Gallbladder and Cystic Duct

4.1 Normal Anatomy and Variants

# 92 Gallbladder

KEY FACTS: ANATOMY (GORE ET AL. 1994)

●The gallbladder is located in a fossa on the lower surface of the liver between the right and left lobes

●Normal wall thickness: < 2–3 mm

●Divided into four parts: fundus, body, infundibulum, and neck

KEY FACTS: VARIANTS

●Location (e.g.,may be intrahepatic,suprahepatic, retroperitoneal)

●Content: sludge (calcium bilirubinate granules and cholesterol crystals), commonly found during prolonged fasting and hyperalimentation (Fig. 92a, b)

●Classification of septa:

–Longitudinal septum (= duplication; 1 in 3000 to 1 in 12000);

–Isolated transverse septum

–Phrygian cap: 2%–6% of population, kinking/folding of fundus and sometimes septum; Fig. 92c, d)

●Size (“cholecystomegaly” vs. “microgallbladder”)

KEY FACTS: MRI (BRET AND REINHOLD 1997)

●Signal intensity of gallbladder content:

–T2: hyperintense

–T1: variable, depending on the composition and concentration of bile (higher signal intensity in patients fasting for several hours; Demas et al. 1985)

●The normal gallbladder wall is thin and hypointense relative to retroperitoneal fat on non-fat-suppressed snapshot T2weighted MR images

●Signal intensity of sludge (Fig. 92a, b):

–T1: hyperintense

–T2: slightly hypointense (differential diagnosis with stones: shape)

References

Bret P, Reinhold C (1997) MRI of the gallbladder. In: Rossi P (ed) Biliary tract radiology. Springer, Berlin Heidelberg New York, pp 59–69

Demas BE, Hricak H, Moseley M et al. (1985) Gallbladder bile: an experimental study in dogs using MR imaging and proton MR spectroscopy. Radiology 157 : 453–455

Freeny PC, Stevenson GW (1994) Margulis and Burhenne’s alimentary tract Radiology, 5th edn. Mosby, St Louis

Gore RM, Ghahremani GG, Fernbach SK (1994) Gallbladder: anomalies and anatomic variants. In: Gore RM, Levine MS, Laufer I (eds) Textbook of gastrointestinal radiology. Saunders, Philadelphia, pp 1621–1635

Hakansson K, Christoffersson JO, Leander P et al. (2002) On the appearance of bile in clinical MR cholangiopancreatography. Acta Radiol 43 : 401– 410

Fig. 92 a, b. Sludge. a T1and b T2-weighted images showing sludge in dependent portion of the gallbladder. c, d Phrygian cap. c Projective image showing folding of fundus with larger diameter of

the distal part and presence of a septum (arrowheads). d Axial T2-weighted image showing septum (arrows). Note higher signal intensity of bile within the fundus

#93 Cystic Duct

Related topics: #27, 28 (intrahepatic bile ducts, variant anatomy), #82, 83 (extrahepatic duct, complications after cholecystectomy)

KEY FACTS: ANATOMY

●Average diameter: 1.8 mm

●Average length: 2–4 cm

●Course: classically serpiginous with tight S-shaped bends

●Location:

–Distal part usually posterior to the common bile duct (95%)

–May run parallel to the common hepatic duct for a short distance

–In 10%, the two ducts have a long parallel course

●Insertion: the point at which the cystic duct joins the bile duct is quite variable (Shaw et al. 1993) (Fig. 93a):

–Upper part of bile duct (including left or right hepatic duct): ± 30%

–Middle part: ± 60%

–Lower part: ± 10%

KEY FACTS: MRI

●Small,tubular fluid-containing structure between the gallbladder and bile duct

●Usually easily recognized due to its characteristic location and “folded” appearance

●Identification of anatomic variants (high and low insertion, long parallel course) is important if (laparoscopic) cholecystectomy is planned (see #52, 82, 83) (Fig. 93b, c)

References

Schulte SJ (1994) Embryology, normal variation, and congenital anomalies of the gallbladder and biliary tract. In: Freeny PC, Stevenson GW (eds) Marqulis and Burhenne’s alimentary tract radiology. Mosby, St. Louis, pp 1251–1274

Shaw MJ, Dorscher PJ, Vennes JA (1993) Cystic duct anatomy: an endoscopic perspective. Am J Gastroenterol 88 : 2102–2106

Silvis SE (1995) The normal bile duct. In: Silvis S, Rohrmann C, Ansel H (eds) Endoscopic retrograde cholangiopancreatography. Igaku-Shoin, New York, pp 168–192

Turner MA, Fulcher AS (2001) The cystic duct: normal anatomy and disease processes. Radiographics 21 : 3–22