Issue Description Fanconi syndrome is a disorder in which the
proximal renal tubules of the kidney do not properly reabsorb
electrolytes and nutrients back into the body, but instead "spill"
them in the urine. Symptoms include excessive drinking (polydipsia),
excessive urination (polyuria), and glucose in the urine (glucosuria.)
If Fanconi is left untreated, muscle wasting, acidosis, and poor
condition will also occur.
Causes Fanconi's syndrome appears to have a hereditary
predisposition for Basenjis as well as Norwegian Elkhounds. Other
breeds that are predisposed (to a lesser degree) are Shetland
sheepdogs and Schnauzers. The onset of the disease is not until later
in life (3-11 yrs of age in Basenjis), and thus affected dogs may have
been bred before diagnosis, passing on the genetic trait.
Approximately 10% of adult Basenjis have Fanconi's syndrome. The
acquired form of Fanconi's syndrome can be caused by heavy metal
poisoning (lead, mercury, cadmium and uranium). Drugs such as a
gentamicin, cephalosporins, outdated tetracycline, cisplatin, and
streptozotocin can cause proximal renal tubule resorption
abnormalities. Chemicals such as Lysol® and maleic acid also have
been reported to cause the syndrome. Renal cystic disease and
neoplasia, including multiple myeloma and monoclonal gammopathies,
also have been found to cause acquired Fanconi's syndrome.
Fanconi's syndrome is a progressive disease, which, if not treated,
ultimately results in transport system failure to the point where
solute losses are significant enough to overwhelm other compensatory
mechanisms and the dog can no longer maintain homeostasis. The most
significant of these is the loss of bicarbonate (HCO3-). Proximal
renal tubular acidosis subsequently develops and, if left uncorrected,
will ultimately lead to death. In an unaffected dog with a normal
acid-base balance, most of bicarbonate ions in the urine are converted
to carbonic acid (HCO3- + H+� H2CO3), which is then converted to H2O
and CO2 with the aid of carbonic anhydrase found in the brush border
of the renal tubular epithelial cell. The carbon dioxide formed
readily diffuses across the luminal membrane of the renal tubular
cell. In this way, bicarbonate is conserved. The hydrogen ion needed
to form carbonic acid is supplied by the sodium-hydrogen ion
antiporter, which has a high enough Tm to conserve the needed
bicarbonate in an unaffected dog. In Fanconi's syndrome, the Tm is
reduced due to either the lack of a sufficient sodium concentration
gradient or a defect in the transporter itself. As a result, fewer
hydrogen ions are secreted and, thus, less bicarbonate is conserved.
The loss of bicarbonate causes an acidemia and the plasma bicarbonate
level decreases until it has reached a level which the impaired
transport system can handle. Affected dogs can compensate somewhat for
the acidemia through respiratory mechanisms (hyperventilation), shifts
in intracellular potassium, and secreting hydrogen ions in the distal
Symptoms A dog suffering from Fanconi's syndrome
typically presents with polyuria and polydypsia, a history of weight
loss, a poor hair coat and, sometimes weakness.
Diagnosis Glucose (sugar), and other nutrients and
buffers spill into the dog's urine from the faltering renal tubule
system of the kidneys; however, the dog will be found to have a normal
to low BLOOD glucose. This condition may be mistaken for diabetes and
disastrously mistreated. Blood glucose would be HIGH in diabetes.
A dog's urine can easily and inexpensively be checked for glucose with
glucose test strips found at any drugstore in the diabetic supplies
section. This form of testing can pick up oncoming Fanconi Syndrome
well before any of the overt symptoms appear. Overt symptoms are:
frequent urination, excessive water-drinking, and loss of weight and
condition. Early detection means easier treatment and less permanent
Glucose test stripping at one-month intervals is
highly recommended for Basenjis of any age, and for a dog of any breed
suspected of having Fanconi Syndrome. Simply hold the glucose testing
stick (or diabetic test tape) under the dog's urine, remove, and wait
the appropriate amount of seconds. Report any abnormalities in color
to your veterinarian and have him do a blood glucose test. If the dog
is spilling glucose in the urine and the blood glucose test reading is
normal to low, a presumptive diagnosis of Fanconi Syndrome may be
made. A subsequent venous blood gas analysis should confirm this
diagnosis and tell you the status of the disease process.
Treatment Approximately every six to eight months, a
multivalent blood workup, a urinalysis, and a venous blood gas test
need to be done on a Fanconi-afflicted dog by your veterinarian. Based
on the dog's individual tests, appropriate, individually-tailored, and
easily-obtainable nutrients are included with the dog's daily meals.
These oral supplements resupply the nutrients which the tests identify
as being lost in the urine.
Prognosis The outlook is exceptionally good with early
detection and treatment. This condition can now be controlled but not