Tuesday, April 6, 2010

14. High BUN and creatine in a vomiting adult dog

April 7, 2010. Perth, 6 am. Writing from a Willeton house in Perth as I reflected on this "medical malpractice" case.

Vet 1 diagnosed kidney failure. The adult neutered male dog of a small breed, around 5 years had been vomiting for the past few days and occasionally over the years. Vet 1's blood test some 9 months ago showed a high BUN. So she advised another blood test. It showed high BUN and an extremely high creatine level. She suspected acute kidney failure and advised abdominal scanning at two other practices as she does not have the facility. Antibiotics were prescribed for the "skin disease" according to the owner.

Vet 2 (myself) advised monitoring. The worried owner phoned me wanting to fax me the blood tests and get a telephone diagnosis. I asked her to bring the dog down for an examination as blood test results need to be co-related with the history and physical examination of the dog.

She got the dog in for examination. She showed me the blood tests and asked whether her dog was dying soon. The dog was normal and had no polydipsia or polyuria. Therefore, I did not "run down" the other vet. I did not ask for another blood test to verify as it was taken 24 hours ago. I presumed that the owner would not want one as most owners of small breeds feel the pain of their dogs having their small vein punctured for blood taking. In any case, most vets in Singapore, including me, trusted the blood test results of our competitors and seldom asked for another test. This was a big mistake on my part.

As the dog was active and normal, except for vomiting, I said it was not dying soon. It could be having gastritis (stomach infection). I advised taking of the antibiotics I prescribed for 5 days. The important thing was to monitoring the water intake daily and to keep in touch by phone if vomiting persisted and the dog did not eat. I advised a prescription canned food for kidney disease. The owner phoned me the next day that the dog ate the canned food. However, it vomited after eating the canned food some 24 hours later.

Vet 3 diagnosed no kidney problems. The owner went to Vet 3 to get a scan. Vet 3 did a blood test and warded the dog which was given an IV drip. "It is a medical malpractice," the owner phoned me. "Vet 1 said that her blood test machine had broken down and did not even have the decency to phone me earlier." There was much anger. There was a meeting with Vet 1. Vet 1's mentor told the owner that I ought to have taken a blood test. Since I had not done it, I was also involved in "misdiagnosis".

Conclusion:
I should have taken a blood test and recommended a scan immediately. There was no point trying to save money for the owner. Practising defensive medicine would have been prudent on hindsight. I apologised for not having asked her to take a blood test. She said she would have objected anyway. I offered to take back the cans prescription renal diet.

"Well, Vet 3 says that the dog should be on a prescription liver diet!". The dog was no more vomiting. What was the diagnosis? Liver problems now? This case shows that the vet must get another blood test done and if the owner objects, to put it in writing. If the physical findings do not indicate kidney failure, be assertive and run down the competitor. No quarters given. However, running down the competitor just adversely affect the image of the veterinary profession in Singapore. I don't do it. Every vet will make mistakes and so I don't run down my competitors. I hope the 4th year vet students in Murdoch University will find this case alive and interesting for their "Polydipsia and Polyuria" lectures, well documented by Dr Peter Irwin,

1. Normal dogs drink about 50-60 ml/kg/day. Cats considerably less. I did ask the owner to monitor the water intake. Instead she syringe feed water to the dog. This may be one cause of "vomiting" after eating the canned food.

2. Polydipsia: >100ml/kg/day in dogs. >50ml/kg/day in cats on DRY food and >10ml/kg/day in cats on WET food.

3. Polyuria: increase in urine production >50ml/kg/day. general guide only. not possible to measure in clinic or home setting.

4. Urine Specific Gravity (USG) to assess renal concentrating ability. Measured on a refractometer (urine dipstick results unreliable).

No such thing as a "normal" USG. Most healthy animals USG 1.025 to 1.065. A sample with <1.025 may raise a diagnostic suspicion of polydipsia.

4.1 Hypersthenuria USG>1.012. Urine more concentrated than the patient's plasma
4.2 Isothenuria USG 1.008 - 1.012. Persistent isothenuria with azotaemia is consistent with tubular insufficiency or renal failure.
4.3 Hyposthenuria USG <1.008. Renal tubules can dilute but not concentrate urine. Unlikely to have renal failure or insufficiency. Usually caused by interference with the ADH receptors in the renal collecting ducts.

DDx of PU and PD in dogs and cats
COMMON CAUSES
DOGS
Chronic renal disease
pyometra
diabetes mellitus
hyperadrenocorticism
Iatrogenic (drug induced)
Medullary solute washout - a process as a consequence of marked polyuria of ANY CAUSE and can contribute to the severrity of the PU. E.g. relief of Urinary tract obstruction in FLUTD cat.

CATS
Chronic renal disease
Post-obstructive diuresis
Hyperthyroidism
Diabetes melllitus
Iatrogenic
Medullary solute washout


P.S. It is best to advocate ultra-scan of the kidneys to check for polycystic kidneys or tumours and not to ask the owner to wait a few days. In the above case, the owner said that Vet 1 should have made the necessary arrangements as she was told to wait 2 weeks at one practice. She managed to find one vet who did the scan.

LESSONS LEARNT FROM THIS CASE
1. PROVIDING EXCELLENT CUSTOMER SERVICES
The vet can make arrangements for scanning at other practices since he has none. The dog owner wants scanning and therefore, this service should create goodwill and loyalty if the vet does it. As for me, I did not advise immediate scanning as my clinical findings did not indicate acute renal failure and like vets from my baby-boomer generation, I was trying to lower the owner's total veterinary costs. I should make arrangements for scanning as that was what the owner wanted. In fact, she had the impression that I said scanning was unnecessary, according to Vet 1's mentor when I spoke to him to discuss the resoluion of the owner's conflicts in this case.

2. MINI-PROFILES NOT ADVISED
Always collect URINE and blood for health screening. This is because the vet cannot assess the dog's metabolic state without both samples. In this case, Vet 1 did a mini-profile to check only blood BUN and creatinine. The owner told me that the BUN was high but creatinine was normal some 9 months ago and the vet advised a mini-profile to check BUN and creatinine. The BUN has gone higher and the creatinine level was extremely high in the second mini-profile test.

FULL PROFILE means CBC (complete blood count) and FBE (full biochemical exam) AND elecrolytes (Na, Cl & K). Many Singapore pet owners will not want to pay for the full profile and so, permission must be given first. Otherwise, the owner may not pay!

3. HONESTY
The owner complained that Vet 1 should have had informed her when the vet knew that the blood test machine was malfunctioning instead of after she told them that Vet 3 had said that there was no kidney disorders from Vet 3's blood test. She had to take leave from work and suffered stresses. "Why didn't Vet 1 inform me earlier?" she said. "It is medical malpractice!"

4. REPEAT BLOOD SAMPLE.
I should have strongly advise a blood sample plus a urine sample when clinical findings did not indicate an acute renal failure. This was what the owner had the impression from Vet 1 and was worrying a lot. I was trying to save the owner some money. Younger vets in Singapore do not think twice about blood tests, X-rays, urine tests and histopathology (even for a hamster tumour). Times have changed and the Singapore pet owner must pay more for vet treatment.

5. POLYDIPSIA AND POLYURIA
Many Singapore dog owners know that their dogs drink a lot but don't know how much. The dog may not be polydipsic. Check Urine SG with a refractometer. A sample with less than 1.025 may indicate polydipsia.

6. ACUTE RENAL FAILURE
is characterised by the sudden onset of oliguria/anuria, azotaemia or both.
6.1 Clinical Signs are: extreme lethargy (the dog was active in this case study), dehydration, oliguria or anuria and vomiting.
6.2 Lab findings include: renal azotaemia (very high increase in BUN and creatinine) with isothenuria. Urea >50mmol/L. creatinine >300mmol/L.
6.2.1 Urine analysis may show cause e.g. oxalate crystals, white cell cass, bacteriuria in acute pyelonephritis).
6.3 Electrolyte abnormalities (Na, K, Cl variable)
6.4 Metabolic acidosis
6.5 Hyperphospataemia

I hope this case study will be useful as they show the owner's points of view. In this case, assuming that the blood test machine was not "malfunctioning", it is possible that the vomiting dog had a bacterial infection of the kidneys resulting in a renal azotaemia (acute renal falure). With antibiotics, the dog took a few days to recover. When Vet 3 was consulted, there was no more bacterial infections (e.g. pyelonephritis) and therefore no more renal azotaemia. Acute renal failure at the beginning stage may just show azotaemia and not oliguria/anuria. So Vet 3 became the hero. A urine test by Vet 1 would have been very useful to support bacterial infection in the urinary tract, e.g. proteinuria, white cell casts, USG, pH, presence of uroliths but the owner might not want to pay initially and this is a common situation in Singapore in this period of recession.

CONCLUSION
4th year vet students who must study a lot of theories and memorise them to pass examinations can see that the complexities and and economics of practice are so much different from the class-room lectures.

Mini-profile blood tests rather than complete blood count and biochemistry may be done in practice as the owner may not want to pay for a comprehensive blood test. Do NOT assume that the owner would not want a repeat blood test. Get a second blood test done rather than try to save money for the owner and be liable for "medical malpractice" litigation. Get the owner's objection recorded if the owner does not want a second blood test.

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