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Compendium June 2008 (Vol 30, No 6)


by Stephen Birchard, DVM, MS, DACVS, Michael Nappier, DVM

    CETEST This course is approved for 2.0 CE credits

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    Cryptorchidism is a common clinical problem in dogs and cats. Retained testes can be unilateral or bilateral, are usually small and atrophied, and vary in location. These factors make diagnosis and surgical removal challenging in some animals. Diagnosis is confirmed using a variety of modalities, including diagnostic imaging in difficult cases. Surgical removal of the affected and normal testes is the treatment of choice. The surgical approach and technique used depend on the location of the retained testis.

    Cryptorchidism is one of the most common congenital defects seen in small animal practice. In dogs, the reported prevalence of cryptorchidism ranges from 0.8% to 10%.1 The defect is a sex-linked autosomal recessive trait that is common in certain breeds,2 such as Chihuahuas, miniature schnauzers, Pomeranians, poodles, Shetland sheepdogs, and Yorkshire terriers. Smaller breeds are 2.7 times more likely to be cryptorchid than larger breeds.3 In cats, one study found Persians to be predisposed to cryptorchidism.4 Due to the thermal suppression of sperm production, bilaterally cryptorchid animals are sterile, while unilaterally cryptorchid animals are usually fertile.5 Undescended testes are 13.6 times more likely to develop neoplasia (Figure 1) than normal testes and are at increased risk of torsion.6,7

    Undescended testes vary in their anatomic position. They may be located in the prescrotal area, inguinal region, or abdominal cavity. In a study of 240 cryptorchid dogs and 50 cryptorchid cats, retained testes were most commonly found in the right inguinal region in dogs and in the left or right inguinal region in cats.8 Locating an ectopic testis can be difficult in some animals. A thorough and systematic approach to patient evaluation is necessary to efficiently find and remove the abnormal testis. Although surgery for removal of cryptorchid testes is well described in the veterinary literature, approaches to diagnosis and localization of ectopic testes have not been extensively described. This lack, coupled with the increasing number of animals that present with an unknown neutering history (e.g., rescue animals), emphasizes the need for a discussion of a thorough clinical approach to cryptorchidism.

    This article describes a systematic approach to the diagnosis and surgical treatment of cryptorchidism in dogs and cats, including the integration of the history; physical examination; blood tests, including hormone assays; and diagnostic imaging to make a definitive anatomic diagnosis. Various options for surgical removal of the retained testis are also described.



    Most authors agree that if one or both testes are not present in the scrotum by 2 months of age, the animal is cryptorchid.2 It is highly unlikely that the testes will descend into the scrotum after this age. The clinical signs of cryptorchidism are usually not recognized by the owner. Young affected animals generally do not show signs of illness unless the retained testis develops an associated pathology such as torsion or neoplasia. Routine physical examination reveals a lack of one or both testes in the scrotum. Older dogs may develop a neoplasm (e.g., Sertoli cell tumor [ Figure 1 ]) in the retained testis. Dogs with a Sertoli cell tumor may present with feminization syndrome characterized by symmetric alopecia and gynecomastia (Figure 2). Other testicular neoplasms, such as seminoma, rarely cause signs other than a palpable mass in either the inguinal canal or abdomen. Animals with testicular torsion usually present with acute abdominal pain and lethargy (Figure 3).

    Physical Examination

    Because ectopic testes can be located in several different areas of the body, the physical examination must be thorough. Areas to focus on include the scrotum, prescrotal area, inguinal canals, and abdominal cavity. If one testis is present in the scrotum, pushing it dorsally and cranially into the inguinal canal can help determine whether it is the right or left testis. After determining which testis is retained, carefully palpate the prescrotal area and inguinal canal on the affected side. Palpation of the testis in the inguinal region may be difficult because it can be confused with inguinal fat or the inguinal lymph node. Ultrasonography may be helpful to identify the testis (see Diagnostic Imaging, below). Perform abdominal palpation, but unless the retained testis is affected with a tumor, it is likely to be atrophied and very difficult to palpate. Failure to palpate an abdominal testis does not rule it out.

    In addition to examining the animal to locate the retained testis, perform a general physical examination to rule out diseases associated with cryptorchidism. Examine the patient for alopecia and enlarged mammary glands caused by a Sertoli cell tumor, abdominal discomfort due to testicular torsion, and an inguinal or abdominal mass associated with testicular neoplasm (Figure 2).

    Laboratory Evaluation

    If indicated (e.g., in patients with advanced age or signs of other diseases), conduct a preoperative complete blood count and serum chemistry profile. The hyperes­trogenism associated with Sertoli cell tumors can cause bone marrow suppression and aplastic anemia. In older animals, evaluate the chemistry profile for evidence of unrelated chronic disease such as renal failure or liver disease. If these conditions are present, provide treatment to attempt to stabilize the animal before general anesthesia and surgery to remove the retained testis.

    A testosterone assay can be conducted to determine whether the animal has functional testicular tissue. The testosterone level will be consistent with that of an uncastrated animal if testicular tissue is present. Serum testosterone assays can be conducted before and 2 hours after administration of human chorionic gonadotropin to verify the results of the testosterone assay. See  Box 1  for the steps of this test.

    Diagnostic Imaging

    Plain film radiography of the abdomen may be useful if testicular neoplasia or torsion is suspected. Retained testes appear as intraabdominal soft tissue masses. Thoracic radiography should also be conducted in animals with suspected neoplasia to rule out metastasis.

    Ultrasonography of the abdomen, inguinal canals, and prescrotal area can be helpful in definitively identifying testicular tissue (Figure 4). The testis has a characteristic ultrasonographic appearance, with the mediastinum testis appearing as an echogenic linear structure in the center of the echogenically homogeneous testis.9 Ultrasonography of the retained and normal testes can also help rule out a neoplasm in the parenchyma.10

    Surgical Treatment

    Because of the pathology that commonly affects ectopic testes, and because the condition is hereditary, we recommend surgical removal of both testes in affected animals. For cosmetic reasons, or to prevent disqualification of the animal in the show ring, some clients may ask their veterinarian to surgically pull the retained testicle down into the scrotum. Do not attempt to surgically move an inguinal or prescrotal testis into the scrotum. Because of the hereditary nature of the disorder, this cosmetic procedure is unethical and will encourage perpetuation of the defect in future generations of animals.

    Prescrotal Testis

    Prepare the prescrotal area for aseptic surgery. In dogs, testes located just cranial to the scrotum can be removed either by pushing the testis caudally and exposing it through a standard prescrotal midline incision or by simply incising directly over the testis. The testis is easily exposed and removed via either approach. The testis can be removed in either an open (incise through the tunic) or a closed (leave the tunic intact) fashion. In cats, because scrotal testes are typically removed via bilateral scrotal incisions, testes in the prescrotal area will most likely require incision directly over the testis. As with removal of a normal testis, expose the testis, vas deferens, and vessels. Triple ligate the vas deferens and vessels with absorbable suture, incise between the distal two ligatures, and remove the structure. Close the subcutaneous tissue and skin routinely.

    Inguinal Testis

    Testes located in the inguinal area usually require incision directly over the inguinal canal. Meticulous and thorough dissection may be required to expose the testis. Be careful not to injure the pudendoepigastric artery and vein or their branches. It is possible to confuse the inguinal lymph node with the testis. However, careful dissection and gross examination of the structure should allow differentiation before proceeding with the excision. Once the testis and associated structures are exposed, remove them as described for prescrotal or normal testes.

    In rare cases, the testis may be found within the inguinal ring. Gentle traction on the gubernaculum may move the testis out of the ring and into the subcutaneous space. Careful dissection and incision into the external inguinal ring may be necessary to remove the testis. During this dissection and subsequent closure of the ring, be careful not to injure the external pudendal artery and vein. Once the testis and associated structures are exteriorized, remove them as described for prescrotal testes. If the inguinal ring fascia was incised to remove the testis, carefully close the tissue with simple interrupted absorbable sutures. Routinely close the subcutaneous tissue and skin. Meticulously close subcutaneous dead space to prevent seromas, which are common in this area.

    If the ectopic testis is not in the inguinal area, extend the skin and subcutaneous incisions cranially and perform an abdominal approach.

    Intraabdominal Testis

    In cats, unilateral or bilateral intraabdominal testes are removed by a ventral midline approach. In dogs, intraabdominal testes can be removed either by a standard ventral midline approach or by a paramedian approach (see Box 2). Bilateral intraabdominal testes should be approached via the ventral midline. For unilateral abdominal testes in dogs, we prefer the paramedian approach. The advantage of the paramedian approach is that it avoids dissection around the prepuce and ligation of the caudal superficial epigastric artery and vein. The paramedian approach also avoids creating dead space in the subcutaneous tissue adjacent to the prepuce. Seroma formation is very common in this area.

    Although the paramedian approach can allow removal of the testis through a smaller incision than the ventral midline approach, the surgeon should sufficiently expose the intraabdominal structures to allow careful, accurate identification. Expose and remove the testis only after verifying that all other structures have been correctly identified. In one clinical study, the prostate gland was inadvertently removed in three dogs because of insufficient exposure while attempting to remove an abdominal testis.11 If additional exposure is needed to identify key structures, enlarge the abdominal incision and use appropriate retractors to find the testis and surrounding organs.

    Rarely, the abdominal approach reveals that the testis is in the inguinal canal. It may still be possible to remove the testis through this approach by enlarging the inguinal canal to allow moving the testis into the abdomen. Alternatively, remove the testis as described in the inguinal approach.

    Recently, laparoscopy-assisted cryptorchidectomy has been described in dogs and cats.12 The complications associated with this technique were minimal, and operative times decreased with experience. The disadvantages of this technique are the expense of the equipment and the expertise needed to operate it. Anesthetic concerns are related to decreased venous return secondary to insufflation of the abdomen with carbon dioxide and hypoventilation due to the head-down position of the animal during the procedure. However, these anesthetic issues were not seen in the animals in this study.

    Postoperative Care and Complications

    We routinely submit all excised tissue for histopathology to ensure complete removal of testicular tissue and to examine for testicular neoplasia. Routine postoperative care after removal of retained testes involves monitoring of the incision for inflammation, seroma, or infection. Some animals may require an Elizabethan collar to prevent licking of the incision. Analgesic therapy is indicated. A local tissue block can be performed using bupivacaine on the body wall and skin before closure. We generally use intravenous opioid medications (e.g., hydromorphone) for the first 12 to 24 hours postoperatively, followed by an oral NSAID for 3 to 5 days.

    Rare complications include incisional dehiscence, inadvertent prostatectomy during removal of abdominal testes, ureteral ligation, and hemorrhage due to inadequate ligation of testicular blood vessels. We retrospectively evaluated 10 consecutive dogs that underwent the paramedian abdominal approach for removal of abdominal testes at The Ohio State University Veterinary Teaching Hospital. Only two dogs had complications; one had excessive incisional swelling and the other had an incisional infection. Both complications resolved with appropriate treatment, and no dogs had long-term problems.

    Downloadable PDF

    1. Cox VS, Wallace LJ, Jessen CR. An anatomic and genetic study of canine cryptorchidism. Teratology 1978;18:233-240.

    2. Graves TK. Diseases of the testes and scrotum. In: Birchard SJ, Sherding RG, eds. Saunders Manual of Small Animal Practice. 3rd ed. St. Louis: Elsevier; 2006:963.

    3. Pendergrass TW, Hayes HM Jr. Cryptorchidism and related defects in dogs: epidemiologic comparisons with man. Teratology 1975;12:51-55.

    4. Millis DL, Hauptman JG, Johnson CA. Cryptorchidism and monorchism in cats: 25 cases (1980-1989). JAVMA 1992;200:1128-1130.

    5. Romagnoli SE. Canine cryptorchidism. Vet Clin North Am Small Anim Pract 1991;21:533-544.

    6. Hayes HM, Pendergrass TW. Canine testicular tumors: epidemiologic features of 410 dogs. Int J Cancer 1976;18:482.

    7. Pearson H, Kelly DF. Testicular torsion in the dog: a review of 13 cases. Vet Rec 1975;97:200-204.

    8. Yates D, Hayes G, Heffernan M, Beynon R. Incidence of cryptorchidism in dogs and cats. Vet Rec 2003;152:504-506.

    9. Matoon JS, Nyland TG. Prostate and testes. In: Nyland TG, Matoon JS, eds. Small Animal Diagnostic Ultrasound. 2nd ed. Philadelphia: WB Saunders; 2002:259.

    10. Johnston GR, Feeney DA, Johnston SD, O'Brien TD. Ultrasonographic features of testicular neoplasia in dogs: 16 cases (1980-1988). JAVMA 1991;198:1779-1784.

    11. Schulz KS, Waldron DR, Smith MM, et al. Inadvertent prostatectomy as a complication of cryptorchidectomy in four dogs. JAAHA 1996;32:211-214.

    12. Miller NA, Van Lue SJ, Rawlings CA. Use of laparoscopic-assisted cryptorchidectomy in dogs and cats. JAVMA 2004;224:875-878.

    References »

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