MORPHOLOGYCholesterol stones ariseexclusivelyinthegallbladderandconsistof50%to100%cholesterol.Purecholesterolstonesarepaleyellow;increasingproportionsofcalciumcarbonate,phos phates,andbilirubinimpartgray-whitetoblackdiscoloration(Fig.
16.39 ).Theyareovoidandfirm;theycanoccursingly,butmostoftenthereareseveral,withfacetedsurfacesresultingfromtheirapposition.Mostcholesterolstonesareradiolucent,althoughasmanyas20%maycontainsufficientcalciumcarbonatetoberadiopaque.
Pigment stones mayariseanywhereinthebiliarytreeandareclassifiedintoblackandbrownstones.Ingeneral,blackpigmentstonesarefoundinsterilegallbladderbile,whilebrownstonesarefoundininfectedintrahepaticorextrahepaticducts.
Fig. 16.39 Cholesterolgallstones.Thewallofthegallbladderisthickenedandfibroticduetochroniccholecystitis.
Thestonescontaincalciumsaltsofunconjugatedbilirubinandlesseramountsofothercalciumsalts,mucinglycoproteins,andcholesterol.Blackstonesareusuallysmall,numerous,andfragiletothetouch(
Fig.16.40 ).Brownstonestendtobesingleorfewinnumberandtohaveasoft,greasy,soaplikeconsistencyowingtothepresenceoffattyacidsaltsreleasedfrombiliarylecithinsbybacterialphospholipases.Becauseofcalciumcarbonatesandphosphates,50%to75%ofblackstonesareradiopaque.Brownstones,whichcontaincalciumsoaps,areradiolucent.
Gallstones may be present for decades without causing any symptoms, and 70% to 80% of individuals with gallstones remain asymptomatic throughout life. In an unfortunate minority, however, the symptoms are striking. There is usually right upper-quadrant or epigastric pain, often excruciating, which may be constant or, less commonly, spasmodic. Such “biliary” pain is caused by gallbladder or biliary tree obstruction or by inflammation of the gallbladder itself. More severe complications include empyema, perforation, fistulas, inflammation of the biliary tree, obstructive cholestasis and pancreatitis. The larger the stone, the less likely it is to enter the cystic or common ducts to produce obstruction; thus, the very small stones, or “gravel,” are dangerous. Occasionally a large stone may erode directly into an adjacent loop of small bowel, generating intestinal obstruction
Fig. 16.40 Pigmentgallstones.Severalfacetedblackgallstonesarepresentinthisotherwiseunremarkablegallbladderfromapatientwithamechanicalmitralvalveprosthesis,leadingtochronicintravascularhemolysis.
http://ebooksmedicine.net (gallstone ileus).
Inflammation of the gallbladder may be acute, chronic, or acute superimposed on chronic, and almost always occurs in association with gallstones. In the United States, cholecystitis is one of the most common indications for abdominal surgery. Its epidemiologic distribution closely parallels that of gallstones.
Acute inflammation of a gallbladder that contains stones is termed acute calculous cholecystitis and is precipitated in 90% of cases by obstruction of the gallbladder neck or cystic duct. It is the most common major complication of gallstones and the most frequent indication for emergency cholecystectomy. Manifestations of obstruction may appear with remarkable suddenness and constitute a surgical emergency. In some cases, however, symptoms may be mild and resolve without intervention.