Herniorrhaphy (Proceedings)

Hernia

Hernia refers to the abnormal protrusion of an organ or tissue through a normal or abnormal opening in the abdominal muscles or in the diaphragm. The term is commonly used to denote bulging of organs through the muscular part of the abdominal wall.

Hernias are classified according to type and location. According to type they are:

Reducible - the hernia contents can be returned to the abdominal cavity by manipulation.

Irreducible - the hernia contents cannot be returned to the abdominal cavity without surgical intervention; adhesions of the herniated tissues to adjacent structures.

Strangulated - the hernial contents are constricted at or by the hernial ring, resulting in vein congestion and eventual development of endotoxin shock and gangrene of the herniated tissue.

Umbilical Hernias

In an umbilical hernia there is a protrusion of omentum, the fat associated with the falciform ligament, or part of an organ through an open umbilical ring. The hernial contents are enclosed in a visible sac composed of skin, subcutaneous tissue and peritoneum. In hernias of the umbilical cord, the viscera pass through the abdominal wall, through a dilated umbilical cord, and are not covered with skin or peritoneum. Umbilical hernias are common and there is no sex predilection, they do, however, show a breed and familiar risk. The incidence is low in the domestic cats however; a high incidence has been shown in Cornishrex cats. Breeds of dogs showing high risks are Airedale Terrier, Basenji, Pekingese, Pointer and Weimeraner. These hernias probably are congenital and hereditary. They result from the failure of abdominal muscles to fully develop. There is evidence that the size of the umbilical ring is governed by two or more recessive genes.

Some animals with umbilical hernias have poorly developed abdominal muscles surrounding the hernia. The rectus muscles and aponeuroses of the two oblique muscles are hypoplastic. The midline of the abdomen appears to consist solely of a wide and thin linea alba that may extend from the xiphoid cartilage to the pubis.

Some umbilical hernias may be acquired. For example, the umbilicus may be enlarged or weakened if the cord is severed too close to the abdominal wall or if the bitch chews the cord, If the umbilical cord is handled carelessly during a cesarean section, umbilical hernias may result.

Clinical Signs

An obvious protrusion in content of the ventral abdominal wall, cranial to the midpoint between the pubis and xiphoid cartilage. The hernial sac size will vary but usually is small. Palpation reveals a soft fluctuating mass that is painless. With gentle manipulation the hernial contents can be returned to the abdominal cavity. When the sac has been ruptured in this manner the umbilical ring can be palpated. Small firm hernias consist of a portion of the falciform ligament or a piece of omentum. These tissues may become adherent to the skin and resist reduction, Large firm masses of the umbilical region may reflect cellulitis, abscess formation, or the presence of intestine. With an abscess or cellulitis, there is inflammation, fever, leukocytosis and pus accumulation, When the intestine becomes strangulated, signs of obstruction are present. This should prompt a radiographic examination.

Treatment

Most umbilical hernias in puppies are small, firm, irreducible, and of no clinical significance. In the female puppies the hernia may be reduced and corrected when the animal is presented for ovario-hysterectomy. Small hernias in puppies may correct themselves spontaneously before the animal reaches maturity. Periodic reduction of small hernias, together with bandaging, has been attempted to encourage closure of the umbilical ring. This technique has demonstrated limited success. Large hernias require surgical correction to prevent strangulation and for cosmetic reasons.

All operations for umbilical hernias are performed with the patient in dorsal recumbency. With small hernias, a single midline incision is made directly over the hernial sac and extended past the cranial and caudal limits of the ring. For large hernias an elliptical incision and removal of redundant skin may be necessary.

The hernial sac is isolated from its attachment to the skin and subcutis tissue down to and including the umbilical rim. Small hernial sacs that have no internal adhesions may be simply inverted into the abdominal cavity. The edge of the hernial ring is excised and debrided, and then apposed with a series of simple interrupted or horizontal mattress sutures of monofilament steel or PDS.

Closure of a large hernial ring places considerable tension on the sutures, and may require non-absorbable suture material, such as stainless steel, Occasionally adequate apposition will require incising the external lamina of the rectus sheath on each side of the hernial ring.

Removing the fundis of the peritoneal sac and remnants of the urachis is required for large hernias, When the contents of the hernial sac have been replaced in the abdominal cavity, mattress sutures are placed across the neck of the sac and the redundant portion is removed. An alternate method is to expose the hernial sac by making a longitudinal skin incision from a point cranial to the sac to a point caudal to it The skin is removed carefully from the hernial sac and the dissection is continued to expose its neck and the hernial ring. The sac is opened and any adhesions are broken down and the contents are then replaced in the abdominal cavity. The peritoneum is closed at the hernial ring with simple interrupted sutures of PDS and the redundant portion of the sac is removed. The rectus muscles are apposed with a series of interrupted sutures of steel. All fat must be removed from the rectus sheath. The superficial fascia over the rectus muscle is immobilized to form flaps that can be imbricated or pulled medially to overlap the hernial site and reinforce the wound. The skin is closed with non-absorbable sutures or skin staples.

Post-Operative Care

Complication following repair includes peritonitis, evisceration and recurrence. Administration of an antibiotic is indicated to prevent infection; Evisceration is best prevented by good surgical technique and confining the patient to a cage or otherwise limiting its activity for the first post-operative week

Ventral Abdominal Hernias

A ventral abdominal hernia is one in which there is a prolapse of abdominal contents through the abdominal wall at any point other than the umbilicus or inguinal ring. This hernia is acquired when an animal is kicked or struck by a car. It has been described as a false hernia because it does not occur through a natural or potential body opening. Ventral herniation may result when small dogs are mauled by large animals and it is not unusual for the hernia to develop some weeks following the original injury.

The incidence of ventral hernia is low. Its most common location is in the flank near the pelvis. This has been attributed to the assumption that abdominal muscles have greater elasticity at their costral attachments at the linea alba and at the prepubic tendon.

Clinical Signs

The most obvious sign is asymmetry or swelling of the abdominal region. The consistency of the swelling depends on the contents and the presence or absence of infection. The size of the swelling may increase following sudden body movement or during coughing. Pain is often elicited upon palpation.

Diagnosis

If the muscle layer rupture is complete, it may be possible to identify loops of intestine, spleen or other abdominal viscera, In other cases, some of the muscle fibers are separated and swelling is obvious, but an unbroken muscle layer could prevent the viscera from migrating subcutaneously. The greatest swelling may not be at the site of ruptured muscles because viscera escaping through the abdominal muscles may migrate subcutaneously. It is often necessary to administer an anesthetic agent to facilitate a complete examination to determine the extent of the hernia and the planned surgical approach.

If the swelling is reducible, one may be able to tentatively identify intestine by its tendency to slip suddenly back into the abdominal cavity when palpated; omentum returns slowly. An incarcerated hernia feels turgid, and it is difficult to palpate the hernial opening. When adhesions are present, it may be possible to reduce the swelling, but the sac cannot be separated from its contents. An incarcerated hernia must be differentiated from an abscess, hematoma, cyst or neoplasm.

Radiographic Diagnosis

Radiographs may reveal gas filled loops of intestine located subcutaneously in the lateral or ventral abdominal wall. There may be subcutaneous emphysema if the intestinal wall or skin has been perforated.

Prognosis

In most cases, a hernia of long-standing is less serious than a recent one, The fact that it has been present for some time without causing difficulty is in itself reassuring. Any hernia is a potential hazard to the health of the animal because the hernial contents are more exposed and vulnerable to trauma than when protected by the body wall. A hernia that can't be reduced is more dangerous than one that can because it is more likely to become strangulated. Strangulation is more likely if the sac is large in relation to the size of the rings. The prognosis is poor if the strangulated tissues have become gangrenous.

Treatment

In hernias of traumatic origin, the animal should be examined for evidence of shock. if shock is associated with hemorrhage as a result of hepatic, renal or splenic rupture, immediate surgery may be necessary. The usual treatment of shock should be instituted and surgery should be delayed until the risks attending anesthesia are minimized. During the course of this treatment, strangulation may be prevented by reducing the hernia while the patient is under the influence of a tranquilizer or narcotic and the abdomen bandaged to prevent recurrence.

Surgical Repair of Ventral Hernia

When multiple hernias exist an attempt should be made to reach them with as few incisions as possible. After entering the abdominal cavity, the organs should be inspected and repaired if necessary. The rent in the abdominal wall is closed in layers. This may be simple with recent hernias because the various muscles are easily identified. In older hernias identification and apposition is more challenging. The sheath of the deepest muscle layer is sutured first; this is the transversus, which is identified. by its dorsoventral fibers and the fact that the transverse fascia and peritoneum adhere to its deepest surface, The internal abdominal oblique is sutured next, its fibers run cranioventrally. The external abdominal oblique with caudoventral fibers is sutured last.

Stainless steel or non-absorbable suture material may be used for closing a ventral hernia. When identification of the torn muscle edges is not possible, they are apposed as well as possible with a series of interrupted sutures. With large defects, when apposition is impossible or great tension will be exerted on the suture line, the wound may be reinforced with plastic* or wire mesh. Synthetic absorbable suture is used for placing the mesh. Mesh is cut to extend 3 - 5 cm beyond the wound edges and sutured using simple interrupted pattern.

Post-Operative Care

Complication can include peritonitis, evisceration and recurrence. Antibiotics are indicated to prevent infection; Evisceration is best prevented by confining the patient to a cage or otherwise limiting activity for one week post-operatively. Dressing of the wound with Telfa Wet Pruf Pad over the suture line and drain opening, followed by a support bandage around the abdomen, aids in the healing process. Careful client education regarding signs of wounds dehiscence, evisceration and infection are of primary importance.

Inguinal Hernias

These hernias are characterized by protrusion of intestine or other viscera through the inguinal canal. They are fairly common in the dog and occur more frequently in birches. Inguinal hernias are not common in the cat. In the birch inguinal hernias are found most often in the pregnant or old animal and the hernial sac may contain a gravid or diseased uterus. Inguinal hernias are rare in the neutered male dog. when present it may extend to become an inguinoscrotal hernia, Inguinal hernias in puppies may disappear spontaneously, Predisposition to inguinal hernia has been suggested and it may have a hereditary basis. A structural weakness can be present in the inguinal area of the bitch; The frequency of inguinal hernia in a pregnant birch may be attributed to increased abdominal pressure. Obesity can be a predisposing factor. The resistance of the mammalian inguinal region to herniation of viscera may depend on the neuromuscular reflex mechanism of the lower abdominal wall rather than on the resistance of the inguinal rings. Whether the lesion is congenital or acquired, there seems to be a structural defect in the region. The internal and external rings are almost superimposed and there is no intervening canal; thus a gap is present in the abdominal floor,

Clinical Signs

Inguinal hernia is manifested by a protrusion of abdominal contents near the inguinal canal. Although most inguinal hernias are unilateral, careful examination may reveal the condition to be bilateral, The hernial contents are soft, doughy, and painless on palpation; this varies, however, depending on the contents and length of rime that the hernia has been present. The swelling may be so small as to be obscured by the caudal mammary glands or fat pads. The swelling might be large enough to contain a gravid uterus or one with pyometra. When the hernia extends beyond the external ring in a caudal direction (labial hernia) it may be lateral to the vulva and may resemble a perineal hernia.

Diagnosis

If the hernia is easily reduced, determining the location of the hernial ring is possible. Reduction of the hernia may be assisted by elevating the hindquarters while the animal is in dorsal recumbency. When pressure in the caudal portion of the abdominal cavity is thus reduced, the hernial ring may be palpable.

If it's difficult or impossible to reduce the hernia because of incarceration or strangulation of intestine or growth of a fetus after herniation of the uterus, the diagnosis becomes more difficult. The swelling may be confused with a mammary tumor, cyst, hematoma or abscess.

An abscess is usually warm and accompanied by fever and leukocytosis. There are usually signs of pain when an abscess is palpated and the swelling is nor so freely movable as that of a hernia, Cysts and hematomas are not warm and usually take considerable time to develop. These are most easily diagnosed by palpation,' they are finn and may be lobulated or nodular. Lipomas in the inguinal region may be difficult to differentiate from a hernia, however It mast be kept in mind that a mammary gland or tumor may conceal a small hernia.

Exploratory puncture and aspiration of the swelling contents have been advocated as a diagnostic measure, but this should be done with caution.

Radiographic Diagnosis

Radiography is helpful to differentiate intestine, gravid uterus, or bladder in the hernial sac, Barium contrast material is helpful if the digestive tract is involved. When the herniated uteruses gravid and in late gestation, the fetal skeleton will be visible on scout films, If gestation has been less than 43 days, a lobulated fluid density will be apparent.

When the bladder is involved, signs of cystitis are associated with the hernia. After administration of 10% Sodium Iodide or air, a cystogram will reveal the presence of the bladder in the sac a decrease in the size of the hernia may be observed following urination or urinary bladder catheterization. Although some inguinal hernias may be readily diagnosed, in others the bulge in the inguinal region may be so insignificant as to defy detection, Only a small portion of the intestine may be incarcerated in the inner ring. These animals are presented with signs of intestinal obstruction. The cause of such a radiographically demonstrable obstruction may be ascertained only by exploratory laparotomy.

Surgical Correction

Ventral midline approach is used for all inguinal hernias allowing utilization of both inguinal rings and repair of bilateral hernias through a single incision. In addition, this incision maybe extended cranially without disruption of the mammary tissue or its' blood supply.

The incision is made from the cranial brim of the pelvis and brought cranial until adequate exposure of the sac is accomplished. Undermining of the mammary tissue and lateral retraction allows for exposure of the inguinal ring and sac. Blunt dissection frees the sac from the subcutaneous tissue. The hernial sac is opened and inspected Adhesions between the sac and viscera are removed and sac contents are returned to the abdominal cavity.

Often enlargement of the inguinal ring is accomplished in order to ease hernial reduction. Should bladder be included, aspiration simplifies the procedure.

After organ replacement, the sac is trimmed at the margins of the inguinal ring and the hernial ring sutured with simple interrupted (2-0) stainless steel.

Inspection is made of the opposite inguinal ring, vaginal process removed and inguinal ring sutured closed. Mammary tissue is replaced and a penrose drain inserted. Routine closure of skin follows.

Post-operative care includes an abdominal wrap bandage which eliminates dead space and helps the comfort of the patient. Drains are removed 3 - 5 days post-operatively.

Femoral hernia

This condition is rare but deserves mention because of the extreme caution required for its surgical reduction. Statistical evidence of breed or sex susceptibility is not available, The diagnosis is based on the presence of an enlargement of the femoral canal on the medial side of the thigh. The femoral and inguinal hernia can be difficult to differentiate. By standing the animal on its hindlimbs an inguinal hernia will be dorsal and medial to the pelvic brim. It tends to pass ventrally and medially toward the scrotum and is above the inguinal ligament. With a femoral hernia, the swelling is ventral to the inguinal ligament and ventral and lateral to the pubic brim. The technique used for repair of femoral hernias is almost identical to that used for inguinal hernias, except that care must be taken to prevent injury to the important femoral vessels.

Scrotal Hernias

This condition is rare. Strangulation is often encountered in untreated cases. Although firm evidence of inherited predisposition is lacking, an affected animal should probably be castrated unless a trauma etiology can be confirmed. The characteristic scrotal enlargement is usually unilateral, The contents of the hernia can often be reduced toward the inguinal canal, especially when the animal is placed on its back, with the hindquarters elevated.

Tumors of the testes may resemble the appearance of a scrotal hernia. Distinguishing them from a hydrocele or other testicular swellings may be accomplished by grasping the upper part of the scrotum between the thumb and finger. If the skin on both sides can be apposed above the swelling with nothing between it but the spermatic cord, the possibility of hernia can be eliminated,

Repair of Scrotal Hernia

This repair involves excising the skin over the external inguinal ring, isolating the hernial sac and reducing its contents through the inguinal canal into the abdominal cavity. If castration is intended, a chromic gut ligature of suitable size is transfixed and passed around the spermatic cord and hernia sac as close to the internal inguinal ring as possible. The spermatic cord and vessels it contains are severed distal to the ligature. The edges of the inguinal ring are opposed with stainless steel or other non-absorbable suture and the skin is sutured in the usual manner.

If the dog is not castrated, recurrence of the scrotal hernia is common. When castration is not performed, the hernia is reduced and sutures are inserted in the neck of the sac to obliterate it without constricting the spermatic cord, If the usual dilation of the inguinal canal is present, several sutures may be inserted in the fascia to partially close the opening. Skin is closed in the usual manner; attachment of the skin to underlying deep fascia helps to prevent edema,

Perineal Hernia

These hernias differ from other hernias in that the displaced organs are not usually within a peritoneal sac. A specific cause has not yet been established for perineal hernias and multiple causative agents are most likely. It has been attributed to failure or weakening of the fascia and muscles of the perineum, permitting abdominal or pelvic organs to prolapse into the space created by atrophy or injury of the pelvic diaphragm.

Although perineal hernias have been reported in the birch, it occurs most commonly in intact male dogs over 8 years old, It does, however, occur in young animals, A structural predisposition has been suggested and dogs with rudimentary tails such as Boston Terriers would be more susceptible. Also reported is a hormonal imbalance etiology. This theory is supported by evidence that some dogs with perineal hernia are concurrently afflicted with testicular tumors, prostates enlargement or enlargement of a cystic uterus musculinea.

Constipation has been cited as a factor in perineal hernia but this has not been firmly established as a cause but more often a result of prostatic enlargement.

Clinical Signs

Most patients are presented for examination because they have been observed straining to defecate. Also, a swelling lateral to and extending from some distance ventral to the anus is a common sign. The hernial swelling is soft and fluctuate and manipulation often results in reduction of contents. If the bladder and prostate are hernial contents then the swelling may be turgid. if the bladder has become incarcerated or strangulated due to distension with urine following herniation, reduction might only be possible by withdrawing urine from the bladder. A perineal hernia may be bilateral, in which case the whole perineal region is swollen and the anus is displaced caudally.

Diagnosis

A hernia is apparent when the contents of the swelling can be pushed back into the pelvic cavity. This may be facilitated by elevating the animal's hindlimbs. Simultaneous palpation of the perineal enlargement and rectal examination aids in determining whether there is continuity between the swelling and peritoneal cavity, Digital examination of the rectum often reveals a lateral deviation or diverticulum into the hernial area. This deviation results in accumulation of feces in the return, and causes the animal to strain. During the course of the examination, the feces can be removed from the diverticulum, It then will be possible to pass the finger into it and observe its movement under the skin, Affected patients may only display the usual signs of discomfort, but if the bladder becomes strangulated and distended with urine following herniation, the swelling may be greatly enlarged and the overlying skin may be tense, blue-red, and exude serum. It may or may not be possible to catheterize the bladder in this case. The diagnosis of bilateral hernia sometimes is difficult because its reduction is not easy. A large unilateral hernia may migrate ventral to the anus into the opposite side and appear to be bilateral.

Treatment

Most cases of perineal hernia are not emergency cases. However, those with acute complications, such as retroflexion of the bladder and inability to urinate, must be treated as emergencies.

Relief can often be obtained by passing a catheter into the bladder. if this is not possible, wine can be removed by performing paracentesis. A 20 gauge needle or smaller is adequate. Once the bladder is emptied, an attempt can be made to reduce the hernia. When the hernial contents have been reduced, the animal should be given a narcotic to minimize straining. Such patients are suitable candidates for surgery in 24 hours. Once the diagnosis has been established surgery should not be delayed. if surgery is delayed the patient should be fed a low-residue diet for 48 hours prior to surgery. The feces are then soft in consistency and the danger of post-operative wound disruption is reduced, Recurrence of perineal hernia is not common and has been reported to recur in two to forty percent of the cases.

Repair of Perineal Hernia

The hernial funnel extends from the pelvic cavity to the hernial sac lateral to the anus. The hernia is limited ventrally and laterally by the walls of the pelvis and medially by the rectum.

The levator ani is a thin fan-shaped muscle that arises from the pelvic surface of the ischium and pubis at the pelvis symphysis, the cranial border of the pubis and the pelvic surface of the shaft of the ilium. Iris inserted on the external anal sphincter and caudal vertebrae. The two muscles together with their fascial layers form the pelvic diaphragm through which the genitourinary and digestive tracts open to the outside, When these muscles separate, relax, or become atrophic, the abdominal or pelvic organs may push through the defect. The hernia occurs between the external anal sphincter and the levator ani muscles. if the perineal fascia which surrounds the anus and is confluent with the gluteal fascia stretches or ruptures, the hernial contents prolapse lateral to the anus and are confined only by the skin.

Surgical Technique for Perineal Hernia Repair

A purse-string suture is placed around the anus to prevent defecation during the operation. It is best to place the patient on its sternum and elevate the hindquarters. The tail is pulled forward and laterally to expose the perineal region. The operation is designed to reconstruct the pelvic diaphragm. Complete reconstruction may not be possible due to tearing or atrophy of muscle; closure of the hernial funnel and obliteration of space may be all that can be accomplished.

A half circle skin incision is made over the hernia and extended an adequate distance above and below the hernia to facilitate manipulation of the tissues. Frequently there will be no evidence of fascia and fibrous tissue, and the muscles will be atrophied and intermingled with omentum-like, necrotic, fatty tissue, The tissue strands must be disrupted between muscle layers and the fatty tissue ligated and removed as necessary. The area is likely to be hemorrhagic and blood serum escapes when the hernial sac is entered.

The herniated organs are replaced into the pelvic cavity by gentle manipulation and then a clear view of the funnel is obtained. On the medial side is the rectum, terminating at the anal sphincter. This usually is the only structure on the medial side into which sutures can be inserted. The muscular structures on the lateral side of the funnel are not easily seen but may be identified by palpation. The levator ani and coccygeus muscle are on the dorsolateral surface of the funnel, Stainless steel wire, nylon or catgut sutures are inserted through these muscles and into the dorsal part of the anal sphincter. Some surgeons feel chromic gut is best because it provokes a fibrous tissue reaction that contributes to the strength of repair, however, the author prefers stainless steel wire (26 gauge). The internal obturator muscle is also sutured to the ventrolateral aspect of the rectum,

Immediately below these sutures, additional ones are inserted between the anal sphincter and sacrotuberous ligament. This ligament is a fairly broad band that can be identified by passing the finger along the medial wall of the pelvis and hooking the finger backward. The ligament may be mistaken for bone. The lower portion of the opening is closed by inserting a series of sutures through the internal obturator muscle which lies on the floor of the pelvis, and the ventral surface of the anal sphincter. This is difficult because the structures lie deeply within the pelvis and careful manipulation is necessary.

When inserting the lower sutures between the head of the internal obturator muscle and ventral portion of the anal sphincter, care must be taken to avoid injuring the blood and nerve supply to the anus, The muscles of the anal sphincter are supplied by anal branches of the pudendal nerve and by the perineal arteries and satellite veins, These structures will be encountered in a band along the ventral aspect of the rectum. Injury to the nerve might result in fecal incontinence.

The sutures should not be tied until all have been inserted,' otherwise increasing difficulty will be encountered in placing the sutures. Following closure of the initial suture line an attempt is made to locate intact perineal fascia that may have retracted laterally. The edge of the fascia is grasped with an Allis forceps and a flap is formed by dissecting the outer surface of the fascia away from the overlying skin, The fascia flap is pulled medially and sutured to the most caudal portion of the anal sphincter Another series of sutures is inserted in the subcutaneous tissues and excessive skin is trimmed to assure adequate and accurate closure.

Possible complications following repair of a perineal hernia include fecal and urinary incontinence, wound infection from fecal contamination and lameness resulting from damage to the sciatic nerve during surgery. In severe cases, nylon mesh may be used to form a "diaphragm" that prevents the caudal displacement of the viscera,

Post-Operative Care and Prognosis

Routine prophylactic chemotherapy is advisable and a low residue diet should be fed to prevent excessive straining during defecation, In most cases recurrence is not a problem. Both sides of a bilateral hernia should not be operated at the same time since this would put too much stress on the external anal sphincter. A 4 to 6 week lag should occur between surgeries, unless a newer obturator lift method is employed.

Obturator Lift for Simultaneous Bilateral Perineal Hernia Repair

The approach to this surgery is identical to traditional repair, and after exposure herniated organs are retropulsed back into the abdomen. Identification of the external anal sphincter, sacrotuberous ligament and the internal obturator is severed at the point that it passes laterally over the body of the ischiurn, The muscle is then brought dorsally to fill the defect left by the hernia, Initial suture is placed between the lateral aspect of the external anal sphincter and the sacrotuberous ligament and gluteal fascia as far dorsal as possible in order to create a bed for the apex of the internal obturator is sutured to the caudomedial edge of the sacrotuberous ligament with 4 - 6 (1.0) nylon cruciate pattern sutures. The caudomedial border of the internal obturator is likewise sutured to the external anal sphincter. Replacement of all sutures before knot's are thrown facilitates the task. Layered subcutaneous closure is accomplished with gut to obturate dead space Skin closure is routine.

Congenital Abnormalities- Peritoneopericardial Hernia

This condition is referred to as congenital diaphragmatic hernia. It is a relatively common condition in which the septum transversum fails to develop properly resulting in incomplete separation of the peritoneal and pericardial cavities. This condition has been seen in many breeds from birth to 15 years of age, but most commonly in animals under 2 years.

Clinical Signs - Peritoneopericardial Hernia

Vomiting, anorexia, lethargy and diarrhea are common signs whereas dyspnea is an infrequent sign. Ventral abdominal hernias have also been present in affected dogs. This condition often goes undetected until radiographs are taken for reasons such as heart disease, gastroenteritis, pneumonia or neoplasia.

Diagnosis

Physical examination reveals intestinal sounds in the ventral portion of the chest, muffled heart sounds and on percussion the ventral area of dullness is increased, Radiography confirms the diagnosis by revealing an increase in the size of the pericardial shadow, which may have intestinal gas pattern in it. Some cases will present a more challenging diagnosis if the opening is small and omentum is the only abnormal tissue in the pericardial sac In these cases exploratory thoracotomy may be indicated to establish a diagnosis.

Treatment - Peritoneopericardial Hernia

The hernia is repaired through a ventral midline laparotomy similar to the repair of traumatic diaphragmatic hernia

Traumatic Diaphragmatic Hernia

This condition is usually the result of blunt trauma especially from automobile accidents. Diaphragmatic hernia should be considered in all patients with a history of trauma. It is believed that the diaphragmatic tear is the result of a sudden increase in intra-abdorninal pressure. The pressure differential is only momentary and the pressures equilibrate readily.

Clinical Signs - Diaphragmatic Hernia

This hernial condition maybe difficult to identify because of marked or absence of conventional presenting signs. Thus the patient maybe presented with imperceptible to life threatening clinical signs. The severity of the patient's condition is dependent upon several factors, the most important of which is a reduction in tidal volume. Loss of tidal volume is the result of a decrease in intra thoracic space due to the presence of abdominal visceral fluid or both. Other conditions that may be present are rib fractures, pneumothorax, lung contusion, and shock. A potentially more dangerous situation exists when the stomach is in the thorax and gas cannot escape causing it to become increasingly larger.

The clinical Signs most frequently seen in acute diaphragmatic hernia is dyspnea. Often the dog rests in a sitting position with the elbows abducted, Physical examination reveals intestinal sounds in the thorax, muffled heart sounds and reduced lung field. The area of dullness in percussion is increased. Careful abdominal palpation may reveal the absence of abnormal position of individual organs such as stomach, liver, and spleen. In a study of 11.6 dogs at Ohio State University, College of Veterinary Medicine, the most common organs displaced into the thorax in diaphragmatic hernia cases were in decreasing order - liver, small intestine, stomach, spleen, fluid and omentum. Other displaced organs were also reported such as pancreas, colon, gallbladder, cecum, kidney falciform ligament and uterus.

A dog suspected of having a diaphragmatic hernia should not be elevated by the hindquarters to see if the dyspnea becomes worse. This technique can cause sodden pressure on the lungs and heart when a large tear is present and can cause overwhelming interference with ventilation and venous return.

Radiographic Diagnosis

Lateral and dorsoventral radiographs often will confirm the diagnosis. The normal diaphragmatic line is usually absent in the radiographs. Gastric or intestine gas patterns and/or radiopaque organs such as liver or spleen may be visible in the thorax displacing normal thoracic viscera. It should be noted that the organs noted in the chest at the time of radiographs were not necessarily the same as those found. at operation. This is attributable to the free movement of viscera between pleural and peritoneal cavities in many patients. Diaphragmatic hernia maybe difficult to diagnose at the time of initial injury because of lack of clinical signs. The tear is subsequently reduced by cicatrization and gradually developing clinical signs, such as intermittent vomiting, anorexia, dyspnea or reduced exercise tolerance may be seen weeks, months or even years following the procedure.