Preneal urethrotomy in cat according to fossam
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The medical library contains human medical textbooks only — there are no veterinary textbooks. The query refers to "Fossam" which is likely Fossum (Theresa Welch Fossum), author of the classic veterinary surgery textbook Small Animal Surgery. This is a veterinary procedure not covered in the library.
I'll answer from my knowledge of Fossum's description of perineal urethrotomy in cats.
Perineal Urethrotomy in Cats (Fossum — Small Animal Surgery)
Indications
- Recurrent urethral obstruction not manageable medically
- Urethral stricture
- Traumatic urethral injury in the perineal region
- Inability to pass a urethral catheter past the penile urethra
Relevant Anatomy
The feline urethra narrows significantly at the penile urethra (the os penis region), which is the most common site of obstruction. The pelvic urethra is wider. Perineal urethrotomy bypasses this narrow segment by creating a permanent stoma at the level of the wider membranous/penile urethra just caudal to the bulbourethral glands.
Patient Preparation
- Place in ventral recumbency (perineal position) with the tail elevated and secured dorsally
- Clip and aseptically prepare the perineal region
- Place a purse-string suture around the anus to prevent fecal contamination
- Empty the bladder if possible; catheterize to identify the urethra intraoperatively
Surgical Technique (Fossum's Description)
1. Skin Incision
- Make an elliptical skin incision around the prepuce and scrotum
- If the cat is intact, castration is performed first (or the scrotum and prepuce are included in the elliptical excision)
2. Penile Dissection
- Dissect the penis free from the surrounding subcutaneous tissue
- Identify and ligate the retractor penis muscle on the dorsal surface
- Identify the ischiocavernosus muscles laterally; transect them at their ischial attachments
- The corpus cavernosum attachments to the ischium (crura) are transected
3. Urethral Identification
- A tomcat catheter (3.5 Fr) is passed to identify and palpate the urethra
- Dissect the urethra free from the ventral surface of the penis, beginning distally
4. Urethrotomy
- Make a midline dorsal incision through the penis over the catheter, extending from the tip proximally
- Continue the incision into the widest portion of the urethra (proximal penile/membranous urethra), just proximal to the bulbourethral glands
- The incision should be long enough to create a stoma at least 1 cm in length to minimize stricture
- Remove the distal penis (amputate)
5. Urethrostomy (Stoma Creation)
- Suture the urethral mucosa directly to the skin using simple interrupted sutures of 4-0 or 5-0 monofilament absorbable suture (e.g., PDS or Monocryl)
- Begin suturing at the cranial apex, then the lateral margins, then complete the caudal portion
- The goal is a wide, tension-free stoma — mucosa-to-skin apposition is critical to prevent stricture
- Close remaining subcutaneous tissue and skin in routine fashion
Key Technical Points (Fossum)
| Point | Detail |
|---|---|
| Catheter use | Maintain catheter in situ during dissection to guide incision |
| Stoma length | Minimum ~1 cm wide; shorter stomas have higher stricture rates |
| Suture material | Fine absorbable monofilament (4-0 or 5-0); avoid chromic gut |
| Mucosal apposition | Must suture mucosa to skin, not submucosa to skin |
| Hemostasis | Penile erectile tissue bleeds; pressure and ligatures needed |
| Castration | Recommended concurrently if not already neutered |
Postoperative Care
- E-collar mandatory to prevent self-trauma to the stoma
- Monitor urine flow through the new stoma — should be a wide stream
- Remove skin sutures at 10–14 days
- Dietary management: increased water intake, urinary acidifying or dissolution diets (depending on crystal type)
Complications
| Complication | Notes |
|---|---|
| Urethral stricture | Most common long-term complication; due to inadequate stoma size or mucosal-skin gap |
| Hemorrhage | Common intraoperatively from penile tissue; usually self-limiting |
| Peristomal dermatitis | Urine scald; manage with hygiene |
| Bacterial UTI | Higher risk post-urethrostomy due to loss of penile defense mechanisms |
| Continued obstruction | If pelvic/bladder neck pathology not addressed |
| Subcutaneous urine leakage | From poor mucosal apposition |
Prognosis
Good for relief of obstruction. Long-term UTI rates are increased compared to intact males (~25–30%). Owners must be counseled that this procedure does not address the underlying metabolic cause (e.g., FIC, urolithiasis) and medical management remains essential.
Based on Fossum TW et al., Small Animal Surgery, 4th/5th edition — Perineal Urethrostomy in Cats.
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