Surgery of the Kidney and Ureter

Chapter 25


Surgery of the Kidney and Ureter



General Principles and Techniques



Definitions


Nephrectomy is excision of the kidney; nephrotomy is a surgical incision into the kidney. Nephrostomy is the creation of a permanent fistula leading into the pelvis of the kidney; temporary nephrostomy tubes (nephropyelostomy) are occasionally used to divert urine when obstructive uropathy occurs or when the proximal ureter has been avulsed from the kidney. Pyelolithotomy is an incision into the renal pelvis and proximal ureter; a ureterotomy is an incision into the ureter; both are generally used to remove calculi. Neoureterostomy is a surgical procedure performed to correct intramural ectopic ureters; ureteroneocystostomy involves implantation of a resected ureter into the bladder. Chronic kidney disease (CKD) refers to patients with markers of structural or functional kidney damage of longer than 3 months’ duration. A staging system for CKD has been proposed by the International Renal Interest Society (IRIS) for canine and feline CKD (Box 25-1), reflecting degrees of creatinine concentration with substages regarding proteinuria and blood pressure. Renal failure is defined as when 75% of nephrons in both kidneys cease to function. Chronic renal failure (CRF) refers to patients with CKD with significant clinical signs (polyuria, polydipsia, weight loss, decreased appetite) and laboratory findings (azotemia, anemia, proteinuria). Damage to the kidney is usually irreversible because nephrons are replaced by fibrous connective tissue. Acute renal failure (ARF) may also be referred to as acute kidney injury (AKI) and refers to patients that have an abrupt decline in renal function usually caused by an ischemic, toxic, or infectious insult. Sometimes this becomes confusing; animals with CRF or CKD can become acutely worse if reasons for acute injury are superimposed upon the chronic condition (i.e., acute on chronic kidney failure).



image Box 25-1   Staging System for Chronic Kidney Disease (CKD)


Step 1: Staging is initially based on fasting plasma creatinine assessed on at least two occasions in the stable patient.







Preoperative Management


Renal, ureteral, or urethral disease may cause AKI or CKD, or disease in these organs may be associated with AKI or CKD from other causes. The minimum database for patients with urinary dysfunction includes measurement of hematocrit, blood urea nitrogen (BUN), phosphorus, calcium, creatinine, total protein, albumin, magnesium, electrolytes, total carbon dioxide levels, urinalysis, and blood pressure, and an electrocardiogram if electrolyte values are not readily available. Renal patients may have significant metabolic derangements besides azotemia. CKD and especially AKI may be associated with varying degrees of dehydration. Oliguria may be present in AKI or in severe CKD; however, both AKI and CKD may be associated with polyuria. Preoperative intravenous (IV) fluid therapy is necessary to restore circulating blood volume and urine production; however, fluids must be administered judiciously to prevent overloading of these patients. Diuretics may also be helpful for enhancing urine production in animals that are adequately hydrated. Urine production of hydrated animals on maintenance fluids that do not have abnormal extrarenal losses should be at least 50 ml/kg/day or more than 2 ml/kg/hr.


Various electrolyte and acid-base abnormalities may occur, depending on the severity and duration of the renal, urethral, or ureteral disease. Hyperkalemia often is present in AKI owing to obstructive disorders, uroabdomen, and parenchymal dysfunction. Hypokalemia may occur with CKD and diuretic therapy. Hyperkalemia and hypokalemia predispose the patient to cardiac arrhythmias and should be addressed before surgery. Severe hypermagnesemia and hypomagnesemia can cause cardiac conduction disturbances and central nervous system (CNS) aberrations. Clinically important hypocalcemia occasionally is associated with AKI. Hypercalcemia may cause AKI or may be due to CKD. Metabolic acidosis may be present in animals with acute or chronic kidney disease but tends to be worse with acute injury.



NOTE • Abnormalities in the serum potassium level may lead to cardiac arrhythmias and death; correct these abnormalities before surgery.


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).



Anesthetic Considerations


Animals with CKD may pose unique challenges for anesthesia. The CKD patient may have chronic electrolyte abnormalities that generally should be corrected slowly. Severe hypokalemia may cause electrocardiographic (ECG) changes (e.g., flattened T waves, U waves) and a prodysrhythmic state; affected patients may have skeletal muscle weakness. Severe hypomagnesemia sometimes causes dysrhythmias, weakness, or hypotension. Patients may be tachycardic owing to hypovolemia, which may mask concurrent hypertension or anemia. Affected animals may be malnourished and hypoproteinemic; this may affect how they respond to medications. Azotemic patients have altered drug binding secondary to changes in pH and hypoproteinemia, as well as an altered blood-brain barrier; thus, they are particularly susceptible to medications that cause sedation. Therefore the lower end of drug doses should be used.


Patients with AKI (e.g., acutely obstructed animals) often are otherwise healthy. Patients may present early or late in the course of obstruction; therefore, clinical signs vary from an uncomfortable, straining cat with normal laboratory values to a recumbent, moribund AKI patient. The mildly affected animal can be treated similarly to an otherwise healthy patient, except that special attention should be paid to limiting IV fluids before relieving the urinary obstruction. The obstructed patient with AKI may have sodium and potassium disturbances and possibly life-threatening ECG changes associated with hyperkalemia, hypovolemia, hypotension, weakness, and hypothermia. These patients usually can tolerate only limited doses of drugs causing further sedation or hypotension. Another group of AKI patients consists of those with CKD that have acute disease superimposed, and therefore present in an AKI crisis. Laboratory data are extremely important in determining the animal’s electrolyte status and in anticipating the animal’s response to anesthesia.


Several generalities can be made about patients with renal disease. First, the decompensated patient that is hypovolemic and depressed usually needs minimal to no premedication. Opioids may need to be given to effect during surgery, instead of as a premedication. Second, many drugs (e.g., induction agents, pain medications) have to be given slowly and in lower doses than in healthy animals. One can always give more of an induction agent; it is difficult to take it back once given. Third, when possible, slowly correct electrolyte abnormalities, hypovolemia, anemia, and hypothermia before surgery. Patients should be diligently monitored intraoperatively and postoperatively, including oxygen saturation via pulse oximeter (SpO2), blood pressure, ECG, respiratory rate, and temperature. In addition, monitoring of end-tidal carbon dioxide (EtCO2) is very helpful in titrating narcotics intraoperatively and in assessing adequacy of ventilation.


Severely anemic patients should be transfused if the hematocrit is low (<18% in cats; <20% in dogs) before induction of anesthesia; these animals will benefit from oxygen before, during, and after anesthesia (see p. 31). Anticholinergic drugs should be given as needed to prevent or treat bradycardia. Medications that should be avoided in patients with renal compromise include nonsteroidal anti-inflammatory drugs (NSAIDs), aminoglycosides, and some contrast agents. Compound A, a by-product of sevoflurane, causes renal failure in rats; however, research does not support this finding in dogs, cats, and humans. In the human literature, it is recommended to use sevoflurane at an oxygen flow rate greater than 2 L/min to protect against nephrotoxicity in compromised patients, or to use isoflurane. Ketamine at low doses or as a low-dose constant rate infusion (CRI) generally is not contraindicated in animals with renal disease. However, in chronically ill or compromised patients, ketamine can cause problems when used at induction doses. Ketamine stimulates the sympathetic nervous system and inhibits reuptake of norepinephrine. The effect of ketamine relies on adequate catecholamine stores to support blood pressure during induction. In chronically ill or severely compromised patients, catecholamine stores may be depleted, resulting in marked hypotension and bradycardia when this drug is used.


Systemic arterial blood pressure should be maintained between 70 and 80 mmHg to ensure adequate renal perfusion, and urine output should be monitored during surgery with a urine output goal of at least 0.5 ml/kg/hr. Because of the intrinsic properties of the kidney to autoregulate, renal blood flow tends to remain constant despite variations in systemic arterial pressure between 75 and 160 mmHg. However, hypotension during surgery may cause renal vasoconstriction, diminished renal blood flow, and subsequent renal damage. Hypotensive drugs (e.g., acetylpromazine) should not be used in animals with renal impairment. If the cat is oliguric but normotensive, mannitol 0.25 to 0.5 g/kg IV may be used. If both oliguria and hypotension are present, dopamine (dogs: 5 to 20 µg/kg/min IV; cats: 2 µg/kg/min IV) or dobutamine (2 µg/kg/min IV) may be administered. Once oliguria is established, dopamine is minimally effective at creating a polyuric state. Thiobarbiturates should be avoided if arrhythmias are present. Isoflurane is the inhalation agent of choice in arrhythmic patients. If nephrectomy is to be performed, function in the remaining kidney should be protected by ensuring adequate blood flow during and after surgery.


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.



Water should not be withheld preoperatively in patients with renal disease, and careful attention should be paid to hydration status. IV fluids should be given to almost every animal with renal disease.



Antibiotics


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.



image Box 25-2   Selected Antibiotics of Use in Animals with Renal Disease*







*Although in human patients, these drugs are routinely dosed based on the degree of renal impairment, this is not done in veterinary medicine because they are safe and have few serious side effects.



Surgical Anatomy


The kidneys lie in the retroperitoneal space lateral to the aorta and the caudal vena cava. They have a fibrous capsule and are held in position by subperitoneal connective tissue. The cranial pole of the right kidney lies at approximately the level of the thirteenth rib, opposite the first three lumbar vertebrae. The cranial one-third is covered by the caudate process of the caudate lobe of the liver. The cranial pole of the left kidney lies opposite the second to fourth lumbar vertebrae, farther caudal than the right kidney by approximately half a kidney length. The renal pelvis is the funnel-shaped structure that receives urine and directs it into the ureter. Generally, five or six diverticula curve outward from the renal pelvis. The renal artery normally bifurcates into dorsal and ventral branches; however, variations in the renal arteries and veins are common. The ureter begins at the renal pelvis and enters the dorsal surface of the bladder obliquely by means of two slitlike orifices. The blood supply to the ureter is provided from the cranial ureteral artery (from the renal artery) and the caudal ureteral artery (from the prostatic or vaginal artery).



NOTE • The anatomy of the renal vasculature varies considerably, so use care when ligating these vessels during nephrectomy.



Surgical Technique


To address the kidney, a ventral midline abdominal incision is performed from the xiphoid to caudal to the umbilicus. If the distal ureter is to be transected (i.e., nephrectomy), or if a cystotomy is necessary, the incision should extend to the pubis. Balfour retractors are used to retract the abdominal wall and expose the kidney. The entire abdominal contents should be inspected before the urinary tract is explored. The right kidney is exposed by elevating the duodenum and displacing the other loops of intestine toward the animal’s left side. Similarly, the left kidney is exposed by elevating the mesocolon so that the small intestine is retracted to the animal’s right side. The kidney can be isolated from the remaining abdominal contents with moistened laparotomy sponges.



Renal Biopsy


Renal biopsy may be indicated to determine a definitive diagnosis in dogs and cats with renal disease, or to provide an estimate of the severity or reversibility of renal damage. It may be performed at surgery, or it may be done percutaneously by ultrasonography, laparoscopy, or digitally using a keyhole abdominal incision. Ultrasound-guided and laparoscopic biopsies are the preferable percutaneous techniques. Renal biopsy should be avoided in patients with bleeding disorders, large intrarenal cysts, perirenal abscesses, severe hydronephrosis, and obstructive uropathy. Administering fluids before, during, and shortly after biopsy to initiate and maintain a mild diuresis may reduce formation of blood clots in the renal pelvis, which could cause hydronephrosis. Spring-loaded biopsy needles, biopsy guns, or manual devices (e.g., Tru-Cut) may be used to obtain a sample, but manual devices are not recommended because they can easily produce fragmented tissue samples. Advantages of the spring-loaded devices are that they can be manipulated with one hand and often obtain better samples with less artifact, especially when guided by ultrasound. Sixteen gauge needles are often used, but 18 gauge needles are typically adequate and may be easier to use in smaller patients. Attention to detail is critical; a good quality sample obtained with an 18 gauge needle is more useful than a ragged or fragmented sample from a 16 gauge needle. In healthy dogs, serial ultrasound-guided renal biopsies were not found to induce functional changes in the kidneys or histologic changes that might be confused with progressive renal disease (Groman et al, 2004). Needle biopsies are often inadequate when juvenile-onset renal disease (i.e., renal dysplasia) is evaluated because of nonuniform distribution of lesions; wedge biopsies are preferred in such cases.



NOTE • It is extremely easy to obtain tissue samples that are nondiagnostic because they primarily consist of medullary tissue, are too small, have too few glomeruli, or have too many artifacts. For patients with glomerular disease, at least two samples larger than 10 mm or three samples smaller than 10 mm are recommended. These samples should be divided and placed in appropriate solutions for light microscopy, immunofluorescence, and electron microscopy immediately after they are obtained. The minimum numbers of glomeruli required for accurate diagnosis of glomerular disease are as follows: 5 to 10 for light microscopy, 1 to 2 for electron microscopy, and 3 to 5 for immunofluorescence. The smaller number is adequate if all glomeruli are similar, but the larger number is needed if they are dissimilar (a common situation). For patients with AKI, two samples larger than 7 mm submitted in formalin for light microscopy is sufficient. Obtaining multiple biopsies of the kidney does not appear to produce more damage than a biopsy with only a single pass, provided that the biopsy needle remains in cortical tissue (Vaden, 2004).



Ultrasound-Guided Percutaneous Biopsy


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.




NOTE • Do not place the biopsy needle too deep in the kidney or too few glomeruli may be obtained in the sample. The risk for transection of a large arcuate vessel is also present (Fig. 25-1, C).




Laparoscopically Guided Biopsy


Laparoscopy for renal biopsy requires general anesthesia. In general, renal biopsy is done laparoscopically only when other biopsies (e.g., hepatic, pancreatic) are required and are the primary indication for laparoscopy. If the primary purpose of the procedure is to obtain renal biopsies, ultrasound is typically preferred. Single-cannula laparoscopy is sufficient for insufflation and visualization; however, double cannulas will provide an instrument portal to facilitate manipulation of the viscera and stabilization of the kidney during biopsy.


Using a No. 15 Bard-Parker scalpel blade, make a third small skin incision for penetration of a 16 to 18 gauge core biopsy needle. Use the manipulation instrument to position and secure the kidney, and place a double spring–fired biopsy needle against the renal capsule and direct it tangentially before discharge. After the biopsy, withdraw the needle and apply pressure via the manipulating instruments. Be sure the samples consist of cortical tissue and are of sufficient length, then process as described previously.




Needle Biopsy


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.



NOTE • Avoid taking a biopsy near the renal pelvis to prevent extravasation of urine. To make sure that you get a diagnostic sample, position the biopsy device across the cortex, as indicated previously.





Nephrectomy


Nephrectomy (ureteronephrectomy) is indicated for renal neoplasia, uncontrollable hemorrhage, persistent urine leakage, pyelonephritis resistant to medical therapy (e.g., associated with nephroliths), hydronephrosis, and ureteral abnormalities that defy surgical repair (e.g., avulsion, stricture, rupture, obstruction due to calculi). Before nephrectomy, renal function in the opposite kidney ideally should be assessed by determining the glomerular filtration rate (GFR) through administration of an exogenous marker or by nuclear scintigraphy. Bilateral renal dysfunction may warrant a guarded prognosis. If renal neoplasia is suspected, radiography (thoracic and abdominal) and ultrasonography should be used to help rule out metastasis, including the opposite kidney.



NOTE • To avoid unintentional transection, the opposite ureter should always be identified before the affected kidney is removed; this is particularly important when large neoplasms are removed.


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.




Partial Nephrectomy


Partial nephrectomy is occasionally warranted for focal renal lesions, particularly if preservation of renal function is necessary because of bilateral renal dysfunction. However, in most cases total nephrectomy is usually easier and carries less risk of postoperative hemorrhage. If partial nephrectomy is performed, electrocoagulation of bleeding vessels should be avoided because it causes excessive parenchymal damage. Avoid partial nephrectomy in animals with clinically significant coagulopathies; excessive blood loss may occur after this procedure.


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


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).


Nephrotomy incisions may be closed without sutures or with transparenchymal horizontal mattress sutures. The latter may cause increased vascular strangulation, pressure necrosis, infarction, and postoperative hemorrhage. Cyanoacrylate adhesive provides rapid hemostasis; however, if the adhesive enters the renal diverticula, calculi may form.


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


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).




Ureterotomy


Ureterotomy occasionally is performed to remove obstructive calculi. The procedure carries the risk of postoperative leakage and stricture formation and should be performed with care. If obstruction is not present, dietary dissolution of struvite calculi may be attempted. However, removal of calculi is indicated if obstruction occurs or seems likely (e.g., hydroureter, hydronephrosis). Depending on the animal’s size, removal of the stones with a ureteroscope may be possible. Some stones in the distal ureter may be flushed or pulled into the bladder through a cystotomy, making a ureterotomy unnecessary. Although ureteral mucosa regenerates over a stent if the mucosa has not been completely disrupted, the use of stenting catheters is controversial because they may promote stricture formation and infection. If stents are used, they should be smaller than the diameter of the ureter. In some animals, ureteral stents may be placed so that they exit the urethral orifice and are sutured to the exterior. Transverse or longitudinal incisions may be made in the ureter; however, tension on transverse ureterotomies may be less; therefore they may heal more readily.


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).




NOTE • Ureterotomy, ureteral reimplantation, and ureteral anastomosis are greatly facilitated by wearing loupes for magnification or by using an operating microscope.




Ureteral Reimplantation


The diameter of the feline ureter is approximately 0.4 mm at the level of the bladder, and standard ureteroneocystostomy techniques often cause ureteral obstruction. Microsurgical techniques may be necessary to prevent ureteral obstruction in cats, particularly when the ureter is not dilated owing to disease (e.g., renal transplantation). A “drop-in” technique was originally described for ureteroneocystostomy of cats undergoing renal transplantation; however granuloma formation and hemorrhage were common. Extravesical techniques have largely replaced intravesical techniques in people. A recent study in cats suggested that the extravesical technique using a simple interrupted suture pattern was preferred over an extravesical technique using a continuous suture pattern or an intravesical mucosal apposition technique (Mehl et al, 2005). Although all three techniques resulted in renal pelvis dilation, the dilation resolved more rapidly with the extravesical technique using a simple interrupted pattern, and this technique was associated with consistently lower serum creatinine concentrations during the first postoperative week.


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).


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Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Surgery of the Kidney and Ureter
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