Examination of the Abdominal Organs

The abdominal organs, particularly the gastrointestinal tract takes priority in the examination of organs. Their content of enzymes and bacterial flora render these organs to undergo rapid post mortem autolysis. It is desirable to remove the entire alimentary tract from the rest of the carcass. This will minimise soiling of the carcass with spilling digesta from the opened alimentary tract segment.

Remove the whole segment of the gastrointestinal tract. To do this, grasp the large intestine and cut its mesenteric attachment. Cut the portion of the large intestine as it enters the pelvic cavity. While holding the cut segment of the large intestine, severe the mesenteric attachment of the large and small intestine. This will free the whole segment of the gastrointestinal tract. Grasp the whole structure, including the stomach and spleen and expose the duodenal loop where the bile duct opens. Gently press the gall bladder and note if the bile would flow freely from the bile duct towards the duodenal loop. A small cut at the segment of the duodenum where the bile duct opens may be required to determine this condition. Then, grasp the body of the stomach and gently press the cardia and the oesophagus close to the oesophageal hiatus of the diaphragm. Free the stomach the segments of the intestines by cutting the oesophagus. Remove the spleen by cutting the omental attachment from the body of the stomach. Place the whole gastrointestinal segments on one side of the table. With the aid of a pair of scissors, the stomach is first opened by cutting from the cardia and down at the greater curvature towards the pylorus. Spread open the stomach and gently remove its contents. Examine the contents and qualify and the thickness of the walls. Note for the presence of ulcers, evidence of calcification, strictures, perforations, foreign bodies, and exudates.

Free the entire length of the intestine by cutting close to the mesenteric attachment segment by segment. While freeing the duodenum, exercise care not to damage the pancreas which should be examined at this stage. Note for nodule formations, colour, and texture of the organ. Examine also the adjacent adipose tissues and look for evidence of necrosis of fat. Cut open the intestine as the segment is freed from its attachment. Some workers suggested that the whole segment of the gastrointestinal tract be opened. While this is ideal, the time involved in opening the whole segment may be staggering. For an average sized animal, this may reach to four meters and consequently require much time. Also, the subdivisions of the intestinal tract may not be appreciated if the whole segment is freed and lying as a straight tubular structure on the table. Moreover, accidental cutting of segments may leave the examiner losing track of the continuity of the structure. As an alternative, the intestines may be examined leaving their mesenteric attachment intact. Locate and open a representative segment of the duodenum, jejumum, ileum, caecum and colon. Examine the contents, the appearance of the mucosal surfaces, thickness of the walls, presence of ulcers and strictures, foreign bodies, and exudates. Qualify the color, odour, and consistency of the contents. Samples taken from the segments of the gastrointestinal tract intended for laboratory examination should be evaluated as to its relative merits. Considerations should include the time elapsed since death of the animal.

Examination of Thoracic Organs

The next step is to examine the thoracic organs. Removal of the organs from their attachments in the thoracic cavity is recommended. To do this, grasp the tounge, trachea and oesophagus lying close to the thoracic inlet. While lifting these structures and pulling backwards, cut the pleural attachments of the lungs. Severe the aorta and other vessels to free the lungs and the heart. Lay the freed organs at one side of the table.
 Inspect the dorsal and ventral surfaces of the tounge. Note for the presence of ulcers and suppurative foci and wounds. Palpate the tounge muscles and look for nodules or abnormal masses. Inspect the thyroid and parathyroids at both sides. Cut open the whole lenght of the oesophagus and examine the mucosa for the presence of ulcers, strictures, and abnormal tissue masses. Open the trachea and examine for haemorrhages, fluid or froth content, foreign bodies and broken cartilage rings. Continue examining the trachea down to its minute bronchial terminations in the lungs. Look for evidences of dilatation, collapse, foreign bodies, fluid and/or froth content. Animals that died from lung oedema may show a stable froth in the trachea.
 Examine the surfaces of the lungs and pleural investments by ocular inspection and palpation. Look for changes in colour and consistency of individual lobes, collapsed or dilated lobes, and for the presence of abnormal tissue masses. Areas of consolidations should be characterised as to location and degree of involvement of lung parenchyma and its distribution. An apical distribution is most often an indication of bronchopneumonia.

Examination of the Heart and Blood Vessels

 It is convenient to examine the heart that is still attached to the lungs. Grasp the heart on one hand and examine the outer surfaces of the pericardial sac for thickness and transparency. Open the pericardial sac and note the colour, tubidity, amount and quality of pericardial fluid. Examine the pericardium and note for haemorrhages and the amount of fat in the pericardial groove. Qualify the shape of the heart and note any change in the bulk of the chambers.
 

Figure 5. Opening the Right Chambers

Grasp the heart by one hand and rotate it so that the anterior surface faces upward, with the right chamber facing the examiner. As an aid in orientation, the triangular extremity of the right auricle and the pulmonary artery would point at the direction of the examiner's right side when the heart is rotated. Cut open the right auricle starting from the site for entry of the posterior vena cava and horizontally towards the opposite extremity. Remove any clotted blood and examine the patency of the tricuspid valves and the inner surfaces of the right auricle. Position the knife inside the right ventricle. Cut the muscle close to the septum starting from the examiner's left side then downwards and into the entire length of the pulmonary  artery.  This will form a V-shaped flap of the right side of the heart. Continue opening the pulmonary artery and its branches deep in the lung parenchyma. Examine the thickness of the right chambers, the tricuspid valve and associated papillary muscles, and the endocardium.
 

Figure 6. Opening the left chamber.

Figure 7. Opening the Aorta

Figure 8. Examination of heart while still attached to the lungs, oesophagus and trachea

Examination of Other Visceral Organs

The examination of the rest of the organs still attached to the carcass follows. Examine the intact and cut surfaces of the liver and note for colour, texture, consistency, changes in the acinar patterns, abnormal masses among others. Make several slices of the liver for closer inspection. Cut open the gall bladder and note the quality and colour of bile, and the appearance of the mucosa.

Examine the adrenal glands which are located above the anterior pole of both kidneys. Cut them open longitudinally and note the relative thickness of the cortex in relation to the medulla. Carefully remove the kidneys from their attachments without severing the ureters. Grasp the kidney gently between one hand and cut it into halves longitudinally. Examine the kidneys for haemorrhages, areas of necrosis and/or infarcts, evidence of mineralisation, and compare the thickness of the cortex to that of the medulla. Trace the opening of the ureter and cut it open until it enters the urinary bladder. Puncture the urinary bladder and collect the urine and measure the volume. Cut open the urinary bladder and note for areas of haemorrhages, necrosis, presence of stones, and fibrosis.

For male animals, slice and examine the prostate and cut open the urethra up to the penis. Look for possible small calculi that usually lodge at the urethral flexure. In female animals, free the vulva and the vagina from their attachments in the pelvic cavity. Cut them open and examine.Lymph nodes are examined whenever they are encountered during dissection. In cases of suspected malignancy, it is imperative to examine the regional lymph node and look for evidence of metastases.

Examination of the Brain

The examination of the brain requires removal of the head from the rest of the carcass, and opening the calvarium. To remove the head from the rest of the carcass, severe all attachments at the atlanto-occipital joint. While doing this, take care not to unnecessarily pull the spinal cord damaging it on the process. Skin the head and remove all muscles to expose the vault of the cranium.

To open the vault of the cranium and expose the brain, a hacksaw may be used to saw off the overlying bones. Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain. If a vise is not available to hold the severed head in position, grasp firmly the head and press it against one corner of the table and carefully saw the bone slowly. Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner. A mechanic hacksaw may be used to saw off the overlying bones. Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain. If a vise is not available to hold the severed head in position, grasp firmly the head and press it against one corner of the table and carefully saw the bone slowly.
 

Figure 10. Sample skull of the dog. Arrows illustrate the lines where the cuts shall be made.

Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner. Grasp the whole head with one hand pressing the thumb against the nasopharyngeal openingAnchor the index finger on the orbital rim and support the nasal region with the rest of the fingers. Press firmly the head on one corner of the table. Carefully saw the condyloid fossa just above the occipital condyles. Continue the cut slightly oblique and forward cutting the junction of the squamous temporal and occipital bones, and up to the supraorbital process of the frontal bones. Take care when cutting the lateral part of the temporal bone since at this part the bones are relatively thin and lie close to the brain.

After completing cuts at the right side of the head, rotate the head to cut the bones at the other side. Grasp the head with the thumb anchored on the orbital rim and the index finger pressed against the nasopharyngeal opening. Support the head using the rest of the fingers grasping the nasal region. Make a similar cut until both the cuts at both side of the head meet at the median plane. Place the head on the table and hold it firmly with one hand. Make a diagonal cut continuing the cuts made at either side, and saw off about quarter thick of the head. This completes the cuts to open the calvarium.

Hold the head slightly tilted with the foramen magnum facing the examiner. To remove the sawed portion of the calvarium, pry it open by sticking the knife or a flat instrument onto the sawed portion where the occipital and temporal bones meet forming a ridge. This part of the skull is relatively thick. Twist the knife and force open the sawed bone. If the cuts made were deep enough, this should pry open the calvarium without much difficulty. Once the sawed portion is lifted and removed, cut the meninges covering the brain.

The brain is now exposed for examination. Before removing the whole brain from the cavity, examine the surface of the brain and look for evidence of oedema such as cerebellar coning and flattening of the gyri and sulci. Remove the brain by inverting the head with the palm supporting the falling brain. With the aid of a pair of scissors, cut all the cranial nerves and attachments until the whole brain drops slowly to the palm of the hand holding the head.

The whole brain is best fixed in ten-times the brain volume of 10% formalin solution overnight before examination. This will harden the brain and makes it amenable to slicing and manipulation. Detailed examination of the brain requires making serial sections no thicker than 0.5 cm. In looking for possible lesions in the brain, the idea of duplication in the appearance of both sides of the brain should be considered. Any alteration on the appearance of one side compared to that of the other side may be a suspect for possible lesion, provided that cuts were made perpendicularly. When slicing the brain, note any difference on the diameter of the ventricles and any abnormal tissue masses. Save the slices of the brain in fresh formalin solution. For routine histopathological evaluation of the brain, at least six sections are required composed of the following transverse sections:

1) Root of spinal cord
2) Mid cerebellum
3) Cerebrum at either side including  the hippocampus
4) Brain stem taken at the level of  the pons
5) Cerebral peduncle

Examination of the Spinal Cord

Clincial history of sudden and/or progressive paralysis warrants the examination of the spinal cord, nerve plexus, and associated ganglia. Remove the entire spinal column by sawing off all attachments of the ribs at either side and muscles. Cut the spine from the rest of the carcass at the articulation of the last lumbar and first sacral vertebra. Remove as much muscles as possible. Note for evidence of fracture and/or dislocations.
 

Figure 11. Diagram of the vertebra showing the sites (dorsal arches and/or splitting of the vertebra) where the cuts should be made.

 Figure 12. Illustration showing the the sawed
  segment of the spinal column by splitting
  the verterbra.

The spinal cord should be removed by opening the spinal column. Two approaches may be used to do this. First, the spinal column may be split through the aid of a saw cutting about one third of the vertebra, and second, by removal of the dorsal arches. Splitting the vertebral column enables the examination of the intervertebral discs and vertebral canal. To do this, hold the spinal column with one hand pressing it on the far end of the table. With one or three vertebral bodies extended beyond the edge of the table, carefully saw the vertebral body longitudinally. Keep the blade of the saw positioned medially to the spinous process cutting the dorsal arches and the vertebral body at one side. Complete the cuts until the whole length of the spinal column is split open adjusting the extended portion one or two vertebral bodies at a time as cuts are made.

While sawing, be careful not to damage the enclosed spinal cord. Once the spinal column is split opened, mark the specific regions (cervical, thoracic, and lumbar regions) using pins or by loosely tying pieces of twine at each division. Lift the cord by grasping the spinal meninges and severe all attachments. The second alternate method employs the removal of the dorsal arches. This may be accomplished using a chisel cutting the arch of each vertebral body. For large animals however, it may be convenient to detach first the individual vertebral bodies and saw off the dorsal arches.

The spinal cord, like the brain is best examined after fixation in 10% formalin solution. After fixation, remove the meningeal covering. Hold the cord vertically on one hand. Gently palpate the cord passing it between the thumb and the index finger. Note for pits and depressions, and difference in texture. Examine also the vertebral canal and note for narrowing of the lumen, evidence of fractures, and character of the intervertebral discs. Evidence of disc degeneration includes dryness and changes in the colour of the disc (from yellowish to greenish) with or without apparent protrusion into the spinal canal.

Examination of Bones and Joints

Bones and joints are seldom examined unless the clinical history suggests lameness. Also, by doing the examination samples of bone marrow which often reveals some clues on the haemopoeitic status of the animal could be collected for laboratory examination.

While the hip joint is probably the most accessible joint usually examined during the dissection stage, other joints may be included should the need arises. To open the stifle joint, skin the hind leg. Cut the quadriceps femoris muscle at its tendon lying on the anterior surface of the hindlimb overlying the patella. Slit the tissues at both sides of the patella and expose the distal articular surfaces of the femur and proximal part of the tibia. The almost flattened fibrous structure located between the distal articular surface of the femur and proximal surface of the tibia are the menisci and ligaments of the joint capsule. Dissect and examine these structures. Examine the articular surfaces of the bones for evidence of erosion, cracks and fissures, and the presence of osteophytes. Note also the character, colour, amount and consistency of synovial fluid including the synovial membranes. Reactive synovial membranes usually present small papillae which are best recognised by submerging the specimen in water or saline.

Following the examination of the stifle joint, remove the femur for evaluation of the bone and bone marrow. Split the bone longitudinally into halves using a hack saw. Examine the cut surface of the bone. Note the amount of compact and spongy bone material.

Examination of Eyes and Ears

The examinations of eyes and organs of hearing are seldom done unless clinical history suggests otherwise. The eyes are best examined at the first instance. Since the eyes often do not allow easy handling, it is best to have them fixed in formalin. To examine the organs of hearing, examine the middle external ears, then trace and cut open the external ear canal and note its contents. Examine the middle ear by opening the tympanic bullae and note its contents.