Test Detail
Congenital idiopathic megaesophagus (CIM) — German Shepherd
Neurological · Dog
Generalized dilation of the esophagus of congenital origin, without an identifiable obstructive or neuromuscular cause, that produces regurgitation from weaning. In the German Shepherd, a familial aggregation with a genetic basis is recognized. Studies from 2022 identified an association with a 33-bp VNTR in intron 1 of MCHR2 rather than a closed causal mechanism; the trait is also sex-differentiated and its expression is influenced by additional factors not yet fully characterized.
Incidence
Affected breed: German Shepherd. CIM is described with familial aggregation in the breed; no reliable figures for population incidence or carrier frequency in large series have been published.
Breeder management
- In the face of a confirmed case in a litter, do not repeat the parental mating
- Avoid breeding affected animals or those with a close family history of CIM
- Consider the genetic risk test (MCHR2 VNTR) in affected lines to assess the mating, if available at the laboratory
- Do not mechanically exclude a carrier of the risk allele without weighing the rest of the health and pedigree context
- Communicate the history and management measures (elevated feeding, food as a slurry) to the buyer of offspring from affected lines
- Avoid breeding affected animals or those with a close family history of CIM
- Consider the genetic risk test (MCHR2 VNTR) in affected lines to assess the mating, if available at the laboratory
- Do not mechanically exclude a carrier of the risk allele without weighing the rest of the health and pedigree context
- Communicate the history and management measures (elevated feeding, food as a slurry) to the buyer of offspring from affected lines
Specialist notes
Differential diagnosis with acquired megaesophagus (myasthenia gravis, hypoadrenocorticism, peripheral neuropathies, myopathies, vascular esophageal obstruction), with persistent right aortic arch (vascular ring anomaly) in the puppy and with other congenital disorders. The esophagogram/fluoroscopy and the esophageal motility study are key. Management is based on elevated feeding in small meals of slurry texture; the prognosis is variable, with partial improvement on maturing in some cases. Aspiration pneumonia is the main cause of mortality. The validity of the MCHR2 test outside the German Shepherd (e.g., in the Berger Blanc Suisse) is questioned (PMID: 40626856).
References
1. Bell SM, Evans JM, Evans KM, Tsai KL, Noorai RE, Famula TR, Holle DM, Clark LA. Congenital idiopathic megaesophagus in the German shepherd dog is a sex-differentiated trait and is associated with an intronic variable number tandem repeat in Melanin-Concentrating Hormone Receptor 2. PLoS Genet 18(3):e1010044, 2022. PMID: 35271580
2. OMIA:002716-9615. Megaoesophagus, MCHR2-related in Canis lupus familiaris. https://omia.org/OMIA002716/9615/
3. Kehl A, Schelling C. [Is the megaesophagus test valid for White Swiss Shepherds (Berger Blanc Suisse)?]. Schweiz Arch Tierheilkd 2025. PMID: 40626856
2. OMIA:002716-9615. Megaoesophagus, MCHR2-related in Canis lupus familiaris. https://omia.org/OMIA002716/9615/
3. Kehl A, Schelling C. [Is the megaesophagus test valid for White Swiss Shepherds (Berger Blanc Suisse)?]. Schweiz Arch Tierheilkd 2025. PMID: 40626856