Umbilical Hernia

An umbilical hernia is a congenital or acquired defect in the abdominal wall at the umbilicus, through which abdominal contents (omentum, fat, or viscera) protrude. In veterinary surgery, it is classified as a true hernia when it consists of a hernial ring (the defect in the body wall), a hernial sac (peritoneum and skin), and hernial contents. Congenital umbilical hernias result from incomplete closure of the umbilical ring after birth, while acquired hernias may occur secondary to trauma or increased intra-abdominal pressure. The defect is typically small (1-2 cm) but can be large, allowing herniation of intestines, which may become incarcerated or strangulated. Surgical repair is indicated to prevent complications and is one of the most common procedures in small animal practice.

The primary etiology of umbilical hernias is congenital, resulting from failure of the umbilical ring to close completely after parturition. This incomplete closure is often due to a genetic predisposition, with certain breeds showing higher incidence. Acquired umbilical hernias are less common and may result from trauma (e.g., blunt force injury) or increased intra-abdominal pressure (e.g., pregnancy, obesity, or excessive straining). In some cases, iatrogenic causes such as improper ligation of the umbilical cord during delivery may contribute. The underlying cellular mechanism involves defective collagen synthesis or abnormal development of the abdominal wall musculature and fascia, leading to a weak point at the umbilicus.

Umbilical hernias are common in both dogs and cats, with a reported incidence of up to 2-4% in dogs. Certain breeds are predisposed, including Airedale Terriers, Pekingese, Basenjis, and Weimaraners, suggesting a hereditary component. In cats, the condition is less frequent but can occur in breeds like Persians. There is no significant sex predilection. Congenital hernias are typically present at birth or become apparent within the first few weeks of life. Acquired hernias can occur at any age, often secondary to trauma or increased intra-abdominal pressure. Small hernias may close spontaneously by 6 months of age, but larger defects usually persist and require surgical correction.

The pathophysiology of umbilical hernia involves a defect in the abdominal wall at the umbilicus, allowing abdominal contents to protrude. The hernial sac is lined by peritoneum and covered by skin. Initially, the hernia may be reducible, with contents easily returned to the abdominal cavity. However, as the hernia enlarges or if adhesions form, the contents may become incarcerated (non-reducible) or strangulated (compromised blood supply). Strangulation leads to ischemia, necrosis, and potential perforation of the herniated viscera, resulting in peritonitis and systemic inflammatory response syndrome (SIRS). The biomechanical forces of increased intra-abdominal pressure, such as during pregnancy or obesity, can exacerbate the herniation. In congenital cases, the defect is due to incomplete fusion of the abdominal wall components during embryonic development.

Intrinsic predisposing factors include genetic predisposition, as seen in certain breeds, and congenital weakness of the abdominal wall. Age is a factor, as small hernias may close spontaneously in young animals, while larger defects persist. Obesity and pregnancy increase intra-abdominal pressure, predisposing to hernia formation or enlargement. Extrinsic factors include trauma, such as vehicular accidents or bites, which can cause acute rupture of the abdominal wall. Poor nutrition and management practices may also contribute to poor tissue healing. Prior abdominal surgery with inadequate closure can lead to incisional hernias, though these are distinct from umbilical hernias.

Clinical signs of umbilical hernia vary depending on the size and contents. Small, reducible hernias often present as a soft, painless swelling at the umbilicus, with no systemic signs. Larger hernias may contain omentum or intestines, and if reducible, the contents can be manually replaced. If the hernia becomes incarcerated, the swelling becomes firm, painful, and non-reducible. Strangulation leads to acute signs of abdominal pain, vomiting, anorexia, depression, and possibly fever. On palpation, the hernial ring can be felt as a distinct defect in the abdominal wall. In severe cases, signs of shock and peritonitis may be present. It is important to assess for concurrent congenital anomalies, such as portosystemic shunts or cardiac defects, which may be associated with umbilical hernias.

Differential diagnoses for umbilical hernia include: 1) Umbilical abscess or infection, which presents with swelling, pain, and purulent discharge; 2) Hematoma, often due to trauma, with a history of injury and fluctuant swelling; 3) Neoplasia, such as lipoma or mast cell tumor, which may be firm and adherent; 4) Omphalitis, inflammation of the umbilical stump, common in neonates; 5) Abdominal wall hernia at other locations, such as inguinal or incisional hernias, which can be differentiated by palpation of the ring location; 6) Cystic remnant of the urachus, which may present as a midline swelling; 7) Granuloma, often secondary to foreign body or suture reaction. Definitive diagnosis is made by palpation of the hernial ring and imaging (ultrasound or radiography) to identify contents.

The diagnostic algorithm for umbilical hernia begins with a thorough physical examination, including palpation of the umbilicus to identify a soft swelling and a palpable ring. If the hernia is reducible, the contents can be pushed back into the abdomen, and the ring size can be assessed. If the hernia is non-reducible or painful, further imaging is warranted. Abdominal radiographs may reveal herniated viscera, especially if the hernia contains intestines, and can help assess for obstruction. Abdominal ultrasound is more sensitive for identifying hernial contents, assessing reducibility, and evaluating for complications such as strangulation. In cases of suspected strangulation, Doppler ultrasound can assess blood flow. Advanced imaging like CT may be used for complex cases, especially if concurrent anomalies are suspected. Preoperative laboratory workup (CBC, biochemistry, urinalysis) is recommended to rule out concurrent disease, especially in older animals.

In uncomplicated umbilical hernias, laboratory findings are typically within normal limits. If strangulation or peritonitis occurs, hemoconcentration, leukocytosis with a left shift, and elevated liver enzymes may be seen. Serum biochemistry may reveal electrolyte imbalances (e.g., hypokalemia) due to vomiting. Coagulation panel (PT/aPTT) is recommended if surgery is planned, especially in cases with liver disease. Inflammatory biomarkers such as C-reactive protein (CRP) and serum amyloid A (SAA) may be elevated in inflammatory or infectious conditions. Synovial fluid analysis is not relevant unless there is concurrent joint disease. Urinalysis may show signs of dehydration or urinary tract infection. Blood gas analysis may indicate metabolic acidosis in cases of shock.

Radiography: Standard abdominal radiographs (lateral and ventrodorsal views) may show a soft tissue opacity at the umbilicus, and if intestines are herniated, gas-filled loops may be visible. However, radiographs are often inconclusive for small hernias. Ultrasonography: This is the imaging modality of choice. It can clearly identify the hernial ring, the contents (omentum, fat, or bowel), and assess reducibility. Color Doppler can evaluate blood flow to herniated bowel, helping to diagnose strangulation. CT: Computed tomography provides detailed cross-sectional images and is useful for complex hernias, especially when concurrent abdominal anomalies are suspected. It can accurately measure the defect size and plan surgical approach. MRI: Rarely needed but may be used to evaluate soft tissue structures in detail. Fluoroscopy: Can be used to assess dynamic herniation during real-time imaging, but is not commonly required.

Cytology: Fine-needle aspiration of the hernial sac may be performed if there is suspicion of infection or neoplasia. Aspirated fluid or tissue can be examined for inflammatory cells, bacteria, or neoplastic cells. Histopathology: If the hernia is surgically removed, the hernial sac and contents may be submitted for histopathological examination. In congenital hernias, the sac typically shows fibrous connective tissue and peritoneum. If strangulation has occurred, necrotic bowel may show ischemic changes, hemorrhage, and inflammation. In cases of neoplasia, histopathology is essential for diagnosis and grading. Special stains may be used to identify specific tumor types.

Treatment of umbilical hernia is primarily surgical. Small, reducible hernias in young animals may be monitored for spontaneous closure up to 6 months of age. However, surgical repair is recommended for hernias that persist beyond this age, are large, or have a high risk of incarceration. Surgery is also indicated for any hernia that becomes non-reducible or strangulated. Preoperative stabilization is crucial in cases of strangulation, including fluid therapy, pain management, and correction of electrolyte imbalances. Surgical technique: The animal is placed in dorsal recumbency. A fusiform incision is made over the hernial sac. The sac is dissected free from the surrounding subcutaneous tissue. The hernial contents are reduced into the abdominal cavity. If the contents are adhered or strangulated, they are carefully dissected and assessed for viability. Non-viable bowel is resected and anastomosed. The hernial ring is then closed. For small defects, simple interrupted sutures with absorbable monofilament (e.g., polydioxanone, size 2-0 to 0) are placed in the external rectus sheath. For larger defects, a herniorrhaphy may be performed using a simple continuous pattern or a tension-relieving technique such as a Mayo mattress pattern. In cases of excessive tension, a mesh (e.g., polypropylene) may be used to bridge the defect. The subcutaneous tissue and skin are closed routinely. Postoperative care includes pain management (opioids, NSAIDs), antibiotics if indicated, and activity restriction for 2-4 weeks.

The prognosis for umbilical hernia repair is excellent, with a low complication rate. For uncomplicated hernias, the success rate is near 100%. Complications are rare but may include seroma formation, infection, dehiscence, or recurrence. Recurrence is more likely if the defect is large or if tension was present during closure. In cases of strangulation, the prognosis depends on the extent of bowel necrosis and the timeliness of surgical intervention. If resection and anastomosis are performed without complications, the prognosis is good. Negative prognostic indicators include delayed presentation, severe peritonitis, and concurrent systemic disease.

Postoperative follow-up includes monitoring for signs of infection, seroma, or recurrence. Sutures are typically removed 10-14 days after surgery. Activity restriction is recommended for 2-4 weeks to allow proper healing. A recheck examination is advised at 2 weeks and 4 weeks postoperatively to assess healing. If mesh was used, longer follow-up may be needed. Owners should be instructed to monitor for any swelling or discomfort at the surgical site. In cases of strangulation, serial monitoring of vital signs and laboratory parameters is essential. Long-term follow-up is generally not required for uncomplicated cases, but any recurrence should be promptly evaluated.

Pearls: 1) Always palpate the hernial ring to assess size and reducibility. 2) In young animals, small hernias may close spontaneously, but surgical repair is safe and prevents future complications. 3) Use a simple interrupted pattern with absorbable monofilament for closure to minimize tissue reaction. 4) If the hernia is large, consider using a mesh to reduce tension. 5) Always check for concurrent congenital anomalies, especially portosystemic shunts. Pitfalls: 1) Failure to identify strangulated bowel, leading to necrosis and peritonitis. 2) Inadequate closure of the hernial ring, leading to recurrence. 3) Excessive tension on the closure, causing dehiscence. 4) Damage to the bladder or other viscera during dissection. 5) Not addressing concurrent infections or systemic disease, which can compromise healing.

Perioperative antimicrobial prophylaxis: Cefazolin (22 mg/kg IV) administered 30 minutes before incision and repeated every 90 minutes during surgery. Postoperative antibiotics are not routinely indicated unless there is contamination or infection. Analgesia: Preoperative opioids such as hydromorphone (0.05-0.1 mg/kg IV) or methadone (0.1-0.3 mg/kg IV). Intraoperative analgesia can be provided with a constant rate infusion (CRI) of fentanyl (5-10 mcg/kg/hr IV) or lidocaine (25-50 mcg/kg/min IV). Postoperative NSAIDs such as carprofen (2.2 mg/kg PO q12h) or meloxicam (0.1 mg/kg PO q24h) for 3-5 days. If NSAIDs are contraindicated, use tramadol (2-5 mg/kg PO q8-12h) or gabapentin (5-10 mg/kg PO q8-12h). Local anesthesia: A line block with bupivacaine (1-2 mg/kg) at the incision site can provide additional analgesia. For animals with liver disease, adjust dosages and avoid NSAIDs. In cases of strangulation, aggressive fluid therapy with balanced crystalloids (e.g., lactated Ringer's solution) at shock rates (90 ml/kg/hr for dogs, 45 ml/kg/hr for cats) is essential.

Landmark studies and consensus guidelines support the surgical management of umbilical hernias. A retrospective study by Tobias (2010) reported that surgical repair of umbilical hernias in dogs and cats has a low complication rate and excellent outcomes. The ACVS (American College of Veterinary Surgeons) guidelines recommend surgical repair for hernias that do not spontaneously close by 6 months of age or if they are large. A study by Smeak (2000) evaluated the use of mesh for large abdominal wall defects, showing good results. In terms of anesthesia, a study by Muir (2007) highlighted the importance of perioperative analgesia in reducing stress and improving recovery. The use of prophylactic antibiotics is supported by the ACVS guidelines, which recommend cefazolin for clean-contaminated procedures. Overall, the evidence supports early surgical intervention to prevent complications such as strangulation.