Normal differential renal function does not indicate a normal kidney after partial ureteropelvic obstruction and subsequent relief in 2-week-old piglets

The features of technetium-99m-DTPA renal dynamic imaging after severe unilateral ureteral obstruction in adult rabbits

Background

It is controversial to evaluate the function of hydronephrotic kidneys by renal dynamic imaging (RDI). Our aim was to study the features of renal dynamic imaging (RDI) at different stages after unilateral ureteral obstruction (UUO) and to investigate a method that could be reasonably used to evaluate renal function and predict renal functional recoverability.

Methods

We made UUO models using fifteen adult New Zealand white rabbits and systematically observed the changes in kidney morphology, blood flow, radiotracer distribution and function by RDI. We then compared the differences in terms of imaging features between different periods and analyzed the relationship between blood flow and function in obstructed kidneys.

Results

1) Obstructed kidneys gradually became larger than preoperative kidneys and contralateral kidneys (P<0.05) and reached their peak size between days 42 and 56, after which they gradually got smaller in size. 2)The correlation between the blood perfusion of the obstructed kidney and the obstruction duration (r = 0.125, P = 0.045) was very weak. In the initial period of obstruction, the perfusion of the obstructed kidney significantly decreased, followed by a sharp rebound in later days, and then the perfusion declined again. The peak in blood perfusion was on day 7. 3) The uptake rate of the obstructed kidney drastically decreased in the early stage and became lower than that of the contralateral kidney and the kidney before the operation (P<0.05), after which uptake increased gradually; the peak was on day 28. After that, uptake gradually decreased. 4) The grading of the radiotracer distribution in obstructed kidneys was positively correlated with the obstruction duration (r = 0.975, P = 0.000), and a uniform renal distribution was an early feature of obstruction. 5) The blood perfusion of the obstructed kidney and its functioning frequently increased or decreased simultaneously, but sometimes there was also a mismatch. The peak of renal blood perfusion recovery occurred prior to the peak of renal function recovery.

Conclusion

In different periods of severe UUO, the imaged features of obstructed kidneys were different. These features are beneficial for determining the degree of hydronephrosis and renal function and predicting renal functional recoverability.

Does baseline renal function always decrease after unilateral ureteral severe obstruction? -experimental validation and novel findings by Tc-99m diethylene triamine pentaacetate acid (DTPA) dynamic renal scintigraphy

Background

There is a lack of consensus concerning changes in renal function after unilateral ureteral obstruction. The aim of this study was to assess the influence of ureteral obstruction on renal morphology and function and to explore the effectiveness of dynamic renal scintigraphy in evaluating obstructive renal function.

Methods

We established a model of right ureteral obstruction using New Zealand white rabbits. We measured the glomerular filtration rate (GFR) before the operation and from days 1 to 82 after obstruction, observed the changes in bilateral kidney sizes and the GFR, and then compared the differences between the left and right kidneys.

Results

The difference between left and right kidney sizes was not significant before obstruction (t=-0.430, P=0.674); the right kidneys increased in size after obstruction and were larger than the left kidneys (P≤0.001). Obstructed kidneys demonstrated a morphological process of decelerated expansion and retraction. The difference in GFR between the left and right kidneys was not significant before obstruction (t=1.77, P=0.098); during days 1-21 and 42-82 after obstruction, the GFR of the right kidneys decreased and was lower than that of the left kidneys (P<0.001); on day 28, the GFR difference between the left and right kidneys (t=1.62, P=0.130) and the difference in the right kidney GFR before and after obstruction (t=1.03, P=0.323) were not significant. The GFR of obstructed kidneys rapidly declined initially, experienced a tortuous process of repeated dormancies and multiple self-recoveries, and then gradually declined.

Conclusions

The GFR in hydronephrotic kidneys is fluctuating. Thus, evaluating the true function of hydronephrotic kidneys using only baseline GFR is difficult; however, combining baseline GFR with renal morphology to assess obstructive renal function and its recoverability can provide more meaningful results.