| Yorkshire Terrier CONGENITAL ABNORMALITIES |
1. Cryptorchid: Unilateral or bilateral non-descent of the testicle into the scrotum.
2. Patellar Luxation: Dislocation of the patella (knee).
3: Dewclaws: Extra toes on either the front or hind limbs.
4. Over and Undershot jaw: Teeth aligning improperly. Should be level or scissors bite.
5. Atlantoaxial Subluxation: Spinal cord compression and trauma.
6. Hemivertebrae: Vertebral body appears to have a portion absent.
7. Collapsed Trachea: Collapse of flattening of the cervical trachea.
8. Inguinal and Umbilical Hernias: Protrusion of abdominal contents or inquinal ring.
9. Renal Cortical Hypoplasia: Bilateral underdevelopment of the kidney cortex.
10. Hyperadrencorticism: Characterized by alopecia, calcinosis, cutis, muscular wating, ployuria, polydipsia, and
increaded appetite.
11. Hydrocephalus: Accumulation of fluid in the brain.
12. Retinal Dysplasia: Retinal detachment, noticeable at 3-6 weeks of age.
13. Retinal Degeneration: Damage or malfunction of photoreceptor, bipolar, or ganglion cells, leading to partial or
total loss of vision.
14. Retained Decidous Teeth: Failure of permanent dention to repel deciduous teeth.
15. Legg-Perthes Disease: Unilateral or bilateral necrosis of the femoral head leading to a progressive lameness.
16. Dystocia: Maternal or fetal factors causing difficult or prolonged whelping.
17. Glycogen Storage Disease/Hypoglycemia: The inability to movilize glycogen which leads to clinical hypoglycemia.
18. Porto-systemic Shunt: Sbnormal communication between the portal vein and a systemic vein that shunts blood
away from the liver into the systemic circulation.
19. Distichlasis: Double Eyelashes
20. Keratoconjunctivitis Sicca: Dry eye.
21. Intestinal Lymphangectasia: An inflammation and dysfunction of the intestinal lymphatic system that causes loss of
protein, fats and lymphocytes from the body.
HEPATIC PORTO-SYSTEMIC SHUNTS
Most dogs will be diagnosed with porto-systemic shunts are under one year of age but dogs as old as eight have
been diagnosed with the condition. Animals are usually stunted, thin, depressed, have trouble gaining weight, and are
usually characterized by the owners as chronic "poor-doers". In most affected dogs there will be some degree of
behavioral signs ranging from listlessness, apathy, or depression; to more severe signs of circling, head pressing,
stupor, drooling, blindness, or convulsions, some leading to coma. These behavioral changes are due to an
accumulation of toxins (especially ammonia) that affect the brain causing a condition called Hepatic Encephalopathy.
These toxins are most abundant in the blood stream following the dog eating, especially a high protein meal, and may
remain high for hours afterward. Not all dogs with the shunt will show this meal associated behavioral change, but in
the 25% of the affected dogs that do, the diagnosis becomes clearer. A high percent of affected animals show an
intolerance to anesthetics or tranquilizers and will show increased recovery times following use of these products.
Even anticonvulsants used to control seizures may be potentially dangerous if allowed to concentrate in a dog with a
functional shunt. Approximately 75% of affected individuals will show digestive system symptoms including poor
appetite (eating paper, etc.). Urinary system symptoms may include increased thirst and urination and in a majority of
porto-systemic shunt cases, there will be crystals or stones formed in the urinary tract. These crystals will be either
uric acid or ammonium urate (ammonium biurate or thom-apple crystals). There can be bladder stones formed or
crystals may be noted on the hair around the prepuce or vulva.
Routinely performed serum chemistries are fairly non-specific toward confirming the diagnosis of porto-systemic
shunts, but there may be a decreased total protein (primarily albumin), decreased blood glucose, decreased
cholesterol, and decreased blood urea nitrogen (BUN). The uric acid levels may be elevated in a significant number
or affected individuals. Liver enzyme concentrations of ALT and ALP are elevated in 60-85% of dogs with congenital
shunts. Elevated ALP levels on animals under one year of age may be caused by normal growth processes.
Serum Ammonia Concentrations are considered by some researchers to be porto-systemic shunts. In more than 85%
of dogs with congenital portocaval shunts, an increased fasting blood ammonia concentration is sufficient to confirm
the diagnosis of a porto-systemic shunt.
Serum bile acid levels are extremely important in the diagnostic screening of symptomatic potential shunts. Fasting
and 2-hour post meal blood samples are evaluated for bile acid levels. In virtually all porto-systemic shunts there will
be a significant rise in the bile acid levels over normal.
Liver function testing with Bromosulfaphthalein (BSP) or Ammonia Tolerance testing are sensitive and reliable if
performed correctly. These tests measure the liver's ability to excrete or detoxify known agents and thus measure
liver function accurately.
Radiography is one of the most important methods of establishing a diagnosis of proto-systemic shunt and is currently
the only univerally accepted nethod of confirming a shunt, short of major surgery. Injection of a radiopaque dye into
either the spleen (Splenoportography) or a blood vessel from the intestine (Jejunal vein portography) will show the
shunt on radiographs and allow accurate assessment for surgical correction.
The placement of a radiopharmaceutical agent (radioisotope) specific for the liver into the colon for absorption
through the mucosa has been gaining favor because of it's non-invasive diagnostic value. This procedure requires
very specialized equipment and the diagnosis is based on the distribution of the radionuclide in the lung or heart
compared to that in the liver. The radiosotope would be concentrated in the liver of a normal dog. This procedure
does not identify the exact location of the shunt for surgical correction if required.
Until recently ultrasound was fairly unreliable for non-surgical diagnosis of porto-systemic shunts. With the advent of
Color Flow Ultasound, there is the potential for diagnosis of this condition on non-anesthetized animal. At the current
time this technology appears to be the diagnostic procedure of choice. Research has confirmed the value and
accuracy of Color-flow Doppler Ultrasound. When used by experienced operators, this is the preferred screening and
diagnostic tool for porto-systemic shunts in all breeds of dogs.
At the present time Hepatic Porto-systemic Shunts are considered to be unquestionably genetic by some of the
leading canine geneticists in the United States. The exact mode of heredity has not been identified at the present time
but research is being conducted at Michigan State Unviersity to identify this pattern.
Genetic disorders in dogs can spread relatively rapidly if a dog, whetyer affected or a carrier, is a well respected
animal either in conformation or ability and is used extensively for breeding. This is especially true in the case of the
male that can produce hundreds of offspring during his breeding life. If the cause of such a condition can be
discovered then working strategies can be implemented to control and eliminate the disorder.
The YTCA Foundation, Inc. is currently funding research into the genetic nature of the problem. This step will
hopefully become the basis for setting up an open registry for Yorkshire Terriers and other affected breeds to
hopefully eliminate or atleast minimize the problem within each breed
2. Patellar Luxation: Dislocation of the patella (knee).
3: Dewclaws: Extra toes on either the front or hind limbs.
4. Over and Undershot jaw: Teeth aligning improperly. Should be level or scissors bite.
5. Atlantoaxial Subluxation: Spinal cord compression and trauma.
6. Hemivertebrae: Vertebral body appears to have a portion absent.
7. Collapsed Trachea: Collapse of flattening of the cervical trachea.
8. Inguinal and Umbilical Hernias: Protrusion of abdominal contents or inquinal ring.
9. Renal Cortical Hypoplasia: Bilateral underdevelopment of the kidney cortex.
10. Hyperadrencorticism: Characterized by alopecia, calcinosis, cutis, muscular wating, ployuria, polydipsia, and
increaded appetite.
11. Hydrocephalus: Accumulation of fluid in the brain.
12. Retinal Dysplasia: Retinal detachment, noticeable at 3-6 weeks of age.
13. Retinal Degeneration: Damage or malfunction of photoreceptor, bipolar, or ganglion cells, leading to partial or
total loss of vision.
14. Retained Decidous Teeth: Failure of permanent dention to repel deciduous teeth.
15. Legg-Perthes Disease: Unilateral or bilateral necrosis of the femoral head leading to a progressive lameness.
16. Dystocia: Maternal or fetal factors causing difficult or prolonged whelping.
17. Glycogen Storage Disease/Hypoglycemia: The inability to movilize glycogen which leads to clinical hypoglycemia.
18. Porto-systemic Shunt: Sbnormal communication between the portal vein and a systemic vein that shunts blood
away from the liver into the systemic circulation.
19. Distichlasis: Double Eyelashes
20. Keratoconjunctivitis Sicca: Dry eye.
21. Intestinal Lymphangectasia: An inflammation and dysfunction of the intestinal lymphatic system that causes loss of
protein, fats and lymphocytes from the body.
HEPATIC PORTO-SYSTEMIC SHUNTS
Most dogs will be diagnosed with porto-systemic shunts are under one year of age but dogs as old as eight have
been diagnosed with the condition. Animals are usually stunted, thin, depressed, have trouble gaining weight, and are
usually characterized by the owners as chronic "poor-doers". In most affected dogs there will be some degree of
behavioral signs ranging from listlessness, apathy, or depression; to more severe signs of circling, head pressing,
stupor, drooling, blindness, or convulsions, some leading to coma. These behavioral changes are due to an
accumulation of toxins (especially ammonia) that affect the brain causing a condition called Hepatic Encephalopathy.
These toxins are most abundant in the blood stream following the dog eating, especially a high protein meal, and may
remain high for hours afterward. Not all dogs with the shunt will show this meal associated behavioral change, but in
the 25% of the affected dogs that do, the diagnosis becomes clearer. A high percent of affected animals show an
intolerance to anesthetics or tranquilizers and will show increased recovery times following use of these products.
Even anticonvulsants used to control seizures may be potentially dangerous if allowed to concentrate in a dog with a
functional shunt. Approximately 75% of affected individuals will show digestive system symptoms including poor
appetite (eating paper, etc.). Urinary system symptoms may include increased thirst and urination and in a majority of
porto-systemic shunt cases, there will be crystals or stones formed in the urinary tract. These crystals will be either
uric acid or ammonium urate (ammonium biurate or thom-apple crystals). There can be bladder stones formed or
crystals may be noted on the hair around the prepuce or vulva.
Routinely performed serum chemistries are fairly non-specific toward confirming the diagnosis of porto-systemic
shunts, but there may be a decreased total protein (primarily albumin), decreased blood glucose, decreased
cholesterol, and decreased blood urea nitrogen (BUN). The uric acid levels may be elevated in a significant number
or affected individuals. Liver enzyme concentrations of ALT and ALP are elevated in 60-85% of dogs with congenital
shunts. Elevated ALP levels on animals under one year of age may be caused by normal growth processes.
Serum Ammonia Concentrations are considered by some researchers to be porto-systemic shunts. In more than 85%
of dogs with congenital portocaval shunts, an increased fasting blood ammonia concentration is sufficient to confirm
the diagnosis of a porto-systemic shunt.
Serum bile acid levels are extremely important in the diagnostic screening of symptomatic potential shunts. Fasting
and 2-hour post meal blood samples are evaluated for bile acid levels. In virtually all porto-systemic shunts there will
be a significant rise in the bile acid levels over normal.
Liver function testing with Bromosulfaphthalein (BSP) or Ammonia Tolerance testing are sensitive and reliable if
performed correctly. These tests measure the liver's ability to excrete or detoxify known agents and thus measure
liver function accurately.
Radiography is one of the most important methods of establishing a diagnosis of proto-systemic shunt and is currently
the only univerally accepted nethod of confirming a shunt, short of major surgery. Injection of a radiopaque dye into
either the spleen (Splenoportography) or a blood vessel from the intestine (Jejunal vein portography) will show the
shunt on radiographs and allow accurate assessment for surgical correction.
The placement of a radiopharmaceutical agent (radioisotope) specific for the liver into the colon for absorption
through the mucosa has been gaining favor because of it's non-invasive diagnostic value. This procedure requires
very specialized equipment and the diagnosis is based on the distribution of the radionuclide in the lung or heart
compared to that in the liver. The radiosotope would be concentrated in the liver of a normal dog. This procedure
does not identify the exact location of the shunt for surgical correction if required.
Until recently ultrasound was fairly unreliable for non-surgical diagnosis of porto-systemic shunts. With the advent of
Color Flow Ultasound, there is the potential for diagnosis of this condition on non-anesthetized animal. At the current
time this technology appears to be the diagnostic procedure of choice. Research has confirmed the value and
accuracy of Color-flow Doppler Ultrasound. When used by experienced operators, this is the preferred screening and
diagnostic tool for porto-systemic shunts in all breeds of dogs.
At the present time Hepatic Porto-systemic Shunts are considered to be unquestionably genetic by some of the
leading canine geneticists in the United States. The exact mode of heredity has not been identified at the present time
but research is being conducted at Michigan State Unviersity to identify this pattern.
Genetic disorders in dogs can spread relatively rapidly if a dog, whetyer affected or a carrier, is a well respected
animal either in conformation or ability and is used extensively for breeding. This is especially true in the case of the
male that can produce hundreds of offspring during his breeding life. If the cause of such a condition can be
discovered then working strategies can be implemented to control and eliminate the disorder.
The YTCA Foundation, Inc. is currently funding research into the genetic nature of the problem. This step will
hopefully become the basis for setting up an open registry for Yorkshire Terriers and other affected breeds to
hopefully eliminate or atleast minimize the problem within each breed
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