Abstract
The records of 31 cats and eight dogs undergoing surgical correction of peritoneopericardial diaphragmatic hernia (PPDH) from 2000 through 2007 were reviewed. Weimaraners and long-haired cats of varying breeds, particularly Maine Coon cats, appear to be at higher risk of PPDH. Presenting complaints were most commonly related to the respiratory and gastrointestinal tracts in both dogs and cats, although respiratory signs were more prevalent in cats, and gastrointestinal signs were more common in dogs. The most common herniated organs were liver, gallbladder, and small intestine. Mortality associated with surgical repair of PPDH in cats and dogs was low in the first 2 weeks postoperatively, and prognosis for return to normal function was excellent. Peri-and postoperative complications were typically minor and self-limiting.
Introduction
Peritoneopericardial diaphragmatic hernia (PPDH) is an opening or communication between the pericardial sac and the pleuroperitoneal membrane. Organs that are normally located within the peritoneal cavity may be displaced into the pericardial sac. In cats and dogs, PPDH is solely the result of congenital anomalies.1,2 In humans, however, PPDH can occur as a result of either trauma or a congenital anomaly.2,3 In normal cats and dogs, the pericardium and diaphragm are not connected; therefore, PPDH as a result of trauma is unlikely.
Peritoneopericardial diaphragmatic hernia is the most common congenital cardiac defect diagnosed in cats 2 years of age and older.4 The condition is attributed to abnormal embryogenesis of the ventral portion of the diaphragm. Several theories of faulty embryogenesis leading to PPDH have already been described in detail.5–8
In previous published reports of PPDH in the veterinary literature, information regarding outcome is often incomplete, and postoperative mortality rates are not typically reported.2,5,6,8–14 Postoperative mortality rate has only been reported in one study in cats undergoing surgery for correction of PPDH; this rate was 14%.15 The purpose of this study was to evaluate morbidity and mortality associated with PPDH in the perioperative period in cats and dogs. The perioperative period was defined as the time from diagnosis to 2 weeks postoperatively. We hypothesized that following surgical repair, mortality was very low, perioperative complications were minor, and outcome was excellent.
Materials and Methods
Medical records of cats and dogs undergoing surgical repair for PPDH at Veterinary Surgical Associates from January 2000 through December 2007 were reviewed. Cats and dogs were included in the study if a diagnosis of PPDH was made based on the results of thoracic radiography with or without ultrasonography, and diagnosis was confirmed by surgical exploration. All animals undergoing surgical correction of PPDH from 2000 through 2007 were included in the study. Data obtained from the records included age, breed, sex, medical history, physical examination findings, results of laboratory tests and diagnostic imaging studies, surgical findings, perioperative complications (i.e., those that occurred preoperatively, intraoperatively, and in the immediate postoperative period prior to discharge from the hospital), postoperative complications (i.e., those occurring within 2 weeks of surgical correction of the PPDH), and the postoperative mortality rate (i.e., deaths occurring within the first 2 weeks postoperatively). Complications were classified as minor if they resolved without veterinary intervention. Conversely, major complications were those requiring surgical or medical intervention at the time they were detected.
Results
During the 8-year study period, 5270 cats were presented to Veterinary Surgical Associates for evaluation. Breeds consisted of Maine coon (n=116), Himalayan (n=90), domestic longhair (n=716), Persian (n=91), domestic shorthair (n=3147), and Siamese or Siamese-cross (n=248). Of the 5270 cats presented to the hospital during the study period, 3685 were of a breed with short hair, 1459 were of a breed with long or medium hair, and 40 were of breeds that could have long or short hair. Eighty-six cats had no breed reference recorded in the record. Thirty-nine animals—31 cats and eight dogs—had surgically confirmed PPDH. The prevalence of PPDH in cats in the hospital population was 0.59% (31 of 5270). The median age of cats diagnosed with PPDH was 48 months (range 2 to 138 months). Fifteen of 17 male cats were castrated, and all 14 female cats were spayed. Affected breeds included domestic longhair (n=16), domestic shorthair (n=5), Maine coon (n=4), Himalayan (n=2), Siamese (n=2), domestic medium hair (n=1), and Persian (n=1). Of the 31 cats with PPDH, 24 were of a breed with long or medium hair. Several long-haired breeds of cats appeared to be overrepresented compared to our hospital population during the 8-year study period. The prevalence of Maine coons with PPDH was 12.9% (4/31); however, Maine coons made up only 2.2% (116/5270) of the feline hospital population. The prevalence of cats within our hospital population having a diagnosis of PPDH was 2.2% (2/90) for Himalayans, 2.23% (16/716) for domestic long-haired cats, and 1.1% (1/91) for Persians. Domestic short-haired cats appeared to be underrepresented, as prevalence of PPDH in them was only 0.16% (5/3147) compared to the proportion of the hospital population.
The median age of dogs diagnosed with PPDH was 30 months (range 20 to 66 months). Breeds included Weimaraner (n=5), Saluki, Labrador retriever, and Tibetan terrier (n=1 each). Three of the four female dogs were spayed, and all four male dogs were castrated. Because of the small number of dogs diagnosed with PPDH during the study period, the exact prevalence of PPDH in dogs was not calculated. No sex predilection was seen for either cats or dogs diagnosed with PPDH.
Clinical signs in cats at presentation included either those related to the respiratory or gastrointestinal system or those that were nonspecific or unrelated to the diagnosis. Respiratory signs in cats included labored breathing or dyspnea (n=6), tachypnea or slightly increased respiratory effort (n=6), coughing (n=2), wheezing, cyanosis, and respiratory distress with collapse (n=1 each). Gastrointestinal signs in cats included acute vomiting (n=3); chronic, intermittent vomiting (n=3); and ptyalism (n=1). Nonspecific signs included decreased appetite and anorexia (n=7), lethargy (n=4), weight loss (n=4), weakness (n=1), and hiding (n=1). One cat had pollakiuria as the only presenting sign, and three cats had no clinical signs at the time of presentation. Clinical signs in dogs presenting with PPDH included acute vomiting (n=4), intermittent labored respirations (n=2), exercise intolerance, collapse, fever, and diarrhea (n=1 each). The diagnosis of PPDH was incidental while examining the animals for other reasons.
On physical examination, the most common finding in dogs (4/8) and cats (17/31) was muffled heart sounds. Other common physical examination findings in cats included tachypnea (n=12), thin body condition (n=7), an empty abdomen on palpation (n=7), decreased lung sounds on auscultation (n=6), and dehydration (n=4). Less common physical examination findings in cats included a heart murmur (n=2), thoracic borborygmi (n=2), a depressed or quiet mentation (n=2), a painful abdomen or “full” cranial abdomen (n=1), and a pericardial friction rub on auscultation (n=1). One cat had no abnormalities detected on physical examination. Other physical examination findings in dogs included thoracic borborygmi (n=3), decreased lung sounds, tachypnea, an empty abdomen on palpation, pyrexia, a depressed mentation, and increased body condition (n=1 each). No abnormalities were detected during physical examination of two dogs that also had no clinical signs at the time of presentation.
Thoracic radiography was performed on all 31 cats and all eight dogs. Survey radiographs revealed changes consistent with PPDH in all cases, including an enlarged cardiac silhouette and concurrent diaphragmatic discontinuity.9,10 A concurrent sternal defect was noted in one cat. Thoracic ultrasonography was performed in 11 cats and two dogs. In all 39 cases, radiographic and ultrasonographic findings were supportive of a diagnosis of PPDH.10,11 Results of an ultrasonographic assessment of cardiac function were available to us for two of the 11 cats but neither of the two dogs that underwent thoracic ultrasonography. One cat had a normal echocardiogram aside from mild mitral regurgitation, and the other had decreased diastolic filling noted.
In addition, one cat and one dog had an upper gastrointestinal barium series performed. In the dog, the study revealed loops of barium-filled intestines within the pericardial sac. In the cat, the barium-filled gastrointestinal tract was located within the abdomen. Ultrasound confirmed that the liver was the only organ herniated into the pericardial sac, which was further confirmed at surgery.
Radiographs and barium studies were performed by the referring veterinarian in all cases, and these studies were not repeated at our hospital. Ultrasonography was performed by referring veterinarians, by internal medicine specialists with experience in ultrasonography, or by board-certified radiologists prior to surgery.
Results of laboratory testing (complete blood counts and serum biochemical profiles) were available for 27 of the 31 cats and all eight dogs. All parameters were within reference ranges for 13 cats and four dogs. In the remaining cases, the most common abnormal finding on biochemical analysis in both dogs (3/8) and cats (4/27) was an elevated alanine aminotransferase (ALT) level. Various nonspecific abnormal findings were detected in the remaining animals. Nonspecific laboratory findings in cats included significant anemia (n=1), mild hyperglycemia (n=3), a mildly elevated creatine kinase (n=3), a mildly elevated alkaline phos-phatase (ALP; n=2), an elevated creatinine, an elevated bilirubin, an elevated aspartate aminotransferase, eosinophilia, mature neutrophilia, hyperkalemia, and hypocholesterolemia (n=1 each). Nonspecific laboratory findings in dogs included elevated ALP (n=2), mature neutrophilia, an elevated total bilirubin, elevated packed cell volume (PCV), and decreased platelet count (n=1 each).
Concurrent medical conditions diagnosed in cats (n=1 each) presented with PPDH included hypertrophic cardiomyopathy, polycystic kidney disease or polycystic kidney and liver disease, linear foreign body, intussusception, chylothorax, inflammatory bowel disease, gastroenteritis, sternal defect, and diaphragmatic rent. Two cats had reportedly experienced a recent trauma near the time of diagnosis of PPDH. Two cats had a history of large umbilical hernias that were repaired when they were kittens. Concurrent conditions in dogs included a gastric foreign body (n=2) and gastric dilatation volvulus (GDV; n=1).
Following a tentative diagnosis of PPDH made by the referring veterinarian, all 39 animals were referred to Veterinary Surgical Associates for surgical repair of PPDH. In all cases, a cranial abdominal midline approach was made. Upon confirming the PPDH, the pericardial-diaphragmatic defect was closed by apposing the diaphragmatic remnants with absorbable or nonabsorbable suture. A thoracostomy tube was placed in animals in which adhesions to the pericardium were encountered and a partial pericardiectomy was necessary, resulting in entrance to the pleural space. Surgical correction did not require entrance to the pleural space in all cases. In animals in which thoracostomy tubes were required, the tubes were removed immediately after recovery or within 12 hours of recovery (in most cases) once negative intrapleural pressure was established. One cat required a thoracostomy tube to remain in place for 48 hours until pleural effusion was minimal. Some animals required immediate surgical intervention for the above-described concurrent problems, such as GDV and gastrointestinal obstruction from intussusception or foreign bodies.
Abdominal viscera found within the pericardial sac in cats included the liver (n=31), gallbladder (n=14), intestines (n=9), omentum (n=8), spleen (n=6), colon (n=4), pancreas, falciform fat, stomach, and an enlarged reactive lymph node (n=1 each). Clotted blood was in the abdomen of one cat. Adhesions between the pericardium and herniated structures were noted in nine cats. Specifically, adhesions of herniated liver lobes to the myocardium were noted in two cats. Liver lobectomy was performed in three cats; a hepatic cyst was excised in one cat; and an urachal diverticulum was excised in one cat.
Abdominal viscera found within the pericardial sac in dogs included the liver (n=6), gallbladder (n=6), omentum (n=5), intestines (n=4), spleen (n=3), colon (n=2), pancreas (n=1), and falciform fat (n=1). In one dog, adhesions between the pericardium and herniated structures were present, and one dog had adhesions of the liver to the myocardium. Gastric foreign bodies were removed in two dogs; gastropexy was performed in two dogs; and an ovariohysterectomy was performed in one dog.
Perioperative complications were noted in 58% (18/31) cats and 62.5% (5/8) dogs. Hyperthermia was the most common minor perioperative complication and was detected in 12.9% (4/31) cats. Hyperthermia was first detected within 1 to 12 hours after surgery and resolved within 12 hours of detection; however, it did persist for 48 hours in one cat. Frantic behavior (attributed to a fentanyl constant-rate infusion) occurred in one cat in the immediate postoperative period. A major intraoperative complication in one cat was penetration of the ventricle during dissection of an adhesion between the liver and myocardium, which was successfully repaired. Another major intraoperative complication was hypotension (n=1). Major complications in the first 24 hours postoperatively included the development of pleural effusion (n=2), oxygen dependency (n=1), and pulmonary edema (n=1). In dogs, the only major intraoperative complication was hypotension (n=1).
In cats, minor postoperative complications included vomiting and diarrhea (n=2), surgical wound inflammation (n=2), occasional cough, anorexia, pain, and sneezing (n=1 each). No major complications were noted during the postoperative period.
Only one dog had a major postoperative complication, which was dehiscence of the skin incision secondary to self-trauma. This wound was successfully repaired. Minor postoperative complications that occurred in dogs included seroma formation, incisional irritation, soft stool, continued vomiting, and regurgitation (n=1 each).
The overall mortality was 5.1% (2/39), involving one (3.2%) of the 31 cats and one (12.5%) of the eight dogs. The cat died of congestive heart failure secondary to chronic, hypertrophic, obstructive cardiomyopathy diagnosed on echocardiography 9 days postoperatively; the cardiomyopathy failed to respond to medical therapy. The dog suffered cardiopulmonary arrest the morning following surgical correction of PPDH and could not be resuscitated.
Discussion
Consistent with previous reports, no sex predilection was identified in the cats included in this study.2,9,15 Similarly, no sex predilection was detected in the dogs in this study. This finding is in contrast to previous reports where male dogs were predisposed to PPDH.2,9 Median ages at time of presentation were 48 months for cats and 30 months for dogs. Cats of long-haired breeds were overrepresented in this study. Previous reports have suggested that Persians and other long-haired breeds, including domestic long-haired cats and Himalayans, are predisposed to PPDH.11,14,15 Weimaraners represented the majority of dogs (5/8) in our study and have been previously reported to be at an increased risk for PPDH.9,16
Subsequent to presumptive diagnosis of PPDH, all 39 animals included in this study were referred to Veterinary Surgical Associates for surgical repair of PPDH. Therefore, we cannot accurately assess whether an animal’s clinical signs were directly related to the PPDH. Nonetheless, clinical signs in animals included in this study were similar to those historically reported. Clinical signs were primarily attributable to the respiratory or gastrointestinal tracts.2,3,5,6,9–11,14,15,17 Clinical signs were generally non-specific or respiratory related in cats, with tachypnea and dyspnea being the most common clinical findings upon presentation. In contrast, gastrointestinal signs were more prevalent in dogs. Acute vomiting was the presenting clinical sign for half of the dogs but only three of the 31 cats. Of those four dogs, two had confirmed gastrointestinal disease unrelated to PPDH (e.g., GDV, gastric foreign body), which could explain their clinical signs. The dog with GDV also had a gastric foreign body removed, and the presenting clinical signs were thought to be related to the GDV. The other dog with a gastric foreign body was asymptomatic, and the foreign body was considered to be an incidental finding. Of the three cats having gastrointestinal signs at presentation, two had concurrent gastrointestinal disease (such as inflammatory bowel disease or linear foreign body) that could explain the clinical signs. One cat with an intussusception did not show clinical signs associated with the gastrointestinal tract; the only reported presenting sign was hiding.
In this study, three cats and two dogs had no clinical signs at the time of presentation. Abdominal ultrasonography and radiography leading to the diagnosis of PPDH were performed in one cat after mildly elevated ALP and ALT were noted on routine annual laboratory tests. One cat had PPDH diagnosed when radiography was performed after muffled heart sounds were noted on physical examination following the cat’s ingestion of ivy. Diagnosis of PPDH was made in one cat when radiographs were obtained for evaluation of pollakiuria. One dog was diagnosed with PPDH when screening radiography was performed after two of her puppies were diagnosed with the condition. This dog also had a gastric foreign body noted at surgery. In the other dog, screening radiographs obtained (after the dog had chewed an electrical cord) were diagnostic for PPDH.
Muffled heart sounds were the most common physical examination finding in cats and dogs, consistent with previous reports.15,16 In contrast to a previous report in cats, muffled heart sounds were ausculted on both the left and right hemithoraces with equal frequency.15 In several cases, heart sounds were noted to be displaced to the left or cranially. Tachypnea was also a common finding in animals with PPDH, which can be explained by the presence of abdominal organs within the thorax, causing compression on the lungs. Other physical examination findings, which could have been attributed to herniation of abdominal viscera into the pericardial sac in our animals with PPDH, included an empty abdomen on palpation or palpation of a “full” cranial abdomen, decreased lung sounds, thoracic borborygmi, and pericardial friction rub. A heart murmur was noted in two cats, neither of which was subsequently diagnosed with primary cardiac disease. It is plausible that compression of the myocardium due to presence of abdominal organs within the pericardial sac altered blood flow within the heart, causing turbulent flow auscultable as a murmur. Interestingly, the cat with hypertrophic obstructive cardiomyopathy had muffled heart sounds and did not have a murmur ausculted prior to surgery.
Seven cats had a thin body condition, which may have been related to chronic disease. Although decreased appetite was not always noted by the owners, these cats may have had chronic, intermittent anorexia or vomiting that was not perceptible or was considered normal for the cat by the owners. Depression and dehydration were nonspecific findings that could have been correlated to the animals’ presenting complaints of inappetence, vomiting, or hiding behavior.
Elevated rectal temperature of 104°F was noted in one dog on presentation to the referring veterinarian; the fever had resolved prior to presentation to our hospital a few hours later, after a single dose of enrofloxacin. The dog also had a neutrophilia at the time of presentation to the referring veterinarian. At the time of surgery, the pancreas of this dog was entrapped within the pericardial sac. The neutrophilia and fever were thought to be related to acute pancreatitis, although no specific testing for pancreatitis was performed.
Diagnosis of PPDH in all animals was made by interpretation of thoracic radiographs.9,10 One cat and one dog had barium administered to confirm the diagnosis of PPDH.9,10,12,13 Upper gastrointestinal studies are diagnostic of PPDH when barium-filled loops of bowel are contained within the pericardial sac; however, absence of this finding does not rule out PPDH. In the cat, the gastrointestinal tract was noted to be completely within the abdomen, whereas barium-filled loops of intestine were present in the pericardial sac of the dog. Given that the liver is the most commonly reported organ to be herniated into the pericardial sac in cats,3,15 the lack of barium-filled loops of bowel visualized in the pericardial sac on barium series in this study is not surprising. If confirmation of a PPDH diagnosis is desired, and ultrasonography is unavailable, a positive-contrast peritoneogram may be useful; however, false negatives are also possible if the diaphragmatic defect is sealed by the herniated organs.9,14
Ultrasonography was not performed in all animals, but when it was performed, findings confirmed the radiographic diagnosis.10,11 Echocardiographic evaluation was not performed in most cases. Of the 11 cats in which thoracic ultrasonography was performed, medical records of only two cats contained information regarding cardiac function. Echocardiographic abnormalities in one of these two cats included mild mitral regurgitation and decreased diastolic filling. No information was in the medical record regarding the echocardiographic findings in the cat with previously diagnosed hypertrophic obstructive cardiomyopathy. Echocardiographic findings are relevant in animals with PPDH, because PPDH is believed to potentially cause cardiac compromise.9,10,12,18–20 Peritoneopericardial diaphragmatic hernia may also occur concurrently with other congenital cardiac defects19 such as aortic stenosis,3 patent foramen ovale,6 ventricular septal defect,18 and pulmonic stenosis.18
Consistent with previous reports, laboratory findings were normal in most cases, and no findings were pathognomonic for PPDH.3,15 The most common laboratory finding in both cats and dogs was elevated ALT, which is common with hepatocellular damage from any cause. Since the liver is the most common organ herniated in PPDH, the elevation of ALT is possibly a result of trauma to the liver because of its location. Serum ALP was elevated in two cats and two dogs, and total bilirubin was mildly elevated in only one cat and one dog. These findings could also be consistent with liver and gallbladder irritation secondary to herniation. No other cause for elevation of these enzymes was noted in any animals of this study.
The cat with significant anemia had a PCV of 16% (reference range 29% to 45%) at the time of presentation; the anemia was regenerative, responsive to a red blood cell transfusion, and did not recur. A specific cause of the anemia was not identified. Three cats had mildly elevated blood glucose, which could have been related to stress from being hospitalized or from physiological effects caused by the presence of PPDH. All three cats with mild hyperglycemia had clinical signs such as coughing, increased respiratory effort, lethargy, and vomiting; these signs could be attributed to PPDH. Mild, mature neutrophilia—most likely related to stress—was also present in one cat and one dog. Mildly elevated creatine kinase was noted in three cats and was most likely related to restraint for examination and blood draw. The dog with PPDH and concurrent GDV had an elevated PCV and decreased platelet count, which could have been related to hemoconcentration resulting from hypovolemic shock and platelet use from tearing of the short gastric vessels secondary to the GDV.
An elevated creatinine was noted in one cat, which was attributed to prerenal azotemia from dehydration, as the cat had a urine specific gravity of 1.045. One cat that had an eosinophilia also had a chronic, intermittent dry cough and was suspected of having feline allergic bronchitis. Hyperkalemia was noted in one cat on referral blood work, which was normal on recheck at our hospital prior to surgery. Hypocholesterolemia was noted in one 8-month-old kitten that also had elevated serum ALT and ALP levels, which could be attributed to fasting, primary liver disease, or entrapment of the liver in the hernial sac. The kitten had no presenting clinical signs, and PPDH was diagnosed based on medical workup for the laboratory abnormalities noted on routine blood work. A liver biopsy was not performed at the time of surgery.
Concurrent congenital midline anomalies have commonly been reported in cats and dogs with PPDH.3,6,9,15,21,22 In this study, evaluation of medical records identified one cat with a sternal defect and two cats with umbilical hernias. The cats with umbilical hernias had large body wall defects that required surgical repair at a young age. One Persian cat had polycystic kidney disease, and one Himalayan cat had both polycystic kidney and liver disease at the time of surgery. Polycystic disease has been reported previously in these breeds and has been previously associated with PPDH.8,14,15,23
All surgical procedures were performed by a diplomate of the American College of Veterinary Surgeons or a resident-trained surgeon with direct diplomate supervision. Therefore, the level of surgical experience could not be evaluated as a factor related to morbidity and mortality.
At surgery, the liver and gallbladder were the organs most commonly found to be herniated into the pericardial sac in both dogs and cats. All abdominal organs except the adrenal glands and urinary tract are susceptible to herniation. No herniation of the uterus and ovaries occurred in our study, though this has been previously reported.24 Only one female dog in this study was intact at the time of presentation, and ovariohysterectomy was performed at the time of herniorrhaphy. Small intestine was herniated in 29% (9/31) of cats but in 50% of the eight dogs. This finding may explain the fact that dogs tended to have more clinical signs related to the gastrointestinal tract, and cats tended to have signs more commonly related to the respiratory tract.
In the cat that had an intussusception, the intussuscepted segment of intestine was located within the pericardial sac at the time of surgery. On preoperative physical examination, however, a firm, tubular structure was palpable within the abdomen. This suggested that the herniation of the intussuscepted intestinal loop into the pericardial sac may have been a dynamic process in this cat.
Adhesions were present in several animals, a finding which has been noted in previous reports.2,5,14,15,22 In cats, the liver was either adhered to the pericardium or to the myocardium itself. Adhesions in the dogs differed from those identified in the cats. Of the two dogs with adhesions present at surgery, one had adhesions of the gallbladder to the pericardium, while the other had adhesion between the omentum and left atrium. In general, adhesions to the pericardium can be addressed by excision of the affected portion of pericardium. In the two cats with adhesions between liver and myocardium, successful debridement of the adhesions was not achieved. In one case, the ventricle was inadvertently entered during attempted debridement. The surgeon attempted gentle debridement of the liver from the myocardium in the second cat, but because significant manipulations were required with minimal results, the procedure was deemed unsafe for fear of penetrating the ventricle. In both cases, the PPDH was incompletely closed around the liver, leaving the liver in situ but presumably preventing further herniation of other organs. Extension of the abdominal incision to include a caudal median sternotomy may be required to allow for full debridement of adhesions, if necessary.
One cat presented with labored breathing and was diagnosed with concurrent chylothorax. At surgery, the PPDH was repaired, but no additional treatment for chylothorax was performed based on the supposition that the herniation of the liver may have been the cause of the chylothorax. Signs of pleural effusion did not recur in the perioperative period.
Chylothorax in conjunction with PPDH has been previously described; however, a direct correlation between chy-lothorax and PPDH has not been shown.15,25 In the three cats described in those two studies, chylous effusion was either persistent or it recurred (in 1 week for one cat and in 27 days for the other) after surgical correction of PPDH.15,25 Chylous effusion resolved after thoracic duct ligation was performed in one of the three cats in the published reports, suggesting that PPDH was an incidental finding and not associated with the chylothorax.25
Nonchylous pleural effusion was a major complication in the immediate postoperative period in two cats included in this study. In one of these cats, pleural effusion was preexisting and thought to be cardiogenic in origin. Echocardiography information was not available for either of these two cats. Pleural effusion could have been induced by inflamed, herniated viscera or the surgical procedure itself. Both cats with pleural effusion were discharged without complication. Nonchylous pleural effusion after PPDH correction was previously reported in one cat.15
Complications of PPDH repair were not common in the perioperative period. The majority of complications that occurred were minor. Of the minor complications, transient hyperthermia in cats was most common. Postoperative hyperthermia, reported in 54% of cats that are surgically treated for PPDH,15 was noted in 13% of the cats in this study. The hyperthermia noted in the animals of our study was transient and self-limiting. Opioid administration has been shown to cause postoperative hyperthermia in cats and was most likely the cause of the transient hyperthermia in our animals.26,27
Reexpansion of chronically atalectic lung has been a suspected cause of pulmonary edema after correction of PPDH.15 Reexpansion pulmonary edema (REPE) is known to occur after correction of congenital and traumatic diaphragmatic hernias.28 One cat in our study had postoperative pulmonary edema, but this finding was attributed to congestive heart failure secondary to hypertrophic cardiomyopathy rather than REPE. The mechanism by which REPE occurs is unclear, as pericardial distension is unlikely to cause chronic atelectasis. To our knowledge, REPE following pericardiocentesis in animals with chronic pericardial effusion has not been reported.
The postoperative mortality rates in this study were 3.2% and 12.5% in cats and dogs, respectively. The mortality rate in cats after surgical correction of PPDH in this study is lower than the mortality rate of 14% recently reported.15 In that study, four of the five cats died within the first 2 weeks postoperatively, and three of those cats had periods of hypoventilation noted during surgery or in the immediate postoperative period.15 All of our animals were maintained on a mechanical ventilator throughout the procedure, and no episodes of hypoventilation were noted, which may have contributed to a lower mortality rate. Precise, controlled ventilation by use of a mechanical ventilator is recommended during anesthesia for animals undergoing surgical correction of PPDH. In the animals of this study, two died within the perioperative period. The cat died of complications attributed to hypertrophic obstructive cardiomyopathy and recurrent congestive heart failure, and the dog suffered cardiopulmonary arrest the morning following surgery. That dog’s presenting complaint was an acute episode of collapse, and a specific cause of collapse was not identified and may not have been related to the PPDH.
The limitations of this study are primarily related to its retrospective nature. A consistent protocol for preoperative evaluation was not used, and all animals were referred for surgical correction of the PPDH, regardless of the original presenting clinical signs. The small sample size must also be considered when evaluating the results of this study.
Conclusion
The prognosis for cats and dogs with PPDH undergoing surgical repair is excellent for return to normal function. Perioperative complications, although common, were typically minor and self-limiting. Postoperative complications and mortality rates measured within 2 weeks of surgery were low and seemingly unrelated to surgical correction of the PPDH.
References
