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 Hounsfield units White Shades of gray Black

Hepatobiliary CT Gallbladder SMV Liver SMA IVC R Kidney Desc Colon Aorta R renal artery L Kidney

Case #1 Which is normal? What is abnormal? Hyperdense material in gallbladder (biliary sludge, blood or contrast) with thickened wall Which is normal? What is abnormal? The white “stuff” is contrast in the bowel Without contrast, the bowel appears black (air)

Case #1: Cholecystitis Presentation: 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? Irregular soft tissue within the duct suggests malignancy. Dilation due to cystic common bile duct Where is the abnormality? What structure is it in? Common Bile Duct

Case #2: Cholangiocarcinoma Cholangiocarcinoma 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 #3 Where 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 #4 What 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 Abscess CT 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: Steatohepatitis Fat 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

Describe the difference. 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