Diaphragm: hernia in Horses (Equis) | Vetlexicon
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Diaphragm: hernia

ISSN 2398-2977


Introduction

  • Rare.
  • Cause: congenital (rare) or acquired (trauma).
  • Signs: death, colic, respiratory embarrassment, but very variable.
  • Diagnosis: radiography, ultrasound, clinical signs; often not diagnosed until laparotomy.
  • Treatment: surgery.
  • Prognosis: guarded.

Presenting signs

Acute presentation

  • May be found with acute abdominal pain Abdomen: pain - adult, and evidence of shock Cardiogenic shock.
  • Sudden herniation of intestines through defect may show sudden, severe respiratory signs.

Geographic incidence

  • Very rare.

Age predisposition

  • If congenital, may be younger; however can occur in any age.

Breed/Species predisposition

Cost considerations

  • Considerable: these cases are very intensive and often quite costly to address.

Special risks

  • Anesthesia Anesthesia: general - overview:
    • Problem of lung compression due to herniated intestines. Most critical when positioning the horse in dorsal recumbency.
    • IPPV is necessary throughout surgery as there is an incomplete mediastinum in most adult horses.
    • Before final closure, lungs should be maximally inflated to expel as much air as possible from the thorax.
    • Venous return may also be diminished from obstruction, leading to decreased preload, stroke volume, and cardiac output.
Tilting the table can reduce herniation.

Pathogenesis

Etiology

  • Congenital:
    • As a result of failure of fusion of diaphragm during fetal development.
    • Congenital defects most commonly reported in the left dorsal quadrant of the diaphragm. One such type is known as a Morgagni or retrosternal hernia, in which the bowel is contained within a hernia sac.
  • Acquired: usually in association with a fall, violent exercise, external trauma, or increased abdominal pressure. Most often seen in the middle portion of diaphragm.
  • Euthanasia Euthanasia: ruptured diaphragms have been reported at postmortem in animals with no previous history or clinical signs. Such defects are usually located dorsal to the xiphoid and are presumed to occur at the time of euthanasia.

Pathophysiology

  • Small defects allow herniation of small intestine; accumulation of gas and ingesta in these cases leads to rapid incarceration and strangulation Umbilicus: hernia (strangulating), leading to severe abdominal pain and deterioration in cardiovascular status due to endotoxemia Systemic inflammatory response syndrome.
  • Large defects allow the large colon, stomach and/or liver to enter the thoracic cavity; strangulation in these cases is uncommon. Signs probably related to bowel distension and mesocolon tension.

Timecourse

  • Onset of clinical signs variable and dependent on volume of intestines herniated and if there is any strangulation.

Diagnosis

Presenting problems

Client history

  • Trauma, eg fall or violent exercise.
  • Recurrent colic Abdomen: pain - adult: horse may show evidence of colic when varying amounts of intestines herniate through the defect.
  • Weight loss/failure to maintain condition Weight loss: overview.
  • Pregnancy.
  • If in a foal, may have been dystocia at birth Reproduction: dystocia.

Clinical signs

Diagnostic investigation

Radiography 

  • See Thorax: radiography.
  • May not always be practical.
  • Most consistent finding is loss of diaphragmatic line.
  • Multiple fluid lines may be observed.

2-D Ultrasonography

  • See Ultrasonography: thorax.
  • Used to assess relationships of the thoracic wall, pleural cavity and lung parenchyma.
  • May reveal gas filled loops of intestine or excessive pleural fluid.
  • May see evidence of hemorrhage on transabdominal ultrasound.

Other

  • Auscultation Thorax: auscultation:
    • Thoracic auscultation may reveal borborygmi.
    • However, inconsistent finding and referred borborygmi can be normal.
    • Thoracic percussion Thorax: percussion may reveal lack of resonance.
    • Absence of lung sounds focally or in ventral thorax.
  • Rectal examination Urogenital: rectal palpation:
    • Often non-diagnostic.
    • May get the impression of an 'empty' caudal abdomen.
    • If intestines are strangulated then may be distended small intestines Umbilicus: hernia (strangulating).
    • Other findings have included taut mesentery, dry feces and no feces.
  • Fluid/aspirate analysis:
    • Abdominocentesis Abdomen: abdominocentesis may reveal evidence of recent hemorrhage if there has been acute trauma, or findings consistent with strangulated intestine.
    • Thoracentesis Thorax: thoracentesis may also show evidence of acute hemorrhage (care with thoracentesis in suspected cases because bowel trauma → leakage into thorax).

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

Gross autopsy findings

  • Defect in diaphragmDiaphragm: hernia 01 - pathologyDiaphragm: hernia 02 - pathologyDiaphragm: hernia 03 - pathology:
    • Congenital lesions most common in left dorsal quadrant.
    • Acquired lesions most common in middle portion.
    • Lesions associated with euthanasia usually located dorsal to the xiphoid.

Histopathology findings

  • Can discern between acute tear versus chronic hernia sac based on presence of fibrosis within edges of hernia.

Differential diagnosis

Treatment

Initial symptomatic treatment

Standard treatment

  • Difficult to manage successfully as there is poor surgical access and the diaphragm has a poor suture holding capacity.
  • Immediate repair indicated if pain is non-responsive to analgesia, there is respiratory embarrassment or there is evidence of strangulation.
If an acute hernia is not accompanied by severe signs then repair should be delayed for 3 weeks to allow more secure suture placement in fibrosed tissue. The horse should be box rested and monitored for colic.
  • Approach via a ventral mid-line laparotomy Abdomen: laparotomy, unless dorsal hernia then a thoracotomy Thorax: thoracotomy is more suitable.
  • Assess all abdominal viscera.
  • In some cases, it may be necessary to enlarge defect first to allow reduction of incarcerated intestine.
  • Small defects can be sutured. Large defects require mesh herniorrhaphy.
  • If mesh is used air will continue to move until fibrosis occurs; a flap consisting of transversus muscle and peritoneum can be used to seal to effect and encourage fibrosis.
  • Antibiotic cover Therapeutics: antimicrobials is necessary if mesh is used or if there is any intestinal resection. Analgesia Anesthesia: analgesia - overview should be given as necessary.

Monitoring

Subsequent management

Treatment

Monitoring

Prevention

Control

  • Closure of the hernia, if possible.

Outcomes

Prognosis

  • Guarded.

Reasons for treatment failure

  • Sequelae associated with damage to abdominal organs.
  • Dehiscence of repair.
  • Rupture at another location.
  • Wound dehiscence at celiotomy.
  • Death secondary to cardiovascular or respiratory failure.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Loynachan A T (2022) Equine pulmonary agenesis and hypoplasia associated with diaphragmatic herniation. J Equine Vet Sci 109, 103855 PubMed. 
  • Abu-Seida A (2021) Diagnostic and treatment challenges for diaphragmatic hernia in equids: a concise review of literature. J Equine Vet Sci 106, 103746 PubMed. 
  • Bauck A G, Nelson E, McLain A et al (2021) J-incision to approach the cranial abdomen in the adult horse. Vet Surg 50 (3), 600-606 PubMed. 
  • Palmer J E (2012) Colic and diaphragmatic hernias in neonatal foals. Equine Vet Educ 24 (7), 340-342 WileyOnline.
  • Boerma S, Back W & Sloet van Oldruitenborgh-Oosterbaan M M (2012) The Friesian horse breed: A clinical challenge to the equine veterinarian? Equine Vet Educ 24 (2), 66-71 ResearchGate.
  • Pauwels F F, Hawkins J F, MacHarg M A et al (2007) Congenital retrosternal (Morgagni) diaphragmatic hernias in three horses. JAVMA 231 (3), 427-432 PubMed. 
  • Collier D S (2000) Comparative aspects of diaphragmatic hernia. Equine Vet J 31 (5), 358-359 PubMed.
  • Goehring L S, Goodrich L R & Murray M J (2000) Tachypnoea associated with a diaphragmatic tear in a horse. Equine Vet J 31 (5), 427-432 PubMed.
  • Edwards G B (1993) Diaphragmatic hernia - a diagnostic and surgical challenge. Equine Vet Educ 5 (5), 267-269 VetMedResource.
  • Proudman C J & Edwards G B (1992) Diaphragmatic diverticulum (hernia) in a horse. Equine Vet J 24 (3), 244-246 PubMed.

Other sources of information

  • Toth F & Schumacher J (2019) Abdominal Hernias. In: Equine Surgery. 5th edn. Eds: Auer J & Stick J. Saunders, USA. pp 645-659.