Large deposits of fat over the spine, in the region of the falciform ligament in the cranioventral abdomen or around the apex of the heart may all suggest the presence of overnutrition or obesity.
Soft tissue organs should be examined on survey radiographs for changes in shape, contour, size, position or radiodensity.
In ageing animals several changes are commonly seen on survey radiographs which may have little or no clinical significance:
|(1)||In the chest cardiac enlargement (left sided, right sided or both) may occur in dogs in the absence of any clinical signs but associated with compensatory mechanisms such as in response to the leaking atrioventricular valves which occurs in endocardiosis.|
|(2)||Many older dogs (particularly the brachycephalic breeds) develop a pronounced bronchial pattem (doughnuts and tramlines) on lateral radiographs of the chest due to thickening and calcification of the bronchial walls. These changes may or may not be associated with respiratory signs such as abnormal respiratory sounds on auscultation.|
|(3)||In the abdomen hepatic enlargement is frequently noticed in both cats and dogs with the left hepatic lobe extending well beyond the costal arch on lateral views of the abdomen. Occasionally the liver size is reduced on survey radiographs, sometimes with cranial displacement of the axis of the stomach even though routine biochemistry tests for liver damage are normal.|
|(4)||Kidney size may be reduced in the presence of progressive renal dissuch as chronic interstitial nephritis in cats and increased in cases of renal hypertrophy or neoplasia, and the renal contour may be irregular due to fibrosis or the presence of neoplasia such as lymphosarcoma (which is also common in cats).|
|(5)||Dystrophic calcification can occur in many soft tissues notably the kidneys (where it usually occurs at the junction between the cortex and medulla), heart wall, urinary bladder, prostate, tendons and skin. In tendons the likely cause is chronic inflammation due to repeated trauma. However, in all such cases a primary underlying cause such as hypercalcaemia due to paraneoplastic syndrome, or Cushing's syndrome should be sought.|
|(6)||Animals with Cushing's syndrome (hyperadrenocorticism) and other conditions may develop calcification of the skin which, when overlying other structures, may confuse unsuspecting clinicians trying to interpret radiographs.|
Interpretation of the significance of radiographic signs can be difficult in older animals. It is helpful if comparisons can be made with survey radiographs taken earlier in life to determine significant changes and, if sequential films are available, they will give an idea of the timescale of progression of a lesion. This type of information can be very helpful with the development of subtle changes in, for example, the lungs.
If it were not for the potential health hazards associated with obtaining good radiographic images, and for the need to administer a general anaesthetic to most animals to get them, a good case could be put for obtaining screening films at various stages of an animal's life. In future the use of safe, noninvasive imaging techniques such as ultrasound will undoubtedly add a new dimension to our ability to detect early changes in organs through routine screening examinations.