1. Size
1.1. Enlarged
1.1.1. unilateral
1.1.1.1. compensatory hypertrophy
1.1.2. bilateral
1.2. Normal
1.2.1. Bilaterally symmetric. Length: cats 3.5-4.5 cm; dogs 3-10 cm depending on body weight
1.3. Small
1.4. Collecting system
1.4.1. Normal
1.4.1.1. < 2 mm of anechoic renal pelvic fluid
1.4.2. Dilation
1.4.2.1. Mild-moderate dilation of the renal pelvis (+/-) pelvic recesses without obstruction
1.4.2.1.1. pyelectasia
1.4.2.2. Moderate-severe dilation of the renal pelvis and pelvic recesses secondary to obstruction
1.4.2.2.1. hydronephrosis
1.4.3. Contents
1.4.3.1. echogenic fluid
1.4.3.1.1. pyelonephritis
1.4.3.2. hyperechoic material
1.4.3.2.1. calculi
1.4.4. Architecture
1.4.4.1. Normal
1.4.4.1.1. cortex hyperechoic to medulla
1.4.4.2. Focal/multifocal lesions
1.4.4.2.1. nodules/masses
1.4.4.3. Diffuse lesion
1.4.4.3.1. reduced corticomedullary distinction
1.4.4.3.2. hyperechoic band in outer medulla