Surgery of the Abdominal Cavity

Chapter 19


Surgery of the Abdominal Cavity



General Principles and Techniques





Preoperative Concerns


Celiotomy is performed for various reasons; it may be indicated for diagnostic (e.g., biopsying an organ) and/or therapeutic reasons. Many animals undergoing abdominal exploratory surgery have chronic disease, but some patients require emergency abdominal surgery because of acute clinical signs. Some conditions are life-threatening (e.g., gastric dilatation-volvulus, colonic perforation, severe hemorrhage), and appropriate therapy must be started promptly. Conditions that require surgery must be differentiated from those that can be managed medically. Although obviously unnecessary surgery must be avoided, surgery cannot always be delayed until one is certain the patient will benefit from it.


The decision to operate is based on the history and physical examination findings, radiographic and ultrasonographic studies, and laboratory analyses. Physical examination can be unreliable in predicting the severity of abdominal trauma. The inaccuracy associated with examining patients with acute abdominal disease, particularly that associated with trauma, can be attributed in part to the patient’s condition at the time of examination and delayed development of clinical signs associated with some injuries. Depressed or lethargic animals may not show pain during abdominal palpation. Clinical signs of hemorrhage often are inapparent immediately after trauma; delays of 3 to 4 hours between injury and development of shock and collapse are common in patients with hepatic or splenic lacerations. Therefore, animals that have suffered traumatic injury should be closely observed for at least 8 to 12 hours. Life-threatening hemorrhage becomes apparent before this time in most cases. However, animals with traumatic bilious peritonitis may not have overt clinical signs for weeks. Likewise, traumatic mesenteric avulsion is seldom associated with clinical signs until peritonitis develops, usually several days after injury. Sensitive diagnostic tests such as diagnostic peritoneal lavage (see p. 380) may help identify patients with significant abdominal trauma before overt clinical signs develop.



NOTE • Be aware that overt clinical signs associated with mesenteric avulsions or rupture of the biliary tract may not become evident for days to 2 weeks after injury.


Preoperative management of most animals undergoing exploratory laparotomy is dictated by the underlying abdominal disease. General observations include noting the animal’s attitude and posture, temperature, respiratory rate and effort, and heart rate and rhythm. Abdominal auscultation, percussion, and palpation plus rectal examination are indicated. Serial examinations are important to detect trends or deterioration in the patient’s status. An intravenous catheter should be placed for fluid and drug administration, and blood samples should be drawn. Useful initial blood work in an animal with acute abdomen includes complete blood count (CBC), platelet count, serum total protein and glucose concentrations, and blood urea nitrogen (BUN). Other laboratory tests (e.g., serum biochemistry profile, clotting parameters) can be performed, depending on the animal’s condition and the suspected underlying disease. Urine may be collected by means of cystocentesis or catheterization for urinalysis. An indwelling urinary catheter may be used to quantitate urinary output if necessary. Abdominal radiographs may detect peritoneal fluid (i.e., uroabdomen, peritonitis) or abnormal accumulations of air. Animals with acute abdominal signs of uncertain cause should have abdominocentesis, diagnostic peritoneal lavage (see p. 380) FAST (see p. 383), or a CT performed if radiographs are nondiagnostic. Electrolyte and hydration abnormalities should be corrected before surgery.



NOTE • If you note free air in the abdominal cavity of an animal that has suffered a recent traumatic injury, consider exploratory surgery; this finding may indicate rupture or perforation of the gastrointestinal tract.


Major abdominal evisceration may occur in dogs secondary to postsurgical dehiscence or trauma. In affected animals, the intestines typically are eviscerated and may have gross contamination with dirt or other debris (e.g., cat litter). Regardless of the inciting cause, exposure and contamination of the abdominal viscera warrant immediate surgical intervention. In a recent study of animals that had developed a postoperative major abdominal evisceration, all had recently undergone ovariohysterectomy (Gower et al, 2009). The authors noted that the preponderance of wound dehiscence leading to abdominal evisceration in animals undergoing ovariohysterectomy was likely a reflection that it is one of the most frequently performed abdominal procedures in small animals, rather than being a direct consequence of the procedure.



Anesthetic Considerations


The anesthetic management of animals with abdominal disease depends on the underlying disease. Animals that are not in shock can be premedicated with a benzodiazepine and opioid and induced with propofol, ketamine, or etomidate given intravenously to effect (Table 19-1). Table 19-2 provides suggested anesthetic protocols for animals that are in shock or that are debilitated.






Surgical Anatomy


The rectus sheath is composed of an external and an internal leaf (Fig. 19-1). The external leaf is formed by the aponeurosis of the external abdominal oblique muscle and a portion of the aponeurosis of the internal abdominal oblique muscle. The aponeurosis of the transversus abdominis muscle joins the external leaf near the pubis (see Fig. 19-1). The internal leaf consists of a portion of the aponeurosis of the internal abdominal oblique muscle, the aponeurosis of the transversus abdominis muscle, and the transversalis fascia. The internal leaf disappears in the caudal third of the abdomen, where the aponeurosis of the internal abdominal oblique muscle joins the external leaf, leaving the caudal rectus abdominis muscle covered only by a thin sheet of transversalis fascia and peritoneum (see Fig. 19-1).




NOTE • The linea alba is easier to locate near the umbilicus because it becomes thinner near the pubis.



Surgical Techniques


The abdomen generally is explored by means of a ventral midline incision. In most animals, the entire abdomen, including the inguinal areas and the caudal thorax, should be prepared for aseptic surgery to allow extension of the incision into thoracic or pelvic cavities if necessary. Prepping too small an area is a common mistake, particularly for abdominal exploration in trauma patients. To visualize all abdominal structures adequately, the incision must extend from the xiphoid process to the pubis. If only a specific abdominal structure will be examined, a shorter incision can be made. A caudal abdominal incision extending from umbilicus to pubis is adequate for bladder exploration; similarly, a cranial abdominal incision (i.e., umbilicus to xiphoid process) allows evaluation of liver and stomach. Occasionally, the midline incision is extended laterally at the xiphoid process (1 cm caudal to the last rib) to facilitate exposure of the liver, biliary system, and diaphragm. A paracostal (paralumbar) celiotomy can be used to expose the kidneys and adrenal glands; it is most commonly used for unilateral adrenalectomy.



NOTE • Always count surgical sponges before making the incision and before abdominal closure to help ensure that none are inadvertently left in the abdominal cavity.



Ventral Midline Celiotomy in Cats and Female Dogs


With the patient in dorsal recumbency, make a ventral midline skin incision beginning near the xiphoid process and extending caudally to the pubis (Fig. 19-2, A). Sharply incise the subcutaneous tissues until the external fascia of the rectus abdominis muscle is exposed. Ligate or cauterize small subcutaneous bleeders and identify the linea alba. Tent the abdominal wall and make a sharp incision into the linea alba with a scalpel blade. Palpate the interior surface of the linea for adhesions. Use scissors to extend the incision cranially or caudally (or both) to near the extent of the skin incision. Digitally break down the attachments of one side of the falciform ligament to the body wall, or excise it and remove it entirely if it interferes with visualization of cranial abdominal structures. Clamp the cranial end of the falciform ligament and ligate or cauterize bleeders before removing it.




Ventral Midline Celiotomy in Male Dogs


With the patient in dorsal recumbency, place a towel clamp on the prepuce and clamp it to the skin on one side of the body (Fig. 19-2, B). Drape the tip of the prepuce and clamp outside the surgical field. Make a ventral midline skin incision beginning at the xiphoid process and continuing caudally to the prepuce. Curve the incision to the left or right of the penis and prepuce (i.e., the side opposite the clamped prepuce) and extend it to the level of the pubis (see Fig. 19-2, B). Incise the subcutaneous tissues and fibers of the preputialis muscle to the level of the rectus fascia in the same plane as the skin incision. Ligate or cauterize large branches of the caudal superficial epigastric vein at the cranial aspect of the prepuce. Retract incised skin and subcutaneous tissues laterally and locate the linea alba and external fascia of the rectus abdominis muscle. Do not attempt to locate the caudal linea alba until subcutaneous tissues have been incised and the abdominal musculature fascia identified. Tent the abdominal wall and make a sharp incision into the linea alba with a scalpel blade. Palpate the interior surface of the linea for adhesions. Use scissors to extend the incision cranially or caudally (or both) to near the extent of the skin incision.




Abdominal Exploration


Systematically explore the entire abdomen. Various techniques may be used; however, every surgeon should develop a consistent pattern to ensure that the entire abdominal cavity and all structures in each animal are visualized and/or palpated (Box 19-1).



image Box 19-1   Systematic Exploration of the Abdominal Cavity




1. Explore the cranial quadrant.



2. Explore the caudal quadrant.



3. Explore the intestinal tract.



4. Explore the gutters.



Use moistened laparotomy sponges to protect tissues from drying during the procedure. If generalized infection is present, or if diffuse intraoperative contamination has occurred, flush the abdomen with copious amounts of warmed, sterile saline solution.


Historically, many different antiseptics (e.g., povidone-iodine, chlorhexidine) and antibiotics have been added to lavage fluids. Povidone-iodine is the most widely used antiseptic; however, this practice has not shown a beneficial effect in repeated experimental and clinical trials and may be detrimental in animals with established peritonitis because the carrier, polyvinylpyrrolidone, inhibits macrophage chemotaxis. Similarly, no substantial evidence indicates that adding antibiotics to lavage fluid benefits patients treated with appropriate systemic antibiotics. Room temperature lavage fluids should not be used in anesthetized patients. Heated lavage fluids are useful for increasing the temperature in dogs.


Remove the lavage fluid and blood and inspect the abdominal cavity before closure to ensure that all foreign material and surgical equipment have been removed. Perform a sponge count and compare it with the preoperative count to ensure that surgical sponges have not been left in the abdominal cavity.



Abdominal Wall Closure


The linea alba may be closed with simple interrupted sutures or a simple continuous suture pattern. The simple continuous technique does not increase the risk of dehiscence when properly performed (i.e., secure knots, appropriate suture material), and it allows for rapid closure. Preferably strong, absorbable suture material (e.g., polydioxanone [PDS], polyglyconate [Maxon], poliglecaprone 25 [Monocryl], glycomer 631 [Biosyn]) should be used for continuous suture patterns, and six to eight knots should be placed at each end of the incision line. Monofilament, nonabsorbable suture material (e.g., polybutester [Novafil], polypropylene [Prolene], nylon) has been associated with suture sinus formation and should be avoided. Surgical gut and stainless steel wire should not be used for continuous suture patterns.


On each side of the incision, incorporate 4 to 10 mm of fascia in each suture. Place interrupted sutures 5 to 10 mm apart, depending on the animal’s size. Tighten sutures sufficiently to appose but not enough to strangulate tissue, because too-tight sutures adversely affect wound healing. Incorporate full-thickness bites of the abdominal wall in the sutures if the incision is midline (i.e., through the linea alba; Fig. 19-3). Do not incorporate the falciform ligament between the fascial edges. If the incision is lateral to the linea alba and muscular tissue is exposed (i.e., paramedian incision), close the external rectus sheath without including muscle in the sutures. Do not attempt to include peritoneum in the sutures. Close subcutaneous tissues with a simple continuous pattern of absorbable suture material, and reappose the preputialis muscle fibers. Use nonabsorbable sutures (simple interrupted or continuous appositional pattern; see Chapter 8) or stainless steel staples to close the skin. Place skin sutures without tension.



For paracostal celiotomy, close the individual muscle layers with synthetic absorbable suture material in a continuous or interrupted pattern. Attempt to eliminate dead space between muscle layers. Appose subcutaneous tissue with absorbable suture in a continuous or interrupted pattern, and close the skin with nonabsorbable suture in a simple interrupted or continuous pattern.





Postoperative Care and Assessment


The abdominal incision should be checked twice daily for redness, swelling, or discharge. If the animal licks or chews at the incision, an Elizabethan collar or sidebar should be used to prevent iatrogenic suture removal. Early signs of altered wound healing include inflammation and edema. Swelling and serosanguineous drainage from the incision are consistent signs of acute incisional dehiscence. Dehiscence usually occurs 3 to 5 days after surgery, when minimal healing has occurred and the sutures have weakened; however, it may occur earlier if knots were tied improperly or if fascia was not incorporated into the sutures. Evisceration usually causes sepsis and severe blood loss secondary to mutilation of exposed intestine; the patient must be treated promptly. The abdomen should be bandaged, fluid therapy initiated, and broad-spectrum antibiotics given while the animal is prepared for surgery. If technical failure such as poor knot tying or improper suturing is suspected, the entire suture line should be removed and replaced. Débridement of the wound edges is unnecessary and delays wound healing. The intestine should be closely inspected for viability and damaged sections resected if appropriate (see p. 501). The abdominal cavity should be lavaged copiously with warmed, sterile saline. Open abdominal drainage (see p. 381) or suction drainage may be considered in animals with generalized peritonitis. Wound disruption after 10 to 21 days usually causes hernia formation rather than evisceration. Hernia repair in these animals may require excision of fibrotic tissues. Subsequent closure requires that tissue layers be accurately apposed.



Complications


Dehiscence (incisional hernias) and abdominal evisceration may occur if improper surgical technique is used (see the previous discussion). The most common causes of wound dehiscence in the early postoperative period are suture breakage, knot slippage or untying, and sutures cutting through tissue. A higher rate of dehiscence may be seen in animals with wound infection, fluid or electrolyte imbalance, anemia, hypoproteinemia, metabolic disease (e.g., hyperadrenocorticism, diabetes mellitus), immunosuppression (e.g., feline immunodeficiency virus [FIV], feline leukemia virus), or abdominal distention, or in those that have been treated with corticosteroids, chemotherapeutic agents, or radiation. Suture sinus formation has been reported with nonabsorbable suture material. Such cases require surgical resection of affected tissues and removal of offending sutures.





Specific Diseases



Umbilical and Abdominal Hernias



Definitions


External abdominal hernias are defects in the external wall of the abdomen that allow protrusion of abdominal contents; internal abdominal hernias are those that occur through a ring of tissue confined within the abdomen or thorax (e.g., diaphragmatic hernia, hiatal hernia). External abdominal hernias may involve the abdominal wall anywhere other than the umbilicus, inguinal ring, femoral canal, or scrotum. Umbilical hernias occur through the umbilical ring. The contents of true hernias generally are enclosed in a peritoneal sac; false hernias allow protrusion of organs outside a normal abdominal opening; therefore the contents seldom are contained in a peritoneal sac. Omphaloceles are large midline umbilical and skin defects.


Abdominal hernias may be defined according to their location (i.e., ventral, prepubic, subcostal, hypochondral, paracostal, or lateral). The cranial pubic ligament formerly was called the prepubic tendon.



General Considerations and Clinically Relevant Pathophysiology


Abdominal hernias generally occur secondary to trauma, such as vehicular accidents or bite wounds; however, they occasionally occur as congenital lesions. Congenital cranial abdominal hernias (i.e., cranial to the umbilicus) have been reported in association with peritoneopericardial diaphragmatic hernias in dogs and cats. Abdominal hernias are false hernias because they do not contain a hernial sac. When associated with blunt trauma, they arise as a result of rupture of the wall from within caused by an increase in intraabdominal pressure while the abdominal muscles are contracted. The most common sites of traumatic abdominal hernias are the prepubic region and the flank. Cranial pubic ligament hernias often occur in association with pubic fractures (Fig. 19-4). Paracostal hernias may allow migration of abdominal contents along the thoracic wall (see Fig. 19-4). In rare cases, the abdominal contents enter the chest through defects in the intercostal muscles. Nearly half of the animals that suffer from traumatic abdominal hernia have serious concurrent injuries, including orthopedic (e.g., pelvis) and soft tissue injuries; thus a thorough physical examination of all affected animals should be performed.



Umbilical hernias usually are congenital, caused by flawed embryogenesis (see Fig. 19-4). Umbilical vessels, the vitelline duct, and the stalk of the allantois pass through the umbilical ring in the fetus, but this aperture closes at birth, leaving an umbilical cicatrix. If the aperture fails to contract or is too large or is improperly formed, a hernia results. These hernias are lined by a peritoneal sac and are considered true hernias. The cause of umbilical hernias is seldom known, but most are thought to be inherited. Many male dogs with umbilical hernias are cryptorchid. Omphaloceles allow abdominal organs to protrude externally (eviscerate). The abdominal contents initially are covered by amniotic tissue, but this membrane covering is easily ruptured. Most affected neonates die or are euthanized at birth.



Diagnosis




Physical Examination Findings


Abdominal structures (e.g., organs, omentum) in the subcutaneous space or between muscle layers usually cause asymmetry of the abdominal contour. The size of the swelling may not correspond to the size of the hernia, particularly if intestine has migrated into the hernia. The swelling should be palpated carefully to discern the contents of the hernia (e.g., intestine, bladder, spleen) and to locate the abdominal defect. These patients should be thoroughly examined to determine whether a concurrent abdominal or thoracic injury or abnormality exists. Rupture of the cranial pubic ligament often is difficult to palpate because of subcutaneous swelling and pain.


Umbilical hernias usually manifest as a soft ventral abdominal mass at the umbilical scar. Deep palpation of the swelling reveals the size of the umbilical ring and helps characterize hernial contents. The hernial ring is not palpable in some animals because the ring closes subsequent to herniation of falciform fat or omentum. Occasionally, intestine or other abdominal structures can be palpated; they generally can be reduced into the abdominal cavity. If the umbilical sac is warm or painful and the contents are irreducible, intestinal strangulation or obstruction should be suspected.



NOTE • Be sure to evaluate dogs with congenital hernia for other defects (e.g., cryptorchidism in animals with umbilical hernia, ventricular septal defects and pericardial diaphragmatic hernias in animals with cranial abdominal hernias).







Surgical Treatment


Most abdominal hernias can be repaired by suturing torn muscle edges or apposing a disrupted abdominal wall edge to the pubis, ribs, or adjacent fascia. Synthetic mesh must be used to repair the defect in rare cases. Some hernias (e.g., intestinal strangulation, urinary obstruction, concurrent organ trauma) require emergency surgical correction. However, the extent of devitalized muscle may not be apparent initially, and delaying surgery in stable patients until muscle damage can be accurately assessed facilitates surgical correction. The most common surgical complications are hernia recurrence and wound infection. Abdominal hernias secondary to bite wounds usually are contaminated; wound infection and dehiscence of the skin or hernial repair (or both) are common. Nonabsorbable mesh should not be placed in these hernias, and the wounds should be drained. Treatment of infected wounds includes cultures, drainage, antibiotics, and/or flushing. Abdominal exploration should be performed at herniorrhaphy to diagnose concurrent abdominal organ injury (e.g., mesenteric avulsion, gastric or intestinal perforation, diaphragmatic herniation, bladder rupture).


Many umbilical hernias resolve spontaneously in young animals or are small and are not corrected until the animal is neutered. Spontaneous closure may occur as late as 6 months of age. Intestinal strangulation is most likely to occur when the hernial defect is about the size of the intestine and the hernial sac is large. Strangulation is unlikely with very small or large defects. If abdominal viscera in the hernia cannot be reduced, surgery should be performed as soon as possible.




Anesthesia


If no concurrent abdominal injury or disease is identified, a variety of anesthetic protocols can be used to anesthetize the animal. See Table 19-2 for anesthetic management of animals that are in shock or are debilitated. See also subsequent chapters for detailed information about anesthetic management of patients with specific diseases (e.g., renal, pancreatic, hepatic).



Surgical Anatomy


The abdominal wall is composed of four muscle layers (the external and internal abdominal oblique muscles, the rectus abdominis muscle, and the transversus abdominis muscle). Abdominal hernias may occur at insertions or attachments of these muscles or through muscle bellies themselves. In the dog, the cranial pubic ligament (prepubic tendon) is a band of transverse fibers that serves to attach the ventral abdominal muscles to the cranial border of the pubis. In cats, no distinct prepubic tendon exists (Beittenmiller et al, 2009); rather, the abdominal muscles attach directly to the pelvic brim (Fig. 19-5).





Surgical Techniques



Abdominal Hernias


For most abdominal hernias, perform a ventral midline abdominal incision to allow the entire abdomen to be explored. Assess the extent of visceral herniation. Reduce the herniated contents and amputate or excise necrotic or devitalized tissue around the hernia. Close the muscle layers of the hernia with simple interrupted or simple continuous sutures. If a large area of devitalized tissue is removed, use synthetic mesh such as Marlex or Prolene to close the defect (do not place nonabsorbable mesh in infected sites). Fold the edges of the mesh over and suture the folded edges to viable tissue using simple interrupted sutures. Injuries to the cranial pubic ligament can be difficult to repair. If necessary, drill holes in the pubic bone to anchor the sutures.




Cranial pubic ligament (prepubic) hernias

In dogs, make a ventral midline skin incision and identify the ruptured tendon and its pubic insertion. Evaluate the inguinal rings and vascular lacuna; these hernias may extend into the femoral region as a result of rupture of the inguinal ligament. In cats, inspect the crura of the superficial inguinal ring and the aponeurosis of the external abdominal oblique muscle for damage. Reattach the free edge of the abdominal wall to the cranial pubic ligament with simple interrupted, cruciate, or mattress sutures of nonabsorbable monofilament suture (e.g., polybutester [Novafil], polypropylene [Prolene], nylon) or absorbable suture material (see later under “Suture Materials and Special Instruments”). If an inguinal or femoral hernia is present, reattach the prepubic tendon to the pubis first, before repairing the other defects.


As an alternative, suture the tendon remnant to the muscle fascia and periosteum covering the pubis, or anchor it to the pubis by drilling holes in the pubic bone through which sutures can be placed (Fig. 19-6). If the hernia extends into the femoral region, it may be necessary to suture the body wall to the medial fascia of the adductor muscles. When doing so, take care to avoid damaging the femoral vessels or nerves.



A cranial sartorius muscle flap may be used to repair prepubic tendon injuries. Separate the cranial portion of the muscle from its caudal belly and the quadriceps femoris muscle. Then transect the cranial portion of the muscle at its distal insertion on the medial aspect of the patella and elevate it to the level of the proximal vascular pedicle (Fig. 19-7). Rotate the flap 180 degrees to the defect, and secure it using simple interrupted sutures. Use the flap to repair concurrent inguinal or femoral hernia, if present.




Umbilical Hernias


For umbilical hernias, palpate the hernial ring, reduce the abdominal contents if possible, and incise the skin over the umbilicus. If the hernia contains only fat or omentum, ligate the hernial neck and excise the sac and its contents. As an alternative, if adhesions are not present, invert the sac and its contents into the abdominal cavity. Do not débride the wound margins. Suture the edges of the defect with monofilament, synthetic, absorbable suture (e.g., polydioxanone [PDS], polyglyconate [Maxon], poliglecaprone 25 [Monocryl], glycomer 631 [Biosyn]) in a simple interrupted pattern. If the hernial contents cannot be reduced, make an elliptic incision around the swelling to avoid damaging the contents. Incise the hernial sac and replace the contents in the abdominal cavity. If the contents are irreducible, or if strangulation or intestinal obstruction is present, extend the abdominal defect on the midline. Explore the abdomen and inspect the intestines for viability before closing the defect. Umbilical hernia repair seldom requires mesh implantation.



Suture Materials and Special Instruments


Strong, absorbable suture (e.g., polydioxanone [PDS], polyglyconate [Maxon], poliglecaprone 25 [Monocryl], glycomer 631 [Biosyn]) or nonabsorbable suture (e.g., polybutester [Novafil], polypropylene [Prolene], nylon) should be used to repair abdominal or ventral hernias. Nonabsorbable suture materials may be preferred over absorbable suture materials because they maintain tensile strength for longer than a year (see p. 68); however, successful repair with absorbable suture materials has been reported. Marlex and Prolene synthetic mesh may be used to repair some large defects. A study of polypropylene mesh showed a substantial reduction in the diameter of the ductus deferens associated with an intense inflammatory reaction when the mesh was placed in contact with the spermatic cord of dogs (Goldenberg and Ferreira de Paula, 2005).




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Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Surgery of the Abdominal Cavity

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