Chapter 25 General Principles and Techniques Animals with later stages of CKD are typically anemic owing to diminished renal erythropoietin production. Elevated circulating parathormone concentrations may also have a negative effect on erythropoietin concentrations. Gastric ulceration, bleeding, or increased red cell fragility may occur in uremic patients. Coagulation profiles are warranted in animals with severe kidney disease. Normally hydrated animals with a packed cell volume (PCV) below 20% or a hemoglobin level less than 5 g/dl may benefit from preoperative blood transfusions (see Box 4-1 on p. 30). The following general anesthetic principles should be considered in animals with renal disease (Table 25-1). The patient may be premedicated with an anticholinergic if bradycardic (i.e., atropine or glycopyrrolate) and an opiate. If the animal has minimal renal compromise, a thiobarbiturate or propofol can be used for induction. Ketamine should be avoided in chronically ill dogs and cats with renal compromise. If a dog is severely depressed, hydromorphone plus diazepam (see Table 25-1) may allow intubation. If additional drugs are needed (see Table 25-1), a reduced dose of etomidate, thiobarbiturate, or propofol may be administered IV. Anesthetic Considerations for Animals with Renal Disease* @Buprenorphine is a better analgesic than morphine in cats. *Patients with renal disease may have decreased volume of distribution and decreased clearance of many drugs. It is recommended to start with low doses and titrate slowly to effect. †Monitor for hyperthermia in cats. Animals with renal calculi, ectopic ureters, or urinary tract obstruction may have concurrent infections and should be given appropriate antibiotics based on urine culture and susceptibility testing; alternatively, antibiotics can be withheld until appropriate intraoperative cultures have been taken. Potentially nephrotoxic antibiotics (i.e., aminoglycosides, tetracycline [except doxycycline], and sulfonamides) should be avoided. Penicillins and cephalosporins (e.g., ampicillin, amoxicillin, cefazolin, cephalexin; Box 25-2) are highly concentrated in urine. They are effective against most Gram-positive organisms; cephalosporins also have an enhanced Gram-negative spectrum. Fluoroquinolones (e.g., enrofloxacin; see Box 25-2) have broad activity against aerobic Gram-negative bacteria. Drug doses or dosing frequency should be altered as required by the degree of renal compromise. Ultrasound-guided percutaneous biopsies require heavy sedation or preferably general anesthesia. Place the patient in ventrodorsal recumbency. If generalized diffuse disease is suspected, as occurs with glomerular disease, the right kidney is the preferred side for a biopsy because it is technically easier to perform. However, either kidney may be sampled from this position. Clip the hair over the biopsy site and aseptically prepare it. Place a sterile sleeve over the ultrasound probe. Using sterile ultrasound coupling gel, identify and examine the kidney. Once the site of entry for the biopsy has been determined, make a small stab incision in the skin using a No. 15 Bard-Parker scalpel blade. The safest approach is to pass the biopsy instrument through the most lateral aspect of the kidney cortex; this is the area farthest from the major vasculature. Insert the biopsy device (e.g., an 18 or 16 g, single spring–fired biopsy core needle [E-Z Core Single Action Biopsy Device, Products Group International, Lyons, Colo.] or an automatic spring-loaded biopsy gun [e.g., Bard Biopty or Monopty single-use spring-loaded disposable biopsy instrument, C. R. Bard, Murray Hill, N.J.]) through the nick in the skin, and advance it until it just penetrates the kidney capsule (Fig. 25-1, A). Position the biopsy needle in such a way that a biopsy is taken of glomerular tissue in the renal cortex, rather than of medullary tissue (Fig. 25-1, B). Place the tip of the needle through the renal capsule before activating it to prevent sliding of the needle along the capsule and to avoid tearing the capsule. Fire the biopsy device, and retract the needle through the skin. Gently manipulate the sample from the biopsy needle, and place it onto a glass slide with physiologic saline. Cut the sample into three sections, and place one in 10% neutral buffered formalin solution for light microscopy and one in glutaraldehyde for electron microscopy; freeze one for immunofluorescence. Perform a needle biopsy with a Tru-Cut-type instrument by placing the tip of the instrument on the kidney capsule with the obturator specimen rod fully retracted within the outer cannula. Position the biopsy needle as described previously (see Fig. 25-1). Push the specimen rod into the lesion by advancing the plastic handle or by triggering the firing mechanism. With manual devices, advance the outer sheath of the needle into the tissue to sever the biopsy sample. Withdraw the needle with the outer sheath over the specimen rod. Apply digital pressure to the site to control hemorrhage. Be sure the sample is long enough (see previous discussion) and primarily consists of cortical tissue. Process the sample as described previously. Grasp the peritoneum over the kidney and incise it. Using a combination of blunt and sharp dissection, free the kidney from its sublumbar attachments. Elevate the kidney and retract it medially to locate the renal artery and vein on the dorsal surface of the renal hilus (Fig. 25-3). Identify all branches of the renal artery. Double ligate the renal artery with absorbable suture (e.g., polydioxanone, polyglyconate, glycomer 631, poliglecaprone 25) or nonabsorbable suture (e.g., cardiovascular silk) close to the abdominal aorta to ensure that all branches have been ligated. Identify the renal vein and ligate it similarly. The left ovarian and testicular veins drain into the renal vein and should not be ligated in intact dogs. Avoid ligating the renal artery and vein together to prevent the formation of an arteriovenous fistula. Ligate the ureter near the bladder. Remove the kidney and ureter and, after procuring appropriate culture specimens, submit them for histologic examination. If possible, strip the renal capsule from the area of the kidney to be excised. Use absorbable suture (No. 0 or 1) with two long, straight needles attached. Thread the needles into the kidney at the proposed resection site (Fig. 25-4, A and B). Tie the thread into three separate ligatures, but avoid damaging the renal vessels or ureter (Fig. 25-4, C). Excise the renal tissue distal to these ligatures. Ligate any bleeders and suture the exposed diverticula with absorbable suture (2-0 or 3-0). Approximate the capsule over the end of the kidney (Fig. 25-4, D), and anchor it to the sublumbar tissues to prevent rotation of the kidney. As an alternative, clamp the renal vessels with vascular forceps and excise the kidney parenchyma. Ligate the parenchymal vessels and close the renal pelvis and diverticula. Suture the capsule as described previously and remove the clamps from the renal vessels. Nephrotomy usually is performed to remove calculi (see p. 726) lodged in the renal pelvis, but it may also be performed to explore the renal pelvis for neoplasia or hematuria. Nephrotomy should be avoided in patients with severe hydronephrosis because ample parenchyma may not be available to prevent postoperative urine leakage. In addition, nephrotomy may temporarily diminish renal function by 25% to 50%. Although bilateral nephrotomies can be performed, this could precipitate AKI if renal function is sufficiently compromised preoperatively. Staged procedures are indicated in such patients. Nephrotomy may be done by bisecting the kidney or by using an intersegmental approach whereby the plane of dissection follows the terminal branches of the posterior and anterior renal arteries. The interlobar arteries are not transected; this theoretically minimizes nephron destruction. Neither technique affected GFR in normal dogs, but because the bisection approach requires less surgical manipulation and time, it is the preferred technique (Stone et al, 2002). Locate the renal vessels and temporarily occlude them with vascular forceps, a tourniquet, or an assistant’s fingers. Mobilize the kidney to expose the convex lateral surface. Make a sharp incision along the midline of the convex border of the kidney capsule, then bluntly dissect through the renal parenchyma, ligating renal vessels as necessary (Fig. 25-5). Culture the renal pelvis. Remove the calculi and flush the kidney with warm saline or lactated Ringer’s solution. Assess the ureter for patency by placing a 3.5 French soft rubber catheter down the ureter and flushing it with warm fluids. Close the nephrotomy by apposing the cut tissues and applying digital pressure for approximately 5 minutes while restoring blood flow through the renal vessels (sutureless technique). As an alternative, appose the capsule with a continuous pattern of absorbable suture material (see Fig. 25-5). If adequate hemostasis is not achieved, or if urine leakage is a concern, place absorbable sutures through the cortex in a horizontal mattress fashion (see previous comments and Fig. 25-5). Then, suture the capsule in a continuous pattern with absorbable suture. Replace the kidney in its original location. Sutures may be placed in the peritoneum where the kidney was elevated to help stabilize it. Pyelolithotomy may be performed to remove renal calculi if the proximal ureter and the renal pelvis are sufficiently dilated. This procedure prevents trauma to the renal parenchyma associated with nephrotomy. Pyelolithotomy is extremely difficult if the ureter is not dilated. Dissect the kidney from its sublumbar attachments and expose the dorsal surface. Identify the ureter and renal vessels (Fig. 25-6, A). Make an incision over the dilated pelvis and proximal ureter, and remove the calculi (Fig. 25-6, B). Flush the renal pelvis and diverticula with warm saline to remove small debris. Next, flush the ureter to ensure its patency. Close the incision in a continuous pattern with 5-0 or 6-0 absorbable suture (Fig. 25-6, C). Make a transverse or longitudinal incision in the dilated ureter proximal to the calculi and remove them (Fig. 25-7, A). Place a small, soft rubber catheter into the ureter proximal and distal to the incision, and flush the ureter with warm fluid. Make sure that all calculi have been removed and that the ureter is patent. Close the incision in a simple interrupted pattern with 5-0 to 7-0 absorbable suture (Fig. 25-7, B). As an alternative, if the ureter is not dilated and if stricture formation seems likely, make a longitudinal incision over the calculi and close the incision in a transverse fashion (Fig. 25-7, C). If the ureter has been damaged, perform a resection and anastomosis (see next section) or a proximal urinary diversion via a nephropyelostomy tube (see p. 718). To perform an extravesical simple interrupted suture pattern technique, make a partial-thickness incision through the muscularis and submucosa of the ventral aspect of the apex of the urinary bladder to expose the mucosa (Fig. 25-8, A). Spatulate the distal end of the ureter, and make an incision equal in length to the spatulation incision in the ureter through the bladder mucosa in the caudal aspect of the muscularis incision. Place a simple interrupted suture (6-0 or 8-0 nylon) between the proximal ureter at the end of the spatulation and the cranial aspect of the bladder mucosal incision, and a second interrupted suture between the distal end of the ureter and the caudal aspect of the bladder mucosal incision (Fig. 25-8, B). Place a 4-0 polypropylene stent into the lumen of the ureter to ensure patency. Place the stent after the first two sutures are tied, and remove it before tying the final sutures of the mucosal layer. Place two additional interrupted sutures between the ureteral and bladder mucosae on one side of the incision (Fig. 25-8, C). Close the seromuscular incision (Fig. 25-8, D).
Surgery of the Kidney and Ureter
Preoperative Management
Anesthetic Considerations
TABLE 25-1
Antibiotics
Surgical Technique
Renal Biopsy
Ultrasound-Guided Percutaneous Biopsy
Needle Biopsy
Nephrectomy
Partial Nephrectomy
Nephrotomy
Pyelolithotomy
Ureterotomy
Ureteral Reimplantation
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Surgery of the Kidney and Ureter
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