INTRODUCTION

The routine procedures for the necropsy examination of domestic animals will be described first. To illustrate the technique, the dog will be used as the model for the methods employed. Before necropsy, evaluate the clinical history of the animal to have an idea of what organs or organ system should receive particular attention. Although the examination of all organs and systems is recommended, prior knowledge of the clinical history serve as a guide in knowing what to look for and what specimens should be collected to confirm the diagnosis.
 Specimens submitted for necropsy should be examined following a set of routine. Two methods are traditionally used in the necropsy examination of domestic animals: Routine necropsy, and cosmetic necropsy. Cosmetic necropsies is most often sought by the owner of companion animals, particularly dogs and cat owners and shall be dealt with in another section. This section shall deal with the routine necropsy procedures.
 The procedures for the routine necropsy examination of dead carcass can be conveniently divided into three major stages:

1) Dissection stage - consist of preliminary incisions to expose the various organs and body cavities for the examination.
2) Display stage - the stage where all organs are exposed but remained on their original position and relations.
3) Examination stage - the part of necropsy where specific organs and organ systems are systematically examined one after another.

DISSECTION STAGE

 Position the specimen with its left side down, with the feet facing the examiner (Figure 1). Carefully examine the animal's exterior. Note the body openings for the presence of secretions/excretions, prolapse, and color of mucus membranes. Examine the hair coat, and note for the presence of ectoparasites, areas of alopecia, thickening of the skin, crust formations, tumour masses, and possible wounds. Penetrating wounds should be probed and the extent or depth noted. Palpate the continuity of bony structures and look for evidences of fractures and abnormal masses.

Work with the right side of the specimen. The first incision is a straight line from the chin towards the ventral midline of the neck. Make an incision beginning from the chin and expose the mandibles and masseter muscles. Skin the neck and expose the underlying structures. Continue skinning backward to the flank of the right forelimb. Grasp and lift the right forelimb upward and cut all muscles between the subscapular area and the rib cage to free the limb. While doing this, locate, slice and examine the prescapular and axillary lymph glands. Examine the size and color and texture of the glands. After cutting all attachments of the forelimb, reflect the limb to the dorsum of the specimen (Figure 2).
 Hold the right hindlimb and cut the skin and underlying muscles of the hind flank. Expose the rim of the hip joint. With the aid of the tip of the knife, cut the round ligament to free the head of the femur and consequently the hindlimb. While doing this, take note of the articular surfaces of the acetabulum and the femur. Note also the amount, quality and quantity of the synovial fluid, and the appearance of the joint structures.
 

 Figure 1. Position of the animal for necropsy. Arrows indicate the course of primary incisions.

 Figure 2. The specimen after skinning and cutting the attachments of both limbs. Broken lines indicate the cuts that should be made to open the thoracic and peritoneal cavities.

The abdominal cavity is then opened. Palpate the free edges of the last rib and make a shallow incision sufficient to cut the abdominal muscles and peritoneum at this region while not cutting deeper structures. Lift the opening and continue cutting the abdominal wall from the dorsum and into the area of the xiphoid cartilage of the sternum. Continue cutting the abdominal wall at its dorsal and caudal boundaries down to the inguinal region. While this is done, note for the presence of ascitic fluid. Save as much fluid as possible for measurement of volume. Be careful not to cut the intestinal segments while doing this maneuver. After exposing the abdominal organs, leave the omentum that covers the intestinal loops for a while to avoid drying of the exposed segments.

Position the knife at the angle formed by sternal part of the diaphragm and the xiphoid cartilage of the sternum. Cut the sternal part of the diaphragm and note the presence or absence of negative pressure within the thoracic cavity (Figure 3). The presence of a negative pressure is suggested by the backward displacement of the diaphragm. Continue cutting the costal part of the diaphragm close to the inner rims of the ribs. The right side of the rib cage is then severed from its attachment to the sternum. In young subjects, cutting the costo-chondral articulation with the aid of a knife can easily do this. Old subjects may require the use of ordinary pruning shears or costotome. Cut the costo-chondral articulation from the last articulation and towards the first rib. Be careful not to severe the tongue, trachea and oesophagus lying freely at this region. Detach the wall of the rib cage by cutting the neck of the ribs and associated intercostal muscles to expose the thoracic organs.
The pelvic cavity is then opened. This is done by sawing the ilium close to the rim of the acetabulum at both sides (Figure 4). Then, saw the ischium from behind at both sides. Remove the sawed portion of the pelvic bone by cutting all underlying attachments to expose the pelvic cavity and its contents. At this point, the buccal, thoracic, abdominal and pelvic cavities and their contents are exposed for detailed examination.

DISPLAY STAGE

 The display stage is that part necropsy examination when all the organs are exposed for close inspection. This stage is the best time to examine the whole carcass where all organs are exposed and remains untouched. Examine the exposed organs and note their relations, position, and external appearance. Lift carefully the organs for a much-detailed examination of the whole structure. Exercise extra care so as  not to unnecessarily displace the organs at this stage.

If frank or clotted blood is present in any of the body cavities, carefully look for possible bleeding points. Should this be noted in the abdominal cavity, take particular attention to the surfaces of the liver and look for small fissures and cracks on the surface. In most traumatic conditions (e.g., vehicular accidents involving small animals), fissures and cracks on the liver parenchyma may be subtle or not readily apparent. Unfortunately, the same may be easily produced by handling and thus information concerning this condition is easily lost or overlooked. Manipulation and unintentional cutting of blood vessels may leak blood into the body cavity and make the appreciation of internal bleeding difficult. However, antemortem bleeding into the body cavity usually have accentuated lymphatic vessels filled with blood.

Evidence of gastrointestinal accidents (torsion, volvulus, intussusception, strangulation, rent and tears in the omentum and mesenteries) is best examined at the display stage. Excessive manipulation of organs could easily dislocate relationship of organs, making the examination and recognition of strangulation, volvulus and intususception difficult. Similarly, small holes in the omentum or mesentry caused by abdominal accidents most often are overlooked, easily lost, or inadvertently produced.

Should specimens for laboratory examination be required, the display stage is the best time to collect the required samples. Tissue blocks intended for histopathological studies should be collected at this stage. This is recommended since excessive handling of organs and tissues during the examination stage will most often produce artefacts in tissue sections. After carefully observing the organs at this point, the detailed examination of any organ or organ system follows.