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What is the location and size of normal kidneys on radiographs?
- Location: retroperitoneal, right more cranial than left (esp in dogs)
- Size in dogs: 2.5-3.5 x length of L2
- Size in cats: 2-3x length of L2
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The size of the kidneys can only be accurately evaluated on...
VD view!
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Describe normal margination of small animal kidneys and why the margins are seen.
- should have smooth margins in dogs and cats
- margins are seen due to contrast with retroperitoneal fat
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What are causes of lack of visualization of the kidney(s)? (4)
- border effacement/ superimposition with GI structures
- retroperitoneal effusion or lack of retroperitoneal fat
- surgical removal of a kidney
- renal aplasia or agenesis
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What are general indications of excretory urogram (intravenous pyelogram)?
- better evaluation of the kidneys (increases contrast with surrounding tissues)- structural change s (cysts, masses, nephroliths, hematoma), qulitative assessment of renal function
- evaluate ureters (not normally seen)- ureteroliths, structures, tears, ectopic ureters
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If an animal is azotemic, how do you alter your IV dose of iodinated contrast for excretory urogram?
increase dose
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Why might you perform a concurrent negative contrast cystogram with an excretory urogram?
to better visualize the uretero-vesicular junction, dx ectopic ureters
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What are contraindications for excretory urogram? (2)
- dehydration (rehydrate first)
- previous reaction to contrast
- [note: AZOTEMIA IS NOT A CONTRAINDICATION]
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What are potential complications with excretory urogram? (4)
- contrast induced renal failure has been reported, usually reversible with diuresis
- anaphylactic reaction
- nausea/ vomiting
- IV contrast may cause transient CV changes
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Why should you obtain a urine sample and perform a UA before performing an excretory urogram? (2)
- iodinated contrast limits bacterial growth (possible false neg culture)
- iodinated contrast can affect the specific gravity
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Describe the vascular phase of an excretory urogram. (2)
- occurs immediately post-injection of contrast
- allows you to identify the renal artery(ies) supplying the kidney
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Describe the nephrogram phase of an excretory urogram. (3)
- occurs immediately post-injection of contrast
- parenchyma most opaque ~10-30s pst-injection
- can eval tubules and vascular supply
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Describe the pyelogram phase of an excretory urogram. (3)
- occurs 1-2 minutes after the injection
- can eval pelvis, renal diverticula, ureters
- ureters are intermittently opacified
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How wide should the renal pelvis and ureters be on an excretory urogram?
- Pelvis= 1-2mm wide
- Ureters= 2-3mm wide
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How do normal ureters appear at their insertion to the bladder?
"J" hook at the trigone
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What are causes of renomegaly? (7)
- neoplasia (smooth or irregular margins)
- hematoma (usually unilateral)
- perinephric pseudocysts (smooth margins, CATS)
- nephritis/ pyelonephritis
- hydronephrosis (smooth margins)
- hypertrophy
- chronic renal disease (BKLK) (smooth or irregular margins)
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What are potential causes of small kidney(s)? (2)
- chronic renal disease (smooth or irregular margins)
- renal hypoplasia
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Describe the appearance an clinical aspects of perinephric pseudocysts. (4)
- enlarged kidneys
- smooth margins
- CATS ONLY
- other DDx- nephritis, hydronephrosis, infiltrative neoplasia
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What are causes of a change in shape of the kidney(s)?
chronic infarcts
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What are potential causes of renal pelvic dilation? (3)
- obstruction (ureteroliths)
- diuresis
- pyelonephritis
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What are potential causes of an increase in opacity of the kidney(s)? (3)
- nephrolith(s)
- dystrophic mineralization of parenchyma
- mineralization of cyst, tumor, granuloma, hematoma
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What are potential causes of a decrease in opacity of the kidney(s)? (2)
- vesico-ureteral reflux after negative contrast cystogram
- taruma
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What are radiographic aspects of pyelonephritis? (3)
- pelvic dilation
- proximal ureteral dilation
- blunted pelvic recesses
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What are radiographic aspects of hydronephrosis? (5)
- pelvic dilation
- dilation of pelvic recesses (right)
- pelvic recesses not seen (left)
- ureteral dilation
- if severe, renomegaly
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What are radiographic aspects of renal neoplasia? (3)
- mass effect in caudal pole
- distortion of renal pelvis
- other DDx- renal cyst
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What are causes of renal pelvic filling defects on urogram? (3)
- blood clot
- calculi (remember:calculi will appear radiolucent when surrounded by positive contrast)
- neoplasia
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What are causes of diffuse ureteral enlargement? (3)
- obstructive hydroureter
- atony secondary to inflammation
- unilateral- ectopic ureter
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What are causes of a focal ureteral enlargement? (1)
ureteroceole (congenital defect- ureter balloons distally before it enters bladder)
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How might an ectopic ureter appear on excretory urogram?
- abnormal accumulation of positive contrast in the vagina
- hydroureter
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What are the subsets of ureteral luminal filling defects and causes of each? (3)
- intraluminal (contrast going around defect): calculi, gas bubble, blood clot
- intramural (irregular wall margin): neoplasia, inflammation, granuloma
- extraluminal-extramural (external compression): stricture, external mass
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