43. Myth or Real? Idiopathic muscular hypertrophy of the distal oesophagus (IMHO) has been linked to perforation/rupture of the oesophagus.

Answer: Real

In a recently published case report from a research project done at the College of Veterinary Medicine at Iowa State University, oesophageal perforation within the thorax (chest) of 5 horses was examined. While perforation of the oesophagus “is an uncommon event that can occur for a variety of reasons”, the location where the oesophagus has been compromised plays a role in the prognosis. Intrathoracic rupture (within the chest cavity) of the oesophagus carries a grave prognosis, can occur spontaneously, may have no history of obstruction (“choke”) and may not be discovered until a secondary pleuropneumonia (inflammation of the tissue that lines the lungs and the chest cavity along with a pneumonia) has developed. This study looked at 5 cases, but I will touch on just the case involving a 15-year-old Friesian mare. She was presented to Iowa State 5 days after transport from PA to IA. Her medical history was uncertain, but she had not “choked” during transport. At examination, she had a fever, was depressed and not eating. Her heart and respiratory rates were elevated, an ultrasound revealed fluid in her chest and her blood work was abnormal. Chest tubes were placed and fluid was drained off both sides of her chest. She was treated aggressively but continued to deteriorate. Plant material, consistent with hay, was found in the fluid that was drained off the right side of her chest and the possibility of a rupture of the oesophagus was raised. Despite a grave prognosis, the mare was taken to surgery where a 6.35 cm tear was found in the oesophagus along with caudal muscular hypertrophy (increased thickness of the muscular layer of the oesophagus). The mare was humanely euthanized on the surgery table. Some of the conclusions reached by this group are as follows:

1. Spontaneous rupture of the intrathoracic oesophagus may be more common that we think.
2. Friesian horses have a higher frequency of oesophageal disease than non-Friesian breeds and caudal muscular hypertrophy was identified in 33% of Friesian horses compared to <1% of non-Friesians.
3. IMHO has been associated with spontaneous rupture of the oesophagus.
4. Horses with oesophageal disease may present with non-specific signs and this points out the need for more advanced diagnostics.
5. The mortality rate of those horses with intrathoracic oesophageal rupture is exceedingly high.

The authors conclusion: “While oesphageal disease aside from routine oesophageal obstruction is infrequently encountered in clinical practice, pleuropneumonia secondary to oesophageal perforation can present with nonspecific clinical signs and should be considered in cases of pleuropneumonia without an obvious underlying cause.”

Scientific Article: Hepworth-Warren, KL et. al. “Intrathoracic oesophageal perforation and secondary pleuropneumonia: Five cases” EVE June 2015, pp. 283-290.