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Radiology of the Abdomen--Chapter Four, Part 1



Abdominal Calcifications
Part 1

I. Introduction

Unusual calcifications, and other densities, noted on plain films of the lumbar spine are a common source of questions in a radiology consultation practice. Many densities are mundane and clinically insignificant. It will be apparent, though, that others might require follow-up and/or referral.

A. Types of calcification
  1. Concretions. A concretion is calcified mass formed within the lumen of a vessel or hollow viscus. They are created by the precipitation of calcium salts, as in kidney stones or by calcium deposition, as in phleboliths.

  2. Conduit walls. Conduits are hollow tubes through which fluids pass, such as the collecting system of the kidneys, the ducts of the biliary system and pancreas, and the vas deferens. The most common cause of conduit wall calcification in the abdomen is atherosclerosis of the abdominal aorta and its branches. Splenic artery calcification is also fairly common.

  3. Cystic or cyst-like calcifications. An example of this type of calcification is calcium deposition in a porcelain gallbladder. Aneurysms are also in this category. A critical feature of cystic wall calcification is the curvilinear rim of opacity which need not be completely visible.

  4. Solid mass. This category contains a diverse group of calcifications. They include calcified lymph nodes, and uterine leiomyoma.

  5. Amorphous. Of course this category exists when a density is difficult to characterize.
B. Physiology
  1. Dystrophic calcification. This is a result of local tissue damage from such things as trauma, ischemia and necrosis. There is normal blood calcium and phosphorous. Abdominal aortic atherosclerosis is a result of dystrophic calcification.

  2. Metastatic calcification. (In this usage, the term metastatic should not imply uncontrolled spread of cancer.) Calcium is deposited in otherwise healthy tissues secondary to systemic hypercalcemia and an alkaline environment. Conditions leading to this imbalance are hyperparathyroidism, and chronic renal disease.

  3. Concretion formation. Essentially stones, which form as a consequence of both local and systemic factors. Kidney stones, as an example, form due to a favorable medium caused by alkalinity (systemic) and local factors such as stasis and obstruction.
II. Abdominal calcifications

A. Concretions


1. Venous - phleboliths.

    This is the most common calcification within the pelvis with an estimated 35% of the population over 40 having them. When seen elsewhere such as the superficial soft tissues of the extremities, they may represent a feature of a soft tissue hemangioma.

    Phleboliths found within the pelvis are not clinically significant, other than simulating ureteral stones and other concretions. They do have an association with chronic constipation, however. It is thought that straining at stool eventually causes incompetence of the valves within veins which leads to thrombosis. The thrombus then calcifies.

    Radiologically, phleboliths are round to oval and measure 2 - 5 mm in diameter. They are well-defined, often demonstrating radiolucent centers. There should be no gaps in the continuity of the wall, a good way to distinguish them from arterial and cystic calcifications.

    The ischial spines mark the most superior location for the majority of phleboliths, but not all. This is a feature which may be useful in distinguishing phleboliths from ureteral stones.

    Phleboliths can be found just above the pubic bones to either side of the midline. Occasionally phleboliths are found within the scrotum.

    Phleboliths

    Gall stones - cholelithiasis

Gall stones are caused by precipitation of cholesterol salts, bilirubin pigments, or a combination of the two. Only 10-15% of gall stones contain enough calcium to be radiographically visible, but their high incidence in the population makes it highly probable that chiropractors will come across them -- usually on lumbopelvic and lumbosacral x-rays. They are classically seen in middle-aged, multiparous females and are usually associated with cholecystitis. Individuals with sickle cell anemia have a 50% incidence of gall stones with about 1/2 of these visible on plain film due to calcium content.

Evaluations of concretions in the right upper or right lower quadrants requires a general knowledge of the usual location of the gallbladder, which, of course, is not normally visible. The gallbladder is usually located at the intersection of the hepatic flexure of the colon (which usually contains enough air to be visible) and the lower edge of the liver.

Location of gallbladder (blue) relative to the colon.


Single gallstone

Patient A

Patient A

Patient B

Patient B

  1. Radiographic features
  • single or multiple
  • smoothly marginated calcifications
  • may be laminated and/or faceted
  • variable size, generally between 2 and 10 mm
  • radiolucent center common
  • occasionally may demonstrate a fissure in the center = "Mercedes Benz" sign


    Mercedes Benz Sign


  1. Oral cholecystography will demonstrate radiolucent stones which would escape detection on plain films. Ironically, the same contrast material may obscure stones that are radio-opaque. In the following two images, note how the opaque stones (right side) are more difficult to see with the contrast material.


    .

    Multiple lucent stones in
    gallbladder on transverse MRI

    Ultrasound showing multiple
    stones near cystic duct


Gross path. specimen



C. Milk-of-calcium bile within the gallbladder
  • countless minute stones composed of calcium carbonate which are held in suspension by bile
  • upright or cross table lateral films frequently show fluid level
  • secondary to cystic duct obstruction

Milk of Calcium Bile


D. Renal calcifications. There are two distinct types of renal calcifications: renal stones (nephrolithiasis) and nephrocalcinosis.

Collecting system stones (nephrolithiasis), are true stones. They develop due low grade infections, urinary stasis and most are related to pH imbalances in the urine. Stones are generally asymptomatic until they break loose. When the lodge at predictable locations, they cause excruciating pain, usually in flank region. Later the pain may refer to the groin. Hematuria can be seen in a urinalysis. The most common type of kidney stone in the US is calcium oxalate which happens to be the most radio-opaque type. Uric acid stones are not dense enough to show up on radiographs.

Patient A

Kidney Stone

Patient A

Patient B




Patient B




Radiographic features

  • calcification, single or multiple, overlying the kidney shadow
  • on lateral view, the density or densities overlie the spine because of their retroperitoneal location
  • small stones can be amorphous, but the larger stones may take on the shape of the calyces which they occupy
    • staghorn calculus- extensive struvite mineral deposition
    • take on the size and shape of the collecting system of the kidney
    • can look just like an IVP (look for absence of opacification of the ureters and bladder).


  1. Gross specimens

Medical treatment

Nephrocalcinosis represents calcification of the kidney parenchyma, instead of the collecting system. It results from abnormally high serum concentrations of calcium and/or phosphate. Usually people with this condition have an underlying serious illness such as: hyperparathyroidism, sarcoidosis, bone metastasis, steroids, hypervitaminosis D, and other rare diseases, as well as congenital abnormality (medullary sponge kidney).

Radiographic features

  • multiple, stippled calcifications within renal medulla and/or cortex
E. Ureteral stones

Renal calculi can become detached and pass into the collecting system. They then lodge in predictable areas of the collecting system which are known constrictions:

  • at the ureteropelvic junction
  • as ureter passes over the lumbar t.p.'s
  • at the entrance to the true pelvis, near the pelvic brim/sacral ala, where the ureters deviate sharply posterior
  • at the uretero-vesicle junction, which is the junction of the ureter with the urinary bladder (most common)

    Radiographic features

  • ureteral calculi are usually small (1-4 mm in diameter)
  • oval shaped stones will be oriented parallel to course of ureter ("rice grain" shaped)
  • most lie above level of ischial spines
Ureteral Stones
Phleboliths
Location
above ischial spines below ischial spines
Size
<4 mm 2-5 mm
Shape
round or oval round or oval
Orientation
long axis parallel to ureter variable

F. Appendicolith (aka: fecalith, coprolith)

Form after something like a seed becomes trapped in the appendix. The body then lays down endogenously produced substrate that eventually calcifies.

Clinical features

  • younger patients (under 30)
  • may not be symptomatic
  • symptoms of appendicitis + radiopaque appendicolith is highly suggestive of perforation of the appendix which is a surgical emergency

Radiographic features

  • located in RLQ
  • about 30% are radiopaque
  • usually solitary, occasionally multiple
  • laminations are common

Location of normal appendix

 

Appendicolith

G. Pancreatic calculi

Calculi in the pancreas are associated with chronic pancreatitis, most commonly a result of long-standing alcoholism. The normal pancreas spans the sagittal and parasagittal portions of the upper abdomen with the tail slightly higher and to the left.

    Normal location of pancreas

    Pancreatic calculi

H. Urinary bladder calculi

There is a high male predominance with 98% of all bladder calculi in the United States seen in elderly men. Urine retention from prostatic hypertrophy is a common predisposing factor. Radiological signs include:

  • solitary
  • smooth margins
  • densely opaque
  • midline location

  1. Bladder stone
I. Prostatic calculi

Prostatic calculi are associated with chronic prostatitis and are noted in men older than 40. The midline location of multiple, granular calcifications is nearly diagnostic.

 

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