section name header

Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Herniation of abdominal viscera into the thoracic cavity through a diaphragmatic defect
  • Diaphragmatic hernia generally results in simple or strangulated obstruction of the herniated GI viscera and in hypoventilation

Signalment!!navigator!!

  • No sex or breed predilection
  • Most frequently observed in adult horses

Signs!!navigator!!

  • Abdominal pain, which may vary from mild, intermittent episodes of colic to severe, intractable pain
  • Alteration in respiration, which may vary from exercise intolerance, to tachypnea, to respiratory distress depending on the degree of decrease in thoracic volume
  • Clinical signs suggestive of hypovolemic shock, such as blanched mucous membranes, tachycardia, and collapse, may be observed when severe hemorrhage occurs in the abdominal or thoracic cavity

Causes and Risk Factors!!navigator!!

  • Diaphragmatic defects may be either congenital or acquired
  • Congenital defect results from incomplete fusion of the pleuroperitoneal folds, causing an enlarged esophageal hiatus
  • Acquired defects result from sudden increases in intrathoracic or intra-abdominal pressure. Acquired defects are usually observed after external trauma, strenuous exercise, GI distention, or pregnancy

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • All disorders resulting in acute abdominal pain in the horse
  • Pneumonia and pleuritis. Horses with diaphragmatic hernias usually are not pyrexic, are not depressed, and do not have inflammatory leukograms
  • Horses with diaphragmatic hernia may be exercise intolerant

CBC/Biochemistry/Urinalysis!!navigator!!

Usually normal.

Other Laboratory Tests!!navigator!!

Blood gas analysis may reveal hypercapnia. Respiratory acidosis or uncompensated metabolic acidosis is usually observed in horses with diaphragmatic hernia. The hypercapnia observed in horses with diaphragmatic hernia is associated with hypoventilation due to either thoracic pain and/or reduction of thoracic volume.

Imaging!!navigator!!

  • Thoracic radiography—standing lateral thoracic radiography is used to confirm a diagnosis of diaphragmatic hernia. Radiographic signs include gas-filled loops of intestines in the thoracic cavity, increased ventral thoracic density, and absence of the cardiac shadow. The most consistent radiographic sign is loss of the diaphragmatic shadow in the area of the hernia
  • Thoracic ultrasonography—reveals the presence of pleural fluid and of abdominal viscera in the thoracic cavity

Other Diagnostic Procedures!!navigator!!

  • Auscultation of the thorax of horses with diaphragmatic hernia reveals regions of thoracic dullness or reduced cardiac sounds on the involved side of the thorax. Referred GI sounds are frequently heard over the caudoventral thorax in normal horses
  • Abdominal paracentesis usually yields a normal abdominal fluid; however, in the case of an acute acquired diaphragm defect, abundant hemorrhagic fluid may be obtained
  • ECG may reveal decreased amplitudes of the QRS complex

Treatment ⬆ ⬇

TREATMENT

  • Emergency exploratory celiotomy is performed under general anesthesia with assisted positive-pressure ventilator. Surgical treatment consists of reduction of the herniated viscera, resection of devitalized intestine, and intestinal anastomosis. Repair of the diaphragmatic defect is not always possible and may require a second procedure
  • In horses with acute diaphragmatic defects secondary to trauma, surgery may be delayed if the animal's condition is stable. Delay allows development of fibrosis of the edges of the defect and easier surgical closure
  • Preoperative fluid volume replacement therapy is accomplished with administration of lactated Ringer's solution at a rate of 3–6 mL/kg/h

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Preoperative and postoperative medications consist of systemic antibiotics (sodium penicillin G 20 000 IU/kg IV every 6 h and gentamicin sulfate 6.6 mg/kg IV every 24 h) and NSAIDs (flunixin meglumine 1 mg/kg IV BID).

Contraindications/Possible Interactions!!navigator!!

α2-Agonist agents, such as xylazine, detomidine, and romifidine, should be used with caution because these drugs have depressive effects in both the cardiovascular and respiratory functions.

Follow-up ⬆ ⬇

FOLLOW-UP

  • Postsurgical monitoring for the development of pneumothorax or pleural effusion
  • Restrict exercise for 90 days after the surgical correction of the hernia
  • Prognosis for survival of horses with diaphragmatic hernia is poor to guarded

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Abbreviations!!navigator!!

  • GI = gastrointestinal
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Bristol DG. Diaphragmatic hernias in horses and cattle. Comp Cont Educ Pract 1986;8:S407–S412.

Bryant JE, Sanchez LC, Rameriz S, Bleyaert H. What is your diagnosis? Herniation of the intestines into the caudal region of the thorax. J Am Vet Med Assoc 2002;15:1461–1462.

Malone ED, Farnsworth K, Lennox T, et al. Thoracoscopic-assisted diaphragmatic hernia repair using a thoracic rib resection. Vet Surg 2001;30:175–178.

Author(s) ⬆

Author: Ludovic P. Bouré

Consulting Editors: Daniel Jean and Mathilde Leclère