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Urology Lillian R. Aronson, VMD, Diplomate ACVS University of Pennsylvania, School of Veterinary Medicine Feline Renal Transplantation Introduction The first renal transplant performed in an animal was in Vienna by Dr. Emerich in 1902 and then in 1905 by Dr. Alexis Carrel in the United States. Interestingly, up until a few years ago, the vascular technique developed by Dr. Carrel for the anastomosis of the donor and recipient vessels was used exclusively. The first successful clinical feline transplant was performed at the University of California, Davis on a Persian cat named "Queenie." She lived for 2 years with her new kidney and then died of heart failure. Queenie's renal function was normal at the time of her death. There are many important aspects to a successful transplant program. These include, careful case selection, having the appropriate technical preparation and support, having the appropriate equiptment and facilities, and good communication with referring veterinarians and owners. Once the cat becomes part of the transplant program, constant contact is maintained with the referring veterinarian and owner for the rest of the cat's life, so good communication is essential. Renal transplantation is currently an accepted treatment option for cats in renal failure, however, not every cat is a candidate for the procedure. This is often very difficult for many owners to understand, because they believe that transplantation is the "last ditch" effort that can potentially save their cat. Unfortunately, often when a transplant has been performed on an inappropriate candidate, usually because of a persistent owner, a poor outcome has resulted. Case selection Proper case selection is essential. The best candidate for renal transplantation is the patient in very early decompensated renal failure. Probably the best determinant of this is body weight. A 10 to 20% decrease in body weight will still allow a patient, in otherwise good health, to withstand the stress of anesthesia. As weight loss increases, the morbidity and mortality of surgery increases. Although, there is not an absolute age restriction for transplantation, the oldest cat that has been transplanted was 18 years of age. The degree of azotemia, anemia and urine specific gravity, do not determine, in themselves, a suitable patient for transplantation. In some facilities, hemodialysis is used to correct electrolyte and acid/base imbalances to lower the blood urea nitrogen level to 100mg/dl or less. Candidates should be free of other disease conditions including heart disease, recurrent urinary tract infections, inflammatory bowel disease and underlying neoplasia. Many cats in renal failure have a heart murmur. This murmur may be a physiologic murmur secondary to the anemia. This does not, in itself, disqualify a candidate for the procedure. The concern would be if the cat had underlying heart disease, for example, hypertrophic cardiomyopathy. Cats with recurrent urinary tract infections are also not good candidates, since infection can potentiate rejection. If the cat currently has a negative urine culture, a cyclosporine (2-5mg/kg) challenge is recommended prior to transplantation to determine if the cat will "break" with an infection. Preoperative examination includes a serum chemistry profile, a complete blood count, urinalysis and culture, urine protein:Cr ratio, FeLV/FIV test, toxoplasmosis titer, parathyroid hormone level, thoracic and abdominal radiographs, abdominal ultrasound and an electrocardiographic examination. The feline recipient must also be blood crossmatched to 2 or 3 blood donor cats. Donor selection The kidney donors are cats from the SPCA or cats from SPF colonies that would otherwise be euthanized. An owner may elect to use one of the family's other cats as a kidney donor. The renal donor should be a healthy, young adult that is crossmatch compatible to the recipient. The antigens present on the red blood cells are also present on the endothelium of the graft blood vessels. Preformed antibodies to these antigens can cause a clot to form in the graft vessels resulting in organ infarction. The donor should have no evidence of renal insufficiency based on a complete blood count, serum chemistry profile and urinalysis. The cat must be FeLV/FIV negative. A contrast enhanced CT is performed to assure that the donor has two normally shaped, well vascularized kidneys. The client is required to adopt the donor cat since no cat is ever euthanized for the program. Preoperative care Preoperative care includes a protein restricted diet, phosphate binders, intravenous administration of a balanced electrolyte solution and blood transfusions to correct the anemia. Blood products need to be available for surgery. Some cats in chronic renal failure are not transfusable because of incompatabilities despite the fact that the cats are of the same blood type. Blood crossmatching is an important consideration particularly if the patient is traveling a great distance to the transplant clinic. The recipient is started on immunosupression 24-48 hours prior to surgery. Cyclosporine and prednisone/prednisolone are used in combination for their synergistic effects. Cyclosporine blocks IL-2 secretion by T helper cells, inhibits IL-1 release by macrophages, and reduces the response of T cytotoxic cells to IL-2. CyA does not cause cell death, but interferes with the cell communication by cytokines necessary for T cell activation. The exact mechanism of action of prednisolone/prednisone in not completely known. It may cause destruction of B and T cells by decreasing DNA, RNA and protein synthesis and decrease neutrophil and macrophage migration and phagocytosis. Prednisone/prednisolone can enhance the immunosuppressive ability of other agents. Cyclosporine and prednisone are administered in a gelatin capsule so the cat does not taste the Cyclosporine. Blood levels should be monitored regularly to maintain therapeutic concentrations and minimize side affects. Currently, the 12 hour trough level is measured, just prior to the next oral dose. There seems to be very little correlation between the oral dose of Cyclosporine and the blood level that will be achieved in a particular patient. Two 4kg cats can be given the same oral dosage and their blood levels may be entirely different. Because of interpatient and intrapatient variability in the absorption of oral Cyclosporine and its metabolism, blood levels should be monitored regularly to maintain therapeutic concentrations and minimize toxic side effects. Currently a trough level of 500 ng/ml is maintained for the first 30 days following surgery, and is then reduced to approximately 200-300 ng/ml for long term therapy. If renal function starts to deteriorate in the first weeks to months following transplantation, Azathioprine (0.3mg/kg/72 hours) may be added to the immunosuppressive protocol. Cats receiving Azathioprine should have their white blood cell count monitored regularly. Anesthesia At the time of anesthetic induction, both the donor cat and the recipient are given cephalexin. The specific anesthetic protocol for these patients is not necessarily unique to this procedure, however there are some important aspects that need to be mentioned. The recipient cat may be under anesthesia for as long as 6 hours and hypothermia is of serious concern and can be detrimental to these patients. The cat should be kept warm during the entire procedure. Whole blood is administered to the recipient to maintain the packed cell volume as close to 30% as possible. Systemic arterial blood pressure should be monitored regularly and fluid, blood or dopamine administration used to maintain systolic pressure ~ 90mmHg. Surgery Renal transplantation should be performed by veterinarians familiar with vascular surgery. The donor and recipient surgeries are performed simultaneously. The donor is brought into the surgical suite approximately 30-45minutes prior to the recipient. During this time, the donor kidney will be prepared for the nephrectomy. The left and right kidneys are examined for a vascular pedicle that consists of a single artery. The left kidney is preferred because it provides a longer vein than the right kidney. The renal artery and vein are cleared of as much fat and adventitia as possible. The ureter is dissected free to the point where it joins the bladder. The nephrectomy will be performed when the recipient is prepared to receive the kidney. At the time of the original incision, the donor is given a dose of mannitol (1g/kg IV). Fifteen minutes prior to nephrectomy, an additional dose of mannitol (.25 g/kg IV) is given to the donor cat. Mannitol is used to reduce the incidence and duration of acute tubular necrosis that can occur during warm ischemia. Two surgical procedures have been described for the recipient. The first technique (described by Dr. Carrel), transfers the transplanted kidney to the recipient's iliac vessels. Preferably, a left donor kidney is placed in the right iliac fossa of the recipient, and a right donor kidney in the left iliac fossa. The chosen iliac fossa is prepared for end to end anastomosis of the renal artery to the iliac artery and end to side anastomosis of the renal vein to the iliac vein. Because of limited exposure, the vein is anastomosed first. Silk (7-0) is used for the venous anastomosis and nylon (8-0) is used for the arterial anastomosis. Approximately 20% of the cats undergoing this procedure were developing some form of hind leg complications including lameness, pain and in one case, amputation. This amount of morbidity was of concern and as a result, a new surgical technique was adopted for the recipient. In the new procedure, the renal artery is anastomosed end-to-side to the caudal aorta (proximal to the caudal mesenteric artery), and the renal vein is anastomosed end-to-side to the caudal vena cava. Partial occlusion clamps are used to obstruct blood flow in both the aorta and the caudal vena cava. Windows are created in both vessels that match the size of the renal artery and vein, respectively. Similar to the other technique, 8-0 nylon is used for the arterial anastomosis and 7-0 silk for the venous anastomosis. Once the vascular anastomosis is finished, a ureteroneocystotomy is performed using a technique to appose ureteral and bladder mucosa. Prior to closure, a biopsy of one of the native kidneys is taken and a gastrostomy or esophagostomy tube placed to aid in nutritional support. Finally, the allograft is pexied to the abdominal wall. If the kidney is placed in the iliac fossa, 2 simple interrupted sutures of prolene are placed along the greater curvature of the graft. If the kidney is transplanted onto the aorta and vena cava, a musculoperitoneal flap is elevated from the adjacent body wall and sutured to the renal capsule using 4-6 interrupted sutures of prolene. Mannitol (1g/kg IV) may need to be given to the recipient prior to closure. The native kidneys are usually left in situ to act as a reserve if graft function is delayed. The native kidneys can be removed at a later time if warranted. Postoperative care and perioperative complications The key to postoperative care is minimal stress and handling of the patient and keeping the patient warm. The recipient is administered balanced electrolyte solutions until water and food are accepted. Packed cell volume, total protein, a renal panel and blood cyclosporine levels are checked every 2-4 days. Antibiotics are administered until the feeding tube is removed. Voided urine is collected daily to assess urine specific gravity. During the first 48 hours, blood pressure is monitored every 1-2 hours for the development of hypertension. If the systolic blood pressure is equal to or greater that 170mmHg, hydralazine (2.5mg) is administered subcutaneously. The hydralazine dose can be repeated if the systolic pressure hasn't decreased within 15 minutes. If the cat is refractory to hydralazine, acepromazine (0.005mg/kg IV) has been administered. During the perioperative period, the most common complications seen over the past 17 years involved ureteral, pedicle, and central nervous system complications. Prior to 1992, a "drop in" type of ureteroneocystotomy was performed. Approximately 30% of the cats were developing ureteral obstructions 5-10 days postoperatively from granuloma formation at the ureteroneocystostomy site. The cat would initially be doing well and then start to do poorly. A falling specific gravity and a rising creatinine would accompany the clinical signs. Diagnosis of ureteral obstruction was made via ultrasonographic examination of the ureter and kidney. A second surgery was needed to re-implant the ureter. With the change in surgical technique at the ureteroneocystostomy site, this has no longer been a problem. Prior to 1991, a nephropexy was not performed. Two cats had renal torsions and 2 cats had tearing of the vascular pedicle. With the old surgical technique, 2 sutures were adequate to maintain the kidney in the iliac fossa. When the new surgical technique was adopted, this pexy technique wasn't adequate and two cats developed renal torsions of their allograft. Currently, the allograft is placed in a musculoperitoneal pocket along the body wall. Probably the most frustrating complication encountered during the perioperative period were central nervous system complications. Many variables were evaluated including the cyclosporine medication, the degree of azotemia, cholesterol and magnesium levels, osmolality, hypertension and erythropoietin. The variable that seemed to be most significant in these cats was hypertension. Postoperatively, many of the cats were becoming severely hypertensive (systolic >200), even if not hypertensive pre-operatively. During these episodes, the cats would begin to seizure and these seizures were not controlled well with anticonvulsants. Once treatment was initiated prophylactically (systolic >170) with subcutaneous hydralazine, the incidence of these complications dropped significantly. Long-term management and complications Cats are discharged from the hospital when graft function is determined to be satisfactory and trough whole blood levels of cyclosporine are stable. Delayed graft function may occasionally occur due to the shock of ischemia and reperfusion injury. If ultrasonographic examination of the kidney reveals good cortical blood flow, the kidney will probably function. If the transplanted kidney fails to function, the kidney should be biopsied prior to re-transplantation. Initially, the cat is examined once a week until the cyclosporine blood levels are stable. During each exam, clinical pathological assays are performed including packed cell volume, total protein, plasma creatinine, blood urea nitrogen and phosphorus, a cyclosporine level and a urinalysis if a urine sample is available. The intervals between veterinary visits are increased once the cat stabilizes. It is recommended that a complete blood count and serum chemistry panel be performed every 3-4 months and an echocardiography performed every 12 months. Renal complications following transplantation have included renal rejection, hemolytic uremic syndrome, oxalate nephrosis and renal failure. Both acute and chronic rejection are seen in the feline transplant recipient. With acute rejection, loss of function of the affected organ is usually seen in 7 to 21 days. Histopathological examination of the organ shows mononuclear leukocyte infiltration of the tissue, with loss of normal structure. Suspected acute rejection episodes are treated with intravenous administration of cyclosporine (6.6mg/kg/24hr over 4-6 hrs) and prednisolone (10mg/kg BID IV). Chronic rejection is characterized by gradual loss of organ function over months to years, often without evidence of a rejection episode. Kidneys undergoing chronic rejection show severe narrowing of numerous arteries and thickening of the glomerular capillary basement membrane. Hemolytic uremic syndrome (HUS) in human transplant patients may occur secondary to immunosuppressive drugs, vascular rejection or recurrence of the original disease. Three feline transplant recipients were dignosed with HUS secondary to cyclosporine therapy. Complications have also occurred possibly secondary to immunosupressive therapy. These have included chronic urinary tract infections/pyelonephritis, fungal infections, toxoplasmosis, FeLV infection ,diabetes and neoplasia. Bacterial urinary tract infections in the transplant patient cause direct morbidity and mortality due to the infection itself, and may also activate the rejection process. Of ~150-200 cats, five cats broke with systemic toxoplasmosis and 4 cats developed diabetes 2-6 months after being on immunosupression. Three cats that tested negative for FeLV prior to transplantation became FeLV+ after transplantation and immunosupression. Fifteen cats have developed various types of neoplasia including gastrointestinal lymphoma, multicentric lymphoma, anaplastic round cell tumors and squamous cell carcinoma. Conclusion Renal transplantation offers a unique method of treatment for renal failure in cats. Presently, 90% of cats recover sufficiently and will go home following renal transplantation, and approximately 60-70% of the cases are alive and continuing to do well at 1 year after transplant. Survival times are steadily improving as more patients have been treated, problems recognized, and complications avoided. Clients who are interested in renal transplantation for their pet need to understand the risks and that it is a lifetime commitment for the life of the animal. Surgical Approach to Feline Urolithiasis Introduction At the University of Pennsylvania, we are seeing an increasing number of feline patients present with calcium oxalate nephroliths and/or ureteroliths. In many cases, the ureteroliths are causing partial or complete ureteral obstructions. According to the Minnesota Urolith Center, the incidence of feline calcium oxalate uroliths has been steadily increasing. In 1984, calcium oxalate uroliths comprised approximately 4.9% of feline uroliths submitted. In 1999, this number of calcium oxalate submissions increased to 55%. The cause of feline calcium oxalate urolith formation has not been clearly established. It has been suggested that dietary modification that has been recommended to prevent struvite urolithiasis in cats such as low magnesium, acidifying diets may predispose patients to the formation of calcium oxalate stones. Although medical management of struvite urolithiasis has proven to be successful, medical protocols that will promote dissolution of calcium oxalate uroliths are currently unavailable. Both monohydrate and dihydrate uroliths have been diagnosed in the cat and can lodge in the kidney, ureters, bladder, urethra or can be present in several parts of the urinary tract simultaneously. It is not clear if calcium oxalate stones lodged in the kidney or ureter will migrate into the bladder. Obviously removing stones from the bladder is far more straightforward than removal from the ureter or kidney. Anecdotal evidence suggests that some stones will eventually pass into the bladder. The author is aware of one case of a calcium oxalate ureterolith that passed into the bladder after three months of observation. Additionally, the author has seen a few cats with calcium oxalate stones lodged in the ureter pass into the bladder following fluid therapy. In one report of 11 cats with ureteral calcium oxalate stones, however, imaging studies were performed over periods of 11 to 42 days and no stone migrated in any of the cats over these time periods. Given this uncertainty, it is not always clear how long one should wait to address either renal or ureteral uroliths. Surgery is indicated in cases of ureteral obstruction, known impairment of normal renal function or the presence of a secondary infection that doesn't respond to medical therapy. Factors that also need to be considered with regards to prognosis include the function of the contralateral kidney and the overall health of the patient. The ability of the feline kidney to recover from partial or complete outflow obstruction is unknown. Recovery of renal function depends on the severity and duration of the obstruction and the presence of pre-existing renal disease. Unfortunately, in cases of unilateral ureteral obstruction, a diagnosis may go undetected if function in the opposite kidney is normal. Clinical presentation and investigation Cats with uroliths affecting the kidney and ureter can present asymptomatic or with non-specific clinical signs including lethargy, weight loss, anorexia, vomiting, fever and polydipsia and polyuria. Hematuria may or may not be present. Patients may also present with abdominal pain and splinting or renomegaly. Cats with cystic calculi usually present with pollakiuria, stranguria, and hematuria. Cats with urethral calculi present with signs typical of partial or complete urethral obstruction. A complete physical examination is performed, as many affected cats are older and may have concurrent disease(s). A urinalysis, complete blood count, biochemical profile, and plain abdominal radiographs are usually recommended as initial investigative steps. Uroliths are often visualized on plain radiographs, although small ureteroliths are occasionally missed. Further imaging studies including ultrasonography, excretory urography, and computed tomography are often helpful in identifying small ureteroliths as well as delineating the level of a ureteral obstruction. Kidney There are two options for removing nephroliths. A nephrotomy provides the greatest exposure of the renal pelvis and collecting duct system, but entails temporary interruption of the affected kidney's blood supply. The kidney is partially dissected from its retroperitoneal location. The renal artery and vein are isolated and temporarily occluded with Rommel tourniquets. A longitudinal incision is made with a scalpel through the convex lateral surface of the kidney. Calculi are removed from the renal pelvis and the collecting duct system, both of which are flushed with sterile saline. The nephrotomy incision is closed by approximating the two "halves" of the kidney and the renal capsule is sewn with 4/0 PDS in a simple continuous pattern. The Rommel tourniquets are released and the two "halves" of the kidney are held firmly opposed for 5 minutes. Although this technique provides more optimal surgical exposure, there may be some negative consequence to long term renal function. In a recent report, nephrotomy in normal cats gradually decreased GFR by 20% over one year. Alternatively, pyelolithotomy may be performed if the renal calculi have created dilation of the renal pelvis. This approach does not provide as good an exposure of the pelvis as a nephrotomy, but does not necessitate occlusion of the renal vasculature. To expose the pelvis, the kidney is dissected free of its peritoneal attachments and folded medially. An incision is made over the proximal ureter and pelvis and the stones are removed. A suture (3/0 to 4/0 nylon) can be passed distally to ensure that there is no obstruction of the more distal ureter. The proximal ureter and pelvis are closed with either a continuous suture pattern or single interrupted, appositional sutures using prolene, nylon or PDS. Ureter Ureteroliths are removed when they are causing a partial or complete obstruction (as visualized by dilation of the proximal ureter and renal pelvis on ultrasound) or are associated with a urinary tract infection. Ureteral surgery in cats generally requires substantial magnification. At VHUP, we tend to use 8 to 10 times magnification provided by an operating microscope. Stones in the proximal ureter are removed by ureterotomy. The ureter is closed with single interrupted sutures of 8/0 prolene or nylon. Stones lodged in the distal ureter may be removed by ureterotomy or the affected area of the ureter may be removed in toto and the distal ureter re-implanted into the bladder. To allow for re-implantation of the mid-portion of the ureter, the kidney can be mobilized from its retroperitoneal space and moved caudally towards the bladder. A temporary nephrostomy tube can be placed at surgery if urinary diversion is necessary. Bladder Cystic calcium oxalate calculi are removed by routine cystotomy. A ventral cystotomy is preferred. The calculi are removed and the bladder is flushed. The urethra is catheterized and flushed retrograde to ensure that no stones remain. The bladder is closed with single interrupted appositional sutures of 4/0 PDS. Urethra Until recently, the majority of male cats presented for urethral obstruction had struvite plugs obstructing the urethra. In these cases, the cat was stabilized, unblocked, the bladder flushed, and medical management instituted. With the increasing incidence of calcium oxalate urolithiasis, it is important to rule out urethral and cystic calculi in male cats with urethral obstruction. This necessitates at least abdominal radiographs in cats with urethral obstruction. If this investigation is not performed, it is likely that any urethral calcium oxalate calculi pushed back into the bladder will migrate and re-obstruct the cat when the urinary catheter is removed. Radiographs are also carefully scrutinized for evidence of renal or ureteral calculi. Cystic calcium oxalate calculi are removed via a ventral cystotomy. Given the poor success of medical management in preventing calcium oxalate urolith formation in cats, recurrence of stones is quite possible. Perineal urethrostomy is being revisited as a treatment option to possibly prevent urethral obstruction. It is difficult to make firm recommendations on when perineal urethrostomy should be considered as it is not clear what percentage of cats with calcium oxalate stones will have recurrence and whether perineal urethrostomy will prevent obstruction in all cases. In some cats with cystic calculi, the veterinarian must decide between a simple cystotomy and a cystotomy combined with a "prophylactic" perineal urethrostomy. To perform a perineal urethrostomy, the patient is placed on a rectal stand and a purse string suture placed in the anus. An elliptical incision is made from just dorsal to the scrotum to ventral to the prepuce. The penis is mobilized using blunt and sharp dissection. The ischiocavernosus and ischiourethralis muscles are cut and the ventral ligamentous attachments severed. The retractor penis muscle is excised from the dorsal surface of the penis to the level of the bulbourethral glands. A tom cat catheter is placed and the urethra incised to just cranial to the bulbourethral glands. The urethral mucosa is then sutured to the skin using 4-0 or 5-0 Ethilon or Prolene. In some cases that are extremely unstable, the placement of a temporary cystostomy tube needs to be considered. In summary, the incidence of feline calcium oxalate uroliths is increasing. Nephroliths and ureteroliths should be removed if they are associated with infection or obstruction of urine outflow. Ureterotomies require substantial magnification for accurate suturing. The increased incidence of lower urinary tract stones means that the traditional approach to blocked cats should change to include screening abdominal radiographs. The effectiveness of perineal urethrostomy for preventing calcium oxalate stone obstruction of the urethral has not been determined. Urinary Tract Trauma Trauma can involve the kidneys, ureters, bladder or urethra. Urinary tract trauma can be associated with automobile accidents or falls, penetrating wounds secondary to bites and penetrating foreign bodies, and forceful catheterizations. The kidneys and ureters are considered retroperitoneal and the bladder and proximal urethra are considered intraperitoneal. Because of their retroperitoneal location, the kidneys and ureters are less commonly damaged when compared to the bladder and urethra. The distinction between the retroperitoneal vs the intraperitoneal space is an important concept to understand when evaluating these patients since the site of trauma can often effect the animal's clinical presentation and, as a result, the ability to make a prompt and accurate diagnosis. A diagnosis of urinary tract trauma is based on history, physical examination, clinical pathological findings, evaluation of peritoneal fluid (if present), abdominal radiographs, abdominal ultrasound and contrast studies. Not only is it important to make a diagnosis, but the aim is also to determine the location of urinary leakage. Initial stabilization Depending on the time delay until diagnosis, many patients will have electrolyte and acid base abnormalities which need to be corrected as much as possible prior to surgery since these changes can make them poor anesthetic candidates. Urinary leakage can result in dehydration, azotemia, hyperkalemia, acidosis and hypovolemic shock. The rate of fluid administration as well as the type of fluid therapy should be based on a patient's specific needs. Although potassium free solutions such as 0.9% saline are recommended, a balanced electrolyte solution such as Normosol-R will correct hypovolemia and not contribute substantially to the serum potassium on an acute basis. Dogs are typically started at a rate of 60-90ml/kg/hr and cats at a rate of 40-60ml/kg/hr. The patient is then reassessed halfway through their initial fluid bolus and the rate adjusted accordingly. Additionally, these patients need to be evaluated very carefully for other systemic injuries. If enough force was present to cause trauma to the urinary tract, there is a reasonable chance that other organ systems may have been affected. Along with trauma to the urinary tract, these patients may present with a life threatening bleed associated with splenic or hepatic trauma as well as respiratory distress associated with thoracic trauma. Thoracic radiographs should be performed on any trauma patient to rule out pulmonary contusions, rib fractures as well as a possible diaphragmatic hernia. An ECG should be placed and if hyperkalemia is present, it should be treated accordingly. Cardiac arrhythmias are first apparent at potassium levels of 8mmol/L when the P-R interval becomes prolonged. As the hyperkalemia becomes more severe, the QRS complexes become wider, the T waves become taller and the P waves flatten and eventually disappear. In addition to the intravenous fluid therapy, treatment for hyperkalemia often includes intravenous 10% calcium gluconate (50-100mg/kg given slowly over 5 minutes with continuous ECG evaluation) and/ or regular insulin (.1-0.25 U/kg) and dextrose (1-2 g/unit of insulin). In patients that are severely acidotic, sodium bicarbonate can be administered. The recommended dose of sodium bicarbonate administration is 0.3 X base deficit X body weight (kg). One half of the dose is given slowly IV over 15 to 30 minutes and then the acid base status of the patient is reassessed. In some patients temporary peritoneal dialysis or urinary diversion may be necessary. To perform peritoneal dialysis, the caudal abdomen is prepared for aseptic surgery and a local anesthetic is infused. A small stab incision is made in the caudal abdomen and the peritoneal catheter introduced. The catheter is advanced off of the stilette, sutured to the ventral abdomen and connected to a sterile closed urine collection system. Kidney Isolated renal trauma is often difficult to diagnose. Historical information in conjunction with the presence of gross or microscopic hematuria and pain on palpation in the sublumbar region may be suggestive of a primary renal injury, however are not pathognomonic for the condition. Abdominal ultrasound may reveal some fluid accumulation surrounding the kidney in the retroperitoneal space. Occasionally, renal injury can be confirmed by excretory urography, however often the diagnosis is made during exploratory surgery. Treatment of renal trauma is dictated by the extent of injury. Lacerations of the kidney can be sutured, however if severe injury has occurred a partial or complete nephrectomy may be necessary. Ureter Unilateral ureteral tears secondary to trauma are difficult to diagnose if urine accumulation is confined to the retroperitoneal space. Clinical signs in these patients are often vague and may include lethargy, dehydration, sublumbar pain, vomiting, anorexia and pyrexia. Clinicopathological findings in these patients are typically normal. Abdominal radiographs often reveal a loss of retroperitoneal detail and an increased size of the retroperitoneal space. Abdominal ultrasound may identify fluid accumulation in the retroperitoneal space. If both ureters are disrupted, signs of acute azotemia will occur. If urine leakage enters the peritoneal cavity, a uroperitoneum will develop. Excretory urography is beneficial in cases of both unilateral and bilateral ureteral abnormalities. Treatment options for ureteral abnormalities is often dictated by patient stability, function of the remaining kidney and location of the injury. Options include primary repair, ureteral reimplantation and ureteronephrectomy. In some cases a percutaneous nephrostomy tube may be beneficial in diverting urine away from the surgery site. Bladder Traumatic bladder rupture is the most common cause of a uroperitoneum. Traumatic bladder rupture can also occur secondary to aggressive palpation or poor catheterization technique. Urine leakage into the peritoneal cavity results in uremia, dehydration, hypovolemia and death if untreated. It is important to remember that patients may urinate normally if a small leak is present and the ability to retrieve fluid on bladder catheterization does not preclude the diagnosis of a ruptured bladder. Additionally, the inability to palpate a urinary bladder as well as the presence of a fluid wave is supportive of a diagnosis of uroperitoneum. To diagnose a uroperitoneum, the concentration of the creatinine and urea in the fluid retrieved on abdominocentesis should be compared with that of the peripheral blood. The urea molecule is small and rapidly equilibrates across the peritoneal membrane. The creatinine molecule is a larger molecule and diffuses more slowly. As a result, in a patient with a uroperitoneum, the creatinine level in the abdominal fluid is higher than that of the serum. Abdominal radiographs in these patients may reveal a loss of abdominal detail as well as the absence of the urinary bladder. Positive contrast cystography, with leakage of contrast material out of the bladder, provides a diagnosis of a ruptured bladder as the cause of the uroperitoneum. Treatment of a patient with a bladder rupture includes stabilization of the cardiovascular system, treatment of any life threatening metabolic abnormalities and then definitive surgical repair of the bladder. An exploratory laparotomy is performed and the damaged area of the bladder is debrided and sutured in either a single interrupted appositional pattern or a two layer closure. Because of the chemical peritonitis that can occur with urine leakage, copious lavage of the abdominal cavity is recommended prior to closure. Urethra Both partial and complete urethral tears can also occur secondary to trauma. Urethral lacerations and ruptures are associated with pubic fractures, fractures of the os penis, penetrating wounds and iatrogenic injury secondary to urethral examination, catheterization and surgery on or adjacent to the urethra. Clinical signs will vary depending upon the location of the rupture. A proximal urethral rupture can result in a uroperitoneum and clinical signs similar to a patient with a ruptured bladder. A distal urethral tear will result in urine leakage into the surrounding soft tissues. This is manifested as swelling, pain and cellulites in those areas. A diagnosis of urethral rupture is confirmed by retrograde urethrography. To accurately determine the site of rupture, positive contrast material is injected slowly into the urethra using fluoroscopy. Surgery for urethral trauma often includes primary repair and urinary diversion. Urinary diversion can be accomplished by a cystostomy tube or by an intraurethral catheter. In some cases, urinary diversion +/- a urethral stent may be performed without primary repair. Primary suture repair is the best treatment for complete urethral rupture or avulsion of the urethra from the bladder. |
