A Mouse Model to Evaluate the Long-Term Structural and Functional Outcomes after the Reversal of Prolonged Unilateral Ureteric Obstruction

My laboratory works on the mechanisms and therapy to improve long-term outcomes after kidney injury, and the specific focus of this protocol is to develop a tool to study long-term outcomes after reversal of urinary obstruction. We have developed a mouse model of unilateral reversible ureteric obstruction, which allows us to evaluate the long-term functional and structural outcomes of reversing urinary obstruction in the kidney. Other methods require multiple surgeries or microsurgical expertise, which most laboratories do not have access to. In addition, because this is unilateral obstruction, most other methods do not allow functional evaluation of recovery without performing split renal function tests. There really only two. The first is consistent placement of the vascular clamp at the same position on the proximal ureter in each experiment, and the second is removal of the vascular clamp several days later without causing damage to the ureter or kidney.

[Rachel] To begin, prep the surgical side of an anesthetized mouse with antiseptics. Make a 1.5 centimeter longitudinal dorsal incision along the midline through the skin and subcutaneous layers using scissors and forceps. Make a small incision through the left flank muscle and fascia above the kidney. Then with a pair of forceps, exteriorize the left kidney. Using blunt forceps. Carefully dissect the fat at the lower pole and some connective tissue near the ureter. Locate the ureter region. Then separate the ureter along with its connective tissue from the renal pedicle to avoid including the renal vein and artery with the clamp. Use clamp appliers to open the vascular clamp and position it directly below the renal pelvis on the ureter. Use the markings on the clamp to ensure uniform pressure is applied across all mice. Now use a saline soaked sterile cotton swab to gently push the kidney with the clamp back into the retroperitoneal space. Then suture the muscle layer using an absorbable suture. Use skin clips to close the skin layer. To remove the ureteric clamp, remove the wound clips then clean the surgical area without reshaping using the original incisions to access the clamp. Reopen the muscle layer and expose the retroperitoneal space. Use forceps to carefully locate the clamp in the retroperitoneal space without exteriorizing the kidney. With clamp appliers, gently open the clamp while pulling the surrounding tissue away using forceps to safely remove it. Now exteriorize the kidney to inspect the renal pelvis for obstruction. A swollen renal pelvis confirms hydronephrosis. Push the kidney back into the retroperitoneal space using a saline soaked sterile cotton swab and suture the incision shut as demonstrated. To perform contralateral nephrectomy, reopen the dorsal site using the original skin incision. In size, the right flank muscle, and fascia above the kidney. Then exteriorize the right kidney using forceps. Hold the right kidney with smooth, curved forceps and dissect the upper and lower poles free from the surrounding tissue. After freeing the kidney, tie a Foro silk suture around the renal vessels and ureter using a double surgical knot. Wait for approximately 30 seconds until the kidney darkens. Then hold it with the smooth curved forceps and remove it by cutting distally to the knot using curved scissors. Gently push the remaining renal pedicle back into the retroperitoneal space using a saline soaked sterile cotton swab, then close the muscle and skin layers using sutures and clips. Typical survival and renal function measurements were taken 84 days after reversible unilateral ureteral obstruction. Functional studies compared reversible unilateral ureteral obstruction with nephrectomy alone for blood urea nitrogen, transdermal glomerular filtration rate, and urinary osmolarity after 18 hours of water deprivation. Urinary osmolarity values were markedly lower than nephrectomy control mice at the same time points.