CHAPTER 27. Soft Tissue Surgery
S. Brent Reimer
GENERAL INFORMATION
I. Wound classification
Wounds are classified based on the degree of contamination. As the degree of contamination increases, the postoperative infection rate can generally be expected to increase as well. The “critical” level of bacterial contamination that begets infection is classically greater than 10 5 organisms per gram of tissue, but variables other than population play a role (i.e., the virulence of the organism, blood supply of tissue involved, host defense mechanisms). Surgeries are classified as one of the following four types:
A. Clean: A surgically created wound (nontraumatic) not involving the respiratory, gastrointestinal (GI), or genitourinary tract. No breaches in the tenets of aseptic technique
B. Clean-contaminated: Controlled entrance into the respiratory, GI, or genitourinary tract, avoiding spillage of contents into the surgical field or with a minor breach in aseptic technique
C. Contaminated: Surgical field subjected to gross spillage of infected tissues or contents of respiratory, GI, or genitourinary tract. Also seen with a major breach in aseptic technique and in “fresh” (less than 4 to 6 hours) traumatic wounds
D. Dirty: Traumatic wound with devitalized tissues or delayed treatment (longer than 4 to 6 hours), transaction of “clean” tissues encountered during surgery to gain access to abscessed tissues
II. Antimicrobial prophylaxis
Antimicrobial prophylaxis is defined as the administration of an antimicrobial agent before the contamination event, typically the surgical incision. Therefore, these agents should be given preoperatively 30 and 60 minutes before creation of the incision. However, the continuation of antibiotic prophylaxis into the postoperative period is indicated in some very specific circumstances. Decisions regarding which antimicrobial to administer should be directed by anticipated pathogens present and their susceptibility profile. Currently, no evidence has been found that substantiates the routine continuation of antimicrobial administration postoperatively.
III. Patient preparation
A. Hair removal: Clipping is preferred over shaving because it incurs less skin trauma. The clipping should be performed immediately before surgery and should take place in an area independent of the operating room
B. Skin preparation: Antiseptic agents are used to reduce the bacterial colonization of the surgical field before surgery. The preferred agents are bactericidal. Commonly used agents include chlorhexidine or povidone-iodophor compounds intermittently rinsed with either sterile saline or isopropyl alcohol. Chlorhexidine may cause a decreased number of skin reactions compared with povidone-iodophor compounds. One report states that the use of chlorhexidine scrubs with isopropyl alcohol rinses is inferior to chlorhexidine scrubs with sterile saline rinses
SUTURE INFORMATION
I. Suture materials
A. Suture is classified as absorbable or nonabsorbable. Most absorbable suture materials lose much of their tensile strength within 60 days of implantation. Most absorbable sutures undergo tissue hydrolysis, but some are absorbed via phagocytosis (e.g., chromic surgical gut)
1. Nonabsorbable suture materials include silk, nylon, and polypropylene
2. Absorbable suture materials include polydioxanone, polyglactin 910, chromic surgical gut, polyglycolic acid, poliglecaprone 25, and polyglyconate
B. Suture is further classified as either monofilament or multifilament (“braided”). Multifilament suture materials inherently possess more capillarity, thus allow more bacteria to “wick” into areas in which they are used. Monofilaments possess less of this capillary action and thus are a better choice for contaminated wounds. Multifilament suture materials typically have less memory and often possess better handling characteristics compared with monofilament materials
1. Monofilament sutures include polydioxanone, poliglecaprone 25, polypropylene, polyglyconate, and nylon
2. Multifilament sutures include silk, polyglactin 910, polyglycolic acid, and chromic surgical gut
C. Suture can further be classified as synthetic or natural (organic)
1. Natural suture materials include surgical gut and silk
D. Suture selection should be individually tailored to the tissue and expected wound environment. In general, the suture should be as strong as, but should not greatly exceed, the tensile strength of the involved healing tissue. For wounds in which bacteria are anticipated to be present (GI surgery, contaminated wounds), typically a monofilament absorbable suture is recommended (e.g., polydioxanone)
E. Suture patterns include inverting, everting, and appositional patterns. Appositional and inverting patterns are most commonly used
1. Inverting suture patterns include the Lembert, Halsted, Cushing, Connell, Parker-Kerr, and pursestring
2. Appositional suture patterns include the simple interrupted, simple continuous, cruciate, and Gambee
BODY CAVITIES AND HERNIAS
I. Abdominal cavity
A. Most commonly approached through a ventral midline incision through the linea alba via a midline celiotomy
B. The holding layer of the abdomen is the external rectus fascia. It is imperative that this layer be included in abdominal closures to prevent dehiscence
II. Hernias
A. Umbilical hernia
1. Congenital defect believed to be heritable in some breeds
2. Often asymptomatic but could have visceral entrapment
3. Herniorrhaphy is the surgical closure of the hernia
4. Prognosis is good and recurrences are uncommon
B. Cranial pubic ligament hernia
1. Traumatic avulsion of the cranial pubic ligament from the pubic bone
2. Commonly allows caudal abdominal viscera to escape the abdominal cavity and reside in the subcutaneous tissues
3. Diagnosis: Suspicion in a patient with abnormal swelling near pelvic inlet after a traumatic event. Bruising of the skin overlying the swelling is also a suspicious finding. Radiographs may reveal a loss of the “stripe” of the ventral abdominal wall on a lateral film as it courses toward its typical insertional point on the cranial edge of the pubis. Viscera may also be readily apparent on radiographs. Abdominal ultrasound may also be useful
4. Treatment: Herniorrhaphy. The avulsed ligament often has to be secured to holes predrilled into the pubic bone to gain purchase.
5. Prognosis is favorable for patients without significant concurrent injuries
C. Inguinal hernia
1. Traumatic: Can occur in any dog or cat
2. Nontraumatic: Most typically associated with intact, middle-aged female dogs or young male dogs. Presumably associated with a delayed closure of the inguinal ring to allow the testicles to descend
D. Scrotal hernia is most common in chondrodystrophic dogs
E. Femoral hernia
1. Male or female dogs are affected
2. Can present with a nonpainful swelling over the mid-thigh or can have vomiting or pain with entrapment
F. Perineal hernia
1. More common in dogs than cats
2. Much more common in intact males, link to androgens
3. Failure of the muscles of the pelvic diaphragm allows abdominal organs to escape. Omentum most commonly entrapped and dogs present with tenesmus, dyschezia, diarrhea, and a fluctuant nonpainful swelling in the perineal region. Can be unilateral or bilateral. Can become an emergency if bladder becomes entrapped
4. Diagnosis: Typically a clinical diagnosis; rectal examination is useful in the diagnosis of this disease
5. Herniorrhaphy, most commonly using an internal obturator roll-up technique. Concurrent castration is also highly recommended.
6. Prognosis: Generally fair to good, but recurrence is relatively common
G. Diaphragmatic hernia
1. Can be traumatic (acquired) or congenital
2. The most common congenital diaphragmatic hernia is called a peritoneopericardial diaphragmatic hernia
a. Can occur in cats and dogs
b. Can be asymptomatic or cause problems related to the cardiovascular, respiratory, or GI tracts
c. Direct communication between the abdomen and the pericardial sac
d. May be accompanied by concurrent sternal defects or, in dogs, cranial abdominal wall hernias. Domestic long-haired cats and Weimaraner and cocker spaniel dogs appear to be predisposed
e. Radiographic signs: Enlarged cardiac silhouette, tracheal elevation, loss of diaphragmatic border, gas-filled structures within the pericardial sac
f. Treatment: Surgical herniorrhaphy if clinically affected. Surgical approach is via a ventral midline celiotomy, which can be extended into a caudal sternotomy if necessary
g. Prognosis is favorable
3. Traumatic diaphragmatic hernias are more common than congenital diaphragmatic hernias in small animals
a. Motor vehicle accidents are the most common cause but can result from many events that cause intraabdominal pressure to elevate quickly. This causes the lungs to deflate quickly, which creates a significant pressure differential between the abdominal and pleural compartments. This causes the diaphragm to be under significant stress, and ruptures can occur
b. Patients with diaphragmatic hernias are often in shock as a result of the traumatic event. Concurrent injuries are common and should be looked for; may present with dyspnea, tachypnea, cyanosis, or tachycardia
c. Physical examination may reveal dull heart and lung sounds, intrathoracic borborygmi as a result of GI organs being present in the thoracic cavity, minimal ability to generate meaningful chest excursions, significant abdominal component to respiration, and potentially an abdomen that appears “deflated,” which is due to the abdominal contents now residing in the thoracic cavity
d. Initial patient stabilization is often necessary. This is accomplished by providing oxygen supplementation, potentially elevating the cranial end of the patient in an effort to encourage thoracic contents to “leak” back into the abdomen. Pleural effusion is commonly present and can be removed via thoracocentesis in an effort to improve breathing
e. Diagnosis is obtained via plain radiographs most commonly. A loss of the diaphragmatic line may be appreciated; a loss of the cardiac silhouette, displacement of the lungs by soft tissue or fluid opacity structure, or presence of gas-filled GI organs can also be seen on occasion. If a definitive diagnosis is not yet obtained, a water-soluble positive contrast agent can be injected into the peritoneal cavity in a procedure called a positive contrast celiogram. An abnormal communication between the abdominal and thoracic cavities would allow contrast agent to enter the thoracic cavity. An upper GI study using barium administered per os may also reveal loops of intestine within the thoracic cavity. Ultrasound may also be useful in obtaining the diagnosis if necessary
f. Treatment: Mechanical ventilation is necessary during this procedure. Patient should be stabilized before being taken to surgery to correct. Patients with gastric entrapment may be at an increased risk for acute respiratory decompensation resulting from progressive gastric distension. These patients should be monitored closely and potentially taken to surgery on an emergency basis. Surgical correction is achieved via ventral midline celiotomy. Rarely, this incision needs to be extended into a caudal sternotomy. The rent is identified, and gentle traction is placed on the herniated organs to place them back into the abdomen. The liver is the organ most commonly herniated through the diaphragm. Occasionally, the rent needs to be enlarged to allow the herniated organs to be replaced into the abdomen. The rent is then sutured, typically in a simple continuous pattern. A thoracostomy tube is placed to facilitate reestablishment of negative intrapleural pressure
g. Prognosis: Typically good in patients that can be stabilized. Recurrence is uncommon
SURGERY OF THE INTEGUMENT
I. Wounds
A. Healing of the integument is influenced by the wound environment as well as host factors. The healing of wounds occurs in the following overlapping phases:
1. Inflammatory phase. Occurs immediately after the wound has been created
2. Debridement phase. Host cells remove damaged or necrotic tissue
3. Repair phase. Generally begins several days after the injury
B. Most surgical wounds are weakest during the “lag phase” of wound healing, which occurs 3 to 5 days after surgery. Most surgical dehiscences occur during this time
C. Host factors that slow wound healing include excessive glucocorticoid levels (either endogenous or exogenous), diabetes mellitus, malnourishment, and hypoalbuminemia
D. Wounds can heal via several different mechanisms:
1. Primary closure. Surgical closure of viable tissue without delay
2. Delayed primary closure. Typically contaminated wounds. Wound cleaned and lavaged for 2 to 5 days after surgery until contamination is under control, and then wound closure is performed
3. Secondary closure. Wound maintained as an open wound and closed subsequent to granulation tissue formation (more than 5 days after creation of the wound)
4. Second-intention healing. Wound allowed to heal via granulation, wound contraction, and epithelialization without surgical manipulation
II. Specific diseases of the integument
A. Neoplasia
1. Mast cell tumors: Most common cutaneous malignancy of dogs. All are considered malignant in dogs. Exist as grade 1, 2, or 3, with the higher the grade indicating a more anaplastic and biologically aggressive tumor. Typically occur in the skin but can also occur in the bone marrow or internal organs (liver, spleen, GI tract). In cats, cutaneous mast cell tumors are typically benign and have a predisposition for the head and neck. Visceral involvement in cats indicates malignancy
a. Signalment: Predisposition in certain breeds (boxers, pugs, and Boston terriers). Generally middle-aged or older animals
b. Diagnosis: Described as the “great imitator” because of its tendency to have no typical or highly predictable appearance. Should be considered a differential diagnosis for any cutaneous or subcutaneous mass. Mass can increase and decrease in size as a result of degranulation of intracellular histamine granules. Typically exfoliates cells readily on fine-needle aspirate (FNA) to obtain diagnosis. Cytology reveals a round cell population with granules commonly seen. Grade can only be obtained via histopathological appearance via biopsy
c. Treatment: Wide surgical excision is the treatment of choice. Classically, 3-cm margins have been recommended. This recommendation was based primarily on empirical thought rather than scientific evidence. Recent reports may support less aggressive surgical margins as being as effective. Classically chemotherapeutic interventions centered on prednisone or vinblastine have been used. May also need a histamine 2 (H 2) blocker if the increased levels of H 2 in the blood are causing GI ulceration. May respond to radiation therapy
d. Prognosis: Good with successful removal of masses with clean margins. Guarded to poor with grade 3 tumors or tumors which have already metastasized (regional lymph nodes most commonly)
2. Mammary masses: Uncommon in male dogs and male cats but can occur. Most common tumor in female dogs. Cause is unknown but linked to hormonal influences, so decreased incidence in dogs spayed early in life. Approximately 50% are malignant in dogs, between 80 and 90% are malignant in cats
a. Signalment: Typically intact females or females spayed late in life
b. Diagnosis: Often a palpable mass in the mammary chain. Normal dogs have five mammary glands on each side; cats normally have four glands on each side. FNA may be diagnostic
c. Treatment: Surgical excision of the disease. In dogs, typically a lumpectomy or mammectomy is performed for smaller masses. In cats, more aggressive surgery is indicated and typically takes the form of bilateral radical mastectomy
d. Prognosis: Depends on histologic type, stage of disease, and ability to resect diseased tissue
SURGICAL DISEASES OF THE GI TRACT
I. Oral cavity
A. The oral cavity is inherently contaminated with bacteria but also has a robust blood supply. Consequently, healing typically occurs despite the contaminated environment
B. Surgery within the oral cavity has an increased risk of wound dehiscence as a result of the inherent contamination, increased tension often encountered, as well as the constant use of the oral cavity for daily activities (e.g., eating, swallowing saliva)
C. Neoplasia of the oral cavity
1. Malignant melanoma: Most common oral tumor of dogs. Aggressive locally and is often metastatic. Treatment centers on removing the local disease and on appropriate staging. Long-term prognosis is poor
2. Squamous cell carcinoma: Most common oral tumor of cats; occur with frequency in dogs. Locally invasive and can metastasize. Treatment centered on removal of the local disease and staging. Can be tonsillar in dogs. Prognosis is guarded in dogs and grave in cats
3. Fibrosarcoma: Locally aggressive but late to metastasize. Treatment primarily involves wide excision of the primary tumor
4. Osteosarcoma: Locally aggressive and high metastatic potential. Prognosis in dogs is poor but typically better than appendicular osteosarcoma
5. Epulides: Most common class of benign oral tumors. Three types: Acanthomatous (most common), fibromatous, and ossifying exist. Arise from the periodontal ligament. Treat with excision or radiation therapy
6. Ameloblastoma: Benign; arise from dental lamina. Young dogs
7. Oral papillomatosis: Benign process, typically younger dogs. Viral cause. Usually multiple gray masses on gingival or buccal mucosa. Typically requires no surgical intervention and spontaneously regresses
D. Cleft palate: Brachycephalic dogs and Siamese cats are predisposed. Often diagnosed at birth but may manifest because of difficulty nursing, milk coming from nostril during nursing, pneumonia (aspiration), small stature, or a failure to thrive
1. Primary cleft: Lip and premaxilla (harelip)
2. Secondary cleft: Cleft in the hard and soft palate
3. Treatment: Surgical correction of the defect using local tissue flaps most commonly. Prognosis is fair, but multiple surgeries should be anticipated to revise defect
E. Salivary mucocele: Also called a sialocele, or salivary cyst. Dogs have four paired sets of salivary glands, including the zygomatic, parotid, mandibular, and sublingual. The mandibular salivary gland duct courses from the gland rostrally and is continuous with the sublingual chain. These glands eventually empty at the rostral aspect of the lingual frenulum. These are the glands most commonly affected by a salivary mucocele. Four individual presentations can occur:
1. Nonpainful ventral cervical swelling
2. Pharyngeal swelling, which can lead to profound dyspnea
3. Rannula, submucosal swelling under the tongue
4. Exophthalmia, which is due to retrobulbar leakage of the zygomatic gland
6. Treatment: Excise the affected gland(s). Prognosis is excellent with surgery. Repeated drainage of the mucocele is very rarely effective in resolving the disease
F. Salivary gland neoplasia: Rare disease. Typically malignancy. Treatment via surgical excision
II. Esophagus
A. Animals afflicted with esophageal disease can exhibit ptyalism, regurgitation, coughing (particularly with secondary aspiration pneumonia), dysphagia, weight loss, or may be recumbent if severely debilitated
B. The esophagus does not heal as readily as many of the other areas of the GI tract because of its decreased vascularity that results from its segmental blood supply as well as the fact that the esophagus lacks a serosal layer, is in constant motion with day-to-day activities such as breathing and swallowing, and does not typically have access to the omentum to accentuate the healing process
C. Esophageal foreign bodies: Typically younger animals. Bones, rawhides, toys, fishhooks. Most commonly lodge at the thoracic inlet, base of the heart, or near the diaphragm
1. Diagnosis: Radiographs, contrast studies, esophagoscopy
2. Treatment: Preferable to remove the foreign body endoscopically; if that is not possible, then removal by surgical intervention
3. Prognosis: Good if esophagus is healthy; if damaged, esophageal stricture can result
D. Esophageal strictures: Can be intraluminal or extraluminal compressions. Can be the result of many insults, including previous esophageal surgery, esophagitis, or neoplasia. Has also been linked to administration of certain medications (e.g., doxycycline capsules in cats) because of the caustic medications maintaining mucosal contact for an extended period
1. Diagnosis: Radiographs, contrast studies, esophagoscopy
2. Treatment: Esophageal resection and anastomosis, bougienage
3. Prognosis: Guarded because recurrence is common
E. Esophageal neoplasia: Rare in cats and dogs. Typically progressed at time of diagnosis. Has been linked with Spirocerca lupi infestation
F. Vascular ring anomalies: Result from persistence of embryologic structures that normally regress in utero. Patients affected most commonly present for regurgitation, which typically begins shortly after weaning to solid foods, which cannot pass the constriction. Irish setters and German shepherd dogs are breeds that are predisposed. Multiple littermates may be affected. May remain of small stature and grow more slowly than unaffected littermates. Ventral cervical swelling can be observed near the thoracic inlet corresponding to dilated esophagus. May be coughing if have concurrent aspiration pneumonia. There are several different vascular ring anomalies, but the persistent right aortic arch is the most common and accounts for more than 90% of the vascular ring anomalies
1. Diagnosis: Radiographs typically show a dilation of the esophagus cranial to the base of the heart. Also want to rule out concurrent aspiration pneumonia. Contrast studies may also be useful. Echocardiography may be useful in determining the abnormal vessel(s) involved
2. Treatment: Surgical transection of the constricting vessel. For a persistent right aortic arch, this is accomplished through a left lateral thoracotomy performed at the fourth intercostal space
3. Prognosis: Typically good; esophageal motility problems can persist
G. Cricopharyngeal achalasia: Disorder of swallowing where food bolus that has formed in the mouth is not allowed to enter the esophagus because of failure of the cricopharyngeal muscle to relax during swallowing. Springer and cocker spaniels are predisposed. Typically diagnosed at weaning
1. Diagnosis: Clinical signs, dynamic contrast studies of the patient swallowing
2. Treatment: Cricopharyngeal myectomy
3. Prognosis: Guarded to fair
H. Hiatal hernia: Protrusion of the abdominal portion of the esophagus as well as potentially portions of the stomach through the esophageal hiatus in the diaphragm into the caudal portion of the thorax. Shar-peis and brachycephalic breeds are predisposed
1. Diagnosis: Radiographs, but the condition can be dynamic and so can have normal radiographs and a hiatal hernia still be present
2. Treatment: Medical management with H 2 blockers, gastroprotectants. If no positive response to medical management, surgical correction via gastropexy and hiatal reduction is needed
3. Prognosis: Typically good.
III. Stomach
A. Gastric dilatation-volvulus (GDV) syndrome: An extremely serious medical condition that results from the stomach rotating to varying degrees on its own axis. Gas subsequently becomes trapped within the gastric lumen and cannot escape. The stomach dilates, which subsequently compresses the systemic and portal venous systems within the abdomen. This significantly decreases cardiac return, and the patients become cardiovascularly unstable because of their functional hypovolemia. This condition represents a surgical emergency! (Figure 27-1)
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