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
II. Abdominal calcifications
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.
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.
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.
This category contains a diverse group of calcifications.
They include calcified lymph nodes, and uterine
- Amorphous. Of course this category
exists when a density is difficult to characterize.
- 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.
- 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.
- 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.
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
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.
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
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.
- 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
Mercedes Benz Sign
- 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
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
- 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.
- 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
- can look just like an IVP (look for absence of opacification
of the ureters and bladder).
E. Ureteral stones
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).
- multiple, stippled calcifications within renal medulla and/or
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)
- 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
|above ischial spines
||below ischial spines
|round or oval
||round or oval
|long axis parallel to ureter
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
- 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
- located in RLQ
- about 30% are radiopaque
- usually solitary, occasionally multiple
- laminations are common
Location of normal appendix
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
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
- smooth margins
- densely opaque
- midline location
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.