Invertebrates, thegallbladder, also known as thecholecyst, is a small holloworgan wherebile is stored and concentrated before it is released into thesmall intestine. In humans, the pear-shaped gallbladder lies beneath theliver, although the structure and position of the gallbladder can vary significantly among animal species. It receives bile, produced by the liver, via thecommon hepatic duct, and stores it. The bile is then released via thecommon bile duct into theduodenum, where the bile helps in the digestion offats.
The gallbladder can be affected bygallstones, formed by material that cannot be dissolved – usuallycholesterol orbilirubin, a product ofhemoglobin breakdown. These may cause significant pain, particularly in the upper-right corner of the abdomen, and are often treated with removal of the gallbladder (called acholecystectomy).Cholecystitis, inflammation of the gallbladder, has a wide range of causes, including result from the impaction of gallstones, infection, and autoimmune disease.
The human gallbladder is a hollow grey-blueorgan that sits in a shallow depression below the right lobe of theliver.[2] In adults, the gallbladder measures approximately 7 to 10 centimetres (2.8 to 3.9 inches) in length and 4 centimetres (1.6 in) in diameter when fully distended.[3] The gallbladder has a capacity of about 50 millilitres (1.8 imperial fluid ounces).[2]
The gallbladder is shaped like a pear, with its tip opening into thecystic duct.[4] The gallbladder is divided into three sections: thefundus,body, andneck. Thefundus is the rounded base, angled so that it faces theabdominal wall. Thebody lies in a depression in the surface of the lower liver. Theneck tapers and is continuous with thecystic duct, part of thebiliary tree.[2] The gallbladder fossa, against which the fundus and body of the gallbladder lie, is found beneath the junction ofhepatic segments IVB and V.[5] The cystic duct unites with thecommon hepatic duct to become thecommon bile duct. At the junction of the neck of the gallbladder and the cystic duct, there is an out-pouching of the gallbladder wall forming a mucosal fold known as "Hartmann's pouch".[2]
Lymphatic drainage of the gallbladder follows the cystic node, which is located between the cystic duct and the common hepatic duct. Lymphatics from the lower part of the organ drain into lowerhepatic lymph nodes. All the lymph finally drains intoceliac lymph nodes.
The gallbladder wall is composed of a number of layers. The innermost surface of the gallbladder wall is lined by a single layer ofcolumnar cells with abrush border ofmicrovilli, very similar to intestinal absorptive cells.[2] Underneath the epithelium is an underlyinglamina propria, amuscular layer, an outer perimuscular layer andserosa. Unlike elsewhere in the intestinal tract, the gallbladder does not have amuscularis mucosae, and the muscular fibres are not arranged in distinct layers.[6]
Themucosa, the inner portion of the gallbladder wall, consists of alining of asingle layer of columnar cells, with cells possessing small hair-like attachments calledmicrovilli.[2] This sits on a thin layer of connective tissue, thelamina propria.[6] The mucosa is curved and collected into tiny outpouchings calledrugae.[2]
A muscular layer sits beneath the mucosa. This is formed bysmooth muscle, with fibres that lie in longitudinal, oblique and transverse directions, and are not arranged in separate layers. The muscle fibres here contract to expel bile from the gallbladder.[6] A distinctive feature of the gallbladder is the presence ofRokitansky–Aschoff sinuses, deep outpouchings of the mucosa that can extend through the muscular layer, and which indicateadenomyomatosis.[7] The muscular layer is surrounded by a layer of connective andfat tissue.[2]
The outer layer of the fundus of gallbladder, and the surfaces not in contact with the liver, are covered by a thickserosa, which is exposed to theperitoneum.[2] The serosa contains blood vessels and lymphatics.[6] The surfaces in contact with the liver are covered inconnective tissue.[2]
The gallbladder varies in size, shape, and position among different people.[2] Rarely, two or even three gallbladders may coexist, either as separate bladders draining into the cystic duct, or sharing a common branch that drains into the cystic duct. Additionally, the gallbladder may fail to form at all. Gallbladders with two lobes separated by aseptum may also exist. These abnormalities are not likely to affect function and are generally asymptomatic.[8]
The location of the gallbladder in relation to the liver may also vary, with documented variants including gallbladders found within,[9] above, on the left side of, behind, and detached or suspended from the liver. Such variants are very rare: from 1886 to 1998, only 110 cases of left-lying liver, or less than one per year, were reported in scientific literature.[10][11][2]
The gallbladder develops from anendodermal outpouching of the embryonic gut tube.[13] Early in development, the human embryo has threegerm layers and abuts an embryonicyolk sac. During the second week ofembryogenesis, as the embryo grows, it begins to surround and envelop portions of this sac. The enveloped portions form the basis for the adult gastrointestinal tract. Sections of thisforegut begin to differentiate into the organs of the gastrointestinal tract, such as theesophagus,stomach, andintestines.[13]
During the fourth week of embryological development, the stomach rotates. The stomach, originally lying in the midline of the embryo, rotates so that its body is on the left. This rotation also affects the part of the gastrointestinal tube immediately below the stomach, which will go on to become theduodenum. By the end of the fourth week, the developing duodenum begins to spout a small outpouching on its right side, thehepatic diverticulum, which will go on to become thebiliary tree. Just below this is a second outpouching, known as thecystic diverticulum, that will eventually develop into the gallbladder.[13]
The main functions of the gallbladder are to store and concentratebile, also called gall, needed for the digestion of fats in food. Produced by the liver, bile flows through small vessels into the largerhepatic ducts and ultimately through thecystic duct (parts of thebiliary tree) into the gallbladder, where it is stored. At any one time, 30 to 60 millilitres (1.0 to 2.0 US fl oz) of bile is stored within the gallbladder.[15]
When food containing fat enters thedigestive tract, it stimulates thesecretion ofcholecystokinin (CCK) fromI cells of the duodenum and jejunum. In response to cholecystokinin, the gallbladder rhythmically contracts and releases its contents into thecommon bile duct, eventually draining into theduodenum. The bileemulsifies fats in partly digested food, thereby assisting their absorption. Bile consists primarily of water andbile salts, and also acts as a means of eliminatingbilirubin, a product ofhemoglobin metabolism, from the body.[15]
The bile that is secreted by the liver and stored in the gallbladder is not the same as the bile that is secreted by the gallbladder. During gallbladder storage of bile, it is concentrated 3–10 fold[16] by removal of some water and electrolytes. This is through theactive transport of sodium and chloride ions[17] across the epithelium of the gallbladder, which creates anosmotic pressure that also causes water and other electrolytes to be reabsorbed.[15]
A function of the gallbladder appears to be protection againstcarcinogenesis as indicated by observations that removal of the gallbladder (cholecystectomy) increases subsequent cancer risk. For instance, a systematic review and meta analysis of eighteen studies concluded that cholecystectomy has a harmful effect on the risk of right-sided colon cancer.[18] Another recent study reported a significantly increased total cancer risk, including increased risk of several different types of cancer, after cholecystectomy.[19]
Gallstones form when the bile issaturated, usually with eithercholesterol orbilirubin.[20] Most gallstones do not cause symptoms, with stones either remaining in the gallbladder or passed along thebiliary system.[21] When symptoms occur, severe "colicky" pain in the upper rightquadrant of the abdomen is often felt.[20] If thestone blocks the gallbladder, inflammation known ascholecystitis may result. If the stone lodges in the biliary system,jaundice may occur; if the stone blocks thepancreatic duct,pancreatitis may occur.[21] Gallstones are diagnosed usingultrasound.[20] When a symptomatic gallstone occurs, it is often managed by waiting for it to be passed naturally.[21] Given the likelihood of recurrent gallstones, surgery to remove the gallbladder is often considered.[21] Some medication, such asursodeoxycholic acid, may be used;lithotripsy, a non-invasive mechanical procedure used to break down the stones, may also be used.[21]
Known ascholecystitis, inflammation of the gallbladder is commonly caused by obstruction of the duct with gallstones, which is known ascholelithiasis. Blocked bile accumulates, and pressure on the gallbladder wall may lead to the release of substances that cause inflammation, such asphospholipase. There is also the risk of bacterial infection. An inflamed gallbladder is likely to cause sharp and localised pain, fever, and tenderness in the upper, right corner of the abdomen, and may have a positiveMurphy's sign. Cholecystitis is often managed with rest and antibiotics, particularlycephalosporins and, in severe cases,metronidazole. Additionally the gallbladder may need to be removed surgically if inflammation has progressed far enough.[21]
Acholecystectomy is a procedure in which the gallbladder is removed. It may be removed because of recurrent gallstones and is considered anelective procedure. A cholecystectomy may be anopen procedure, or alaparoscopic one. In the surgery, the gallbladder is removed from the neck to the fundus,[22] and so bile will drain directly from the liver into thebiliary tree. About 30 percent of patients may experience some degree ofindigestion following the procedure, although severe complications are much rarer.[21] About 10 percent of surgeries lead to a chronic condition ofpostcholecystectomy syndrome.[23]
Biliary injury (bile duct injury) is the traumatic damage of thebile ducts. It is most commonly aniatrogenic complication ofcholecystectomy — surgical removal ofgall bladder, but can also be caused by other operations or bymajor trauma. The risk of biliary injury is more during laparoscopic cholecystectomy than during open cholecystectomy. Biliary injury may lead to several complications and may even cause death if not diagnosed in time and managed properly. Ideally biliary injury should be managed at a center with facilities and expertise inendoscopy,radiology and surgery.[24]
Cancer of the gallbladder is uncommon and mostly occurs in later life. When cancer occurs, it is mostly of the glands lining the surface of the gallbladder (adenocarcinoma).[21] Gallstones are thought to be linked to the formation of cancer. Other risk factors include large (>1 cm)gallbladder polyps and having a highly calcified"porcelain" gallbladder.[21]
Cancer of the gallbladder can cause attacks of biliary pain, yellowing of the skin (jaundice), and weight loss. A large gallbladder may be able to be felt in the abdomen.Liver function tests may be elevated, particularly involvingGGT andALP, with ultrasound and CT scans being consideredmedical imaging investigations of choice.[21] Cancer of the gallbladder is managed by removing the gallbladder, however, as of 2010,[update] the prognosis remains poor.[21]
Cancer of the gallbladder may also be found incidentally after surgical removal of the gallbladder, with 1–3% of cancers identified in this way.Gallbladder polyps are mostly benign growths or lesions resembling growths that form in the gallbladder wall,[26] and are only associated with cancer when they are larger in size (>1 cm).[21] Cholesterol polyps, often associated withcholesterolosis ("strawberry gallbladder", a change in the gallbladder wall due to excesscholesterol[27]), often cause no symptoms and are thus often detected in this way.[21]
Tests used to investigate for gallbladder disease includeblood tests andmedical imaging. Afull blood count may reveal an increased white cell count suggestive of inflammation or infection. Tests such asbilirubin andliver function tests may reveal if there is inflammation linked to the biliary tree or gallbladder, and whether this is associated with inflammation of the liver, and alipase oramylase may be elevated if there ispancreatitis. Bilirubin may rise when there is obstruction of the flow of bile. ACA 19-9 level may be taken to investigate for cholangiocarcinoma.[21]
Mostvertebrates have gallbladders, but the form and arrangement of the bile ducts may vary considerably. In many species, for example, there are several separate ducts running to the intestine, rather than the single common bile duct found in humans. Several species ofmammals (includinghorses,deer,rodents, andlaminoids),[29][30] several species ofbirds (such as pigeons and somepsittacine species),lampreys and allinvertebrates do not have a gallbladder.[31][32]
Depictions of the gallbladder and biliary tree are found inBabylonian models found from 2000 BCE, and in ancientEtruscan model from 200 BCE, with models associated with divine worship.[35]
Diseases of the gallbladder are known to have existed in humans since antiquity, with gallstones found in the mummy of Princess Amenen ofThebes dating to 1500 BCE.[35][36] Some historians believe the death ofAlexander the Great may have been associated with an acute episode of cholecystitis.[35] The existence of the gallbladder has been noted since the 5th century, but it is only relatively recently that the function and the diseases of the gallbladder has been documented,[36] particularly in the last two centuries.[35]
The first descriptions of gallstones appear to have been in theRenaissance, perhaps because of the low incidence of gallstones in earlier times owing to a diet with more cereals and vegetables and less meat.[37] Anthonius Benevinius in 1506 was the first to draw a connection between symptoms and the presence of gallstones.[37]Ludwig Georg Courvoisier, after examining a number of cases in 1890 that gave rise to theeponymousCourvoisier's law, stated that in an enlarged, nontender gallbladder, the cause ofjaundice is unlikely to be gallstones.[35]
The first surgical removal of a gallstone (cholecystolithotomy) was in 1676 by physician Joenisius, who removed the stones from a spontaneously occurringbiliary fistula.[35] Stough Hobbs in 1867 performed the first recordedcholecystotomy,[37] although such an operation was in fact described earlier by French surgeonJean Louis Petit in the mid eighteenth century.[35] German surgeonCarl Langenbuch performed the first cholecystectomy in 1882 for a sufferer of cholelithiasis.[36] Before this, surgery had focused on creating afistula for drainage of gallstones.[35] Langenbuch reasoned that given several other species of mammal have no gallbladder, humans could survive without one.[35]
The debate whether surgical removal of the gallbladder or simply gallstones was preferred was settled in the 1920s, with the consensus that removal of the gallbladder was preferred.[36] It was only in the mid and late parts of the twentieth century that medical imaging techniques such as use ofcontrast medium andCT scans were used to view the gallbladder.[35] The firstlaparoscopic cholecystectomy performed byErich Mühe of Germany in 1985, although French surgeons Phillipe Mouret and Francois Dubois are often credited for their operations in 1987 and 1988 respectively.[38]
To have "gall" is associated with bold, belligerent behaviour, whereas to have "bile" is associated with sourness.[39]
In theChinese medicine, the gallbladder (膽) is associated with theWuxing element of wood, in excess its emotion is belligerence and in deficiency cowardice and judgement, in the Chinese language it is related to a myriad ofidioms, including using terms such as "a body completely [of] gall" (渾身是膽) to describe a forward person, and "single, alone gallbladder hero" (孤膽英雄) to describe a lone hero, or "they have a lot of gall to talk like that".[40]
In theZangfu theory ofChinese medicine it is an extraordinary Fu oryang organ, as it holds bile. The gallbladder not only has a digestive role, but is seen as the seat of decision-making and judgement.[40]
^Leeuw, Th.G.; Verbeek, P.C.M.; Rauws, E.A.J.; Gouma, D.J. (September 1995). "A double or bilobar gallbladder as a cause of severe complications after (laparoscopic) cholecystectomy".Surgical Endoscopy.9 (9):998–1000.doi:10.1007/BF00188459.PMID7482221.S2CID2581053.
^abcSchoenwolf, Gary C.; et al. (2009). "Development of the Gastrointestinal Tract".Larsen's human embryology (4th ed.). Philadelphia: Churchill Livingstone/Elsevier.ISBN978-0-443-06811-9.
^Standring S, Borley NR, eds. (2008).Gray's anatomy : the anatomical basis of clinical practice. Brown JL, Moore LA (40th ed.). London: Churchill Livingstone. pp. 1163, 1177,1185–6.ISBN978-0-8089-2371-8.
^abcGuyton, Arthur C.; Hall, John E. (2005).Textbook of medical physiology (11th ed.). Philadelphia: W.B. Saunders. pp. 802–4.ISBN978-0-7216-0240-0.
^Meyer, G.; Guizzardi, F.; Rodighiero, S.; Manfredi, R.; Saino, S.; Sironi, C.; Garavaglia, M. L.; Bazzini, C.; Bottà, G. (June 2005). "Ion transport across the gallbladder epithelium".Current Drug Targets. Immune, Endocrine and Metabolic Disorders.5 (2):143–151.doi:10.2174/1568008054064805.PMID16089346.
^abcdefghijklmnopqNicki R. Colledge; Brian R. Walker; Stuart H. Ralston, eds. (2010).Davidson's principles and practice of medicine (21st ed.). Edinburgh: Churchill Livingstone/Elsevier. pp. 977–984.ISBN978-0-7020-3085-7.
^Lifang, Qu (2020).Chinese Medicine Psychology: A Clinical Guide to Mental and Emotional Wellness. Jessica Kingsley Publishers.ISBN978-1-78775-276-4.
^abYu, Ning (January 1, 2003). "Metaphor, Body, and Culture: The Chinese Understanding of Gallbladder and Courage".Metaphor and Symbol.18 (1):13–31.doi:10.1207/S15327868MS1801_2.S2CID143595915.
Books
Standring S, Borley NR, eds. (2008).Gray's Anatomy : The Anatomical Basis of Clinical Practice. Brown JL, Moore LA (40th ed.). London: Churchill Livingstone.ISBN978-0-8089-2371-8.
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