Development of reference intervals for the large intestinal transit of radiopaque markers in dogs

Ten healthy dogs were fed 30 1.5 mm and 10 5 mm radiopaque markers (BIPS, M edID, Grand Rapids) mixed with sufficient quantities of a high fibre diet t o meet 25% of their estimated daily caloric requirements, Abdominal radiogr aphs were made at two hour intervals until 90% of the small and large marke rs had left the colon, The mean residence times (MRT) of each size of marke r in the proximal, distal and total colon were calculated using kinetic ana lysis. The MRT's of the small markers were 4.9 hours (SD 4.4), 7.1 hours (S D 3.3) and 12.0 hours (SD 7.1) respectively. The MRT's of the large markers were not significantly different from the small markers except in the prox imal colon where they were significantly shorter (3.2 hours, SD 2.3). Refer ence colonic filling and colonic transit curves for both sizes of markers w ere constructed. These may be useful to detect abnormal colonic transit in dogs.