A Lecture Summary from a lecture by Dr. James King

Introduction

This lecture provides a practical framework for managing urinary tract surgery in dogs, with particular emphasis on acute urethral obstruction. The content addresses the reality that many veterinarians face: performing these surgeries when referral is not an option – and aims to build confidence through clear anatomical guidance, procedural tips, and decision-making strategies. 

The lecture covers the full spectrum from initial stabilisation through to surgical technique and postoperative management, with a strong focus on knowing when to proceed, when to pause, and how to avoid common pitfalls. The emphasis is on practical tips gained from clinical experience, recognising that much of urogenital surgery relies on anecdotal evidence and established techniques rather than extensive new literature.

1. Pre-Surgical Considerations: Urolith Types and Client Guidance

Understanding the type of urolith is essential before surgery, as it guides client expectations and long-term management:

• Struvite stones are heavily associated with infection and alkaline urine pH, and they can often be managed medically with appropriate antibiotics and dietary therapy, particularly when infection is controlled
• Calcium oxalate stones are typically associated with more acidic urine and may indicate underlying endocrinopathies such as hypercalcaemia or Cushing’s disease. Identifying these conditions is critical because removing the stones alone will not prevent recurrence without addressing the underlying metabolic issue
• Urate stones are classically associated with Dalmatians and portosystemic shunts. Dietary control after surgery is unbelievably important to avoid recurrence
• Cystine stones are most common in entire male dogs, particularly bulldogs, and are hormonally dependent. Castration is an important step in preventing recurrence. Owners often resist this initially but frequently agree when stones recur

Important radiographic consideration: The traditional dogma that struvite and calcium oxalate stones are radiopaque while urates and cystines are radiolucent is not consistently accurate. Urates and cystines can absolutely be radiopaque due to varying calcium compositions. Relying purely on radiopacity to guide client discussions can lead to surprises.

The key message: Consider why the stone formed before cutting it out. This allows appropriate client guidance about ongoing management and sets realistic expectations about recurrence risk.

2. Stabilisation and the “Take a Breath” Principle

Acute urethral obstruction is an emergency, but once relieved, the patient is no longer an emergency:

Initial approach:

• Obtain IV access and stabilise with fluids before attempting to pass a urinary catheter
• Perform minimum database: CBC, biochemistry, and blood gas if available. These may reveal postrenal azotaemia, electrolyte derangements (particularly hyperkalaemia), and calcium abnormalities that must be addressed before anaesthesia
• Relieve the obstruction as soon as the patient is stable enough

Critical principle: Once the obstruction is relieved and an indwelling catheter is placed, the patient is no longer an emergency. This allows time to:

• Treat underlying infections
• Resolve metabolic derangements
• Wait for appropriate staffing and resources
• Plan surgery thoughtfully rather than rushing

The exception: If the obstruction cannot be relieved, emergency surgery with urethrotomy may be necessary – but this is uncommon (only encountered twice in the speaker’s experience).

Alternative options when catheterisation fails:

• Rectal occlusion technique/uroretrohydropulsion: An assistant places a finger in the rectum and pushes down on the pelvic symphysis to occlude the urethra. The surgeon infuses a 50/50 mixture of sterile lubricant and saline with firm pressure. When the assistant releases, the pressure differential shifts the obstruction through. This can be incredibly effective
• Cystocentesis: Can buy time in desperate situations, but be mindful that a chronically distended bladder wall may be fragile and at risk of rupture

3. Diagnostic Imaging Essentials

Radiography is the cornerstone of preoperative evaluation, but the most common mistake is not including the perineum:

• Always include the perineum on radiographic images – as stones lodged in the distal urethra will be missed entirely if imaging stops at the pelvis
• Contrast urethrography is invaluable when radiolucent stones are suspected or when stones cannot be visualised on plain radiographs

Technique for contrast urethrography:

• Use Iohexol (approximately 0.5 ml/kg undiluted, typically 350 mg iodine/ml)
• Clip and prepare the prepuce with aqueous chlorhexidine first – while not a sterile procedure, contamination should not be made worse
• Pass a rigid catheter and pinch the end of the penis firmly. This is essential to prevent contrast spraying everywhere and allows retrograde filling
• The contrast study will highlight radiolucent stones (appearing as filling defects) and can identify the precise location of obstruction

Normal contrast study suggests functional obstruction such as reflex dyssynergia from lumbosacral disease (L7-S1 disc disease), which causes dribbling without mechanical obstruction.

4. Surgical Approach and Bladder Anatomy

The ventral midline approach with paraphimosis extension is essential for adequate visualisation:

Surgical preparation:

• Large abdominal clip – give yourself plenty of room
• Sterile prep including flush of the prepuce/vulva
• Have rigid catheters available in multiple sizes (6, 8, and 10 French)
• Use only monofilament, absorbable suture material – never multifilament or braided
• Keep warm saline, plenty of sponges, and pathology pots ready
• Perioperative antibiotic prophylaxis: cefazolin at 30 mg/kg every 90 minutes (updated ADAP guidelines)

Paraphimosis extension:

• Extend the midline incision through the preputial muscle to get as far caudal as needed
• This provides superior visualisation and reduces the risk of abdominal contamination
• The improved access makes surgery more accurate and efficient

Bladder anatomy landmarks:

• The ventral median ligament is the key landmark – it indicates you are safely away from the ureters (which lie in the lateral ligaments dorsally)
• The trigone contains the neurological supply to the bladder; stay away from this region
• Use Babcock forceps to grasp the bladder apex and pull it rostrally – these can be towel-clamped to drapes if working alone
• Stay sutures further aid retraction and exposure

Cystotomy incision:

• Make the ventral midline cystotomy through the ventral median ligament
• This ensures you stay away from ureters and the trigone

5. Cystotomy Technique: Stone Removal and Closure

Stone removal requires systematic lavage and careful attention to preventing stone loss:

Preventing stone loss:

• Pack lap sponges generously around the surgical site, as stones will otherwise disappear into the abdomen or subcutaneous space
• As soon as the cystotomy is opened, stones will drain down toward the trigone. Do not assume they are all removed when the visible ones are gone

Lavage technique:

• Lavage both antegrade and retrograde until fluid passes clearly and no more stones emerge
• Use a urinary catheter to flush from both directions
• Dalmatians and dogs with heavy stone burdens can have surprising numbers of stones – they just keep coming!

Useful instruments:

• A blunt spoon (sterilised) is highly effective for scooping stones, and is much more efficient than curettes or forceps
• Suction can help, but turn the suction down to avoid trauma to the mucosa

Closure considerations:

• Single layer, full thickness closure is recommended. Include the submucosa, which provides the strength-holding layer
• Simple continuous suture is preferred; simple interrupted may be useful for severely thickened bladder walls but is not necessary in most cases
• Suture choice: Monocryl is the speaker’s preference due to rapid absorption (bladder heals within 5–7 days). Longer-lasting sutures like PDS are unnecessary and may provide a nidus for crystal formation. Despite textbook concerns about rapid absorption in infected urine, clinical experience does not support this as a problem

Leak testing:

• Not routinely performed. Remember that all soft tissue repairs will leak if pressure is high enough, and intraoperative testing creates supraphysiological pressures that can disrupt initial fibrin sealing
• If concerned about suture spacing, place a couple of extra sutures rather than performing a leak test
• Some apparent “leakage” may actually be blood from suture bites, not urine

Post-closure checks:

• Ensure no stones are left in the subcutaneous space or abdominal cavity – postoperative radiographs will otherwise be difficult to interpret
• Collect diagnostic samples: bladder wall biopsy (full thickness, taken before cystotomy) often yields more accurate culture results than urine alone
• Always obtain a postoperative radiograph

6. Special Considerations: Nephroliths and the “Fix Everything” Trap

A common surgical trap is the desire to fix every problem simultaneously:

The case example of a 5-year-old male entire Pug illustrates this perfectly:

• Presented with urethral obstruction, severe bacteriuria, pyuria, and azotaemia
• Radiographs showed a massively dilated bladder with multiple stones AND a large nephrolith
• The urine was alkaline, suggesting struvite stones

The decision-making process:

• The life-threatening problem was urethral and bladder obstruction that required cystotomy
• The nephrolith, while large, had likely been present for some time and was not immediately life-threatening
• Nephrotomy would significantly reduce glomerular filtration rate in that kidney, representing a major functional loss
• Medical dissolution was a better option: treat the infection and use a urinary diet

Key takeaway: Do not develop tunnel vision thinking everything must be surgically fixed at once. Address the immediate life-threatening issues first, treat medically where appropriate, and monitor. The case discussed in the lecture was stabilised over 36 hours (with the obstruction relieved) before proceeding to surgery and went home the next day. Even without 24-hour care, this approach is feasible: Relieve obstruction, stabilise, and plan surgery when ready.

7. Urethrotomy and Urethrostomy

Urethrotomy is doable but requires familiarity with anatomy and realistic expectations about bleeding:

Indications for urethrotomy:

• When stones cannot be retrograde passed (often due to fibrous adhesions)
• When a catheter cannot be passed despite all efforts
• Contrast studies help locate radiolucent stones

Common location: Most stones get stuck at the base of the os penis. The prescrotal urethrotomy is therefore the most common approach. Perineal urethrotomies are possible but more challenging.

Surgical technique:

• Ventral midline approach as normal
• Use small Gelpi retractors to retract subcutaneous tissue
• The retractor penis muscle is pushed aside
• The urethra appears as a distinctly purple structure; a catheter guides you to the location
• Use an 11-blade scalpel (not a 15-blade) and cut superficially, extending with scissors if needed
• Expect significant bleeding—this is normal. Do not use cautery; use gentle damp swabs and turn suction down to avoid mucosal trauma

Closure and management options:

Approach	Pros	Cons
Leave open	Reported technique	Bleeds heavily, messy, urine scalding
Leave open with catheter	Catheter directs urine	Leakage into subcutaneous space causes cellulitis
Close primarily (speaker’s preference)	Cleaner, less scalding, better management	Requires fine suture technique (5-0 or 6-0 Monocryl or PDS)

Suture choice for urethra: 5-0 or 6-0 Monocryl with a small needle is excellent for urethral surgery.

Catheterisation after urethrotomy:

• The speaker prefers NO urinary catheter if closure is satisfactory
• If significant trauma occurred, leaving a catheter for a couple of days may be appropriate
• There is no right or wrong, with both approaches having their advocates

Expected outcome: Some degree of stenosis will form regardless of technique, but this does not necessarily cause functional problems for the dog. However, it means that if stones recur, they may not pass as easily, so this should be discussed with owners.

Summary: Practical Decision-Making Flow

1. Stabilise – IV fluids, minimum database, treat derangements
2. Relieve obstruction – pass catheter; use rectal occlusion technique if struggling
3. Take a breath – once unobstructed, the patient is no longer an emergency
4. Image thoroughly – always include the perineum; use contrast if needed
5. Plan surgery – consider urolith type and underlying causes; address life-threatening issues first
6. Surgical technique – midline approach with paraphimosis extension; ventral cystotomy; single-layer continuous closure with Monocryl; no leak test
7. Postoperative care – postoperative radiograph; no routine catheterisation; supportive care
8. Client guidance – explain recurrence risk and long-term management needs upfront