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Surgical upper urinary tract disease in dogs (Proceedings)

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Aug 01, 2010

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.