
skin. Routine postprocedural catheter care was used in the follow-up period
[5].
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Dr. Lucey. What are the advantages of using fluoroscopy combined with sonography rather than sonography alone?
Dr. Gervais. It may sometimes be prudent to manipulate the guidewire under direct visualization using fluoroscopy, particularly with large complex collections or when the access route may prove difficult. In this individual, the collection extended to the subphrenic space, and using fluoroscopy permitted successful positioning of the catheters so that they covered the total extent of the collection rather than inadvertently coiling in one anatomic area. Theoretically, this type of positioning will provide more complete drainage.
Dr. Lucey. What are the indications for using two catheters for abscess drainage?
Dr. Boland. There are several situations in which a single catheter may not be sufficient for complete drainage of an abscess. A multiloculated, irregularly shaped collection may not fully drain through a solitary catheter that is positioned in one area of the collection. As in this patient, large collections will often require more than one catheter. Large collections may involve several intraperitoneal spaces, and there may be more than one dependent site where pus may collect. A catheter located in the most dependent portion of the abscess may not drain pus that is settled in a more superficial locule. In addition, large collections may insinuate themselves around adjacent structures and can therefore develop narrow-necked diverticula or outpouches arising from the primary abscess cavity. Although there is communication between the abscess and the diverticula, which can be confirmed on contrast-enhanced examinations, pus may not readily flow between them. A second catheter may therefore be required to successfully drain these abscesses.
Dr. Lucey. How will I know when one catheter is insufficient to drain a collection?
Dr. Mueller. Both clinical and imaging clues would indicate that more than one catheter may be required. First, one should always perform postprocedural imaging after percutaneous abscess drainage because adequate drainage of the collection can then be assessed. Drainage is best performed with CT, although it can also be accomplished using sonography for superficial collections. A particular disadvantage of fluoroscopy is that small additional collections that either do not communicate or communicate poorly with the large collection may not be visualized.
Second, clinical follow-up by the radiologist is essential [5]. Follow-up involves daily inspection of the catheter and drainage contents, regular flushing of the catheter with normal saline, and monitoring the daily catheter output [6]. The patient's clinical condition should also be monitored, and the WBC and temperature should return to normal. If the patient does not symptomatically improve or fever and elevated WBC persist, inadequate drainage should be suspected. Follow-up imaging should then be performed, and the necessity for a second catheter can be assessed.
Dr. Lucey. Some patients drain large volumes of material from an abscess but still have fevers and an elevated WBC. What does this imply?
Dr. Boland. First and foremost, one should obtain a repeated imaging study, preferably using CT with oral contrast material to determine whether a new or a previously undrained collection is present. Second, one should understand that draining well does not necessarily mean that the collection is completely drained. If the collection, as in this case, is large or multiseptate, a second or third catheter may be necessary to obtain complete drainage.
Dr. Lucey. What influences the choice of catheter size when planning an abscess drainage?
Dr. Maher. A general rule of thumb is that the larger the catheter placed, the better the drainage. Catheters greater than 10-French are less likely to become clogged and are generally comfortable for the patient [6]. The suspected nature of the contents of the collection should be used as a criterion for deciding which catheter to use [6]. Serosanguinous fluid can be drained with smaller calibre catheters (8-French or 10-French). Infected collections, particularly infected hematomas, require larger catheters (12- to 16-French) because of their turbid and viscous nature. Often the choice of catheter size is made only after an initial aspiration of the contents. On occasion, even larger catheters have been used in thicker, more viscous collections. Other factors can influence the choice of catheter size. In patients with a bleeding diathesis, it is prudent to use smaller catheters to decrease the potential risk of bleeding. The depth of the collection has no influence on the choice of catheter size as long as there is an unobstructed access route.
Dr. Lucey. Most abscess catheters have only a few drainage holes at their tips. Does this matter?
Dr. Gervais. Generally not, because the success of abscess drainage is usually determined at the time of placement. However, in large collections, particularly those in potential spaces such as the subphrenic region as opposed to collections in organs such as the liver, a drainage catheter with more than 10 sideholes, such as those used for biliary drainage, may provide more surface area for drainage. This type of catheter allows more complete drainage.
Dr. Lucey. Is there an advantage to using the Seldinger technique over the trocar technique?
Dr. Mueller. The Seldinger technique offers a more conservative approach with a single needle puncture because it potentially permits a step-by-step approach to catheter placement. A guidewire is passed through this needle, and the track is dilated over this guidewire to accommodate the catheter. The Seldinger technique is especially useful in procedures performed using fluoroscopic guidance because real-time monitoring of the guidewire and catheter manipulation can aid in accurate catheter placement. This technique, however, is more time-consuming than the trocar approach. One disadvantage of the Seldinger technique is that the guidewire has a tendency to buckle at the skin, and care must be taken to ensure that this does not happen [4]. To help prevent buckling, the dilators and catheter should be passed over the guidewire in the same plane as the initial needle puncture. In addition, the abscess material may leak around the guidewire while the radiologist is dilating the track.
The trocar technique is frequently chosen for sonographic and CT-guided drainage of collections. A 20-gauge needle is passed directly into the cavity, using either CT or sonographic guidance. Once the correct position has been confirmed on imaging, the catheter is inserted into the cavity using a tandem approach, alongside the 20-gauge needle.
The choice of technique ultimately lies in the hands of the interventional radiologist performing the procedure. In this patient, the Seldinger technique was used because of the ease of placement under sonographic and fluoroscopic guidance and because it was important to ensure accurate placement of the catheters into either end of the collection.
Dr. Lucey. What steps are necessary to ensure complete drainage after the catheter has been placed?
Dr. Boland. First, the material in the abscess cavity should be aspirated completely to decrease the volume of infected material and to initiate collapse of the cavity. Gentle irrigation with small volumes (10-15 mL) of sterile saline should then be performed [4]. This irrigation will remove remaining debris and will clean the cavity of any remaining purulent material. A CT scan obtained after drainage will act as a baseline for further imaging, to determine either if the collection continues to decrease in size or if the patient deteriorates and an abscess recurrence is suspected.
Dr. Lucey. The catheter should be removed once the collection has drained completely. What criteria do you use in deciding when to remove a catheter, and how do you know that a collection has fully resolved?
Dr. Maher. The most important criterion to determine whether catheter withdrawal is prudent is the patient's clinical condition correlated with the volume of catheter drainage over time. The patient should have a normal temperature within 48-72 hr, and the WBC should return to normal. The catheter drainage should also decrease over time. Decreasing outputs from the catheter to less than 20 mL/24 hr is an indication that the collection is well drained, providing that the patient's fever has abated [6]. Catheter care is performed by flushing the catheter at least every 8 hr with 5-10 mL of normal saline. Decreasing outputs from the catheter could also mean catheter blockage, and flushing is helpful to prevent this. Finally, follow-up imaging is frequently used to determine whether a catheter can be withdrawn. Imaging is usually performed with CT but can also be performed with sonography for superficial collections (Fig. 1G).
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Dr. Lucey. Are there any indicators after abscess drainage that would suggest an underlying anastomotic leak?
Dr. Boland. The key to recognizing an anastomotic leak lies in detecting persistently large outputs from the drainage catheter. The volume drained from an abscess should decrease over time if there is no communication with the bowel. An anastomotic leak should be suspected if large volumes (>50 mL) are drained over a protracted period or if the volume drained increases after an initial decrease in drainage. Communication with the bowel, when suspected, may be confirmed with a contrast injection into the catheter. A CT scan with oral contrast material may also show the anastomotic breakdown. The most important consequence of an anastomotic leak relates to the duration of catheter drainage. Premature removal of the drainage catheter may result in reaccumulation of the abscess. The catheter should remain in situ until the anastomotic leak has healed, as shown by a contrast injection into the catheter.
Dr. Lucey. Are these criteria for catheter removal altered when an anastomotic leak is the cause of the abscess?
Dr. Mueller. The criteria for catheter removal will remain unchanged. The catheter should stay in situ for a protracted period even when the abscess appears to be drained to allow time for the anastomotic breakdown to heal. The time for healing of the anastomotic breakdown can be affected by the condition of the anastomosed segment—for example, if there is distal obstruction, irradiation of the bowel, or an intrinsic abnormality of the bowel such as Crohn's disease. Any distal obstruction would allow the bowel contents to take the path of lesser resistance through the site of anastomotic breakdown. For the bowel to heal, the distal obstruction must be resolved. If the bowel is damaged by radiation or intrinsic disease, healing of the leak may be hindered. Bowel rest and parenteral nutrition are often used, but even with these treatments, healing may prove difficult.
Dr. Lucey. As you have described, it may take many weeks for these collections to resolve. Should the patient remain in the hospital for the duration?
Dr. Gervais. Many catheters should remain in situ for only 5-7 days. Patients who require longer drainage, as this patient did, do not have to remain in the hospital until the catheter is removed. Most patients respond well to percutaneous abscess drainage initially even if there is communication with the bowel. While waiting for the communication to seal, the patient can be discharged with the catheter securely positioned after the daily outputs remain reasonably constant for 24 hr. The patient (or a family member) must be capable of changing the catheter bag and must be responsible for flushing the catheter at home twice a day. The patient should be encouraged to contact the radiology department with any issues or questions that might ensue. In patients with a documented enteric fistula, particularly in the proximal small bowel with high outputs, it may be necessary to institute IV hyperalimentation for a period of time to rest the bowel and provide enough time for the fistula to heal. This can create an obstacle to early discharge.
The patient in this case showed catheter outputs that were initially in excess of 100 mL/24 hr for the first week and remained above 50 mL/24 hr for the following days. The patient was discharged with an appointment for a follow-up catheter injection 3 weeks later. This subsequent examination did not reveal any persistent communication with the bowel. The outputs were minimal and the catheter was removed after the catheter injection. At the 6-month follow-up, the patient is well and does not have any symptoms related to the previous anastomotic leak.
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