CHAPTER six Soft Tissues

CALCIFICATION (MINERALIZATION)

Calcification is a process by which calcium salts are deposited in tissue. Dystrophic calcification is the deposition of calcium salts in abnormal tissue or tissue that is dead, degenerating, or damaged. Metastatic calcification is the deposition of calcium salts in tissue that is not the site of a disease process. It results from abnormalities in blood and tissue calcium and phosphate levels. It is associated with such metabolic disturbances as hyperparathyroidism (hypercalcemia) or hypovitaminosis D. Calcific deposits may be found in such soft tissues as the lungs, gastric mucosa, and kidneys (see Chapter 2, pp. 46, 58, and 136), as well as those around joints (see Chapter 4, pp. 420-422, 428, and Figure 4-45, A to C) and in the walls of blood vessels (Figure 6-1).

Figure 6-1 Calcification. A, Calcification (arrows) of the external ear canals in an old dog. B, Calcification in a chronically inflamed infraspinatus bursa on the lateral aspect of a shoulder joint. C, Calcification in a mammary tumor. The soft tissue swelling is well demonstrated. D, Calcified cataracts (arrows). Calcification. E, Calcification of the biliary tract, an incidental finding. F, This dog had a pendulous abdomen, polydipsia, and polyuria. The lateral radiograph shows a generalized mineralization of the soft tissues, particularly well seen in the soft tissues of the inguinal area. Diagnosis: Cushing’s syndrome—hyperadrenocorticism. G, A female 3-year-old cat with severe dyspnea, polydipsia, and harsh respiratory sounds on auscultation. Extensive mineralization of the soft tissues is seen. Note the prominent aorta, which is mineralized throughout its length. Diagnosis: dystrophic calcification caused by renal disease. Calcification. H, This 1-year-old Labrador Retriever presented with a left foreleg lameness of 2 months’ duration. The carpus was hyperextended, and tendon injury was suspected. Radiographs at the time of the injury were unremarkable. This subsequent study illustrates extensive mineralization of the soft tissues just proximal to the accessory carpal bone. This mineralized tissue extends distally to involve the body of the accessory carpal bone. Diagnosis: posttraumatic calcification. I and J, A 5-month-old kitten with a history of dyspnea. Lateral (I) and dorsoventral (J) views show widespread, symmetrical, pinpoint infiltrations throughout the lungs obscuring the normal thoracic structures. The diaphragm is flattened, and the gastric wall is mineralized. Rugal folds are visible as parallel radiopaque stripes. This was metastatic calcification caused by renal failure. Calcification. K to M, A 12-year-old Yorkshire Terrier had polydipsia, polyuria, and an enlarged abdomen. Lateral (K) and ventrodorsal (L) radiographs show hepatomegaly, a pendulous abdomen, and poor serosal detail. There is a vaguely circular soft tissue opacity in the left dorsal abdomen. It has a mineralized rim. It lies craniomedial to the kidney, with which it shows border effacement. M, An ultrasonogram shows a 5-cm-wide heterogeneous mass (M) invading the cranial pole of the left kidney. It has anechoic areas and hyperechoic foci (arrowhead) caused by calcification within the mass. This neoplastic mass could have arisen either from the adrenal gland or from the kidney.Calcification. N, A 9-year-old Kerry Blue Terrier presented with lethargy. There was proteinuria. Discrete areas of mineralization lie ventral to the thoracic vertebrae. Diagnosis: this was a mineralized adrenal gland. O, Coronary artery mineralization in a dog. A tortuous, mineralized linear structure is seen superimposed on the heart base on a lateral view of the thorax (arrows). This represents mineralization of vessels in the region of the coronary sinus. P, Several well-marginated mineral opacities are seen in the soft tissues distolateral to the great trochanter of the femur. They were an incidental finding. Diagnosis: dystrophic calcification. Q, This 2-year-old working German Shepherd presented with an unusual hindlimb action. On palpation both gastrocnemius muscles were hard distally. The longitudinal sonogram shows the normal muscle fibers (G) infiltrated by an echogenic infiltrate, causing acoustic shadowing (arrows) (proximal is to the left of the image). Diagnosis: myositis ossificans.

Calcification of the external ear canals may occur in old dogs (Figure 6-1, A). Hematomas or bursae may calcify, as may tumor tissue (Figure 6-1, B). Calcification of the medial meniscus of the stifle has been reported in dogs and cats (see Figure 4-5, B and C).

Calcium may be laid down in the skin and subcutis in Cushing’s syndrome (see Chapter 2, p. 123) and secondary to hyperparathyroidism (calcinosis cutis). The tracheal rings and bronchial walls may be affected and there may be diffuse pulmonary parenchymal mineralization (see Figures 3-12, E, and 6-1, F and G).

Mineralization of the coronary arteries may be seen as faintly radiopaque lines extending caudoventrally from the aortic root. Mineralization of the aortic bulb is occasionally seen at the level of the fourth intercostal space in the craniodorsal region of the cardiac silhouette (Figure 6-1, O).

Ultrasonography of calcified tissue can be unrewarding if a structure is only partially calcified. Deposits will be seen as hyperechoic foci scattered in the tissues (Figure 6-1, M). In myositis ossificans, bony plaques are deposited in muscle, or the muscle itself may become ossified. Trabeculated bone opacities may be seen. It may occur as a result of chronic trauma. Calcification cannot be distinguished from ossification unless a trabecular pattern can be identified (Figure 6-1, Q).

In calcinosis circumscripta (calcium gout, kalk gicht [chalk gout], tumoral calcinosis), deposits of amorphous calcified material are laid down in the subcutaneous tissue and skin. Lesions are usually found on the limbs, under the pads, or over bony prominences. Similar lesions have been described in the mouth. The etiology remains obscure. Chronic renal disease, hyperparathyroidism, and hypovitaminosis D have been suggested as possible causes. Approximately half the cases seen occur in young German Shepherds that are otherwise apparently normal (Figure 6-2).