What's wrong with this dog, that escaped from home?

So it can be helpful when presented with a fair amount of information to boil things down to a simplified problem list:

• lethargy, depression
• paraparesis (and possibly proprioceptive deficits all four limbs)
• tachycardia and hypotension that responded to IVFT bolusing
• mucous membrane pallor
• pain on hip extension
• pain on abdominal palpation with possible fluid thrill

We might make an educated guess that he's experienced unwitnessed trauma, ingested something or coincidentally become unwell for another reason (maybe this being less likely?). His response to initial treatment might also be considered partly diagnostic, as well as having provided therapeutic benefit. 

So as not to be daunting, why not just suggest one clinical pathological test and one diagnostic imaging assessment that you feel would be MOST appropriate for Trev.

Thank you for the case;

The response to a fluid bolus suggests a degree of hypovolaemia, whether this is haemorrhage , fluid loss or third space loss remains open currently. 

The neurological signs are what stand out to me as being a little unusual but I suppose could also be attributed to trauma or toxin ingestion, in line with our educated guesses. 

If limited to one clinical pathological test I would perform an EPOC- to check for electrolyte imbalances (which could be causing some of the ataxia) and also get an idea of PCV due to the possibility of haemorrhage (although, if very acute and given suspected hypovolaemia this may not be ideal in the absence of total solids).
This would also provide urea/creatinine which would be useful to assess for hypovolaemia (if prerenal azotaemia). Given the possibility of trauma, if azotaemia is present and peritoneal effusion is confirmed, this may be important in case of uroabdomen.

Alternatively- Biochemistry, haematology, electrolytes and a manual PCV could be performed for a more complete picture and would be my preference.

An initial imaging assessment at the time of triage would be an AFAST to establish if the fluid thrill is true, and if free fluid is present I would then perform abdominocentesis with fluid analysis and cytology to try to ascertain the source of peritoneal effusion.

Thanks for your well reasoned thoughts!

I think your suggestion that this may represent hypovolaemia is likely given the response to fluid challenge (especially given that the BP was low and then improved with IVFT, rather than it simply being response to pain relief which might be more likely to show a reduction in HR and either a lowering of high BP, or no change in BP). 

AFAST is a great option for rapid abdominal assessment where there may be fluid in the abdomen (even I can do it!) and then taking an appropriate sample and testing it is definitely the best option rather than just assuming what the fluid might be based on simply appearance alone. In this case

- the dog had a serum urea of 12mmol/L and creatinine of 100mcmol/L 

- a circulating PCV of 35% and TS of 45g/dL

- AFAST confirmed free abdominal fluid; cytology showed there were RBC present in the fluid. The fluid had a PCV of 10% and TS of 12g/dL. The fluid also had creatinine of 48mmol/L and potassium of 9mmol/L.

What does anyone think this means?

Out of the following options, what is your preferred course of action?:

a) Perform an exploratory coeliotomy

b) Perform orthogonal view abdominal and thoracic radiographs

c) Perform retrograde positive contrast urethrocystography

d) Conservative management with analgesia and close monitoring

Whilst the abdominal fluid has a PCV of 10%, which would give it the appearance of blood, the considerably higher creatinine and potassium of the abdominal fluid compared with serum mean that it is urine. There is no point comparing the serum urea to fluid urea because the smaller molecule moves too readily across the peritoneum to allow a differential gradient to be simply recognised. Bloody urine in the abdominal cavity is consistent with a traumatic uroabdomen.

Urine can leak from the renal pelvis, ureters, urinary bladder and proximal urethra. The terminal intrapelvic urethra (and further distal) are extra abdominal and shouldn't cause peritoneal effusion. They can cause marked bruising and, more chronically, skin sloughing. To determine the location of the leak, retrograde positive contrast urethrocystography is a simple and accurate test if performed properly. Images are obtained whilst contrast is instilled at the penis; it is a dynamic study and instilling contrast followed by a pause before taking the radiograph can introduce artefact or fail to properly dilate the lower urinary tract.

This dog had bilateral sacroiliac luxurious, accounting for the musculoskeletal signs. He responded to treatment for pain and hypovolaemia. He had a traumatic bladder rupture that was repaired primarily once he was stable for anaesthesia.