Improvement of the reversible unilateral ureteral obstruction model

Abstract

The reversible unilateral ureteral obstruction (RUUO) model is pivotal for studying obstructive nephropathy (ON) but has limitations, including procedure complexity and inconsistent recanalization success. We developed a simpler, reliable, and efficient RUUO model, and utilized advanced auxiliary examination methods to assess hydronephrosis and renal function changes, providing evidence for procedural success. Male Sprague-Dawley rats were divided into control and experimental groups. Baseline data on glomerular filtration rate (GFR) and magnetic resonance imaging (MRI) were obtained from the control group. The experimental group was subdivided based on obstruction durations of 3, 7, 10, and 14 days. Unilateral ureteral obstruction models were created followed by obstruction release to establish the RUUO models. Dynamic renal scintigraphy with single-photon emission computed tomography was used to measure left kidney GFR pre-recanalization and on day 7 and 14 post-recanalization. MRI was used to evaluate hydronephrosis resolution. Key surgical modifications included complete removal of ligated ureter segments and wider ureter-bladder anastomosis, improving consistency and 93.35% recanalization success rate. MRI and ^99mTc-DTPA dynamic renal scintigraphy indicated varying degrees of renal functional recovery. The 3-day obstruction group showed near-complete restoration within 1 week of recanalization. Conversely, extended obstruction durations significantly impaired recovery. The 14-day group demonstrated marked functional decline due to progressive renal fibrosis observed at 2 weeks post-recanalization. The optimized model offers simplified surgical techniques, enhanced recanalization success, and high reproducibility. These findings highlight the importance of early recanalization in preserving renal function, and provide a robust framework for future research on ON, including therapeutic strategies.

Keywords: Dynamic renal scintigraphy; MRI; glomerular filtration rate; hydronephrosis; obstructive nephropathy; reversible unilateral ureteral obstruction model.

Figure 1.

Scheme of the experimental imaging protocol used in this study.

Figure 2.

UUO surgery pictures. (A) Normal left ureter (indicated by the arrow). (B) Incising the surface peritoneum along the distal end of the ureter. (C–E) Dissecting the distal ureter outside the ureteral sheath. (F–G) Passing 4-0 silk suture beneath the ureter and tying a knot. (H–I) Trimming the excess suture tails with micro scissors to complete the ureteral ligation.

Figure 3.

UUO-schematic diagram. (A) Incising the abdominal muscle along the linea alba, creating an approximately 3.5 cm incision to expose the left ureter. (B) Dissecting the distal segment of the ureter outside the ureteral sheath. (C–D) Passing a 4-0 silk suture beneath the ureter and tying a knot. (E–F) Trimming the excess suture tails to complete the ligation of the left ureter.

Figure 4.

RUUO surgery pictures. (A) Dilated ureter post-obstruction (indicated by the arrow). (B) Releasing the ureter and trimming surrounding adipose tissue. (C) Incising the left wall at the base of the bladder. (D) Cutting the dilated ureter at the black ligation knot. (E) Inserting the first suture through the bladder incision as a fixation point (indicated by the arrow) while leaving approximately 5 cm of suture tail. (F) Performing end-to-end anastomosis of the ureter and the anterior bladder wall. (G) Using the 5 cm suture tail to rotate the bladder. (H) Performing end-to-end anastomosis of the ureter and the posterior bladder wall. (I) Using the 5 cm suture tail again to rotate the bladder back to its physiological position.

Figure 5.

RUUO-schematic diagram. (A) Incising the abdominal muscle along the linea alba, creating an approximately 3.5 cm incision to expose the dilated left ureter. (B) Separating the ureter and trimming the surrounding adipose tissue. (C) Incising the left wall at the base of the bladder. (D) Cutting the ligated segment of the left ureter. (E) Inserting the first suture at the left side of the bladder incision as a fixation point, leaving approximately 5 cm of suture tail. (F) Performing end-to-end anastomosis of the ureter to the anterior bladder wall. (G) Using the 5 cm suture tail to rotate the ureter-bladder anastomosis site. (H) Performing end-to-end anastomosis of the ureter to the posterior bladder wall. (I) Using the 5 cm suture tail again to rotate the bladder back to its physiological position.

Figure 6.

SPECT-procedure for renal function assessment.

Figure 7.

RUUO surgical model specimen.

Figure 8.

Changes in hydronephrosis after obstruction and recanalization. Renal pelvic dilation increased proportionally with the duration of obstruction. After 7 days of recanalization, renal pelvis dilation and hydronephrosis relief varies according to the initial obstruction duration. The 3-day obstruction group showed the quickest recovery, while the 14-day group exhibited the lowest. By Day 14 post-recanalization, all groups demonstrated significant improvement in hydronephrosis and renal pelvis recovery. These findings highlight the efficacy of the modified recanalization model in alleviating hydronephrosis.

Figure 9.

Changes in dynamic renal scintigraphy after obstruction and recanalization. As shown in the figure, the ROI activity in the left kidney decreased with the duration of obstruction. By Day 7 post-recanalization, ROI activity in all groups significantly increased compared with baseline, with the 3-day and 7-day groups showing the most pronounced improvement. By Day 14 post-recanalization, ROI activity was high in all groups except the 14-day group, where it remained low.

Figure 10.

Changes of glomerular rate before and after the release of the obstruction. (A) Left kidney GFR was 46.56 (41.10, 59.88) ml/min; right kidney GFR was 49.21 (43.38, 57.60) ml/min; total kidney GFR was 96.23 (83.01, 121.8) ml/min. (B) Changes in left kidney GFR between UUO3, RUUO7, and RUUO14 were statistically significant (p < 0.01). (C) Changes in left kidney GFR between UUO7, RUUO7, and RUUO14 were statistically significant (p < 0.05). (D) Changes in left kidney GFR between UUO10, RUUO7, and RUUO14 were statistically significant (p < 0.01). (E) Changes in left kidney GFR between UUO14 and RUUO14 were not statistically significant (p > 0.05). (F) On Day 7 post-recanalization, the chart indicates that all groups showed significant increases in left kidney GFR. On Day 14 post-recanalization, three groups continued to show increases, although at a slower rate, while the 14days groups exhibited a decline in GFR instead of improvement.