Introduction

Surgery of the external genitalia encompasses a group of fairly specific conditions that frequently require intricate surgical techniques for their repair. This presentation discusses the various organs in these groups. It includes the most common conditions affecting them and the specific surgeries that are used to correct them.

Surgery of the Female Genitalia

Mammary Neoplasia

This is one of the most common tumour presentations in older dogs and cats and accounts for 70% of all tumours in dogs and for 17% of all feline tumours. In cats, mammary tumours tend to be much more aggressive.¹ Both male dogs and cats can also develop mammary tumours, but incidence is significantly lower than in females. Animals may present with more than one lump and it is important to remember that each tumour may be a completely different histological type.

Dogs have 5 pairs of mammary glands: 2 thoracic, 2 abdominal, 1 inguinal set. In cats, inguinal glands are either absent or rudimentary, leaving them with only 4 pairs.¹ The glands are tubular-alveolar structures surrounded by a fibroelastic capsule and have a single teat duct exiting them.

Prognosis is determined by the type and size of the tumour. Tumours with a diameter larger than 3 cm in dogs (2 cm in cats) have a worse prognosis than smaller tumours. Evidence of spread to the lymphatic system, adherence to deeper tissues, ulceration of the tumour surface and rapid growth of the mass, are other indications of a poor prognosis.²

Treatment of choice in mammary tumours is surgical resection. The various categories of this are: lumpectomy (nodulectomy), simple mastectomy, regional mastectomy (en bloc resection of 2–3 glands based on their known blood and lymphatic supply) and chain mastectomy which includes the resection of all glands down one side of the mammary chain.¹

Vulvar Fold Episioplasty

This is a condition often diagnosed in Pugs and Bulldogs. Boerboels also seem to account for a high number of cases. The condition is acutely linked to obesity and is also known as a "recessed vulva." Perivulvar dermatitis, pyoderma and recurrent urinary tract infections are associated with the condition.³ Surgical correction involves a simple elliptical, full thickness incision of the skin fold dorsal to the vulva. Monofilament absorbable sutures are placed at evenly spaced intervals in the subcutaneous layers and a simple interrupted skin suture layer is used to complete the repair.^1,3

Vaginal Hyperplasia

This is a very distinctive, but uncommon condition, seen in young, female dogs during oestrus or proestrus. It results from hormonal stimulation causing oedematous swelling of the ventral floor of the vagina. It differs from vaginal prolapse, which is more likely to occur during partus or straining and involves a 360 degree protrusion of vaginal mucosa from the vaginal opening.³

Vaginal hyperplasia is more common in large breed dogs under 2 years old. It has a familial origin and clients should be advised not to breed with these dogs. Treatment of choice includes reducing swelling of the mass using castor sugar soaked abdominal swabs and preventing self-mutilation and desiccation. Transvulvar sutures can be used temporarily to help manually reduce the mass. Definitive treatment is to perform an ovariohysterectomy in the bitch.^1,3

Episiotomy

In many instances the vulvar opening severely hinders examination of the vaginal region and the urethral opening during surgery. One means of gaining better visualisation is to perform an episiotomy. This is a full thickness incision through the caudal vaginal wall. Large haemostats or Doyen atraumatic forceps are placed vertically up the vaginal vestibule and then the incision is made between these two instruments.

Episiotomy serves the surgeon many possibilities like the removal of vaginal tumours under direct visualisation, aiding in dystocia and visualisation of the urethral papilla in cases of urinary outflow obstruction. Repair of the episiotomy incision is done in a 3 layers closure using a monofilament absorbable suture material and a simple interrupted suture pattern.^1,3

Vaginal Tumours

Vaginal masses are not an uncommon finding in female dogs, fortunately 73–84% are benign³ and often they are pedunculated and intraluminal, which makes resection easier than initially anticipated. The most commonly encountered vulvar-vaginal tumours are fibroleiomyomas, lipomas, leiomyosarcomas, squamous cell carcinomas and transmissible venereal tumours (TVT).¹ Fibroleiomyomas tend to be smooth, firm and white, often pedunculated and easy to remove. TVTs on the other hand are diffuse, friable and bleed easily.

Excisional biopsy is the treatment of choice and episiotomy can make a surgeon's life much easier by providing direct visualisation. Where tumours are more extensive, removal of the entire mass via a vulvovaginectomy or even complete resection of the reproductive tract via a ventral celiotomy and pelvic ostectomy may be required.

Surgery of the Male Genitalia

Testicular Neoplasia

An interesting study revealed that 27% of intact, male dogs showed signs of testicular neoplasia at time of necropsy.⁴ Usually this involved older dogs with an average of greater than 10 years old. Most testicular neoplasms are likely benign and hence metastasis is rare. This does not include the cryptorchid testicles, which transform to malignant tumours at a very early stage.

Scrotal tumours, which are most commonly mast cell tumours and melanomas, must be differentiated from testicular neoplasia. Testicular neoplasms are usually Sertoli cell tumours (which produce oestrogen) and Leydig or interstitial cell tumours (which produce excessive testosterone). Others include seminomas and mixed germ cells stromal tumours. Multiple tumours of completely different cell types may be present within the same testicle. Testicular tumours in cats are extremely uncommon. Castration is the surgical treatment of choice in dogs and cats and is usually curative.

Phimosis/Paraphimosis/Hypospadias

Phimosis is the inability to extrude the penis from the prepuce. It is a rare developmental or post traumatic condition in which the preputial opening is too small or completely absent. It can also be secondary to preputial neoplasia or cellulitis. It results in secondary infection, self-mutilation and pooling of urine which causes cystitis.

Paraphimosis, in contrast, is the inability to retract the penis back into the prepuce. It may be associated with trauma, neurogenic abnormalities, copulation, penile haematomas, neoplasia or foreign bodies. Once retracted, a normal preputial sheath should cover the penis with an excess of at least 1 cm. Acute paraphimosis is usually managed conservatively. In cases where this is not sufficient, a preputiotomy, partial penile amputation or cranial advancement of the prepuce using imbrication of the cranial preputial muscles, is required.

Hypospadias is the last condition discussed in this group. It is a developmental abnormality in which the urethra opens ventral and caudal to the normal urethral orifice. It is also a rare condition and is often associated with other congenital abnormalities. Treatment of choice is a multilayer closure of the primary defect and castration of the individual.^5,6

Perineal Surgery

Anal Sacculectomy

The indications for unilateral or bilateral anal sacculectomy are chronic infection, impaction, sinus tract development or neoplasia. The technique is performed using either an open technique, in which the anal sphincter is severed to gain full access for dissection of the anal duct, or a closed technique in which blunt probes or cavity fillers are utilised and this allows the anal sacs to be removed without any damage to the anal sphincter.^7,8 The second technique is the preferred method as it is less invasive, but requires better instrumentation and a certain degree of surgical skill. Faecal incontinence is a possible complication with any technique for removing the anal glands.⁸

Feline Perineal Urethrostomy

A common presentation (almost 10% of feline hospital admissions) is that of cats showing signs of feline lower urinary tract obstruction (FLUTOS). The cause of this may be due to the production of uroliths that end up blocking the very narrow penile urethra or more commonly by a condition called feline idiopathic cystitis (FIC). This condition is often initiated by stress or changes in environmental conditions. Obesity is a strong predisposing factor and female cats are affected by this condition with the same frequency as male cats.

In most cases these patients can be successfully managed medically using careful catherisation of the penile urethra and flushing the urethra with saline or the administration of anxiolytics and sedatives. In cases where recurrent blockage occurs, a definitive treatment would be performing a perineal urethrostomy.⁶

References

1.  Macphail CM. Surgery of the reproductive and genital systems. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013.

2.  Chang SC, Chang CC, Chang TJ, et al. Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumours: 79 cases (1998–2002). J Am Vet Med Assoc. 2005;227:1625.

3.  Adin CA. Vagina, vestibule and vulva. In: Tobias KM, ed. Veterinary Surgery Small Animal. St. Louis, MO: Elsevier Saunders; 2012.

4.  Grieco V, Riccardi E, Greppi GF, et al. Canine testicular tumours: a study on 232 dogs. J Comp Pathol. 2008;138:86.

5.  Pavletic MM. Reconstruction of a canine urethra by use of an inverse tubed bipedicle flap in a dog with hypospadias. J Am Vet Med Assoc. 2007;231:71.

6.  Bleedorn JA, Bjorling DE. Urethra. In: Tobias KM, ed. Veterinary Surgery Small Animal. St. Louis, MO: Elsevier Saunders; 2012.

7.  Radlinsky MG. Surgery of the perineum, rectum and anus. In: Fossum TW, ed. Small Animal Surgery. St. Louis, MO: Elsevier Mosby; 2013.

8.  Aronson LA. Rectum, anus and perineum. In: Tobias KM, ed. Veterinary Surgery Small Animal. St. Louis, MO: Elsevier Saunders; 2012.