Cholelithiasis vs. Cholecystitis

Definitions

	Cholelithiasis	Cholecystitis
What it is	Presence of stones (calculi) within the gallbladder	Inflammation of the gallbladder
Core concept	A structural/metabolic condition	An inflammatory/infectious process

Relationship Between the Two

More than 95% of biliary tract disease is attributable to gallstones. Cholelithiasis is the primary risk factor for cholecystitis - gallstones are found in 90-95% of patients with cholecystitis. However, they are distinct conditions: you can have gallstones for years without ever developing inflammation, and a minority of cholecystitis cases (~5-12%) occur without any stones at all (acalculous cholecystitis).

Cholelithiasis (Gallstones)

Types of Stones

1. Cholesterol stones (90% in the US/Western Europe)

Contain >50% crystalline cholesterol monohydrate
Form when bile becomes supersaturated with cholesterol relative to bile acids and phospholipids

2. Pigment stones

Black stones - form in the gallbladder; associated with chronic hemolytic anemias (sickle cell, hereditary spherocytosis), older age
Brown stones - associated with biliary infection; can form anywhere in the biliary tree

Risk Factors ("4 Fs" mnemonic)

Female sex and female sex hormones (estrogen, OCP, pregnancy)
Fat (obesity, metabolic syndrome, rapid weight loss)
Forty (increasing age)
Fertile (multiparity)
Also: Native American descent (Pima/Hopi/Navajo), Crohn's disease, cystic fibrosis with pancreatic insufficiency, TPN, drugs (clofibrate, ceftriaxone)

Clinical Features

Most patients are asymptomatic - only ~25.8% develop biliary colic at 10 years; complications occur in ~3% at 10 years
Biliary colic: dull, steady RUQ or epigastric pain (not truly "colicky"), radiating to the right scapula/shoulder; nausea/vomiting; triggered by gallbladder contraction against obstructed cystic duct
Patients appear well, no fever, no guarding/rebound
No leukocytosis, liver enzymes usually normal

Cholecystitis (Gallbladder Inflammation)

Types

1. Acute Calculous Cholecystitis (most common, ~88-95% of cases)

Triggered by a stone obstructing the gallbladder neck or cystic duct
Sequence: obstruction → increased intraluminal pressure → mucosal ischemia → phospholipases hydrolyze biliary lecithin to toxic lysolecithin → disruption of the protective mucus layer → detergent action of bile salts → prostaglandin release → inflammation
Bacterial superinfection common (E. coli most frequent; anaerobes in up to 40%)

2. Acute Acalculous Cholecystitis (5-12% of cases)

Caused by gallbladder stasis and ischemia without stones
Seen in critically ill patients: post-major surgery, severe trauma, burns, sepsis
Carries a high mortality rate due to underlying illness

3. Chronic Cholecystitis

May follow repeated acute attacks or develop silently
Almost always associated with gallstones, but supersaturation of bile (rather than stones per se) appears to drive the inflammation
E. coli and enterococci cultured in ~1/3 of cases

Clinical Features

Pain - RUQ pain that starts colicky then becomes constant (distinguishes from uncomplicated biliary colic)
Fever, nausea, vomiting
Murphy's sign - inspiratory arrest on deep palpation of RUQ
Guarding and rebound tenderness (peritoneal signs)
Leukocytosis (though absent in ~50% of cases)
Mild elevation of LFTs, alkaline phosphatase; markedly elevated lipase suggests concurrent pancreatitis

Head-to-Head Comparison

Feature	Cholelithiasis	Cholecystitis
Definition	Gallstones present	Gallbladder inflamed
Cause	Cholesterol/pigment supersaturation	Cystic duct obstruction (usually by a stone)
Symptoms	Often none; intermittent biliary colic	Persistent RUQ pain, fever, nausea/vomiting
Pain character	Dull, intermittent, self-limiting	Constant, progressive
Fever	Absent	Present
Murphy's sign	Absent	Positive
Guarding/Rebound	Absent	Present (peritoneal irritation)
WBC	Normal	Leukocytosis (often with bandemia)
LFTs	Normal	May be mildly elevated
Ultrasound	Echogenic stones with posterior shadowing	Stones + thickened GB wall (>3 mm) + pericholecystic fluid + sonographic Murphy sign
Treatment	Elective; asymptomatic = watchful waiting; symptomatic = cholecystectomy	Urgent cholecystectomy, IV antibiotics, fluids
Complications	Cholecystitis, choledocholithiasis, pancreatitis, Mirizzi syndrome	Empyema, perforation, fistula, Mirizzi syndrome

Ultrasound Findings

The image below shows what acute cholecystitis looks like on ultrasound - note the echogenic stones inside the gallbladder lumen, the thickened gallbladder wall (GBW), and pericholecystic free fluid (FF):

Ultrasound showing gallstones, thickened gallbladder wall, and pericholecystic fluid in cholecystitis

Fig. 76.22 - Gallbladder with gallstones (Stones), thickened gallbladder wall (GBW), and pericholecystic fluid (FF). Together with a sonographic Murphy sign, these findings constitute the diagnosis of cholecystitis.

When all four signs are present (stones + thickened wall + pericholecystic fluid + sonographic Murphy sign), the positive predictive value for cholecystitis exceeds 90%.

Complications Worth Knowing

Choledocholithiasis - stone migrates to common bile duct → obstructive jaundice, cholangitis (Charcot's triad), pancreatitis
Empyema - pus fills the gallbladder
Gangrenous cholecystitis - ischemic necrosis of the wall
Perforation - can lead to peritonitis or cholecystoenteric fistula
Gallstone ileus - large stone erodes into bowel, causes small bowel obstruction

Sources: Robbins & Kumar Basic Pathology; Robbins, Cotran & Kumar Pathologic Basis of Disease; Rosen's Emergency Medicine; Textbook of Family Medicine 9e

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