Gallbladder

Gallbladder ultrasound: sonographic anatomy and technique

KEY POINTS 

  • Topographically, the gallbladder typically lies on the inferior visceral surface of the liver at the gallbladder fossa.
  •  Usually located in the midclavicular line, just below the right lower costal margin (Figure 1).
  •  Stores and expels bile into duodenum.
  • It comprises a fundus, body and neck (Figure 4 and 5).
  • The gallbladder often lies obliquely within the abdomen, which is important to appreciate for positioning the transducer correctly to image the long and short-axes of the gallbladder.

Fig 1. Gallbladder (GB) is located in midclavicular line (MCL), below the lower costal margin at the gallbladder fossa inferior to right hepatic lobe. 

TECHNIQUE

First of all, to properly identify and scan the gallbladder,  some technical conditions and machine parameters must be fulfilled (Table 1 and 2).

Table 1. Gallbladder scanning technique

Table 2. Suitable machine parameters

Gallbladder identification

    Along the midclavicular line, place the probe obliquely just below the righ costal arch (right subcostal region). Ask the patient for deep inspiration and angulate the probe cranially up into the liver in a steep angle. At this angle you will see the most cranial liver segments and vascular structures comprised by the hepatic veins and inferior vena cava (Fig. 2A). Then, slowly angulate the probe donward. At a most caudal scan you will visualize the portal bifurcation, special attention to the umbilical segment (U) of the left portal vein (Fig. 2B). Ligamentum teres (LT) travels from the umbilicus to the anterior aspect of the umbilical segment (U) of the left portal vein. Continuing the scanning inferiorly, we will depict the  ligamentum teres (LT), interlobar fissure (ILF) and the right portal vein (RPV) (Fig. 2C). Keeping the downward movement the gallbladder (GB) will appear immediately beneath the ILF (Fig 2D). 

Fig.2 At an oblique subcostal projection the gallbladder (GB) is positioned beneath the liver immediately adjacent to interlobar fissure (ILF). 

TIP 

 The interlobar fissure (ILF) is a landmark that separates the two hepatic lobes and is seen as a bright linear echo within the liver connecting the gallbladder fossa and the right portal vein (RPV). It can be a useful landmark for locating small contracted gallbladders or gallbladder completely filled with gallstones. 

Fig.3 At a subcostal longitudinal projection you should use sliding movements along the subcostal margin to find the gallbladder. The gallbladder (GB) should be seen conected to right portal vein (RPV) by the interlobar fissure (ILF). 

 ANATOMY

Fig.4 Right subcostal oblique section depicting a pear-shaped echo-free structure, the gallbladder (GB). 

The gallbladder usually is divided into three parts:

- Fundus: is the rounded distal tip. It usually projects below the inferior margin of the liver, where it comes into contact with the anterior abdominal wall.

- Body: is the midportion of the GB, commonly in contact with the duodenum. It generally lies in contact with the visceral surface of the liver and is directed upward, backward and to the left.

- Neck: is the GB portion continuous with the cystic duct. It is oriented posteromedially toward the porta hepatis. 

Note: The infundibulum, also called Hartman's pouch, is a frequent but inconstant finding in the juction of neck of the gallbladder and the cystic duct. It is a common site of lodged gallstones.

Fig.5 Diagram illustrating gallbladder parts.

CHARACTERISTICS OF THE NORMAL GALLBLADDER

REFERENCES:

1. Hertzberg, B.S.;Middleton, W.D. (2015). Gallbladder. In Elsevier, Ultrasound:The requisites (pp. 32-33). Philadelphia, PA. 

2. Barreiros, A.P. (2012). Ultrasound of the biliary system. Retrieved from:www.kosmos-host.co.uk/efsumb.../coursebook-biliary_ch04.pdf

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Written by Dr. Augusto César
Board certified Brazilian radiologist, co-founder of the Salus Sonography project and Medultra smartphone app. Currently works as an interventional and general radiologist in private practice, São Paulo, Brazil.

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