Time Stamps

  • Pearl 1: Gallbladder Problems Spectrum
  • Pearl 2: Choose Imaging Strategicallyā€”Start with RUQ US, Escalate as Needed
  • Pearl 3: Biliary Tree Diagnostics
  • Pearl 4: Invasives that are Diagnostic and Therapeutic
  • Pearl 5: Stenting in ERCP

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Show Notes

Pearl 1: Gallbladder Problems Spectrum

  • What causes gallstones?
    • Gallstones = an imbalance in the components of bile (ex. cholesterol supersaturation) leading to crystal formation
      • Plus defects in motility of the gallbladder
    • Types:
      • Cholesterol stones are theĀ 
        • Most common stonesĀ  in the U.S.
      • Pigmented stonesĀ 
        • Seen in patients with chronic hemolytic diseases (e.g., sickle cell anemia, thalassemia).
  • What makes gallstones symptomatic?
    • Only when they obstruct the cystic duct, causing biliary colic!Ā 
      • Characteristic pain: a crescendo-decrescendo RUQ pain after fatty meals,Ā 
        • Can radiate to the right scapula
  • How common are gallstones and who gets them?
  • Who is at risk for gallstones?
    • The ā€œFour Fā€™sā€: Female, Fat, Fertile, Forty
    • Additional risk enhancers:
      • Pregnancy
        • Higher progesterone = decreased gallbladder motility PLUS Estrogens increase hepatic cholesterol secretion = cholesterol stones
      • GLP-1 receptor agonists (e.g., semaglutide, liraglutide)Ā 
        • Decreased GI motility
      • Rapid weight loss
      • Hemolytic anemia
        • Ā Pigmented stones (bilirubin-based)
      • Native American ancestry
        • Highest prevalence (up to 70% in Pima women by age 30!)
      • TPN (total parenteral nutrition)Ā 
        • Biliary stasis without oral intake
      • Spinal cord injuryĀ 
        • Decreased gallbladder contractility
  • What are the clinical manifestations of gallstones?
    • Biliary colic: Intermittent cystic duct obstruction ā†’ pain without inflammation
      • Self-resolves in hours
    • Acute cholecystitis: Persistent cystic duct obstruction ā†’ gallbladder wall inflammationĀ 
      • Look for RUQ tenderness, fever, leukocytosis
    • Choledocholithiasis: Stone in common bile duct ā†’ obstructive jaundice, transaminitis
    • Cholangitis: Choledocholithiasis + bacterial infectionĀ 
      • Charcotā€™s triad = RUQ pain + fever + jaundice
    • Gallstone pancreatitis: Obstruction of ampulla of Vater ā†’ lipase elevation, epigastric pain
  • What about acalculous cholecystitis? Who is at risk?
    • Occurs without stones, mostly in critically ill or post-op patients
      • Ex: ICU patient with unexplained sepsis and no clear sourceĀ 
        • Pathophysiology: biliary stasis + ischemia ā†’ gallbladder inflammation
      • Signs are subtle:Ā 
        • FeverĀ 
        • LeukocytosisĀ 
        • Vague abdominal discomfort
  • Summary
    • Cystic duct = Biliary colic/cholecystitis
    • Common bile duct (CBD) = Choledocholithiasis
    • CBD + infection = Cholangitis
    • Pancreatic duct = Gallstone pancreatitis

Pearl 2: Choose Imaging Strategicallyā€”Start with RUQ US, Escalate as Needed

  • RUQ Ultrasound (US): The First-Line Workhorse
      • Classic first lineĀ 
    • Pros:Ā 
      • Noninvasive
      • No radiation
      • Highly sensitive for stones
    • Best For: Suspected biliary colic, cholecystitis, or abnormal LFTs with a biliary pattern.
      • Gallstones: Echogenic with posterior shadowing.
      • Cholecystitis signs:
        • Gallbladder wall thickening (>3 mm), pericholecystic fluid
        • Sonographic Murphyā€™s sign (more specific than the clinical one)
    • Sensitivity: High for stones (85ā€“95%), but moderate for acute cholecystitis (it may miss up to 25% of cases).
    • Limitations:Ā 
      • * Operator dependent: Quality varies by the techā€™s skill.
      • Patient factors: Obese habitus, overlying bowel gas, or recent eating can obscure the view.
      • The “Blind Spot”: Often misses the distal common bile duct (CBD) due to duodenal gas, limiting its use for choledocholithiasis.
  • CT Abdomen/Pelvis: The “Catch-All” for Uncertainty
    • Pros:Ā 
      • Evaluates the entire abdomen and pelvisĀ 
      • Identifies alternative diagnoses (like appendicitis or diverticulitis) in about 32% of cases where biliary disease was suspected
    • Best For:
      • Perforation or abscess
      • Emphysematous cholecystitisĀ 
      • Patients who are ā€œcritically illā€ with an undifferentiated abdomen
    • Sensitivity: 50-90%
    • Limitation:
      • Not sensitive for gallstones
        • Especially non-calcified ones (which are the majority)
    • NOTE: Meta-analyses show no significant difference between CT and US for diagnosing acute cholecystitis. Itā€™s excellent for seeing wall inflammation and “stranding”
  • HIDA Scan (Cholescintigraphy): The Functional “Light Show”
    • How it works: A radiotracer is injected; if the gallbladder does not fill within 1ā€“4 hours, the cystic duct is obstructed (diagnostic for acute cholecystitis).
      • Biliary Dyskinesia: By adding CCK (cholecystokinin), we can calculate the Ejection Fraction (EF)
        • EF <35ā€“40% suggests dyskinesiaā€”functional pain without stones
    • Best For:
      • Bile Leaks: Useful post-opĀ 
        • If the tracer accumulates outside the biliary tree, youā€™ve found a leak
        • Acute cholecystitis
  • Sensitivity: 90-100%
  • Limitations:Ā 
    • Slow (hours)
    • False positives (see below)
  • The Caveats (False Positives):
    • Starvation/TNP or Opioids: Can prevent gallbladder filling, mimicking cholecystitis.
    • Liver Disease/Jaundice: If the liver canā€™t conjugate/excrete the tracer (common in cirrhosis), the test is “basically useless.”
  • The Clinical Reality: Even with a low EF and surgery, 30ā€“40% of patients with biliary dyskinesia may still have pain post-cholecystectomy.

Pearl 3: Navigating the Biliary Treeā€”From MRCP to Duct Dilation

  • MRCP: The Non-Invasive “Gold Standard” for Imaging
    • How it works:Ā 
      • MRCP uses T2-weighted sequences where stationary fluid (like bile) lights up bright white
        • This creates a high-contrast map of the ducts, making stones and strictures pop!
      • MRCP is diagnostic only: Unlike ERCP, it cannot remove a stone; it only confirms it is there
  • Why do we use MRCP over Ultrasound/CT?
    • Distal Visualization: Ultrasound loses resolution the further it gets from the probeĀ 
      • While US is great for the gallbladder, MRCP is far superior for the distal Common Bile Duct (CBD)
    • High Sensitivity: It has a ~95% sensitivity for picking up bile duct stones.
    • The “No Dilation” Rule: Don’t be fooled by a normal-sized duct on CT
      • 20ā€“30% of CBD stones present with no ductal dilation at all
      • The Catch: It requires the patient to lie perfectly still and follow breath-holding instructions
        • If the patient is confused or tachypneic, you’ll likely get a report of “severe motion artifact”
  • Decoding the “Dilated” Duct: When is it Normal?
    • We often see a 7 or 8 mm duct and think “obstruction,” but the biliary tree also “stretches with life”
      • Use the following to interpret dilation!
        • The Rule of Aging
          • General rules for “normal” CBD diameters can be much higher than the classic 6 mm cutoff:
            • Young/Middle-aged (<65): Up to 8 mm can be normal
            • Elderly (>65): Up to 11 mm can be considered normal
        • The Rule of Surgery
          • Post-Cholecystectomy: Once the gallbladder is gone, the duct acts as a reservoir and can stretch up to 13ā€“15 mm without pathology
        • The Opioid Effect
          • These can cause spasms of the Sphincter of Oddi ā†’ leading to asymptomatic biliary dilation that doesn’t require a procedure
            • Check the med list for narcotics or tramadolĀ 

Pearl 4: Stenting at ERCPā€”Not Always Necessary

  • EUS (Endoscopic Ultrasound): The Internal Scout
    • How it works: EUS is essentially an endoscope with a high-frequency ultrasound probe on the tipĀ 
      • Allows the gastroenterologist to place the probe directly against the stomach or duodenal wall, just centimeters away from the biliary tree and pancreas
    • Pros: By looking from the “inside-out,” you bypass skin, muscle, fat, and crucially bowel gasĀ 
      • This results in the highest resolution images possible of the distal bile duct and pancreas
    • Sensitivity: It is incredibly sensitive (>90ā€“95%) for choledocholithiasis
      • Specifically for “pesky” small stones (<5 mm) that MRCP might miss.
    • Beyond Stones: EUS is the workhorse for:
      • Tissue Acquisition:
        • Fine-needle aspiration (FNA)
        • Biopsy of pancreatic masses
      • Therapeutics:
        • Drainage of pancreatic fluid collections (pseudocysts)
        • Celiac plexus blocks for chronic pain management
    • Clinical Tip: If a patient has an MRCP that is “equivocal” but clinical suspicion remains high, EUS is the next best step to confirm a stone before committing to an ERCP.
  • ERCP: The Therapeutic Heavyweight
    • Endoscopic Retrograde Cholangiopancreatography (ERCP) is no longer a “diagnostic” tool.Ā 
      • Because of its risks, it is strictly reserved for therapy
    • The Procedure:
      • A side-viewing scope is passed to the duodenum, the bile duct is cannulated with a wire, and contrast is injected under X-ray (fluoroscopy)
    • Therapeutic Moves: * Sphincterotomy: Making a small cut in the muscle (Sphincter of Oddi) to open the duct.
      • Stone Extraction: Using balloons or baskets to pull stones out.
      • Stenting: Bypassing obstructions or strictures.
  • The Risks: Ā 
    • Post-ERCP pancreatitis (3ā€“10% of cases)
    • Bleeding
    • InfectionĀ 
  • The “Target” Rule: Go straight to ERCP only if you have a “clear target” (e.g., stone seen on CT/US, bilirubin >4, and clinical jaundice)
    • If there is any doubt, get the MRCP or EUS first
  • The Clinical Decision: To Scope or Not to Scope?
    • High Suspicion (Jaundice, Dilated duct + Stone on CT)
      • Next step: Straight to ERCP
      • Rationale: High pre-test probability; therapeutic intervention is certain
    • Intermediate Suspicion (Pain/Labs improving, “Maybe” stone)
      • Next step: MRCP or EUS
      • Rationale: Avoids the 10% risk of pancreatitis if the stone has already passed
    • Small Stone Suspicion (MRCP negative but LFTs still up)
      • Next step: EUS
      • Rationale: Highest sensitivity for stones <5 mm
    • Pancreatic Mass
      • Next step: EUS
      • Rationale: Needed for biopsy/tissue acquisition

Pearl 5: Gallbladder Management Is a Team Sport

  • The “Exit” Strategy: Sphincterotomy vs. Dilation
    • The bile duct exit (the Sphincter of Oddi) is often smaller than the stone trying to pass through it
      • To fix this, GI has to “enlarge the doorway”
    • Sphincterotomy: This is the universal “gold standard” for stone managementĀ 
      • Tiny wire with an electrical current to cut the sphincter muscle, permanently enlarging the opening
    • Balloon Dilation: Instead of cutting, use a balloon to stretch the opening
      • When? Usually reserved for patients with a high bleeding risk (e.g., those on anticoagulation or with severe coagulopathy) where a cut might cause significant hemorrhage
  • To Stent or Not to Stent?
    • A stent isn’t always necessary!Ā 
      • If GI clears the stone and the bile is flowing freely, they may leave the duct “naked”
    • NO, do NOT stent in the following:
      • Duct clearance complete
      • Bile flowing freely
      • Risk of lost follow-up
        • Avoid stent unless absolutely necessaryĀ 
    • YES, stent in the following:
      • The “Incomplete Clean”
        • If there are too many stones, or a stone is too large to remove in one session
      • Pus/Cholangitis
        • If the patient is unstable or “super sick,” the goal is “drainage first”Ā 
          • A plastic stent ensures bile (and pus) can bypass any remaining debris
      • Residual stone seen
      • Planned re-intervention
      • Unstable or anticoagulated
        • Partial drainage could be the safest route
    • Pro-Tip on Stent Life: Plastic stents are temporaryĀ 
      • They generally stay patent for 2ā€“3 months!Ā 
        • After that, they clog, corrode, or migrate.
        • They are a foreign body and must come out or be exchanged
  • What if the stone is too big? Lithotripsy!
    • What if a 12 mm stone is jammed in an 8 mm duct? GI has to break it up:
      • Mechanical: A basket with a “crank” that literally crushes the stone
      • Cholangioscopy (SpyGlass): A tiny 10 French camera goes inside the bile duct so the doctor can see the stone directly
      • EHL/Laser: Using shockwaves (Electrohydraulic Lithotripsy) or a laser to fragment the stone into small pieces that can then be swept out.
  • The “Gallbladder Problem”: ERCP is Not a Cure
    • Clearing the “pipes” (the bile duct) doesn’t fix the “factory” (the gallbladder).
      • The Standard of Care: Patients who have had a CBD stone are at high risk for a repeat eventĀ 
        • Refer to General Surgery for a cholecystectomy
    • The High-Risk Alternative: In elderly or very frail patients (e.g., severe dementia, high surgical risk), may perform a “maximal sphincterotomy” and stop there
      • Ā Eeduces recurrent biliary events in ~80% of cases, but nearly half of these patients may still experience a biliary event down the line
      • Trade off: Avoiding surgery vs. accepting a higher risk of recurrence
  • Ā 

Transcript

Dr. Shreya Trivedi: Welcome to the Core IM Five Pearls Podcast, bringing you high-yield, evidence-based pearls. I’m Dr. Shreya Trivedi, and I’m joined by.

Dr. Jahnavi Udaikumar: Dr. Ā Jahnavi Udaikumar. Hey guys, I’m a first year GI fellow at Houston Methodist. I think we have an interesting topic today. We’re going to talk about gallbladder and biliary pathology and imaging.Ā 

Dr. Shreya Trivedi: Yes, and I’m so glad you brought this episode to light because it’s something we see all the time, but to have that head space to just have a clearer framework, and I think for me more so, it was like the later pearls where we get to understanding why we’re choosing this modality versus that, that was gold. And with that, let’s meet our discussions for today.

Dr.Ā  Anoop Prabhu: Hey, I’m Anoop Prabhu. I’m an interventional endoscopist at the Roswell Park Comprehensive Cancer Center in Buffalo, New York.

Dr. Uzma Siddiqui: Hi, I’m Dr. Uzma Siddiqui. I’m a therapeutic endoscopist at the University of Chicago and director of our advanced endoscopy unit called the Center for Endoscopic Research and Therapeutics.

Dr. Shreya Trivedi: As always, test yourself with each of the following questions and pearls. Remember, the more you test yourself, the deeper your learning gains.Ā 

Dr. Shreya Trivedi:Ā  Pearl one, the foundation. How does where the stone gets stuck determine everything that follows?

Dr. Jahnavi Udaikumar: Pearl two, choosing imaging strategically. When should you start with an ultrasound? Why does a CT scan help? When do you escalate to something like a HIDA scan?

Dr. Shreya Trivedi: Pearl three, evaluating the biliary tree. When you see ductal dilatation or a rising bilirubin, how do you think through an MRCP? And what actually counts as “abnormal ductal dilatation”?

Dr. Jahnavi Udaikumar: And Pearl four, diagnostic versus therapeutic procedures. When do we reach for EUS versus ERCP?

Dr. Shreya Trivedi: And Pearl five, what actually happens during an ERCP? When do patients need a stent? And what do you counsel them afterwards?Ā 

Pearl 1: Gallbladder Problems Spectrum

Dr. Shreya Trivedi:Ā  All right, Jahnavi, let’s set the foundation before we get into the imaging and more of the management nuances. Let’s just do a quick run-through of the spectrum of diseases that these little guys who kind of say like they’re like the quiet roommates of the GI tract until they’re not can cause.

Dr. Jahnavi Udaikumar: I like to say gallstones or cholelithiasis is what happens when the bile just isn’t vibing. It’s not biling. If the bile just sits for too long, we get biostasis, and that biostasis is a nidus for formation of these gallstones, especially in susceptible patients.

Dr.Ā  Anoop Prabhu: Women are more commonly stricken with stone disease, gallbladder disease, certain ethnicities, so Native American, Pima Indians, certain age. So the older you are, the more likely you are to get stones. Obesity is a risk factor, as is dramatic weight loss. So often people who get a gastric bypass and lose weight from that, and it stands to reason maybe some of these newer GLP-1 receptor agonists might contribute to that as well. Pregnancy, where there’s a lot of changes in solubility of stones and hormonal changes. And then other medications like octreotide.

Dr. Uzma Siddiqui: When you get gallstones, it’s just kind of an imbalance, right? How your bilirubin’s broken down. Certain diseases, even like hemolytic anemia patients with sickle cell, they’re sometimes prone to getting stones too. So anytime you get an imbalance in your bilirubin breakdown, whether it’s hormones, medications, losing the weight really fast, those are all situations where it can just predispose you to the stones.

Dr. Jahnavi Udaikumar: So essentially, there are patient risk factors like age, gender, ethnicity, and then physiological states like pregnancy or rapid weight loss.

Dr. Shreya Trivedi: I didn’t think about rapid weight loss as kind of contributing to that biliary stasis you talked about. But I guess I’m glad you brought it up because we live in the age of GLP-1s, and so it’s definitely something we should be on the lookout for.

Dr. Jahnavi Udaikumar: Yeah, totally. And I think it makes more sense if you think about the primary mechanism. I think that’s limited fat intake and rapid weight loss. And so there’s less stimulation of the gallbladder and more biliary stasis. Then with GLP-1s itself, they directly inhibit gallbladder motility, and so there’s delay of emptying.

Dr. Shreya Trivedi: That makes a lot of sense. Okay. So I mean, so many people are walking around asymptomatic. They just have some gallstones. No problemo. Let’s get into when these gallstones cause some problemos.

Dr.Ā  Anoop Prabhu: So what happens is a stone essentially gets lodged in that duct, and it creates a blockage to the outflow of the bile that normally would be open. And so as a result of that, you get pressure within the system, the gallbladder gets distended, it gets painful, you get bacterial translocation, and then ultimately you develop cholecystitis. So in general, the pathophysiology of cholecystitis is cystic duct obstruction.

Dr. Jahnavi Udaikumar: And so if the gallstones are only causing an intermittent blockage of the cystic duct, we see that up-and-down crescendo, decrescendo, right upper quadrant pain after a meal. We know that to be biliary colic, but when that blockage actually becomes permanent, it causes cholecystitis.

Dr. Shreya Trivedi: Right. And then, of course, to distinguish biliary colic from cholecystitis, we’re going to see an infectious picture, radiographic findings. Okay. And then let’s migrate down. Say the stone goes down to the common bile duct, AKA choledocholithiasis. What different array of problems do aka choledocholithiasis and when that causes a different array of problems?

Dr. Uzma Siddiqui: If it blocks the bile duct tube, you can get potentially infections in the bile duct called cholangitis, or it can obstruct or block the pancreas duct, and you can get pancreatitis.

Dr. Jahnavi Udaikumar: Right. That’s perfect. Let’s round out our foundation pathology that we might see in acalculous cholecystitis.

Dr.Ā  Anoop Prabhu: Acalculous cholecystitis by definition, is without stones or acalculous. And so I like to think of it as essentially almost like a cholecystoparesis. So the gallbladder basically becomes paralyzed. And so if most cases of acalculous cholecystitis, as opposed to calculus cholecystitis, are cases that we see mostly in the ICU. So these are critically ill patients who have some sort of other pathologic issue going on. They’re critically ill. They get a distended gallbladder, and it becomes cholecystitis, but there’s actually no stones present.

Dr. Shreya Trivedi: To nerd out for a second, I do think it’s neat that all this ties back to the pathophysiologic phase of that initial biliary stasis, and that even works out with the Acalculus cholecystitis. And I think it reminds me of that larger kind of theme in the body just in general: stasis is no good. And I think my mantra more recently, even to myself, is movement. Movement is medicine. I guess with that, Jahnavi, why don’t we recap this very quick pearl?

Dr. Jahnavi Udaikumar: Pearl one, move, but pearl two, if I had to make it simple. Gallstone disease is often a problem of cholesterol overload and motility failure. So the stones are basically innocent until they block something and where they exactly block defines a disease.

Dr. Shreya Trivedi: Right. So the intermittent blockage is going to be that biliary colic. And then when the stones really get lodged in the cystic duct and cause inflammation and infection, that’s cholecystitis. And then blockage down in the bile duct, aka choledocholithiasis, that can lead to cholangitis. And if it even goes further down in the pancreatic duct, that can lead to pancreatitis.Ā 

Pearl 2: Choose Imaging Strategically: Start with RUQ US, Escalate as Needed

Dr. Shreya Trivedi: All right, so let’s paint the scene. Give a patient with a vague right upper quadrant pain, and you are faced with a choice of what is the best imaging modality as your kind of first go-to. Is it the right upper quadrant ultrasound for this patient or the CT abdomen?

Dr.Ā  Anoop Prabhu: A lot of times in the ER, unless there’s a lot of evidence to suggest that this is a right upper quadrant pathology, CT scan is usually the first test anyhow because it kind of is a catchall and will cover a lot of different things. It’ll get ureteral stones or appendicitis or diverticulitis or all these other things that are on the differential. Whereas a right upper quadrant ultrasound, you’re kind of putting all your chips in the idea that there’s something wrong in the right upper quadrant.

Dr. Jahnavi Udaikumar: So the first branch point is how confident are we that this is gallbladder pathology or maybe some other intra-abdominal processes? The good thing is the CT scan, of course, gives the entire abdomen pelvis in one go.

Dr. Shreya Trivedi: Yeah. It begs the question: is the CT just as good as the ultrasound when it comes to identifying problems with that gallbladder?

Dr. Uzma Siddiqui: The CT scan is it’s good for diagnosing acute cholecystitis because if you see a lot of inflammation around the gallbladder, a thickened wall, in that respect, it can be very helpful, but it’s not as good for picking up small bile duct stones and small gallstones.

Dr.Ā  Anoop Prabhu: CT is not very good at evaluating for stones. So that’s primarily because it’ll only see stones that are calcified, and the majority of stones are not calcified.

Dr. Shreya Trivedi: All right, so CT can be helpful when we’re worried about cholecystitis. And if we want to put numbers to it, for cholecystitis, the CAT scan has a pretty wide range of sensitivity, anywhere from 50 to 90%. The ultrasound, on the other hand, is operator-dependent, and depending on what study you look at, can miss up to 25% of acute cholecystitis. So it’s got a moderate sensitivity, just shy of 70% for cholecystitis.

Dr. Jahnavi Udaikumar: Yeah, I guess I can hum and ha looking at these sensitivities. But I mean, what really helps settle this is that when it comes to cholecystitis, there’s actually a meta-analysis that shows no significant difference between the CAT scan and the ultrasound for diagnosing cholecystitis.

Dr. Shreya Trivedi: Great. There. I like that we can kind of close that tab. What about small stones? It sounds like CT is less helpful, especially with gallstones that are not calcified. So then that got me wondering how good is the ultrasound then at picking out the pesky little stones that we might miss on CT?

Dr. Jahnavi Udaikumar: Shreya, that’s a great question. The right upper quadrant ultrasound actually excels at detecting gallstones. It has a high sensitivity for cholithiasis, approximately 85, 95%. But Dr. Siddiqui did teach me about some of the practical limitations that we have to consider.

Dr. Uzma Siddiqui: The times where it’s not as good though, if the patient is very obese or you have a lot of bowel gas; maybe they just ate, it can be a little bit harder to visualize the gallbladder.

Dr. Jahnavi Udaikumar: And then on top of that, the right upper quadrant ultrasound also typically misses some of the distal common bile duct. That’s because there’s bowel gas from the duodenum. So essentially the ruckus is limited in identifying choledocholithiasis.

Dr. Shreya Trivedi: Yeah. So I guess what I’m hearing is if ultrasound could be our real go-to if the patient’s been fasting, has the right body habitus, gives a story for slam dunk biliary colic or cholecystitis, we just need our patients to read the textbook and not give us these vague histories.

Dr. Jahnavi Udaikumar: Yeah, no biggie, right? Right. On the off chance they don’t really read the textbook and the picture is a little less clear. The CAT scan may not be the worst idea.

Dr. Shreya Trivedi: Yes, that is fair. All right. And I know sometimes both modalities might not give us the answer. And every now and then, GI will recommend a HIDA scan. And I don’t really know why. And sometimes I’m just like, okay, they said so I’ll order it.

Dr. Jahnavi Udaikumar: Yeah. So should I think of HIDA scan as the gallbladder light show? You put in some radio tracer, watch it flow. The HIDA scan actually is diagnostic when the gallbladder is not visualized.

Dr. Shreya Trivedi: Right. So I guess if the tracer doesn’t fill that gallbladder in a couple hours, that indicates a blocked cystic duct, AKA cholecystitis.

Dr.Ā  Anoop Prabhu: HIDA can sometimes be useful in other biliary pathology as well too. So bile leaks. So if somebody has a gallbladder removal and then they develop a bile leak, if you do a HIDA scan, you’ll see accumulation of contrast outside of the biliary system. So that kind of suggests there’s a leak.

Dr. Shreya Trivedi: Great. Bile leaks. Yes, this is when the bile fluid escapes the bile ducts or gallbladder and leaks into the abdomen. And we typically see this after surgery or trauma to the area.

Dr. Jahnavi Udaikumar: And then the HIDA scan also helps us determine how well that gallbladder really is squeezing.

Dr.Ā  Anoop Prabhu: So if you do it HIDA in somebody who has biliary pain and their ejection fraction is below 40, so they actually give CCK or cholecystokinin to the gallbladder to get it to squeeze. And then you look at how much is left before you inject it and how much is after, and then you develop a fraction. And if it’s below 40%, then that suggests that you’ve got dyskinesia.

Dr. Shreya Trivedi: Yeah. And just a quick refresher, biliary dyskinesia is a functional disorder where the gallbladder doesn’t empty properly, and that cuts that biliary type pain even though there’s no gallstones present.

Dr. Jahnavi Udaikumar: You’re right. And that’s why the gallbladder ejection fraction is just one piece of the bigger puzzle. The true gold is correlating a low EF with typical biliary colic symptoms.

Dr. Shreya Trivedi: Right. And then the other thing that I learned that I was like, okay, keep in mind for next time is false positives. So some people might have a low gallbladder ejection fraction just because they’ve been fasting for too long, not enough contraction or they’re on opioids or they’re septic.

Dr. Jahnavi Udaikumar: Yeah. One of our reviewers, Dr. Adam Goodman, says he doesn’t quite love the HIDA scan because patients with biliary dyskinesia, he’ll get a cholecystectomy, but a good portion of them, say about 30 to 40%, they’ll still have that continued pain. So it’s not a slam dunk that that said treatment actually helps.

Dr. Shreya Trivedi: Fair. And then that reminds me, one of our other reviewers, Dr. Elliot Tapper, he made the point that HIDA will be positive in patients with cirrhosis and jaundice because the HIDA is measuring the conjugation and expiration of the radio tracer. So basically useless in jaundice. All right. So I guess takeaway when it comes to initial imaging, the ultrasound’s going to be great for gallstones, cholecystitis. It’s fast, radiation-free, but depending on the operator can miss up to 25% of cholecystitis cases. On the other hand, the HIDA scan, it’s going to give us the highest accuracy for cholecystitis. And it also can help us measure gallbladder function, say for dyskinesia or detect bile leaks, but it can take hours, and it comes with its false positives from fasting, opioids, and acute illness.

Dr. Jahnavi Udaikumar: That was perfect. And to add on, the CAT scan actually has similar accuracy to the ultrasound for cholecystitis, but also good at identifying alternative non-gallbladder diagnoses, making it most useful when the entire clinical picture is really unclear.

Pearl 3:Ā  Biliary Tree Diagnostics

Dr. Shreya Trivedi: Okay, so we purposely chunked all the things for gallbladder pathology, right upper quadrant ultrasound, CAT scan, HDA together. But let’s say the right upper quadrant ultrasound, the CAT scan has some ā€œdilated bile ductsā€ inside the bilirubins elevated. This is where we’re going to pivot to biliary tree imaging. And let’s walk through what GI reaches for next and why.

Dr. Jahnavi Udaikumar: Yep. Let’s start with MRCP, which is usually the first non-invasive step.

Dr.Ā  Anoop Prabhu: So MRCP, some people get confused with that. It’s strictly an imaging study. It sounds a lot like ERCPs, but it’s simply an MRI that’s done with a different protocol to allow for optimal visualization of the bile duct. So MRCP is very sensitive for stones and very sensitive for stones in the bile duct, more so than for sure CT and also for abdominal ultrasound.Ā 

Dr. Shreya Trivedi: Yeah. So big picture, MRCP is going to shine compared to the CAT scan or the right portal ultrasound in that it’s going to give us the best sneak peek into the biliary tree. It’s going to be great at spotting dilated ducts, seeing if there’s any strictures, and it has a 95% sensitivity for actually picking up those bile duct stones.

Dr. Jahnavi Udaikumar: Right. MRCP is T2 weighted. So fluid-like bile lights up. It makes stones and blockages much easier to spot.Ā 

Dr. Uzma Siddiqui: I need the full-length bile duct image. And if I want to see the distal bile duct, because in some cases you might have a stone and the bile duct is not very dilated.

Dr. Shreya Trivedi: And then here’s a pearl. Just because you don’t see ductal dilatation on that initial CAT scan or right berocardinal ultrasound doesn’t necessarily rule out a stone. About 20 to 30% of common bile duct stones have no dilatation on the CAT scan.

Dr. Jahnavi Udaikumar: And there’s other plus sides to the MRCP. Thankfully, there’s no need for contrast, no sedation, just a long nap in a loud tube.

Dr. Uzma Siddiqui: MRCP, the patient does have to hold their breath here and there and lie still. So if you have a patient that can’t follow instructions, you’re going to get a report that says severe artifact and blurry images, so not as helpful.

Dr. Jahnavi Udaikumar: Yeah. So if you’re ordering an MRCP, just think ahead. Do you think this patient really can lie still for 30, maybe even 60 minutes to get the best images?

Dr. Shreya Trivedi: Yes, exactly. And then zooming out, it’s not just the image quality that’s going to affect our interpretation of the MRCP. The clinical context also matters. And I think this was a big teaching point because usually for me, if I see ductal dilatation, say it’s like nine millimeters biliary duct, I’m like, “Oh gosh, stone, we need to act.” But that is not always the case.

Dr. Uzma Siddiqui: And then one thing that we get consulted on quite a bit, if a patient is on chronic narcotics and tramadol; that can cause a little bit of spasm of your sphincter of Oddi muscle at the bottom of the bile duct, and the patient will get asymptomatic biliary dilation.

Dr. Jahnavi Udaikumar: And just like with any patient, look through their med list, see if they’re on opioids, see if those narcotics are contributing, especially if the patient presents asymptomatically. The other things that matter are age and if they already had their gallbladders removed.

Dr.Ā  Anoop Prabhu: And there was a recent study, I think about a year ago where it was just a cross-sectional study of healthy patients looking in Germany looking at what’s the normal cutoffs for sizes. And what they actually found is that up to 8 millimeters is reasonable in somebody 65 or younger. And as you get older, it can go up to 11 millimeters and be reasonable in an elderly patient. And in somebody who’s had their gallbladder removed, it can be upwards of 13 to 15 millimeters and be considered normal.

Dr. Shreya Trivedi: Great. I’m going to say it again just because this comes up often and it’s high yield. We can think about the ducts as stretching with life. We can expect the bile ducts to be up to eight millimeters when someone’s young and then to be 11 millimeters when they’re over 65 or so. And then if their gallbladder’s gone, we’re okay with up to 13 to 15 millimeters. All right, so with that being said, I think the next time I’m on service and a patient asks me, Dr. Trivedi, why do I need to get another study? I already had a CAT scan. I think I’ll be better equipped to say the MRC is going to give us a much better picture further down in that biliary tree. And then I think I’ll be more mindful when I’m looking at the interpretation of that bile duct dilatation and ask myself, is this person over 65? Do they have their gallbladder removed? And lastly, are they on any opioids, or did they get any in the emergency room?

Dr. Jahnavi Udaikumar: Yeah, that’s perfect. And in fact, it brings us to the more invasive things that we have on our hand that can be both diagnostic as well as therapeutic.

Pearl 4: Invasives that are Diagnostic and Therapeutic

Dr. Shreya Trivedi: All right, let’s get into things that are more invasive. We have two things, the EUS and the ERCP, and let’s start with the EUS.

Dr.Ā  Anoop Prabhu: So EUS is short for endoscopic ultrasound, and so it is also an endoscopic procedure. And essentially it’s a scope with an ultrasound probe on the tip of it. And so I tell patients, instead of looking from the outside in, we send the probe down into your stomach and intestine and look from the inside out. And so that allows us to get higher quality images because we’re not having to look through skin and muscle and fat and those other kind of interfering things. And it allows us to do therapeutics diagnostics so you can actually take biopsies and do lots of crazy interesting things with the EUS scope as well.

Dr. Jahnavi Udaikumar: Right. To drop the endoscope into the stomach or duodenum, and then doing an ultrasound from the stomach and duodenum to peek at what’s going on with the pancreas, the ampulla, the bile ducts, and any other surrounding structures. Thankfully, if the patient has ascites or has morbid obesity, it actually won’t impact image quality because we’re already inside.

Dr. Shreya Trivedi: Awesome. And one of our reviewers pointed out that the EUS is very sensitive. And then the plus side of EUS to mention is that it’s very sensitive in detecting small bile stones that might actually be missed on MRCP, which is interesting because I always thought MRCP, that’s it. But then it helped me click why sometimes GI might say, okay, no, we actually need an EUS. Studies say that the EUS is quite sensitive, like 90 to 95% when it comes to choledocholithiasis, especially for stones under five millimeters.

Dr.Ā  Anoop Prabhu: So you use an EUS, for instance, if somebody has a pancreas mass and you need tissue, so you’re often using them for fine needle biopsy or tissue acquisition. In this setting, that EUS would be done to evaluate the bile duct for stones.Ā 

Dr. Shreya Trivedi: Yes. I feel like I’ve definitely seen the EUS done for patients when we definitely need tissue or biopsy. But one thing I learned is that we can also reach for the EUS for pancreatic fluid collection drainage or for even pain management with a celiac plexus block.

Dr. Jahnavi Udaikumar: That’s perfect. Now from the EUS, let’s transition to ERCP.

Dr.Ā  Anoop Prabhu: ERCP is an endoscopic procedure where you’re actually sedating a patient going in and doing something to investigate or therapeutic. Before the advent of MRCP, ERCP was often one of the keystone diagnostic studies in the early workup of stone disease. But because of the high quality of MRCP and other complementary studies like EUS, diagnostic ERCP is essentially a non-existent entity now. So we strictly use it primarily for therapy, mostly because it’s not without risk, obviously pancreatitis, bleeding, and infection. And so we kind of reserve it for the cases where we know we need to do something therapeutically.

Dr. Jahnavi Udaikumar: And to be precise, actually post ERCP, there’s a risk of pancreatitis about three to 10%. So with an ERCP, GI is going in either to extract that stone, place a stent, or relieve an obstruction. We aren’t just scouting over there.

Dr. Uzma Siddiqui: So with an ERCP, we have a little catheter that we get into the bile duct with the little wire, and then we shoot some dye under x-ray to see the bile duct. Assuming it’s a stone, then we make a little cut that’s called a sphincterotomy. And then we have a little balloon, and we’ll pull the stone out. So if I have someone, they came in pain, elevated liver enzymes, they’re jaundice, and a CT scan is showing me a bile duct that’s a centimeter, and there’s clearly a stone in the bile duct, I will go straight to ERCP because I know I have a target. I’m going to do something therapeutic. If there’s any question as to the diagnosis, you’re going to get the MRCP or the EUS first.

Dr. Shreya Trivedi: Okay. I love this point because sometimes I feel like it’s a random why GI might recommend straight to ERCP the next day after a CAT scan in the ER or why sometimes they recommend more of an intermediate diagnostic step like MRCP or EUS. And to close that loop, it’s really to make sure that there is actually a stone in that biliary tree before they jump to an intervention like ERCP.

Dr.Ā  Anoop Prabhu: A case that might illustrate how we would approach this is there’s a patient who had her gallbladder out for a biliary colic and abdominal pain, and then a couple of days later presents with acute abdominal pain and what’s determined to be biliary pancreatitis. And so there’s a concern on imaging that there’s some sort of obstruction at the distal bile duct. But very quickly between when she presented and when she eventually was seen by our service, her pain had almost entirely resolved. And that was combined with liver enzymes that had almost entirely normalized as well. And so when you start to think about that case, if you think about what she looked like when she first came in versus what she looks like in the present time, so to speak, your pretest probability for whether or not there’s actually still, because you’re thinking, okay, she dropped a stone, she had cholecystitis, and there’s a stone in the bile duct. So I think your pretest probability for whether or not there’s still a stone there is lower later on in her course than earlier on in her course because of those things. Pain’s better, LFTs are better. And so earlier on in her case, you might be inclined to say, “Hey, we have sufficient evidence here. Let’s go straight to ERCP and remove what’s presumed to be a bile duct stone.” But later on in her presentation with those improvements in her clinical status and her labs and so on and so forth, knowing the risks of ERCP, you might be more inclined to get some sort of confirmatory test.

Dr. Shreya Trivedi: Ah, bless. When the stone just passes on its own, but really hammers home that we’re going to get an MRCP to take a better look or even potentially an EUS, though EUS is on the invasive side. Knowing that if with either of those we find a stone, the patient will still end up getting an ERCP.

Dr. Jahnavi Udaikumar: And pro tip. Some centers will do EUS and ERCP in the same sedation session. Two birds, one nap. Looks like I might need one after fellowship too.

Dr. Shreya Trivedi: I know. I’m a nap fan. Okay. So one thing I also appreciated was that Dr. Siddiqui was pretty real with us about sometimes the decision of what someone is recommending probably might just really be dependent on what’s available.

Dr. Uzma Siddiqui: In your own practice, you’re going to probably see people recommend one or the other with no rhyme or reason. A lot of it depends on just the availability at your hospital and timing. So if you consult me at 9:00 PM on a Friday, we’re going to tell you to get an MRCP. If it’s like 8:00 AM on a Friday, and depending on how backed up the MRI schedule is, a lot of times we’ll say, okay, bring the patient down.

Dr. Shreya Trivedi: That is so true. So what I’m taking away in terms of diagnostic and therapeutic purposes at the EUS and ERCP is that fundamentally they’re different tools with different thresholds. The EUS is an ultrasound basically from inside the stomach in the duodenum, giving us really excellent images, especially when we want to look at what’s actually going on in that biliary tree, really confirming choledocholithiasis, and great when we need tissue like, say, tissue of a pancreatic mass, or interventions like pancreatic fluid drainage or celiac plexus block.

Dr. Jahnavi Udaikumar: And then ERCP is actually reserved for situations with a high pretest probability where I’m so confident that a therapeutic intervention is much needed, whether I’m extracting a stone, placing a stent, or relieving the obstruction. Clinically, that means using MRCP or EUS as confirmatory steps when the patient’s course is improving, or there’s uncertainty that exists before an ERCP.

Pearl 5: Stenting in ERCP

Dr. Shreya Trivedi: All right. Sometimes I find patients go down for an ERCP and they come back with a stent and I’m like, “What? Surprise.” And then some don’t. And so it made me wonder what is actually happening in that ERCP?

Dr. Jahnavi Udaikumar: Turns out quite a lot happened, Shreya.

Dr. Shreya Trivedi: Yeah. I’ll have to admit before this episode, I fully didn’t understand who or who doesn’t get a sphincterotomy.

Dr.Ā  Anoop Prabhu: So if somebody has a stone almost with a few exceptions, they’re going to get a sphincterotomy. And I think the idea is that the reason the stone got stuck is because it’s bigger than the exit. This is kind of the most rudimentary way to think about it. And so you kind of cut the exit to be bigger, which is the sphincter body, and then you clean out all those stones to get it through. So typically you are doing something to make the exit bigger. In some instances, we end up dilating the exit instead, but in general, sphincterotomy is done almost universally for a stone management.

Dr. Jahnavi Udaikumar: And the dilation he’s referring to is usually done with a balloon. GI might use balloon dilation instead of sphincterotomy when bleeding risk is high. For example, patients who are anticoagulation or with coagulopathy.

Dr. Shreya Trivedi: And then how do we decide stent or no stent? And I think selfishly I’m wondering, is there any way I can predict that, okay, this patient’s going to come back with a stent versus this person is not?

Dr. Uzma Siddiqui: Sometimes that’s a judgment call. And if you ask four different interventional GIs, they might tell you something different. Because I know some people that are like, if there’s pus 100%, they’re going to always leave a stent. But sometimes you’ll go in, and you see a little pus, you get the stone out, you sweep the bile duct a few times, and then there’s no more pus; it’s draining bile very well. Then I won’t leave a stent because then I don’t have to go back now. If I say there’s a huge stone, multiple stones, and the patient’s super sick, unstable, my goal is just to go in, put in a stent, and get out. Usually in that situation, we will put a plastic stent. Those stents are good for up to three months.

Dr. Jahnavi Udaikumar: So these plastic stents, they aren’t meant to stay forever. There’s larger 10 French stents that last about three months while there’s smaller seven French stents that may have a median patency of about, I don’t know, two months or so. In practice, stents are often used when the duct can’t be fully cleared in one ERCP, whether that’s because there’s pus, multiple stones, or just the patient’s really sick. We’re trying to give the best chance for drainage from the bile duct to the intestine.

Dr. Shreya Trivedi: Yeah. Yeah. Thanks for saying that more explicitly. I guess I’m curious what happens, say you’re kind of doing the ERCP, you’re in there, and you just find the stone is just too big to remove.

Dr. Jahnavi Udaikumar: Yeah, that’s when lithotripsy actually comes in.

Dr. Uzma Siddiqui: We have different forms of lithotripsy: mechanical, which is a basket that is attached to a crank that can break up a stone. We also can do what’s called cholangioscopy, where you put this tiny 10 French camera inside the bile duct and then you apply either electrohydraulic lithotripsy, which is shockwaves with water, or laser. The factors that come into play, how big of an opening to the bile duct can I make? And that’s determined by each patient’s anatomy. What is the overall size of the bile duct? Because they may have an eight millimeter bile duct, but a 12 millimeter stone jammed in there that I cannot pull out with a balloon, so I’ll have to do lithotripsy to fragment it.

Dr. Shreya Trivedi: Great. It’s great to know that that’s available. Something else that comes up often is, I just recently had a patient that reminded me of this, is a 90-year-old who had cholangitis and had a stent placed. And our GI colleagues were like, “Yes, we’ll bring him back in four weeks or so to remove it.” But I’m like, “Wait a minute, this guy’s 90. He has Parkinson’s dementia. He’s going to a rehab.” But I felt skeptical. I was like, “I don’t know if this guy’s set up to come back in four weeks or so.” But I think it raises the question, what happens if our patients can’t make it back for a stent removal?

Dr. Uzma Siddiqui: A lot of times patients don’t come back in that timeframe and you’ll get away with it in a lot of cases, but they just tend to get clogged up after three months. So that’s why that’s usually kind of the max we put for a plastic stent. But sometimes they come back later. And I mean, rarely if it’s in for years and years over that timeframe, the plastic does get degraded. You could have the stent break off in the bile duct, but for the most part, they just get kind of clogged and corroded, and then you take them out. But it’s a foreign body, so you don’t want it in there forever.

Dr. Shreya Trivedi: Right. So it speaks to that kind of thing that we can all be doing better, which is checking in terms of goals of care and educating patients on that trajectory of these stents. They can clog, they can migrate, and more often they could fly under the radar and become forgotten.

Dr. Jahnavi Udaikumar: Yeah. The other part of counseling I think that often gets missed is what comes next. Just because the bile duct is clear, it doesn’t mean we’re solving the root problem because the gallbladder is still making stones. Patients will actually need to get their gallbladder removed and need to see general surgery for a cholecystectomy.

Dr. Uzma Siddiqui: They passed a stone into the bile duct once; the high likelihood they’re going to do it again. So if you don’t want to keep coming back with symptoms or infection or pancreatitis, you want to get your gallbladder out because that’s where the stones are being made.

Dr. Jahnavi Udaikumar: So in older patients or those patients who are really high risk for surgery will sometimes stop after the ERCP. We’ll do a sphincterotomy, clear the stones, and actually not take the gallbladder out. But I think it’s important to be honest about what that means long-term. This isn’t a cure. Almost half of patients can still have another biliary event down the line. So it’s a reasonable option when surgery just isn’t safe, and you’re trading off a higher risk of recurrence.

Dr. Shreya Trivedi: Yeah, I could see that. That’s fair. I feel like some patients that are more frail, elderly, you might say, “Okay, I’m willing to take that risk of maybe I’ll be the half that doesn’t have a recurrence with this stent in place or without a cholecystectomy.” Awesome. So let’s recap. My takeaway, number one, I guess, is a sphincterotomy. It’s often used and gives me flashbacks to med school and that enlarges the opening at the sphincter of OD, allowing stones to pass. And then if a stent is placed, it’s going to be temporary; knowing that stents can clog, they can migrate, and follow-up is needed for removal. And then even though the bile duct was clear during the ERCP, the ERCP is not going to prevent recurrence, right? The gallbladder is still making stones, and so we need to do clear counseling that there will need to be a cholecystectomy in the future if it kind of aligns with goals.

Dr. Shreya Trivedi: And that is a wrap for the episode. If you found this episode helpful, our ask is to please share it with your team. Check out the show notes. We’ll link the YouTube for the original interviews if you want to listen to some of the interviews more.

Dr. Jahnavi Udaikumar: And a huge shout-out, special thank you to our reviewers, Dr. Elliot Tapper and Dr. Goodman, for their time and their expertise.

Dr. Shreya Trivedi: And as always, opinions expressed on our own and do not represent the opinions of any affiliated institutions. Thank you. Take care.Ā 

References