Episode 3: Cholecystitis

Written By Learning Inthedark
 

Discover the 4 D’s of Radiology DETECT - DESCRIBE - DIFFERENTIAL - DECISION

DETECT

Epidemiology.

  • 25 million Americans are estimated to have cholelithiasis (stones present anywhere in the biliary system)
  • 80% of cholelithiasis is composed of cholesterol, with pigments or some form of calcium
  • 90-95% of cases of acute cholecystitis are secondary to gallstones
  • Acalculous cholecystitis comprises another set of cholecystitis and can be secondary to systemic infection, bile stasis, gallbladder ischemia, or cystic duct obstruction
  • 40% of patients with cholecystitis will develop complications

Etiology & Definitions.

Spectrum of Gallstone Disease

  1. Cholecystolithiasis: Gallstones within the gallbladder
  2. Choledocholithiasis: Presence of gallstones in the common bile duct (CBD)
  3. Biliary Colic: Transient obstruction of the biliary tree leading to intermittent pain
  4. Cholecystitis: Inflammation of the gallbladder
  5. Ascending Cholangitis: Biliary stasis leading to biliary sepsis which can be life threatening

Pathophysiology of Acute Cholecystitis

  • Cause: Most commonly gallstones become impacted in the cystic duct or gallbladder neck leading to increased intraluminal pressure and distension of the gallbladder. Ischemia and necrosis may occur if the obstruction persists

Clinical Presentation.

Colicky abdominal pain progressing to persistent abdominal pain located in the RUQ can indicate the presence of gallstones that are either transiently or persistently stuck within the biliary ductal system


Pain with deep palpation over the RUQ is termed the Murphy’s Sign and can be exacerbated by an ultrasound probe. It is indicative of cholecystitis


Classic clinical presentation of Ascending Cholangitis:

  1. Charcot’s Triad: RUQ pain, Fever, Jaundice
  2. Raynaud’s Pentad: Charcot’s triad + Hypotension + Altered mental status

Risk Factors for Gallbladder disease:

  1. Modifiable: Obesity, Rapid weight loss, diet, drugs, biliary stasis
  2. Non – modifiable: Age ≥40, sex, ethnicity, surgical resection of the terminal ileum (leading to poor absorption of biliary salts), family history, cirrhosis, Crohn’s disease

DESCRIBE

Anatomy of the Gall-bladder

Location: Anterior and inferior to segments IV and V of the liver

Components: Fundus which tapers to form the infundibulum to the neck of the gallbladder which then empties into the cystic duct

Blood supply: Cystic artery which is a branch of the right hepatic artery

Biliary system: Right and left hepatic duct meet up to form the common hepatic duct which joins with the cystic duct to form the common bile duct which will then insert into the duodenum

Bile filling is retrograde filling down from right and left hepatic ducts to the sphincter of oddi and then back up to the gallbladder

Imaging Workup

  1. Ultrasound:
    • Preferred first line
    • Useful for: Gallstone detection, sonographic murphy’s sign (high sensitivity)
  2. CT
    • Inferior to ultrasound in detection of gallstones but useful for the detection of complicated gallbladder disease
  3. Nuclear medicine scanning
    • Helpful in the context of uncertain cholecystitis diagnosis in particular with acalculous cholecystitis and negative or equivocal ultrasound findings
    • Helpful in differentiating acute from chronic cholecystitis
  4. MRCP
    • Heavily T2 weighted MRI looking at the biliary system
    • Non-invasive method of visualizing obstructed ducts
    • Can aid detection in query perforation evident on CT or when there is concern for a bile leak post cholecystectomy

Ultrasound Findings

  • Technique: optimal images are obtained with...
    1. Different acoustic windows including subcostal or intercostal
    2. Alternating patient position: Sitting, decubitus, standing, sitting

Cholelithiasis Findings:

  • Gallstones: mobile, echogenic foci with posterior acoustic shadowing. Wall echo shadow sign (hyperechoic gallbladder wall, hypoechoic space representing bile and then hyperechogenic line of the surface of a gallstone with acoustic shadowing distal to the gallstone) – can be present with large gallstone or multiple gallstones

Choledocholithiasis +/- Cholecystitis

  • Intra and extrahepatic duct dilatation – this is not present in everyone and lack of its presence does not indicate absence of stones impacting the bile duct
    • Extrahepatic duct dilatation is measured at the level of the common hepatic artery or right hepatic artery and should be > 6 mm + 1 mm per decade above 60 years of age. It can be > 10 mm post cholecystectomy
    • Measurements should be from the inner to outer wall
    • Intrahepatic dilatation: Generally > 2 mm or >40% of the adjacent portal vein. Helpful tip is to see the portal venous system adjacent to the dilated duct to ensure that you are looking at the intrahepatic component
  • Presence of a gallstone within the common bile duct - ensure to scan both proximal and distal common bile ducts
  • Further imaging with MRCP can be considered in patients presenting with a high clinical suspicion of CBD stone but no definitive ultrasound findings

Cholecystitis

  • Findings: Gallbladder wall thickening (> 3 mm), wall edema, gallbladder distension (>40 mm in the transverse plane and > 10 cm in the sagittal plane with convex walls), positive sonographic Murphy sign (very important!) , pericholecystic and perihepatic fluid
  • Very important to document the sonographic Murphy Sign as its presence conveys a high positive predictive value for acute gallbladder inflammation
  • Intra or extrahepatic biliary dilatation

Ascending Cholangitis

  • What: Acute bacterial infection of the biliary tree caused by biliary obstruction
  • All that clogs, is not gallstone! Causes can include an impacted stone, stricture from previous injury, PSC, or tumour
  • Findings: Thickening of the walls of the bile ducts (this can also be evident on CT). Ultrasound can also show biliary dilatation, presence of stones, pus or debris within the common bile duct

Acalculous Cholecystitis

  • Findings: gallbladder wall thickening (> 3mm), pericholecystic fluid, intramural gas, wall striation, mucosal sloughing, echogenic bile or sludge in the lumen of the gallbladder, diameter of the gallbladder > 5 cm
  • Risk Factors: ICU, trauma, mechanical ventilation, hyperalimentation, post-operative state, diabetes, prolonged fasting, burns, postpartum
  • Treatment: Cholecystectomy or cholecystostomy tube depending on clinical status

CT Findings

Cholecystolithiasis (“Gallbladder stones”)

  • Variable findings based on the degree of calcification. Some stones are iso-attenuating and poorly visualized in comparison to surrounding bile. Degenerated gallstones may look like a “Mercedes Benz” sign due to nitrogen demarcated by central fissures

Choledocholithiasis (“Ductal Stones”)

  • Classic presentation of a calcified gallstone would be hyperattenuating material present within the common bile duct. Variable presentation and sensitivity actually occurs, however, depending on the composition of the stone
  • MRCP may be indicated if not readily visualized on either CT or ultrasound

Acute Cholecystitis

  • Gallbladder wall thickening > 3 mm
  • Pericholecystic inflammatory fat stranding
  • Hypo or hyperattenuating gallstones

Complications

ACUTE COMPLICATIONS

  1. Gangrenous Cholecystitis
    • Pathophysiology: Gallbladder distension causes an increase in intraluminal pressure impeding blood flow leading to ischemia and necrosis
    • Findings on CT: Intraluminal membranes, irregular or discontinuous mural enhancement, wall defect. Alternating hyper & hypoattenuating regions are specific signs of necrosis on CT
    • Outcomes: Can lead to mural necrosis and perforation
    • Treatment: Emergency cholecystectomy or cholecystostomy tube placement
  2. Perforation
    • Location: most commonly in the gallbladder fundus
    • CT is more sensitive in the detection compared to ultrasound
    • Associated findings on CT: Mural defect within the gallbladder, extraluminal gallstone, presence of pericholecystic fluid with a collapsed gallbladder
  3. Emphysematous Cholecystitis
    • What is this: Gallbladder infection with gas forming organisms
    • Risk factors: Males and diabetic patients
    • Findings on CT: intraluminal or intramural gas
    • Ultrasound Findings: Presence of intraluminal gas – hyperechoic foci in non-dependent regions with associated comet-tail artefact or dirty acoustic shadowing
  4. Mirizzi Syndrome
    • Definition: extrinsic compression of the extrahepatic bile ducts by a stone present in the cystic duct or gallbladder (most often the infundibulum)
    • CT Findings: Diffusely thickened gallbladder +/- presence of gallstone impacted in the infundibulum or cystic duct

    CHRONIC COMPLICATIONS

  5. Gallstone Ileus
    • This is typically secondary to a cholecystoduodenal fistula
    • Findings on CT include
      • Rigler’s triad: Gallstones present in in the small bowel, evidence of small bowel obstruction, pneumobilia
      • Associated findings: fistula between the gallbladder and small bowel or colon
      • The level of obstruction commonly occurs at the terminal ileum
  6. Chronic Cholecystitis
    • Findings: Gallbladder wall thickening in the presence of gallstones with fibrosis of the wall. The gallbladder may appear collapsed due to the immobility from chronic inflammation
    • Porcelain gallbladder is a peripherally calcified gallbladder wall which may be seen in the context of chronic cholecystitis. It can be an indication for prophylactic cholecystectomy as there is a somewhat controversial association with increased risk of gallbladder carcinoma
  7. Postoperative bile leak
    • Findings: Nonspecific fluid collection in the gallbladder fossa. Most commonly caused by leak from cystic duct remnant or from duct of Luschka (cholecystohepatic ducts). Diagnosis by aspiration, nuclear medicine scan, or MRI with primovist (biliary excretion)

DIFFERENTIAL

Gallbladder Wall Thickening

  1. Gallbladder Carcinoma
  2. Xanthogranulomatous Cholecystitis
  3. Post-prandial physiological state
  4. Secondary thickening from: liver disease, PSC, infections
  5. Gallbladder Adenomyomatosis (generally more focal)
  6. HLH

Gallbladder Wall Distension

  1. Prolonged fasting
  2. Total parenteral nutrition
  3. Prolonged fasting
  4. Narcotic drug use

DECISION

Approach

  1. Non-Operative Management: Pain control, IV Fluids, Antibiotics
  2. Operative Management: Cholecystectomy – Laparoscopic with conversion to open in the context of challenging cases, difficult anatomy or complications
  3. Cholecystostomy Tube:
    • Indications – source control in setting of sepsis, high risk surgical patients, delayed presentation with significant inflammation
    • Placed under ultrasound guidance
    • Tube remains in situ for a prolonged duration with delayed surgical intervention
 

Typical Case of Cholecystitis

 

References

Peterson CM et al. Right upper quadrant pain. Available at https://acsearch.acr.org/docs/69474/Narrative/. American College of Radiology. Accessed June 18th, 2021.

O'Connor, O. J., & Maher, M. M. (2011). Imaging of cholecystitis. American Journal of Roentgenology, 196(4), W367-W374.

Dhir, T., & Schiowitz, R. (2015). Old man gallbladder syndrome: gangrenous cholecystitis in the unsuspected patient population. International journal of surgery case reports, 11, 46-49.

Ratanaprasatporn, L., Uyeda, J. W., Wortman, J. R., Richardson, I., & Sodickson, A. D. (2018). Multimodality imaging, including dual-energy CT, in the evaluation of gallbladder disease. Radiographics, 38(1), 75-89.

Becker, C. D., Hassler, H., & Terrier, F. (1984). Preoperative diagnosis of the Mirizzi syndrome: limitations of sonography and computed tomography. American journal of roentgenology, 143(3), 591-596.

Jones, M. W., Hannoodee, S., & Young, M. (2020). Anatomy, abdomen and pelvis, gallbladder. StatPearls [Internet].

Aubin JM, Ball CG. (2018). Dynamic practice guidelines for emergency general surgery: Biliary colic and cholecystitis. Canadian Association of General Surgeons. https://cags-accg.ca/wp-content/uploads/2018/11/ACS-Handbook-CPG-Ch-8-Biliary-Colic-and-Cholecystitis.pdf

Mandell, J. (2013). GASTROINTESTINAL IMAGING. In Core Radiology: A Visual Approach to Diagnostic Imaging (pp. 87-156). Cambridge: Cambridge University Press. doi:10.1017/CBO9781139225762.003

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