Chapter 11
The upper abdomen
Stefan Posth1 and Ole Graumann2,3,4
1Dept of Emergency Medicine, Odense University Hospital, Odense, Denmark. 2Dept of Radiology, Odense University Hospital, Odense, Denmark. 3Dept of Clinical Medicine, Odense University, Odense, Denmark. 4Dept of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Correspondence: Stefan Posth, Kløvervænget 25, 5000 Odense C, Denmark. E-mail: stefan.posth@rsyd.dk
When carrying out an US scan of the thorax, the examiner will also detect structures in the upper abdomen. Incidental abdominal pathologies may be detected with varying frequency during TUS. In this chapter, we provide an overview of the most common pathologies. Clinicians should be aware of the technical challenges when interpreting abnormal US patterns. Examiners who normally only examine the thorax may not be familiar with the abdominal organs. It is therefore essential that a specialist opinion is requested when a possible pathology is detected.
Cite as: Posth S, Graumann O. The upper abdomen. In: Laursen CB, Rahman NM, Volpicelli G, eds. Thoracic Ultrasound (ERS Monograph). Sheffield, European Respiratory Society, 2018; pp. 148–160 [https://doi.org/10.1183/2312508X.10007417].
When performing US of the lungs, anatomical structures in the upper abdomen will inevitably also be visualised.
Although the focus of this Monograph is US pathologies in the thorax, it is important for the examiner to be familiar with the most common pathological findings in the upper abdomen. It is not the purpose of this chapter to go through all possible pathologies but rather to draw attention to pathologies that require transferral to another specialist, for example a radiologist, for further examination. We will review pathologies in the right upper abdominal quadrant, the epigastrium and the left upper abdominal quadrant.
A number of studies have considered the question of which pathologies would be expected in an unselected group of patients, many of whom do not present with obvious abdominal problems. Table 1 summarises the pathological findings of these studies.
Table 1. Summary of studies of pathologies detected during abdominal US in unselected patients
Anatomy of the upper abdomen
When performing US of the thorax, organs in the upper abdomen will also be visualised. Table 2 offers an overview of abdominal organs that can be seen while scanning sections of the thorax. This is discussed further in another chapter in this Monograph [8]. If incidental relevant or undefinable pathology is detected in the upper abdomen, the patient should be referred to a specialist, such as a radiologist or gastroenterologist.
Table 2. Abdominal organs seen during TUS
Thorax section | Abdominal organs |
|---|---|
R2 | Liver, gallbladder, bile ducts, inferior vena cava, abdominal aorta, pancreas |
R3 | Liver, gallbladder, bile ducts, kidney |
R5 | Liver, bile ducts, kidney |
L2 | Inferior vena cava, abdominal aorta, pancreas, bile ducts, stomach |
L3 | Spleen, kidney, stomach |
L5 | Spleen, kidney |
Frequent pathologies in the right upper abdominal quadrant
The US anatomy of the right upper abdominal quadrant of a healthy subject is shown in figure 1a and b. Pathologies in this section can occur in the liver, gallbladder, bile ducts or right kidney.
Figure 1. a and b) Normal anatomy of the right upper abdominal quadrant; c–f) normal anatomy of the epigastrium; g and h) normal anatomy of the left upper abdominal quadrant.
Liver pathologies
The most common liver pathologies are steatosis, cysts and focal lesions [9].
Hepatic steatosis and liver cirrhosis
Hepatic steatosis is characterised by increased echogenicity of the liver compared with the kidney parenchyma (figure 2a). Hypoechoic areas in the liver hilum can often be seen. Sonographic signs of liver cirrhosis include inhomogeneous liver parenchyma, an irregular and nodular liver surface, and a variety of other possible findings including destroyed vascular architecture. Ascites is frequently present (figure 2b and c).
Figure 2. a) Liver steatosis; b and c) liver cirrhosis.
Focal liver lesions
Focal liver lesions include liver cysts, calcifications, and benign and malignant lesions.
Sonomorphologically, cysts are characterised as round, anechoic, smoothly delineated structures with refraction shadows at the edges, a strong posterior wall echo and enhancement below the cysts (figure 3a). Atypical cysts do not fulfil all of these sonographic signs. Calcifications present as echo-rich structures with acoustic shadowing distally (figure 3b).
Figure 3. a) Liver cyst; b) liver calcification; c) hepatic haemangioma (*); d) focal nodular hyperplasia (*); e and f) hypoechoic liver metastasis (*); g) hyperechoic liver metastasis and cholestasis (*).
Even for an experienced specialist, it is challenging to differentiate between benign and malignant focal liver lesions with standard US, and supplementary advanced imaging is often needed for a correct diagnosis. Widespread metastatic liver disease can be impossible to detect with normal B-mode, but when a solid lesion is seen, there are some characteristics for both benign and malign lesions.
Hepatic haemangiomas
Hepatic haemangiomas are the most common benign liver lesion. They typically are <3 cm in diameter, round and may be lobulated with a smooth outline. They are located adjacent to liver vessels, often near to the liver capsule, and demonstrate a homogeneous, echo-rich texture (figure 3c). Due to the presence of only capillary-sized blood vessels, there is often no flow detected with Doppler US.
Focal nodular hyperplasia
Focal nodular hyperplasia is usually an isoechoic lesion of variable size, with a central scar and calcifications (figure 3d). These lesions are mostly hypervascularised, with a central arterial blood supply, causing a so-called wheel-spoke phenomenon in colour Doppler mode.
Hepatocellular adenoma
A hepatocellular adenoma is usually isoechogenic with the surrounding liver tissue. Therefore, it can be very difficult to differentiate an adenoma from the surrounding liver tissue. In a fatty liver, adenomas may be poorly echogenic.
Liver metastases
Liver metastases have a wide variety of B-mode appearances, from isoechogenic with the surrounding liver tissue, and therefore impossible to detect, to hyperechoic or hypoechoic (figure 3e–g). They may be confused with any kind of liver lesion.
Bile duct pathologies: cholestasis
The most frequent pathology of the bile ducts is cholestasis [10]. The major sonographic feature of cholestasis, which can be caused by multiple diseases, is dilation of the intra- and extrahepatic biliary ducts (figure 4a and b). In intrahepatic cholestasis, two anechoic tubes are seen side by side, or the dilated bile ducts and adjacent portal vein branch are seen as two adjacent anechoic circles. This phenomenon, which is also called “double tracking” or “multiple tubes”, can occur in part of the liver or, if the cause of cholestasis is extrahepatic, in the whole liver.
