Clinical Significance of Renal Pelvic Dilatation on Ultrasound in Dogs and Cats

Abstract

Renal pelvic dilatation is often recognized sonographically in dogs and cats, but ranges of measurements expected with different urologic conditions remain unknown. Ultrasound images of 81 dogs and 66 cats with renal pelvic dilatation were reviewed, and six groups were formed based on medical records: (I) clinically normal renal function, and (II) clinically normal renal function with diuresis; (III) pyelonephritis; (IV) noninfectious renal insufficiency; (V) outflow obstruction; (VI) miscellaneous nonobstructive anomalies. Medians for maximal pelvic width (range) for group I was 2.0 mm (1.0-3.8) in 11 dogs, and 1.6 mm (0.8-3.2) in 10 cats; for group II, 2.5 mm (1.3-3.6) in 15 dogs, and 2.3 mm (1.1-3.4) in 16 cats; for group III, 3.6 mm (1.9-12.0) in nine dogs, and 4.0 mm (1.7-12.4) in seven cats; for group IV, 3.1 mm (0.5-10.8) in 33 dogs, and 2.8 mm (1.2-7.3) in 13 cats; for group V, 15.1 mm (5.1-76.2) in six dogs, and 6.8 mm (1.2-39.1) in 17 cats; and for group VI, 3.8 mm (1.2-7.6) in seven dogs, and 3.0 mm (1.3-7.5) in three cats. Pelvic width in group I was lower than in groups III-V (P ¼ 0.0001), but did not significantly differ from group II. Pelvic width !13 mm always indicated obstruction. While the proportion of bilateral pelvic dilatation was not different among groups, the difference in pelvic width (maximal-minimal) was greater in group V vs. groups I, II, and IV (P ¼ 0.0009). These results confirm that renal pelvic dilatation can be detected sonographically in dogs and cats with clinically normal renal function, and that it increases with renal insufficiency, pyelonephritis, or outflow obstruction. Nevertheless, renal pelvic width varies substantially within groups and should be interpreted with caution. r

ACVIMSmall Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats

“…Many <7 mm also were associated with ureteral obstruction. The cause of ureteral obstruction was not documented by ultrasonography alone in up to 25% of cats, which necessitated concurrent radiographic imaging and ureteropyelography …”

Urinary Tract

“…2,14,23,24,73,85 Mild, unilateral pelvic dilation has been observed with saline diuresis or secondary to increased urine flow when the contralateral kidney was badly diseased or missing. However, current high-resolution ultrasound equipment allows visualization of mild pelvic dilation during diuresis in normal animals (pyelectasia).…”

“…However, current high-resolution ultrasound equipment allows visualization of mild pelvic dilation during diuresis in normal animals (pyelectasia). 85 The differential diagnosis for renal pelvic dilation includes congenital disease, pyelonephritis, obstruction to urine flow, 2,14,23,24,73,85 Mild, unilateral pelvic dilation has been observed with saline diuresis or secondary to increased urine flow when the contralateral kidney was badly diseased or missing.…”

Pyelonephritis in Dogs: Retrospective Study of 47 Histologically Diagnosed Cases (2005–2015)

“…The most common findings were pyelectasia, hydroureter, and hydronephrosis. These findings are not specific for pyelonephritis and can be related to neoplasia of the urogenital tract, ectopic ureter, obstructive urolithiasis, CKD, prior administration of IV fluids or diuretics . Care should be taken not to overdiagnose pyelonephritis based on such features.…”