Ultrasound of the GallBladder: Pictorial Essay


Reviewed by Dr Ravi Kadasne

Normal Gallbladder is seen as a sonolucent pear shaped structure with slim wall (2 mm or so). Best seen with overnight fasting or at least 4-5 hours fasting. It is seen usually at the inferior aspect of the liver right lobe.

The Phyrgian Cap is a fold of the gall bladder seen at the fundus. It has no connections with gallstones or carcinoma. It is a benign finding seen commonly.

GB Duplication

GB Duplication is unusual but seen sometimes. Sometimes, there may be a diverticulum representing the duplicated gall bladder (see image below). If there is a doubt, a fatty meal may be given to see contraction - (not usually required though)

GB Wall thickening is diagnosed when wall is thicker than 3.5 mm. It is commonly seen in inflammatory conditions of the gall bladder like acute calculous cholecystitis, acalculous cholecystitis or chronic cholecystitis.?It is also seen in systemic causes like liver dysfunction, hepatitis, hypoproteinemia, dengue, and sometimes even in typhoid with liver involvement. Pseudothickening is noted in ascites as well.

Causes

Calculous Cholecystitis Acute or Chronic

Acalculous Cholecystitis

Carcinoma or adenomyosis

Pancreatitis

Ascites, Cirrhosis, Cardiac or Renal Failure

Low Proteins

Viral Hepatitis, Dengue, Malaria or Enteric infection

Gallstones

Gallstones are seen commonly on USG and this is the most sensitive test to detect gall stones. These stones are either cholesterol or bile pigment based, and calcium deposition occurs later. They occur due to chemical imbalance in the make up of the bile within the GB.

Common predisposing factors are fat, fertile female of 40, Obese patients with BMI > 30, sudden weight loss, patients on OCPs, and patients with cirrhosis and digestive disorders.

Radiographically, on xrays gallstones will be seen in only 10-15% of cases, with even less showing the classical Mercedes Benzsign of laminated stones that occurs due to fissuring.

Acute Calculous Cholecystitis

Acute calculous cholecystitis is one of the common causes of acute abdomen, presenting with pain in the RU quadrant, with fever and sometimes shoulder pain. Classical signs on ultrasound include presence of gallstones, wall thickening, sludge, pericholecystic fluid, and sometimes tenderness over the GB while scanning, termed the sonographic Murphy's sign.

Impacted GB Calculus with Acute Cholecystitis

Sometimes, the stone may get impacted at the neck of the gall bladder.

Hepatization of the GB

As the stone gets impacted at the gall bladder neck, the sludge echogenecity increases and the entire GB gets a bright homogenous echopattern that resembles the liver echo adjacent to it. This is called hepatization of the gall bladder.

GB & CBD Calculi

Gall bladder calculi are seen easily. What could be seen incidentally are small CBD calculi within the GB, with or without signs of obstructive jaundice clinically. Hence, its important to scan the CBD and measure it, and evaluate it for small CBD calculi.

GB Hydrops

Gall bladder hydrops is a condition that is seen during long hospitilization stays, post operative, post trauma, post burns wherein the patient is NBM, so the GB distends and the wall gets thinned out. It may be preceded by a viral or systemic infection (like Salmonella).

Chronic Calculous Cholecystitis

Chronic Cholecystitis is caused by repeated attacks of cholecystitis, and is diagnosed when the GB loses its ability to distend. What is seen in gall bladder calculi, with a thickened wall sometimes, and a partially distended GB.

WES Triad

The WES triad is another sign of chronic cholecystitis; here the WES stands for Wall (of the GB), Echo (of the calculus) and Shadow (caused by the stones).

GB POLYP

Gall bladder polyps are small well-defined mucosal outgrowths from the GB wall, and its difficult to exclude an early neoplastic mass from a polyp - if its increasing in size on follow up scans, it must be treated with suspicion.

Adenomyomatosis

Gall bladder adenomyomatosis is one of the hyperplastic cholecystoses and is caused by hyperplasia of the wall of the GB with formation of intra mural diverticuli that penetrate into the muscular layer of the GB wall. Cholesterol crystals then get trapped in these diverticuli, and give rise to the comet-tail sign thats diagnostic of this condition.

Cholesterolosis

Gall bladder Cholesterolosis is another of the hyperplastic cholecystoses and is seen as multiple GB polyps. It occurs due to lipid deposits on the surface of the GB mucosa (this is not seen on USG)

Adenoma/ Mass

Ill-defined masses or growths within the gall bladder are considered as suspicious for neoplastic lesions unless proved other wise, by other modalities.

Gall bladder masses may show intra luminal or exophytic growth that leads to intra hepatic extension. CT & MRI are imaging modalities that are required to diagnose this better.