Hepatobiliary Anatomy and Pathology

By Zach Krahn MS4

Anatomy Review

The liver is one of two organs in the body with a dual blood supply; the portal vein supplies ~2/3 of the total blood with the hepatic artery supplying the rest.

The major function of the liver is to filter the blood of toxins although it is also very important in protein synthesis and metabolism.

The gallbladder is the storage unit for bile, a substance that aids in fat metabolism

CT Basics

CT images are constructed based upon the differing density of substances in the body.

Dense substances (e.g. bone or metal) appear bright {hyperdense}

Low density substances (e.g. organ tissue or fat) appear less bright {hypodense}

Hounsfield units are used to describe the relative brightness of a substance on CT

Contrast, either oral or IV, can be given to better delineate anatomic structures

50 Shades of Gray

White

Shades

of gray

Black

Hounsfield units

Hepatobiliary CT

IVC

R Kidney

R renal artery

Aorta

L Kidney

Desc Colon

SMA

SMVGallbladder

Liver

Case #1Which is normal? What is abnormal?

Hyperdense material in gallbladder (biliary sludge, blood or contrast) with thickened wall

Without contrast, the bowel appears black (air)

The white “stuff” is contrast in the bowel

Case #1: CholecystitisPresentation: colicky pain (comes and goes), nausea,

and fever.

Risks: Obesity, gallstones, prolonged fasting

Treatment is usually surgical plus antibiotics

Case #2

Where is the abnormality?

What structure is it in? Common Bile Duct

Irregular soft tissue within the duct suggests malignancy. Dilation due to cystic common bile duct

Case #2: CholangiocarcinomaCholangiocarcinoma is a

cancer of the bile duct system

Symptoms include RUQ pain and intermittent jaundice

Risk factors: Clonorchis sinensis infection, toluene/benzene exposure, cysts within bile duct

Treatment: Surgical +/- adjuvant chemotherapy; poor prognosis

Case #3Where is the abnormality?

What structure is it in?

Note calcifications

Liver

Case #3: Hepatocellular Carcinoma Imaging demonstrates large

hypodense area within liver parenchyma, calcifications are present.

Common presentation: male between ages of 40-60, often vague symptoms including jaundice, RUQ pain, fever, weight loss

Risk factors: Cirrhosis, Hepatitis B (more so than Hepatitis C), hemochromatosis

Treatment: Resection, liver transplant, radiofrequency ablation.

Case #4What is abnormal?

What could it be? Blood (hemorrhage), pus (abscess), water (cyst)

Fluid around liver could also be blood, pus, or water

Case #4: Hepatic AbscessCT imaging shows an area

of necrosis surrounded by inflammation (heterogeneous density)

Common presentation: May be subtle. RUQ pain and fever may be present

Risk factors: Biliary tract disease, pancreatic disease, can be idiopathic

Treatment: Drainage and antibiotics

Case #5

What is abnormal? How do you know?

Spleen is normally about the same density as liver

Liver is less dense than spleen, suggests problem

Case #5: SteatohepatitisFat deposition in liver

parenchyma

Presentation: Often asymptomatic. May have RUQ pain, muscle pain, jaundice, liver enzyme elevations

Risk Factors: Obesity, excessive alcohol, extensive weight loss (bariatric surgery)

Treatment: Lifestyle interventions

Case #6

Abnormality? Describe the difference.

The edges of the liver should be smooth in appearance

This liver has a rough surface with many nodules

Case #6: Cirrhosis

Scarring of liver parenchyma due to chronic inflammation

Presentation: Fatigue, weight loss, jaundice, spider angioma, gynecomastia

Risk Factors: Alcoholism, Hepatitis C or B, history of blood transfusion before 1992 (before Hep C routinely tested), hemochromatosis

Treatment: Liver transplant, cease alcohol use, vaccinate against Hepatitis A, treat underlying condition

Take Home Points

Learning the anatomy now will help you better understand pathology and radiology in the future.

When looking at imaging studies, it is useful to know what “normal” looks like

CT imaging relies on the differing density of tissues whatever surrounds those tissues (air, water, fat)

References

Case in Point. American College of Radiology. Multiple topics: cholangiocarcinoma, cholecystitis, hepatocellular carcinoma

Dynamed. Topics: Cirrhosis, steatohepatitis, hepatic abscess

Images obtained from Case in Point at American College of Radiology, Imaging Consult, Radiopaedia