Today, I review, link to, and excerpt from Core IM‘s Imaging for Acute Cholecystitis: ultrasound vs MRCP vs. CT vs. HIDA.
All that follows is from the above resource.
Imaging for Acute Cholecystitis: ultrasound vs MRCP vs. CT vs. HIDA
Transcript
Your patient presents to the emergency department with fever, right upper quadrant pain, and elevated white blood count. Acute cholecystitis is very high in your differential. How should we proceed with imaging? What should we order? The American College of Radiology appropriateness criteria recommends right upper quadrant ultrasound as a good starting point to evaluate a patient with these symptoms.
It’s fast, minimally invasive, doesn’t use radiation, requires no scheduling or sedation, is very good at finding possible stones, and could also find other pathology that could be sources of pain in this patient. You go ahead and order an ultrasound. Here’s a normal for comparison, and we get these images.
We found stones in the lumen of the gallbladder. Also, the gallbladder wall looks very thickened. Not only this, but there are areas of edema, these dark areas within the gallbladder wall, which suggests that some inflammatory processes at work. All these findings are concerning for acute cholecystitis.
Another bonus for starting with ultrasound. Literature has shown that ultrasound has a positive predictive value of 92 to 95% for acute cholecystitis. When you see stones plus gallbladder wall thickening, or stones plus a positive Murphy sign. What if the ultrasound hadn’t been so convincing and you still had a very high clinical index of suspicion for acute cholecystitis?
Luckily, we have imaging solutions for this conundrum. HIDA scans are a great follow-up for indeterminate ultrasounds and can provide increased sensitivity. It can also provide valuable functional data for the gallbladder, such as if chronic acalculus cholecystitis is suspected. However, these studies do take some time for scheduling and for setup with the appropriate tracer.
They also utilize radiation. If we were perhaps concerned that there was a distal stone in the common bile duct that maybe wasn’t well seen on ultrasound. MRCP shows beautiful pictures of the common bile duct and are really able to look at that distal portion. However, MRIs often take time for scheduling and may require sedation depending upon your patient population.
Let’s say we had another patient that was a direct admit to the ICU. They had imaging findings that were concerning for cholecystitis, but we’re concerned that perhaps they have gangrenous cholecystitis, or potentially a perforation. Now it’s time for a CT to shine. CT won’t always show all types of stones, such as cholesterol stones, but it is great for looking at complications of cholecystitis.
In this patient we can see that there’s sloughing and discontinuity of the gallbladder wall concerning for gangrenous cholecystitis. CT is also wonderful for finding gas within the wall and emphysematous cholecystitis or finding adjacent fluid collections in cases of perforation. So what did we learn today?
Right upper quadrant ultrasound is a great first line imaging modality when we are suspecting acute cholecystitis in a patient, if our clinical suspicion is high and our initial imaging is equivocal, we have many adjunct imaging options such as HIDA scan or MRCP depending upon the clinical picture. CT can also shine in cases where we’re concerned about complications.
