Leukaemias are rare in dogs and cats compared to other solid neoplasms. They are difficult to diagnose in the early stages and can easily be confused with inflammation or other diseases. Therefore, in addition to a full blood count and a thorough medical history, additional diagnostic tests are required before the diagnosis of leukaemia can be confirmed.

What is leukaemia?

Leukaemia is a malignant disease of the bone marrow where the uninhibited, clonal proliferation of haematopoietic precursor cells leads to a more or less severe displacement of normal haematopoiesis in the bone marrow (BM).
A distinction can be made between lymphocytic and myeloid leukaemia (affecting erythrocytes, granulocytes, monocytes and thrombocytes).
Depending on their course and the proportion of blasts in the bone marrow and peripheral blood, leukaemias can be divided into acute and chronic. It is important to know the difference between leukaemia and lymphoma.

Both are haematopoietic neoplasms, but they develop in different tissues. Lymphomas typically develop in lymphatic tissue (e.g., lymph nodes and the lymphatic system). As in human medicine, it is sometimes difficult or impossible to differentiate precisely between lymphoma and lymphatic leukaemia, even with a detailed preliminary report.

Epidemiology

Both genetics and environmental influences play a role as risk factors for the development of leukaemia and lymphoma.
Familial, genetic relationships have been described in dogs (e.g., Golden Retriever, Gordon Setter, Portuguese Water Dog, Rottweiler and Irish Setter) and in oriental breeds of cats, such as Siamese cat. Environmental factors (e.g., exposure to cigarette smoke) and infectious diseases (FeLV) can also contribute to the development of haematopoietic neoplasia.

Rabbits, guinea pigs, rats, and other small animals are popular pets and daily patients in our small animal practices. As in all animals, mycoplasmas are also of great importance in small mammals. They are usually host-specific, so that different mycoplasma species have clinical relevance for (almost) every animal species.

Mycoplasma ‒ a special bacteria

Mycoplasmas are gram-negative bacteria. They are facultative aerobes and obligate parasites. They are unique mainly because of the absence of a cell wall – they are only bounded by a cytoplasmic membrane. They are also the smallest self-replicating organisms. They prefer the epithelia of the respiratory and urogenital tracts, articular cartilage, eyes, and mammary glands. Mycoplasma infections are chronic.

Note: The terminology is currently changing; in some places, Mycoplasma has already become Mycoplasmopsis. For the sake of simplicity, we will use the term Mycoplasma for all pathogens in this article.

Due to their morphological peculiarities, mycoplasmas can only be cultured under very special conditions. This is a lengthy and expensive process that is not relevant for routine diagnostics. Serology can only be used for a few mycoplasma species, but since seroconversion can take months and does not provide any information about clinical relevance, it is not a suitable diagnostic tool in cases of illness. The rapid and reliable detection of mycoplasma infections is possible using the polymerase chain reaction (PCR).

Important: For diagnostics using PCR, we require a dry swab (without transport medium) from the oropharynx/conjunctiva or a sample of fluid (bronchoalveolar lavage or nasal wash). The samples must be taken before treatment begins! It is not possible to create an antibiogram after a positive PCR result.

Thirteen of the currently 159 classified species of the genus Mycoplasma are associated with small mammals (as of 2022, see Table 1). Of these 13 species, only a few are truly clinically relevant, and we will take a closer look at them below.

What exactly is hypoadrenocorticism?

Why don’t we refer to it as Addison’s disease anymore?

The term “Addison’s disease” is no longer recommended in the current ALIVE guidelines (ALIVE: Agreeing Language in Veterinary Endocrinology) because it refers only to primary hypoadrenocorticism. The preferred term “hypoadrenocorticism” (hypoA) describes any form of adrenal cortex insufficiency. The causes can be both natural and iatrogenic and can be either adrenal (primary hypoA) or pituitary (secondary hypoA). In the classic case, primary hypoA is triggered by an immune-mediated loss of adrenal cortex function. The deficiency usually affects both glucocorticoids (primarily cortisol) and mineralocorticoids (primarily aldosterone), although isolated cortisol deficiency is also possible.
In contrast, in secondary hypoA, the hormones that stimulate the adrenal gland (primarily ACTH) are absent. This is almost always accompanied by a pure cortisol deficiency, as aldosterone can be produced and secreted independently of ACTH.

How do I diagnose hypoadrenocorticism?

The diagnostic process consists of the following steps:

a) Clinical suspicion

• Description: Hypoadrenocorticism can occur in any age, gender, or breed.
  However, young dogs between the ages of 3 and 4 years, as well as certain breeds, are predisposed (Table 1). In some studies, bitches were affected more frequently, but this does not appear to apply to all breeds.
• Clinical signs: The clinical signs can vary greatly and resemble those of other diseases, meaning that hypoA can be the cause of the symptoms in almost every case. However, hypoA should definitely be included in the differential diagnoses if polyuria/polydipsia, gastrointestinal symptoms, and weakness are present, especially if these symptoms occur recurrently and respond quickly to infusion therapy.

b) Suitable laboratory changes

• Haematology: Cortisol deficiency is often associated with mild, non-regenerative anaemia. However, a more specific sign is the lack of a stress leukogram in a critically ill patient. In particular, attention should be paid to the presence of lymphocytosis.
• Clinical chemistry:
  • Changes in electrolytes: Hyperkalaemia and hyponatraemia are typical of hypoadrenocorticism and are triggered by the lack of aldosterone.
    A pure cortisol deficiency will not be associated with hyperkalaemia, but it can also lead to hyponatraemia
  • Prenatal azotaemia: This is a consequence of reduced blood volume and reduced glomerular pressure due to an aldosterone deficit. Azotaemia usually is mild. However, in some patients with hypoA azotaemia can be unusually severe despite its purely prerenal nature.
  • Hypoglycaemia: This can result from cortisol deficiency.
  • Hypercalcaemia: The exact pathogenesis is unclear; usually it is an increase in total calcium, but increased concentrations of ionised calcium are also possible.
• Urinalysis: Despite the prerenal azotaemia, which should normally be associated with concentrated urine, hypoA results in a reduction in the urine-specific gravity (USG).

c) Cortisol screening

d) ACTH-Stim

The Na/K ratio as a screening method

A low ratio of sodium (Na) and potassium (K) (Na/K ratio) can be indicative of hypoA. However, the specificity is not particularly high, as there are many differential diagnoses (Table 2).
Adequate specificity is only present at Na/K < 20. It should also be kept in mind that hypoA is not always associated with hyperkalaemia.

Table 2: Differential diagnoses for a low Na/K ratio

Even healthy dogs can show very low basal cortisol concentrations

Due to the pulsatile release of cortisol, concentrations measured at any given time may be randomly low. Even in healthy dogs, serum cortisol concentrations may be below the detection limit.
An ACTH stim is therefore necessary in any case for values below the cut-off.

Why cortisol should be sent to a laboratory for measurement?

The ALIVE committee of the ESVE (European Society of Veterinary Endocrinology) points out the necessity of correct test validation and reliably performed quality controls when measuring cortisol. Measurement of cortisol in a reference laboratory is therefore recommended.

Serum is the preferred sample material

Cortisol can also be measured in (heparinised) plasma. However, serum should be used to standardise hormone measurements. In any case, you should avoid using different sample materials within one functional test.

It doesn’t always have to be “Addison’s”

Insufficient stimulation of cortisol after an injection of tetracosactide/cosyntropin in patients with normal adrenal function may be caused by incorrect test performance. However, glucocorticoid pre-treatment is much more often the cause. Even small amounts, administered briefly, a long time ago, or applied topically (including eye drops and ear ointment), can influence the pituitary-adrenal axis. Exogenously administered glucocorticoids lead to feedback to the pituitary gland, which stops producing adrenocorticotropic hormone (ACTH). The adrenal glands react very sensitively to this lack of endogenous ACTH stimulation with atrophy of the adrenal cortex.
The time required for the adrenal cortex to recover varies from individual to individual. The same applies to progestagens, which also have a gluco- corticoid effect. The medical history regarding possible previous treatments must therefore be taken very conscientiously.

Can dexamethasone be given in an emergency if an ACTH stimulation test cannot be carried out immediately?

Dexamethasone is not detected by the widely used cortisol assays and therefore does not interfere with the measurement. If a patient requires immediate treatment with a glucocorticoid in an emergency, before an ACTH stim can be carried out, the use of dexamethasone is therefore often recommended. However, the ACTH stimulation must then be carried out immediately. Any delay (even a few hours) can negatively influence the assessability of the test result. Dexamethasone affects the pituitary-adrenal axis like any other glucocorticoid.

The patient pre-treated with glucocorticoids

In an experimental study, healthy beagles given prednisolone for three weeks recovered their adrenal function within just two weeks after withdrawal.However, observations from other studies have identified patients who, even after relatively small amounts of glucocorticoids, showed a abnormal response to tetracosactide/cosyntropin for several weeks after discontinuation. In general, a period of 6-8 weeks without glucocorticoids is recommended before performing stimulation testing. If this is not possible, endogenous ACTH measurement (eACTH) and/or measurement of stimulated aldosterone serum concentration may be considered.

Hypoadrenocorticism despite cortisol stimulation

The typical patient with hypoA will not show any increase in cortisol concentration in response to ACTH stimulation. However, it should be noted that a certain degree of stimulation of cortisol is quite possible. Usually, a stimulated cortisol concentration in the lower quartile of the reference range (often below 20 ng/ml) is defined as consistent with hypoA. However, in some patients higher stimulated cortisol concentrations may be encountered.
In case of reasonable clinical suspicion, hypoA may be diagnosed even if the given cut-off is exceeded. The consultation of a specialist in endocrinology is recommended in these cases.
Furthermore, an isolated aldosterone deficiency has been described that is associated with hyperkalaemia and hyponatraemia with physiological cortisol stimulability.
However, this is limited to case reports.

What to do with questionable results of an ACTH stim

A correlation of clinical signs and laboratory changes is essential. In any case, the differential diagnoses need to be checked carefully.
A precise medical history regarding possible exposure to glucocorticoids (including topical therapy in people that are in close contact with the patient) needs to be taken.
Measurement of endogenous ACTH (eACTH) can support the diagnosis of primary hypoA. In primary hypoA, eACTH should be measurable or elevated. In patients pre-treated with glucocorticoids no eACTH is released.
However, eACTH concentrations below the detection limit are not conclusive and need to be interpreted cautiously. They do not exclude hypoA. There are two reasons to it: First, eACTH is instable and can easily be destroyed when sample handling (including shipment) is suboptimal. Second, eACTH is released from the pituitary in a pulsatile manner. This means that low concentrations may occur at any given time. When this happens, a low concentration will be detected.

Canine eACTH is unstable. For reliable results, EDTA plasma needs to be separated shortly after sampling, refrigerated, and shipped cooled.
The EDTA plasma must arrive at the laboratory in a cooled state (temperature not exceeding 8°C) to avoid incorrect results.

In case ACTH stim is not available

If an ACTH stim is not available, the cortisol/eACTH quotient can provide helpful information.
However, whether it can replace the ACTH stim as a diagnostic tool is still subject of discussion although some supporting study data is existing.
In order to avoid incorrect results arrival of EDTA plasma at the laboratory in a cooled state (temperature not above 8° C) is mandatory.

Eunatraemic/eukalaemic hypoadrenocorticism (‘Atypical’ Addison’s Disease)

Hyperkalaemia in patients with hypoA develops due to a deficiency in aldosterone. However, not every patient with hypoA is hyperkalaemic. Eunatraemic/ eukalaemic hypoA is seen in secondary hypoA (= pituitary disease = isolated cortisol deficiency), but secondary hypoA is rare. Absence of hyperkalaemia may also occur in patients with primary hypoA (= adrenal cortical insufficiency).
Either this is because the immune mediated destruction of the adrenal cortex has not yet reached the aldosterone producing parts, i.e. those parts have not been fully destroyed, and there is still enough aldosterone production left to control the potassium concentration. Or other factors influencing the blood potassium concentration (e.g. decreased intake due to inappetence, compensation via the kidneys in a still adequately hydrated patient) are in place.
Eunatraemic/eukalaemic hypoA should be considered in any patient with gastrointestinal signs. The presence of measurement of the serum aldosterone concentration may indicate whether or not there is a corresponding, therapeutically relevant deficiency.

Hypoadrenocorticism also occurs in cats

Hypoadrenocorticism has also been described in cats, albeit rarely. In particular, cats of the British Shorthair breed are frequently mentioned in the literature. Diagnostic cut-off values are extrapolated from dogs, although some endocrinologists argue that they should be set higher as those for dogs.

The Laboklin parameters and profiles for the diagnosis of hypoadrenocorticism

Cortisol, eACTH, and aldosterone can be measured separately. In addition, measurement of cortisol as part of the ACTH stimulation test and the cortisol/ eACTH ratio is offered. Two newly composed, helpful profiles are rounding out the Laboklin service with respect to hypoA: the intestinal profile and the “Addison’s profile”.
Since hypoA is often associated with non-specific gastrointestinal symptoms, the new intestinal profile also includes the measurement of cortisol, along with other important parameters such as pancreatic-specific lipase (PSL) and trypsin-like immunoreactivity (TLI).

Dr Jennifer von Luckner, Dr Ruth Klein

Table 3: Revised profiles and parameter combinations at Laboklin that are of interest when hypoadrenocorticism is suspected

Have you experienced any of these situation whilst in veterinary practice: an eight-week-old puppy suddenly developing a large haematoma after a microchip has been inserted, a female dog experiencing increased bleeding during her oestrus cycle, unusual post-operative bleeding after a routine neutering, a Labrador with a history of eating something in the park a a few days ago and is now presenting with signs of apathy, haematomas and coughing, a patient presented to the emergency room with severe thrombocytopenia?
These are not uncommon scenarios, however they can seriously disrupt the daily routine of a veterinary practice or clinic.
As a veterinarian you will be faced frequently with both congenital and acquired coagulation disorders. In daily practice, we encounter congenital and acquired coagulation disorders. After a (micro) trauma, clot/thrombi formation occurs physiologically in the blood vessels to limit blood loss.
The interaction between coagulation promoting and coagulation-inhibiting factors is important in this process. If these processes are disrupted, serious bleeding or thrombus formation can occur. Coagulation disorders are potentially lifethreatening, especially if they remain undetected.
A detailed case history, clinical examination and the right diagnosis are therefore extremely valuable so that early changes can be detected and the appropriate treatment regimes initiated.

Diagnostic Work-up

Pre-report and Clinical Examination

The work-up of a patient with a suspected coagulation disorder can be complex, as it is not always clear from the outset that there is a coagulation disorder. A detailed case history is therefore fundamental. The general case history for a patient with a suspected coagulation disorder includes the following:

• Breed, age and gender of the patient
• Regular tick prophylaxis?
• Any history of travel
• Previous illnesses
• Has the patient ever been diagnosed with a blood clotting disorder or thrombosis?
• Family history: Are there any cases of coagulation disorders in littermates or parents?
• Have unusually long bleeding times or increased bleeding been observed after injuries or procedures?
  • Dental treatment/teething
  • Castration
  • Births
  • Oestrus
  • Other surgical procedures or traumas
• Is the patient receiving medication that can affect blood clotting?
  • Painkillers
  • Blood-thinning medication
  • Other medication (antibiotics, dietary supplements, vitamins, etc.)
• Could the patient have ingested anything?
  • Rodenticides
  • Medication from the owner

In addition to the preliminary patient history, a thorough clinical examination is important.

Disorders of primary haemostasis are often characterised by diffuse mucocutaneous colour changes due to vascular defects.
Petechiae (punctiform bleeding), ecchymoses (small-area skin or mucous membrane bleeding), mucocutaneous haemorrhages, and epistaxis may also occur. In disorders of secondary haemostasis, haematomas, body cavity effusions, and bleeding into large joints are more likely to be found.
Note: The initial patient history and the clinical examination of the patient are important for the initial assessment of whether there is an increased tendency to bleed and whether the disorder is one of primary or secondary haemostasis.

Laboratory Diagnostics

The selection of appropriate laboratory diagnostic tests are essential for further evaluation.
Global tests are not always reliable. Activated partial thromboplastin time (aPTT) and prothrombin time (PT) can remain unchanged even when the patient has a coagulation disorder.
Depending on the clinical picture, a full blood count focusing on the platelet count and organ screening should also be conducted. Based on these results and clinical suspicion, further diagnostic work-up may be indicated.

Preanalytics

Preanalytics includes all the steps prior to the actual analysis and significantly contributes to the reliability of laboratory diagnostic findings, particularly for coagulation values.
Poor blood collection technique, severe stasis, or incorrect tube order can lead to inaccurate laboratory results. Citrate tubes should always be filled first when coagulation disorders are suspected. The reason for this is simple: serum tubes are often coated with procoagulants, which can contaminate the citrate tube and distort the measurement results. Citrate tubes may vary in colour depending on the manufacturer (usually blue or green) and come in different sizes.
The correct mixing ratio is crucial (9 parts blood, 1 part sodium citrate). Unlike other anticoagulants, coagulation in blood treated with sodium citrate can be restarted by adding activators. The amount of activator is precisely calibrated to the mixing ratio in the tube, so it is essential that the tube be filled exactly to the specified fill line. Any deviation in fill level can lead to inaccurate laboratory results and thus invalid values for the patient. Since these tubes are rarely used, it is advisable to check the expiry date before use. Even the formation of small or large clots can invalidate the analysis or render it impossible.
Tip: Regularly check your tube inventory for completeness and expiration dates, and ensure proper filling quantities.

Coagulation Tests

An overview of the various coagulation tests can be found in Table below.

Disorders of Primary Haemostasis

Various conditions can lead to disorders in primary haemostasis, including thrombocytopenia and platelet dysfunction.

Thrombocytopenia

In most cases, thrombocytopenia in small animals is an incidental finding. Thrombocytopenia refers to the reduction in platelet count to below the species-specific norm. It usually indicates a pathological process, which can lead to a coagulation disorder with significantly reduced platelet levels.
Often, more than one cause can contribute to thrombocytopenia. A distinction should be made between pseudothrombocytopenia and true thrombocytopenia. Pseudothrombocytopenia occurs when not all the platelets present are counted during platelet analysis.
Therefore, a manual microscopic assessment is always recommended before proceeding with further investigation. Possible causes of true thrombocytopenia include reduced production in the bone marrow, increased consumption, destruction of thrombocytes, or increased sequestration.

Von Willebrand Factor Deficiency

Von Willebrand disease (vWD) is the most common genetic bleeding disorder and varies in severity. It results from a defective or missing Von Willebrand factor (vWF) in the blood, which plays a role in blood clotting. A defective or absent vWF causes affected animals to bleed for extended periods when injured and, in severe cases, can lead to fatal haemorrhage. The bleeding primarily affects mucous membranes and can be exacerbated by additional illnesses or stress. Typical signs include recurrent bleeding in the gastrointestinal tract (with or without diarrhoea), epistaxis, bleeding gums, prolonged bleeding during oestrus, lameness due to joint haemorrhage, bruising, excessive bleeding after surgery, or from nails that have been cut too short. vWD is classified into three types (Type 1, 2, and 3), with Type 1 being the mildest form. Laboratory findings show no prolongation of PT, aPTT, and TCT.

Disorders of Secondary Haemostasis

Various diseases can cause disorders of secondary haemostasis, which may be either congenital or acquired.

Haemophilia A and B

These congenital coagulation disorders follow an X-linked recessive inheritance pattern.
Male animals are either clinically affected or healthy, while females are usually clinically asymptomatic carriers. Haemophilia A is caused by a deficiency or reduced activity of factor VIII, whereas Haemophilia B results from a deficiency of factor IX. Mild to severe bleeding disorders are possible. Clinically noticeable signs in affected animals often include large haematomas, epistaxis, and bleeding in the skin, muscles, and joints. Severe cases following major injuries or surgeries can be fatal. Haemophilia often occurs in certain families or breeds.

Haemophilia A is one of the most important inherited blood clotting disorders in Havanese dogs, while Haemophilia B is significant in the Rhodesian Ridgeback breed.

Liver Disease

Liver disease can result in defective production of both procoagulant and anticoagulant factors. PT, aPTT, ACT, or TCT may be increased.
Bleeding is uncommon but can occur in severe liver failure or in the setting of disseminated intravascular coagulation (DIC).

Vitamin K Antagonists and Vitamin K Deficiency

Vitamin K antagonists, such as coumarin derivatives (e.g. from rat poison), sweet clover, or certain medications, can cause internal and/or external bleeding, which usually occurs within 3 to 7 days of ingestion. Since these substances affect the vitamin K cycle, a possible increase in vitamin K epoxide concentration can be measured (coumarin activity). Coagulation tests typically show an increase in PT first (Quick value), with aPTT and TCT usually also increasing over the course of the test.

Consumption Coagulopathy

Consumption coagulopathy, or disseminated intravascular coagulopathy (DIC), is a coagulation disorder caused by the intravascular activation of blood coagulation. This leads to a significantly increased consumption of plasma coagulation factors and thrombocytes, resulting in a deficiency of these factors and thrombocytopenia.
The outcome can be bleeding. DIC always develops secondarily as a result of diseases that trigger excessive coagulation, such as tissue necrosis, heat stroke, infection with Angiostrongylus vasorum, neoplasia, endotoxaemia, sepsis, liver disease, poisoning, and pancreatitis.
Laboratory findings include thrombocytopenia, prolonged PT, aPTT, and TCT, along with increased D-dimers.

Conclusion

Blood coagulation is a complex topic, and diagnosing patients with coagulation disorders is often challenging. However, a thorough medical history and targeted tests can help make the correct diagnosis and thus rectify the problem.

Dr. med. vet. Annemarie E. Baur-Kaufhold
Translation: Laboklin

Can a single blood sample simplify the invasive and expensive work-up of tumour patients? This is a question frequently faced by both owners and veterinarians. The general answer is: to some extent. Blood samples can indeed provide crucial information for diagnosis and monitoring.
This article explores the current status of this approach.

First of all, serological tests should be distinguished from liquid biopsy methods. Serological tests detect proteins produced by tumour cells in the blood, whereas liquid biopsy methods are employed to identify DNA, RNA, and nucleic acid-associated proteins in body fluids.

Haematology

Non-regenerative anaemia is often associated with tumour diseases such as anaemia of chronic disease. It can indicate bone marrow infiltration by neoplastic cells (e.g., in leukaemia, lymphoma, multiple myeloma, or other metastases) or oestrogen-producing tumours (such as Sertoli cell tumours). Different cell lines are typically affected in cases involving bone marrow, making it important to consider relevant tumours, especially when accompanied by neutropenia and/or thrombocytopenia.

Thrombocytopenia is commonly observed in spleen tumours, while thrombocytosis can also arise in various neoplastic conditions.

Massive lymphocytosis can occur with lymphoproliferative neoplasms.

Eosinophilia may arise, for instance, as a response to a mast cell tumour or in association with T-cell lymphoma.

Blood Chemistry

Specific blood chemistry parameters can offer valuable insights for an oncological work-up, including globulins, lactate dehydrogenase (LDH), and calcium (Ca).

Hyperglobulinaemia is observed in antibody-producing tumours such as multiple myeloma, plasmacytoma, and B-cell lymphoma/leukaemia. Serum electrophoresis can provide evidence of this condition (see Fig. 2).
The elevated metabolism in tumour tissue and the associated rapid cell proliferation increase lactate dehydrogenase (LDH). High LDH levels in the blood of dogs may indicate malignant tumour diseases.
More importantly, an increase in LDH levels in lymphoma patients undergoing therapy can indicate a potential recurrence.

At the Laboklin expert panels, renowned experts provide answers to questions on exciting and current topics. We have summarised the highlights from the panel on CKD for you. The invited experts were PD Dr. Roswitha Dorsch from (senior lecturer for urology and nephrology at LMU Munich, Germany), PD Dr. Petra Kölle (senior lecturer for animal nutrition at LMU Munich, Germany), Prof. Dr. Rafael Nickel (Dipl. ECVS, Evidensia Veterinary Clinic Norderstedt and Associate Professor for urology at FU Berlin, Germany), and Dr. Ariane Schweighauser (Dipl. ACVIM and ECVIM-CA (Internal Medicine), specialised in nephrology and extracorporeal blood purification procedures at Vetsuisse University of Bern, Switzerland).

Dr Dorsch kicks things off by explaining how chronic kidney disease (CKD) is defined. It is characterised by a long-term reduction in kidney function and/or changes in kidney structure, affecting one or both kidneys. CKD is defined as lasting more than 3 months, which is the time it can take for kidneys to recover from an acute kidney injury.

The cause of CKD often remains unknown, but sometimes metabolic or congenital diseases, as well as dietary factors, are identified during the diagnostic process. Ureteral obstructions, chronic bacterial infections, and infectious diseases may also be involved. Notably, cats with CKD often show higher levels of antibodies against leptospires compared to healthy cats. Therefore, testing for leptospirosis using tests such as the MAT and urine PCR may be considered for free-range cats that hunt mice.

According to Dr. Schweighauser, acute renal injury will always leave the kidneys with a certain amount of residual damage. Therefore, lifelong monitoring of kidney function is essential to detect complications such as hypertension and possible progression to CKD. This enables timely intervention and adjustment of treatment.

PD Dr Kölle emphasises that avoiding excessive protein and phosphate is an important measure to minimise the risk for CKD development and progression. She advises feeding a diet composed for senior pets to dogs and cats once they reach the age of 8 years. As a general rule, excess protein in a cat’s diet, often resulting from expensive, meatheavy food, should be avoided.

Prof Dr Nickel points out that mechanical outflow obstructions can lead to a CKD in the long term or enhance its progression. When asked whether he considered the calcium oxalate stones often found in the context of CKD to be the cause or consequence, he replied that the primary disease is localised in the tubules. In the first instance, it is probably the result of CKD however, its stage also triggers further damage.

Feline coronaviruses (FCoV) are distributed worldwide and commonly seen in veterinary practice. There are two different biotypes:

Feline enteric coronaviruses (FECV) infect the enterocytes of the intestine. They are seen as low pathogenic and can cause mild enteritis. These viruses are transmitted via the faecal-oral route. Re-infections are common.

Feline infectious peritonitis viruses (FIPV) originate in mutations in individual host cats, which had been infected with FECV. A change in biotype is accompanied with a change in tropism for host cells: the viruses are now able to penetrate macrophages and can therefore invade different tissue types. This presents with a very different clinical picture, namely the feline infectious peritonitis (FIP). FIP is a life-threatening disease of individual cats, which presents with distinct clinical symptoms. These include, among others, fever, lethargy, anorexia, weight loss, swollen abdomen, icterus, dyspnea, neurological symptoms and uveitis. Usually, the potential for transmission of FIPV is negligible.

At least until now.

During 2023, there was a massive increase in FIP-cases on the island of Cyprus.

During the first seven months of that year, the number of cases confirmed by PCR increased 40-fold, compared to the previous year (Fig. 1). The actual number of affected cats is unknown, since there are many stray cats on Cyprus. The „Pancyprian Veterinary Association“ estimates the number of deceased cats until July 2023 at around 8000. A FIP outbreak of this magnitude has not been observed previously.

Small mammals are fleeing and prey animals. Serious illnesses must remain unrecognised for a long time, otherwise the animals can easily become victims of predators! Laboratory diagnostics are therefore an important part of the diagnostic process, especially in the case of non-specific symptoms such as apathy, inappetence and lack of mobility. Not only changes in the red (anaemia, dehydration) and white blood count (pseudo-left shift, lymphoma) can be indicative. Changes in the activity and concentration of clinical-chemical parameters (enzymes, substrates, electrolytes) show which organs are affected or what type of metabolic change is present. The most important parameters are listed in Table 1 for “quick reference”.

Liver metabolism

The enzymes GLDH, ALT, AST, γ-GT, AP and the substrates glucose, albumin, urea, bilirubin, triglycerides and serum bile acids are also considered liver parameters in small mammals. These are determined in either serum or plasma.

The GLDH (glutamate dehydrogenase) is found in the mitochondria of liver cells (centrilobular) as well as heart and kidney cells (Wesche 2014). It is the most sensitive liver enzyme and responds even to mild cell damage (acute hepatopathies due to anorexia (fat storage) and/or intoxication) and is a good marker for acute, incipient liver problems (Leban-Danzl et al. 2016). The measurement is not yet available for in-house diagnostics.

The ALT (alanine aminotransferase) is considered to be liver-specific and is mainly found in the cytoplasm of liver and heart muscle cells (Hein 2014). It is less sensitive than GLDH, is only released as liver cell damage progresses and therefore indicates more severe and/or chronic liver damage (Leban-Danzl et al. 2016). A correlation between liver cell death and ALT activity has been described (Jenkins 2000).

The AST (aspartate aminotransferase) is similarly sensitive as the ALT, but is not specific to the liver, as it also occurs in the heart and skeletal muscle. An increase in AST activity should therefore always be interpreted together with CK activity (muscle enzyme) and the other liver parameters in order to differentiate between a muscle-associated increase in concentration (Leban-Danzl et al. 2016). ALT and AST are also present in certain quantities in erythrocytes, i.e. they are also released in small quantities during haemolysis without a liver problem being present.

AP (alkaline phosphatase) and γ-GT (gamma-glutamyltransferase) are mainly found in the bile ducts, but are also not liver-specific and are rather inert (Hein 2014). If their activity is increased and the bilirubin and serum bile acid (SGS) concentration in the serum/ plasma also rises, one can assume cholestasis. In rabbits, AP is particularly inert and a steroid-sensitive isoenzyme does not develop in them. In other small mammals, AP activity is increased, especially in young animals, due to increased bone metabolism and possibly also in other hepatopathies, osteopathies, pregnancy and bone loss (Leban-Danzl et al. 2016).

Liver metabolism is usefully assessed in conjunction with the substrates glucose, albumin, urea, bilirubin, triglycerides and bile acids in order to differentiate between pre- and intrahepatic causes of cholestasis (posthepatic). Rabbits have a particularly active fat metabolism. In phases of anorexia, there is rapid fat mobilisation and storage in the liver (hepatic lipidosis) (Hein 2014). In liver cirrhosis, an increase in enzymes is often no longer detected as the capacity of the liver cells is exhausted. Blood parasites or autoimmune haemolytic anaemia have not yet been described in small mammals (Hein 2019).

Accordingly, mild hepatopathies only begin with an increase in GLDH activity. Depending on the severity and duration of the problem, AST and ALT activity increase and all other liver parameters only change in the event of severe damage. Massive changes in liver parameters occur primarily in RHD, massive liver coccidiosis, intoxications and/or liver lobe torsions.

Renal metabolism

Urea and creatinine concentrations are considered reliable kidney parameters in small mammals. The data available on SDMA measurement in small mammals is currently still too limited.

In carnivorous or insectivorous small mammals, the urea concentration is, as in dogs and cats, dependent on food intake (protein-rich food) (Hein 2014). Herbivorous small mammals only consume a small amount of protein with their food. Therefore, in contrast to carnivorous or insectivorous small mammals, the urea concentration in their blood is independent of their diet. An isolated increase in the urea concentration can be an indication of gastrointestinal haemorrhage (reabsorption of blood) (Hein 2014). Late-stage liver insufficiency and/or a reduced protein intake can lead to a drop in urea concentrations.

Creatinine is a non-specific muscle parameter and, as the end product of endogenous muscle metabolism, is a reliable and nutrition-independent renal parameter. The creatinine concentration is influenced accordingly by muscle mass, exercise activity and renal function (Hein 2014).

If urea and creatinine concentrations are elevated at the same time, this is referred to as azotemia. Azotaemia can occur prerenally (dehydration, hypovolaemia, renal hypoperfusion), renally (acute or chronic renal insufficiency) and/or postrenally (obstruction of the urinary tract).

Pancreatic metabolism

Although only of minor importance in herbivores due to the predominance of bacterial digestion, the measurement of α-amylase and lipase activity is also possible in small mammals. Rabbits have a high lipase activity, which explains the rapid mobilisation of fat and their tendency to liver lipidosis during periods of starvation, while the α-amylase activity is rather low. In contrast to others, rabbits tend to have permanently high glucose and fructosamine concentrations.

Glucose metabolism

Herbivorous small mammals are never physiologically fasting.

The glucose and fructosamine concentrations provide information on the sugar metabolism. Fructosamines are glycosylated serum proteins. The glucose concentration of the last 3 weeks is reflected in the fructosamine concentration.
Longer-term changes in the glucose concentration (diabetes, insulinoma) can therefore be detected more easily, while short-term changes (e.g. short hunger phases, glucose administration) have hardly any influence.

Both substrates are determined from promptly centrifuged, separated serum or heparin plasma, regardless of the time of the last feed intake (except ferrets 2-4 hours off food). Otherwise there will be falsely low glucose concentrations due to degradation by the remaining erythrocytes and changes in the fructosamine concentration due to haemolysis. Hypoproteinaemia of any kind also leads to falsely low fructosamine concentrations, and lipaemia also influences the fructosamine concentration. The results should therefore always be critically reviewed and checked if necessary.

Diabetes mellitus is rather rare in small mammals and is mostly diet-related. Differential diagnoses for hyperglycaemia are: stress, iatrogenic intake, hormone influence (glucocorticoids, progesterone) (rather mild) and in rabbits ileus (severe). In rabbits, the glucose and fructosamine concentration is permanently high, as they only metabolize carbohydrates slowly, but quickly switch to gluconeogenesis (Harcourt-Brown and Harcourt-Brown 2012). Determining the glucose concentration can therefore be helpful in rabbits with suspected ileus. The higher the glucose concentration, the more likely an ileus is in an inappetent rabbit, and the longer it persists, the worse the prognosis (Harcourt-Brown and Harcourt-Brown 2012). If hyperglycaemia and hyponatraemia (sodium < 129 mmol/l) occur together in severely ill rabbits, the mortality rate is 2.3 times higher (Bonvehi et al. 2014).

Lipid metabolism

Fat metabolism includes triglycerides, cholesterol and serum bile acids. Increases in triglyceride concentrations occur rapidly in rabbits during periods of anorexia and are the first indication of impending liver lipidosis. Hypercholesterolaemia is mainly described in guinea pigs and is associated with fatty infiltrations in the liver and other tissues (Hein 2014).

Protein metabolism

The total protein and albumin concentration can be measured photometrically and the albumin and globulin fractions by means of electrophoresis.
These measurements are important for symptoms associated with a disturbance in the water and protein balance, such as diarrhoea, polydipsia/ polyuria, weight loss, etc. Acute phase proteins have so far only played a minor role in small mammals.

Electrolyte metabolism

Sodium, potassium, calcium and phosphate concentrations are also measured in small mammals. The determination of other electrolytes such as chloride, magnesium, iron etc. is also possible.

Herbivorous small mammals do not take up calcium according to their needs, but according to their diet and – except in the case of calcium deficiency – also independently of vitamin D via intestinal absorption. This results in physiological fluctuations in the serum calcium level. In rabbits, guinea pigs and degus, up to 65 % of excess calcium is excreted via the urinary tract (in contrast to < 2 % in most other pets) (Hein 2014). Excess calcium results in urinary gravel and uroliths in the urinary tract.
Chinchillas largely excrete excess calcium in their faeces. Uroliths are therefore rare in them, but tissue and possibly aortic calcifications are all the more common. Meaningful studies on the relationship between calcium and phosphate concentrations in small mammals are still lacking.

Potassium plays a similar role in small mammals as in dogs and cats, but their tolerance to fluctuations in potassium concentration, e.g. in neoplasia, appears to be greater. Hyperkalaemia occurs during whole blood transfusions as a result of haemolysis (release from thrombocytes, leucocytes and erythrocytes).

Conclusion

With the help of clinical-chemical parameters, the metabolic situation in small mammals can be assessed well and diseases can be diagnosed quickly and easily.

Jana Liebscher, Dr Jutta Hein

Table 1: Clinical-chemical parameters with organ/metabolic affiliation

Dangers from rodenticides and dead rodents

Rodenticides (‘rat poisons’) are repeatedly the cause of life-threatening poisoning in dogs and cats. Primary poisoning can occur through the direct ingestion of poisoned bait, e.g. if it has been improperly placed in an open area for ‘pest control’ (Fig. 1a). Secondary poisoning can result from the ingestion of poisoned rodents (Fig. 1b). The ingestion of the bait or the dead rodents is often not directly observed by the animal owners or it is often not known what type of poison is involved. If the animals are presented to the practice with suspected poisoning, the ‘cat-and-mouse game’ often begins with the search for the cause of the poisoning symptoms or the poison causing it.
Two currently important rodenticides and classes are presented below:

α-Chloralose

The use of this substance, which was originally used as a narcotic and later also as an avicide (poison against birds), has risen significantly in Europe in recent years (Dijkman et al. 2023). The sale of bait material containing the poison α-chloralose is poorly regulated, making it easy and therefore common to obtain through online sales.

Symptoms of poisoning with α-chloralose are essentially based on the depressive effect of the substance on the central nervous system (CNS).

Depending on the dose, seizures and convulsions, particular susceptibility to external stimuli (hyperreflexia), hypersecretion, depression, somnolence, bradypnoea and even dsypnoea may occur. Hypothermia is also common, as the poison also impairs thermoregulation through the CNS (toxic principle particularly effective against wild rodents and birds). The occurrence of neurological symptoms combined with hypothermia can confirm the suspicion of poisoning with α-chloralose.

Poisoning with α-chloralose must be counteracted by symptomatic therapy, in particular by stabilising measures for circulation, respiration and body temperature. Direct detection of the toxin is possible from serum or urine. Decontamination should be considered if the ingestion occurred within the last few hours.

The gold standard in the diagnosis of mast cell tumours (MCT) is cytology and histopathology. Clinical staging is based on the clinical picture including the lymph node status (cytological/ histological). Immunohistological and molecular genetic methods are also available for more precise characterisation.

Cytology is used for preoperative diagnosis (Fig. 1) and clinical staging (e.g. lymph nodes, spleen). Although cytological grading of canine mast cell tumours has been published (Blackwood et al. 2012), it has limitations, as the cytological malignancy criteria are often overestimated with subcutaneous MCT not being identified.

Histopathology can be used to distinguish cutaneous from subcutaneous mast cells and assess the resection margins. Histological grading enables a statement to be made regarding the biological behaviour (probability of recurrence, risk of metastasis, survival times) of cutaneous mast cell tumours in dogs.

There are two histopathological grading systems for cutaneous mast cell tumours in dogs: The older grading system according to Patnaik et al. (1984) distinguishes between three tumour grades (grade I well differentiated – Fig. 2 -, grade II moderately differentiated and grade III poorly differentiated). It is based on the following criteria, among others: tumour loca- lisation, cell morphology, nuclear morphology, overall architecture and number of mitoses. As this system contains several criteria that are not easy to objectify, a modified two-stage system was established that is based on parameters that are easier to measure (Kiupel et al. 2011). In accordance with the recommendations of the consensus group (Berlato et al. 2021), a combination of both grading systems is currently usually specified, which correlate with prognostic statements (see Table 1) (Stefanello et al. 2015).

If a mast cell tumour is subcutaneous, the grading systems according to Patnaik et al. (1984) and Kiupel et al. (2011) should not be used, as subcutaneous MCTs are generally less malignant than cutaneous MCTs (Bellamy and Berlato 2022). With a few exceptions, they can generally be well controlled locally and usually require no further treatment once they have been completely removed (Betz 2021).

Table 1: Prognostic statements for cutaneous mast cell tumours in dogs, based on the combined grading systems of Patnaik et al. (1984) and Kiupel et al. (2011) – modified according to Stefanello et al. (2015)

Furthermore, lymph nodes can be examined histologically for a neoplastic tumour cell population. The assessment is based on the scheme by Weishaar et al. (2014). The prognosis is significantly better in stages HN0/HN1 than in HN2/HN3.

HN0: None to isolated (0-3 mast cells/HPF), scattered and solitary mast cells in the sinus (subcapsular, paracortical or medullary) and/or in the parenchyma. Assessment: no metastatic infiltration (reactive or normal).

HN1: More than 3 scattered and solitary mast cells in the sinus (subcapsular, paracortical or medullary) and/or parenchyma in at least 4 HPF. Assessment: pre-metastatic (grey area).