Exophytic hydatid cyst of liver- CT

Exophytic hydtid cyst which is dumbell shaped and causing portal vein obstruction resulting in atrophy of right lobe of liver is unusual.

Other things about liver hydatid cyst are explained in my previous blog...Click on the following link..

http://manju-imagingxpert.blogspot.com/2009/08/hydatid-cyst-of-liver.html

Choledocholithiasis - MRCP

45 year old female with pain abdomen and jaundice underwent MRI and MRCP revealed calculus in the distal common bile duct obstructing the lumen resulting in mild to moderate upstream dilatation of the intra hepatic biliary radicals.

Discussion:

Choledocholithiasis is relatively common, seen in in 6 - 12% of patients who undergo cholecystectomy. They may present with biliary colic, ascending cholangitis, obstructive jaundice, acute pancreatitis. Stones within the bile duct may form either in situ or pass from the gallbladder, and when recurrent tend to be pigment stones, and are thought to be associated with bacterial infection.
USG: Sensitivity varies from 13 to 55%. Features include dilated duct with stones visualized within. Recently endoscopic ultrasonography (EUS) has also been used with very high sensitivity and specificity.
CT: Moderate sensitivity of 65 - 88% but have to look for very subtle findings. They are

• Target sign - Central rounded density of stone with surrounding lower attenuating bile or mucosa.
• Rim sign: Stone is outlined by thin shell of density.
• Crescent sign: Bile eccentrically outlines luminal stone, creating a low attenuation crescent.
• Calcification of the stone: unfortunately only 20% of stones are of high density

Setting window level to the mean of the bile duct and setting the window width to 150HU has been reported to improve sensitivity.
MRCP: is the gold standard investigations for biliary lithiasis replacing the ERCP. Filling defects are seen within the biliary tree on thin cross-sectional T2 weighted imaging.

Oriental cholangitis - MRI

42 year old female came with history of recurrent attacks of abdominal pain, fever, and jaundice. MRCP coronal HASTE image of upper abdomen shows dilatation of intrahepatic biliary radicles and CBD with multiple calculi within the hepatic ducts (L>R) and CBD (arrows). No calculi in the gall bladder. Thick slab MRCP image (left) better shows the IHBR and CBD dilatation with hepaticolithiasis and choledocholithiasis. Incidentally note the right retrocaval ureter.

Recurrent pyogenic cholangitis (RPC) or Oriental cholangiohepatitis is a recurrent and chronic and biliary tract infectious process typically seen in the Asian population, particularly Chinese. The disease involves recurrent episodes of infectious cholangitis with fever, abdominal pain, and jaundice. The causative infectious agents are typically bacterial such as E. coli and other coliforms. However biliary tract parasites such as Ascaris lumbricoides and Clonorchis sinensis are common coexistent pathogens, and it is not clear which infectious agents are the primary cause or representative of secondary superinfection.

The recurrent infections lead to bile duct dilatation, strictures, obstruction, and calculi. The bile duct dilatation may be pronounced and involves both the intrahepatic and extrahepatic ducts. There is a predilection for ductal involvement in the left lobe of the liver but diffuse intrahepatic disease can be seen. The extrahepatic bile duct can be quite dilated up to as much as 3-4cm in diameter. The dilatation of the extrahepatic duct may be secondary to loss of elasticity of the duct wall due to chronic infection or it may be due to ampullary narrowing.

The calculi are typically bile pigment stones with varying amounts of calcium. The stones have a mud or paste-like consistency. The stones presumably form due to bacterial enzymes causing deconjugation of bilirubin which then precipitates as calcium bilirubinate. In addition it has been postulated that a low protein diet as is seen in some Asian populations may play a role in formation of intraductal stones. MRCP is gold standard non invasive investigation for diagnosis of oriental cholangitis.

Focal Nodular Hyperplasia of Liver - CT and MRI

MRI of 30 year old female T1 weighted image showing well defined slightly hypointense lesion with central hypointense scar which is showing slightly hyperintense on T2 WI. In venous phase the lesion is showing homogeneous contrast enhancement (arrow). In delayed phase image there is enhancement of scar.

CT of another 28 year old female showing well defined showing arterial enhanging lesion in the left lobe of liver with central non enhancing scar. On venous phase image the lesion shows homogeneous contrast enhancement. In delayed phase image there is enhancement of scar.
Discussion:

FNH is considered a non-neoplastic, hyperplastic response to a congenital vascular malformation. Histologically, FNH is not a tumor and consists of benign-appearing hepatocytes occurring in a liver that is otherwise normal (i.e. no cirrhosis).
On CT scan the FNH are hypervascular lesions with homogeneous enhancement in arterial phase and hypodense central scars in arterial and venous phase, which enhance in the equilibrium phase. This is characteristic of FNH.
On MR typical FNH is slightly hypointense on T1WI and slightly hyperintense on T2WI. The scar is somewhat hyperintense on T2. The enhancement is as we expect with 'capillary blush' with a scar that enhances late in the equilibrium phase. We need to differentiate fibrolammellar carcinoma (FLC) of liver from FNH as the imaging findings are almost similar except for few differentiating points. The central scar is hyperintense on T2 in FNH where as it is Hypo in FLC. Scar enhances in delayed phase of contrast study in FNH where as it will not enhances in FLC. May see calcification in FLC and not in FNH.

Cholesterol gallstones

Fig1: CT scan of 57 year old female shows multiple hypodense small lesions of fatty attenuation seen in the gall bladder suggestive of cholesterol gall stones. Fig 2: USG of gall bladder shows multiple calculi in the GB.

Gall stones are of two types: 1. Cholesterol stones and 2. Pigment stones.

Cholesterol stones are made primarily of cholesterol of 70-80%. Where as pigment stones contain only 20% of cholesterol. Ultrasound is the most sensitive and best investigation for the diagnosis of cholelithiasis. CT can pick up calcified gall stones and cholesterol stone which contain more amount of cholesterol. Cholesterol stones appear dark on the background of isoense bile on CT. CT can miss gallstones which are not calcified.

Hydatid cyst of Liver

Multiphasic study of 55 year old male patient non contrast image shows well defined fluid attenuating lesion seen in the segment 8 of liver with rim calcification. The lesion does not show enhancement on arterial and venous phase. The findings are consistent with calcified hydatid cyst. (Type 5).

The liver is the commonest organ to be involved by the hydatid disease. The hydatid cyst can attain very large size before causing symptoms or may be incidentally dectedted early on investigation.

Types of hydatid cyst accodring to Gjarbi's classification bases on uSG appearance:

Type 1 : Pure fluid collection.

Type 2 : Fluid collection with a split wall.

Type 3 : Fluid collection with daughter cysts.

Type 4 : Heterogenous echopattern.

Type 5: Completely calcified lesion.

Preffered management is combination of Albendazone and PAIR techniqe - Puncture, Aspiration, Injection and Re-aspiration (PAIR).

Pracedure : Percutaneous drainage is performed under aseptic conditions with continuous sonographic guidance and intensive monitoring to treat any complications. Using a transhepatic approach, the cyst punctured by a 20-gauge needle and cyst contents aspirated rapidly. After aspiration, the cyst should be filled with a near-equal volume of 95% ethanol which will be left in the cavity for 20 min. Finally the cyst is reaspirated, irrigated and left partially filled with sterile 0.9% saline. Before and after injection of 95% ethanol, cyst fluid should be sent immediately for cytological and microbiological examination. Staining with neutral red is indicated in a viable cyst, while staining with methylene blue and eosin indicated in a non-viable cyst. Percutaneous drainage will be successful if the endocyst separated from the pericyst and if the reaspirated fluid shows a non-viable cyst. If not, percutaneous drainage was repeated at the same sitting to obtain success. After percutaneous drainage had been performed, all patients should be given albendazole 10 mg/kg body weight for 6 weeks. Othre treatment option is surgery which includes morbidity and mortality.

Non Alcoholic Steatohepatitis (NASH)

15 year old male obese boy came with pain in abdomen with elevated liver enzymes. He is non alcoholic, not taking any medication and tests negetive for hepatitis. MRI abdomen T1 weighted image shows diffuse fatty infilteration in the liver which is confirmed by loss of signal on ooposed phase chemical shifgt image. Findings are consistent with Non Alcoholic Steatohepatitis (NASH).

Synonyms: Hepatic fatty metamorphosis , Hepatic fatty steatosis, NASH

Nonalcoholic steatohepatitis (NASH) is fat in the liver, with inflammation and damage. It resembles alcoholic liver disease, but occurs in people who drink little or no alcohol. The major feature in NASH is fat in the liver, along with inflammation and damage.Patients generally feel well in the early stages and only begin to have symptoms—such as fatigue, weight loss, and weakness—once the disease is more advanced or cirrhosis develops.

We have to differentiate "Fatty liver", NASH and nonalcoholic fatty liver disease (NAFLD). Fat in their liver, but no inflammation or liver damage, a condition called “fatty liver. If fat is suspected based on blood test results or scans of the liver, this problem is called nonalcoholic fatty liver disease (NAFLD). If a liver biopsy is performed in this case, it will show that some people have NASH while others have simple fatty liver. Main causes for the NASH are elevated blood lipids, such as cholesterol and triglycerides, and many have diabetes or pre-diabetes, obesity.

USG shows diffuse increase in echotexture. CT scan will show diffuse decrease in attenuation. MRI shows intracellular fatty infilteration which is diffusely hyperintense on T1 weighted image (in phase image) and shows loss of signal on opposed phase chemical shift image. These MRI findings in patient with elevated liver enzymes suggestive of NASH. Liver biopsy and histopathology are diagnostic.

Confluent Hepatic Fibrosis (CHF)

Multiphase CT scan of 13 year old male patient with known case of cirrhosis, non contrast image showing atrophy of left lobe with capsular retraction. Arterial phase image does not show any enhancement. Venous phase image shows faint wedge shaped enhancement in segment IVa (arrow head) and the delayed image shows progressive incresed and persistant enhancement in segment IVa (arrow). Rest of the liver shows lace like enhancement. No mass effect or vascular displacement. The findings are consistant with Confluent hepatic fibrosis (CHF).

Pathology:

CHF Can be seen on imaging in approximately 14% of patients with advanced cirrhosis who are candidates for liver transplantation. It is associated with volume loss seen as retraction of overlying hepatic capsule or total shrinkage of segment or lobe.

Imaging Findings:

CHF is seen incidentally in patients with advanced cirrhosis who undego pretransplant imaging or imaging to ruleout hepatocellular carcinoma. Best diagnostic clue for CHF is pre-contrast CT showing hypo attenuating lesion with volume loss that becomes isoattenuating or minimally hypoattenuating at post-contrast CT, especially if wedge-shaped, located in medial segment of left lobe &/or anterior segment of right lobe, in patients with advanced cirrhosis. In our case the non contrast images are not showing typical hypoattenuation lesion. Wedge-shaped lesions radiate from porta hepatis & extend tohepatic capsule. Peripheral lesions are remote from porta hepatis. Lobar or segmental involvement, most commonly in lateral segment of left lobe. Retraction of overlying capsule seen in 90% cases.

The lesions are isoattenuating on post contrast images in 80% and hperattenuating on delayed scans. They show delayed persistent enhancement due to variability in contrast enhancement of confluent fibrosis relates to relative vascularity & extent of fibrosis.

MR imaging does show morphological changes & characteristic locations that suggest diagnosis, but no more so than CT. Lesions appear as regions of hypointense signal relative to adjacent liver parenchyma on T1 imaes and hyperintense on T2 due to prominant edema. They show delayed progressive enhancement on administration of gadolinium.

Differential diagnosis for focal liver lesions with capsular retraction apart from CHF are Cholangiocarcinoma, Treated metastases and sclerosing cholangitis.