Vaterian Sphincter Complex

5.1 Normal Anatomy and Variants

# 119 Normal Anatomy

KEY FACTS: ANATOMY

●The vaterian sphincter complex includes the distal (intramural) part of the common bile duct and pancreatic duct, the papilla, and the surrounding smooth muscle (sphincter of Oddi) (Fig. 119a)

●Length of vaterian sphincter complex: 10–15 mm

●Course: oblique in a laterocaudal direction

●Diameter of intramural duct: a few millimeters

●In 60%–80% of individuals,the pancreatic and bile ducts unite to form a common channel (length, 2–15 mm; average, 5 mm; Misra and Dwivedi 1990; see # 123)

●The slightly dilated distal segment of the common channel is also called the ampulla

●The papilla forms an endoluminal protrusion at the medial wall of the duode-

num and contains the orifice

● Size of papilla: usually less than 10–

15 mm

●Shape of papilla: variable (may be polypoid)

●Location of papilla:

– Usually (92%) located at the posteromedial wall of the mid-descending duodenum

– Can be anywhere between the pylorus and the ligament of Treitz

●Location of minor papilla: 1–2 cm proximal to the major papilla

KEY FACTS: MRI

●If MRI is performed during relaxation of the sphincter, images show the distal portion of the pancreatic duct and common bile duct as thin, fluid-containing structures connected with the duodenum (Fig. 119b)

●Nonvisualization is a normal variant if

only single images are obtained (see

# 120; Van Hoe et al. 1998)

●The papilla may be seen as an endoluminal protrusion at the medial wall of the duodenum

References

Misra SP, Dwivedi M (1990) Pancreaticobiliary ductal union. Gut 31 : 1144–1149

Stewart E, Vennes J, Geenen J (1977) Atlas of endoscopic retrograde cholangiopancreatography. Mosby, St Louis, p 41

Van Hoe L, Gryspeerdt S, Vanbeckevoort D et al. (1998) Normal Vaterian sphincter complex: evaluation of morphology and contractility with dynamic single-shot MR cholangiography. AJR 170 : 1497–1500

#121 Variant Anatomy (1):

Type of Junction

KEY FACTS: ANATOMY

●The junction between the distal common bile duct and the pancreatic duct can be classified as follows:

–Y-type junction (± 70%)

–V-type junction (± 20%)

–U-type junction (± 10%)

–Other types (rare)

●In less than 0.2% of patients, the common bile duct and pancreatic ducts have separate orifices

References

Bocker V, Stolte M (1979) Functionelle Morphologie. In: Ottenjann R, Classen M (eds) Gastroenterologische Endoskopie. Enke, Stuttgart, pp 142–149 Wiedmeyer DA, Sewart ET, Taylor AJ (1993) Radiologic evaluation of structure and function of the sphincter of Oddi. Gastrointest Endoscop Clin

North Am 3 : 13–40

a

b

Fig. 121. a Y-type (left), V-type (center), and U- type junction (right). CBD, common bile duct; PD, pancreatic duct. (Reprinted with permission from Wiedmeyer et al. 1993). b–d Projective images showing junction with b Y-type, c V-type, and d U-type morphology (arrows)

c

d

#122 Variant Anatomy (2):

“Pseudocalculus” Sign

Related topics: # 73 (stones in common bile duct: pitfalls in diagnosis), # 125 (impacted stone)

KEY FACTS

●Pseudocalculus sign: concave aspect of distal border of suprasphincteric part of the common bile duct, mimicking a stone (Fig. 122)

●Cause: forceful contraction of the sphincter with retrograde “invagination”

●Normal variant

●Potential cause of false-positive MR ! diagnosis of common bile duct lithiasis

(if dynamic imaging is not performed)

References

Ferruci J, Wittenberg J, Stone L, Dreyfuss J (1976) Hypotonic cholangiography with glucagon. Radiology 118 : 466–467

Van Hoe L, Gryspeerdt S, Vanbeckevoort D et al. (1998) Normal Vaterian sphincter complex: evaluation of morphology and contractility with dynamic single-shot MR cholangiography. AJR 170 : 1497–1500

Van Hoe L, Mermuys K, Vanhoenacker P (2004) MRCP pitfalls. Abdom Imaging 29 : 360–387

Fig. 122 a – g. a Pseudocalculus sign. Left, the sphincter is relaxed. Right, forceful contraction of the sphincter leads to retrograde invagination (arrow). b, c Projective image obtained during contraction showing pseudocalculus sign (arrow). c Projective image obtained 10 s later showing normal sphincter area (arrows). Note the absence of fluid in the second portion of the duodenum in b

Fig. 122 a – g. (continued) d, e Other patient. Projective images obtained within a 15-s interval.Again, the aspect of the distal common bile duct in d could erroneously be interpreted as a small stone (arrow). f , g. Different patient. Projective image during for-

ceful sphincter contraction (f) showing retrograde invagination resulting in the pseudocalculus sign (arrow). Projective image obtained 20-s later (g) showing a normal sphincter area (arrow)

#123 Variant Anatomy (3):

Length of Common Channel

KEY FACTS

●In 60%–80%, the pancreatic and bile ducts unite to form a common channel (length, 2–15 mm; average, 5 mm; Kochhar et al. 1989)

●Presence of an anomalous pancreaticobiliary duct union (common channel greater than 15 mm in length) may predispose to intrabiliary reflux of pancreatic juice and formation of a choledochal cyst (see #68)

●Note: A key factor in the evaluation of the length of the common channel is adequate visualization of the exact location of the papilla. In MRI, sufficient filling of the duodenum with fluid is an essential prerequisite

●Note: Techniques to ensure that the duodenum is filled with fluid during an MRCP study:

–Dynamic (repetitive) scanning (mechanism: intermittent passage of fluid)

–Injection of a spasmolytic agent (possible mechanism: increased outflow of bile and/or gastric content; see #21)

–Oral administration of water

References

Hand BH (1962) An anatomical study of the choledochoduodenal area. Br J Surg 50 : 486

Hosoki T,Hasuike Y,Takeda Y et al. (2004) Visualization of pancreaticobiliary reflux in anomalous pancreaticobiliary junction by secretin-stimu- lated dynamic magnetic resonance cholangiopancreatography. Acta Radiol 45 : 375–382

Kochhar R, Nagi B, Chawla S et al (198) The clinical spectrum of anomalous pancreaticobiliary junction. Surg Endoscop 3 : 83–86

#124 Variant Anatomy (4): Papilla in or Adjacent

to a Duodenal Diverticulum

KEY FACTS: ANATOMY

● Incidence of duodenal diverticula: 5%–10% (Shemesh et al. 1987)

●Anatomic relationship to papilla:

–Papilla on the rim of the diverticulum (most common)

–Papilla in the diverticulum (may be a cause of failed ERCP)

●Associations:

–Increased incidence of common bile duct stones

–Possibly also increased incidence of pancreatitis (Osnes et al. 1981)

KEY FACTS: MRI (FIG. 124)

●Appearance of diverticula: paraduodenal structures containing:

–Fluid

–Air

–Air and fluid (with air–fluid level)

● The terminal ducts may be narrowed as they pass around the diverticulum

● If the papilla is within the diverticulum, ! intermittent reflux of air may be seen (may be interpreted as a stone if dynamic imaging is not performed)

●Duodenal diverticula may mimic cystic neoplasms of the pancreas when filled only with fluid (Macari et al. 2003)

References

Balci NC, Noone T, Akun E et al. (2003) Juxtapapillary diverticulum: findings on MRI. J Magn Reson Imaging 17 : 487–492

Macari M, Lazarus D, Israel G, Megibow A (2003) Duodenal diverticula mimicking cystic neoplasms of the pancreas: CT and MR imaging findings in seven patients. AJR Am J Roentgenol 180 : 195–199

Osnes M, Lootveit T, Larsen S, Aune S (1981) Diverticula and their relationship to age, sex, and biliary calculi. Scand J Gastroenterol 16 : 103–107

Shemesh E, Friedman E, Czesniak A, Bat L (1987) The association of biliary and pancreatic anomalies with periampullary duodenal diverticula. Correlation with clinical presentations. Arch Surg 122 : 1055–1057

a

c

Fig. 124 a, b. a Axial T2-weighted image showing a large diverticulum at the medial border of the duodenum (arrow). Note the presence of an air-fluid level. b Projective image showing that the papilla is located adjacent to (not in) the diverticulum (arrow). c–e Other patient. Three consecutively obtained projective images. c Weblike low-intensity structure in the distal common bile duct (arrowheads), representing reflux of air. Note the small duodenal diverticulum (arrows). d The air has disappeared. In addition, the connection between the distal common bile duct and the diverticulum is clearly demonstrated (arrow). e Air refluxing into the bile duct (arrowheads). This case illustrates that small diverticula embedded in the duodenal wall may show temporal changes in size and shape caused by smooth muscle contractions

b

d

e