IMAGING OF GALLBLADDER VARIANTS

H MHALLA (1), S MEZGHANI BOUSSETTA (1)

Department of radiology (1) Hospital of Ben Arous. Tunisia

INTRODUCTION

Routine imaging of the gallbladder demonstrates a wide array of imaging

variants, including anomalies in location, number, and configuration. An

awareness of these normal variants may prevent misdiagnosis and will aid

in evaluation of alternative diagnostic possibilities.

OBJECTIVES

The aim of this study is to describe different radiologic findings of gallbladder

variants and embryological events leading to these variants.

MATERIALS AND METHODS

Retrospective study of five patients.

All of them have consulted in regional hospital of Ben Arous.

Abdominal US exam performed for each of them revealed gallbladder

anomalies.

RESULTS AND DISCUSSION

The mean age was 26 years (8 months- 48 years), clinical symptoms were

right upper quadrant pain (4 cases) for 6 months (2 cases), acute pain (2 cases)

and radiological discovery without clinical symptoms (1 case). 3 patients had

congenital anomalies; mega-urethra (1 case), situs inversus (1cas), congenital

scoliosis (1 case). Gallbladder variants were anomalies in location (2 cases)

retrohepatic and left gallbladder, anomalies of number (2 cases) agenesis and

duplicity and anomalies of configuration (1 case) junctional fold gallbladder.

We can notice different gallbladder variants. Anomalies of number such

as duplicity, accessory, agenesis or triplication, in location such as left

sided, suprahepatic, intrahepatic, retroplaced and mobile gallbladder, and

of configuration such as multiseptate and junctional fold gallbladder.

For a better understanding of these variants, we need to understand the

events occurring at the embryological period.

Embryology

In the fourth week of fetal development, the hepatic diverticulum appears as a

cellular outgrowth of the proximal part of the intestinal tube. The hepatic

diverticulum arises as a sacculation consisting of a cranial portion which

further differentiates into glandular tissue and bile ducts. The main portion of

the hepatic diverticulum elongates to form the common bile and hepatic

ducts. The caudal portion of the hepatic diverticulum becomes the gallbladder

and cystic duct. The gallbladder is a solid epithelial cylinder which is carried

from the duodenum by the elongated common duct.

In the seventh week, a lumen is established within the cystic duct.

Anomalies in Number

Agenesis of the gallbladder is rare, as are duplication anomalies.

Triplication gallbladder is exceptional.

Duplicated Gallbladder

The phenomenon is explained by the duplication of the gallbladder vesicle.

Gallbladder duplication is a rare anomaly. Boyden’s classification of double

gallbladders includes:

(1) bilobed incomplete gallbladder division with one cystic duct

(2) complete gallbladder duplication with separate cystic ducts entering the

common hepatic duct (Figure 1)

(3) complete gallbladder duplication with a common cystic duct entering the

common hepatic duct.

Figure 1: Ultrasonography showing two gallbladders with separate ducts (Type 2 of Boyden’s classification).

Differentiation between the specific types of duplication is usually not possible

with sonography. When stones are present, they may be sequestered in one of

the two lobes. When gallstones can be demonstrated to communicate with all

parts of the gallbladder, a folded gallbladder is more likely than duplication.

A more specific sign of gallbladder duplication may be isolated contraction of

the non-diseased lobe with an absence of contraction of the diseased lobe. This

finding may be useful for differentiating between two gallbladder lobes and

other forms of pericholecystic fluid collection. It may also suggest at least

partial duplication of the cystic duct, since a patent cystic duct must be present

to contract the lobe.

Accessory Gallbladder

Boyden presented two theories explaining accessory gallbladder formation:

- The first suggests that the phenomenon is caused by the primary subdivision

of the embryonic primordium into two parts, and accessory gallbladders

represent an outgrowth of a secondary vesicle from some other portion of the

biliary duct system subsequent to the formation of a definitive gallbladder.

- The second theory supports the idea that bile duct buds occur at the junction

of the hepatic ducts. These duct buds usually regress and disappear. However, if

they persist, gallbladder anomalies such as duplication or triplication may

occur. If the bud originates on one of the hepatic or common ducts, the

accessory gallbladder will contain its own cystic duct. If the bud originates

from the cystic duct, a Y-shaped cystic duct will connect the accessory and the

normal gallbladder to the common duct.

Pseudo duplication gallbladder may simulate a double gallbladder.

Agenesis of gallbladder (Figure 3)

The development of the liver and gallbladder system starts around the third

week of gestation, when the primordial liver, called the hepatic diverticulum, is

formed as an outgrowth of the endodermis of the anterior intestine. As the

diverticulum grows, its connection with the intestine narrows to form the

external hepatic bile duct. A small ventral invagination grows in this narrow

area and gradually forms a vacuole that becomes the gallbladder and cystic

duct. A failure of this invagination results in agenesis of the gallbladder.

Figure 3: A, B: T2 axial slices, C: sequence RARE both showing agenesis of gallbladder which appears as a stump.

Triplication of Gallbladder

Triplication of the gallbladder is a very rare congenital anomaly of the biliary tract.

Gallbladder multiplications are not likely to be discovered unless associated with

cholelithiasis, sludge, cholecystitis and carcinoma. Multiple gallbladders are thought to

be caused by the failure of rudimentary bile ducts to regress during embryological

development. Three distinct types are described:

-The first type is characterized by the presence of multiple gallbladders that drain into

the common bile duct via separate cystic ducts.

- The second type is characterized by the presence of two gallbladders with a common

cystic duct entering the common duct, and a third gallbladder with an independent

cystic duct.

-The third type is characterized by the presence of three gallbladders that share a single

cystic duct.

Anomalies in location

Normally, the gallbladder is adjacent to the undersurface of the liver, in

the plane of the interlobar fissure, with the gallbladder neck maintaining

a constant relationship to the porta hepatis. The gallbladder is routinely

found in the right upper quadrant, but may be seen in any part of the

abdomen. While anomalies of positions are rare, the most common of

these are the left sided, intrahepatic, transverse, and retroplaced

(retrohepatic or retroperitoneal).

A left-sided gallbladder location is seen in situs inversus (Figure. 4).

A gallbladder in the left upper quadrant without situs inversus is even rarer.

There are several explanations for that:

-The first is that, the normal gallbladder bud may migrate to the left lobe instead

of the right, and lie on the left side of the ligamentum teres. In this situation, the

portal vein, biliary tree and hepatic artery should be in the normal location and

classified as an ectopic gallbladder.

- The second suggests that, the gallbladder may develop directly from the left

hepatic duct, and is accompanied by a failure in the development of the normal

structure on the right side.

-Third, the left umbilical vein disappears and the right one partly remains.

-The fourth explanation is that, the gallbladder is on the left side of the

ligamentum teres simply because the latter deviated to the right .

The left-sided gallbladder may occur either as a single anomaly or in a malrotation

of the intestine

Figure 4: CT injected axial slices showing ectopic gallblader with gallstone associated with situs inversus

Intrahepatic gallbladders

Have a subcapsular location along the anterior inferior right lobe of the

liver. This poses a problem for scintigraphy, as an intrahepatic

gallbladder can cause a focal defect. When a solitary defect is present in

a technetium liver scan, the differential diagnosis includes neoplasm,

abscess, hematoma, lymphoma, and an aberrant gallbladder.

Sonography can be helpful in these cases.

Suprahepatic gallbladder

The suprahepatic gallbladder is a rare type of gallbladder ectopia, with only

approximately eight cases reported. Most of these patients have either

associated hypoplasia of the right hepatic lobe or a right-sided diaphragmatic

eventration. A suprahepatic gallbladder has been reported with hepatomegaly

due to macronodular cirrhosis. Rarely, the suprahepatic gallbladder may be

intrathoracic, and be associated either with a right-sided diaphragmatic

eventration or a traumatic right-sided diaphragmatic hernia. It may be located

either anteriorly or posteriorly over the dome of the right hepatic lobe. As with

many other ectopic gallbladder locations, it usually has a mesentery that

allows it to float freely in the peritoneal cavity. The cystic duct and vascular

supply of the gallbladder in a suprahepatic location insert normally.

The retroplaced gallbladder (retrohepatic) (Figure. 5)

Is rare and can be either congenital or acquired.

Gallbladder rotation and/or displacement can be caused by hepatic lobe

abnormalities (aplasia, hypoplasia, and hypertrophy) and by abnormal

mobility of the gallbladder itself. From an imaging standpoint, it is

important to realize that when the gallbladder is not visualized in its

normal location, the possibility of an ectopic location must be considered.

Figure 5: A: ultrasonography, B: CT, C: schematic representation, showing retrohepatic location of gallbladder.

A mobile Gallbladder

May have different causes. One type of anomaly may be related to the

congenital deformity. Between the fourth and the seventh week of

embryological development, the pars cystica forms from the hepatic

diverticulum. Abnormal migration with an absence of a gallbladder

mesentery creates a “free floating gallbladder”. Another anomaly occurs

with generalized visceroptosis. The mesentery of the gallbladder and

cystic duct relax and elongate, thus creating a mobile situation.

These anomalies leading to “floating gallbladder” can be responsible for

complications such as torsion or volvolus .

Anomalies in Form

Junctional fold gallbladder

Several variations in the radiologic appearance of gallbladder shape have

been described. The so-called junctional fold is folding of the gallbladder,

usually of the posterior wall, but can occur anteriorly as well. Such

junctional folds occur frequently, and are easily shown by sonography as

well as by other imaging techniques. Careful analysis usually excludes

adjacent disease. The Phrygian cap is a typical. It takes its name from the

ancient Greek headgear, descriptive of this asymptomatic folding of the

gallbladder fundus. This variant is readily identified with sonography and

CT.

Septa of the gallbladder can be either partial or complete. These can lead to

stasis and stone formation.

Multiseptate gallbladder (Figure 6)

Is a rare anomaly, having a multichambered lumen with multiple septa,

creating a honeycombed appearance. Differential possibilities on sonography

include desquamated gallbladder mucosa, and possibly polypoid

cholesterolosis.

The coexistence of biliary symptoms with multiseptate gallbladder has been

well established, and most patients have biliary pain suggestive of cholecystitis

Gallbladders containing one to three septa are not unusual. The exact

mechanism responsible for the genesis of multiseptation is not clear. However,

it is speculated that wrinkling and infolding seen in the gallbladder buds of cat

and guinea-pig embryos or formation of the so-called Phrygian cap in human

embryos may be related to this phenomenon.

Figure 6: Ultrasonography showing some locules formed by the transversal septas.

CONCLUSION

Radiological diagnosis of biliary anomalies is an important part of

abdominal imaging. In daily practice, biliary anatomy may be demonstrated

with a wide range of techniques, such as high resolution US, multislice CT

and MRCP. Preoperative awareness of any variation minimizes the chance

of an unexpected situations during cholecystectomy, and helps avoiding

any unwanted damage to the biliary tract.

REFERENCES

1- Sonography of Gallbladder Duplication and Differential Considerations Robert C. Goiney1, Steven A. Schoenecker2, Dale A. Cyr2, William P. Shurnan2, Michael J. Peters2, Peter L. Cooperberg3. A JR 145:241-243, August 1985 0361-803X/85/1452-0241© American Roentgen Ray Society.2- Triplication of the gallbladder Ronald j. Ross, MD, and Maurice D. Sachs, M.D From the Department of Radiology, Forest City Hospital, Case-Western Reserve University School of Medicine, Cleveland, Ohio.. VoL. 104, No. 33- Agenesis of the gallbladder and cystic duct Serviço de Gastroenterologia Cirúrgica, Hospital do Servidor Público Estadual, São Paulo, Brazil. Jaques Waisberg, Paulo Engler, Pinto Júnior, Paula Regina Gusson, Paola Rossini Fasano , Antônio Cláudio de Godoy. 4- Agenesis of gallbladder and multiple anomalies of the biliary tree in a patient with portal thrombosis: A case report Yusuf BAYRAKTAR1, H. Yasemin BALABAN1, Serap ARSLAN1, Ferhun BALKANCI2 Departments of 1Gastroenterology and 2Radiology, Hacettepe University, Ankara. The Turkish Journal of Gastroenterology 2006, Volume 17, No 3, Page(s) 212-2155-Triplication of the gallbladder. Banu Alicioglu, Department of Radiology, Trakya University School of Medicine, Edirne 22030, Turkey. World J Gastroenterol. 2007 Apr 7; 13 (13) 2004-6. 6- Left-sided gallbladder associated with congenital liver cyst. R. COLOVIC1, N. COLOVIC1, G. BARISIC1, H. D. E. ATKINSON2 & Z. KRIVOKAPIC1. ISSN 1365-182X print/ISSN 1477-2574 online # 2006 Taylor & Francis DOI: 10.1080/136518204100166427- Left-sided gallbladder: Its clinical significance and imaging presentations Sheng-Lung Hsu, Tai-Yi Chen, Tung-Liang Huang, Cheuk-Kwan Sun, Allan M Concejero, Leo Leung-Chit Tsang, Yu-Fan Cheng.8- The Aberrant Gallbladder: Angiographic and Radioisotopic Considerations VINCENT P. CHUANG. Am J Roentgenol 1 27 : 41 7-421 . 1976 4179- Gastrointestinal Case of the Day Kenneth D. Hopper,1 Mary Ellen Fisher, Claudia J. Kasales, Paul S. Potok, Jon W. Meilstrup, and Daniel B. Kelley. AJR 1994;162:1448-1451 0361-803X/94/1626-1448 ©American Roentgen Ray Society. 10- Torsion of Gallbladder: Report of a case. Yon Pil Cho and al. Yonsei Med J Vol. 46, No 6, 2005. 11- Imaging of Gallbladder Variants Jon W. Meilstrup,1 Kenneth D. Hopper, and Gary A. Thieme. AJR 157:1205-1208, December 1991 0361 -803X/91/1 576-1 205 C American Roentgen Ray Society.12- Multiseptate Gallbladder with Cholelithiasis Diagnosed Incidentally in an Elderly Patient. Wataru Miwa, Kyutaro Toyama, Yoko Kitamura, Kazuko Murakami, Kazuhisa Kamata, Tessyu Takada, Hiroaki Tanabe and Masaaki Kanayama. Internal Medicine Vol. 39, No. 12 (December 2000).