Equine field surgery- Urogenital surgery (Proceedings)
If the side of cryptorchidism is unknown, surgery can be prolonged and laparoscopic exploration of the abdomen may be a better approach.
Urogenital Surgeries
Male
• Cryptorchid castration
• Circumcision
• Penile amputation
• Urethrotomy
Cryptorchidism
• Left testicles - more likely abdominal
• Right testicles - more likely inguinal
• Previous surgical exploration
– makes identification of surgical landmarks difficult
• If the side of cryptorchidism is unknown, surgery can be prolonged and laparoscopic exploration of the abdomen may be a better approach
Geldings with Stallion-like Behavior
• Serum testosterone at time zero and 30 to 120 minutes after ? 6000 IU human chorionic gonadotropin (HCG) IV
– Geldings have serum testosterone levels of less than 40 pg/ml
– Cryptorchids have serum concentrations of greater than 100 pg/mL
• Baseline testosterone levels – < 40 pg/ml = gelding
– > 100 pg/ml = testicular tissue
• Post hCG stimulation – 6,000 or 12,000 IU given intravenously
– 1 hour & 2 hour - 200 % INCREASE
– 24 hours & 48 hours - 400 % INCREASE
• Estrogen Assays – Conjugated or unconjugated
• most common tested is estrogen sulfate
– Increased levels
– > 3 years of age - 95-96% accurate
– False negatives - < 3 years or donkeys
• If <18 months of age or during winter
may respond poorly to HCG
Collect additional sample 24 hours after HCG
retest when older or during the spring
Rectal palpation
• may help determine location
– Horses with abdominal testicles will have a small or indiscernible inguinal ring
– A larger ring with evidence of the ductus deferens entering the canal indicates the horse is an incomplete abdominal cryptorchid, is an inguinal cryptorchid, or has a descended scrotal testicle
• Perform based on temperament and size of the horse, and the anticipated surgical approach
• Bilateral cryptorchidism occurs in up to 15% of cryptorchid horses
Cryptorchid Castration
Equipment • Emasculators - White's modified, Serra, and Reimer
• Sponge forceps - to evert the vaginal process
Anatomy • Picture of normal testicle
• Epididymis – Head, body & tail
• Gubernaculum
– proper ligament
– Ligament of the tail of the epididymis
– Scrotal ligament
Cryptorchid Castration - Inguinal Approach
• Cryptorchid testicle removed first
• Incision over superficial inguinal ring
• Incision is extended by blunt dissection
• Superficial caudal epigastric vessels
– lateral to the incision
• Identify the inguinal extension of the gubernaculum or the vaginal process
• Inguinal testicle identified at this point
• Open vaginal tunic to confirm the presence of a testicle
• Incomplete abdominal cryptorchids will have only the epididymis present in the vaginal tunic
• Don't mistake descended tail of the epididymis for a small testicle
Cryptorchid Castration - Noninvasive Inguinal Approach
• If abdominal, the cranial medial aspect of the superficial inguinal ring is searched for the inguinal extension of the gubernaculum (scrotal ligament)
• Palpable as a fibrous band which descends into the inguinal canal
• Size generally less than 1 cm
• Light traction and blunt dissection to loosen tissue around the structures in the inguinal canal result in exposure of the vaginal process
• Vaginal process incised, and the epididymis or ligament of the tail of the epididymis is used to retrieve the testicle from the abdomen.
• If the inguinal extension of the gubernaculum is not located, the vaginal process can often be found by palpating a thin cordlike structure in the depression of the deep inguinal ring and by placing a curved sponge forceps in the deep inguinal ring and carefully everting the vaginal process
• Opening the vaginal process reveals the ligament of the tail of the epididymis
• Enlarge the vaginal ring manually with a finger, or with Metzenbaum scissors
• Some testicles will not be able to be exteriorized sufficiently to effectively apply emasculators and will require ligation
• Close superficial inguinal ring if the vaginal ring has been opened or is wider than one finger width
• Further closure of the subcutaneous tissues and skin is optional
Cryptorchid Castration - Parainguinal Approach
• Use if known abdominal testicle
• Or, when noninvasive approach unsuccessful
• Incision parallel and medial to the superficial inguinal ring beginning 3 to 4 cm cranial to the cranial extent of the ring
• A 4-cm incision is made into the aponeurosis of the external abdominal oblique muscle.
• The index and middle finger are inserted through this incision and bluntly through the internal abdominal oblique, transverse fascia, and peritoneum and into the peritoneal cavity
• The area of the deep inguinal ring is swept with the finger for testicle or related structures
• Traction used to exteriorize the testicle from the abdomen
• The aponeurosis of the external abdominal oblique muscle is closed with No. 2 or 3 synthetic absorbable suture material
• Skin and subcutaneous tissue are closed with 2-0 absorbable synthetic suture material.
Expected Outcome
• Variable difficulty and time required
• Often difficulty cannot be predicted preoperatively
• Inguinal cryptorchids require little more than routine castrations
• Some abdominal cryptorchids require significant time, careful exploration, and closure
• Best results come when the surgeon is prepared for either situation
Complications
• Similar to routine castration
• Risk of incisional problems and eventration greater
• Adhesion formation near the inguinal ring may cause colic
• Noninvasive approaches when possible and entering the abdomen through approaches that can be closed directly (e.g., the modified parainguinal incision) decrease the risk of incisional complications and eventration
• Rarely, greatly enlarged testicles, teratomas, or cystic testicles are identified and require removal through an enlarged incision.
• Monorchidism is rare but possible. If a retained testicle is not identified after a thorough search, two options are available. The horse can be referred for further surgery, preferably laparoscopy, or the descended testicle can be removed and hormonal testing carried out to confirm the absence of testicular tissue.
Circumcision
Indications • removal of neoplastic tissue, granulomas, or other masses from the sheath
• removal of preputial scar tissue that prevents penile retraction or extension
• Equipment - tourniquet optional
Expected outcome
• Most common reason for circumcision is removal of squamous cell carcinoma
• The prognosis is good if:
– extent of neoplasia is limited
– Neoplasia confined to the preputial tissues
– wide surgical margins are taken
Complications - Edema common, recurrence possible, dehiscence +/- stricture, further resection
Alternatives • Laser excision of neoplastic tissues
– Improved hemostasis
– Ablates underlying tumor bed
• Local excision combined with cisplatin injection and topical 5-fluorouracil
Penile Amputation
Indications
• Neoplastic lesions (primarily squamous cell carcinoma) and other masses involving the shaft of the penis
• Permanent penile paralysis
• Paraphimosis
• Priapism
• Equipment
– Tourniquet
– urinary catheter
Penile amputation Procedures
• William's Technique
• Scott's Technique
• Vinsot's technique
– triangular portion of epithelium and underlying tissue with the base proximal to the apex is removed
– Modification performed in standing horses
• vertical incision directly to the urethra
• nonabsorbable circumferential ligature is placed around the penis, and the penis is transected distal to the ligature
• urethral mucosa is sutured to the skin as previously described. The penile stump is allowed to heal by second intention
• Advantages are decreased surgery time, and the potential to perform the procedure standing
• Disadvantages are the tendency for stricture formation, and excessive bleeding
Expected Outcome • Recurrence or metastasis of SCC common
• Survival – 60%-71% > 1 year
• If urethra involved
– 30% 18 month survival
Complications – Hemorrhage, dehiscence, urethral stricture, minor swelling, recurrence or metastasis of neoplastic lesions
Comments
• Distal amputation less complicated than proximal
– penis diameter increases proximally
– redundant tissue of the prepuce increases surgical and anesthetic time
• For SCC
– assess the horse for evidence of metastasis
– identify small lesions elsewhere on the penis or prepuce
– If lesions too proximal to amputate or requiring preputial ablation and inguinal lymph node removal, more involved procedures have been described
Urethrotomy
Indications
• Urolithiasis involving the bladder and urethra
• Urethral rents causing hemospermia in stallions and hematuria in geldings
• Temporary urine diversion for urethral obstructive lesions, such as hematoma, neoplasia (e.g., squamous cell carcinoma), or parasitic granuloma (e.g., habronemiasis)
Equipment • male urinary catheter
• Possible custom-made lithotrite
Anatomy
• The male pelvic urethra is about 12 cm long and tapers in diameter from 3 cm near the prostate to 1.5 cm in the extrapelvic region
• Urethralis muscle envelops the pelvic urethra
• Corpus spongiosum penis surrounds the urethra
• Bulbospongiosus muscle lies caudal to the pelvic urethra and becomes ventral to the extrapelvic urethra distally
• Bilobed retractor penis muscle lies beneath the subcutaneous tissue at the perineal region
Procedure
• Vertical incision starts 4 to 6 cm distal to the anus and extends ventrally for 8 to 10 cm through the median raphae skin and subcutaneous tissue
• The incision should not extend ventral to the ischium
• Retractor penis muscles are separated on midline and reflected laterally
• Bulbospongiosus muscle is exposed and incised
• Hemorrhage is expected
• The incision continues through the corpus spongiosum penis and the urethral wall
• Urethral lumen entry is verified by visualizing and palpating the urinary catheter
• The catheter helps to prevent both accidental deviation from midline and penetration of the cranial urethral wall
Expected outcome for Cystic urolithiasis
• Good prognosis
• Possibility of recurrence
• If not treated early
– urethral obstruction
– bladder rupture
• Urethrotomy success for other urinary obstructive lesions depends primarily on the nature and extent of the lesion
Complications
• Excessive bleeding
• Urine scald
• Unilateral urine scald
• Stricture formation
• Recurrence of urolithiasis
• Rectal or urethral damage
• Orchitis
• Peritonitis
• Bladder rupture
Alternatives
• Urethral rents - perineal release incision
• Urethrostomy for permanent urine diversion
• Laparocystotomy
– advantages are the decreased recurrence rate
– less trauma
• Laparoscopy
Comments
• Most cystic calculi are large enough that they must be crushed or broken into smaller pieces to allow removal through an urethrotomy incision
• Other, less traumatic, options for eliminating uroliths via urethrotomy include laser (e.g., pulsed-dye) and electrohydraulic lithotripsy
• Perform urethrotomy 24 to 48 hours before lithotripsy for less hemorrhage
Inguinal Hernia
• Primarily congenital in males
• Most resolve by 3-6 months of age
• Cause is unknown, but a hereditary predisposition may exist
• Development of the hernia
– increased abdominal pressure at birth
– large vaginal rings
– straining to pass meconium
• Foals generally present with nonpainful swelling or enlargement of the scrotum or inguinal region
• Usually reducible and do not cause any clinical signs
• Resolve within a few days to a few months
• Predisposition to evisceration following castration?
Indications
• Repair indicated for inguinal herniorrhaphy when:
– not resolved by 3 to 6 months of age
– gradually increasing in size
– owners request elective repair
• Foals with large hernias that have ruptured into the subcutaneous space or exhibit clinical signs of abdominal pain should not be repaired in the field because of the difficulty in reducing these hernias and the potential need for abdominal exploration
Anatomy
• Peritoneum
• Internal abdominal oblique
• External abdominal
• Scrotum
• Vaginal tunic
• Tail of the Epididymus
• Testicle
• Vaginal ring
Direct vs. Indirect
Congenital vs. Acquired
Expected Outcome
• Edema of the incision site and prepuce
– generally resolves with conservative therapy
• In uncomplicated and elective cases, recovery is usually straightforward and uneventful
Complications
• Prevalence of complications is low
• Seroma formation most common
• Failure to resect devitalized
• In neonates, exploratory celiotomy has the added advantage of being able to remove the umbilical remnants to reduce the incidence of septicemia
• Preoperative concerns to warrant referral
– systemic health of the foal
– viability of the intestine
– anticipated length or difficulty of the procedure
• Uncommon complications
– incisional infections
– wound dehiscence with evisceration
– intestinal prolapse
– paralytic ileus
– Bronchopneumonia
– abdominal adhesions
– Peritonitis
– Colic
– incidence of complications ~13% (4 of 31)
– survival rate only 50%
Alternatives
• Laparoscopic techniques have been developed to repair readily reducible inguinal hernias and possibly salvage the affected testicle
References
Adams SB, Fessler JF, editors: Atlas of Equine Surgery, Philadelphia, 2000, WB Saunders Co.
Auer JA, Stick JA, editors: Equine Surgery, 3rd ed. Philadelphia, 2006, WB Saunders Co.
McIlwraith CW, Robertson JT, Turner AS, editors: Equine Surgery: Advanced Techniques, 2nd ed. Ames, IA, 1998, Blackwell Publishing.
McIlwraith CW, Robertson JT, Turner AS, editors: Equine Surgery, 2nd ed. Philadelphia, 1998, Lippincott Williams & Wilkins.
Wilson DA, Kramer J, Constantinescu GM, Branson KR, editors. Manual of Equine Field Surgery, St Louis, 2006, Elsevier.
