A 1-year-old 3.7-kg (8.1-lb) spayed female domestic shorthair cat was taken to the referring veterinarian for a routine examination. The cat had been found as a stray 1 month prior to the examination and appeared clinically normal. During the physical examination, palpation of the sternum revealed an approximately 5-cm-long defect in the bone. The heart was readily palpable and could be observed beating underneath the skin at the caudoventral aspect of the thorax. A freely movable 3-cm-diameter soft tissue mass consistent with a hernia was palpated along the cranioventral aspect of the abdomen. A grade I to II/VI systolic murmur was auscultated in the left parasternal region. The remainder of the physical examination was unremarkable. Thoracic and abdominal radiography revealed lack of fusion of the sternum and a soft tissue opacity at the cranioventral aspect of the abdomen consistent with a hernia. The cat was referred to the Soft Tissue Surgery Service at the University of Pennsylvania Ryan Veterinary Teaching Hospital for further evaluation.
During the initial physical examination at the veterinary teaching hospital, the cat was bright, alert, and responsive, and remarkable findings were similar to those reported by the referring veterinarian. Hematologic analysis revealed a mild leukocytosis (WBC count, 19,500 WBCs/μL; reference range, 4,040 to 18,700 WBCs/μL) and basophilia (195 basophils/μL; reference range, 0 to 100 basophils/μL). Serum biochemical analysis results were unremarkable.
The cat was anesthetized in a routine manner for a CT examination to further characterize the sternal defect. The CT scan revealed incomplete fusion of the sternum (Figure 1) and a PPDH that involved the central portion of the liver. The distance between the hemisternebrae was approximately 3 cm at the widest part of the sternal cleft. The scan also revealed multifocal alveolar changes with bronchiectasis, pleural thickening, and pulmonary nodules, which were believed to be secondary to an infectious or inflammatory process with or without an underlying allergic component. Surgery was recommended to correct the sternal cleft and repair the PPDH. However, on the basis of the leukocytosis, basophilia, and diffuse pulmonary abnormalities, the cat was sent home and treated with fenbendazole (50 mg/kg [23 mg/lb], PO, q 24 h for 10 days) for suspected lungworm infection before surgery was performed.
Three-dimensional CT reconstruction image of the thorax of a 1-year-old 3.7-kg (8.1-lb) domestic shorthair cat with a congenital sternal cleft. The cat also had a PPDH and a cranial midline abdominal wall hernia. Collectively, those defects were consistent with incomplete PC.
Citation: Journal of the American Veterinary Medical Association 254, 9; 10.2460/javma.254.9.1099
Following completion of the prescribed fenbendazole regimen, the cat was readmitted to the veterinary teaching hospital for surgical correction of the congenital defects. Prior to surgery, the cat was blood typed and crossmatched with an appropriately identified donor cat. It was classified in the American Society of Anesthesiologists class II anesthetic risk category and premedicated with oxymorphone (0.05 mg/kg [0.02 mg/lb], IM), dexmedetomidine (40 μg/kg [18 μg/lb], IM), and midazolam (0.2 mg/kg [0.09 mg/lb], IM). Anesthesia was induced with propofol (6 mg/kg [2.7 mg/lb], IV) and maintained with isoflurane in oxygen. The cat was also administered a morphine (0.1 mg/kg [0.045 mg/lb]) epidural and cefazolin (22 mg/kg [10 mg/lb], IV) perioperatively.
A ventral midline incision was made from the manubrium to the umbilicus. Because of the sternal defect and proximity of the heart to the skin, care was taken to ensure that the heart was not inadvertently damaged when the incision was made. A thin membranous layer of tissue was observed overlying the heart, which may have represented an incomplete pericardium or pleura (Figure 2), and that tissue was preserved during the repair. In addition to the sternal cleft, a cranial midline abdominal wall defect and a large PPDH were identified. To repair the sternal cleft, 25-gauge cerclage wiresa were preplaced in an interrupted manner around 4 left and 3 right hemisternebrae (Figure 3). A porcine small intestinal submucosa graftb was then placed over the entirety of the sternal cleft, and the preplaced cerclage wires were passed through the graft. A titanium contourable mesh platec was cut to span the sternal cleft and secured in place with the preplaced cerclage wires. The free edges of the small intestinal submucosa graft were wrapped around the perimeter of the titanium plate. A primary diaphragmatic herniorrhaphy was performed to correct the PPDH. The diaphragmatic remnants were sutured to the membranous pericardial tissue, porcine small intestinal submucosa graft, and titanium mesh with 2-0 polypropylene suture.d Free air within the pleural space was evacuated through an 8F red rubber catheter.e The surgical incision was closed in a routine manner. Postoperative thoracic radiographs were obtained and confirmed that the sternal defect, cranial midline abdominal wall hernia, and PPDH had been corrected (Figure 4).
Intraoperative photograph of the cat in Figure 1. The cat was positioned in dorsal recumbency, and a ventral midline incision was made from the manubrium to the umbilicus, with care taken to ensure that the heart was not inadvertently damaged. Notice a thin membranous layer of tissue, which was overlying the heart and might have represented an incomplete pericardium or pleura, is elevated to reveal the heart. That tissue was preserved during the repair.
Citation: Journal of the American Veterinary Medical Association 254, 9; 10.2460/javma.254.9.1099
Intraoperative photographs of the cat in Figure 1 that depict the procedural steps of the sternal cleft repair. A—Cerclage (25-gauge) wires were preplaced in an interrupted fashion around 4 left and 3 right hemisternebrae. Notice the thin membrane of tissue overlying the heart in Figure 2 extends across the sternal cleft. B—A porcine small intestinal submucosa graft was placed over the entirety of the sternal cleft, and the preplaced cerclage wires were passed through the graft. C—A titanium contourable mesh plate was cut to span the sternal cleft, placed over the small intestinal submucosa graft, and secured in place with the cerclage wires. The free edges of the small intestinal submucosa graft were wrapped around the perimeter of the titanium plate. D—The diaphragmatic remnants were sutured to the membranous pericardial tissue, porcine small intestinal submucosa graft, and titanium plate with 2-0 polypropylene suture. Right is to the left side of each panel.
Citation: Journal of the American Veterinary Medical Association 254, 9; 10.2460/javma.254.9.1099
Left lateral (A and C) and ventrodorsal (B and D) radiographic images of the thorax of the cat of Figure 1 obtained immediately (A and B) and 1 month (C and D) after surgery to repair the sternal cleft, cranial midline abdominal wall hernia, and PPHD. Notice that, at 1 month after surgery, the implants had not migrated and were intact with only mild bending at the cranial and caudal margins of the mesh plate.
Citation: Journal of the American Veterinary Medical Association 254, 9; 10.2460/javma.254.9.1099
Immediately after surgery, a constant rate infusion of dexmedetomidine (0.5 μg/kg/h [0.2 μg/lb/h], IV) was initiated for analgesia. The cat also received buprenorphine (0.02 mg/kg [0.009 mg/lb], IV, q 6 h), robenacoxib (2 mg/kg [0.9 mg/lb], SC, q 24 h), and cefazolin (22 mg/kg, IV, q 8 h). The next morning, the cat was bright, alert, and responsive. Two days after surgery, the constant rate infusion of dexmedetomidine was tapered and discontinued, and gabapentin (7 mg/kg [3.2 mg/lb], PO, q 12 h) was added to the treatment regimen. Administration of gabapentin, buprenorphine, robenacoxib, and cefazolin was continued for another day. The cat recovered well and was discharged from the hospital 4 days after surgery with instructions for the owner to administer cephalexin (22 mg/kg, PO, q 12 h) and buprenorphine (0.02 mg/kg [0.009 mg/lb], sublingually, q 6 to 8 h as needed for analgesia).
The cat was returned to the veterinary teaching hospital approximately 1 month after surgery for a recheck examination. The owner reported that the cat was doing well, and no postoperative complications had been observed. Thoracic radiographs were obtained and revealed that the surgical implants were intact with mild bending of the cranial and caudal margins of the mesh but no evidence of migration (Figure 4). The cat was reexamined 3 months after surgery. The owner reported that the cat continued to do well. Thoracic radiographs revealed no substantial changes to the implants from those observed on radiographs obtained during the 1-month postoperative recheck examination.
Discussion
The present report described successful surgical correction of a sternal cleft, PPDH, and ventral abdominal wall hernia in an adult cat. Sternal clefts are congenital malformations resulting from failure of midline fusion of the sternebrae and xiphoid process.1 Sternal abnormalities are rare in both veterinary and human patients and account for < 1 in 100,000 live births in humans.2,3 In the veterinary literature, sternal clefts have been described in 1 dog4 and 1 cat.5 For both veterinary and human patients with sternal clefts, surgical treatment is recommended during the neonatal period because the hemisternebrae can be easily apposed by primary closure owing to the expandability and elasticity of young cartilage relative to that of mature bone.4 Additionally, compression of intrathoracic organs resulting from apposition of the hemisternebrae is minimal during the neonatal period.6 For patients with sternal clefts, simple closure of the defect is generally recommended before more complex repair methods are pursued.2,3 The 1 dog4 (age, 5 months) and 1 cat5 (age, 2 months) with sternal clefts previously described in the literature were fairly young when the condition was identified and were therefore amenable to primary closure. Primary closure of a sternal cleft provides both a functional and cosmetic outcome and supports normal development and growth of the sternum.4
The cat of the present report was found as a stray approximately 1 month before it was initially examined by the referring veterinarian; therefore, its exact age was unknown, but it was believed to be approximately 1 year old. In human medicine, various techniques have been developed to address the lack of a sternum, excessive chest wall rigidity, and risk of excessive heart and lung compression in adolescents and adults with sternal clefts.6 Those techniques include the use of periosteal flaps from sternal bars and chondral grafts,7 periosteal flaps, pectoralis muscle transposition,8 titanium plates,2,3 stainless steel wire mesh, and various prosthetic materials such as polypropylene mesh.8 In human medicine, the use of prosthetic materials for sternal cleft repair is often discouraged because of the increased risk of infection and the inability of those materials to grow with the patient, compared with the use of autogenous or autologous materials.8 However, when the defect is too large for closure with autogenous or autologous materials, prosthetic and synthetic materials have been successfully used. For example, direct repair of a complete congenital sternal cleft in an adult human patient was successfully accomplished by the use of titanium plates fixed to the manubrium and costal cartilages with predrilled screws.2,3
The cat of the present report had an incomplete sternal cleft with a maximum hemisternebrae gap of 3 cm, which was approximately twice that in the cat of a previous report.5 The cat of that report5 was 2 months old, whereas the cat of this report was estimated to be approximately 1 year old, and there was concern that primary closure of the sternal cleft in an older patient might result in compression of the heart and lungs. Given the patient's age and the width of the sternal gap, and on the basis of descriptions of sternal cleft repair in adult human patients, we chose to use a titanium contourable mesh plate to span the sternal defect, which would provide adequate protection for the heart without causing undue tension on the surgical repair (ie, rib cage) or compression of the heart and lungs. A porcine small intestinal submucosa graft was placed between the titanium mesh plate and the soft tissues adjacent to the heart to help protect those tissues from any rough edges on the plate.
The cat of the present report had a PPDH and a hernia in the ventral abdominal wall in addition to a sternal defect. In human medicine, the combination of those 3 defects is described as incomplete PC.9 Complete PC is defined as a congenital defect in the inferior sternum, midline defect in the supraumbilical abdominal wall, intracardiac anomaly, deficiency in the anterior aspect of the diaphragm, and defect in the diaphragmatic pericardium.10 In human patients, the prevalence of PC varies from 5.5 to 7.9 cases/1 million live births.11,12 Pentalogy of Cantrell is further classified into 3 classes. All 5 defects are present in patients with class 1 PC.9 Four defects, including intracardiac and ventral abdominal wall abnormalities, are present in patients with class 2 PC.9 Various combinations of defects, including a sternal abnormality, are present in patients with class 3 (incomplete) PC.9 For human patients with PC, survival is associated with the severity of the cardiac malformations present and the degree of completeness of the syndrome.13 Incomplete PC (including a sternal cleft) has been described in a 5-month-old German Shepherd Dog.4
On the basis of the PC classification system outlined for human patients,9 the cat of the present report would be categorized as having incomplete (class 3) PC. It is important to note that, although a grade I to II systolic murmur was auscultated in this cat (which might have been consistent with an intracardiac abnormality and resulted in the cat being classified as having class 2 PC), no arrhythmias were appreciated and echocardiography was not performed. To our knowledge, the present report was the first to describe an adult cat with incomplete PC. Although long-term follow-up information was not available for this cat, the use of prosthetic materials, including a titanium contourable mesh plate and a porcine small intestinal submucosa graft, appeared to result in a successful outcome for this patient. Thus, similar techniques may be successful for the treatment of sternal defects in other cats.
Acknowledgments
No third-party funding or support was received in connection with this study or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.
ABBREVIATIONS
| PC | Pentalogy of Cantrell |
| PPDH | Peritoneopericardial diaphragmatic hernia |
Footnotes
Surgical stainless steel suture, Ethicon USA LLC, Somerville, NJ.
BioSISt, Vetrix Inc, Cumming, Ga.
MatrixNEURO, DePuy Synthes Vet, West Chester, Penn.
Prolene, Ethicon USA LLC, Somerville, NJ.
Medtronic Animal Health, Minneapolis, Minn.
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