cholecystitis is inflammation of the gallbladder wall, most commonly caused by a gallstone (calculus) becoming lodged in the cystic duct and obstructing bile outflow. It is distinguished from cholelithiasis, which refers only to the presence of gallstones without inflammation, and from choledocholithiasis, in which a stone has migrated into the common bile duct itself rather than remaining in the gallbladder or cystic duct. The underlying mechanism is mechanical obstruction leading to bile stasis, gallbladder wall distension, chemical irritation, and secondary bacterial infection, which together produce edema, ischemia, and in severe cases necrosis of the gallbladder wall. Cholecystitis is essentially always pathological — there is no physiological form. Clinically relevant subtypes include acute cholecystitis (K81.0), chronic cholecystitis (K81.1), acute cholecystitis with chronic cholecystitis (K81.2), and cholecystitis, unspecified (K81.9), each of which may additionally be coded as calculous or acalculous depending on whether a gallstone is documented as the cause. cholecystitis is often confused with biliary colic, which is transient, self-resolving pain from a stone temporarily obstructing the cystic duct without sustained inflammation — the key distinguishing feature of cholecystitis is a sustained inflammatory process, typically with fever, leukocytosis, and imaging evidence of gallbladder wall thickening or pericholecystic fluid.
The word entered English medical usage in the 1860s as cholecystitis (noun), built directly from New Latin, which combined the Greek combining forms chole- (“bile”) and cyst- (“bladder”) with the standard inflammatory suffix -itis. The root chole- (“bile”) connects cholecystitis to the entire chole- root family: cholelithiasis (chole- “bile” + lith- “stone” + -iasis “condition of” → presence of gallstones), cholangitis (chole- “bile” + angi- “vessel” + -itis “inflammation” → inflammation of the bile ducts), and cholecystectomy (chole- “bile” + cyst- “bladder” + -ectomy “surgical removal” → surgical removal of the gallbladder). The combining form cyst- is highly productive in medical terminology and also appears in cystitis, cystoscopy, and polycystic.
🔀 ALIASES / ALTERNATE TERMS
Cholecystic(adjective form — e.g., “cholecystic pain,” “cholecystic disease”)
Gallbladder attack(lay term, especially used by patients describing an acute episode of biliary colic or early acute cholecystitis)
Acalculous cholecystitis(cholecystitis occurring without gallstones, typically in critically ill patients due to bile stasis and ischemia; still coded to the appropriate K81.0–K81.9 code, since ICD-10-CM does not require a separate calculus code when none is present)
Calculous cholecystitis(cholecystitis with a documented causative gallstone; coded instead under the combination K80 calculus-of-gallbladder codes — e.g., K80.00, K80.10, K80.12)
Emphysematous cholecystitis(severe, gas-forming acute form caused by gas-producing organisms in the gallbladder wall; still reported with K81.0)
Gangrenous cholecystitis(advanced necrotizing form of acute cholecystitis; report the additional code K82.A1 for gangrene of gallbladder when documented)
Empyema of the gallbladder(pus-filled gallbladder, a severe form of acute cholecystitis; still reported with K81.0)
🔗 RELATED TERMS
Cholelithiasis — presence of gallstones in the gallbladder without inflammation; distinguished from cholecystitis by the absence of a sustained inflammatory response.
Choledocholithiasis — shares the chole- root; refers to a gallstone lodged in the common bile duct rather than the gallbladder itself.
Cholangitis — inflammation of the bile ducts, often due to obstruction and infection; commonly coexists with or follows untreated choledocholithiasis, and may present with the Charcot triad of fever, jaundice, and right-upper-quadrant pain.
Biliary colic — transient right-upper-quadrant pain from a temporarily obstructing gallstone; distinguished from cholecystitis by the lack of sustained inflammation, fever, or leukocytosis.
Biliary dyskinesia — a functional gallbladder motility disorder producing biliary-type pain in the absence of stones or inflammation; diagnosed via HIDA scan with ejection fraction testing rather than by direct visualization of inflammation.
Gangrene of gallbladder — necrosis of the gallbladder wall representing a complication of severe acute cholecystitis; coded as an additional diagnosis with K82.A1.
Perforation of gallbladder — a further complication of severe or gangrenous cholecystitis in which the necrotic wall ruptures; coded as an additional diagnosis with K82.A2.
Murphy’s sign — the key bedside diagnostic maneuver for acute cholecystitis, in which palpation of the right upper quadrant during inspiration causes pain and inspiratory arrest.
Hepatobiliary iminodiacetic acid (HIDA) scan — the primary confirmatory diagnostic imaging study for acute cholecystitis when ultrasound findings are equivocal, demonstrating non-visualization of the gallbladder due to cystic duct obstruction.
CODING CORNER
🏥 ICD-10-CM CODES
Cholecystitis Without Mention of Calculus (K81 — Site/Type Specificity Required)
Hepatobiliary (HIDA) scan with pharmacologic intervention (e.g., CCK stimulation); adds gallbladder ejection fraction assessment for suspected biliary dyskinesia.
⚠️ Coding Note: For inpatient profee coding, always confirm whether a gallstone is documented as the cause of the cholecystitis — if so, sequence to the more specific K80 combination code (which captures calculus, cholecystitis type, and obstruction status in one code) rather than defaulting to a standalone K81 code, since the K81 series is reserved for acalculous or stone-status-unspecified presentations. When both acute and chronic cholecystitis are documented on the same encounter, code K81.2 (or the corresponding K80.1x/K80.6x combination) rather than reporting acute and chronic separately. A frequent undercoding alert: documentation of “gangrenous,” “necrotizing,” or “perforated” gallbladder should always trigger a query for the additional K82.A1/K82.A2 codes, as these substantially affect MS-DRG severity and are often left uncaptured when coders stop at the base cholecystitis code. Confirm obstruction status (“with obstruction” vs. “without obstruction”) is explicitly documented before assigning the corresponding K80 fourth/fifth character, since this is a frequent physician query trigger. For payer prior-authorization purposes on cholecystectomy, imaging confirmation (ultrasound and/or HIDA scan) supporting the cholecystitis diagnosis should be present in the chart to support medical necessity.