Surgical upper urinary tract disease in dogs (Proceedings)

General Principles

Careful consideration of preoperative, intraoperative, and postoperative management techniques will assist in preventing complications related to anesthesia and surgery in patients with urinary tract surgical disease. Hospital acquired renal insufficiency is common in humans, seemingly less so in animals but caution is advised. Hypotension of any cause is a potential predisposing cause to renal failure.

Potential Causes of Hypotension

     • Hemorrhage

     • Dehydration

     • Ascites/Pleural Effusion

     • Anesthetic agents

     • Trauma (Shock)

Hypoperfusion may also potentiate the deleterious effects of other nephrotoxins such as aminoglycoside antibiotics, anesthetic agents, and NSAID's.

     1. Hypovolemia and electrolyte imbalance corrected PRIOR to definitive surgery. Maintenance of a normovolemic state and NORMAL urine production (0.5-1.0 ml/kg/hr) during the anesthetic episode is a goal.

     2. Administration of crystalloid fluids (LR or other balanced electrolyte solution) at rates of 10 ml/kg/hour in the normal healthy patient is routine, HIGHER rates if there is preexisting disease.

     3. Measuring urine production may be advantageous and requires nothing more than an indwelling u-cath and a closed system.

AIDS if patient is oliguric (choose one or more)

     1. Furoseamide 2-4 mg/kg bolus

     2. Dopamine 2-5 ug/kg/minute infusion, dose is critical, more is NOT better, causes vasoconstriction

     3. Mannitol 0.5 gram/kg bolus

Anemia may be associated with chronic renal failure (CRF) or secondary to specific surgical procedures such as Urethrostomy which may result in excessive bleeding. Consider Packed cells or whole blood for those animals needing surgery who have a PCV below 25.

Surgical Exposure/Anatomy- Depends Upon Which Portion Of The Urinary Tract One Wants To Expose;

     • -Cranial ventral midline from xiphoid to midway between umbilicus and pubis for upper urinary tract (kidney)

     • -Umbilicus to pubis for lower urinary tract

     • -Pubic osteotomy or ostectomy MAY be necessary to expose pelvic urethra

     • -Episiotomy for exposure of the urethral papilla in the female

     • -Balfour retractors for exposure of the abdomen extremely valuable

Use of the duodenum & mesoduodenum on the right side and the colon and mesocolon on the left side as anatomic retractors will help you in exposing the kidney/ureter on the respective side.

Renal Surgical Disease

The kidneys lie in the sublumbar region and are retroperitoneal. The right kidney is more cranial than the left and is fixed to the liver by the hepatorenal ligament. Recall that the kidneys receive large volumes of total cardiac output by the renal arteries which are direct extensions of the aorta. Reportedly, about 10-20 % of dogs have more than one renal artery on the left side. The arteries are rostral and dorsal to the respective renal veins which are easily visualized. The right kidney is closely associated with the caudal vena cava and disease (neoplasia) of the right kidney may involve the vena cava. A GLOBAL picture of renal function is obtained by blood work and BUN/Creatinine assessment, urinalysis, and urine culture.

***Functional status of an individual kidney can be difficult to determine. Excretory urography is a qualitative study of kidney filtration but is not a quantitative study. If no contrast is excreted by a kidney no function is present but if contrast is excreted we can't determine how much function is present. 2-3 mm of functional cortex is enough to consider salvage of a kidney. Renal scintigraphy is the only non-invasive technique for measuring glomerular filtration but is not widely available.

Nephrectomy

When the following unilateral pathology exists, severe hydronephrosis, neoplasia, endstage pyelonephritis, avulsion of the renal vasculature from trauma (rare) and as a salvage procedure for an animal with unilateral ectopic ureter. Correction of the ectopic ureter is PREFERABLE to nephrectomy if renal function on the affected side is normal.

Technique

     1. Expose the appropriate kidney using the duodenum or colon as described earlier.

     2. Free the kidney form its sublumbar attachment starting laterally using sharp and blunt dissection.

     3. The renal artery and vein are located on the dorsal hilus.

     4. Dissect and separate the artery and vein and doubly ligate the artery with PDS, polyglyconate, or silk. Ligate the renal vein similarly.

     5. Dissect the ureter free from its sublumbar attachments to the level of the urinary bladder and ligate as close to the bladder as possible.

This description is accurate for an animal with normal anatomy, if neoplasia is present, normal anatomy is NOT apparent and the surgeon proceeds by careful dissection of the affected kidney using ligatures and stainless steel clips for ligation.

Nephrotomy/Nephrolithiasis

Nephroliths are urinary calculi located within the renal pelvis and/or collecting diverticula of the kidney. Increase in size of a calculus may OBSTRUCT or cause compressive injury of the renal parenchyma leading to renal failure.

Nephroliths may be asymptomatic or they may produce obstruction of the renal pelvis and/or ureter.

Clinical Signs

     • Hematuria

     • Azotemia/Uremia (bilateral or unilateral and concurrent renal disease in second kidney)

     • Recurrent UTI

     • Abdominal pain

Canine nephroliths are usually calcium oxalate (40% +) or struvite (35%). Feline nephroliths are 98% + calcium oxalate or calcium phosphate.

Proper patient assessment of an animal with upper urolithiasis in addition to blood work, urinalysis, and urine culture involves either excretory urography or ultrasound examination.

Nephrolith Therapeutic Options

     1. "Watchful waiting"- Selected in the asymptomatic patient with NO evidence of OBSTRUCTION and where the stone is not growing in size. Also, the patient is treated for UTI if present.

     2. Medical Management- Dietary and appropriate antibiotic therapy MAY result in dissolution of struvite (MgNHPo4), cystine, or urate stones but therapy is prolonged.

     3. Lithotripsy (ECSWL)- Lithotripsy by external beam lithotripter is available at special sites. The advantage of this therapy is it Is non-invasive but still capable of breaking down the stone without surgical injury to the kidney.

     4. Surgical Management- Nephrotomy is indicated in those animals with remaining renal function and obstructive disease and neither lithotripsy is available and the type of stone precludes medical management. Nephrectomy may be indicated in animals with little

     5. or no function remaining in the diseased kidney.

Nephrotomy Technique

     1. Expose the right or left kidney as previously described.

     2. Temporarily occlude the blood supply to the kidney by one of the following methods.

     • -Digital occlusion by a surgical assistant

     • -Use of bulldog clamps (PREFERRED)

     • -Use of a Rumel tourniquet

     • LIMIT OCCLUSION TO 15-20 MINUTES MAX

     3. Make a longitudinal incision directly over the convex surface of the kidney; use the blunt end of the scalpel handle to bluntly separate parenchyma down to the calculus.

     4. Remove the calculus, culture the renal pelvis, flush the renal pelvis and pass a catheter into the proximal ureter.

     5. Pull the two halves of the kidney together and close the nephrotomy incision with 4/0 PDS in a continuous pattern engaging the renal capsule and small bites of parenchyma. Bites are taken close together so they don't tear out of tissue.

     6. Consider renopexy by suturing one pole of the kidney to the musculature to prevent torsion on its blood supply.

Strongly recommend against performing concurrent bilateral nephrotomy in dogs with bilateral calculi. Stage the surgeries 6 weeks apart.

Ureteral Disease

Ectopic Ureter (s)

     1. Continuous or intermittent incontinence in a young female or male dog suggests ectopic ureter until proven otherwise.

     2. 99% diagnosed in females, Huskies, West Highland, Poodles predisposed

     3. Usually NOT clinically ill (systemically) dogs, many dogs have concurrent UTI's

     4. Tentative diagnosis is made or suggested by either ultrasound examination or excretory urography.

     5. Definitive diagnosis can be made by cystoscopy or at surgery. Cystoscopy is EXTREMELY helpful both for diagnosis and surgical management. Catheterization of the affected ureter (s) makes surgical intervention easier.

     6. Most canine ectopic ureters are intramural, that is they enter the bladder in a normal location but don't have a normal opening, instead they tunnel through the wall and open downstream in the urethra or vagina. Although rarely diagnosed in cats, when they occur they are more typically extramural (they bypass the bladder.

     7. Surgical correction of an intramural ectopic ureter involves making an incision in the wall of the ureter and then suturing the ureteral wall to the bladder mucosa.

Ureteral Calculi

     1. Occasionally seen in dogs, more commonly identified in cats. Usually concurrent with renal calculi. Many cats have evidence of renal failure when diagnosed. The renal failure MAY be caused by obstructive disease or may be an independent event.

     2. Ultrasound examination often shows a dilated ureter proximal to the stone BUT in some cases the stone may NOT be causing obstruction.

     3. Medical management by fluid therapy sometimes results in stone passage into the bladder but my experience with this has not been positive.

     4. Surgical management by ureterotomy can be performed but is challenging. Ocular magnification either with 2-5x mag or even an operating microscope may be necessary.

     5. I would recommend referral to a surgeon if you feel you have a patient that will benefit from ureterotomy.