The ultrasonographic appearance of the gastrointestinal tract in normal and parvoviral infected puppies

Abstract

The normal sonographic appearance of the adult canine gastrointestinal tract has been well described. Interpretation of ultrasonographic findings in puppies presented for gastrointestinal evaluation is difficult due to the lack of information on normal ultrasonographic findings. The gastrointestinal tract, jejunal lymph node size and appearance as well as the presence or absence of peritoneal fluid were prospectively investigated in a group of 23 normal, 7 – 12 week old Beagle puppies. The duodenal wall thickness was significantly greater than other parts of the gastrointestinal tract (mean 3.8 mm). The mean stomach wall thickness was 2.7 mm, mean jejunal wall thickness 2.5 mm and mean colonic wall thickness 1.3 mm. In addition, the mean thickness of the duodenal mucosal layer (2.7 mm) was significantly thicker than that of the jejunal mucosal layer (1.5 mm). The mucosa was isoechoic to the muscularis layer and had a crisp luminal-mucosal interface in all puppies. There were no intestinal corrugations observed and wall layering was distinct in all gastrointestinal segments. The homogenous, hypoechoic jejunal lymph nodes were easily found and their mean thickness measured 7.1 mm (± SD 2.2 mm). A mild amount of anechoic free peritoneal fluid was seen in all puppies. Conclusions drawn from this study were that prominent jejunal lymph nodes and a mild amount of anechoic free peritoneal fluid can be considered normal findings in puppies. Information from the above study was utilised to interpret findings of a prospective clinical study on the ultrasonographic appearance of the gastrointestinal tract of puppies suffering from parvoviral enteritis. Forty puppies between six and 24 weeks of age were examined ultrasonographically within 24 hours of admission for canine parvoviral enteritis confirmed on faecal transmission electron microscopy. A clinical score (assessing habitus, appetite, vomiting, faecal consistency, mucous membranes, abdominal palpation and borborygmi) was attributed to each puppy prior to the ultrasonographic examination. Sonographic findings included fluid filled small intestines in 92.5% of cases, and stomach and colon in 80% and 62.5% of cases respectively. Generalised atony was seen in 30 cases and weak peristaltic contractions indicative of functional ileus observed in the remaining 10 cases. The duodenal and jejunal mucosal layer thicknesses were significantly reduced when compared to values obtained in the normal Beagle puppies with mean duodenal mucosal layer measuring 1.7 mm and jejunal mucosal layer 1.0 mm. Additionally, a mucosal layer with diffuse hyperechoic speckles was seen in the duodenum (15% of cases) and the jejunum (50% of cases). The luminal surface of the duodenal mucosa was irregular in 22.5% of cases and the jejunal mucosa in 42.5% of cases. In all of these puppies, changes were accompanied by generalised indistinct wall layering. Small intestinal corrugations were seen within the duodenum in 35% of cases and within the jejunum in 7.5%. A mild amount of anechoic free peritoneal fluid was observed in 26 cases and was considered within normal limits for puppies and a moderate amount of anechoic free peritoneal fluid was observed in six cases. The jejunal lymph node size was within normal limits for puppies and thus parvoviral enteritis does not appear to be associated with ultrasonographic evidence of regional lymphadenopathy. There was a tendency for animals with the most dramatic ultrasonographic changes to be in poor condition clinically i.e. they had a low clinical score. Each of the above described changes cannot be considered pathognomonic for canine parvoviral enteritis but in combination, are suggestive of the disease. It is hoped that information from this study may alert the clinician as to the possibility of underlying parvoviral enteritis in puppies presented for abdominal ultrasound for investigation of gastrointestinal disease. Further studies are needed to document the ultrasonographic appearance of other paediatric gastrointestinal diseases such as severe verminosis, giardiasis, coccidiosis and distemper etc. before further conclusions can be drawn from this study. Daily ultrasonographic examinations of puppies suffering from canine parvoviral enteritis are needed to further understand the progression of this disease over time as well as the possible ultrasonographic indicators of clinical improvement or deterioration.