The patient underwent a left pyeloplasty, and has been asymptomatic since. Discussion Urinary tract obstruction is a very common problem that, if untreated, may lead to progressive renal damage. Acute obstruction is diagnosed clinically and by radiological techniques. Uptake of radioactive tracer varies from no uptake at all to normal uptake depending on the pressure build-up in the obstructed collecting system and time. Radionuclide function measurements have limited prognostic value in acute obstruction.
Chronic obstruction leads to the compromise of renal function.
The flow, uptake, and excretion of tracers accurately reflect the functional status of each kidney and are used to follow the renal function after therapeutic interventions. Whitaker test, though not dependent on renal function, is invasive and provides no information about the functional status of the kidneys. Tubular agents are preferred and currently Tc99m MAG - 3 is widely used for its high extraction fraction, rapid parenchymal transit, low radiation absorbed dose and excellent imaging properties. Differential function is calculated from the 1-2 min interval data with tubular agents. The literature is replete with attempts to refine and quantify response patterns.