Laboratory Studies
Laboratory studies in the evaluation of candidates for ureterocalicostomy include the following:
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Serum electrolytes/hematology: Standard preoperative laboratory testing is advised, including serum electrolytes and blood counts to help rule out any uncorrected physiologic abnormalities (eg, anemia, hyperkalemia, hypokalemia) that might increase the risks of anesthesia. One would not expect abnormalities in the CBC count directly related to the obstruction unless severe compromise of kidney function or active infection is present. Measures should be taken to correct any abnormality prior to surgical repair.
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Serum blood urea nitrogen (BUN) and creatinine (Cr): Kidney function as indicated by the BUN and Cr values may be normal or elevated (indicating impairment of renal function) depending on the function of the affected and contralateral kidney. Nuclear differential renal function studies, which provide a very accurate measure of renal function, should be performed prior to surgery. However, serum BUN and Cr measurements should be obtained immediately prior to surgery to confirm that no acute change in renal function has occurred and to provide a baseline for postoperative follow-up evaluations.
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Coagulation studies: Coagulation studies, including prothrombin time and activated partial thromboplastin time, should be performed because of the risk of excessive bleeding during resection of the extremely vascular renal parenchyma. Uncorrected coagulopathy is a contraindication to surgical repair. Abnormalities of coagulation parameters most likely would be unrelated to the obstruction. Referral to an internist or hematologist would be appropriate before undertaking surgical treatment. In patients with an elevated serum BUN value, bleeding time should also be evaluated to confirm adequate platelet function.
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Urine studies: Urinary tract infection is a contraindication to ureteral reconstructive surgery. If the patient has a positive urine culture but lacks symptoms of a urinary tract infection, the surgeon should consider a preoperative course of antibiotics to reduce bacterial load in hopes of reducing the chance of postoperative infectious complications.
Imaging Studies
Nuclear medicine diuretic scanning is the most widely used test to measure the degree of obstruction and to quantify relative renal function.
The diuretic renal scan allows the measurement of clearance of the radiopharmaceutical over time and the calculation of renal blood flow, which correlates with relative renal function. The most common radiopharmaceuticals currently used to evaluate relative function and obstruction include technetium Tc 99m mercaptotriglycylglycine, which primarily is a tubular agent, and Tc 99m diethylenetriamine pentaacetic acid, which is primarily a glomerular agent. At the peak uptake of radiopharmaceutical, intravenous furosemide, usually 20 mg, is given to induce diuresis and to allow the assessment of urinary clearance.
Diuretic renography showing residual obstruction after a ureteropelvic junction (UPJ) repair should prepare the surgeon for the possible need for ureterocalicostomy. This study also allows determination of differential renal function, assisting in the decision regarding whether the affected kidney has sufficient function (≥ 25% of total renal function) for salvage or whether a nephrectomy is warranted.
An intravenous pyelography (IVP) or CT with excretory phase following intravenous contrast with coronal reconstruction (in institutions where this is available) may be performed to delineate the anatomy of the UPJ. If the patient has poor overall renal function, contrast administration for these studies may cause significant nephrotoxicity. In a completely obstructed system, contrast excretion may be insufficient to clarify the collecting system anatomy.
Antegrade nephrostography often very clearly delineates the renal pelvic anatomy and is generally easily performed, as many candidates for ureterocalicostomy already have a nephrostomy tube in place for temporary drainage. Nephrostography provides as much anatomic information as an IVP or contrast CT scan but without the potential nephrotoxicity of intravenously administered contrast in a kidney that is already at risk for decreased function owing to long-standing obstruction. See images below. Antegrade nephrostography may not accurately delineate ureteral anatomy well depending on the ability of contrast to pass antegrade. In high grade obstructions, the proximal extent of the stricture is all that will be depicted.
Twenty-four-year-old veteran who suffered a high-velocity injury in Iraq, including spinal cord injury, multiple bowel perforations, and left ureteral transection. A cutaneous ureterostomy was performed and nephrostomy tube placed emergently at the time of the injury. Other issues stabilized, and he then underwent evaluation for definitive management of ureteral transection. Cutaneous ureterostomy is nonfunctioning. Antegrade nephrostography performed at the time of nephrostomy tube change showed a blind-ending renal pelvis.
Thirty-six-year-old patient who underwent two prior attempts at left pyeloplasty, with recurrent obstruction. Nephrostogram shows an obliterated ureteropelvic junction.
Retrograde pyelography is useful to help delineate the anatomy of the lower ureter when high-grade obstruction has prevented opacification of the portion of the ureter distal to the obstruction. This study also allows placement of a ureteral stent in order to temporarily relieve obstruction and to preserve or to improve renal function and to facilitate localization and dissection of the ureter during ureterocalicostomy. Simultaneous retrograde pyelography and antegrade nephrostography bests delineates the length of the ureteral defect. See images below.
Simultaneous retrograde pyelogram and antegrade nephrostogram shows blind-ending renal pelvis and significant defect between pelvis and residual distal ureter. The renal pelvis is not completely obliterated, and it may have been reasonable to consider pyeloplasty if the distal ureter was of sufficient length. However, the proximal portion of residual distal ureter is tortuous, medially deviated, and in the area of a significant amount of prior injury and exploration, which will likely prevent isolating adequate length of viable ureter for ureterocalicostomy. This patient underwent autotransplantation.
Sixty-one-year-old patient with a history of radiofrequency ablation of left lower-pole renal mass with subsequent fibrosis of the extrarenal portion of the renal pelvis and proximal ureter. Simultaneous antegrade nephrostogram and retrograde pyelogram show a relatively short defect and healthy-appearing distal ureter. A ureteral stent is placed in the distal ureteral segment to aide in intraoperative identification.
Renal ultrasonography provides excellent anatomical information, including renal parenchymal thickness, echogenicity, and renal growth. Ultrasonography is minimally invasive and is thus useful in monitoring patients after pyeloplasty or ureterocalicostomy. The main drawback is that this modality does not provide any functional data regarding the drainage of the kidney. Thus, nuclear renography may be more useful initially, and renal ultrasonography should be used for long-term follow-up.
Histologic Findings
Histologic findings of a proximal ureteral stricture and fibrotic renal pelvis are nonspecific. Scar formation with collagen deposition and inflammatory infiltrate may be prominent. In cases of radiation-induced fibrosis, a lack of cellularity and vascular hypertrophy with acellular matrix may be present. Malignant obstruction displays characteristics of the specific carcinoma pathology, most commonly transitional cell carcinoma but occasionally other retroperitoneal tumors such as lymphoma or sarcoma.
Staging
Ureteral strictures may be staged based on location, length, and severity. Location is classified as proximal (UPJ to lower pole of the kidney), mid (lower pole of the kidney to the iliac vessels), overlying the iliac vessels, or distal (below the iliac vessels to the ureterovesical junction [UVJ]). Length is the length of the stricture from the proximal to distal extent. For multifocal strictures, this should be measured from the cephalad end of the proximal stricture to the caudad end of the distal stricture, since intervening healthy ureter cannot be salvaged. Severity commonly refers to the patient's degree of obstruction (ie, mild, moderate, severe). Candidates for ureterocalicostomy are predominately those with proximal severe obstruction.
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Diagram of ureterocalicostomy procedure. The left image shows an obstructed kidney with an intrarenal pelvis with dotted lines delineating the areas of the surgical resection. The middle image depicts the kidney following division of the ureter distal to the obstruction and resection of the lower pole of the kidney. The right image is a representation of the ureter anastomosed to the lower-pole calyx.
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Twenty-four-year-old veteran who suffered a high-velocity injury in Iraq, including spinal cord injury, multiple bowel perforations, and left ureteral transection. A cutaneous ureterostomy was performed and nephrostomy tube placed emergently at the time of the injury. Other issues stabilized, and he then underwent evaluation for definitive management of ureteral transection. Cutaneous ureterostomy is nonfunctioning. Antegrade nephrostography performed at the time of nephrostomy tube change showed a blind-ending renal pelvis.
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Thirty-six-year-old patient who underwent two prior attempts at left pyeloplasty, with recurrent obstruction. Nephrostogram shows an obliterated ureteropelvic junction.
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Postoperative intravenous pyelogram showing drainage from calyx into ureter after ureterocalicostomy.
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Intraoperative photograph during ureterocalicostomy. The lower pole of the kidney has been identified. The ureter has been dissected and the atretic segment divided.
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The ureter has been spatulated and anastomosed to the lower pole calyx over a ureteral stent. The fat pad to the left of the anastomosis will be wrapped around the anastomosis and a drain will be placed.
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Simultaneous retrograde pyelogram and antegrade nephrostogram shows blind-ending renal pelvis and significant defect between pelvis and residual distal ureter. The renal pelvis is not completely obliterated, and it may have been reasonable to consider pyeloplasty if the distal ureter was of sufficient length. However, the proximal portion of residual distal ureter is tortuous, medially deviated, and in the area of a significant amount of prior injury and exploration, which will likely prevent isolating adequate length of viable ureter for ureterocalicostomy. This patient underwent autotransplantation.
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The lower pole of the kidney has been amputated and the lower pole calyx identified. Both the kidney and ureter are mobilized to allow a tension-free anastomosis.
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Sixty-one-year-old patient with a history of radiofrequency ablation of left lower-pole renal mass with subsequent fibrosis of the extrarenal portion of the renal pelvis and proximal ureter. Simultaneous antegrade nephrostogram and retrograde pyelogram show a relatively short defect and healthy-appearing distal ureter. A ureteral stent is placed in the distal ureteral segment to aide in intraoperative identification.
