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A foal born with assisted delivery developed rib fractures and a diaphragmatic hernia. The hernia was repaired using surgical mesh. The filly was healthy 42 months later. Dystocia is a risk factor for rib fractures and traumatic acquired diaphragmatic herniation. Surgical mesh repair is an option for diaphragmatic defects.
Réparation d’une hernie diaphragmatique acquise à l’aide d’un treillis chirurgical chez un poulain. Un poulain né lors d’une parturition assistée a développé des fractures des côtes et une hernie diaphragmatique. La hernie a été réparée à l’aide d’un treillis chirurgical. La pouliche était en santé 42 mois plus tard. La dystocie est un facteur de risque pour les fractures des côtes et une hernie diaphragmatique acquise lors d’un traumatisme. Le treillis chirurgical est une option pour les défauts diaphragmatiques.
(Traduit par Isabelle Vallières)
Diaphragmatic hernias are an uncommon source of colic and respiratory signs in equine neonates (1–3). A recent study described 137 equine neonates < 30 d old with colic, 15 (11%) of which were managed surgically with open techniques, including 1 with diaphragmatic hernia (1). Although minimally invasive techniques have been reported (4,5), ventral open celiotomy affords good exposure for repair of ventral diaphragmatic defects in foals and facilitates reduction of herniated viscera (6). This report describes successful open reduction and surgical mesh repair in a 41-day-old foal with diaphragmatic laceration and hernia secondary to rib fracture.
A hospitalized 8-year-old, 523-kg, primiparous Appaloosa mare undergoing treatment for pneumonia, developed premature placental separation at 335 d of gestation. Assisted vaginal delivery facilitated birth of a 29.5-kg filly foal. The filly was treated with oxygen per nasal cannula, approximately 170 mL/kg body weight (BW) per minute, mannitol (Hospira, Lake Forest, Illinois, USA), 250 mg/kg BW, IV over 20 min, mare colostrum per nasogastric tube, 34 mL/kg BW split into 2 doses, amikacin (Amiglyde-V; Fort Dodge Animal Health, Iowa, USA), 25 mg/kg BW, IV, q24h, and potassium penicillin (PenOne Pro; VetOne, Norbrook Laboratories, Newry, Northern Ireland, UK), 22 × 106 units/kg BW, IV, q6h.
Despite therapy, in the first 12 h of life the foal became progressively obtunded with absent suckle reflex and was unable to stand on her own or hold up her head. Serum IgG concentration was > 80 g/L. The filly was administered mare’s milk by nasogastric tube at 10% of BW, q24h. However, attempts to increase feeding quantity resulted in bloat and signs of colic. Therefore, parenteral nutrition was started on day 3. On day 4, the foal developed increased abdominal respiratory effort and crackles were heard on auscultation of the right thorax, in addition to an audible click of the right hemithorax. Subsequent thoracic radiographs revealed an alveolar pattern in the cranioventral lung lobes and bronchopneumonia. Fracture of ribs 5, 6, and 7 on the right side was also visible. Despite this, the foal continued to get stronger and began nursing from the mare. Nasogastric feeding and parenteral nutrition were then discontinued on day 7. Thoracic radiographs repeated on day 13 showed worsening bronchopneumonia. In addition, the ventral aspect of the diaphragm could not be visualized, and pleural effusion was suspected, which was confirmed with thoracic ultrasound.
On day 22, the foal became lethargic and febrile. A trans-tracheal wash was performed, revealing a mixed growth of Escherichia coli and Staphylococcus spp. The antibiotic regimen was then changed to chloramphenicol (Viceton; Bimeda, Le Sueur, Minnesota, USA), 50 mg/kg BW, PO, q6h, and nebulization with amikacin, q24h for 8 d. Radiographs on day 25 showed mild improvement in the pneumonia but evidence of bronchitis in the caudal lungs. On day 35, the foal developed signs of colic. Colic signs resolved with administration of flunixin meglumine (Prevail; Bimeda-MTC Animal Health, Cambridge, Ontario), 1.1 mg/kg BW, IV. Mineral oil and water were given via nasogastric tube. Abdominal radiographs taken on day 36 revealed gas-filled loops of intestine, as well as a cavitated soft tissue opacity in the caudal ventral thorax. Differential diagnoses included diaphragmatic hernia and a caudal ventral lung abscess, in addition to colonic impaction. At this time, the foal had not defecated for 24 h. A muzzle was placed to prevent ingestion of hay or straw, but the filly was allowed to nurse hourly. Crystalloid IV fluids (Veterinary Plasma-lyte A; Abbott, North Chicago, Illinois, USA) were administered as boluses at 10 mL/kg BW, q4h, and another dose of mineral oil was administered via nasogastric tube. On day 39, crystalloid IV fluids were discontinued and the foal was nursing well and produced normal feces. On day 41, signs of colic returned. Radiographic and ultrasonographic examination confirmed diaphragmatic hernia based on presence of intestinal loops within the thoracic cavity (Figure 1). Surgery was recommended to repair the hernia.
Following pre-oxygenation, the foal was induced with ketamine (VetaKet; Akron, Lake Forest, Illinois, USA), 3 mg/kg BW, IV and diazepam (Hospira), 0.1 mg/kg BW, IV and maintained on isoflurane (Piramal Health Care, Bethlehem, Pennsylvania, USA) in 100% oxygen with positive pressure ventilation. Lidocaine (Hospira), 10 μg/kg BW per minute, IV and lactated ringer’s solution (Hospira), 2 mL/kg BW per hour, IV, were administered during surgery.
A routine ventral midline celiotomy incision was created following aseptic preparation. A 10-cm diameter circular defect was found in the ventral right diaphragm, through which the large colon and a small amount of jejunum were incarcerated in the right thorax. Using gentle traction, the entrapped bowel was removed from the thorax. Removal was facilitated by digital separation of several fibrinous adhesions between the bowel and thoracic body wall adjacent to the site of rib fracture. An omentectomy was performed to remove a segment of omentum adhered to the edge of the diaphragmatic defect. The size of the diaphragmatic defect prevented primary closure. A double layer of woven plastic surgical mesh (Proxplast; Goshen Laboratories, Goshen, New York, USA) was positioned over the defect and secured in place with #2 interrupted horizontal mattress polyglactin 910 sutures (Vicryl; Ethicon, San Angelo, Texas, USA). Balfour retractors facilitated surgical exposure. The incarcerated intestines appeared healthy except for a 1-cm diameter abraded area of the large colon, which was oversewn with 2-0 carbonate-dioxanone copolymer (Biosyn; US Surgical, Norwalk, Connecticut, USA) in a cushing pattern. Sterile 1% carboxymethylcellulose solution (Aqualon; Ashland, Russell, Kentucky, USA) was instilled before closure. A tube (Argyle trochar catheter, sharp tip, 5.3 mm × 25 cm; Covidien, Mansfield, Massachusetts, USA) was placed transcutaneously in the right thoracic cavity to allow evacuation of air and fluid, and was maintained for 24 h after surgery. The foal recovered well from anesthesia.
Chloramphenicol, 50 mg/kg BW, PO, q6h, and crystalloid IV fluids (Veterinary Plasma-lyte A), 10 mL/kg BW, q4h, were continued for 7 d. Eight days after surgery, thoracic radiographs revealed resolving bronchopneumonia. The foal was discharged 19 days after surgery. The abdominal incision was healing well upon recheck 5 wk after hospital discharge. Radiographs confirmed resolution of pneumonia. A follow-up phone call to the owner 42 mo later revealed that the horse had no further illnesses or injuries and was doing well in training.
An acquired diaphragmatic hernia was identified in the foal in this report. The diaphragmatic hernia was assumed to be due to traumatic laceration secondary to displaced rib fractures. The diaphragmatic defect was located adjacent to the fracture location near the costochondral junction of the right 5th, 6th, and 7th ribs and surrounding ossification, similar to previous reports (7). Also supportive of traumatic diaphragmatic laceration was the omental adhesion present on the edge of the defect (8). Birth trauma is a common source of neonatal rib fractures, especially in filly foals born to primiparous dams and with dystocia (9–11). Ultrasonographic imaging has been recommended to assess foals with suspected rib fracture because of improved sensitivity in detection and characterization of thoracic abnormalities in these cases (9,10). Foals with fractures of the 4th, 5th, and 6th ribs are most likely to develop serious trauma of the surrounding soft tissues, including diaphragmatic laceration, resulting in life-threatening injury (9,12,13). Displaced rib fractures are often accompanied by an audible clicking sound during respiration, as in the present case. Early surgical repair of the rib fracture before fracture displacement might have avoided further injury, although repair at the time of diaphragmatic herniorrhaphy was not deemed necessary due to stable healing ossification, which is known to occur approximately 4 to 6 wk after injury in foals sustaining rib fracture in the neonatal period (12). The chronicity of cases in many horses with diaphragmatic hernia suggests a variable duration between traumatic diaphragmatic injury and herniation of alimentary contents, resulting in acute clinical signs of colic and/or respiratory distress (14). While it is likely that the foal herein developed the diaphragmatic laceration in the first week of life, acute incarceration of the viscera in the thoracic cavity precipitated further workup and eventual surgical correction of the defect at 41 d of age.
Diagnosis of diaphragmatic hernia can be challenging, with inconsistent history and physical examination findings (14). Diaphragmatic hernias often result in primarily colic signs, and less commonly with respiratory distress alone (14). The severity of clinical signs and prognosis are related to type, amount, and viability of the herniated abdominal contents (3). In most reported cases of diaphragmatic defects in horses, herniated contents are composed of small intestine or multiple alimentary organs, such as liver, stomach, and small intestines (2). Herniation of the large intestines into the thoracic cavity, with colonic haustra visible on thoracic radiographic examination, has been mentioned in previous reports (14), although the herniated colon is often non-viable contributing to poor prognosis (15). In addition to herniated viscera, hemoabdomen, hemothorax, and subsequent death have been described in 2 neonatal foals with acute rib fracture and diaphragmatic laceration in one report (9) and these conditions have been associated with acute neonatal rib fracture in other reports (13). The prognosis of the foal in the present report was good because of the minimal intestinal vascular compromise, although careful manipulation was still necessary to prevent intestinal perforation during reduction of the herniated contents, which has been reported during attempted removal of the large colon from the thorax of a horse (2). Large colon herniation is more commonly associated with right-sided diaphragmatic defects (6,7,14–16), as in the present report. Congenital and acquired hernias can occur on the left and right portions of the diaphragm, although left-sided defects are more common (2,3) which might, in part, account for the less common occurrence of large colon herniation.
Repair of diaphragmatic hernias in horses can be challenging, often due to the size and location of the tear. Correction of herniated alimentary organs alone, without direct repair, has not been successful due to the rapid recurrence of the entrapment (17). Furthermore, failure rates of diaphragmatic defect repairs are high, most occurring during anesthetic recovery (2,4,7) or within 30 d after surgery (2,3). Mesh repair has been reserved for large defects (7,16), defects in dorsal locations precluding direct suturing from a ventral celiotomy (17), and to complement and strengthen traditional suturing techniques (8). Despite perceived improvement in the strength of the diaphragmatic defects repaired with mesh, early failures still occur (2,4), perhaps due to weakness in the repaired tissues or high strain on the repaired defects during anesthetic recovery. Surgical mesh was used in the foal in the present report because of the size of the diaphragmatic defect and concerns regarding undue tension on the repair if direct suturing alone was utilized. The location of the implanted surgical mesh was, in part, covered by the liver, which limited contact with gastrointestinal organs and potentially minimized serosal abrasion and adhesion formation. Eschewing mesh (18) or complete separation of implanted mesh from viscera might result in the lowest risk (8), although as postoperative adhesions have been detected at celiotomy following traditional direct suturing techniques of diaphragmatic defects in horses (2), the surgeon should focus on repair integrity as a primary goal of the procedure.
In the present case, a chest tube was used to evacuate air from the right hemithorax at the end of the surgical procedure and was maintained through anesthetic recovery and for 24 h after surgery before removal. Maintenance of a chest tube during anesthetic recovery is critical to allow rapid intervention in foals that re-establish pneumothorax, which is a known source of co-morbidity and death following diaphragmatic herniorrhaphy (1,2). Radiographic or other imaging modalities could be used to confirm lung inflation prior to removal (4), though cessation of gas and fluid removal are also used to confirm appropriate timing of chest tube removal. Although poor ventilation, hypoxemia, and atelectasis commonly accompany herniation of alimentary organs into the thorax and re-expansion injury is a concern, removal of displaced organs from the thorax has been identified as the single most helpful factor in improving ventilation and gas exchange (19).
Survival rates of horses with diaphragmatic hernia are estimated to be between 11% and 25% (2–4). For horses undergoing surgical correction of diaphragmatic hernia, survival percentages are increased to between approximately 46% and 67% (2–4). In one report, 3 of 6 foals undergoing surgery for diaphragmatic hernia were euthanized during surgery due to presence and amount of compromised herniated intestine and of the 3 undergoing surgical repair, only 1 survived to hospital discharge (2). Although prognosis for surgical correction of diaphragmatic hernia in horses is fair, and even poorer in foals, if the initial repair is successful and does not fail in the immediate post-operative period, prognosis for return to athletic function can be good (2,4,17,20), as in the present case. CVJ
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No financial support or donations of equipment or drugs were received for the development of this report or in the diagnosis and treatment of the animal about which this report is written.