Cholelithiasis is one of those “you will see it” GI topics on Step—often disguised as a classic vignette about postprandial RUQ pain, risk factors, and a question asking what type of stone it is (or what to do next). Here’s a quick-hit, shareable mnemonic plus the high-yield facts that actually show up on USMLE.
The Mnemonic: “7 F’s + RUQ” (Gallstones Risk Snapshot)
Cholelithiasis risk factors — remember the classic:
Fat, Female, Forty, Fertile, Fair, Family history, Fibrosis (CF) + RUQ pain
One-liner explanation
Estrogen + cholesterol supersaturation + gallbladder stasis → stones (especially cholesterol stones).
If you can recall “7 F’s,” you can usually predict the patient profile in the vignette.
Visual Memory Hook: “F’s in the Gallbladder”
Picture a gallbladder shaped like a pouch stuffed with seven letter F tiles, with a sticky note on it that says “RUQ after fatty food.”
- Fat (obesity/metabolic syndrome)
- Female (estrogen effect)
- Forty (risk rises with age)
- Fertile (pregnancy, multiparity)
- Fair (classically taught; in practice, epidemiology varies)
- Family history
- Fibrosis (cystic fibrosis → thick bile, biliary disease risk)
What the Pain Means (High-Yield Symptom Pattern)
Biliary colic
- Episodic RUQ/epigastric pain (often postprandial, especially after fatty meals)
- May radiate to right shoulder/scapula
- Nausea/vomiting
- No fever, no leukocytosis
- Pain often lasts minutes to hours, then resolves
When it’s not just biliary colic
Use this quick differentiation table:
| Diagnosis | Key clue(s) | Fever/WBC? | Labs | Imaging clue |
|---|---|---|---|---|
| Biliary colic (uncomplicated cholelithiasis) | Episodic RUQ pain after fatty foods, resolves | No | Usually normal | Stones may be seen on US (not always) |
| Acute cholecystitis | Persistent RUQ pain, Murphy sign | Yes | ↑ WBC | US: gallstones + wall thickening, pericholecystic fluid |
| Choledocholithiasis | RUQ pain + jaundice | Sometimes | ↑ ALP, ↑ direct bilirubin | US: dilated CBD |
| Ascending cholangitis | Charcot triad: fever + jaundice + RUQ pain | Yes | Cholestatic pattern | Needs urgent biliary drainage (often ERCP) |
| Gallstone pancreatitis | Epigastric pain radiating to back | Variable | ↑ lipase/amylase, may see ↑ ALT early | US may show stones; CT if severe |
Stone Types: The USMLE-Favorite Contrast
Cholesterol stones (most common in the US)
Mnemonic: “Cholesterol = C for Contraceptives, Calories, and Caucasian (classically)”
- Risk: female, obesity, pregnancy, OCPs
- Often radiolucent (won’t show on plain X-ray)
- Form due to cholesterol supersaturation or ↓ bile salts/lecithin
Pigment stones
Mnemonic: “Pigment = P for hemolysis and infection”
- Black pigment: hemolysis (e.g., sickle cell) → ↑ unconjugated bilirubin
- Brown pigment: biliary infection (classically in Asia; bacterial enzymes deconjugate bilirubin)
- More likely radiopaque than cholesterol stones (but imaging rules are imperfect—US is preferred)
Imaging: What Step Expects You to Choose
First-line test for suspected cholelithiasis/cholecystitis:
- RUQ ultrasound
- Fast, no radiation, detects stones and signs of inflammation
If ultrasound is equivocal but suspicion for cholecystitis is high:
- HIDA scan (cholescintigraphy)
- Nonvisualization of gallbladder = cystic duct obstruction (suggests acute cholecystitis)
High-Yield Management Pearls (Step-Style)
- Asymptomatic gallstones: often no treatment (watchful waiting)
- Symptomatic biliary colic: elective laparoscopic cholecystectomy (common definitive management)
- Ascending cholangitis: antibiotics + urgent ERCP (decompression is key)
- Gallstone pancreatitis: supportive care; ERCP if ongoing obstruction/cholangitis
Ultra-Quick Recap (Shareable)
- Mnemonic: 7 F’s + RUQ → Fat, Female, Forty, Fertile, Fair, Family history, Fibrosis (CF)
- Classic vignette: postprandial episodic RUQ pain ± radiation to shoulder
- First test: RUQ ultrasound
- Complication flags: fever (cholecystitis/cholangitis), jaundice (CBD stone), ↑ lipase (pancreatitis)