This document discusses the typical imaging features of various cysts and abscesses that can occur in the liver and other abdominal organs. It provides details on the characteristics of hydatid cysts, liver abscesses including pyogenic, amoebic and fungal types. Signs of cirrhosis, fatty liver disease, biliary dilatation, cholelithiasis, splenic cysts and renal cysts on imaging are also outlined. Key radiological findings like the "double target sign" and "cluster sign" that help differentiate abscess types are mentioned.

1. Typical cyst criteria
• Sharply defined margins
• Has no measurable wall
• Clear water contents 0-15HU
• NO
Septations
Calcifiations
Enhancement

3. HYDATID CYSTS
• Result from infection caused by echinococcus and an result in cyst
formation anywhere in body
• Daughter cysts within cysts
• Septations
• Splitting of cystic wall

7. LIVER ABCESS
• TYPES OF LIVER
• PYOGENIC LIVER ABCESS
Often polymicrobial, accounts or 80% of liver abcesses
• AMOEBIC LIVER ABCESS
Due to Entamoeba Histolytica, 10%
• FUNGAL ABCESS
Due to candida species, less than 10%

8. RADIOLOGIAL FEATURES
• As a general rule, bacterial and fungal abscesses are
often multiple, whereas amoebic abscesses are more
frequently single. Amoebic abscesses are more
common in a sub-diaphragmatic location and are
more likely to spread through the diaphragm and
into the chest.

9. ON CECT
• The "double target sign" is a characteristic imaging
feature of hepatic abscess demonstrated on contrast-
enhanced CT scans, in which a central low
attenuation lesion (fluid filled) is surrounded by a
high attenuation inner rim and a low attenuation
outer ring . The inner ring (abscess
membrane) demonstrates early contrast
enhancement which persists on delayed images, in
contrast to the outer rim (oedema of the liver
parenchyma) which only enhances on delayed phase

10. PYOGENIC LIVER ABCESS
• The "cluster sign" is a feature of pyogenic
hepatic abscesses. It is an aggregation of
multiple low attenuation liver lesions in a
localised area to form a solitary larger abscess
cavity.

12. AMOEBIC LIVER ABCESS
• They tend to be round or oval and be variable in size although most are
around 2-6 cm in diameter. An enhancing wall is present in most cases.
• Single or multiple near liver capsule
• Enhancing all is evident with peripheral edema

15. FUNGAL LIVER ABCESSS
• Radiographic findings On CT:
• multiple
• small
• hypodense lesions.
• Cluster or scattered

17. CIRRHOSIS
• Small fibrotic right lobe with regenerative enlargement of caudate and left
lobe
• Caudate / right lobe ratio: 0.65 0r more
• Portal vein diameter is more than 1.3cm
• Spleenomegaly, Ascites

20. DIFFUSE FATTY STEATOSIS
• Diffuse hepatic steatosis, also known as fatty liver, is a common imaging
finding and can lead to difficulties assessing the liver appearances
• Diffuse hepatic steatosis is common, affecting ~25% of the population.
• Radiographic features
• mild hepatomegaly (in ~75%)
• CT
• Steatosis causes reduced liver attenuation. This results in:
• low hepatic attenuation compared with spleen on non-
contrast imaging
– non-fatty liver is normally 6-12 HU greater density than
spleen
– if the attenuation of the liver is at least 10 HU less than
that of the spleen the diagnosis of fatty liver is made

22. BILIARY DILATATION
• Diameter of intra-hepatic bile ducts larger than 40% of diameter of
adjacent portal vein
• Dilatation of common bile duct greater than 6mm
• Gall bladder greater than 5cm

24. CHOLELITHIASIS
• Pure cholesterol stones are hypo attenuating to bile whereas calcified
stones are hyper attenuating to bile. Some gall stones are iso-dense to bile
and cannot be identified on CT
• Gallstones (cholelithiasis) describes stone formation at any point along the
biliary tree. Specific names can be given to gallstones depending on their
location:
• cholecystolithiasis: gallstones within the gallbladder
• choledocholithiasis: gallstones within the bile ducts
• Biliary microlithiasis refers to gallstones less than 3 mm in diameter.

27. SPLEENIC CYSTS
• Splenic cysts, although not particularly common, are the most common
focal lesion of the spleen. They may be congenital or secondary.
• CT
Typically shows a hypoattenuating relatively well-defined intrasplenic
lesion. The wall is thin and has a sharp demarcation to splenic
parenchyma. There is no rim or internal enhancement. Wall calcification
may be present.

31. SPLEENIC ABCESSES

34. RENAL CYSTS
• Renal cysts are a common finding in the kidneys. Findings common to all
"simple" renal cysts are well-marginated, thin walls with no enhancement of
the cyst.
• "simple cyst" (Bosniak I)
– well-marginated
– thin or imperceptible wall
– water attenuation (<20 HU on noncontrast series)
– nonenhancing
• ​<10 HU increase from noncontrast to postcontrast series is
nonenhancing
• 10-20 HU increase is indeterminate
• >20 HU increase is enhancement
• be wary of pseudoenhancement artifact

35. • hyperattenuating cyst (Bosniak II)
– well marginated
– thin or imperceptible wall
– hyperattenuating (60-90 HU on noncontrast series)
– nonenhancing
• ​<10 HU increase from noncontrast to postcontrast series is
nonenhancing
• 10-20 HU increase is indeterminate
• >20 HU increase is enhancement
• be wary of pseudoenhancement artifact
• increasing septation of the cyst, thick wall
calcification, and wall/septa enhancement are
concerning for renal cell carcinoma