Catriona M. MacPhail Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA Perineal herniation occurs when there is breakdown of the pelvic diaphragm and transit of intra‐abdominal contents into the ischiorectal fossa of the perineum. The pelvic diaphragm consists of the levator ani muscle, coccygeus muscle, and pelvic fascia. Caudal herniation between the external anal sphincter and levator ani and coccygeus muscles is the most common of the four types. Dorsolateral herniation (between coccygeus and levator ani muscles) and lateral herniation (between coccygeus muscle and sacrotuberous ligament) can also occur. Ventral herniation with rectal sacculation occurs between the ischiocavernosus and ischiourethralis muscles and bulbocavernous muscle, and it is the most challenging type to resolve. The most common, almost exclusive, signalment for perineal herniation is middle‐aged to older, male, sexually intact canines. Inciting causes include tenesmus due to prostatic, lower urinary, or colorectal disease, hormonal alternations, and anatomic muscular weakness; however, a clear etiology often remains undetermined. A recent study found no association between perineal hernias and concurrent gastrointestinal, neurologic, or orthopedic conditions.1 However, a separate study in adult female dogs found comorbidities to be common, including a history of trauma or chronic cough due to cardiopulmonary disease.2 For male dogs, prostatic disease appears to be the most likely contributing factor, as a recent study investigating CT imaging of the prostate in age‐matched intact males dogs with and without perineal hernias found dogs with hernias to have larger prostates, more and larger prostatic and paraprostatic cysts, and more frequent prostatic mineralization.3 Clinical signs vary in significance and are dependent on what tissues and organs are herniated. Deviation or dilation of the rectum into the perineal region results in tenesmus and constipation. Prostatic or urinary bladder herniation results in stranguria or anuria if these organs become retroflexed and entrapped. Herniation of the small intestine is a severe but uncommon clinical scenario (Figure 34.1). Perineal hernias can be unilateral or bilateral, but with identification of an overt unilateral hernia, it is common to identify pelvic diaphragm weakness on the opposite side. One study of 31 dogs with unilateral presentation of perineal hernia found contralateral pelvic diaphragm weakness in all cases.4 Figure 34.1 Lateral abdominal radiograph of male intact dog demonstrating severe perineal herniation of the small intestines and presumed urinary bladder due to bladder’s absence in the caudal abdomen. Diagnosis of a perineal hernia is confirmed by rectal palpation. Determination of the origin of hernia contents can be accomplished through abdominal radiographs and abdominal ultrasound. If there is suspicion for bladder entrapment, point‐of‐care ultrasound should be used immediately to determine the location of the urinary bladder. Aspiration of a fluid‐filled hernia should be performed with caution; preferentially, an attempt at passage of a urethral catheter can be performed to relieve urinary obstruction. Multiple surgical procedures exist to address perineal hernias. Regardless of repair technique, castration should be performed in all male intact dogs to decrease prostatic size and limit hormonal influence, in order to reduce the risk of straining and recurrence. Prior to repair, a purse‐string suture is placed in the anus, and the skin and subcutaneous tissues of the perineum are carefully incised in a curvilinear dorsal to ventral direction from the base of the tail to ~1 cm ventral to the palpable ischiatic table. A tip is to stay 1–2 cm lateral to the anus in order to reduce the risk of anal sac injury. A hernia sac is commonly identified, which is a reflection of the caudal peritoneum. This tissue is breached to allow replacement of contents into the abdominal cavity. A 4 × 4‐in. gauze square on sponge forceps can be useful to keep reduced organs in place while performing hernia repair. Important anatomical structures to avoid in this region when reducing hernia contents include the caudal rectal nerve (branch of the pudendal nerve) and caudal rectal artery (branch of the internal pudendal artery), which course together from lateral to medial near the center and dorsal aspect of the internal obturator muscle (Figure 34.2). Traditional herniorrhaphy involves the preplacement of nonabsorbable monofilament sutures (e.g., 2‐0 polybutester) between the external anal sphincter and levator ani and/or coccygeus muscles. This procedure is considered outmoded due to tension across the muscular closure leading to repair failure and due to the realization that ventral support is required to minimize the chance of recurrence. Figure 34.2 Approach to left perineal region. The left caudal rectal nerve and adjacent caudal rectal branch of the internal pudendal artery (yellow *) are avoided during the herniorrhaphy.
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Perineal Hernia
Introduction
Indications/Pre‐op Considerations
Surgical Procedures
Internal Obturator Transposition
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