Intestinal pseudo-obstruction in a dog

These are biopsy specimens taken at exploratory laparotomy from a thin-walled, distended small intestine in 6-year-old female Border Collie with ileus.

Fig 1. In the full-thickness sections of small intestine there is marked thinning/atrophy of the circular and longitudinal layers of the tunica muscularis (oval outline) associated with an inflammatory infiltrate (H&E x20).
Fig 2. Atrophied bundles of smooth muscle (oval outline) are all that remain of the tunica muscularis (H&E x200).
Fig 3. There is a moderate infiltrate of small lymphocytes and plasma cells at the level of the tunica muscularis (H&E x400).

Final Diagnosis

Lymphoplasmacytic intestinal leiomyositis associated with marked atrophy and loss of the tunica muscularis


The histopathology in this case is consistent with so-called 'intestinal pseudo-obstruction', a rare disease that typically presents with ileus in the absence of mechanical/physical obstruction. Affected intestine is typically distended and thin-walled. It is possible that other organs containing smooth muscle may be affected (e.g. urinary bladder). The cause of the disease in dogs is not known but in human patients, the disease is thought to be due to a primary autoimmune disease process.