Congenital hernia

• A congenital hernia is a defect in the abdominal wall or diaphragm that is present at birth. Abdominal organs or other abdominal tissue may displace through the defect.
• A true hernia has a hernia sac (peritoneum) surrounding the contents. A true hernia is usually the result of a congenital weakness in the abdominal wall.
• True hernias are often reducible (ie contents can move freely between hernia sac and abdomen), because the hernia sac reduces adhesion formation.
• A false hernia has no hernia sac and is usually acquired from trauma or previous surgery. False hernias are more likely to have adhesions that can cause incarceration (ie hernia contents are not able to be moved back into the abdominal cavity).
• The contents of the hernia are said to be strangulated when its blood supply is compromised.
• Congenital diaphragmatic hernias Diaphragm: hernia may be pleuroperitoneal, peritoneopericardial Peritoneal-pericardial diaphragmatic hernia (PPDH), or hiatal.
• Pleuroperitoneal hernia is a defect in the dorsolateral diaphragm with herniation of abdominal viscera into the thoracic cavity. The defect may involve absence of 1-2 cm in the left crus, or the defect may be in both crura and parts of the central tendon. Pleuroperitoneal hernia is rare.
• Peritoneopericardial hernia occurs with improper development of the transverse septum that allows herniation of abdominal viscera into the pericardial sac.
  This is the commonest congenital pericardial and diaphragmatic anomaly in cats.
• Hiatal hernia is protrusion of abdominal organs through the esophageal hiatus of the diaphragm into the thoracic cavity. Sliding hiatal hernia involves the abdominal section of esophagus, the esophagogastric junction, and part of the stomach moving through the esophageal hiatus. Herniated tissues may move in and out of the thorax with changes in pleuroperitoneal pressure gradient. With paraesophageal hernia, the esophagogastric junction remains in normal position, but the fundus and various portions of the stomach move through the esophageal hiatus alongside the esophagus. Pure paraesophageal hiatal hernia is rare, but may be combined with a sliding hernia. Sliding hernia alone is most common, the associated clinical signs may occur intermittently.
  Hiatal hernia is rare in the cat.
• Congenital abdominal wall hernias Intestine: strangulated obstruction / hernia occur on the cranial ventral midline (often associated with peritoneopericardial hernia), at the umbilicus, or in the inguinal region Inguinal hernia.
• Omphalocele is a large midline umbilical and skin defect that permits abdominal organs to protrude from the abdomen. The abdominal organs are covered with amniotic tissue, until minor trauma ruptures this transparent membrane and results in evisceration.
• Gastroschisis is a congenital abnormality similar to omphalocele, but the abdominal wall defect is paramedian.
• A true inguinal hernia may be indirect or direct and both are uncommon. Indirect inguinal hernia, (the more common of the two), occurs when tissue protrudes through the evagination of the vaginal process in females or the vaginal tunica in males (it is also called a scrotal hernia in males). Direct inguinal hernia involves herniation of tissue through the inguinal rings, adjacent to the normal evagination of the vaginal process or vaginal tunica. Direct inguinal hernias are usually large and do not incarcerate organs.

• Diaphragmatic hernias may be asymptomatic. Pleuroperitoneal or peritoneopericardial hernias may present with dyspnea or signs of gastrointestinal dysfunction and/or obstruction. Peritoneopericardial hernias may also present with signs of right-sided heart failure, due to cardiac tamponade. Patients with hiatal hernias usually present for anorexia, regurgitation, vomiting, dysphagia, salivation and respiratory distress.
• Abdominal wall hernias may be asymptomatic, although a nonpainful swelling is usually apparent. There may be signs referable to gastrointestinal or urinary tract obstruction and shock if the abdominal organs or bladder, respectively, are incarcerated. The swelling may become painful and discolored if the hernial contents are incarcerated.

• Pleuroperitoneal hernia: usually noted in young animal, but may be an incidental finding in an adult.
• Peritoneopericardial hernia: although present at birth may remain asymptomatic for years.
• Hiatal hernia : congenital cases usually present in younger animals, acquired hiatal hernia can occur secondary to upper airway obstruction and present at any age.
• Cranial ventral midline hernia: congenital and present in younger animals.
• Umbilical hernia: congenital. In some cases, it may not be apparent until maturity, when the animal has a condition causing increased abdominal pressure, such as obesity, trauma, or protracted straining.
• Omphalocele and gastroschisis are obvious in the neonate and may be fatal.
• Inguinal hernia: congenital inguinal hernias are rare. It is possible that a weakness is present at birth, and herniation of local organs/tissues occurs later in life.

• Peritoneopericardial hernia: Domestic long hair cats, Himalayans and Persians Persian longhair have an increased prevalence in some studies.

• Congenital hernias occur when there is abnormal fetal development. The reason for this may be genetic (hereditary) or may be due to other factors, such as teratogenic agents.
• Pleuroperitoneal hernia involves incomplete development or failure of fusion of the pleuroperitoneal membrane across the pleuroperitoneal canal during development. It is thought to have an autosomal recessive mode of inheritance.
• Peritoneopericardial hernia is usually congenital. It is not known if it is heritable. Peritoneopericardial hernia may occur with other congenital abnormalities including sternal defects, cranial midline abdominal wall hernia, umbilical hernia, abnormal hair swirl pattern on ventral midline, ventricular septal defect or other cardiac defect, and pulmonary vascular disease. These combinations of congenital abnormalities are due to accidents of embryogenesis rather than inheritance.
• Hiatal hernia is usually congenital but may occur with trauma or severe respiratory distress. Trauma may damage diaphragmatic nerves and muscles, resulting in hiatal laxity. In patients with upper respiratory obstruction, reduced intrathoracic pressure during inspiration may contribute to esophageal reflux and visceral herniation.
• Ventral abdominal hernia may occur with other congenital defects,
• Most umbilical hernias are thought to be inherited, and may be polygenetic. Acquired causes of umbilical hernia are uncommon and usually due to excessive traction on the umbilical cord at parturition, or severance of the cord too close to the abdominal wall.
• Inguinal hernias are rare and have not been shown to be heritable in the cat to date. Acquired inguinal hernias have been reported following trauma.

• Pleuroperitoneal hernia may be fatal if the stomach, spleen, and small intestine herniate through the left dorsolateral diaphragmatic defect. Animals are dead at birth, or develop cyanosis and dyspnea and die soon after birth. Compression and atelectasis of lung lobes by the hernia can cause hypoventilation, ventilation/perfusion mismatch Ventilation perfusion mismatching, and hypoxia. Bloating of the stomach within the thoracic cavity can compress the lungs, leading to respiratory insufficiency and death although this appears to be less common in cats than dogs with a herniated stomach.
• Peritoneopericaridal hernia may cause no dysfunction, and these animals are asymptomatic. The most commonly herniated organ is the liver. Falciform ligament, omentum, spleen, small intestine, and (rarely) stomach may also herniate into the pericardial sac. Pathologic changes are related to which abdominal organs are entrapped or compromised.
• Incarceration of the liver in the pericardial sac can cause hepatic venous stasis, hepatic necrosis, biliary tract obstruction and jaundice. The resulting extravasation of fluid results in pericardial effusion Pericardial disease, ascites, or a combination of both.
• Effusion or the presence of viscera in the pericardial sac can cause cardiac tamponade with signs of right-sided heart failure (due to interference in venous return.)
• Compression by the hernia can reduce lung expansion and cause respiratory insufficiency. The severity of compromise depends on the volume and rate of expansion of the herniated tissue.
• Incarceration of the intestine can cause partial or complete obstruction to passage of ingesta. Obstruction of the stomach or proximal small bowel can cause vomiting with subsequent dehydration, metabolic alkalosis Acid base imbalance, electrolyte disturbances, and altered cardiac electrical conduction. Compromise of blood supply to the bowel can cause ischemic necrosis, intestinal perforation, and abscessation.
• Herniation of the stomach is rare, but could result in gastric bloating or signs of gastric obstruction.
• Peritoneopericaridal hernia has been implicated as a cause of pericardial cyst formation.
• Hiatal hernia primarily causes problems related to gastroesophageal reflux, such as esophagitis  Esophagitis and aspiration pneumonia  Pneumonia. Signs of esophagitis include vomiting Vomiting, regurgitation Regurgitation, and hypersalivation. Decreased esophageal motility and megaesophagus Megaesophagus can occur secondary to hiatal hernia. Upper airway obstruction may exacerbate or cause clinical signs of hiatal hernia. A large hiatal hernia could contain spleen, liver, and intestine, and could interfere with cardiorespiratory function.
• Abdominal wall hernias (ventral midline, umbilicus, or inguinal) have varying pathophysiology depending on what tissue has herniated and whether it is incarcerated. In general, very large or very small hernias appear to have a lower risk of incarceration.
• Herniation of a liver lobe, spleen or omentum rarely causes major problems unless strangulation occurs. Strangulation may be caused by constriction of the blood supply at the hernia ring or torsion of a vascular pedicle. Strangulation results in arterial and/or venous occlusion, which causes tissue ischemia and necrosis. Early venous obstruction causes organ engorgement and can result in arterial stagnation. Arterial stagnation or obstruction causes rapid organ necrosis if collateral blood supply is insufficient.
• Obstruction of the bowel can cause electrolyte, acid-base, and fluid imbalances, which may lead to shock Shock. Strangulated hollow organs may cause loss of body fluids by sequestration. Bacteria and toxins can be absorbed systemically, causing septicemia Shock: septic or shock. Strangulated bowel may also rupture, leading to loss of blood or body fluids and septicemia.
• Obstruction of the bladder (inguinal hernia) can cause azotemia Azotemia, hyperkalemia  Hyperkalemia, and metabolic acidosis. Death can occur in 2 or 3 days if the obstruction is not relieved.

• Prevalence of most congenital hernias in cats is unknown but low.
• In one study Persian cats had a higher prevalence of peritoneopericardial hernia, another study reported a higher prevalence within domestic long hair and Himalayan cats.

• Pleuroperitoneal hernia: may die at birth or may develop dyspnea later in life, or may be incidental finding.
• Peritoneopericardial hernia: may present for gastrointestinal dysfunction, dyspnea or cardiac failure, or may be incidental finding.
• Hiatal hernia: typically present for regurgitation.
• Cranial ventral midline hernia: nonpainful swelling cranial to the umbilicus. May have signs of intestinal obstruction. May also have signs referable to a concurrent peritoneopericardial hernia.
• Umbilical hernia: nonpainful swelling over the umbilicus.
• Inguinal hernia: nonpainful swelling in the inguinal region, usually unilateral. May have signs of bowel or bladder obstruction depending on the hernial contents.

• Peritoneopericardial hernia: often asymptomatic for years. May suddenly develop dyspnea or gastrointestinal signs as an adult.
• Hiatal hernia: clinical signs of regurgitation may be seen after weaning onto solid food. Acquired hiatal hernia may develop at any age, sometimes after trauma.
• Cranial ventral midline hernia: swelling or defect palpable at birth. May develop signs related to incarceration of abdominal organs.
• Umbilical hernia: swelling near umbilicus noted soon after birth.
• Inguinal hernia: swelling in inguinal region apparent at birth (if truly congenital). Inguinal hernias may be acquired in adults, usually as a result of increased intra-abdominal pressure or trauma. There is some speculation that acquired hernias may be caused by an underlying congenital muscle weakness.

• Peritoneopericardial hernia: respiratory signs can include dyspnea, tachypnea, coughing, wheezing. Gastrointestinal signs can include anorexia, polyphagia, vomiting, diarrhea. Other nonspecific signs include weight loss, abdominal pain, ascites, exercise intolerance, shock and collapse. Signs of hepatic encephalopathy Hepatic encephalopathy (head pressing, blindness, convulsions) have been reported with liver incarceration. Some animals are asymptomatic.
• Hiatal hernia: hypersalivation and drooling, frequent regurgitation of viscous fluid, hematemesis, vomiting, dysphagia, anorexia, weight loss, dyspnea, orthopnea, and exercise intolerance. May be asymptomatic.
• Cranial ventral midline hernia: nonpainful swelling cranial to the umbilicus. May have signs of intestinal obstruction. May also have signs referable to a concurrent peritoneopericardial hernia.
• Umbilical hernia: soft, round mass at the umbilical scar. Firm if fat or another structure is entrapped. If viscera are entrapped, may have a firm, irreducible, painful mass and acute gastrointestinal signs. Signs of intestinal obstruction include acute abdominal pain, vomiting, depression, and anorexia. Intermittent intestinal dysfunction may occur if intestines are involved in the hernia, even if reducible.
• Inguinal hernia: unilateral or bilateral soft, doughy, painless mass in the inguinal region. Scrotal hernias are usually unilateral and strangulation of abdominal tissues is common. A painful swelling with bluish-black discoloration of the tissue may be noted if intestinal strangulation has occurred. Vomiting, abdominal pain and depression suggest entrapped bowel. Anuria or stranguria occur with bladder obstruction.

• Peritoneopericardial hernia: physical examination may be unremarkable. Concurrent sternal, costal arch, or abdominal wall defects may be apparent as a bulge or may be detected by palpation. Auscultation may reveal muffled heart sounds Cardiac sounds: overview, abnormally positioned heart sounds, or cardiac murmurs due to concomitant cardiac defects. Signs of right-heart failure may be present due to cardiac tamponade. Electrocardiogram ECG: overview may show decreased voltages, electrical alternans due to pericardial effusion, or axis deviation due to cardiac displacement.
• Hiatal hernia: the animal may be cachectic and dehydrated. Esophagoscopy Esophagoscopy reveals mucosal hypermia, inflammation or ulceration of the distal esophagus. Megaesophagus Megaesophagus or aspiration pneumonia Pneumonia may be apparent on thoracic radiographs Radiography: thorax. A soft tissue mass dorsal to the thoracic vena cava and absence of the right crus of the diaphragmatic border are suspicious for a hiatal hernia. Herniation may be intermittent, making diagnosis difficult.
• Abdominal wall hernias: with multiple congenital defects, incarcerated hernias, or signs of obstruction or strangulation, examine with radiographs or ultrasound. Dilated, displaced organs outside the abdominal wall, an obstructive intestinal pattern, or free abdominal fluid warrants surgical exploration. With intestinal obstruction, there may be alterations in electrolytes, acid-base status, and fluid balance. Fine needle aspirate of the hernia is usually unrewarding.
• Cranial ventral midline hernia: examine for other congenital defects, such as incomplete sternal fusion, peritoneopericaridal hernia, congenital heart defects Congenital heart disease: overview and portosystemic shunts Congenital portosystemic shunt (CPSS).
• Umbilical hernia: with small, reducible hernia, no other diagnostics are needed. The hernial ring may be difficult to palpate if it has closed around falciform fat or omentum. If the hernia is warm or painful and the contents are irreducible, intestinal incarceration should be suspected. Always check for other congenital defects.
• Inguinal hernia: palpate the inguinal canal and determine if mass is reducible. It may help to put dog in dorsal recumbency and elevate the hindquarters to reduce caudal intra-abdominal pressure. Be sure to palpate both inguinal canals. Radiographs, contrast radiographs, or computed tomography can be helpful in identifying hernia contents, especially if it contains intestine, uterus or bladder. Ultrasound may also be helpful with scrotal hernias to assess testicular blood flow and determine if hydrocele or spermatic cord torsion is present. Contrast cystography can define the bladder location. Azotemia Azotemia, hyperkalemia  Hyperkalemia, and metabolic acidosis Acid base imbalance may occur with bladder obstruction.

• Peritoneopericardial hernia: cardiomegaly or pericardial effusion Pericardial disease.
• Abdominal wall hernias (cranial abdominal, umbilical, inguinal): abscess, cellulitis, seroma, hematoma, lipoma, and neoplasia. Also consider mammary tumor or cyst, and lymphadenopathy as differentials for an inguinal hernia. Differentials for scrotal hernia include orchitis, trauma with severe scrotal inflammation, and tumors of the testes or scrotum. Femoral hernias are acquired (usually due to blunt trauma), and not congenital. They may be confused with inguinal hernias due to their proximity. Femoral hernias are rare.

• Peritoneopericardial hernia: pericardiocentesis  Pericardiocentesis is indicated if effusion from a herniated liver is causing cardiac tamponade. Nasal oxygen Nasal oxygen administration or oxygen cage may be benefical for dyspneic animals. Elevation of the forelimbs, with the animal in sternal recumbency may help with ventilation.
• Hiatal hernia: elevated feeding, antacids, H2 antagonists (cimetidine Cimetidine, ranitidine   Ranitidine), antisecretory drugs (omeprazole Omeprazole), and prokinetic agents (metaclopramide Metoclopramide, cisapride Cisapride) may be used to control clinical signs. If medical therapy is not effective within 30 days, surgical correction is recommended.
• Cranial ventral midline hernia: very small and very large hernias have less risk of organ entrapment and may be monitored initially. Surgical correction can be performed at the time of elective spay or castration Castration. If the hernia is about the size of the intestinal diameter, surgically repair should be considered sooner to prevent potential strangulation of bowel.
• Umbilical hernia: most small, reducible hernias contain only fat and are of little significance. Spontaneous closure of a small hernia may occur within the first 6 months of life. Most can be surgically repaired at the time of elective spay or castration during routine body wall closure, or monitored indefinitely.
• Omphalocele: immediate surgical repair is indicated to prevent organ damage or contamination.
• Inguinal hernia: if the bladder is herniated and urination is obstructed, the bladder should be immediately decompressed by needle cystocentesis Cystocentesis, urethral catheterization  Urethra: catheterization, or tube cystostomy; followed by diuresis with intravenous fluids. Hernia repair may be performed once the cat is metabolically stable.
• Cats with strangulated hernias should be treated with appropriate intravenous fluid therapy Fluid therapy: overview to restore body fluid, acid-base, and electrolyte balance. Appropriate antimicrobial and shock therapy should be instituted if necessary prior to emergency surgical correction of the hernia. Manual reduction of strangulated organs should not be attempted.

• Peritoneopericardial hernia: surgical repair is generally performed as soon as it is diagnosed. If it is performed in a young animal (2-4 months of age), it is unlikely that adhesions will be present, and the pliable nature of tissues in a young animal facilitate closure of large defects. Early correction may prevent acute decompensation. If the hernia is not diagnosed until the animal is older, conservative management may be used, but there is a risk of a progression of clinical signs, which could necessitate emergency surgery and/or result in death. Generally surgical management is preferred. A ventral midline incision is made. The sternum may need to be incised to enlarge the opening and facilitate return of viscera to the abdomen. Adhesions are rare. Incarcerated liver lobes may be excised if necrotic. Suturing the diaphragm will simultaneously close the pericardial sac and the hernia, repair of this hernia usually does not involve invasion into the pleural space. If the defect is very large, the pericardium may be incised cranial to the diaphragm and used as a flap to close the defect. Air may be aspirated from the pericardial sac or pleural cavity or both if necessary. If continued pneumothorax Pneumothorax or effusion is anticipated, a chest tube may be placed. Concomitant sternal and abdominal wall defects are corrected during closure of the celiotomy.
• Hiatal hernia: surgical repair for animals unresponsive to medical management includes closure of the esophageal hiatus, esophagopexy, and gastropexy.
• Cranial ventral midline hernia: return viable herniated contents to their normal location. The hernia opening may be surgically enlarged to facilitate reduction of the herniated organs. Devitalized or unhealthy tissue is resected. Break down any adhesions, excise the hernial sac, and debride the hernial ring. Close the hernia by approximation of local tissues. Prosthetic implants may be used if primary closure without excessive tension is not possible.
• Umbilical hernia: any incarcerated fat is excised and the body wall is closed routinely. Debridement of the hernial ring is unnecessary.
• Inguinal hernia: an incision is made lateral to the inguinal ring. The hernial sac is opened to evaluate viability of the contents. Nonviable tissue is resected and viable tissue is reduced. If reduction is difficult, the inguinal ring is enlarged by an incision made through the ring in a craniomedial direction. The external inguinal ring is sutured, leaving room caudally for the external pudendal vessel; genital branch of the genitofemoral nerve, artery and vein; and spermatic cord in an intact male dog or round ligament in a female. Bilateral castration is recommended to reduce the chance of hernia recurrence. For bilateral hernias, a midline incision allows closure of both inguinal hernias through one skin incision. For incarcerated or strangulated inguinal hernias a midline abdominal incision is made to allow abdominal exploration in addition to hernia repair. Necrosis of descended testicle may occur secondary to vascular obstruction, and orchiectomy is required if the cat is not already neutered. If the uterus is contained within the hernia, the cat should be spayed. If the uterus is viable and is preserved, there is an increased risk for hernia recurrence with future uterine enlargement or during parturition. Antibiotics are indicated prior to surgery if intestinal strangulation is suspected  Intestine: strangulated obstruction / hernia.

• Diaphragmatic hernias Diaphragm: hernia: monitor for hypoventilation, hypoxia, and respiratory acidosis. Potential complications include pneumothorax, pulmonary edema Lung: pulmonary edema, hemothorax Hemothorax, and pain. Ascites may occur with increased hepatic venous drainage pressure.
• Hiatal hernia: feeding, H2 antagonists, and metoclopramide are recommended until megaesophagus resolves and motility improves as demonstrated by fluoroscopy. Complications include reherniation, gastric tympany, vomiting, dyspnea, and continued gastroesophageal reflux with esophagitis. Pneumothorax can occur during esophagophrenic junction division and must be managed appropriately. Problems are more likely with fundoplication, this technique is not recommended in cats.
• Abdominal wall hernias: monitor for reherniation. Postoperative wound care is routine, and activity should be limited until the incision has healed.
• Inguinal hernia Inguinal hernia: most common complications are hematoma or seroma. Other complications include dermatitis, infection, peritonitis, sepsis, and recurrence.

• Good to excellent for uncomplicated hernias.
• Peritoneopericardial hernia: prognosis is good to excellent if there is no significant liver damage, and recurrence is uncommon. Concurrent sternal and abdominal wall defects have no adverse effects on survival. However, prognosis is poor if there are concomitant cardiac defects.
• Hiatal hernia: prognosis is good with surgical anatomic restoration technique.
• Omphaloceles, umbilical hernias that contain strangulated organs, or the presence of multiple defects carry a guarded to poor prognosis. Prognosis depends on preoperative status of the animal, nature of the herniated contents, and extent of the defect. Animals often die or are euthanized at birth.

• Hiatal hernia that is over reduced can cause esophageal obstruction with accumulation of ingesta cranial to the stenosis.
• When the abdominal cavity has adapted to a small intra-abdominal volume over a long period of time, reduction of the herniated organs and primary closure of the defect may be difficult or impossible. Forcing reduction of the organs may cause excessive tension on the repair and acute pulmonary complications due to diaphragmatic restriction.
• Obesity and increased intra-abdominal pressure from vomiting, coughing, tenesmus, or stranguria increase the risk of dehiscence.
• Most hernia recurrences are due to infection, excessive tension on the repair, incorporating weak tissue in the repair, poor anatomic reconstruction, or use of inappropriate suture material.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Reimer S B, Kyles A E, Filipowicz D E et al (2004) Long-term outcome of cats treated conservatively or surgically for peritoneopericardial diaphragmatic hernia: 66 cases (1987-2002). JAVMA 224 (5), 728-732 PubMed.
• Lorinson D, Bright R M (1998) Long-term outcome of medical and surgical treatment of hiatal hernias in dogs and cats: 27 cases (1978-1996). JAVMA 213 (3), 381-384 PubMed.
• Voges A K, Bertrand S, Hill R C et al (1997) True diaphragmatic hernia in a cat. J Vet Radiol Ultrasound 38 (2), 116-119 PubMed.
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• Robinson R (1977) Genetic aspects of umbilical hernia incidence in cats and dogs. Vet Rec 100 (1), 9-10 PubMed.
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Other sources of information

• Hunt G B, Johnson K A (2003) Diaphragmatic, pericardial, and hiatal hernia. In: Slatter D (ed) Textbook of Small Animal Surgery, 3rd ed, pp 471-487.
• Read R A, Bellenger C R (2003) Hernias. In: Slatter D (ed) Textbook of Small Animal Surgery, 3rd ed, pp 446-448.
• Smeak D D (2003) Abdominal hernias. In: Slatter D (ed) Textbook of Small Animal Surgery, 3rd ed, pp 449-470.