Hypomagnesemia in Acute Leptospirosis

I have seen this in my canine patients. Have you seen it as well?

Case report: severe, symptomatic hypomagnesemia in acute leptospirosis.

Spichler A, Athanazio DA, Furtado J, Seguro A, Vinetz JM.

We report a case of severe hypomagnesemia in non-oliguric acute renal failure caused by leptospirosis that required large doses of magnesium replacement during the acute phase of disease. Biochemical studies confirmed kidney-related magnesium wasting and the mechanisms of this defect are discussed. Magnesium imbalance with its attendant clinical complications occurs in leptospirosis and should be monitored and treated aggressively in cases of leptospirosis-induced non-oliguric acute kidney injury.

PMCID: PMC2637037
PMID: 19052304 [PubMed - indexed for MEDLINE]

Evanger's Dog and Cat Food Warning

FDA Suspends Temporary Emergency Permit for Evanger's

Recently the FDA and USDA announced suspension of a permit for Evanger's Dog and Cat Food Company.

In the statement the FDA reports that:

"Evanger's, operating in Wheeling, Illinois, deviated from the prescribed process, equipment, product shipment, and recordkeeping requirements in the production of the company's thermally processed low acid canned food (LACF) products. The deviations in their processes and documentation could result in under-processed pet foods, which can allow the survival and growth of Clostridium botulinum (C. botulinum), a bacterium that causes botulism in some animals as well as in humans."

A recall has not been announced. But please do keep in mind the possibility of Clotridium botulinum infection in cases presenting with flaccid paralysis who have ingested Evanger's canned foods.

What have our consultants been writing?

Christal Pollock, DVM, DABVP (Avian)

Carpenter JW, Pollock CG, Koch DE, Hunter RP. Single- and multiple-dose pharmacokinetics of marbofloxacin after oral administration to rabbits. Am J Vet Res. 2009 Apr;70(4):522-6. PubMed PMID: 19335109.

Pollock CG. West Nile virus in the Americas. J Avian Med Surg. 2008 Jun;22(2):151-7. PubMed PMID: 18689077.


Pollock C. Diagnosis and treatment of avian renal disease. Vet Clin North Am Exot Anim Pract. 2006 Jan;9(1):107-28. Review. PubMed PMID: 16407082.


Michael D. Willard, DVM, MS, DACVIM (Small Animal Internal Medicine)

Willard MD. Endoscopic diagnosis of diseases causing vomiting. Top Companion Anim Med. 2008 Nov;23(4):162-8. Review. PubMed PMID: 19081549.

Farnsworth CC, Herman JD, Osterstock JB, Porterpan BL, Willard MD, Hooper RN, Roussel AJ, Schmitz DG, Fogelberg K, Kochevar DT. Assessment of clinical reasoning skills in veterinary students prior to and after the clinical year of training. J Am Vet Med Assoc. 2008 Sep 15;233(6):879-82. PubMed PMID: 18795847.

Willard M. Therapeutic approach to chronic electrolyte disorders. Vet Clin North Am Small Anim Pract. 2008 May;38(3):535-41, x. Review. PubMed PMID: 18402879.


Chelsea Greenberg, DVM, DACVIM (Oncology)

Greene SN, Lucroy MD, Greenberg CB, Bonney PL, Knapp DW. Evaluation of cisplatin administered with piroxicam in dogs with transitional cell carcinoma of the urinary bladder. J Am Vet Med Assoc. 2007 Oct 1;231(7):1056-60. PubMed PMID: 17916030.

Greenberg CB, Boria PA, Borgatti-Jeffreys A, Raskin RE, Lucroy MD. Phase II clinical trial of combination chemotherapy with dexamethasone for lymphoma in dogs. J Am Anim Hosp Assoc. 2007 Jan-Feb;43(1):27-32. PubMed PMID: 17209082.

Neurology Case of the Month

This report is based on video evaluation and conversation with Dr. Smith regarding Fluffy Jones [regarding neurologic signs following ear cleaning].

The video evaluation is as follows: Mentation: BAR, Gait: mild vestibular quality ataxia, occasional stumbling to the right and/or left side, no evidence of UMN involvement or paresis, CN’s: Horner’s syndrome OD-rest NSF and no evidence of spontaneous nystagmus. Postural responses and reflexes were not evaluated. A mild right head tilt was also evident and occasional wide head excursions noted. The patient appears extremely alert and responsive and there does not seem to be evidence of central vestibular disease. However, she is currently on prednisone which may mask some clinical abnormalities.

Denervation hypersensitivity testing should be performed using phenylephrine OU. To confirm that the Horner’s syndrome is indeed a third order Horner’s (i.e. a post ganglionic lesion typically seen with otitis media), phenylephrine drops are used OU and any ocular changes monitored every few minutes. If resolution or near-resolution of the Horner’s occurs in less than 20 minutes, then the lesion is post-ganglionic and would support our presumption that we are dealing with ear disease. If it is between 20-40 minutes, a second order Horner’s must be considered, such as is seen with diseases of the mediastinum. If it takes greater than 40 minutes for resolution, then disease within the cervical spinal cord or midbrain must be considered (which is highly unlikely in this cat).

Since no ototoxic drugs were used to my knowledge, clinical signs likely have resulted from irritation to the sympathetic innervation in the middle ear as well as the vestibulocochlear nerve in the inner ear during the ear cleaning. If so, clinical signs will likely resolve over time but it may take months for the Horner’s syndrome to fully disappear. However, since there is no indication for prednisone in this cat and since prednisone may very well be masking a possible central vestibular disorder, re-evaluation after tapering prednisone is indicated including a full neurologic exam. If signs recur or other signs arise, MRI scanning of the head may be indicated.

Georgina Barone, DVM, DACVIM (Neurology)

Cool Recent Abstracts

SMALL ANIMAL

Intracranial Arachnoid Cysts in Dogs

from Compendium by Curtis W. Dewey - Veterinary Answers Consultant, Peter V. Scrivani, Ursula Krotscheck, Sofia Cerda-Gonzalez, Kerry Smith Bailey, Dominic J. Marino

Intracranial arachnoid cyst (IAC) is an infrequently reported developmental disorder seen primarily in small-breed dogs. It usually occurs in the caudal fossa, in the region of the quadrigeminal cistern. Although still considered uncommon, IAC is being recognized more frequently in veterinary medicine, coinciding with the increased availability of magnetic resonance imaging. In this article, clinical information from previously reported cases of canine IAC is combined with additional case information from our hospitals. Similar to IAC in people, it is thought that canine IAC is often an incidental finding. When IAC is responsible for neurologic disease in dogs, generalized seizures and cerebellovestibular dysfunction are the most common clinical presentations. Medical therapy of IAC focuses on management of increased intracranial pressure and seizures, if the latter are part of the clinical complaints. Surgical therapy of IAC involves either cyst fenestration or shunting the excess fluid to the peritoneal cavity.


Peripheral Nucleated Red Blood Cells as a Prognostic Indicator in Heatstroke in Dogs

from JVIM by I. Aroch, G. Segev, E. Loeb, Y. Bruchim

Heatstroke in dogs is often fatal and is associated with a high prevalence of secondary complications. Peripheral nucleated red blood cells (NRBC) occur in dogs with heatstroke, but their association with complications and the outcome is unclear. Peripheral NRBC are common in dogs with heatstroke and have prognostic significance. Forty client-owned dogs with naturally occurring heatstroke. Prospective, observational study. Dogs were followed from presentation to discharge or death. Serum biochemistry and coagulation tests were performed at presentation. CBC and evaluation of peripheral blood smears were performed at presentation and every 12 hours. The relative and the absolute NRBC numbers were calculated. Presence of NRBC was observed in 36/40 (90%) of the dogs at presentation. Median relative and absolute NRBC were 24 cells/100 leukocytes (range 0[ndash]124) and 1.48 × 103/[mu]L (range 0.0[ndash]19.6 × 103/[mu]L), respectively. Both were significantly higher in nonsurvivors (22) versus survivors (18) and in dogs with secondary renal failure and DIC versus those without these complications. Receiver operator curve analysis of relative NRBC at presentation as a predictor of death had an area under curve of 0.92. A cut-off point of 18 NRBC/100 leukocytes corresponded to a sensitivity and specificity of 91 and 88% for death. Relative and absolute numbers of peripheral NRBC are clinically useful, correlate with the secondary complications, and are sensitive and specific markers of death in dogs with heatstroke, although they should never be used as a sole prognostic indicator nor should they replace clinical assessment.


Relationships between Low Serum Cobalamin Concentrations and Methlymalonic Acidemia in Cats

from JVIM by C. G. Ruaux, J. M. Steiner, D. A. Williams

Serum cobalamin concentrations below reference range are a common consequence of gastrointestinal disease in cats. Serum cobalamin [le] 100 ng/L is associated with methylmalonic acidemia. To determine the prevalence of cobalamin deficiency, defined by elevated serum methylmalonic acid (MMA), in cats with serum cobalamin [le] 290 ng/L, and the optimum serum cobalamin concentration to predict cobalamin deficiency in cats. Residual serum samples (n = 206) from cats with serum cobalamin [le] 290 ng/L. Retrospective, observational study. Serum cobalamin and folate were measured with automated assays. Serum MMA was determined by gas chromatography-mass spectrometry. Cobalamin deficiency was defined as serum MMA > 867 nmol/L. Sensitivity and specificity of serum cobalamin concentrations [le]290 ng/L for detecting MMA > 867 nmol/L were analyzed using a receiver-operator characteristic curve. There was a negative correlation between serum cobalamin and MMA concentrations (Spearman's r=[minus]0.74, P < 0.0001). The prevalence of MMA [ge] 867 nmol/L in cats with serum cobalamin [le] 290 ng/L was 68.4%. Serum cobalamin [le] 160 ng/L had a 74% sensitivity and 80% specificity for detecting MMA > 867 nmol/L. No significant difference in serum folate concentrations was detected between affected and unaffected cats. Elevated MMA concentrations, suggesting cobalamin deficiency, are common in cats with serum cobalamin [le] 290 ng/L. Cobalamin deficiency is clinically significant, and supplementation with parenteral cobalamin is recommended for cats with gastrointestinal disease and low serum cobalamin concentrations.

For more on MMA in human beings, click here.


Small Mammals
Single- and multiple-dose pharmacokinetics of marbofloxacin after oral administration to rabbits

From AJVR by James W. Carpenter, MS, DVM; Christal G. Pollock, DVM (VETERINARY ANSWERS CONSULTANT); David E. Koch, MS; Robert P. Hunter, PhD

Objective—To determine the pharmacokinetics of marbofloxacin after oral administration every 24 hours to rabbits during a 10-day period.

Animals—8 healthy 9-month-old female New Zealand White rabbits.

Procedures—Marbofloxacin (5 mg/kg) was administered orally every 24 hours to 8 rabbits for 10 days. The first day of administration was designated as day 1. Blood samples were obtained at 0, 0.17, 0.33, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, and 24 hours on days 1 and 10 of marbofloxacin administration. Plasma marbofloxacin concentrations were quantitated by use of a validated liquid chromatography–mass spectrometry assay. Pharmacokinetic analysis of marbofloxacin was analyzed via noncompartmental methods.

Results—After oral administration, mean ± SD area under the curve was 10.50 ± 2.00 μg·h/mL and 10.90 ± 2.45 μg·h/mL, maximum plasma concentration was 1.73 ± 0.35 μg/mL and 2.56 ± 0.71 μg/mL, and harmonic mean terminal half-life was 8.0 hours and 3.9 hours for days 0 and 10, respectively.

Conclusions and Clinical Relevance—Marbofloxacin administered orally every 24 hours for 10 days appeared to be absorbed well and tolerated by rabbits. Administration of marbofloxacin at a dosage of 5 mg/kg, PO, every 24 hours is recommended for rabbits to control infections attributable to susceptible bacteria.


EQUINE
Risk Factors for Equine Postoperative Ileus and Effectiveness of Prophylactic Lidocaine

from JVIM by S. Torfs, C. Delesalle, J. Dewulf, L. Devisscher, P. Deprez
Postoperative ileus (POI) is a frequent and often fatal complication of colic surgery. Reliably effective treatments are not available. To determine risk factors and protective factors associated with POI, and to assess the effect of lidocaine IV on short-term survival. One hundred and twenty-six horses that underwent small intestinal colic surgery and that survived for at least 24 hours postoperatively. Retrospective cross-sectional study. The association of 31 pre-, intra-, and postoperative variables with POI and the association of lidocaine treatment with short-term survival were investigated. Associations were evaluated with univariable logistic regression models, followed by multivariable analysis. Significant associations of high heart rate (odds ratio [OR] = 1.05, 95% confidence interval [CI] 1.03[ndash]1.08), the presence of more than 8 L of reflux at admission (OR = 3.02, 95% CI 1.13[ndash]8.02) and the performance of a small intestinal resection (OR = 2.46, 95% CI 1.15[ndash]5.27) with an increased probability of POI were demonstrated. Prophylactic lidocaine treatment was significantly associated with a reduced incidence of POI (OR = 0.25, 95% CI 0.11[ndash]0.56). Lidocaine treatment was also significantly associated with enhanced short-term survival (OR = 0.30, 95% CI 0.09[ndash]0.98). The variables associated with an increased risk of POI can be useful in identifying horses at risk of POI and in providing a more accurate prognosis. The results are supportive for lidocaine IV as an effective prokinetic treatment after small intestinal colic surgery.

Case of the Month - Feline Pemphigus

History
There are ulcerated lesions starting on ear margins, later involving lip margins and periocular area as well as neck. Pruritus started after ulcerated lesions appeared. Skin scraping - neg., DTM - neg., Cytology - PMN's and bacteria, C&S - pending, Dermohistopathology - pending, Bloodwork – normal. She is an outside cat, in a multicat household with no other pets involved. There are no external parasites, owner is not pruritic, no change in diet, on commercial pet food. Gave depo-medrol injection 10 days prior to biopsy. Expect biopsy results in 7 days.

Clinical Consultation
This consultation is based on our phone consultation, submitted history and clinical photos. Thank you for the clinical photos which were helpful. I agree with your suspicion that immune-mediated disease is most likely. Differential diagnoses would include: Erythema multiforme (drug-induced, paraneoplastic, idiopathic) and pemphigus foliaceus (drug-induced, paraneoplastic are possible causes). Lupus erythematosus less commonly occurs in cats so is considered less likely. A cutaneous drug reaction also appears less likely in this case given the cat’s lack of drug history (no medications were being administered prior to the onset of skin disease). Although severe allergic dermatitis can sometimes mimic immune-mediated disease in the cat, the severity of the clinical presentation also makes this less likely. I would also make sure to closely examine mucosal surfaces (perianal, oral)- mucosal surfaces are involved it could indicate vesicular auto-immune disease (pemphigus vulgaris, Stevens-Johnson Syndrome, epidermolysis bullosa acquisita). Immunosuppressive therapy will likely be required to control this disease process. Pending skin biopsies, I would recommend starting this cat on immunosuppressive doses of glucocorticoids (typically 2-3 mg/kg of Prednisolone [over prednisone] divided BID). I start to taper after there has been 75-80% improvement (often within 2 weeks). New lesions should not be developing & older lesions regressing. I would not recommend adding in an additional immunomodulatory agent at this time until after the biopsy results have been reviewed.

Additional follow-up is requested on this case: biopsy report, response to initial therapeutic recommendations, etc. Addendum comments and additional therapeutic recommendations can be made at that time.

Addendum
Per our phone conversation, the dermatopathology report is consistent with feline pemphigus foliaceus. Pemphigus foliaceus (PF) is a cutaneous auto-immune disease which most commonly occurs in middle aged to older cats. Another consideration would be paraneoplastic pemphigus; I would be suspicious of this if the skin lesions are not responding to appropriate therapy (this is typically more difficult to treat). Treatment for PF is often life-long, however some cats will go into extended periods of remission (without maintenance medications). Immunosuppressive therapy is required to control this disease. I recommend immunosuppressive doses of glucocorticoids (typically 2.2 mg/kg of Prednisolone [over prednisone] divided BID). I start to taper after there has been 75-80% improvement (often within 2 weeks). New lesions should not be developing & older lesions regressing. I often recommend a second immunosuppressive agent to control the disease and allow for lower doses of glucocorticoids to be used. Options include Chlorambucil or Atopica (Cyclosporine). Most commonly chlorambucil (0.1-0.2 mg/kg qd-qod) is used; tapered further over time. Monitor for myelosuppression. Obtain a baseline CBC, Chemistry profile & UA prior to initiating therapy. Recheck CBC values every 2 weeks for the first 6-8 weeks; then every 3-6 months. Although PF is often responsive to therapy, it can be a difficult auto-immune disease to manage. If remission is not initially achievable, I recommend referral to a veterinary dermatologist if possible.

Please contact me if this report is inconsistent with your clinical findings or you have additional questions. Please contact me at PetRays phone number listed below.

Terri Bonenberger, DVM
Diplomate, American College Veterinary Dermatology

3 week Update
The ulcerated lesions have healed and scabs have fallen off. The cat is doing very well.

Cool Recent Abstracts

American Journal of Veterinary Research
January 2009, Vol. 70, No. 1, Pages 99-104

Assessment of viremia associated with experimental primary feline herpesvirus infection or presumed herpetic recrudescence in cats

Hans D. Westermeyer, DVM, Sara M. Thomasy, DVM, PhD, Helen Kado-Fong, MS, David J. Maggs, BVSc

Objective—To detect feline herpesvirus type 1 (FHV-1) in blood of cats undergoing experimental primary herpetic disease or with spontaneous disease presumed to be caused by FHV-1 reactivation.

Animals—6 young specific-pathogen–free (SPF) cats and 34 adult cats from a shelter.

Procedures—Conjunctiva and nares of SPF cats were inoculated with FHV-1, and cats were monitored for 21 days. Periodically, blood was collected for CBC, serum biochemical analyses, and detection of FHV-1 DNA via PCR assay. For shelter cats, a conjunctival swab specimen was collected for FHV-1 PCR assay, and blood mononuclear cells were tested via virus isolation (with or without hydrocortisone) and FHV-1 PCR assay.

Results—All SPF cats developed clinical and clinicopathologic evidence of upper respiratory tract and ocular disease only. Via PCR assay, FHV-1 DNA was detected in blood of all SPF cats at least once between 2 and 15 days after inoculation. Feline herpesvirus type 1 DNA was detected in conjunctival swabs of 27 shelter cats; 25 had clinical signs of herpetic infection. However, virus was not isolated from mononuclear cell samples of any shelter cat regardless of passage number or whether hydrocortisone was present in the culture medium; FHV-1 DNA was not detected in any mononuclear cell sample collected from shelter cats.

Conclusions and Clinical Relevance—A brief period of viremia occurred in cats undergoing primary herpetic disease but not in cats undergoing presumed recrudescent herpetic disease. Viremia may be important in the pathogenesis of primary herpetic disease but seems unlikely to be associated with recrudescent disease.

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American Journal of Veterinary Research
January 2009, Vol. 70, No. 1, Pages 16-22

Evaluation of the distribution of enrofloxacin by circulating leukocytes to sites of inflammation in dogs

D. M. Boothe, DVM, PhD, A. Boeckh, DVM, PhD, H. W. Boothe, DVM, MS

Objective—To determine the effect of WBC accumulation on the concentration of enrofloxacin in inflamed tissues in dogs.

Animals—6 adult Bloodhounds.

Procedures—Dogs were instrumented bilaterally with tissue chambers. Peripheral WBCs collected from each dog were exposed in vitro to radiolabeled enrofloxacin (14C-ENR). Inflammation was induced with carrageenan in 1 chamber. Ten hours later, treated cells were administered IV to each dog such that 14C-ENR was delivered at a mean ± SD dosage of 212 ± 43 μg. Samples of extracellular fluid from inflammation and control chambers and circulating blood were then collected before (baseline) and for 24 hours after WBCs were administered. Samples were centrifuged to separate WBCs from plasma (blood) or chamber fluid. Radiolabeled enrofloxacin was scintigraphically detected and pharmacokinetically analyzed. Comparisons were made between extra- and intracellular chamber fluids by use of a Student paired t test.

Results—14C-ENR was not detectable in plasma, peripheral WBCs, control chambers, or baseline samples from inflammation chambers. However, 14C-ENR was detected in extra- cellular fluid from inflammation chambers (mean ± SD maximum concentration, 2.3 ± 0.5 ng/mL) and WBCs (maximum concentration, 7.7 ± 1.9 ng/mL). Mean disappearance half-life of 14C-ENR from extracellular fluid and WBCs from inflammation chambers was 26 ± 10 hours and 17 ± 6 hours, respectively.

Conclusions and Clinical Relevance—WBCs were responsible for the transport and release of 14C-ENR at sites of inflammation. Accumulation of drug by WBCs might increase the concentration of drug at the site of infection, thus facilitating therapeutic success.

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Veterinary Patholology 46:63-70 (2009)


Feline Gastrointestinal Eosinophilic Sclerosing Fibroplasia

L. E. Craig, E. E. Hardam, D. M. Hertzke, B. Flatland, B. W. Rohrbach and R. R. Moore

A retrospective study of cases of a unique intramural inflammatory mass within the feline gastrointestinal tract was performed in order to describe and characterize the lesion. Twenty-five cases were identified from archival surgical and postmortem tissues. The lesion most often occurred as an ulcerated intramural mass at the pyloric sphincter (n = 12) or the ileocecocolic junction or colon (n = 9); the remaining cases were in the small intestine. Seven cases also had lymph node involvement. The lesions were characterized by eosinophilic inflammation, large reactive fibroblasts, and trabeculae of dense collagen. Intralesional bacteria were identified in 56% of the cases overall and all of the ileocecocolic junction and colon lesions. Fifty-eight percent of cats tested had peripheral eosinophilia. Cats treated with prednisone had a significantly longer survival time than those receiving other treatments. We propose that this is a unique fibroblastic response of the feline gastrointestinal tract to eosinophilic inflammation that in some cases is associated with bacteria. The lesion is often grossly and sometimes histologically mistaken for neoplasia.

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Journal of Veterinary Internal Medicine
Volume 23 Issue 1, Pages 43 - 49

Clinical Evaluation of a Novel Liquid Formulation of L-Thyroxine for Once Daily Treatment of Dogs with Hypothyroidism

G. Le Traon 1 , S.F. Brennan 2 , S. Burgaud 1 , S. Daminet 3 , K. Gommeren 3 , L.J.I. Horspool 4 , D. Rosenberg 5 , and C.T. Mooney 2

Background: A liquid solution of levothyroxine (L-T4) is available for treatment of canine hypothyroidism.

Hypothesis: Once daily oral administration of a liquid L-T4 solution is effective and safe for controlling hypothyroidism in dogs.

Animals: Thirty-five dogs with naturally occurring hypothyroidism.

Methods: Dogs received L-T4 solution PO once daily at a starting dosage of 20 μg/kg body weight (BW). The dose was adjusted every 4 weeks, based on clinical signs and peak serum total T4 (tT4) concentrations. Target peak serum tT4 and thyroid stimulating hormone (TSH) concentrations, 4–6 hours posttreatment, were 35–95 nmol/L and < 0.68 ng/mL, respectively. Dogs were followed for up to 22 weeks after establishment of the maintenance dose.

Results: Clinical signs of hypothyroidism improved or resolved in 91% of dogs after 4 weeks of L-T4 treatment at 20 μg/kg once daily. The maintenance dose was established in 76, 94, and 100% of dogs after 4, 8, and 12 weeks of treatment, respectively. This was 20 μg L-T4/kg BW for 79% of the dogs, 30 μg/kg BW for 15%, and 10–15 μg/kg BW in the remaining 6%, once daily. Thereafter, median peak tT4 and TSH concentrations were 51 nmol/L and 0.18 ng/mL, respectively, and remained stable during the 22-week follow-up; clinical signs did not recur.

Conclusions and Clinical Importance: All of the hypothyroid dogs had rapid clinical and hormonal responses to supplementation with the PO-administered L-T4 solution. The starting dosage of 20 μg L-T4/kg BW once daily was suitable for 79% of dogs.

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Journal of Small Animal Practice
Volume 50 Issue 1, Pages 9 - 14

Radiographic appearance of cardiogenic pulmonary oedema in 23 cats

L. Benigni, N. Morgan* C. R. Lamb

Objective: To describe the radiographic appearance of pulmonary oedema in cats with cardiac failure.

Methods: Thoracic radiographs of 23 cats presented to a first opinion practice with signs of cardiac failure were reviewed. All cats had tachypnoea and/or dyspnoea and enlarged left atrium on echocardiography.

Results: Pulmonary oedema was characterised radiographically by an increased opacity associated with a range of patterns and variable distribution. All cats had evidence of a reticular or granular interstitial pattern. This occurred in combination with alveolar pattern in 19 (83 per cent) cats, including six with air bronchograms, with increased diameter of pulmonary vessels in 16 (71 per cent) cats and with bronchial pattern in 14 (61 per cent) cats. The distribution of pulmonary oedema was considered to be diffuse/non-uniform in 14 (61 per cent) cats, diffuse/uniform in four (17 per cent) cats, multi-focal in four (17 per cent) cats and focal in the remaining one (4 per cent). Nine (39 per cent) cats were considered to have a regional distribution of oedema, including five (22 per cent) with a ventral distribution, three (13 per cent) with a caudal distribution and one (4 per cent) cat with a hilar distribution. The distribution of pulmonary opacities was bilaterally symmetrical in five (22 per cent) cats.

Clinical Significance: The variable appearance of feline pulmonary oedema is likely to complicate its radiographic diagnosis.

Does Ultrasound Miss Abdominal Lesions?

Of course it does. But big question is how often? Are some findings more or less reliable?

An interesting article in the recent JAAHA looks at the correlation of abdominal ultrasound findings with gross surgical exploration. Whenever I have access to the ex lap findings of a patient undergoing an explore after one of my ultrasounds, I am anxious to find out how my findings compare. We all fear a negative explore, although almost every patient I can think of who had a negative gross explore, had microscopic lesions that were helpful in patient management. Following up on the ultrasound findings is an essential part of the learning process for anyone performing ultrasound or ordering one for their patient.

This was a retrospective study looking at cases from The Queen Mother Hospital for Animals in the UK. The ultrasounds were performed by experienced radiologists or radiology residents. They looked at 100 cases who had an ex lap within 48 hours of an abdominal ultrasound. There were only 19 cats, so one has wonder whether this was an adequate sample size for this particular species. There were no stats looking at cats versus dogs. However, they did note that there was “no apparent relationship…detected between body size of animal and the sensitivity of ultrasound for the primary lesion.” I find cats much easier to ultrasound than similarly-sized dogs (perhaps that is my bias towards this fabulous species), but I do feel this is a weakness in the study.

Their results are similar to what I have found in my clinical practice:

100 primary lesions & 67 secondary lesions were found at surgery.

Ultrasound did not detect the primary lesion in 24 of these animals and secondary lesions in 11 animals.

“A total of 36 animals [out of 100] had discordant ultrasonographic and surgical findings of their primary and secondary lesions.”

Ultrasound detected peritonitis lesions in 89% of cases.

Ultrasound detected intestinal obstruction in 64% of cases.

Ultrasound detected hepatic or splenic nodules in 63% of cases.

GI lesions were most likely to be missed by ultrasound (perforations, ulcerations) followed by organomegaly.

Although not statistically significant, ultrasound missed 5 GI foreign bodies.

Gross visualization at surgery missed some lesions seen on ultrasound - prostatic cysts, renal lesions, bladder lesions, splenic/liver lesions, and a gall bladder polyp.

This study brings to light my own experience.

If I am presented with a persistently vomiting animal with radiographs that are very suspicious for a GI obstruction but my ultrasound findings do not suggest obstruction - I ALWAYS err on the side of suspecting obstruction. Depending on the status of the animal and the level of suspicion from the radiographs, the next step may be to continue supportive care and repeat rads in 6-12 hours or it may be an exploratory laparotomy. My own cat had a negative explore and a number of my patients have as well. We have always learned something from the biopsies obtained and I have been fortunate to never have an owner be angry about it. The possibility of a negative explore is an important part of my conversation with the owner prior to surgery.

When ultrasound is used as part of check for metastasis, again, I always warn owners that we may be missing something. Ultrasound is notoriously poor at seeing all lesions in a liver or spleen. It may miss a focal intestinal lesion. I cannot count how many times over the course of my residency that Mike Willard showed me pictures of horrid livers at laparoscopy that were deemed normal by very experienced radiologists. Likewise, as was seen in this study, ultrasound may be able to detect architectural irregularities in an organ (especially liver, spleen, kidney) that are not seen on the surface of the organ at surgery. In these cases, a biopsy of a “normal” organ may reveal significant pathology.

This is why I am an annoyance to the surgeons when they explore the abdomens of my patients. Ultrasound is so subjective. It helps to have the objective look at surgery (or necropsy) to verify what I have seen. I am quick to recommend surgery (unless it would be detrimental to the patient) when I have any doubt about what I am seeing with ultrasound or if the animal’s signs are worse than expected based on ultrasound. Until we get a hold of one of Dr. Crusher’s tricorders, we’re stuck with histopathology for a diagnosis in many patients.

Jennifer S. Fryer, DVM

www. veterinaryanswers.com

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Introduction to Veterinary Answers, LLC

Veterinary Answers is a phone, fax, and email consultation service provided by specialist veterinarians to assist general practice veterinarians with their cases and practice. Our goal is to provide veterinarians with the information that will allow them to refer fewer patients and provide the highest standard of care available. We provide this service to licensed veterinarians only.

In addition to assistance with individual cases, we also provide article searches, we will set up hospital protocols for infection control or commonly encountered diseases, and answer any question you have in small animal veterinary medicine.

In this blog, we will review current literature and provide our assessment of recent articles that bring up clinically relevant or controversial topics.

Contact us with your questions or comments.
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Managing Twins in the Mare

By C. Scott Bailey, DVM, Dipl. ACT

Although twinning in the horse is a well-described condition academically, it remains a topic for which most horse-owners and many veterinarians feel inadequately prepared. Historically, twinning has been the most common cause of mid- to late-term pregnancy loss in mares; this is because the equine placenta requires a large surface area (the entire uterus) to supply sufficient oxygen and nutrients to the developing fetus in late gestation. Even a relatively small decrease in surface area will result in growth- retardation and a smaller and less thrifty foal at birth.

Physiologically, twins are most often the product of 2 asynchronous ovulations in a single cycle, which may be up to 5 days apart in the mare. For the first 16 days both developing embryos will be propelled around the uterus either adjacent to each other or separately, and they will then become fixed by muscular contraction between 16 and 17 days. In 80% of cases, the embryos are fixed together at the base of one horn, and in 20% of cases, they are each fixed in separate horns. In the latter case, there is no competition for nutrients in early gestation and the vast majority of cases result in late-term abortion. However, if the embryos are adjacent to each other, they may undergo spontaneous regression (70%) by day 40. Overall, in one study 64% of naturally occurring twins were found to undergo spontaneous regression, most before day 26. The likelihood of spontaneous reduction decreased thereafter until day 40. After day 40, 90% of twins will result in late-term pregnancy failure, either in the form of abortion of both fetuses, stillbirth and stunting of term foals or dystocia.

Despite the high rate of pregnancy failure in mares carrying twins, the incidence of double-ovulations is high (20%) is some breeds. The very act of reducing twins results in increased numbers of horses that carry the genetic propensity for twinning. Likewise, inducing ovulation with exogenous hormones also increases the likelihood of double-ovulations. As a result, the use of ultrasound for early pregnancy diagnosis has become routine for many equine practitioners. At this stage, reduction of pregnancy by “pinching” one embryonic vesicle can be performed reliably and safely. This procedure is generally performed around 14-15 days of gestation – a time at which embryonic vesicles are readily detectable and are still mobile in the uterus, making it possible to move one embryo to the tip of a horn by manual trans-rectal manipulation. Once the vesicle is separated adequately from the remaining embryo, and is at the tip of a horn it can be “pinched” manually or with the ultrasound. This procedure has a 90-95% success-rate when performed by a skilled practitioner and can be performed early in pregnancy, at a time in which re-breeding the mare is possible if the procedure results in the loss of both embryos.

After this critical window, success-rates for various reduction methods are low. Between 17 and 26 days natural reduction with or without the benefit of energy deprivation by eliminating grain-based feed may be the most effective means of eliminating one twin. However, if twins are still identified after day 30, another means of reduction should be selected. Allowing the pregnancy to continue beyond day 35 will result in the development of endometrial cups and a loss of the remaining-breeding season if pregnancy is lost subsequently. Therefore, trans-vaginal ultrasound-guided twin reduction may be attempted at this time. A 5 - 7.5 MHz vaginal ultrasound probe with a needle-guide is used to visualize one embryo, which is held adjacent to the probe with one hand in the rectum. The needle is then punctured through the vaginal wall and uterus, and the fetal fluids are aspirated aggressively. This technique has been reported with a 30% success-rate for the production of one live foal in the case of unilateral twins, and up to 70% success-rate for the production of one live foal in the case of bilateral twins when performed between 30 and 36 days.

After 35-36 days of pregnancy, two procedures have been described for selective reduction of one twin.

Most recently, cranio-cervical dislocation of one fetus has been described by a practitioner in central Kentucky. While not widely available, this technique has been demonstrated to carry a relatively high success-rate of >60%. It can be performed trans-rectally or surgically by flank laparotomy, and has been described between 60 and 110 days. At this stage of gestation, the gender of each fetus can be determined, and the fetus is selected for reduction based on both gender and location in the uterus. In addition, this procedure can be performed before complete development of the placenta and may have a higher success-rate than later procedures due to the ability of the remaining fetus to form a fully functional placenta.

Alternatively, ultrasound-guided trans-abdominal cardiac puncture has been well-described in the literature, with a success-rate around 50%. For this procedure, the fetuses are identified by trans-abdominal ultrasound after sedation of the mare and one fetus is injected with KCl or procaine penicillin by intra-cardiac puncture using a spinal needle. The success of this procedure is operator-dependent, but is less invasive than the surgical procedure described above and requires little equipment other than a 3.5 MHz curvilinear probe. It is best performed between 115 and 130 days of gestation and as for the procedure above, both location and fetal gender may be used as criteria for selection. It should be noted that this procedure may result in the birth of a small and unthrifty foal. This is likely due to the fact that the placenta is largely developed by 120 days and the area of placenta which opposes that of the reduced twin remains unavailable for nutrient transfer for the remainder of gestation.

When all other procedures fail to achieve the goal of one developing fetus, abortion of both conceptuses is the single remaining option. Due to the risk of dystocia and periparturient complications to the mare and the low chance of achieving two live foals (1- 2%), allowing the pregnancy to be maintained naturally cannot be recommended. Chemical abortion can easily be achieved before formation of the endometrial cups (36-40 days) with a single dose of prostaglandin or prostaglandin analog, but may require multiple doses of a prostaglandin/ prostaglandin analog and/or oxytocin in later gestation. At this time, abortion should be performed in a hospital-setting, where the mare can be monitored carefully and where parturition can be attended.

Thus, while twins undoubtedly constitute a significant risk to equine pregnancy, there are many methods of managing them successfully. Indeed, the common use of ultrasound for early pregnancy diagnosis has been so successful that many practitioners now feel that double-ovulations are actually of benefit, because they increase the likelihood of fertilization and because any twins can readily be managed early in gestation.

References

Ginther OJ. Twin embryos in the mare: 1. From ovulation to fixation. Equine Vet J 1989; 21:166-70

Leadon DP, Rossdale PD, Jeffcot LB et al. A comparison of agents for inducing parturition in mares in the pre-viable and premature periods of gestation. J Reprod Fertil Suppl 1982; 32: 597-602

Macpherson ML, Homco LD, Varner DD. Transvaginal ultrasound-guided allantocentesis for pregnancy elimination in the mare Biol Reprod Monogr 1995; 1: 215-223

Rantanen NW, Kincaid B. Ultrasound guided fetal cardiac puncture. A method of twin reduction in the mare. Proc Am Assoc Equine Pract 1988; 34:173-79

Wolfsdorf KE. Management of postfixation Twins in Mares. Vet Clin Equine 2006; 22: 713-725