This 13-year-old presents with hemolytic anemia. Look at the first three images. Images 1 and 2 are coronal T2-weighted images, while image 3 is a coronal 3D volumetric image from magnetic resonance cholangiopancreatography (MRCP). See how many observations you can make. There are five major ones. Also, think about what a plausible cause might be for this duct narrowing in a 13-year-old. Images 4-6 are duplicates of the first three images, but with arrows for key findings where applicable.
Coronal T2
Coronal T2
MRCP
Coronal T2
Coronal T2
MRCP
The five observations are:
- Hepatomegaly with low liver signal consistent with iron overload.
- Splenomegaly.
- Hypointensity or hypointense mass within the gallbladder (yellow arrow, image 5).
- Narrowing of the common hepatic duct (pink arrow, image 6).
- Ascites (green arrows, image 6).
Now that we’ve made those five key observations, I’d like to take a deep dive into the cause of this patient’s stricture, one of the longest explanations we’ve had in our case review series. If you’re pressed for time, I’d encourage you to bookmark this page and come back later. If you’ve got a few moments, let’s learn together.
The most plausible explanation for the patient’s duct narrowing is a stricture. Such a stricture in a 13-year-old with no surgical history or trauma other than the images provided most likely would be related to passage of a common duct stone or possibly Mirizzi syndrome. Since a globular mass exists in the gallbladder, it is plausible that this mass consists of a conglomeration of stones, one of which migrated from the cystic duct or eroded the adjacent common hepatic duct causing this stricture. Mirizzi syndrome is defined as hepatic duct obstruction (partial or complete) caused by extrinsic compression from an impacted stone in the cystic duct or Hartmann’s pouch of the gallbladder. While a stone is not currently identified, a passed stone from Mirizzi syndrome could easily account for the findings seen. The obstruction can occur at either the common bile duct or common hepatic duct level.
Mirizzi syndrome is more common in underdeveloped countries, particularly in Latin America. Essentially, an inflammatory phenomenon due to a pressure ulcer caused by an impacted gallstone at the gallbladder infundibulum causes external obstruction of the bile duct.
Such an erosion may result in a cholecystocholedochal or cholecystohepatic fistula. Pablo Luis Mirizzi, a surgeon from Argentina, originally described the syndrome. Mirizzi syndrome has been subdvided into various types (four types to be exact). The two major types include type 1, where there is external compression of the bile duct by a large stone or stones impacted in the cystic duct or Hartmann’s pouch and type 2, which consists of a proper cholecystobiliary fistula caused by gallstone(s) that have eroded directly into the bile duct. If the stone passes, and / or the ulcers heal, then a stricture may evolve.
Hemochromatosis or iron overload refers to iron in the body from any cause. Hereditary hemochromatosis (HHC) is a genetic disorder, while acquired iron overload occurs from transfusional iron overload.
Genetic forms of hemochromatosis are more common in people of Celtic (Irish, Scottish, Welsh, Cornish, British, etc.), English and Scandinavian origin. The mutation is the C282Y mutation on the HFA gene associated with HLA-A3. People with hemochromatosis manifest a very “black liver” on all MR sequences, including the ones displayed here. Whether it is a T1-weighted image, T2-weighted image, and especially on gradient-echo images (not shown), the liver is inordinately hypointense. If the overload is substantial, patients can develop secondary splenomegaly, liver failure and ascites. Our patient has all of these signs.
A second mutation has recently been discovered, H63D. Hemochromatosis is extremely rare in African-Americans, Asian-Americans, Hispanics, Latinos and Native Americans.
Hemochromatosis is associated with liver cirrhosis, bronzed diabetes, involvement of the heart with arrhythmias and cardiomyopathy, arthritis and erectile dysfunction. However, liver damage is the most notable, important and recognized sequela.
The two most important blood tests in making this diagnosis are the transferrin saturation test and serum ferritin test.
The transferrin saturation test shows how much iron is bound to the protein that carries iron in the blood. Transferrin saturation values equal to or greater than 45 percent are abnormal.
The serum ferritin test is more commonly used. Ferritin is a protein that stores iron in the blood. Levels above 300 mcg/L in men and 200 mcg/L in women are considered abnormal. Levels above 1000 mcg/L in men or women are most likely associated with clinically significant iron overload and organ damage. MR can be used to measure the degree of liver iron overload and quantify it. We will discuss this at a later date.
For more case review, head to MRI Online.
