Sonography is used mainly on account of widespread availability and the fact that no radiation is used. First of all, diagnosing appendicitis needs suffi cient skill and expertise in the performance of gastrointestinal ultrasound. Various compression techniques are used to visualize. Usually, the abdomen and the retroperitoneum are examined with the 3.5-MHz transducer. Then the caecum, which usually contains gas, is localised. Most often the appendix originates caudal to Bauhin’s valve. The position of the appendix is highly variable. Artrocaecal position or a position within the small pelvis may be found, Normally the appendix is compressible with an ovoid confi guration in the transverse section. The antero-posterior diameter is normally <6 mm. Compared with the terminal ileum, no peristalsis is visualised in the normal appendix. In a study by Rettenbacher et al. (1997), it was shown that the normal appendix is localised sonographically in 50–70% of cases. Frequently, a high-resolution transducer is used to visualize the appendix during graded compression. In many cases, the appendiceal region can be seen with transabdominal 7.5-MHz transducers. The use of colour- or power Doppler may be useful; however, use of the Doppler methods is not mandatory. Ultrasound contrast media have been used for the detection of hypervascularisation (Incesu et al.2004). Harmonic imaging is presently the standard technique in the abdomen. The main advantage is the higher signal-to-noise ratio, but the depth of penetration is lower with this technique (Table below). Sonographic signs of acute appendicitis and Round confi guration in the transverse section (see Fig. below). Antero-posterior (a.p.) diameter of 6 mm or more (see Fig. below). In some cases with lymphatic hyperplasia the a.p. diameter is >6 mm.
Ultrasound images Acute appendicitis. In transverse section, the appendix is round and measures 12 mm in diameter.
Ultrasound images Acute appendicitis Longitudinal panoramic section.Alteration of the periappendiceal fat
Ultrasound images Transverse section in appendicitis. The appendix is enlarged and reveals echogenic alteration of the surrounding fat
Hypervascularisation of the appendix in colour Doppler
Ultrasound images Transverse section in appendicitis with hyperaemia and thickened wall surrounded by echogenic, hyperaemic fat
Faecolith in the appendix, with obstruction
ultrasound images Obstructed appendix with faecoliths (asterisk) and infl ammatory content In diffi cult patients and in women, also a transrectal or transvaginal approach may visualise appendiceal region and appendicitis (Figs. below).
Ultrasound images Transrectal sonography displays acute appendicitis with echogenic fat reaction If severe complications, such as signifi cant perforation (Fig.A) or abscess formation (Fig.B), are present, the appendix often cannot be visualized as the origin of the infl ammation. In these cases, computed tomogrphy (CT) should be performed in order to completely delineate the infl ammation and to visualise a safe path for a transabdominal drainage; however, the drainage can be performed under US guidance.
Fig. A Ultrasound images of Longitudinal section of an acute perforated appendicitis.
Fig. B Perithyplitic abscess. The appendix can no longer be displayed The accuracy of sonography in diagnosing appendicitis varies between 70 and 95% depending on the study (Chan et al. 2005; Kessler et al. 2004; Lee et al. 2005; Puylaert et al. 1986a; Rettenbacher et al. 2002; van Breda Vriesman et al. 2003). In the present author’s opinion, accuracies over 90% can be achieved if sonography is performed by an experienced team (Gritzmann et al. 2002). It is generally accepted that sonography should be performed in clinically, questionable cases, in order to reduce the high rate of false-negative appendectomies; however, in clinically, highly suspicious cases the incidence of acute appendicitis was only about 70%; therefore, it was advocated that sonography be performed in all cases with pain in the right lower quadrant (Rettenbacher et al. 2002). An acute appendicitis can be excluded if the normal appendix can be completely displayed and/ or a differential diagnosis that explains the clinical fi ndings can be found.
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