The third part of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) Guidelines on Interventional Ultrasound assesses the evidence for ultrasound-guided and assisted interventions in abdominal treatment procedures. Recommendations for clinical practice are presented covering indications, contraindications, safety and efficacy of the broad variety of these techniques. In particular, drainage of abscesses and fluid collections, interventional tumor ablation techniques, interventional treatment of symptomatic cysts and echinococcosis, percutaneous transhepatic cholangiography and drainage, percutaneous gastrostomy, urinary bladder drainage, and nephrostomy are addressed (short version; a long version is published online).
Der dritte Teil der Leitlinien der European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) zur interventionellen Sonografie im Abdomen bewertet die Evidenz für transkutane sonografisch gestützte und assistierte therapeutische Interventionen im Abdomen. Auf der Grundlage publizierter Daten werden zu Indikationen, Kontraindikationen sowie zur sicheren und effizienten Durchführung Empfehlungen für die klinische Praxis gegeben. Berücksichtigung finden die sonografisch geführte Drainage von Abszessen und Flüssigkeitsansammlungen, Tumorablationstechniken, transkutane Zystensklerosierung symptomatischer Zysten und der Echinokokkose, die perkutane transhepatische Cholangiografie und Drainage, die perkutane Gastrostomie, die Harnblasenpunktion und Drainage sowie die Nephrostomie (Kurzversion; eine Langversion ist online publiziert).
This is the third of three guidelines (parts I – III) within the framework of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) Guidelines on Interventional Ultrasound describing ultrasound (US)-guided percutaneous diagnostic and therapeutic interventions of the abdomen. Part III deals with the indications and clinical impact of US-guided therapeutic interventions and gives evidence-based recommendations for the safety and efficacy of these techniques using the available evidence at the time of manuscript preparation. It is complemented by guidelines on general aspects of US-guided interventions (part I)  and US-guided diagnostic interventions (part II) . In addition, EFSUMB also will publish guidelines on the use of diagnostic and therapeutic endoscopic ultrasound   and ultrasound-guided vascular interventions .
Methods of guideline development are described in the introduction to the EFSUMB Guidelines on Interventional Ultrasound . Levels of evidence (LoE) and grades of recommendations (GoR) have been assigned according to the Oxford Centre for Evidence-based Medicine criteria (March 2009 edition) [http://www.cebm.net/oxford-centre-evidence-based-medicine-levels-evidence-march-2009].
Local ablative procedures
Local ablative procedures play a key role in the management of patients with malignancies, primarily with hepatocellular carcinoma (HCC), but also with metastases    .
Local ablative procedures can be classified according to the treatment intention as curative or palliative  .
Tumor ablation is usually performed with curative intent. This applies mainly to small HCCs (≤ 5 cm), as well as to colorectal liver metastases       . The decision for local ablation over resection should take into account data such as the patient’s age, co-morbidities, normal parenchymal reserve and tumor distribution inside the liver, as well as the risks for metachronous tumor growth, and all these should be weighed against the invasiveness of the procedure .
HCC ablation should be preferably performed with curative intent (LoE 1a, GoR A). Strong consensus (100 %).
The main indication for palliative treatment of liver tumors is metastatic neuroendocrine tumor load. Other primary  and secondary liver tumors may also be treated         .
Combined treatment options
With multiple liver metastases (commonly colorectal) not suitable for surgical resection because of their number or location (e. g., proximity of vascular or biliary structures), a combined approach should be considered .
Ablation in conjunction with resection is increasingly used as a parenchyma-sparing curative strategy that combines effective ablative treatment of small tumors with resection of large tumors, for which ablation is less effective        . Similar concepts can be applied to hepatocellular carcinoma (HCC) in a cirrhotic liver, when extensive surgical sacrifice of the parenchyma must be avoided.
Ablation in conjunction with resection may be considered as a parenchyma-sparing curative strategy (LoE 2a, GoR B). Strong consensus (100 %).
Hepatocellular carcinoma (HCC)
The treatment options for HCC in a cirrhotic liver are transplantation, surgical resection, local ablative therapies, transarterial chemoembolization (TACE), radioembolization with Yttrium90 loaded beads (transarterial radioembolization) (TARE), and, in cases of advanced disease, systemic therapy with sorafenib (Nexavar®). Image-guided percutaneous ablation therapies, such as radiofrequency ablation (RFA)   , percutaneous ethanol injection (PEI)    and microwave ablation , have been performed mainly with small HCCs, according to the Milan criteria . These are potentially curative, minimally invasive, and repeatable in case of recurrence .
Local ablative treatment techniques for HCC
Size of tumors
As a single RFA needle usually coagulates a region of about 2 cm in diameter, potentially non-spherical (depending on the RF system) multiple sequential insertions may be required to achieve a safety margin.
To overcome this limitation, multi-needle systems have been introduced for simultaneous ablations and stereotactically guided RFA    . There is no accepted maximum tumor size that can be ablated in a single session but the size is generally in the 4 to 5 cm range. The ablated zone should encompass the treated tumor and a circumferential margin of 5 – 10 mm around the tumor .
Location of tumors
HCC tumors in a subcapsular location or adjacent to the gallbladder have a higher likelihood of incomplete ablation  or major complications   .
To reduce the number of complications, attention must be paid to vulnerable structures close to the tumor or the ablation zone. This applies to the porta hepatis, gallbladder, stomach, small intestine and colon, all of which are particularly sensitive to thermal damage  . In case of subdiaphragmatic lesions, pulmonary, pleural or cardiac heat damage might occur, usually with only minor clinical significance  .
Number of tumors
The maximum number of tumors that can be ablated in a single procedure is not clearly defined, but ranges from 3 to 5 in most centers . Overall survival is best for patients with solitary tumors, intermediate for those with 2 to 3 tumors, and worst for those with ≥ 3 tumors .
The maximum recommended diameter of HCC lesions treatable with thermal ablation is generally considered below or equal to 5 cm, although optimal results are obtained in lesions < 3 cm (LoE 2b, GoR B). Strong consensus (100 %).
The ablation zone should aim to extend at least 5 mm beyond the visible borders (LoE 3a, GoR B). Strong consensus (100 %).
In lesions close to large vessels and heat-sensitive structures, alternative or additional techniques should be considered (LoE 3a, GoR B). Strong consensus (100 %).
Three to five HCCs are the recommended maximum number of lesions in a single session that allows percutaneous ablation with curative intent (LoE 2a, GoR B). Strong consensus (100 %).
RFA versus surgical resection in small HCCs
There is inconclusive evidence as to whether RFA is as effective as surgical resection as the first-line treatment for patients with small, solitary HCCs          . A systematic review of 8000 patients  with a current Cochrane analysis  reported uncertainty regarding the question of the impact of RFA versus surgery. However, a more recent meta-analysis, published after the Cochrane analysis , showed that there were differences in age and liver function between patients with early HCC submitted to either RFA or resection. When the analysis was corrected for these parameters, no survival differences were observed between RFA and surgery in single HCCs < 2 cm or 2 – 3 HCC tumors < 3 cm, whereas surgery resulted in a longer survival in the case of single HCCs measuring 2 – 5 cm . Mortality and morbidity rates of RFA have been reported to be 0 – 1.5 % and 0.9 – 7.9 %, respectively      .
Percutaneous ethanol injection (PEI)
PEI was the first ablative procedure, initially reported in the early 1980 s   .
The procedure is inexpensive and safe, with low mortality and morbidity (0 – 3.2 % and 0 – 0.4 %, respectively)   . Even though RFA has replaced PEI   , PEI can be offered in small HCCs, mainly those for which RFA is not feasible due to tumor location.
RFA versus PEI
Randomized controlled trials comparing RFA with PEI demonstrate that RFA is superior to ethanol injection in terms of treatment response, number of sessions, recurrences, and overall survival        as further supported by meta-analyses   .
The efficacy of the methods is similar for tumors ≤ 2 cm    . Meta-analyses, including randomized controlled trials (RCTs), confirmed that treatment with RFA offers a survival benefit as compared to PEI in tumors > 2 cm     . RFA has a slightly higher rate of major complications (4 %; 95 % CI, 1.8 – 6.4 %) as compared to PEI (2.7 %; 95 % CI, 0.4 – 5.1 %)    . The best results obtained in series of HCC patients treated by RFA provided 5-year survival rates of 40 – 70 % or higher in select groups of patients   . The best outcomes have been reported in Child–Pugh A patients with small (< 2 cm) single tumors  . Independent predictors of survival with RFA are initial complete response, Child–Pugh score, number or size of nodules, and baseline alpha-fetoprotein levels .
Percutaneous microwave ablation (MWA) was introduced into clinical practice in the 1990 s        .
Selection of ablation technique
With PEI, local response is related to tumor size. PEI has yielded very favorable results for small encapsulated HCCs (< 2 cm)  . HCC encapsulation by a cirrhotic liver prevents satellite nodules from being reached, leading to higher rates of local recurrence in comparison to RFA    ).
Percutaneous ethanol injection with curative intent is an alternative to thermal ablation in encapsulated HCCs < 20 mm (LoE 2a, GoR B). Broad agreement (95 %).
Percutaneous ethanol injection can be an alternative in case of contraindications to thermal ablation (LoE 3b, GoR B). Broad agreement (79 %).
Selection of imaging modality (ultrasound, CT, MRI)
US is the first-line imaging modality for local ablative procedures in the liver. CT guidance can be an alternative, particularly when US guidance is not feasible anatomically or with US imaging of occult lesions  . MRI guidance is possible but with limited availability and major costs. Local expertise and personal experience determine the modality of choice. Contrast-enhanced imaging must be available during the interventional procedure to confirm the completeness of necrosis. Fusion imaging is an alternative technique that can be used for the guidance of the procedure.
Planning and monitoring ablation treatment
Imaging plays an important role before, during and after ablation procedures. Assessment of tissue perfusion is crucial to differentiate necrotic areas from viable residual tumor. With US-and CT-guided RFA, this requires evaluation with contrast-enhanced imaging during and immediately after ablation. Contrast-enhanced ultrasound (CEUS) can provide important information for assessment during and immediately after ablation  :
assessment of the lesions to be treated by ablation (number, size, degree and homogeneity of lesion enhancement, presence of feeding vessels, to define the eligibility for treatment and the best ablation strategy)
depiction of previously undetectable lesions with the support of fusion imaging, enabling needle/probe guidance to occult lesions
detection of viable tumor persistence following loco-regional treatment 
CEUS is the most effective method to define local recurrence in a treated nodule because of its real-time capability, the intra-vascular characteristic of the contrast agent and the near-total differentiation between the displayed contrast and background information of current imaging methods . CT and MRI provide better overviews of the liver and adjacent organs, which are necessary for pretreatment staging and useful to detect distant intra- and extra-hepatic tumor recurrence.
Studies have established that RFA is a low-risk procedure    , with a mortality of 0.1 – 0.8 % and few adverse events. Major complications occur in 2.2 – 11 % of RFA-treated patients     . Bleeding, infection, arteriovenous fistula formation, bile duct damage, and tumor seeding are possible complications of local ablative therapy    .
Thermal track ablation can potentially reduce the likelihood of tumor seeding in HCC ablation to below 1 %    .
A multidisciplinary approach to assess patients with HCC in liver cirrhosis for possible transplantation is recommended prior to alternative treatments (LoE 5, GoR D). Strong consensus (100 %).
RFA with curative intent is an alternative, more cost-effective technique in comparison to surgery in early HCC BCLC-0 (HCC < 2 cm) (LoE 2a, GoR B). Strong consensus (100 %).
RFA with curative intent should be considered as a second-line treatment in single HCCs 2 – 5 cm in Child-Pugh A patients, after the patient has been evaluated for surgical resection (LoE 2b, GoR B). Strong consensus (100 %).
RFA with curative intent should be considered as the first-line treatment in Child-Pugh B patients with single HCCs < 5 cm or in patients with 2 or 3 HCCs < 3 cm (LoE 2b, GoR B). Strong consensus (100 %).
Solitary HCCs > 3 cm not suitable for surgery should be considered for combined loco-regional treatments (LoE 4, GoR C). Broad agreement (95 %).
Colorectal cancer liver metastases
It is estimated that 50 – 60 % of patients with colorectal cancer (CRC) will develop liver metastases . The most successful treatment for hepatic metastases is surgical resection           . However, approximately 50 – 70 % of these patients will develop recurrence .
Local ablative procedures with curative intent have a role in the management of CRC liver metastases  . Depending on the size of the lesions, RFA may be performed alone or combined with resection . Several studies have demonstrated that RFA achieved permanent local ablation of liver metastases and a 5-year survival of 24 % to 43 %     . These results are comparable to surgery         . Local recurrence occurs more frequently after ablation than with resection   .
Two meta-analyses confirmed that surgery is superior to RFA with regard to survival outcomes in patients with resectable CRC liver metastases  . The first RCT on the efficacy of RFA combined with chemotherapy versus chemotherapy alone was underpowered; RFA plus systemic treatment resulted in significantly longer progression-free survival (PFS) compared with chemotherapy alone .
Percutaneous thermal ablation with curative intent is a second-line alternative to surgery in patients with colorectal liver metastases (LoE 2a, GoR B). Strong consensus (100 %).
The maximum diameter of metastatic lesions treatable with thermal ablation is generally considered ≤ 4 cm, although better results are obtained in lesions < 3 cm (LoE 5, GoR D). Strong consensus (100 %).
The ablation zone should aim to extend at least 10 mm beyond the visible borders (LoE 5, GoR D). Broad agreement (94 %).
Other liver metastases
Percutaneous thermal ablation or PEI may be a therapeutic option for neuroendocrine liver metastases  .
Renal malignancies treated with local ablative therapy
Possible treatment options for renal cell carcinoma (RCC) are :
Surgery, either nephrectomy or nephron-sparing (open or laparoscopic)
Local ablative procedures (percutaneous or laparoscopic)
Standard therapy for small RCCs is nephron-sparing surgery. Local ablative techniques have evolved into alternative procedures, showing excellent results .
Tumors < 4 cm in diameter are ideal candidates for ablative techniques. The volume to be treated should include a 5 – 10 mm safety margin . Most tumors < 3 cm can be treated in a single ablation session. Tumors between 3 – 4 cm in diameter can also be successfully treated, although multiple ablation sessions may be required         .
Patients with RCCs < 3 cm with significant surgical risk or requirement for nephron-sparing strategy should be considered for local ablative therapy (LoE 2b, GoR B). Strong consensus (100 %).
RCTs comparing surgery and local ablative therapy have not been performed  . Cancer-specific survival is similar for both methods  . The European and American Urological Associations recommend thermal ablation as a treatment option for patients with a T1 renal mass .
Local recurrence-free survival following image-guided tumor ablation is 87 % . The local recurrence of percutaneously performed RFA is estimated at 2.5 – 14 % . Cancer-specific survival of patients treated with RFA is comparable to patients treated with surgery   . Both cryotherapy and RFA had a higher risk of recurrence compared to partial nephrectomy , but re-intervention is straightforward .
The rate of major complications for cryotherapy is 5 %, which is lower than for surgery , the most common complication being hemorrhage  with 2 % developing distant metastases  . Post-procedural ureteric strictures have also been documented . Cryotherapy is preferred over RFA in central tumors in contact with the renal hilum or the ureter .
RCC histology should be obtained prior to ablation (LoE 4, GoR C). Broad agreement (81 %).
CEUS can be used for surveillance after RFA of RCCs in order to detect local recurrence and to assess for liver metastases . CT of the thorax and abdomen is necessary to exclude metachronous extrahepatic metastases. No RCTs have been performed   .
Contrast-enhanced ultrasound or CT or MRI should be performed in the follow-up after RCC ablation, unless contraindicated (LoE 4, GoR C). Strong consensus (100 %).
US-guided percutaneous drainage of abdominal abscesses is a well-established interventional procedure first described in 1974  and is currently the first-line treatment approach for abdominal abscesses.
Definition and classification
Differentiation between phlegmonous inflammation and abscesses is of importance for treatment guidance. An abscess is a pus-containing confined collection, most often caused by bacteria. To be termed an abscess, the fluid has to be viscous and surrounded by an inflammatory wall that develops as a result of effective host defense .
Phlegmonous infections and small abscesses should be treated with antibiotics and require no drainage (LoE 5, GoR D). Strong consensus (100 %).
Postoperative fluid collection
Fluid collections present on postoperative imaging, localized or generalized (“free fluid”), are common and nonspecific which may represent different pathological entities such as hematoma, exudate, seroma, biloma, lymphocele or an abscess. Fluid seen on imaging is often not characteristic; any patient with a clinical suspicion of an abdominal abscess should have a diagnostic aspiration to guide further management. Sterile fluid collections can become infected postoperatively, requiring diagnostic aspiration and eventually therapeutic drainage.