History & signalment
'Indi' is a 2 y.o. FN Rhodesian Ridgeback who was previously healthy although she has a history of scavenging. She now presents with 12 hour history of acute-onset malaise, vomiting with bile multiple times, no diarrhoea but marked abdominal pain.
Physical examination findings
On physical examination she is quiet but alert and responsive. Rectal temperature is 39.1C. She has deep red oral mucous membranes which are slightly tacky and skin 'tenting'. Her abdomen is tense and difficult to palpate in detail.
Routine blood biochemistry and haematology are unremarkable.
Imaging examination findings
An abdominal ultrasound examination is performed -resulting in the following images:
Figure 1: Longitudinal view of the right cranial abdomen.
Figure 2: A loop of bowel, mid abdomen.
Figure 3: More bowel mid-abdomen.
Figure 4: Even more bowel, right side mid-abdomen.
Figure 5: Caudal Abdomen from ventral midline.
Figure 6: Transverse plane view of the duodenum and right lobe of pancreas.
Figure 7: Longitudinal plane view of the right cranio-dorsal abdomen showing the caudal vena cava (CVC) and right adrenal.
1: a) duodenum, jejunum, colon, ileo-caeco-colic junction
The descending duodenum is usually the largest segment of small intestine with the thickest wall and usually lies in a superficial position and immediately adjacent to the right kidney (as here).
This loop of jejunum has a somewhat dilated lumen but at 3mm the wall would be right at the top end of the normal range (2-3mm) for a canine colon (and since this loop is a bit dilated I would expect it to be thinner if anything). Whereas it is well within the normal range 2-5mm for jejunum.
By the same measure, figure 3 at 1.4mm really must be colon -with liquid contents in this case.
Figure 4 shows the ileo-caeco-colic junction with the ileum running in from the right of the picture and emptying into a fluid filled right colonon the left of the image. The ileum has a distinctively thick and prominent hyperechoic submucosal layer.
2) c) possible small intestinal obstruction and incipient diarrhoea
The main issue here is that the jejunum appears, subjectively, distended (this segment was fairly typical of the jejunum as a whole) but does this mean that there is an obstruction?
The best information on this comes from Sharma and others in Veterinary Radiology and Ultrasound May 2011 who found that jejunal diameter > 15mm (measured serosa-serosa) was a relatively specific marker for obstruction. Only 1/55 non-obstructed dogs in their series exceeded this limit.
So, a jejunal diameter of 15mm is exactly borderline! I think we have to say that small intestinal obstruction is a significant possibility. Obviously at the time of the examination the next step was to follow the dilated bowel to try to find an obstructed point further aboral -which was not apparent in this case.
The other relevant finding in Indi's case is the liquid colonic contents. This will almost inevitably manifest outwardly in due course as diarrhoea. I would regard this as fairly strong evidence in favour of gastroenteritis rather than obstruction.
3) a) a small effusion: perform ultrasound-guided abdominocentesis and cytology
One of the great advantages of ultrasonography is its unrivalled sensitivity in detecting effusions -and the fact that it facilitates ultrasound-guided centesis. This small pocket of hypoechoic free fluid is bounded ventrally by the abdominal wall and internally by mesentery and a loop of jejunum.
From this particular image there is not much more that can be concluded about its origin. In an acute abdomen like this we really need to know ASAP whether the fluid is haemorrhagic, exudate or transudate. And if exudate whether septic or not. If cytology confirms sepsis then exploratory surgery without delay is usually indicated. If bacteria are visible (invariably accompanied by neutrophilic exudate) then a diagnosis of septic peritonitis is proven. If no bacteria are visible then the next step is to measure fluid glucose levels and compare with blood glucose levels – effusion glucose more than1mmol/l lower than blood glucose is a reliable indicator of sepsis.
4) d) both pancreatitis and hypoadrenocorticism remain possible
I would describe the section of right pancreas seen here as having a slightly heterogeneous echotexture. However, changes associated with acute pancreatitis such as swelling, diffuse hypoechoic change, hyperechoic peri-pancreatic fat and subcapsular or interlobular oedema are absent. The sensitivity of ultrasonography in the diagnosis of pancreatitis is hard to quantify since we currently have no gold standard for the ante-mortem diagnosis of pancreatitis. However, it's certainly not 100%. Secondly, even if this particular piece of pancreas is relatively unremarkable it cannot be taken for granted that the remainder of the pancreas is similar. Localised acute pancreatitis is common.
This dog's right adrenal appears relatively slim in comparison to length. However, as a broad rule of thumb it has to be considered that long thin dogs have long thin adrenals and short round dogs have chubby adrenals! It is true that 'thin' adrenals (particularly <4mm) can be suggestive of hypoadrenocorticism -but there is a wide range of overlap between normal and Addisonian. An ACTH stimulation test is required to substantiate a diagnosis.