PUPD – A Case Study

Dr Jessica Adamany

VVS Small Animal Internal Medicine Specialist

VVS Internal Medicine Specialist Dr Jessica Adamany brings you an interesting and thought-provoking case study. Read about Ruby, who first presented to her primary vets with polyuria and polydipsia (PUPD).

This is “Ruby”, a 9-year-old, female-neutered, Jack Russel Terrier Cross who underwent a live guided abdominal ultrasound with internal medicine support on the 3rd October 2024.

Ruby initially presented to her primary veterinarian in January 2024 for halitosis and increased thirst and urination. Her owners had previously quantified her water intake which was approximately 900 mL/ 24 hours or 112 mL/kg/ 24 hours; compatible with polyuria and polydipsia (PUPD). Ruby was reported to be otherwise well in herself. Her physical examination was unremarkable aside from a loose 206 and mild gingivitis. A dental procedure was scheduled and pre-anaesthetic laboratory work consisting of a haematology, serum biochemistry, thyroid panel, and a urinalysis was collected.

Ruby’s laboratory work was unremarkable aside moderate elevations in her liver enzymes, shown below.

Test	Result	Ref Interval
ALT	1000U/L	19.8-124
ALP	800U/L	0-130
GGT	46.7U/L	0-10

Urinalysis revealed a urine specific gravity (USG) of 1.016 with 3+ proteinuria. The remainder of the urinalysis was unremarkable. A UPCR was not performed at that time.

At this time Ruby’s problem list included:

• Periodontal disease
• PUPD
• Raised liver parameters
• Suspected proteinuria

Differential diagnoses considered for Ruby’s polyuria and polydipsia included:

• Osmotic diuresis
  • Chronic renal failure
• Central diabetes insipidus
• Secondary nephrogenic diabetes insipidus
  • Hepatic insufficiency
  • Hyperadrenocorticism
  • Hyperthyroidism (rare in dogs)
  • Ionised hypercalcaemia
• Psychogenic polydipsia

Differentials considered for the ALT elevation included:

• Hepatopathy
  • Primary
    • Inflammatory
    • Neoplastic (primary or metastatic)
    • Infectious
    • Toxic
  • Secondary
    • Metabolic (Hyperadrenocorticism)
    • Reactive hepatitis from inflammation within the portal system
    • Hypoxia

Differentials considered for the ALP elevation included:

• Hepatobiliary disease/ Intra and extrahepatic cholestasis
  • Inflammatory
  • Infectious
  • Neoplastic
  • Metabolic
  • Toxicity
• Hyperadrenocorticism (vacuolar hepatopathy and corticosteroid induction)
• Bone destruction or increased osteoclastic activity

Given Ruby’s signalment, history and laboratory work, numerous causes of polyuria and polydipsia could be excluded such as diabetes mellitus, primary glucosuria, electrolyte disturbances, pyometra, septicaemia, primary nephrogenic diabetes insipidus, etc. Although chronic renal disease (IRIS stage 1), some causes of secondary nephrogenic diabetes insipidus (see above), central diabetes insipidus, and psychogenic polydipsia could not be excluded at this stage, given the combination of raised liver parameters and increased thirst and urination, hepatic dysfunction and hyperadrenocorticism were considered likely differentials requiring further investigation.

ALT (alanine aminotransferase) is an enzyme predominantly located within the hepatocytes and is indicative of hepatocellular damage. Ruby’s ALT was markedly elevated with a 10-fold increase. This is a significant abnormality that required further investigation and monitoring for an underlying primary or secondary hepatopathy.

ALP (alkaline phosphatase) has three isoenzymes: liver-ALP, corticosteroid-ALP, and bone- ALP. The liver- ALP isoenzyme is elevated in cases of hepatobiliary disease, mainly intrahepatic or extrahepatic biliary disease/ cholestasis. The corticosteroid- ALP isoenzyme is elevated by endogenous and exogenous glucocorticoids while the bone- ALP isoenzyme is elevated with growth and osteolytic diseases. Given the concurrent marked elevation of Ruby’s ALT, a significant hepatocellular disease (primary or concurrent) was considered likely, however, hyperadrenocorticism can cause some degree of hepatocellular damage due to vacuolar hepatopathy and therefore this disease was still considered.

To investigate further, an ACTH simulation test was performed followed by a sedated abdominal ultrasound. The ACTH stimulation test was not consistent with hyperadrenocorticism with a basal cortisol of 85 nmol/L and a post ACTH cortisol of 450 nmol/L. Abdominal ultrasound was largely unremarkable aside from a small amount of sludge within the gallbladder and subjectively enlarged, hyperechoic liver. Unfortunately, the adrenal glands were not identified. The remainder of the abdominal ultrasound was unremarkable. Fine needle aspiration of the liver was performed and cytology did not reveal any neoplastic cells or inflammation, however, approximately half of the hepatocytes contained mild indiscreet vacuolation.

_{Ultrasound image identifying a mildly hyperechoic liver and a normal gallbladder with a small amount of echogenic debris.}

As Ruby was otherwise well in herself, she was discharged on Denamarin and ursodeoxycholic acid with the plan to review her liver enzymes in 4 weeks. It was requested that the owner collect numerous first morning urine samples to assess the USG on multiple samples and to submit for a urine protein to creatine ratio (UPCR). The owner was made aware that further investigations such as liver biopsy would be required if the liver enzymes were persistently elevated.

Over the course of the next 4 weeks Ruby became significantly more polyuric and polydipsic and developed polyphagia with noticeable weight pain. Clinical examination revealed persistent gingivitis, hepatomegaly and a potbellied appearance. Haematology and serum biochemistry revealed further elevation in her liver enzymes (see below).

Test	Result	Ref Interval
ALT	1366U/L	19.8-124
ALP	824U/L	0-130
GGT	191.0U/L	0-10

Although this pattern was consistently more suggestive of a hepatocellular disease, given Ruby’s clinical signs and physical examination a low dose dexamethasone suppression test (LDDST) was performed before proceeding with repeat abdominal imaging and potential liver biopsies. The LDDST results are shown below.

Test	Result	Ref Interval
Cortisol – Baseline	146.0 nmol/L	25-125
Cortisol – 4 hr Post Dex	139 nmol/L
Cortisol – 8 hr Post Dex	163 nmol/L	<40

Based on this low dose dexamethasone suppression test (LDDST) and compatible clinical signs, Ruby was diagnosed with hyperadrenocorticism as the 8-hour post dexamethasone cortisol concentration was > 40 nmol/L. She was started on trilostane 1.5 mg/kg by mouth once daily.

Within 3 weeks Ruby’s clinical signs had improved, and her liver enzymes had decreased by > 50%, however, her pre-vetoryl cortisol was elevated at 165 nmol/L. As her pre-vetoryl cortisol was elevated and she had persistent clinical signs including mild PUPD and polyphagia, her trilostane dose was increased by 50% based on the Dechra flow sheet on the use of pre-vetoryl cortisol¹.

Ruby remained well for approximately two months, but then represented for evaluation of a progressively distended abdomen, mild recurrence of PUPD, and not being quite her “normal” self. Laboratory work revealed normalisation of her liver enzymes and a pre-vetoryl cortisol within normal limits. Ruby was subsequently booked in for a VVS live guided ultrasound with associated internal medicine support on 3 October.

On abdominal imaging, the most significant finding was an enlarged right adrenal measuring 32 mm x 26 mm with no obvious invasion of the surrounding vasculature. The left adrenal gland was not visualised. The liver was persistently subjectively enlarged and hyperechoic and there was sludge within the gallbladder.

_{Ultrasound image of the right adrenal mass which was identified during the live-guided VVS ultrasound.} 

Ruby’s plan following her VVS live-guided abdominal ultrasound:

The presence of an adrenal mass in conjunction with a lack of suppression on the LDDST is most consistent with a glucocorticoid secreting adrenocortical tumour. However, as we were unable to identify the contralateral adrenal gland to assess for atrophy which would have provided further support for a glucocorticoid secreting adrenocortical tumour, assessment of the urine or plasma catecholamine metabolites (i.e. metanephrine and normetanephrine), to ensure that there was not concurrent production of catecholamines from the adrenal medulla was advised^2,3,4. It was recommended that if this was performed on urine, that a sample be collected 7 days after the current visit to limit any effect of stress during hospitalisation⁵. With the reported recurrence of mild PUPD despite a normal pre-vetoryl cortisol, resolution of polyphagia, and normalisation of the liver enzymes, Ruby’s blood pressure was assessed as hypertension is a sequela noted in 31%-86% of dogs with hyperadrenocorticism⁶ and approximately 50% of dogs with pheochromocytomas⁷. The ionised calcium was also measured to ensure that a paraneoplastic elevation of this electrolyte was not the cause her recurrent PUPD. A urine sample was collected for assessment of the UPCR as it is reported to be elevated in 50% of dogs with hyperadrenocorticism and often requires management⁶.

Ruby’s urine catecholamine metabolites were not suggestive of a pheochromocytoma and her ionised calcium was normal. Therefore, Ruby’s final diagnosis was adrenal dependent hyperadrenocorticism. Although studies show that dogs with adrenocortical tumours can have a median survival time approximately 12 months with trilostane therapy⁸, adrenalectomy is the recommended treatment.

Ruby had her adrenalectomy on 1st November and we are happy to report that she is currently doing very well!

Take home messages from this case:

1. Liver enzyme pattern in hyperadrenocorticism: Elevation of the ALP has been documented to be elevated in over 80-90% of dogs with hyperadrenocorticism. This is due to increased synthesis of the corticosteroid-induced ALP isoenzyme and intrahepatic cholestasis secondary to vacuolar hepatopathy. Increases in ALT are also commonly documented; however, this elevation is often mild when compared to the ALP concentration⁹. In Ruby’s case, the ALT was markedly elevated initially raising the suspicion of a significant hepatocellular disease rather than hyperadrenocorticism alone. Although this type of pattern is less common in dogs only suffering with hyperadrenocorticism, testing for hyperadrenocorticism should still be considered in dogs with this type of liver enzyme pattern, especially in the face of appropriate clinical signs.

2. ACTH stimulation test vs LDDST: As with any test, all available diagnostic tests used in dogs suspected to have hyperadrenocorticism have their limitations, with none of the available tests having a 100% sensitivity or specificity. Although the ACTH stimulation test is easier to run and is reported to be less affected by stress and/or non-adrenal illness with a specificity of 59-93%, the test’s overall sensitivity ranges from 57-95%, and this sensitivity drops substantially to 57-63% in cases of adrenal dependent hyperadrenocorticism¹⁰. In Ruby’s case, this was likely the cause of the false negative result obtained with the ACTH stimulation test.

Currently, many internal medicine specialists consider the LDDST to be the preferred diagnostic test for hyperadrenocorticism in dogs with appropriate clinical signs¹¹. Although this test may be more likely to give a false positive result in cases with stress or non-adrenal illness (specificity 44-73%), it has a much higher sensitivity than the ACTH stimulation test ranging from 85-100%¹². In addition, the LDDST test may allow discrimination between PDH and ADH.

3. The importance of discriminating tests: Once a diagnosis of hyperadrenocorticism is made, steps to differentiate between adrenal and pituitary dependent hyperadrenocorticism is necessary as the origin of disease may alter the recommended treatment and prognosis for the patient. In certain cases, the LDDST can also be used to differentiate between adrenal dependent and pituitary dependent hyperadrenocorticism, however, in Ruby’s case there was a complete lack of suppression which is described as having a 4- and 8-hour cortisol > 40 nmol/L and > 50% of the baseline cortisol. With this result, it was not possible to determine if Ruby’s hyperadrenocorticism was adrenal or pituitary and therefore a differentiating test such as an abdominal ultrasound, endogenous ACTH measurement, or a high dose dexamethasone suppression test was required. Tumour size and presence of local or distant metastasis negatively affect the survival in dogs with adrenal tumours and therefore early diagnosis is advisable¹³.

If you would like to collaborate with VVS on live-guided abdominal ultrasound cases with internal medicine support, get in touch to find out how you can offer this service in your clinic.

Endocrine cases can be challenging to manage in house, If you would like to discuss a clinical case with Dr Jessica Adamany or any of the VVS Internal Medicine team click the link below or email the VVS team at [email protected].

References / further reading

1. https://www.dechra.co.uk/Files/Files/SupportMaterialDownloads/UK/DVP1412-Vetoryl-PVC-Flowchart-UK.pdf

2. Gostelow R, Bridger N, Syme HM. Plasma-free metanephrine and free normetanephrine measurements for the diagnosis of pheochromocytoma in dogs. J Vet Intern Med. 2013; 27(1):83-90.

3. Salesov E Boretti FS, Sieber-Ruckstuhl NS, Rentsch KM, Riond B, Hofmann-Lehmann R. Kircher PR, Grouzmann E, Reusch CE. Urinary and plasma catecholamines and metanephrines in dogs with pheochromocytoma, hypercortisolism, non-adrenal disease and in healthy dogs. J Vet Intern Med. 2015; 29(2):597-602.

4. Van den Berg MF, Kooistra HS, Grinwis GCM, Van Nimwegen A, Van Faassen M, Kema IP, Teske E, Galac S. Reference intervals for plasma, urinary, and salivary concentrations of free metanephrines in dogs: Relevance to the diagnosis of pheochromocytoma. J Vet Intern Med. 2023; 37(1):173-193.

5. Kook PH, Boretti FS, Hersberger M, Glaus TM, Reusch CE. Urinary Catecholamine and metanephrine to creatinine ratios in healthy dogs at home and in a hospital environment in 2 dogs with pheochrocytoma. J Vet Intern Med. 2007; 21(3):388-393.

6. Behrend EN, “Canine Hyperadrenocorticism”. Canine and Feline Endocrinology, Feldman EC, Nelson RW, Reusch CE, Scott-Moncrieff CR, Behrend EN, Elsevier Inc, 2015, pg. 398.

7. Reusch CE, “Pheochromocytoma and Multiple Endocrine Neoplasia. Canine and Feline Endocrinology, Feldman EC, Nelson RW, Reusch CE, Scott-Moncrieff CR, Behrend EN, Elsevier Inc, 2015, pg. 531.

8. Helm JR, McLauchlan G, Boden LA, Frowde PE, Collings AJ, Tebb AJ, Elwood CM, Herrtage ME, Parkin TDH, Ramsey IK. A comparisons of factors that influence survival in dogs with adrenal- dependent hyperadrenocorticism treated with mitotane or trilostane. J Vet Intern Med. 2011; 25(2):251-260.

9. Behrend EN, “Canine Hyperadrenocorticism”. Canine and Feline Endocrinology, Feldman EC, Nelson RW, Reusch CE, Scott-Moncrieff CR, Behrend EN, Elsevier Inc, 2015, pg. 396.

10. Behrend EN, “Canine Hyperadrenocorticism”. Canine and Feline Endocrinology, Feldman EC, Nelson RW, Reusch CE, Scott-Moncrieff CR, Behrend EN, Elsevier Inc, 2015, pg. 403.

11. Bugbee A, Rucinsky R, Cazabon S, Kvito-White H, Lathan P, Nichelason A, Rudolph L. 2023 AAHA Selected Endocrinopathies of Dogs and Cats Guidelines. J Am Anim Hosp Assoc. 2023; 59.

12. Behrend EN, “Canine Hyperadrenocorticism”. Canine and Feline Endocrinology, Feldman EC, Nelson RW, Reusch CE, Scott-Moncrieff CR, Behrend EN, Elsevier Inc, 2015, pg. 405.

13. Massari F, Nicoli S, Romanelli G, Buracco P, Zini E. Adrenalectomy in dogs with adrenal gland tumors: 52 cases (2002-2008). 2011; 239(2):216-221.