22 Eric Monnet Removal of kidney stones represents a surgical challenge. Stones can be removed by a nephrotomy or a pyelolithotomy. Nephrotomy has the potential to reduce kidney function by the damage to the renal parenchyma associated with surgical manipulation and transient ischemia.1-4 Pyelolithotomy is a preferred technique because it does not interfere with the renal parenchyma and reduces the risk of compromised kidney function. However, it is only possible if the renal stones have migrated into the renal pelvis close to the proximal ureter.5 A laparoscopic-assisted approach may represent an alternative to remove stones that are not located in the renal pelvis but may migrate into the ureters and induce a urinary obstruction with hydroureter and hydronephrosis. The author has performed this procedure only in cats with chronic renal disease and uroliths in the ureter and the recesses of the renal pelvis. Kidney stones in cats can be isolated, but more often they are associated with stones in the ureter, inducing partial or complete urinary obstruction. The most common clinical signs reported in cats with uroliths in the upper urinary tract are nonspecific, such as reduced appetite, lethargy, and weight loss.6,7 Clinical signs may also be referable to uremia, such as vomiting, polyuria, and polydipsia, or directly to ureteral obstruction, such as stranguria, pollakiuria, hematuria, and abdominal pain.6,7 A complete blood count, chemistry profile, urinalysis, and urine culture should be performed. The blood urea nitrogen (BUN) and creatinine concentrations depend on the hydration status of the patient, kidney function, presence and extent of ureteral obstruction, and the function of the contralateral kidney. In one study of 163 cats with ureteral calculi, 83% of cats had a BUN or creatinine concentration above the reference range, and 33% were markedly azotemic (creatinine concentration >10 mg/dL; reference range, 1.1–2.2 mg/dL).6,7 Seventy-six percent of cats with unilateral calculi were azotemic compared with 96% of cats with bilateral calculi. In addition, hyperphosphatemia was observed in 54%, hyperkalemia in 35%, and anemia in 48% of cats with ureteral calculi.6,7 Urine should be evaluated for the presence of crystalluria, hematuria, and urinary tract infection. Most uroliths of the upper urinary tract are diagnosed using abdominal radiography and ultrasonography. When urolithiasis is diagnosed, the entire urinary tract should be evaluated for calculi.6
Laparoscopic-Assisted Nephrolith Removal
Preoperative Considerations
Clinical Evaluation
Imaging
Plain Radiographs
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