Page 957 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

932 CHAPTER 7

VetBooks.ir 7.14

Fig. 7.14 Enlarged kidney in a stallion (Arab)
with AKI. The sagittal length of this kidney is
19 cm (7.5 in.). The normal length of the kidney
is comparable to the length of 2.5–3 vertebrae,
which in this case should be approximately
12 cm (4.7 in.).
with AKI. It is important to define ‘true’ hypo- 7.15
calcaemia, which is a decrease in ionised calcium.
A reduction in total serum calcium can result from
a decrease in albumin secondary to a protein- losing
pathological event. Alkalosis decreases ionised
calcium, whereas acidaemia is protective. This is
important when considering rapid correction of aci-
dosis due to AKI or primary disease associated with
AKI. The excretion of phosphorous within urine
in AKI is also disrupted, causing an increase in its
serum concentration. Diagnostic samples should be
collected prior to fluid therapy if possible.

Urinalysis
Urinalysis is essential for differentiation of pre-renal Fig. 7.15 Transabdominal ultrasonogram of the
from renal failure and for characterisation of the right kidney in a horse with suspected CKD. Note the
renal failure. With pre-renal failure, urine should dilation of the renal pelvis (arrow). Hydronephrosis is
be concentrated (SG >1.018), while isosthenuria present on the dorsomedial part of the kidney.
(SG 1.008–1.012) will be present with renal fail-
ure. Mild to moderate proteinuria may be present,
depending on the aetiology and severity. If glomeru- be evident. Dilation of the renal pelvis may be evi-
lar or tubular damage is present, changes to urine dent with urinary outflow obstruction (Fig. 7.15).
sediment such as the presence of casts and increased Renal biopsy has limited diagnostic value. Urinary
numbers of erythrocytes and leucocytes occur. The tract endoscopy may be useful if obstructive urinary
presence of glucosuria without hyperglycaemia is tract disease is suspected.
strong evidence of renal tubular damage. A urinary
GGT:urinary creatinine ratio of >25 is suggestive of Management
renal tubular disease although it is not highly spe- The primary disease should be managed accordingly.
cific. Fractional clearance of sodium and the urine It is important to rule out urinary tract obstruction,
creatinine:serum creatinine ratio can sometimes be especially in patients who present with oliguria or
helpful. anuria. This is achieved by bladder catheterisation.
Renal enlargement, perirenal oedema and loss Nephrotoxic drugs should be discontinued or, if
of detail at the corticomedullary junction may treatment is necessary, the dosing regime formu-
be evident ultrasonographically. Nephroliths may lated at the minimal possible effective dose.