Congenital Abnormalities of the Gallbladder

Published on 19/07/2015 by admin

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 Agenesis of GB: Congenital absence of GB

image Hypogenesis of GB: Rudimentary or atretic GB
image Bilobed GB: 2 completely divided GB cavities with a common cystic duct
image Duplicated GB: Duplicated GB with separate cystic ducts for each moiety
image Multiseptate GB: Single GB with “honeycomb” appearance due to innumerable internal septations
image Hourglass GB: Hourglass shape of GB may be congenital or acquired due to chronic inflammation
image Congenital diverticulum: Usually true diverticulum that can be seen anywhere in GB
image Phrygian cap: Folding of GB fundus (considered normal variant given its high prevalence)
image Ectopic GB: Ectopically positioned GB has been reported in nearly every possible position in abdomen and pelvis

– Most common ectopic positions are intrahepatic, under left hepatic lobe, transverse, and retrohepatic
– Surgical removal of intrahepatic GB may be challenging
image Floating or wandering GB: Mobile GB due to long mesentery, completely covered by peritoneum

– High risk of GB torsion and gangrenous inflammation

TOP DIFFERENTIAL DIAGNOSES

• Prior cholecystectomy
• Chronic cholecystitis
• Hartmann pouch of GB
• Hyperplastic cholecystoses
• Abdominal fluid collection

CLINICAL ISSUES

• Virtually always incidental finding of no clinical significance
• Floating or wandering GB has higher likelihood of torsion due to increased risk of GB “twisting” on long pedicle
image
(Left) Ultrasound demonstrates the characteristic appearance of a phrygian cap, with a fold image near the gallbladder (GB) fundus. This is considered a normal variant given its high prevalence.

image
(Right) Axial T2WI FSE MR in a woman with chronic abdominal pain shows an incidental phrygian cap image.
image
(Left) Ultrasound demonstrates many septations within the GB, creating a “honeycomb” appearance, characteristic of a multiseptate GB.

image
(Right) Coronal Tc-99m HIDA scan of a 54-year-old woman with abdominal pain shows progressive filling of the bile duct image and proximal small bowel image, but no GB activity. The patient had no operative history and multiple imaging studies confirmed GB agenesis.

TERMINOLOGY

Synonyms

• Gallbladder malformation

Definitions

• Spectrum of congenital malformations of gallbladder (GB) shape, morphology, number, or position

image Agenesis of GB: Congenital absence of GB
image Hypogenesis of GB: Rudimentary or atretic GB

– Differentiate from acquired microgallbladder in cystic fibrosis due to viscous bile or chronic cholecystitis
image Bilobed GB: 2 completely divided GB cavities with a single common cystic duct

– Differentiate from cholecystomegaly (abnormally large GB) in sickle cell disease, pregnancy, or obesity
image Duplicated GB: Duplicated GBs with separate cystic ducts for each moiety

– Cystic ducts may separately insert into extrahepatic bile duct (H-type) or have common insertion (Y-type)
– Each gallbladder has a separate cystic artery
image Triplicate GB (vesica fellea triplex): 3 separated GB
image Multiseptate GB: Single GB with “honeycomb” appearance due to innumerable internal septations, likely due to incomplete vacuolization of developing GB bud
image Hourglass GB: Hourglass shape of GB may be due to abnormal vacuolization

– In adults, may be acquired abnormality (due to chronic inflammation and scarring)
image Congenital diverticulum: Usually a true diverticulum (containing all layers of GB wall) that can be located anywhere in GB

– Differentiate from acquired diverticula due to prior cholecystitis or traction from prior surgery or duodenitis
image Phrygian cap: Folding of GB fundus that is considered normal variant given its high prevalence

– Most common variant of GB shape
image Ectopic GB: Ectopically positioned GB has been reported in nearly every possible position in abdomen and pelvis

– Most common positions are intrahepatic, under left hepatic lobe, transverse, retrohepatic, and retroperitoneal
image Left-sided GB: Ectopic GB positioned in left side of abdomen

– Isolated or associated with situs inversus
– Cystic duct usually inserts into left hepatic duct
– May be associated with left portal vein anomalies
image Intrahepatic GB: Subcapsular GB partially or completely embedded in liver
image Horizontal GB: Ectopic GB within porta hepatis; usually deeply embedded in liver
image Retrodisplaced GB: Retrohepatic or retroperitoneal ectopic GB
image Floating or wandering GB: Mobile GB due to long mesentery, completely covered by peritoneum

– May be positioned throughout abdomen
– High risk of GB torsion and may cause pain by herniating through foramen of Winslow into lesser sac

IMAGING

General Features

• Best diagnostic clue

image Abnormal shape, morphology, number, or position of GB

CT Findings

• GB agenesis: Absence of GB in patient with no history of prior cholecystectomy; should exclude prior history of cholecystectomy or ectopic position of GB before arriving at this diagnosis
• Bilobed GB: External contour of GB may be normal and division between duplicated GB cavities may be imperceptible

image 2 distinct cavities easier to visualize if differential density of bile in each cavity
image Prominent GB fold or phrygian cap may be a mimic
• Duplicated GB: External contour of GB may or may not be normal; separate cystic ducts and cystic arteries leading to 2 separate GBs in close contiguity

image Cystic ducts may be completely separate with distant insertion to extrahepatic bile duct (H-type) or have common insertion point to bile duct (Y-type)
image Easiest to distinguish 2 GBs if there is sludge, cholelithiasis, or vicariously excreted contrast in 1 GB but not the other
• Multiseptate GB: Innumerable septations within single GB with normal external contour resulting in “honeycomb” appearance
• Phrygian cap: Prominent folding of GB fundus on GB body

MR Findings

• MRCP helpful for demonstrating anatomy of cystic ducts to differentiate bilobed GB from duplicated GB

image May also provide better soft tissue resolution to identify internal septations or compartments
• Delayed gadoxetate (Eovist) enhanced images may show communication between lumina and can delineate cystic duct anatomy

Ultrasonographic Findings

• Grayscale ultrasound

image First-line modality for evaluation of GB pathologies and anomalies
image Abnormal number, shape, or position of GB

Nuclear Medicine Findings

• Hepatobiliary scintigraphy

image Abnormal form, number, or position of GB
image Absent GB activity may prompt erroneous diagnosis of cystic duct obstruction and acute cholecystitis
image Intrahepatic GB appears as focal photopenic defect on early phase

Imaging Recommendations

• Best imaging tool

image Ultrasound as screening tool (usually incidental imaging finding on US performed for other reasons)
image MR for confirmation and better definition of abnormalities
• Protocol advice

DIFFERENTIAL DIAGNOSIS

Prior Cholecystectomy

• Most common cause of absent GB

Chronic Cholecystitis

• Much more common than congenital anomalies
• Scarring due to chronic cholecystitis can result in shrinkage of GB (mimicking GB hypogenesis) or hourglass-shaped/multiseptate GB
• Usually associated with cholelithiasis

Hartmann Pouch of GB

• Acquired diverticulum along inferior aspect of GB neck/infundibulum
• Associated with chronic obstruction and cholelithiasis
• GB diverticula can also be acquired due to traction from prior surgery or adjacent duodenal inflammation

Hyperplastic Cholecystoses

• Prominent Rokitansky-Aschoff sinuses in GB adenomyomatosis can mimic diverticulum
• Focal mass-like adenomyomatosis at fundus can mimic bilobed GB, duplicated GB, or phrygian cap
• Configuration and presence of wall thickening (and “comet tail” artifact) are helpful to distinguish 2 entities

Abdominal Fluid Collection

• Intraabdominal fluid collections can mimic ectopic GB
• Ectopic GB is continuous with biliary tree (best evaluated on CT, MRCP, and cholangiography)
• Patient’s history and history of prior cholecystectomy are helpful

PATHOLOGY

General Features

• Etiology

image Abnormal development resulting in absence, abnormal formation, or deformity of GB
image Genetic and environmental factors play a role
• Associated abnormalities

image Agenesis of GB has high association with biliary atresia and other congenital malformations
• Normal embryology

image GB arises from hepatic diverticulum (ventral bud) of caudal primitive foregut during week 4 of intrauterine life

– Hepatic diverticulum further divides into pars hepatica (developing into liver and intrahepatic ducts) and pars cystica (developing into GB and extrahepatic bile ducts)
image GB starts as solid cord that vacuolizes by 8th week of intrauterine life
• Pathogeneses

image Abnormal formation (agenesis, hypogenesis, duplication, triplication)
image Abnormal vacuolization (bilobed GB, hourglass/multiseptate GB, congenital stricture or atresia of cystic duct)
image Abnormal migration of ventral bud (GB ectopia)
image Deformity (folds, phrygian cap, hourglass GB)
image Heterotopia and choristoma (ectopic tissue of endodermal origin such as hepatic, gastric, adrenal, thyroid, or pancreatic tissue in GB wall)

Staging, Grading, & Classification

• Abnormal formation

image Hypogenesis (rudimentary GB)
image Phrygian cap
image Hourglass/multiseptate GB
image Bilobed GB
image Gallbladder diverticulum
• Abnormal number

image Agenesis
image Duplicated GB
image Triplicate GB
• Ectopia (abnormal position)

image Intrahepatic GB
image “Floating” GB
image Left-sided GB
image Transverse GB
image Retrodisplaced GB

Gross Pathologic & Surgical Features

• Wide spectrum of abnormal form, position, and number of GB
• Duplicated GB has associated duplication of cystic arteries

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Asymptomatic: Virtually always an incidental finding
• Other signs/symptoms

image RUQ pain due to biliary colic and inflammation
image Inflammation of 1 moiety in a duplicated or bilobed GB in cholecystitis may cause clinical confusion

Demographics

• Epidemiology

image Phrygian cap is normal variant seen in up to 6% of normal population
image Other congenital anomalies are rare

– Agenesis of GB prevalence: 0.04-0.13% in autopsy series
– Duplicated GB prevalence: 1-5 per 10,000
image Given their rarity, exact prevalence and gender distribution are not well studied

Natural History & Prognosis

• Virtually always of no clinical significance
• Very rarely may predispose to biliary stasis, inflammation, and stone formation
• “Floating” or “wandering” GB has higher likelihood of torsion due to ↑ risk of GB “twisting” on long vascular pedicle

image Usually diagnosed as acute cholecystitis on imaging
image ↑ risk of gangrene compared to traditional cholecystitis

Treatment

• No treatment or follow-up in asymptomatic patients
• Cholecystectomy if symptomatic due to cholelithiasis, cholecystitis, or torsion

image Surgical removal of intrahepatic GB may be challenging

DIAGNOSTIC CHECKLIST

Consider

• Ectopic location or agenesis if GB is not visualized

Reporting Tips

• Congenital anomalies may impact surgical planning for cholecystectomy
image
(Left) Ultrasound demonstrates 2 cystic structures in the GB fossa, one of which contains anechoic bile image and the other containing sludge image.

image
(Right) Axial T2 FS MR in the same patient demonstrates the 2 cystic structures seen on US, one showing high T2 signal image, and the other showing intermediate to high T2 signal image. Two separate cystic ducts were seen on MRCP (not shown), allowing the diagnosis of a duplicated GB (rather than a bilobed GB).
image
(Left) Ultrasound of an elderly debilitated man with right upper quadrant pain shows dependent sludge image within both lobes of a bilobed GB.

image
(Right) CECT of the same patient shows 2 separate GBs image. Both lobes of a bilobed GB share a common cystic duct. Persistent abdominal pain and leukocytosis prompted cholecystostomy drainage of the more superficial GB. Both lumina were successfully decompressed.
image
(Left) Transverse ultrasound of a neonate shows a completely intrahepatic GB image. As an isolated finding this is not clinically significant, although the location of the GB may make cholecystectomy exceedingly difficult.

image
(Right) Coronal MRCP shows a cystic structure image adjacent to the GB. The configuration of the “cyst” is characteristic of GB duplication. Both the GB and the “cyst” are partially opacified via separate cystic ducts on a follow-up Eovist enhanced MRCP.

SELECTED REFERENCES

1. Revzin, MV, et al. The gallbladder: uncommon gallbladder conditions and unusual presentations of the common gallbladder pathological processes. Abdom Imaging. 2014. [Epub ahead of print].

 

Khadim, MT, et al. Triple gallbladder: a rare entity. Am J Gastroenterol. 2011; 106(10):1861–1862.

Walbolt, TD, et al. Laparoscopic management of a duplicated gallbladder: a case study and anatomic history. Surg Laparosc Endosc Percutan Tech. 2011; 21(3):e156–e158.

Causey, MW, et al. Gallbladder duplication: evaluation, treatment, and classification. J Pediatr Surg. 2010; 45(2):443–446.

Rivera-Troche, EY, et al. Multiseptate gallbladder. J Gastrointest Surg. 2009; 13(9):1741–1743.

Faure, JP, et al. Abnormalities of the gallbladder, clinical effects. Surg Radiol Anat. 2008; 30(4):285–290.

Hsu, SL, et al. Left-sided gallbladder: its clinical significance and imaging presentations. World J Gastroenterol. 2007; 13(47):6404–6409.

Kabiri, H, et al. Agenesis of the gallbladder. Curr Surg. 2006; 63(2):104–106.

Bani-Hani, KE. Agenesis of the gallbladder: difficulties in management. J Gastroenterol Hepatol. 2005; 20(5):671–675.

Grand, D, et al. CT of the gallbladder: spectrum of disease. AJR Am J Roentgenol. 2004 Jul; 183(1):163–170. [Erratum in: AJR Am J Roentgenol. 183(20:543, 2004].

Nakazawa, T, et al. Multiseptate gallbladder: diagnostic value of MR cholangiography and ultrasonography. Abdom Imaging. 2004; 29(6):691–693.

Ozgen, A, et al. Gallbladder duplication: imaging findings and differential considerations. Abdom Imaging. 1999; 24(3):285–288.

Richards, RJ, et al. Agenesis of the gallbladder in symptomatic adults. A case and review of the literature. J Clin Gastroenterol. 1993; 16(3):231–233.

Meilstrup, JW, et al. Imaging of gallbladder variants. AJR Am J Roentgenol. 1991; 157(6):1205–1208.

Gross, RE. Congenital abnormalities of the gallbladder: a review of 148 cases with report of double gallbladder. Arch Surg. 1936; 32(1):131–162.

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