Multisystemic Review of Calcifications Part 1
Review of all things calcium for the ABR Core Exam.
Show Notes/Study Guide:
What is the mechanism whereby Crohn’s disease makes calcium stones in the kidney. Can you be specific about what type of calcium stones are most associated with Crohn’s disease?
Crohn’s disease is associated with calcium oxalate stones. Oxalate normally binds with calcium in the bowel lumen to be excreted in the stool. With fat malabsorption, such as with Crohn’s disease, calcium in the bowel binds to fat more than it binds to oxalate. Oxalate is then reabsorbed at higher-than-normal levels and is renally excreted. These can then form calcium oxalate stones.
How does bile contribute to this phenomenon of calcium oxalate stone formation in Crohn’s disease?
Bile, which helps with fat absorption, is normally excreted into the small bowel to promote fat absorption and the bile is then reabsorbed in the ileum as part of the enterohepatic circulation of bile salts. In patients with Crohn’s disease that have ileal dysfunction and in patients who have had ileal resection, the bile is not reabsorbed, there is a paucity of bile to help with fat absorption, calcium binds to fat instead of oxalate, oxalate is then absorbed and renally excreted and can form calcium oxalate stones.
Bonus question: Struvite stones classically form secondary to which bacteria?
Struvite stones are classic on board exams and you need to know that they have ammonium that results from urease in the setting of proteous and/or klebsiella.
What are top differential considerations for a spiculated mesenteric mass that is calcified?
Think desmoid tumor, carcinoid, and sclerosing mesenteritis (retractile mesenteritis). Carcinoid is most common about the terminal ileum and pancreas and is arterially enhancing. Retractile mesenteritis has a classic “misty” attenuation. Note that all of these have various imaging manifestations but one way they can present is with a spiculated, calcified, mesenteric mass.
What is milk of calcium and how does milk of calcium typically appear on imaging?
Layering sediments of calcium within cysts. On imaging the appearance can show “tea cupping” or a meniscus-like effect with calcium sediments layering dependently within cysts.
Milk of calcium is most classic on mammography. What is the classic appearance of milk of calcium on a craniocaudal view and what is the classic appearance of milk of calcium on true lateral view?
Craniocaudal (CC): round amorphous (smudgy) calcifications. Lateral (LM or ML) or mediolateral oblique (MLO): tea cupping/layering, especially on extended hold views where you keep the patient in compression for a minute or so before you take the true lateral image to allow additional time for the calcium to layer. A key imaging feature for milk of calcium is that the calcifications change configuration between orthogonal views. Other types of calcifications in the breast do not classically change configuration on orthogonal views.
What if grouped calcifications on a mammogram appear amorphous on orthogonal CC and MLO or ML views?
If calcifications are amorphous on both orthogonal views, you have not confirmed milk of calcium and you need to biopsy. Entities like DCIS can present with amorphous calcifications.
A pathologist is examining core biopsy specimens from a stereotactic biopsy of calcifications, thought to possibly be related to milk of calcium. The pathologist does not see any calcifications in the biopsy specimen under standard microscopy. What could the pathologist consider adding to potentially reveal calcifications that are present but not seen on standard microscopy?
The pathologist could evaluate the biopsy specimens with polarized light which may show calcium oxalate which can be seen with benign milk of calcium. Calcium oxalate is seen under polarized light microscopy whereas calcium phosphate is the more common type of calcification seen on standard microscopy and is stained purple with H & E staining. Calcium oxalate is more likely to be benign whereas calcium phosphate can be benign or malignant.
Besides the breast can you think of another organ that can show milk of calcium on x-rays?
First, I think of renal cysts in which calcium can precipitate. Renal milk of calcium can also be seen in calyceal diverticula. The appear layering on layering on an erect film and rounded on a supine film (change configuration as also seen in mammography). You also can have milk of calcium in other places like the gallbladder but that is less likely to be tested on a radiology board exam.
What are Randall’s plaques?
These are subendothelial deposits of calcium carbonate or calcium phosphate within the loops of Henle within the kidney. These appear hyperdense on an abdominal CT but are not renal stones. Key is that these are abutted by 50% or greater renal parenchyma—they are intimately associated with the renal papilla and renal parenchyma. These are often thought to denote an increased risk of stone formation.
What is a key sequence that is necessary on a triple phase CT to differentiate contrast from calcium on CT angiography, such as for endoleak evaluation?
Precontrast imaging is key on a triple phase CT to differentiate between calcium and contrast. If the hyperdensity seen on later phase images is also present on precontrast images, then it is calcium. If the hyperdensity seen on later phase images is not present on precontrast images this is presumed to represent contrast, such as in an endoleak.
What are differential considerations for renal medullary nephrocalcinosis?
HAMHOP:
H=hyperparathyroidism
A=acidosis (Renal tubular acidosis)
M=medullary sponge kidney
H=hypercalcemia/hypercalciuria (sarcoid, milk-alkali syndrome, hypervitaminosis D)
O=oxalosis (Crohn’s disease, ileal surgical resection)
P=papillary necrosis
Remember a unilateral calcified kidney think TB as nephrocalcinosis would be expected to be bilateral
Bonus: What is a reasonable differential for renal papillary necrosis?
NSAID:
N=NSAIDs
S=sickle cell disease
A=acetaminophen
I=infection (TB, pyelonephritis)
D=diabetes/dehydration
The calcifications with renal papillary necrosis may be curvilinear or ring-shaped (arc of calcs around the papillary tips), or triangular in appearance (more extensive calcification of the papilla). Detached triangular calcs should make you consider sloughed papilla in the setting of renal papillary necrosis.
What are characteristic imaging findings of medullary sponge kidney?
Pyramid like calcifications of the renal medulla on a noncontrast CT that develop a paintbrush like appearance on delayed post-contrast images. These patients are often asymptomatic, but they can present with intermittent flank pain and/or UTI’s due to ureteral obstruction by small calculi in dilated renal tubules. The medullary pyramids would also look echogenic on ultrasound.
