How To Repair Diaphragmatic Hernias in Dogs and Cats

 
   Introduction  
   Hernias of the diaphragm can be either congenital or acquired. Acquired hernias are most commonly due to blunt trauma to the abdomen.  Increased intra-abdominal pressure causes the diaphragm to stretch and rupture.  Liver, spleen and intestines are the organs most commonly herniated into the thoracic cavity.(1)  The muscular portion of the diaphragm, at its ventral and lateral aspects, is the most frequently torn area. Congenital hernias include the pericardial peritoneal diaphragmatic hernia (PPDH).

   Clinical Signs  
   Signs of respiratory distress, e.g., tachypnea, dyspnea, or abdominal breathing, are most common.  The animal may have a "tucked-up" appearance to the abdomen due to shifting of viscera into the pleural space.  In chronic cases, weight loss and lethargy may be the only signs the owners describe.(2) Exercise intolerance is also usually seen. In rare cases, the owner may describe signs referable to other organ systems.  For example, herniation of the intestine can cause obstruction of bowel, resulting in vomiting.  Herniation of the liver and biliary system can cause extrahepatic biliary obstruction, causing elevated serum bilirubin and icterus. 
   
   Diagnosis 
   Auscultation of the thorax reveals decreased lung sounds ventrally, and muffled heart sounds.  The thorax is dull on percussion.  Reportedly, auscultation of borborygmus in the thorax is a sign of diaphragmatic hernia, but this is not a consistent finding and should not be depended upon to make the diagnosis.
   Radiographic examination of the thorax may reveal fluid densities and/or bowel loops in the thorax. (Fig 1) Loss of continuity of the diaphragm is also seen. 

Fig. 1: Lateral thoracic radiograph of a dog with a diaphragmatic hernia and
several loops of bowel in the thoracic cavity. 

Hydrothorax may be the only radiographic sign if the liver is the only organ herniated into the thorax.  This fluid appears serosanguineous and is a transudate or modified transudate.  Ultrasonographic examination of the cranial abdomen can help confirm the hernia. 
   
   Preoperative Care  
   Diaphragmatic herniorraphy is usually considered an emergency operation. Although historically some authors advocated delaying surgical repair for several hours (3), a more recent study found that patients operated within the first 24 hours after presentation had very good outcomes (90% survival) (4). If the animal with diaphragmatic hernia does not stabilize with initial supportive care or if stomach or strangulated bowel is in the thorax the repair must be done immediately.(5) Stomach in the thorax can become dilated with air and cause life threatening hypoventilation. (Fig. 2) 

Fig. 2: Lateral thoracic radiograph of a dog with diaphragmatic hernia and stomach in the thorax cavity.
The stomach is severely dilated with air. 

If this occurs, pass a stomach tube to initially decompress the stomach If a stomach tube cannot be passed perform gastrocentesis percutaneously by placing a needle or over the needle catheter into the stomach through the chest wall.  When respiratory parameters have improved, anesthesia and surgery can then be performed.
   
   Anesthesia  
   Since these patients have markedly reduced ventilatory capacity, anesthetic induction and intubation must be rapid and smooth.  Pre-oxygenation of the patient in an oxygen cage or with an anesthetic mask is helpful to prevent hypoxia during the stress of anesthetic induction.  Rapidly acting intravenous induction agents, such as propofol, allow prompt intubation.  Begin positive pressure ventilation as soon as the endotracheal tube is placed.  Inhalant anesthetics, such as isoflurane, are acceptable for maintenance of anesthesia.
   During the clipping and prepping of the animal for surgery, the prep table can be tilted so that the head is elevated and the hindquarters lowered.  This helps prevent movement of abdominal viscera into the thorax.  
    
   Key Point: It is important to realize that when the abdominal cavity is surgically opened in an animal with diaphragmatic hernia, the animal will no longer be able to ventilate on its own. The rent in the diaphragm allows air to enter the thoracic cavity when the abdomen is open, eliminating the negative intrathoracic pressure that is necessary for normal ventilation. Intermittent positive pressure ventilation (IPPV) is therefore necessary during the surgical repair of the diaphragm. 
   
   Surgery 
   The ventral midline abdominal approach is indicated for most diaphragmatic hernias. (Fig. 3) 

Fig. 3: Intraoperative appearance of a left diaphragmatic hernia
exposed via a ventral midline abdominal approach.
(arrows indicate edges of the ruptured diaphragm).
The liver is present in the thoracic cavity.

Balfour retractors and large malleable retractors facilitate the exposure.  Grasping the edges of the diaphramatic defect with Babcock forceps or stay sutures can help in closure of the defect.  In many cases, the diaphragmatic defect must be enlarged to allow the viscera to be pulled back (reduced) into the abdomen.  When enlarging the defect, be sure to make the diaphragmatic incision in an accessible portion of the diaphragm to simplify closure. Chronic hernias may be associated with adhesions between the herniated organs and the lungs or mediastinum.(2) Break these down carefully to avoid injury to lung or other organs.  After reducing herniated organs back to the abdominal cavity carefully examine the lungs for evidence of atelectasis.  If atelectasis is found it is best not to acutely re-expand those lung lobes since re-expansion pulmonary edema can occur.  This is especially true in chronic hernias.  Place a thoracic drain tube before closure of the diaphragm to allow for re-establishment of negative pressure in the pleural space once the diaphragmic rent is repaired.  
   A variety of techniques for herniorrhaphy have been described.  The author prefers a continuous suture pattern using 2-0 or 3-0 PDS depending on patient size. Suturing is begun at the most inaccessible area of the defect (usually the dorsal aspect) progressing to the most accessible.(Fig 4) 

Fig. 4: Same dog as in figure 3 after suture closure of the diaphragmatic hernia.

Be very careful when working around the central part of the diaphragm because of the caudal vena cava.  Take care to not make the closure too tight around the caval hiatus.  Incorporation of the ribs with the soft tissues during suturing is sometimes necessary for those hernias that occur along the costal arch.
   In rare cases there is not enough diaphragmatic tissue to permit primary closure.  For example, chronic hernias in which the diaphragmatic tissue tears directly off the costal arch or dorsally from the spine.  In these cases reconstruction of the defect with a mesh implant such as Marlex mesh can be used.  The mesh is sutured in place with non-absorbable sutures such as monofilament polypropylene.  Prophylactic antibiotics are indicated in these cases.
   Once closure of the diaphragm is completed, remove residual air from the thorax.  This can be done either directly through the diaphragm using a needle or over the needle catheter or by placing a thoracostomy tube. When postoperative pneumothorax is a potential problem, such as those cases with lung adhesions, an indwelling thoracic drain tube should be placed and left in for as long as necessary to ensure stable negative intrapleural pressure. As previously mentioned in animals with chronic hernias and lung atelectasis, slowly evacuate the air in the pleural space over several hours to prevent re-expansion pulmonary edema. 
   
   Postoperative Care 
   Close observation of the patient is mandatory postoperatively.  If available the patient is kept in an oxygen cage until recovered.  In most cases recovery is unremarkable.  Acute, severe pulmonary edema can occur in some animals postoperatively and must be treated aggressively using diuretics, oxygen, and assisted ventilation.  In general the prognosis for postoperative survival is very good for patients with either acute or chronic diaphragmatic hernias. (2,4)
   
   References
1. Wilson GP, Newton CD, Burt JK. A review of 116 diaphragmatic hernias in dogs and cats. J Am Vet Med Assoc 1971; 159:1142-1145
2. Minihan AC, Berg J, Evans KL. Chronic diaphragmatic hernia in 34 dogs and 16 cats.
J Am Anim Hosp Assoc. 2004 Jan-Feb;40(1):51-63. 
3. Boudrieau RJ: Pathophysiology of Traumatic Diaphragmatic Hernia, in Bojrab MJ (ED): Disease Mechanisms in  Small Animal Surgery, ed 2. Philadelphia, Lea & Febiger, 1993, pgs 103–108
4. Gibson TW1, Brisson BA, Sears W. Perioperative survival rates after surgery for diaphragmatic hernia in dogs and cats: 92 cases (1990-2002).J Am Vet Med Assoc. 2005 Jul 1;227(1):105-9.
5.Bjorling DE. Thoracic Trauma, in Birchard SJ, Sherding RG, ed. Saunders Manual of Small Animal Practice. St. Louis, Elsevier, 2006, pgs. 1721-1722.

Do Lawn Treatment Chemicals Cause Cancer in Pets? A growing body of research says yes!

Cancer is one of the most important health issues affecting household pets. Causes of cancer are many and varied, including genetic predispositions, certain viruses, and exposure to environmental toxins. Many studies in both humans and animals have focused on the increased risk of cancer from chronic use of chemicals such as pesticides and herbicides around the household.  Since dogs and cats have significant exposure to grassy areas of properties, lawn chemicals in particular have been studied for the potential of causing health problems.

Several studies have now shown an association between the frequently used chemicals on household lawns and cancer in dogs.(1-4) Dogs chronically exposed to the herbicides and pesticides in lawn sprays and granules are more likely to get cancers such as lymphoma and transitional cell carcinoma of the urinary bladder. An initial study published in the Journal of the National Cancer Institute in 1991 found that homeowners that frequently used the herbicide 2,4- dichlorophenoxyacetic acid on their lawn had a statistically significant higher rate of lymphosarcoma in their dogs.(1) Lymphosarcoma, also called malignant lymphoma, is a common cancer affecting lymph nodes and other organs and lymphatic tissues. This study was heavily criticized by other investigators who questioned the validity of the results. However, a more recent study published in 2012 analyzed 263 dogs with lymphosarcoma and found a 70% increase in risk of the cancer in households with professionally applied pesticides on the lawns.(2)

Two studies at Purdue University College of Veterinary Medicine have also found disturbing results of dogs exposed to herbicides, particularly the phenoxy herbicides such as the previously mentioned 2,4- dichlorophenoxyacetic acid, also called 2,4-D.(3,4) 

Herbicides were found in the urine of 76% of dogs from households that used them on their lawn.(4) The herbicides were also found in the urine of some dogs from households where the herbicide was not used, indicating they were exposed to them in areas other than their own property. 

The additional study from Purdue found that Scottish Terriers living in households that used herbicides alone or herbicides and pesticides on their lawns were markedly more prone to transitional cell carcinoma of the urinary bladder.(3) This study, along with the former one looking at the chemicals being present in the urine, are convincing evidence that the herbicide exposure is directly related to bladder cancer in this breed. Other breeds could be examined in the future to further define the risks of exposure. 

More research is needed to elaborate the dangers of lawn chemicals to our pets, but these well designed and executed studies make it clear that the commonly used pesticides and herbicides being indiscriminately sprayed and broadcast on our lawns are causing cancer in dogs. Many provinces in Canada have completely banned what they call “cosmetic” use of herbicides and pesticides because of the potential health problems. Cosmetic is a good term because the cancer causing chemicals are being used merely to improve the appearance of our lawns. Maybe we should be more tolerant of less than perfect grass if it decreases the adverse health effects on our pets. 

Although additional studies will help to better define the problem, we now have sufficient evidence to raise serious concerns about the dangers of herbicides and pesticides used on lawns. Homeowners should be educated about these issues so that they can take appropriate action to protect their pets from harm. Professional lawn care companies also need to carefully consider their protocols and make necessary changes to stop contaminating the environment with chemicals that are now proven to be carcinogenic to pets. 

References

1. Hayes HM1, Tarone RE, Cantor KP, Jessen CR, McCurnin DM, Richardson RC. Case-control study of canine malignant lymphoma: positive association with dog owner's use of 2,4- dichlorophenoxyacetic acid herbicides. J Natl Cancer Inst. 1991 Sep 4;83(17):1226-31. 

2. Biki B. Takashima-Uebelhoer, Lisa G. Barber, Sofija E. Zagarins, Elizabeth Procter- 
Gray, Audra L. Gollenberg, Antony S. Moore, and Elizabeth R. Bertone-Johnson. Household Chemical Exposures and the Risk of Canine Malignant Lymphoma, a Model for Human Non-Hodgkin’s Lymphoma. Environ Res. 2012 January ; 112: 171–176. 

3. Glickman LT1, Raghavan M, Knapp DW, Bonney PL, Dawson MHJ. Herbicide exposure and the risk of transitional cell carcinoma of the urinary bladder in Scottish Terriers. J Am Vet Med Assoc. 2004 Apr 15;224(8):1290-7. 

4. Knapp DW1, Peer WA, Conteh A, Diggs AR, Cooper BR, Glickman NW, Bonney PL, Stewart JC, Glickman LT, Murphy AS. Detection of herbicides in the urine of pet dogs following home lawn chemical application. Sci Total Environ. 2013 Jul 1;456-457:34-41. 

Axial Pattern Flap Reconstruction of a Chronic Non-Healing Elbow Wound in a Golden Retriever

Ginger is a 7-year-old female spayed golden retriever who presented to MedVet Toledo with a chronic non-healing open skin wound over the right elbow. (Fig. 1) 

Fig. 1: Ginger

The owner adopted Ginger 1.5 years prior to presentation and the wound was present at that time. Ginger was otherwise healthy with no major medical issues. Serous fluid drained from the wound occasionally. Antibiotic therapy previously prescribed did not result in significant improvement of the wound.

Physical examination of Ginger was normal except for a large (8cm diameter) open wound over the right elbow that appeared to be a decubital ulcer. (Fig. 2) 

Fig. 2: The non-healing chronic open wound over the right elbow on Ginger

Extensive fibrotic scar tissue was present around the periphery of the circular wound, and unhealthy granulation tissue was seen in the wound center. Little to no discharge was present on the wound surface.

A fine needle aspirate of the peripheral scar tissue was performed to rule out neoplasia and the cytology results indicated chronic inflammation. Routine preoperative CBC and serum chemistry profile were normal. The plan was to anesthetize Ginger, perform an extensive surgical debridement of the fibrotic peripheral tissues, and reconstruct the skin using an axial pattern skin flap. 

Ginger was anesthetized and the right elbow and surrounding skin clipped and prepared for aseptic surgery. The donut shaped abnormal scar tissue was removed using blunt and sharp dissection. (Fig. 3) 

Fig. 3: The right elbow of Ginger immediately after surgical debridement of the chronic wound. 

During this dissection it became clear that the tissue was highly vascularized. Hemostasis was difficult and bleeding became brisk throughout the dissected area. The hemorrhage was controlled with electrocautery and direct pressure. We elected to delay the skin flap reconstruction so that open wound management with tie-over bandages could be used on the elbow to allow the debrided area to be in more optimal condition for the definitive reconstruction procedure. (for more information see: tie-over bandages)

One week after the surgical debridement Ginger was re-admitted to the hospital for the skin flap procedure. Ginger was placed under general anesthesia and a thoracodorsal axial pattern skin flap was performed to reconstruct the elbow decubitalulcer. (Fig. 4)
(for more information see: axial pattern skin flaps) 

Fig. 4: Completed thoracodorsal axial pattern flap reconstruction of the elbow on Ginger.
White arrow indicates direction of transfer of the rectangular skin flap harvested from skin over the scapula.

Complete coverage of the wound was achieved with the skin flap. A spica bandage was placed over the leg and thorax to protect the incisions and Ginger was recovered from anesthesia. 

The following day Ginger’s bandage was changed and she was discharged from the hospital. Bandage changes occurred every 2-3 days until the incisions were healed and staples removed. (Fig. 5) 

Fig. 5: Appearance of the surgical incisions on Ginger 10 days postoperatively.

Ginger finally was discharged with no rechecks necessary unless problems arose. However 5 months later she represented to MedVet Toledo for problems unrelated to her elbow. The owner reported that since the skin flap reconstruction Ginger had been much more comfortable and mobile. Ginger’s skin flap had grown a thick, bushy amount of hair. There was redundant skin at the elbow but the overall cosmetic appearance was quite satisfactory. (Fig. 6) In general the owner was very pleased with the end result of the reconstruction.

Fig. 6: Appearance of Ginger's right elbow area 5 months after reconstruction.

Chronic wounds of the elbow in dogs are one of the most difficult to manage. Skin tension, excessive motion, and trauma to the area combine to interfere with healing in this part of the body. Debridement and local advancement of skin over the defect is generally unrewarding for reconstruction, particularly if it results in a suture line directly over the olecranon. Skin flap techniques that bring healthy, robust tissue into the site without creating a suture line over the olecranon, such as an axial pattern flap, is more likely to be successful.

Several aspects of the postoperative care are key to the success of this procedure. A well-padded bandage to protect and cushion the skin flap is mandatory for at least 10-14 days postoperatively. Exercise restriction is also important along with frequent postoperative rechecks to monitor for flap survival and healing. 

One clinical study of 10 dogs having thoracodorsal axial pattern flaps found complications to be common but good functional and cosmetic outcome resulted in 6 of 7 dogs long term follow up. (1)

References

1. Aper R, Smeak, D:  Complications and Outcome After Thoracodorsal Axial Pattern Flap Reconstruction of Forelimb Skin Defects in 10 Dogs, 1989–2001 32:4, 2003, Pages 378-384.