EFSUMB Position Paper: Recommendations for Gastrointestinal Ultrasound (GIUS) in Acute Appendicitis and Diverticulitis

Abstract

An interdisciplinary task force of European experts summarizes the value of gastrointestinal ultrasound (GIUS) in the management of acute appendicitis and diverticulitis. Based on an extensive literature review, clinical recommendations for these highly common diseases in visceral medicine are presented.

In patients with acute appendicitis, preoperative sonography has been established as a routine procedure in most European countries for medical and legal reasons. Routine sonography in these patients may reduce the rate of unnecessary surgery by half. The sensitivity, specificity, and accuracy of ultrasound reach values above 90 % and are equivalent to CT and MRI. However, the high operator dependence may be a problem, for example in point-of-care ultrasound in emergency departments. Structured training programs, quality controls and standardized ultrasound reporting should be increasingly implemented.

In the case of suspected acute diverticulitis, “ultrasound first” should also be a basic element in the approach to all patients. Sonography can confirm the diagnosis and allows early risk stratification. As treatment strategies have become less aggressive and more tailored to the stage of diverticulitis, accurate staging has become increasingly important. GIUS and CT have proven to have similar sensitivity and specificity. Especially in cases of uncomplicated diverticulitis, GIUS will be the one and only imaging procedure. CT may work as a backup and has particular advantages for diverticulitis located in the distal sigmoid, inflammation deep in the small pelvis and insufficient ultrasound scanning conditions. This step-up approach (ultrasound first and CT only in case of a negative or inconclusive ultrasound result) has proven to yield the best accuracy.

Zusammenfassung

Im Rahmen des EFSUMB-Leitlinienprojekts zum gastrointestinalen Ultraschall (GIUS) gibt eine interdisziplinäre Arbeitsgruppe von europäischen Experten einen Überblick zum Nutzen der Sonografie bei akuter Appendizitis und Divertikulitis. Basierend auf einer umfangreichen Literaturrecherche werden klinische Empfehlungen zu diesen häufigen Erkrankungen der Viszeral-Medizin vorgestellt.

Bei Patienten mit akuter Appendizitis haben medizinische und juristische Erwägungen die präoperative Sonografie heute als Routineverfahren in den meisten europäischen Ländern fest etabliert. Die Sonografie kann hier die Rate unnötiger Operation halbieren. Sensitivität, Spezifität und Genauigkeit des Ultraschalls erreichen Werte von über 90 % und entsprechen CT oder MRT. Eine hohe Untersucherabhängigkeit kann jedoch problematisch sein, beispielsweise beim bettseitigen Ultraschall in der Notaufnahme oder Praxis. Strukturierte Trainingsprogramme, Qualitätskontrollen und ein standardisierter Befundbericht sollten deshalb Einzug in den klinischen Alltag finden. Auch beim Verdacht auf eine akute Divertikulitis sollte die „ultrasound first“-Strategie Anwendung finden.

Die Sonografie kann die Diagnose einer Divertikulitis bestätigen und den Schweregrad abschätzen. Da heutige Therapiestrategien weniger aggressiv und mehr auf das Stadium der Divertikulitis zugeschnitten sind, ist eine genaue Einteilung des Schweregrads immer wichtiger geworden. GIUS und CT haben hier eine ähnliche Sensitivität und Spezifität. Gerade bei unkomplizierter Divertikulitis ist die Sonografie völlig ausreichend. Das CT kann als Backup dienen und hat Vorteile bei der Divertikulitis im distalen Sigma, bei einer Entzündung tief im kleinen Becken oder bei unzureichenden Untersuchungsbedingungen. Eine solche Stufendiagnostik (Ultraschall zuerst und CT nur im Falle eines negativen oder nicht eindeutigen Befundes) hat bei der Divertikulitis die höchste Genauigkeit bewiesen.

Key words

appendicitis - diverticulitis - guideline - ultrasound - gastrointestinal tract

1. Introduction

In 2014 the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) formed a Gastrointestinal Ultrasound (GIUS) task force group to promote the use of GIUS in a clinical setting. Altogether seven “Recommendations and Guidelines for Gastrointestinal Ultrasound (GIUS)” are planned. Guidelines for examination techniques and normal findings [1] and for inflammatory bowel diseases [2] marked the kick-off last year. This paper adds recommendations for acute appendicitis and diverticulitis as highly common diseases in visceral medicine.

A team of 18 European experts in Gastrointestinal Ultrasound from Gastroenterology, Radiology and Surgery created recommendations for the use of imaging, based on an extensive literature review until May 2018. These recommendations were refined and finally voted on in an online survey. The agreement/disagreement level was scored on a five-point Likert scale as follows: A+: agree; A–: rather agree; I: indecisive; D–: rather disagree; D+: disagree. All 21 statements had broad agreement of more than 80 % of the experts. The consensus levels of agreement are listed for each recommendation.

2. Acute appendicitis

2.1. Prevalence and clinical implication

Acute appendicitis is the most common surgical disease in Western countries, with a lifetime prevalence of 7 – 8 % [3] [4]. In 1986, Puylaert introduced graded compression ultrasound in the workup of suspected appendicitis [5]. Beside clinical examination and laboratory findings, imaging has become the third component in the assessment of patients with suspected appendicitis [6] [7]. The three main goals of the ultrasound examination are:

• Exclusion of an alternative abdominal disease.

• Confirmation of typical appendicitis or

• Ruling out of acute appendicitis, by proving a normal appendix over its entire length.

The routine use of ultrasound in suspected appendicitis halves the rate of negative appendectomies and reduces surgical complications and costs [6] [8] [9] [10].

Recent studies evaluated antibiotic therapy as a possible alternative in selected cases of uncomplicated appendicitis. For this, appendicitis must be verified by imaging and complicated versus uncomplicated appendicitis should be distinguished [11] [12] [13].

2.2. Examination technique

One way to detect an inflamed appendix is a simple search at the point of maximum tenderness [5]. An alternative way involves systematic localization of the ascending colon, the cecal pole, the terminal ileum and the origin of the appendix, 2 – 3 cm below the medial contour of the cecum [14] [15]. Examination is performed using the graded compression technique first described by Puylaert [5]. Gentle compression eliminates disturbing gas and reduces the distance to the pathologic process. Additions to this technique have been described, for example a left oblique body position in obese patients or an upward graded compression technique in children [16] [17] [18] [19]. Ultrasound experience plays a role in the visualization of the appendix. Practical training in normal and pathological conditions is mandatory to enable adequate appendix evaluation.

2.3. Sonography of uncomplicated appendicitis

Previously, acute appendicitis was diagnosed when a thickened vermiform appendix could be visualized at the point of maximum tenderness [5]. However, increasing experience and technical improvements have made it possible to demonstrate a normal appendix in more than half of adults and more than 70 % of children [20] [21] [22]. Beside maximum diameter, several additional criteria that help to distinguish between an inflamed and a normal appendix have been established. These criteria are the same for children and adults [23].

Primary signs of acute appendicitis

1. Maximum outer diameter of more than 6 mm [14] [17] [24] [25] [26] [27] [28] [29] [30]. A diameter between 6 – 8 mm indicates an equivocal zone of uncertainty [27] [31] [32].

2. Maximal tenderness over the thickened appendix [5] [15] [29] [33] [34].

3. Incompressibility of the inflamed appendix [14] [17] [24] [25] [28] [29] [30] [35].

4. (Large) appendicoliths [14] [25] [26] [28] [29] [36].

5. Hypervascularity in color Doppler in uncomplicated cases [14] [29] [37] [38].

6. Loss of stratification in gangrenous appendicitis [25] [29] [30] [36].

Secondary signs of acute appendicitis (in the surroundings)

1. Hyperechoic periappendiceal tissue [14] [15] [17] [24] [25] [29] [30] [34] [39].

2. Complex fluid collection (pericecal abscess) [14] [15] [17] [25] [29] [39].

3. Mesenteric lymphadenopathy [14] [15] [25] [40] [41].

4. Periappendiceal fluid [14] [15] [25].

2.4. Sonography of complicated appendicitis

Complicated appendicitis includes gangrenous appendicitis (focal or complete necrosis of the wall) as well as perforation (inducing abscess, regional peritonitis and general peritonitis). Confirmation of these complications has consequences for treatment and usually rules out conservative treatment [13] [42] [43]. There is a continuous transition from severe uncomplicated (phlegmonous) to gangrenous appendicitis.

The loss of the normally echogenic submucosal layer seems to be the best independent indicator of gangrenous appendicitis [11]. Other indicators of necrosis may be the lack of vascularization on color Doppler or an appendiceal wall enhancement defect, but these have not been sufficiently investigated [44] [45].

Signs of (sealed) perforation are extraluminal gas, localized collections of periappendiceal fluid, extraluminal appendicoliths and abscess [14] [15] [24] [25] [39].

To distinguish non-complicated from complicated appendicitis, scoring systems based on clinical and imaging features have been suggested [13] [44] [45] [46]. However, they must still be confirmed in larger studies. Other features like intraluminal appendicoliths do not implicate complicated appendicitis, but are associated with perforation and recurrence under antibiotic therapy [42] [47] [48].

2.5. Value of the various sonographic criteria

In routine clinical examination, only the combination of as many different criteria as possible guarantees the best results in the validation or ruling out of acute appendicitis [14] [15] [24] [25] [29] [30] [33] [34] [39]. The three most important criteria in the confirmation of acute appendicitis are:

1. max. diameter of appendix > 6 mm

2. maximum pain over the appendix

3. hyperechoic periappendiceal tissue

Free fluid, mesenteric lymphadenopathy and vascularity of the appendiceal wall on color Doppler are nonspecific signs and can be found in many other situations [14] [15] [25]. Definite exclusion of appendicitis requires visualization of the normal appendix in its entire length [29].

2.6. False-negative results

Non-visualization of the appendix is a problem and does not rule out acute appendicitis. The most important reason for false-negative results is inexperience in GIUS and the examination technique. In this case, an intensive search for indirect signs of appendicitis should be performed as a first step [49] [50] [51].

However, some situations are challenging even for experienced investigators: in particular when the appendix has a retrocecal or pelvic position or in very obese patients [33] [52] [53] [54]. In these cases, adequate compression, scanning in a left lateral decubitus position of the patient and use of a convex probe may be essential to visualize the appendix [17] [52] [53]. Focal appendicitis confined to the tip has a frequency of about 5 % and is another factor in misdiagnosis [25] [37]. Therefore, demonstration of the entire length of the appendix is important [15] [25] [37].

Gas in the appendiceal wall in cases of gangrenous appendicitis may be misinterpreted as a gas-containing bowel loop [15] [55]. A perforated and completely destructed appendix in an abscess is another rare cause of a false-negative result.

2.7. False-positive results

Soon after introducing ultrasound as a preoperative tool, cases of “spontaneously resolving appendicitis” were observed [56] [57]. Recent research confirms mild forms of appendicitis, which resolve spontaneously or under antibiotic therapy [4] [58] [59]. Strictly speaking they are not false-positive, but rather mild courses that probably would not require surgery.

Several other pitfalls can lead to a false-positive US diagnosis of acute appendicitis:

1. Incorrect classification of the terminal ileum as an inflamed appendix [15] [60] [61] [62] [63] [64].

2. Other tubular structures in the right lower abdomen simulating an inflamed appendix:

   • e. g. Meckel’s diverticulitis

   • right-sided colonic diverticulitis

   • dilated Fallopian tube

   • gonadal vein thrombosis

   • muscle fibers of psoas [15] [61] [62] [64]

3. Appendiceal thickening can also be produced by other conditions [65] [66] [67] [68] [69] [70] [71]:

   • Primary appendiceal thickening

     • Crohn’s disease: appendicular involvement is relatively frequent (20 – 25 %) [65] [66] [67]

     • infectious enterocolitis

     • cecal carcinoma [61] [66] [68]

     • appendiceal tumors such as cystadenoma, mucocele or carcinoid [61] [66] [69]

   • Secondary thickening (periappendicitis in case of peritonitis)

2.8. Comparison of US with others imaging methods

The diagnostic accuracy of high-end ultrasound in suspected appendicitis has clearly improved over the last decades. Meanwhile the sensitivity, specificity, and accuracy of ultrasound have reached values above 90 % and are equivalent to CT or MRI [72] [73] [74] [75] [76] [77] [78].

However, ultrasound is a highly operator-dependent tool, and its sensitivity fluctuates greatly in the case of inexperienced operators or inadequate equipment. Institutions using US regularly have a higher sensitivity, and the sensitivity increases with an increased rate of visualization of the appendix [79] [80] [81]. In addition, patient characteristics (e. g. obesity) may influence the sensitivity of US [82].

Point-of-care ultrasonography (POCUS) is increasingly performed by emergency physicians to diagnose acute appendicitis and is available around the clock. If adequate equipment and training are provided, the results will reach accuracy nearly equal to that of ultrasound performed by radiologists, gastroenterologists and pediatricians [83] [84] [85] [86].

Ultrasound for suspected appendicitis may be challenging among pregnant women: if the appendix can be visualized, the specificity of US is good. In equivocal cases, MRI has a higher sensitivity and is considered the method of choice in pregnant women [85] [87].

2.9. Diagnostic strategy

Preoperative imaging has become routine in the workup of suspected appendicitis for both medical and legal reasons. Ultrasound is available in almost every emergency department as a point-of-care procedure 24/7 hours without delay. It is cheap, noninvasive and without ionizing radiation [88].

Based on this data, an “ultrasound first and always” strategy has proved to be reasonable in both children and adults [89] [90] [91] [92] [93]. Primary ultrasound supports the ALARA principle (radiation as low as reasonably achievable), thereby avoiding radiation exposure, especially in children and women of childbearing age [94] [95]. Consistent use of ultrasound in right lower quadrant pain can reduce the need for additional CT or MRI imaging to a small fraction [76] [96] [97] [98] [99]. Cases of inconclusive ultrasonography should lead to clinical reassessment. A second ultrasound after an observation period [100] [101] or a complementary MRI or CT examination should be considered.

Diagnostic scoring systems are recommended in some guidelines as a part of a diagnostic algorithm for suspected appendicitis [87] [102]. There are several competing scores [e. g. the Alvarado Score, Pediatric Appendicitis Score (PAS), and Appendicitis Inflammatory Response score (AIR)] but these do not always perform satisfactorily. Even the cut-off values are not clear. Scores may be used for roughly estimating the likelihood, but not for proving appendicitis [103] [104] [105]. In accordance with the Dutch guidelines [92], we recommend routine use of ultrasound in all cases of suspected appendicitis and do not consider the use of scoring groups obligatory ([Table 1]).

Table 1 Based on clinical assessment, laboratory results, and possibly scoring results, three scenarios are common in the daily routine.

risk of appendicitis	Alvarado or AIR points	impact of sonography
low	0 – 4	visualization of the normal appendix in its full length definitively rules out appendicitis
		complete ultrasound is helpful in finding an alternative diagnosis
intermediate	5 – 8	validation of an inflamed appendix confirms the need for surgery
		if the diagnosis remains unclear, complementary CT, MRI or serial ultrasound performed by an experienced operator may be helpful
high	> 8	confirmation of acute appendicitis
		diagnosis of complications, e. g. abscess

2.10. Education and quality management

In more cases than in other imaging modalities, GIUS depends on individual skills and adequate ultrasound equipment. So-called “non-diagnostic ultrasound” represents a problem especially among less experienced operators. Non-diagnostic ultrasound is caused either by borderline results (e. g. borderline thickening of the appendix to 7 mm) or if the appendix could not be visualized. Non-visualization should be minimized by training and ultrasound experience [106] [107]. If the appendix cannot be visualized, the report should include information as to whether secondary findings in the right lower abdomen were present or not [108].

Visualization of the appendix and especially the search for secondary sonographic features can be taught even to less experienced investigators [83] [109] [110] [111] [112]. A structured training program, the use of standardized ultrasound reporting templates and regular feedback enhance the accuracy of ultrasound and dramatically reduce the number of non-diagnostic ultrasound scans [8] [77] [108] [113] [114] [115] [116] [117] [118]. In this way, the use of CT for patients with an equivocal ultrasound result, costs and admission for observation can be reduced [114].

3. Acute diverticulitis

3.1. Prevalence and clinical spectrum of acute diverticulitis

Colonic diverticula are a common condition, especially in elderly people in Western populations. Complications such as diverticulitis and diverticular bleeding are a frequent cause of hospital admission [119]. Acute diverticulitis occurs in approximately 5 % of people with diverticula, sometimes in recurrent episodes [120] [121]. The incidence of acute diverticulitis seems to have increased during the last years, especially in young and obese subjects [119].

For many years the diagnosis of acute diverticulitis was made clinically, by the triad of left-sided abdominal pain, fever and laboratory markers of inflammation. However, systematic evaluation revealed a high rate of incorrect diagnosis [122] [123], and additional imaging was recommended in cases of suspected diverticulitis [124] [125] [126] [127] [128]. Furthermore, imaging procedures enable us to differentiate uncomplicated from complicated diverticulitis. Roughly, 15 % of patients have complicated disease, defined as an abscess, perforation, fistula, or stenosis [124].

3.2. Examination technique

The scanning techniques for evaluating the colon are described in detail in part 1 of the EFSUMB recommendations for GIUS [1] and in the WFUMB position papers [117] [118]. The graded compression technique is used as described in appendicitis. The easiest way to start your search is at the point of maximum tenderness pointed out by the patient [129] [130]. Alternatively, the sigmoid colon could be localized ventral to the left iliac artery in a cross section and from there be tracked distally and orally to the descending colon. Particularly, for the lower sigmoid, a moderately filled urinary bladder may be beneficial.

3.3. Classification of acute diverticulitis

Various classifications of acute and chronic diverticulitis have been published and modified during the last 55 years [128] [131]. The first of these classifications was based on clinical and surgical findings [132]. In 1978, Hinchey’s original classification [133] divided complicated diverticulitis into four stages (from local abscess to generalized fecal peritonitis). Hinchey’s classification was refined and amended several times and, until today, in various modifications, it remains the basis of most classifications.

Most of the current classifications are based on CT findings [134], but, to this day, not even the use of intravenous or rectal contrast agents is standardized. Ultrasound as a “point-of-care” method that is available in almost every emergency department proved to be able to confirm and classify acute diverticulitis as well [130] [135] [136].

In 2014, the German Society of Gastroenterology (DGVS) and the Society of Visceral Surgery (DGAV) agreed on another classification as part of the new German S2k guidelines: Classification of Diverticular Disease (CDD) [125]. This classification is not linked to a specific diagnostic preference, such as CT versus ultrasonography [137] [138]. However, all guidelines distinguish between uncomplicated and complicated diverticulitis. Complications are generally defined as abscess, perforation, fistula or stenosis [128] ([Table 2]).

Table 2 Classification of Diverticular Disease (CDD) 2014.

type 0	asymptomatic diverticulosis
type 1	acute uncomplicated diverticulitis 1a: without phlegmonous reaction 1b: phlegmonous reaction (colon/surroundings)
type 2	acute complicated diverticulitis 2a Microabscess (< 1 cm) 2b Macroabscess 2c Free perforation
type 3	chronic diverticular disease
type 4	diverticular bleeding

3.4. Sonography in uncomplicated diverticulitis

Uninflamed colonic diverticula can be detected as outpouchings of the colonic wall, often containing gaseous feces or fecaliths, sometimes associated with acoustic shadowing [136] [139] [140]. Particularly, sigmoid colon diverticulosis may be associated with slight thickening of the muscularis propria (the outer hypoechoic layer), caused by a hypertrophied circular smooth muscle.

The following three criteria allow the sonographic diagnosis of acute diverticulitis [130] [136] [139] [141]:

1. Short segmental colonic wall thickening (> 5 mm).

2. Demonstration of the inflamed diverticulum in the wall-thickened area (in contrast to normal diverticula, they are often hypoechoic and are surrounded by hyperechoic fatty tissue).

3. Pericolic tissue changes (non-compressible, hyperechoic).

All three signs correlate very well with the point of maximum tenderness and can be evoked by the graded compression, with the ultrasound transducer (dynamic examination).

These criteria have been confirmed by prospective studies and two meta-analyses, providing high diagnostic accuracy, with a sensitivity and positive predictive value above 90 % [7] [135] [142] [143] [144] [145]. The diagnostic accuracy remains slightly inferior to that of CT scan, particularly in obese patients and in deeply seated lesions in the pelvis. In contrast to the United States, sonography is used as the first-line imaging modality in some European countries and most developing countries [125] [137] [146] [147] [148] [149]. A step-up strategy with US as the first-line method followed by CT whenever US is inconclusive or unreliable seems to represent the most effective approach [150].

3.5. Sonography in complicated diverticulitis

In cases of severe diverticulitis, greater thickening of the colonic wall and increasing paracolic tissue changes can be found. The typical complications of acute diverticulitis include abscess formation, fistulas, perforation and stenosis (CDD type 2).

The US morphology of diverticular abscesses varies widely: they usually appear as hypoechoic fluid collections, sometimes containing echogenic debris and gas bubbles. Hyperechoic, gas-containing abscesses are sometimes difficult to differentiate from bowel loops [151]. In unclear cases with a suspected abscess deep in the pelvis or a gas-containing abscess, additional CT should be performed.

Contrast-enhanced ultrasound (CEUS) is an accurate method for differentiating between intra-abdominal phlegmon and abscess, which both may manifest as hypoechoic masses [152]. CEUS may help to better define the size of the fluid collections and guide sonographic intervention.

Fistulas may present as hypoechoic bands with or without central gas bubbles. Fistulas can involve an adjacent bowel loop, the bladder, or the uterus [140]. Gas in the urinary bladder is an indirect sign of a sigmoid-vesical fistula.

The typical signs of perforation are gas bubbles outside the bowel loops. Contained perforations, fistulas and abscesses are characterized by air bubbles in the mesenterium or in an echo-poor fluid collection. Free peritoneal air or air bubbles in the retroperitoneal space, indicate free or retroperitoneal perforation [137] [153].

3.6. Unusual locations of diverticulitis

Right-sided diverticulitis tends to occur in younger patients and is more frequent in the Far East. The sonographic signs are identical to those of left-sided diverticulitis and ultrasound usually allows differentiation from acute appendicitis [40] [154].

The lower sigmoid colon may be difficult to assess by transabdominal ultrasound and represents a blind spot of GIUS. Especially if the bladder is empty, lower diverticulitis in the deep pelvic region cannot be ruled out by ultrasound. As an alternative to CT or MRI imaging, additional transvaginal or transrectal ultrasound can be used [155] [156] but its use is not widespread.

3.7. The role of US in the treatment of diverticular abscesses

GIUS is a versatile tool for diagnosing paracolic abscesses in complicated diverticulitis. In some special cases, such as distant mesenteric or deep pelvic abscesses, CT has definite advantages for detection. For estimation of the real extension, CEUS may be helpful before intervention [152] [157] [158] [159]. Microabscesses (CDD 2a) and other small abscesses (up to 3 cm) can be treated successfully with antibiotics alone [125] [146] [149] [160] [161] [162]. For large abscesses (> 3 cm) percutaneous drainage combined with antibiotics is the first choice and can significantly reduce the risk of death compared to patients undergoing acute surgery [160]. In borderline abscess, single puncture (or repeated puncture) with aspiration may be sufficient, while drainage with small catheters (7 – 10 Ch) is more effective in larger abscesses [163] [164] [165]. Percutaneous drainage can be performed with ultrasound or CT guidance. If visible by sonography and technically feasible, ultrasound guidance allows real-time control of the puncture [158]. Drains are flushed several times daily and may be removed after imaging control when purulent production has ceased [149]. Injecting an ultrasound contrast agent (SonoVue, some drops diluted in saline) into the cavity through a needle or catheter can prove communication with the bowel lumen or display complex abscess systems [159] [166].

3.8. Comparison of GIUS with other imaging methods

Overall, there are a limited number of published studies reporting the direct comparison of different imaging procedures, considering the large number of affected patients. Two systematic reviews and meta-analyses demonstrated a similar accuracy of CT and ultrasound for the diagnosis of acute diverticulitis [142] [144] ([Table 3]).

Table 3 Comparison between GIUS, CT and MRI in two metanalyses [142] [144].

method	summary sensitivity	summary specificity	metanalysis
US	92 %	90 %	Lameris 2008
	90 %	90 %	Andeweg 2014
CT	94 %	99 %	Lameris 2008
	95 %	96 %	Andeweg 2014
MRI	–	–	Lameris 2008
	98 %	70 – 78 %	Andeweg 2014

In both metanalyses and most head-to-head studies, ultrasound and CT were comparable with respect to the diagnosis of diverticulitis and were superior to other modalities. CT had the advantage of higher specificity and the ability to identify alternative diagnoses [144]. The role of MRI in diagnosing acute diverticulitis is not yet clear and it is not recommended as a first-line diagnostic procedure [128] [144]. Studies comparing CT staging with intraoperative and histologic findings raise doubts as to whether CT is really the “gold standard”. In phlegmonous diverticulitis (CDD 1b; Hinchey IIa), CT resulted in overstaging in 33 % of the patients [167]. Another comparison to surgery revealed considerable inaccuracy of CT in complicated diverticulitis: patients with Hinchey type III (purulent peritonitis) were understaged as Hinchey type I or II [168].

Similar studies between ultrasound and intraoperative findings are still lacking. In addition, there is only minimal data regarding ultrasound in major complications, such as distant mesenteric and pelvic abscesses or free perforation.

However, as with any artform or advanced skill, there is a large learning curve. It must be clear that little experience with GIUS inevitably yields unsatisfactory results and it has been shown that less than 500 completed examinations is insufficient [169] [170].

3.9. Diagnostic strategy

Current guidelines suggest that the diagnosis in all patients with a clinical suspicion of acute diverticulitis must be confirmed by imaging on admission. As treatment strategies have become less aggressive and more tailored to the stage of diverticulitis, accurate staging of the disease has become increasingly important [127] [171] [172]. Due to the similar sensitivity and specificity of US and CT, EFSUMB recommends GIUS as the first-line imaging modality in suspected acute diverticulitis. Common advantages are bedside availability, low costs and the absence of radiation and contrast-induced nephropathy. Especially in cases of uncomplicated diverticulitis, GIUS is the only imaging method needed in acute assessment. If there is no evidence of early and significant clinical improvement, a “second look” 72 hours later may be helpful to rule out the need for intervention or surgery [170]. This second assessment can easily be done by GIUS in most cases.

CT may work as a backup after inconclusive or negative US examinations and has particular advantages for disease located in the distal sigmoid, inflammation deep in the small pelvis or insufficient US scanning conditions (e. g. in obesity). Additional CT may be helpful in planning drainage or immediate surgery in complicated cases. This step-up-approach (ultrasound first and CT only in case of a negative or inconclusive ultrasound examination) has proven to yield the best accuracy [126] [169] [173]. Ultrasound first has been incorporated in more and more European guidelines [124] [125] [128] [174]. Advantages in ultrasound technology and specific training in GIUS (e. g. in emergency medicine) will even strengthen this position in the coming years.

Conflict of Interest

Speaker honoraria, Pentax Medical Singapore Ltd

Consulting/Advisory board, Mediglobe Corporation Gmbh

Congress participation support, Hitachi Medical Systems UK

Speaker honoraria, Abbvie, Janssen, Takeda

Speaker honoraria, Bracco, Hitachi, GE, Mindray, Supersonic, Pentax, Olympus, Fuji,

Boston Scientific, AbbVie, Falk Foundation, Novartis, Roche; Advisory

Board Member, Hitachi, Mindray, Siemens; Research grant, GE

Mindray, SuperSonic

Speaker honoraria, AbbVie, Bracco, Almirall, GE Healthcare, Takeda AS, Meda AS, Ferring AS, Allega

Consultant fee Bracco, GE Healthcare, Takeda and Samsung

Speaker honoraria, Abbvie, Falk Foundation, Ferring, Janssen-Cilag, MSD, Pfizer, Takeda;

Advisory Board/Consultant fee: Abbvie, Celgene, Janssen-Cilag, MSD, Takeda

Speaker honoraria, Abbvie, Alfa Sigma, Janssen-Cilag; Advisory Board/Consultant fee, Allergan, Novartis, Takeda, THD

Speaker honoraria, Falk Foundation; Research grant, GE Healthcare

Speaker honoraria, Meda AS, Ferring pharmaceuticals, Takeda

Speaker honoraria, Philips, GE, Canon; Advisory Board Member, Siemens; Congress participation support, Siemens

Speaker honoraria Bracco, Toshiba. Advisory board member Bracco. Education support Philips. Technical consultancy Philips, BK

The following members declared no conflicts of interest: 

Klaus Dirks, Trygve Hausken, Antony Higginson, Alois Holleweger, Nadia Palotta, Tomás Ripollés, Laura Romanini, Carla Serra

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