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Gastroenterology encompasses a vast array of diseases, and it can be a challenge to memorize every little detail. In this post are the most high-yield hepatic and biliary topics in GI for the USMLE and ABIM. These notes are designed to be concise with learning tools to help you see the forest for the trees, as many attendings like to say.
 
Hepatitis
Hepatitis is most caused by viral infections and is also caused by alcohol and toxin ingestion. A classic presentation would be a patient with jaundice and/or scleral icterus as well as a right upper quadrant finding (tenderness vs hepatomegaly). Remember that ALT is more Liver specific, whereas AST can be elevated from more systemic insults. Alcoholism is not a liver-specific disease, which is why you can expect to see a 2:1 AST:ALT. Acute hepatitis often presents as nausea, vomiting, and malaise in addition to the above classic presentation, and treatments consist primarily of rest and supportive management. Chronic hepatitis can lead to cirrhosis with or without hepatocellular carcinoma.
 
IgM is a marker of acute infection, while IgG is a marker of chronic infection or immunization, depending on the situation. For Hepatitis B, just remember that anti-HBs-IgG (“s” for surface) is a marker of chronic protection; if a patient was exposed to Hep B instead of vaccinated, they will also have anti-HBc-IgG (“c” for core). Hepatitis A causes Acute illness. Hepatitis B most often causes acute illness but can progress to chronic hepatitis. Hepatitis C causes Chronic illness in 80% of patients.
 
Cirrhosis
Causes include alcoholism, hepatitis B or C, PBC, PSC, hemochromatosis, Wilson disease, a1-antitrypsin deficiency, NASH, and autoimmune hepatitis. Physical exam will show findings associated with hyperestrogenism, portal hypertension, and decreased hepatic synthesis. A definitive diagnosis is made with a liver biopsy, and ultrasound or CT/MRI can also show a cirrhotic/nodular liver. Complications include varices, ascites, hepatic encephalopathy, thrombocytopenia, coagulopathy, renal failure, and spontaneous bacterial peritonitis. Liver transplant is the only real treatment. Transjugular intrahepatic portosystemic shunting (TIPS) is exactly what is sounds like - shunting drainage past the liver decreases portal HTN, but without the filtering of the liver, patients are at increased risk of hepatic encephalopathy (from high ammonia).
 
Infiltrative diseases of the liver include hemochromatosis (iron deposition), Wilson disease (copper), and sarcoidosis (noncaseating granulomas). With hemochromatosis, look for “bronze diabetes” - increased skin pigmentation and new onset diabetes; labs will show elevated iron, ferritin, and transferrin. Wilson disease presents similarly to Parkinson’s but in a young person; look for Kayser-Fleischer rings in the eyes and decreased serum ceruloplasmin. 
 
Biliary disorders
Risk factors for cholelithiasis can be remembered with the four Fs - forty (years of age), female, fertile (pregnant), and fat (obese). Patients present with colicky right upper quadrant abdominal pain (on and off due to intermittent contraction of the gallbladder), which should be evaluated with a RUQ ultrasound (US). Patients are at increased risk for pancreatitis, and any patient with pancreatitis should have a RUQ US performed. If the pain becomes constant or if cholecystitis develops, the patient should undergo cholecystectomy. Cholecystitis has the Charcot’s triad of fever, RUQ pain, and jaundice. A HIDA scan is used if there is a high clinical suspicion for either condition but the ultrasound is not definitive. Acalculous cholecystitis can occur in patients on TPN or if they are critically ill.
Choledocoholithiasis has the same risk factors and differs in the location of the gallstone obstruction. Obstruction of the common bile duct leads to elevated LFTs as well as bilirubin. If the stone becomes infected, look for Reynald’s pentad of fever, RUQ pain, jaundice, altered mentation, and hypotension. Ascending cholangitis is a serious condition due to these sepsis findings, and in both cases the stone must be removed by ERCP before cholecystectomy to decompress the gallbladder. An MRCP is used if there is high clinical suspicion for either but ultrasound is not definitive.
 
Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are autoimmune diseases against the gallbladder. A classic presentation of PBC is a female possibly with another autoimmune disease who complains of itching and jaundice; labs will show elevated alkaline phosphatase (AP) and bilirubin with normal LFTs as well as positive ANA and antimitochondrial antibodies (AMA). UDSA can improve symptoms, and liver transplant is curative in progressive disease. A classic presentation of PSC is a male with ulcerative colitis who presents similar to PBC except without AMA. ERCP will show a “beads on a string” appearance of the intrahepatic bile ducts. Stenting of strictures can help with symptoms, and liver transplant may be required.

Further reading:

Now, That's What I Call High-Yield: Gastrointestinal

How to Study for the USMLE Step 1 — Part 3

High-Yield Subjects for the ABIM Internal Medicine Exam


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