Chapter 195 The direct treatment of nephroliths is necessary only when they become problematic, which is the case less than 10% of the time in the authors’ experience. Nephroliths are considered problematic when one of the following occurs: recurrent urinary tract infections (despite administration of appropriate antibiotic therapy for >8 to 12 weeks), pyelectasia or hydronephrosis, worsening renal function, pain and discomfort, or resulting intermittent ureteral obstruction. Traditional open surgical options to treat problematic nephroliths (e.g., nephrotomy, nephrectomy) are associated with frequent complications and high long-term morbidity. In a clinical study of dogs, approximately 43% had stone fragments remaining after surgery and 23% had procedure-related complications (Gookin et al, 1996). Additionally, 67% of dogs had evidence of renal azotemia that developed following nephrectomy. In a feline study of normal cats there was a 10% to 20% decrease in the glomerular filtration rate of the kidney in which a nephrotomy was performed (King et al, 2006). It is important to realize that in healthy animals the renal hypertrophic mechanisms are still functional, but in clinically affected dogs and cats this process already has been exhausted, which makes the change in renal function more dramatic. The use of less invasive approaches, such as extracorporeal shock wave lithotripsy (ESWL) (for stones of <1.5 to 2 cm) or PCNL (for stones of >1.5 to 2 cm), has been shown to be associated with preservation of renal function in humans. PCNL is highly effective in removing all stone fragments in the calices and does not require cutting of the nephrons. Instead, tissues are spread apart with the use of a balloon dilation kit to allow an endoscope and intracorporeal lithotriptor to remove the stone debris effectively. Figure 195-1 Dog with nephroliths undergoing percutaneous nephrolithotomy. The endoscopic image on the top shows the calcium oxalate nephrolith inside the renal pelvis during ultrasonic and electrohydraulic intracorporeal lithotripsy. A, Percutaneous access is obtained using ultrasonography and fluoroscopy. An 18-gauge catheter punctures the kidney onto the nephrolith (asterisk). A guidewire (white arrows) is advanced down the ureter into the bladder and out the urethra for through-and-through access. A second wire is advanced down the ureter for placement of the renal access sheath (black arrow). B, Nephroscope (white arrow) through the ureteral access sheath and multiple stone fragments are visualized (black arrowheads). Figure 195-2 Female dog with idiopathic renal hematuria. Dorsoventral abdominal fluoroscopic image during ureteroscopy (caudal is left and cranial is right) and ureteroscopic images during cauterization. A, A cystoscope (white arrow) is used to identify the ureterovesicular junction, and a ureteral catheter is advanced up the most distal aspect of the ureter for retrograde ureteropyelography using a contrast agent (Iohexol). B, An angled-tipped hydrophilic 0.035-inch guidewire (black arrows) is advanced through the working channel into the ureteral opening, up the ureter, and into the renal pelvis. The J-hooked distal ureter is observed (white arrowhead). C, The cystoscope is removed over the guidewire, and the flexible ureteroscope is advanced over the wire and into the renal pelvis (white arrows). D, During cystoscopy the left ureterovesicular junction is seen to have jets of bloody urine identifying the side of bleeding. E, A lesion on the renal papilla inside the renal pelvis that is bleeding. F, An electrocautery probe (blue) is used through the flexible ureteroscope for cauterization.
Interventional Strategies for Urinary Disease
Kidney and Ureter
Interventional Approach to Nephrolithiasis
Percutaneous Nephrolithotomy
Interventional Approach to Essential Renal Hematuria
Ureteroscopy
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