Heterotopy (“Error loci”) of the spiral loop of the ascending colon in cattle

Objectives: To describe a dysmorphological condition in which the spiral loops of the ascending colon (SLAC) do not form an orderly spiraling mass adjacent to the left side of the mesojejunum. Methods: The study started from the observation of repeated occurrence of intraoperatory and post mortem findings of morphological distortions of the SLAC. Further investigations were carried out on slaughtered veal calves. The specific configuration of the SLAC was classified as following on the basis of the space between loops and their abnormal superimposition as well as loss of the disc shape configuration: 1) normal anatomical situation: the centripetal and the centrifugal coil of the SLAC are intimately attached to the left side of the mesojejunum and the loops are ordenlty distended without any overlapping among adjacent loops; 2) conical shape looseness of the SLAC: the spiral loops are loosly attached to the mesojejunum, and if raised at the level of the central flexure they assume a tri-dimensional flaccid conical shape. Some loops can overlap adjacent one; 3) partial dystopia of the SLAC: intestinal segments of the SLAC are apart from each other with an elongated mesocolon; 4) complete ectopia of the SLAC: in this case the SLAC is completely detached from the mesojejunum. Results: The intraoperatory and post mortem findings of morphological distortions of the SLAC were often observed in animals affected by intestinal mechanical obstructive diseases, such as volvulus, torsion and intussusception. Therefore, it was hypothesized that the abnormal position of the SLAC might have constituted the predisposing factor for the observed intestinal obstructive or ileus condition. The investigation carried out at slaughterhouse included 1,113 clinically healthy slaughtered veal calves. A normal configuration, as expected according to the veterinary anatomical literature, was observed in 641 (57.6± 2.9%) out of the 1,113 calves. A conical shape looseness of the SLAC was found in 381 out of 1113 (34.2±2.8%). Partial dystopia of the SLAC was noted in 68 out of 1,113 cases (6.1±1.4%), whereas a complete ectopia was present in 23 out of 1,113 calves (2.1±0.8%). In the latter cases the SLAC was “dislocated” from its position in the middle of the mesojejunum, just as though it were an independent anatomical structure. Conclusions: This study clearly indicates that the heterotopy of the SLAC represents a relatively common anatomical anomaly also in clinically healthy animals. In fact, 42.4% of the SLAC examined in this study had significant anatomical divergence from what is normally described in reference textbooks. The observation of this kind of anomalies in animals affected by intestinal mechanical obstructive diseases prompts to consider those anomalies as potential predisposing factor for intestinal obstructive or ileus condition. The predisposition might be based on an impairment of the intestinal centre of gravity, and the consequently reduced capacity of the intestine, or tracts of it, of maintaining its correct anatomical position when subjected to stresses causing abnormal movements of the intestinal mass. The heterotopy of the SLAC resembles a developmental abnormality described in human medicine called “intestinal malrotation or nonrotation.