Page 452 - Feline diagnostic imaging

464 27 Urinary Disease

(a) (b)

(c)
(d)

Figure 27.13 Ultrasonography of renal neoplasia. The appearance of a neoplastic kidney varies from complete loss of architecture to
a kidney that looks relatively normal. Carcinoma tends to be unilateral and causes more destruction of tissue whereas lymphoma
tends to be bilateral and affected kidneys usually have a more normal shape and architecture. The appearance is not diagnostic,
however. (a) Ultrasound image of the left kidney of a 12-year-old domestic shorthair. The kidney is enlarged and hyperechoic but has a
relatively normal shape and architecture. (b) Ultrasound image of the right kidney of the same cat. This kidney is greatly enlarged,
measuring 6.25 × 7.65 cm. (c) Ultrasound-guided fine needle aspiration can be helpful in determining the type of neoplasia. Aspirates
from the small mass (1.64 × 1.83 cm) in the kidney of this 10-year-old domestic shorthair revealed large cell lymphoma with high
mitotic activity. (d) Renal neoplasia can also be the result of metastasis, as is seen in this image of the kidney of a 9-year-old
domestic shorthair admitted with neoplasia involving the left hindlimb. The kidney shows a loss of architecture with hypoechoic
areas distorting the shape of the kidney. Fine needle aspiration of the kidneys, limb mass, and medial iliac lymph nodes suggested
plasmacytoma as the most likely differential.

the mass. Differentials for a large retroperitoneal mass in The kidneys are usually enlarged with an irregular shape
the area of a kidney include neoplasia, severe hydrone- and increased echogenicity. Hypoechoic subcapsular
phrosis, polycystic renal disease, and perirenal pseudo- thickening is most likely to occur in cats with renal lym-
cyst (see below). Rarely, a mass is found to be within the phosarcoma and most cats that exhibit this finding are
adrenal gland rather than the kidney. Excretory urogra- found to have lymphosarcoma [13]. The thickening is
phy and ultrasonography can confirm the involvement of crescent shaped in most cases but can appear as a hypo-
the kidney and can be useful in further characterizing echoic rim in others (Figure 27.14c,d). Fine needle aspira-
the mass. The renal pelvis may be distorted, enlarged, or tion with cytologic evaluation of a kidney infiltrated with
unaffected. On ultrasonography, the renal architecture lymphosarcoma typically will provide a definitive diagno-
may be relatively normal or almost unrecognizable sis. The absence of distal acoustic enhancement helps dif-
(Figure 27.13). ferentiate soft tissue thickening from subcapsular fluid.
Lymphosarcoma is the most common renal neoplasm Transitional cell carcinoma rarely occurs in the kidney
(Figures 27.13c and 27.14), with adenocarcinoma also but can occur bilaterally as a primary neoplasm or as the
being common. Lymphosarcoma is frequently bilateral. result of metastasis [14]. Metastasis can also occur in the