The easiest approach for visualisation of the splenic vessels is a transverse section through the upper abdomen. The artery runs at the superior border of the pancreas, usually localised more cranially than the vein. The middle portion of the artery can also be shown in longitudinal sections through the upper abdomen with the transducer slightly angled to the left side (Fig. 7.4a–f). The artery is always neighboured by the splenic vein, which can be imaged behind the pancreatic corpus and tail in transverse and longitudinal sections (Fig. 7.5a–d). Using B-mode ultrasonography (US) alone, both vessels cannot be exactly distinguished. With the help of the different Doppler techniques (colour or spectral Doppler), however, artery and vein can easily be differentiated. From the left lateral intercostal approach, the splenic hilus and the intrasplenic vessels can be demonstrated (Fig. 7.6a, b).

The investigation of the spleen can be performed non-fasting and without special preparation in the supine position or lying on the right side.

Transducers: The appropriate transducer frequency has to be chosen depending on the age/size of the patient and the indication. In neonates, infants and for the detection of smaller focal lesions, high-resolution linear transducers up to 15 MHz are optimal (Fig. 7.7a, b). Older children, especially obese adolescents, are best investigated with a curved array transducer <6 MHz, followed by an additional approach with a high-frequency transducer in order to detect smaller lesions, discontinuation of the splenic surface in cases of trauma and superficial minor vascular pathologies, which may not be detected with low-frequency curved array scanning (Fig. 7.9).

The spleen is often injured in accidents, although it is shielded by the ribs of the left hemithorax, which usually protects the spleen from laceration. Enlarged spleens which tower below the costal arch are extremely vulnerable. In blunt abdominal trauma, injury of the spleen must always be ruled out as the spleen is the most common injured abdominal organ accounting for up to 45 % of all visceral injuries (Tataria et al. 2007). An enlarged spleen is far more at risk of being injured after blunt abdominal trauma. Sonographic signs of possible spleen injury are free abdominal fluid with internal echoes, splenomegaly, reduced respiratory movement, inhomogeneous texture of the spleen, subcapsular haematoma, anechoic lacerations within the parenchyma or disruption of the splenic capsule (Hofmann 2005) (Figs. 7.9a–d and 7.10a, b). In many emergency rooms, a FAST (focal abdominal sonography for trauma) protocol with scanning of the four abdominal quadrants for free fluid, as a sign for haemoperitoneum, is done and later followed by a complete and detailed US investigation after deciding on surgical or conservative therapy for a trauma patient. However, in a study by Richards in 2002, 12 % of children with abdominal injury had no free fluid. Contusions, lacerations, ruptures, fractures, subcapsular and perisplenic haematoma (Figs. 7.9b and 7.10a) of the spleen may be distinguished. Haemoperitoneum and active bleeding are the most likely indications for surgical intervention. Due to the thicker splenic capsule in children, operations in splenic trauma are less frequently compared to adults. In paediatric patients, haemodynamic stability is the most important determinant for conservative treatment. Following trauma, splenic healing can rapidly be observed. This was experienced in the last decades of predominately successful conservative management of splenic injuries. Because of devastating post-splenectomy infections with encapsulated bacteria such as Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae, splenectomy should be avoided whenever possible.

Long-term sequelae of splenic injury may be scarring of parts of the spleen, development of posttraumatic pseudocysts, polysplenia and calcification (Fig. 7.11). In 15–30 % of patients, a two-phase delayed splenic rupture may be expected within 2 weeks. Delayed complications, such as splenic abscesses and pseudoaneurysms of the splenic artery and its branches, have been observed (Lynn et al. 2009). To detect complications, a short follow-up by B-mode sonography and CDS should be scheduled (Goletti et al. 1996). In cases of suspected splenic injury, CDS with low flow settings and a low wall filter should be used (Fig. 7.12a). If a high-frequency curved array probe is used, power Doppler is especially helpful for the diagnosis of focal hypoperfusion of the organ (Fig. 7.12b). Areas without perfusion can be distinguished from the surrounding normal vascularised parenchyma. Lacerations are displayed as focal hypoechoic lesions. Power Doppler reveals missing perfusion, often in a triangular shape. Acute posttraumatic injury and lacerations of the spleen may not be visualised with B-mode due to diffuse swelling of the organ. In the detection of traumatic splenic injury, CEUS (contrast-enhanced ultrasonography) is much more sensitive than mere B-mode and Doppler US alone (see Sect. 7.8, Fig. 7.13; Manetta et al. 2009; Weskott 2013).