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272 STUDENT BMJ VOLUME 10 AUGUST 2002 studentbmj.com

As outlined earlier in the series a smallnumber of densities may be seen on plainradiographs. The most radio-opaque(brightest) of any natural substance is cal-cium, which appears white. The reasoncalcium shows the greatest radio-opacityis that it obstructs x rays more than anyother natural substance. Consequently,fewer of those x rays reach the x ray plate,and the film appears white.

Iatrogenic or artefactual metallic

objects appear even brighter white (this will be discussed in the final part of thisseries). The vast majority of calcium iscontained in the bonesa normal,expected location (bony abnormalities willbe covered in the next part of this series).

The incidence of physiological calcifi-cation of normal anatomical structuresincreases with age and reflects that cal-cium is deposited over time.

Calcium can be seen in normal andabnormal structures. Abnormal calcifica-tion in some cases merely indicates under-lying pathology whereas in others thecalcification is the pathology.

Calcification of normalstructures (box 1)Evaluation of the abdominal radiographmight start at the top, working down the

film. The film should include the loweranterior ribs. As you will recall, towardsthe midline anteriorly, a rib changes frombone to cartilage and is termed costal car-tilage. The cartilage of ribs one to sevenarticulates with the sternum whereas ribseight to 10 indirectly connect to the ster-num by three costal cartilages, each of which is connected to the one immedi-ately adjacent to it (ribs 11 and 12 arefloating). This cartilage can calcify, whichis termed costocalcinosis. Althoughappearing strikingly abnormal, it is harm-less and usually age related (fig 1).

Further down, mesenteric lymph nodes

may calcify and appear as oval, smooth,outlined structures (fig 2). These can beconfused with small kidney stones, espe-cially in a patient without previous films who presents with abdominal pain. Aresuch incidental harmless calcified nodes

responsible for the pain or are renalcalculi This diagnostic dilemma may besolved by the exact location. If due calcifica-tion is identified along the urinary pathway(typically along the line of the transverseprocesses of the vertebral bodies) an intra-

venous urogram to compare against a plaincontrol film may be necessary for a decisivediagnosis. Alternatively, unenhanced com-puted tomography can be used. Also con-tained in the pelvis is the pelvic phlebolith,seen as a small, smooth, round, white opac-ity. Phleboliths are small areas of calcifica-tion in a vein. They may be difficult todifferentiate from small kidney stones.

The final calcification in this section isfound only in men. This is calcium that

collects in the ageing prostate gland and istherefore observed low down in the pelvicbrim. Prostate calcification may also occurin cancerous tissue.

Calcification indicatingpathology (box 2)

Pancreas The pancreas lies at the level of T9-T12vertebrae. Calcification of the pancreas isusually found in chronic pancreatitis,although there are some rarer causes. Ifcalcification is extensive, the full outline of

the pancreas may be observed, mostly onthe left side, but may cross over the mid-line. This speckled calcification occurson the network of ducts within the pan-creatic tissue where most of the calcium isdeposited (fig 3).

Renal calcificationBetween the T12-L2 vertebral region,nephrocalcinosis may be identified. Thisis calcification of the renal parenchymaltissue (fig 4). This is indicative of renalpathology, which includes hyperparathy-roidism, renal tubular acidosis, and

medullary sponge kidney.

Vascular calcificationPerhaps the most striking calcification is inthe blood vessels, most notably the arter-ies. The whole vessel(s) may be exquisitely

Abdominalxrays made easy: calcification

Ian Bickle and Barry Kelly return after a month off with the fourth part in their series on reading plainabdominalxray films

Fig 1

Fig 2

Box 2: Abnormal structures that

contain calcium

Calcium indicates pathology Pancreas

Renal parenchymal tissue

Blood vessels and vascular aneurysms

Gallbladder fibroids (leiomyoma)

Calcium is pathology

Biliary calculi Renal calculi

Appendicolith

Bladder calculi

Teratoma

Box 1: Normal structures that

calcify

Costal cartilage

Mesenteric lymph nodes

Pelvic vein clots (phlebolith)

Prostate gland

Fig 3

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outlined by calcium (fig 5). A great deal ofcalcification may be indicative of a wide-spread atheromatous process within thearteries, especially in diabetes.

In the infrarenal arterial region, belowthe second lumbar vertebrae, abdominalaortic aneurysms are typically located.Over time, as the atheromatous materialis laid down in the lumen, calcium may bedeposited. This may appear on an abdom-inal radiograph, and can be identified,often incidentally, by giving a rough indi-cation of the internal diameter. Anabdominal ultrasound scan should imme-diately follow for accurate assessment, andto determine the timing of surgery orobservational follow up.

Gynaecological calcificationThe final structure in this section is foundonly in womenfibroids. These can become calcified and appear as roundedstructures of varying size and location inthe pelvis (fig 6).

Pathological calcification The final section on calcification onabdominal x ray film refers to pathologi-cal calcification. This almost exclusivelymanifests as calculi in various locations.Calculi may be asymptomatic.

Biliary calculiBiliary calculi are commonly referred toas gallstones. Plain abdominal x ray film

in itself is poor at identifying these calculiand detects only 10-20%. Ultrasound isthe gold standard for first line imaging. Aplain abdominal radiograph is often theinitial investigation in patients withabdominal pain and may identify these

laminated, faceted, often multiple, radio-opacities in the right upper quadrant ofthe radiograph (fig 7). Very rarely a largecalculus may erode into the gallbladder

wall, creating a fistula to the adjacentsmall bowel. This calculus may then passalong the intestinal tract until it cannottravel any further, usually in the distalileum a little proximal to the ileocaecal

valve, and cause an obstruction of the

small bowel (see part 2 of this series). Gasmay also be seen in the biliary tree on theabdominal radiograph (see part 3 of thisseries). This phenomenon is termed agallstone ileus. In the right upper quad-rant the wall of the gallbladder itself may

Fig 5

Fig 6

Fig 4

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