13 Equine Urinary Tract Surgery

Equine Urinary Tract Surgery

• Recognition and diagnosis of urinary bladder calculi is necessary.
• The treatment options for urinary calculi must be described.
• Uroabdomen, patent urachus, and infected umbilicus should be recognized, diagnosed, and treated.

Urinary system: Ureters

• Ureters course along the dorsal body wall and then turn laterally at the pelvic brim to the genital fold.
• They enter the bladder dorsally at the trigone.
• Ureters facilitate the peristaltic transportation of urine.
• Few indications exist for intervention in the kidney or ureter in the horse.
• Intervention may be needed for ureteroliths, ectopic ureter or renal failure biopsy.
• Kidney/ureter intervention is uncommon in horses.

Urinary system: Bladder

• The urinary bladder is highly distensible and in the ventral pelvic canal.
• It is retroperitoneal, except for the apex, which has its origin in the urachus.
• The bladder wall is comprised of the detrusor muscle.
• The detrusor muscle has an outer longitudinal and inner circular layer.
• Fibers in the detrusor muscle become longitudinally oriented dorsally near the bladder neck.
• The bladder wall is a weak point and wear rupture almost always occurs.
• Lateral ligaments are remnants of the umbilical arteries, which commonly get infected in foals.
• There is also a middle ligament that is of little clinical relevance.

Urinary system: Urethra

• The urethra courses through the ventral pelvis.
• It opens for ducts of the sex glands.
• In females, the urethra exits within the vestibule.
• The urethra bends ventrally at the caudal pelvic brim.
• The urethra has a diverticulum.
• In males, the urethra continues inside the penis and is surrounded by erectile tissues.

Urinary Bladder Calculi

• Hematuria, stranguria, and pollakiuria are clinical signs of urinary bladder calculi.
• Urine scalding is rare, but can happen in mares.
• Diagnosis of Urinary Bladder Calculi occurs by rectal palpation or endoscopy of the bladder.
• Further diagnostics include serum chemistry (creatinine and BUN) and ultrasound of both kidneys.
• Males are more commonly affected by Urinary Bladder Calculi.
• There are no published geographic predilections.
• It’s subjectively more common in the West/Pacific NW.
• High calcium diets are suspected of causing Urinary Bladder Calculi.
• The etiology behind Urinary Bladder Calculi is not truly known.
• Calcium carbonate is the most common composition.

Treatment Options

• Stones can be removed whole by ventral midline incision, or by parainginal approach or laparoscope (difficult and time consuming).
• Calculi can also be fragmented and removed, either through perineal urethrotomy, or by one of many fragmentation methods.

Urinary Calculi- Standing Removal

• Perineal urethrotomy and lithotrite or osteotome can be utilized in standing removal.
• Electrohydraulic lithotripsy, ballistic shockwave lithotripsy, and pulsed dye laser lithotripsy are all options.
• A Holmium:YAG laser can also be used.

Endoscopic-Assisted Electrohydraulic Shockwave Lithotripsy

• During Endoscopic-Assisted EH Lithotripsy, an endoscope is inserted via the urethra into the bladder.
• The electrohydraulic shockwave fiber is inserted via the biopsy channel.
• It fragments stones into pieces smaller than 1cm.

Urethral Calculi

• Suspect a confirmed urinary obstruction by palpation of enlarged urinary bladder on rectal palpation.
• Urethral endoscopy is the next step.
• Calculi may be palpable percutaneously.
• Attempt to determine are there other stones in the bladder via rectal palpation and/or ultrasound.
• If there is no other calculi: perform urethrotomy, distend and massage it out.
• If there are more calculi, retropulse them into bladder and remove all from bladder, or perform urethrotomy.
• Do not use a catheter to push the calculi back into the bladder - relieve the obstruction another way.
• Doing so puts the calculi in a more difficult place to access.

Prolapsed Bladder

• Prolapsed Bladder is Secondary to straining.
• Diagnosis is by physical exam.
• Perform a caudal epidural.
• Apply table sugar to shrink it.
• Manually massage back into place.
• Prognosis depends on why prolapse happened and the duration of the prolapse.

Uroabdomen in Foals

• Uroabdomen is more common in colts.
• Colts are born normal
• Typically presents within first 24-48 hours of life.
• Frequent urination is observed.
• Signs are progressive and include lethargy, depression, anorexia, and abdominal distention/colic.
• Ureters are rare, bladder dorsal neck is the most common site.
• Foals can still urinate normally even with a ruptured bladder.
• Horses eat a diet high in potassium and low in sodium.
• Horse kidneys excrete lots of potassium and conserve sodium.
• It is a medical, not surgical, emergency.
• Composition of urine includes: high BUN, creatinine, and K+, and low Na+ and Cl-.
• The systemic clinical picture includes: increased BUN, creatinine, and K+, and low Na+ and Cl-.
• Electrolyte abnormalities are corrected before surgery.
• Methods of confirming uroabdomen: ultrasound, abdominal radiographs, contrast radiography, and abdominocentesis. In abdominocentesis, the fluid smells like urine. Creatinine is also higher than serum and at a 2:1 peritoneal cavity to blood ratio.
• Electrolyte composition of plasma and interstitium is identical. With bladder rupture, the electrolyte balance is disrupted.
• Medical management includes: CBC, serum chemistry, and blood gas analysis must be done.

Correcting Uroabdomen

• The abdominal fluid must be drained.
• Replace plasma volume.
• Correct acid base abnormalities and correct electrolyte disorders (low Na+, low Cl-, and high K+).
• Normal saline or double strength saline may be used.
• Drain abdominal fluid with a teat canula, a foley catheter, a chest trocar, or a peritoneal dialysis catheter.
• If Continuous drainage is required the catheters tend to plug with omentum.

Infected Umbilical Remnants / Infected Umbilicus

• Enlarged umbilicus is often present with purulent discharge.
• The umbilicus is a portal for entry for systemic infection.
• Ultrasound is indicated to determine which structures are involved.
• The umbilical vein should be less than 1 cm.
• There is no clear consensus on whether they should be managed medically or surgically.

Patent Urachus

• Patent Urachus can be evident by urine leaking from umbilicus or umbilicus may just be moist/full stream urine.
• It may be congenital, or acquired in septic foals that develop it at 1-2 weeks of life.
• For congenital cases, attempt medical management via dipping umbilicus in iodine. Placing an indwelling foley catheter in bladder for continuous bladder drainage allows some to heal without surgery. Also consider umbilical remnant resection.
• For Acquired cases, dipping umbilicus is usually ineffective but should be done to prevent ascending infection. Consider an indwelling foley catheter in bladder for continuous bladder drainage to allow to heal without surgery. Or umbilical remnant resection.

Umbilical Remnant Resection

• Indicated when required for midline celiotomy in a neonate for any reason, for patent urachus, for umbilical/urachal infection, or for urachal/urachal tear.
• Perform a ventral midline incision.
• Ligate the umbilical vein and the umbilical artery.
• Amputate the urachus.
• Close the bladder with an inverting closure.