GU NUCS
GENERAL
FUNCTION
NML kidney function is 80% secretion and 20% filtration. Tracer choice is based on which of these parameters you want to look at.
5 indications
Differential function
Suspected obstruction
Suspected renal artery stenosis
Suspected complication from renal transplant
Suspected urine leak
Images are obtains posteriorly (anterior if patient has a transplant or horseshoe)
Typically dynamic exams have 3 phases: blood flow, cortical, clearance.
DIFFERENTIAL FUNCTION
SUSPECTED OBSTRUCTION
Standard dynamic exam w/ BF, cortical, and clearance phases; 30 min wait after clearance; challenge w Lasix if activity in collecting system.
Tracer: MAG3 (MC; better w poor renal function) or DTPA.
Interpretation
No obstruction: tracer clears from CS w/o need for Lasix or washout of 50% of tracer w/n 10 min of Lasix administration.
Intermediate: washout of 50% of tracer w/n 10-20 min of Lasix administration.
MCC for this result is a very dilated pelvis and subsequent "reservoir effect"
True obstruction: washout >20 min after Lasix
False positives
Poor response to Lasix 2/2 bad RF or dehydration at baseline
"Reservoir effect": VERY dilated renal pelvis, delaying transit time
Back pressure effects: full or neurogenic bladder can generate back pressure and prevent emptying of kidneys (resolve w foley catheter)
