Abdominal and pelvic abscesses have traditionally been drained by percutaneous techniques or surgery. While surgical drainage is associated with considerable morbidity and mortality, percutaneous techniques are associated with the need for multiple interventions, increased length of hospital stay, and an indwelling external catheter for prolonged periods. Endoscopic ultrasound (EUS) is a minimally invasive but highly effective technique that enables internal drainage of the abscess. Although data are limited, evidence supporting its clinical efficacy is increasing rapidly. This article summarizes the current status of EUS-guided approach for drainage of gastrointestinal abscess collections.
Areas adjacent to the gastrointestinal (GI) tract that can be easily accessed for drainage by endoscopic ultrasound (EUS) include the subphrenic space, perihepatic regions (left lobe of the liver), lesser sac, areas adjacent to the esophagus (posterior mediastinum), proximal small bowel, left colon, and the perirectal space. Most of the literature and well-designed trials involve drainage of pancreatic fluid collections (PFCs) in the lesser sac, which is discussed elsewhere in this supplement. This article discusses the existing data, techniques, limitations, and safety profile of the EUS-based approach for drainage of other abdominal and pelvic abscesses.
Most abdominal abscesses are post-surgical in nature or secondary to organ perforation and hence benign in etiology. Patients typically present with fever and abdominal pain. The objective of treatment is to evacuate the abscess and enable irrigation of the cavity to facilitate resolution of infection. EUS has the following advantages over conventional endoscopy: (1) it enables access to abscess cavities that do not cause a luminal compression, (2) drainage can be performed real time under sonographic guidance, (3) intervening vasculature can be avoided, and (4) an alternative diagnosis can be established in a small subset of patients.
Instruments and materials
A clear understanding of the anatomy of the abdomen or pelvis and its relationship to the abscess is important before embarking on drainage. In all patients, a dedicated magnetic resonance imaging or computed tomographic (CT) imaging should initially be performed to ascertain their underlying nature and confirm that these abscesses are in close proximity to the GI lumen. Abscesses that are multiloculated measure less than 4 cm in size, have immature walls (without a definitive rim), are located at the level of the dentate line (pelvic abscess) or greater than 2 cm from the EUS transducer, should be managed by alternative techniques. Laboratory parameters must be checked to ensure that patients are not coagulopathic or thrombocytopenic. Patients should be administered prophylactic antibiotics before the intervention and continued on oral antibiotics for 3 to 5 days. Drainage procedures are best performed in a unit with fluoroscopy set up to enable visualization of wire exchanges and stent or drain placement within the abscess. In patients with pelvic abscess, a preparation in the form of an enema and/or polyethylene glycol is mandatory to minimize the chances of contamination and for adequate visualization. Also, patients should be instructed to void urine before the procedure because a distended bladder may impair visualization of a small pelvic abscess during EUS. A sample of the abscess contents should routinely be sent for gram stain and culture in all patients.
Echoendoscopes
Linear array echoendoscopes offering a working channel of at least 3 mm should be used; this includes the FG 38UX (Pentax Precision Instruments Corp., Orangeburg, NY, USA), the EG 38UT (Pentax Precision Instruments Corp., Orangeburg, NY, USA), and the GF-UCT140/180 (Olympus Medical System Corporation, Center Valley, PA, USA). The EG 38UT and the GF-UCT 140, which are used with working channels of 3.8 and 3.7 mm, respectively, both allow placement of a 10F stent. On the other hand, the FG 38X has a working channel of 3.2 mm, which only permits placement of an 8.5F stent. If only echoendoscopes with smaller working channels are available, then after EUS-guided passage of a guidewire, the echoendoscope must be exchanged for a therapeutic gastroscope or duodenoscope, over the previously placed guidewire, to perform abscess drainage.
Accessories
A 19-gauge EUS–fine-needle aspiration (FNA) needle is required to pass a stiff 0.035-in guidewire into the abscess cavity ( Box 1 ). An over-the-wire needle knife catheter is required to puncture the wall of the abscess to facilitate stent or drain placement. Alternatively, in patients who are at high risk for bleeding, a standard 4.5F endoscopic retrograde cholangiopancreatography (ERCP) cannula can be passed over the guidewire to gradually ‘burrow’ the wall of the abscess cavity to achieve the same effect. A through-the-scope balloon (6–15 mm) is needed to further dilate the tract between the abscess cavity and GI lumen. Double pigtail plastic stents (7/8.5F or 10F) and/or catheter are required to facilitate drainage of the abscess cavity.
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Echoendoscope with a biopsy channel greater than 3.7 mm
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19-gauge FNA needle
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0.035 in guidewire
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4.5F ERCP cannula or an over-the-wire needle-knife catheter
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Over-the-wire balloon dilators
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7F or 10F double-pigtail plastic stents and/or drainage catheter
Procedural Technique
Graded dilation technique for drainage of abdominal abscess
Once the echoendoscope is advanced to the duodenum, a gradual withdrawal is performed with back and forth torque to identify the abscess cavity. Caution must be exercised to differentiate a gallbladder from the abscess. Inadvertent puncture of the gallbladder with a 19-gauge needle can lead to biliary peritonitis. Once the abscess is identified, after excluding the presence of vasculature in the path of the needle using color Doppler ultrasound, a 19-gauge FNA needle is used to puncture the cavity under EUS guidance ( Fig. 1 A). A 0.035-in guidewire is then introduced through the needle and coiled within the abscess cavity (see Fig. 1 B) under fluoroscopic guidance. The tract is then sequentially dilated by first passing a 4.5F ERCP cannula over the guidewire. Further dilation is then undertaken using a 6- to 15-mm over-the-wire biliary balloon dilator (see Fig. 1 C). After dilation, two 7 or 10F double-pigtail stents are deployed within the abscess under fluoroscopic guidance (see Fig. 1 D). Multiple stents and a 7 or 10F nasocystic drainage catheter has to be deployed in some patients for periodic flushing and evacuation of the abscess contents.
Technical tips
A major advantage of the graded dilation technique is that electrocautery is not used during any step of the procedure. Although there are no data on abdominal abscess drainage, in the largest series reported to date on EUS-guided drainage of PFCs using the graded dilation technique, bleeding or perforation was encountered in only about 1% of patients. In patients with a thick abscess wall, the ERCP cannula may “bounce off” if not aligned properly. It is important that the cannula be in line with the guidewire when it exits the echoendoscope so as to penetrate the abscess perpendicularly. Once within the cavity, the cannula should be withdrawn into the echoendoscope, and repeated penetration of the abscess should be attempted so as to dilate the transmural tract further.
Needle-Knife Technique for Abdominal Abscess Drainage
After coiling a guidewire within the abscess cavity using a 19-gauge FNA needle, the transmural tract can be dilated using electrocautery administered via an over-the-wire needle-knife catheter (rather than dilating the tract with an ERCP cannula). Another alternative includes the use of a dedicated commercially available cystotome. The cystotome is a modified needle-knife papillotome that consists of an inner wire with a needle-knife tip, a 5F inner catheter, and a 10F outer catheter equipped with a diathermy ring at its distal tip. The proximal end of this device includes a handle with connectors for administration of electrocautery. The abscess is punctured with the cystotome using the knife tip of the inner catheter, by administration of electrocautery, and then entered with the inner catheter. The metal part of the inner catheter is then withdrawn, and a 0.035-in guidewire is passed through the inner catheter into the cavity. The outer 10F sheath of the cystotome that is equipped with a diathermy ring is advanced through the puncture site using electrocautery. The cystotome is then removed leaving the guidewire in the cyst cavity. The trasmural tract is then dilated followed by stent deployment.
Technical tips
An advantage of the needle-knife technique is that it penetrates the abscess wall with relative ease. The main disadvantage of the technique is that perforation has been reported as a complication in several series evaluating drainage of PFCs. When an abscess is approached via the gastric cardia or the fundus of the stomach, because of acute angulation of the echoendoscope, the deployed needle knife may point tangentially leading to an undesirable incision. Maintaining a degree of tension on the guidewire keeps the needle-knife catheter in plane with the guidewire as it exits the echoendoscope and can possibly minimize the risk of perforation.
Post-procedure follow-up
Although there are no formal recommendations, a follow-up CT is performed within 2 to 3 days. If the abscess has decreased in size by more than 50% and the patient is afebrile with improved symptoms, the drainage catheter is discontinued before patient discharge from the hospital. Another CT is then obtained within 6 to 8 weeks to ascertain resolution of the abscess. If the abscess has resolved, the transmural stent is removed by endoscopy. If the abscess is persistent, additional stents are deployed or the patient is referred for surgery.
Pelvic abscess drainage
First, the abscess must be located using a curved linear array echoendoscope. It can sometimes be challenging to differentiate a urinary bladder from pelvic abscess. Unlike an abscess, the urinary bladder generally does not have sediment at its base. Also, as most patients with pelvic abscess are bed bound with a foley catheter in place, the presence of a catheter in the bladder can help make this distinction. If the urinary bladder is accidentally punctured, it generally does not lead to a complication (provided one has not attempted dilation). Once located, intervening vasculature must be excluded using color Doppler. Under EUS guidance, a 19-gauge FNA needle is used to puncture the abscess cavity ( Fig. 2 A). The stylet is removed, and the needle is flushed with saline and aspirated to evacuate as much pus as possible. If there is no return of abscess contents on applying suction, one must irrigate 20 mL normal saline via the FNA needle and then apply suction again. It is likely that the abscess content is thick or the lumen of the needle is clogged with mucosa or debris. A 0.035-in guidewire is then passed through the needle and coiled within the abscess cavity (see Fig. 2 B, C). The needle is then exchanged over the guidewire for a 4.5F ERCP cannula or a needle-knife catheter to dilate the tract between the rectum and the abscess cavity (see Fig. 2 D). The tract is then further dilated using an 8-mm over-the-wire balloon dilator (see Fig. 2 E, F). Once the tract is dilated, one or two 7F/10F double-pigtail transmural stents are deployed (see Fig. 2 G). The decision to place one or more stents is based on the viscosity of the abscess contents: one if the fluid flowed smoothly and more if the contents were thicker. In patients with abscesses that measure 8 cm or more in size and in those abscesses that do not drain well despite placement of transmural stents, an additional translumenal drainage catheter is deployed (see Fig. 2 H). The abscess cavity is accessed again with a 5F ERCP cannula to pass another 0.035-in guidewire. A 10F, 80-cm single-pigtail drain is then deployed over the guidewire. This drain will exit the anus and remain secured to the patient’s gluteal region using tape. This drain is then flushed with 30 to 50 mL of normal saline every 4 hours until the aspirate is clear.
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Endoscopic Ultrasonography-Guided Biliary Drainage: Rendezvous Technique
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Endoscopic Ultrasound: Contrast Enhancement
Endoscopic Ultrasonography-Guided Tumor Ablation
Endoscopic Ultrasonography-Guided Pancreatic Drainage
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