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ACVIM practice questions

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Question 1Cardiology

Which heart valve separates the left atrium from the left ventricle?

  1. Mitral valve Correct answer.
  2. Aortic valve
  3. Pulmonic valve
  4. Tricuspid valve

Explanation

The mitral (left atrioventricular) valve guards the ostium between the left atrium and left ventricle. The tricuspid valve is the right atrioventricular valve, and the semilunar valves sit at the ventricular outflow tracts.

Question 2Cardiology

A dog presents with severe weakness, and ECG shows a regular rhythm at about 40 beats/min with narrow QRS complexes and no visible P waves before most QRS complexes. Which rhythm is most likely?

  1. Ventricular tachycardia
  2. Atrial fibrillation
  3. Atrial standstill Correct answer.
  4. Sinus bradycardia

Explanation

Absent P waves with a slow, regular, narrow-complex escape rhythm suggests failure of atrial depolarization, as in atrial standstill. Atrial fibrillation would be irregularly irregular, and ventricular tachycardia would produce wide complexes at a fast rate.

Question 3Cardiology

Which ECG finding is the hallmark of complete (third-degree) atrioventricular block?

  1. Progressive PR prolongation until a QRS is dropped
  2. A shortened PR interval with a delta wave
  3. Intermittent dropped QRS complexes with constant PR interval
  4. Complete absence of any relationship between P waves and QRS complexes Correct answer.

Explanation

In third-degree AV block, atrial and ventricular activation are independent (AV dissociation), so P waves and QRS complexes bear no fixed relationship. The ventricular escape rhythm is typically slow and regular.

Question 4Cardiology

A cat with hypertrophic cardiomyopathy is started on a beta-blocker. What is the primary therapeutic goal of this drug class in this disease?

  1. Vasodilate to reduce afterload
  2. Increase contractility to improve cardiac output
  3. Reduce dynamic outflow obstruction and myocardial oxygen demand Correct answer.
  4. Promote diuresis to relieve pulmonary edema

Explanation

Beta-blockers slow heart rate and reduce contractility, which lessens dynamic left ventricular outflow tract obstruction and lowers myocardial oxygen demand in hypertrophic cardiomyopathy. They do not increase contractility or provide diuresis.

Question 5Cardiology

Which finding on physical examination is most consistent with a large left-to-right patent ductus arteriosus in a young dog?

  1. A systolic murmur that varies with respiration
  2. A continuous machinery murmur loudest at the left base Correct answer.
  3. A diastolic murmur loudest at the right base
  4. A holosystolic murmur loudest at the left apex

Explanation

A PDA produces continuous flow from the high-pressure aorta into the lower-pressure pulmonary artery throughout systole and diastole, generating a continuous machinery murmur at the left base. Other murmurs described are not characteristic of ductal flow.

Question 6Cardiology

A dog has a systolic murmur, and echocardiography shows a high-velocity jet across the pulmonic valve in systole. Which congenital defect is present?

  1. Ventricular septal defect
  2. Tricuspid dysplasia
  3. Pulmonic stenosis Correct answer.
  4. Aortic stenosis

Explanation

Pulmonic stenosis causes turbulent systolic flow across the narrowed valve, producing a high-velocity systolic jet on Doppler echocardiography. Aortic stenosis would show a systolic jet at the aortic valve, and a VSD a jet across the septum.

Question 7Cardiology

Which echocardiographic measurement is used to estimate left atrial enlargement relative to the aorta in dogs?

  1. E-point septal separation
  2. Fractional shortening
  3. Left atrium-to-aorta ratio Correct answer.
  4. Tei index

Explanation

The left atrium-to-aorta ratio compares left atrial dimension to aortic dimension and is used to assess left atrial enlargement. Fractional shortening reflects systolic function, and E-point septal separation reflects ventricular dilation.

Question 8Cardiology

A dog in congestive heart failure from degenerative mitral valve disease is treated with furosemide. Which parameter should be monitored most directly to gauge the diuretic response?

  1. Serum potassium alone
  2. Resting respiratory rate and body weight Correct answer.
  3. Serum creatinine alone
  4. Packed cell volume alone

Explanation

Resolution of pulmonary edema is reflected by a decline in resting respiratory rate, and body weight tracks fluid loss. These are practical bedside endpoints for diuretic titration. Renal values and electrolytes are monitored for adverse effects but do not measure edema resolution.

Question 9Cardiology

Which of the following is the most common acquired cardiac disease in dogs?

  1. Hypertrophic cardiomyopathy
  2. Pericardial effusion
  3. Dilated cardiomyopathy
  4. Degenerative mitral valve disease Correct answer.

Explanation

Degenerative (myxomatous) mitral valve disease is the most common acquired cardiac disorder in dogs, especially small breeds. Dilated cardiomyopathy occurs but is less common overall, and hypertrophic cardiomyopathy is primarily a feline disease.

Question 10Cardiology

A cat with hypertrophic cardiomyopathy presents with acute hindlimb paralysis and cold, painful limbs. Which complication is most likely?

  1. Intervertebral disc extrusion
  2. Aortic thromboembolism Correct answer.
  3. Septic arthritis
  4. Pulmonary thromboembolism

Explanation

Cats with hypertrophic cardiomyopathy are predisposed to left atrial enlargement and thrombus formation, with thrombi embolizing to the aortic trifurcation and causing acute hindlimb ischemia. The cold, pulseless limbs and acute onset fit this diagnosis.

Question 11Cardiology

Which drug is the first-line positive inotrope of choice for short-term management of acute systolic heart failure in dogs?

  1. Atenolol
  2. Sotalol
  3. Diltiazem
  4. Pimobendan Correct answer.

Explanation

Pimobendan is a calcium sensitizer and phosphodiesterase III inhibitor that increases contractility and provides vasodilation, making it useful in systolic dysfunction. Beta-blockers and calcium channel blockers reduce contractility and are not inotropes.

Question 12Cardiology

A dog is diagnosed with dilated cardiomyopathy. Which echocardiographic finding is most characteristic?

  1. Increased left ventricular wall thickness with hyperdynamic function
  2. Concentric hypertrophy with a small ventricular cavity
  3. Normal chamber size with a thickened septum
  4. Increased left ventricular internal dimension with reduced fractional shortening Correct answer.

Explanation

Dilated cardiomyopathy is characterized by chamber dilation and reduced systolic function, so left ventricular internal dimensions are increased and fractional shortening is decreased. Hypertrophic patterns describe a different disease.

Question 13Cardiology

Which of the following is a recognized cause of pericardial effusion in dogs that must be considered when hemorrhagic fluid is found?

  1. Patent ductus arteriosus
  2. Right atrial hemangiosarcoma Correct answer.
  3. Mitral valve prolapse
  4. Pulmonic stenosis

Explanation

Right atrial hemangiosarcoma is a common neoplastic cause of hemorrhagic pericardial effusion in dogs, along with idiopathic pericarditis and chemodectoma. The other listed conditions do not typically produce hemorrhagic effusion.

Question 14Cardiology

A dog with pericardial effusion shows electrical alternans on ECG and muffled heart sounds. Which hemodynamic abnormality is most likely?

  1. Left-to-right shunting
  2. Cardiac tamponade Correct answer.
  3. High-output failure
  4. Aortic regurgitation

Explanation

Accumulated pericardial fluid raises intrapericardial pressure and impairs ventricular filling, producing cardiac tamponade with pulsus paradoxus and electrical alternans. Shunting and regurgitant lesions do not cause these findings.

Question 15Cardiology

Which electrolyte abnormality most strongly predisposes to cardiac arrhythmias in a dog receiving long-term furosemide therapy?

  1. Hypernatremia
  2. Hypochloremia
  3. Hypokalemia Correct answer.
  4. Hypercalcemia

Explanation

Loop diuretics increase renal potassium loss, and hypokalemia predisposes to ventricular and atrial arrhythmias. Potassium should be monitored and supplemented as needed during chronic diuretic therapy.

Question 16Cardiology

A dog has a systolic murmur and echocardiography demonstrates a jet from the left ventricle into the right ventricle. Which defect is present?

  1. Atrial septal defect
  2. Ventricular septal defect Correct answer.
  3. Tricuspid atresia
  4. Patent ductus arteriosus

Explanation

A ventricular septal defect produces left-to-right flow across the interventricular septum, creating a systolic jet into the right ventricle. An atrial septal defect shunts at the atrial level, and a PDA shunts from aorta to pulmonary artery.

Question 17Cardiology

Which of the following best describes the mechanism by which pimobendan improves cardiac output?

  1. Beta-adrenergic receptor blockade
  2. Pure arterial vasoconstriction
  3. Calcium channel blockade
  4. Positive inotropy with vasodilation Correct answer.

Explanation

Pimobendan increases myocardial contractility through calcium sensitization and phosphodiesterase III inhibition while also causing vasodilation, an inodilator effect. It does not block calcium channels or beta receptors.

Question 18Cardiology

A cat presents with acute dyspnea, and thoracic radiographs show a small heart silhouette with enlarged caudal lobar arteries and patchy alveolar infiltrates. Which condition should be prioritized?

  1. Pleural effusion from right-sided failure
  2. Dirofilariasis with pulmonary thromboembolism Correct answer.
  3. Hypertrophic cardiomyopathy with left-sided failure
  4. Feline asthma

Explanation

A small heart with enlarged pulmonary arteries and patchy infiltrates in a dyspneic cat raises concern for heartworm-associated pulmonary thromboembolism. Hypertrophic cardiomyopathy typically enlarges the heart, and asthma does not enlarge pulmonary arteries.

Question 19Cardiology

Which antiarrhythmic is most appropriate for rate control in a dog with rapid, hemodynamically stable atrial fibrillation?

  1. Lidocaine
  2. Epinephrine
  3. Diltiazem Correct answer.
  4. Atropine

Explanation

Diltiazem slows AV nodal conduction to control ventricular rate in atrial fibrillation. Lidocaine is used for ventricular arrhythmias, and atropine and epinephrine would increase heart rate.

Question 20Cardiology

Which congenital defect in dogs is characterized by a systolic murmur at the left base with weak femoral pulses and a history of exercise intolerance?

  1. Tricuspid regurgitation
  2. Mitral stenosis
  3. Aortic stenosis Correct answer.
  4. Atrial septal defect

Explanation

Aortic stenosis causes a systolic ejection murmur at the left base and may reduce cardiac output, producing weak pulses and exercise intolerance. Mitral stenosis is rare in dogs, and tricuspid regurgitation causes a right-sided murmur.

Question 21Cardiology

A dog with right-sided congestive heart failure has severe ascites and pleural effusion. Which combination of findings is most consistent with this condition?

  1. Systolic murmur at the left apex and crackles
  2. Jugular venous distension and hepatomegaly Correct answer.
  3. Weak pulses and pale mucous membranes
  4. Pulmonary edema and orthopnea

Explanation

Right-sided failure raises central venous pressure, producing jugular venous distension and hepatic congestion with hepatomegaly, along with cavitary effusions. Pulmonary edema and orthopnea reflect left-sided failure.

Question 22Cardiology

A dog with degenerative mitral valve disease has a murmur but no clinical signs, normal chamber dimensions, and normal blood pressure. What is the most appropriate management?

  1. Start furosemide immediately
  2. Begin pimobendan at the first murmur
  3. Perform pericardiocentesis
  4. Monitor and reassess periodically without diuretics Correct answer.

Explanation

Asymptomatic dogs with mild disease and normal cardiac dimensions do not require diuretics; periodic monitoring allows detection of progression. Diuretics in a euvolemic patient risk volume depletion and do not improve outcome.

Question 23Cardiology

Which ECG change is most characteristic of hyperkalemia in a dog with urinary obstruction?

  1. Delta waves with a short PR interval
  2. Prominent U waves with a prolonged QT interval
  3. Sawtooth flutter waves
  4. Tall, peaked T waves with widened QRS complexes Correct answer.

Explanation

Hyperkalemia decreases the resting membrane potential and slows conduction, producing tall peaked T waves and widened QRS complexes that can progress to sine-wave patterns. U waves and flutter waves are not typical of hyperkalemia.

Question 24Cardiology

A dog with a large patent ductus arteriosus is at risk for which long-term complication if left uncorrected?

  1. Left-sided volume overload and congestive heart failure Correct answer.
  2. Pericardial effusion
  3. Right-to-left shunting with cyanosis at birth
  4. Complete heart block

Explanation

Chronic left-to-right shunting through a PDA overloads the left heart with volume and can lead to left-sided congestive heart failure. Right-to-left shunting develops only when pulmonary vascular resistance exceeds systemic resistance, which is a late change.

Question 25Cardiology

A dog with a suspected arrhythmogenic cardiomyopathy has frequent ventricular premature complexes on ECG. Which antiarrhythmic is commonly used for ventricular arrhythmias in dogs?

  1. Digoxin
  2. Sotalol Correct answer.
  3. Furosemide
  4. Atenolol

Explanation

Sotalol combines beta-blockade with class III potassium channel blockade and is used to suppress ventricular arrhythmias. Digoxin is used for supraventricular rate control, and furosemide is a diuretic.

Question 26Cardiology

Which echocardiographic finding is most consistent with a diagnosis of hypertrophic cardiomyopathy in a cat?

  1. Large left atrial appendage thrombus without ventricular hypertrophy
  2. Segmental or diffuse left ventricular wall thickening with diastolic dysfunction Correct answer.
  3. Dilated left ventricle with reduced systolic function
  4. Thin left ventricular free wall with systolic anterior motion of the mitral valve

Explanation

Hypertrophic cardiomyopathy is defined by unexplained left ventricular hypertrophy, typically with diastolic dysfunction and often systolic anterior motion of the mitral valve. Dilatation with reduced systolic function characterizes dilated cardiomyopathy, not hypertrophic cardiomyopathy.

Question 27Cardiology

Which of the following is the most common congenital cardiac defect in dogs?

  1. Patent ductus arteriosus Correct answer.
  2. Ventricular septal defect
  3. Aortic stenosis
  4. Pulmonic stenosis

Explanation

Patent ductus arteriosus is consistently reported as the most common congenital cardiac anomaly in dogs, followed by pulmonic stenosis and aortic stenosis. Ventricular septal defect is also seen but is less common.

Question 28Cardiology

A dog with chronic degenerative mitral valve disease is receiving furosemide and an ACE inhibitor. Which parameter is most useful for monitoring the adequacy of diuretic therapy at home?

  1. Appetite
  2. Heart rate
  3. Sleeping respiratory rate Correct answer.
  4. Body temperature

Explanation

Sleeping respiratory rate is a sensitive and practical marker of pulmonary congestion in dogs with heart failure; an increase suggests worsening congestion. Heart rate, body temperature, and appetite are less specific for fluid status.

Question 29Cardiology

A dog presents with weakness and collapse. ECG shows a regular rhythm at 40 beats per minute with a P wave preceding each QRS complex and a normal QRS morphology. Which condition is most likely?

  1. Atrial fibrillation
  2. Ventricular tachycardia
  3. Sinus bradycardia Correct answer.
  4. Third-degree atrioventricular block

Explanation

A slow regular rhythm with a consistent P wave before each QRS and normal QRS indicates sinus bradycardia. Third-degree AV block would show P waves not consistently related to QRS complexes, and atrial fibrillation would lack organized P waves.

Question 30Cardiology

Which of the following is the most appropriate initial treatment for a dog with acute cardiogenic pulmonary edema due to congestive heart failure?

  1. Calcium channel blocker administration
  2. Furosemide and oxygen supplementation Correct answer.
  3. Beta-blocker administration
  4. Fluid therapy with crystalloids

Explanation

Acute cardiogenic pulmonary edema is treated with oxygen support and intravenous furosemide to reduce volume overload. Fluids would worsen congestion, and beta-blockers or calcium channel blockers are not first-line for acute edema.

Question 31Cardiology

A dog is diagnosed with systemic hypertension. Which of the following is the most common target organ damage associated with systemic hypertension in dogs?

  1. Tricuspid valve dysplasia
  2. Left ventricular hypertrophy Correct answer.
  3. Pulmonary artery rupture
  4. Right ventricular hypertrophy

Explanation

Chronic systemic hypertension increases left ventricular afterload, leading to concentric left ventricular hypertrophy. Right ventricular hypertrophy, pulmonary artery rupture, and tricuspid dysplasia are not typical consequences of systemic hypertension.

Question 32Cardiology

A 10-year-old dog with a history of degenerative mitral valve disease presents with acute onset of dyspnea. Thoracic radiographs show a large left atrium and pulmonary edema. Which of the following best explains the pathophysiology of the pulmonary edema?

  1. Lymphatic obstruction
  2. Increased pulmonary capillary hydrostatic pressure Correct answer.
  3. Reduced oncotic pressure due to hypoalbuminemia
  4. Decreased pulmonary capillary permeability

Explanation

In left-sided congestive heart failure, elevated left atrial pressure is transmitted to the pulmonary veins, increasing pulmonary capillary hydrostatic pressure and causing edema. Decreased permeability would not cause edema, and hypoalbuminemia or lymphatic obstruction are not the primary mechanisms here.

Question 33Cardiology

A dog with a large left-to-right shunting patent ductus arteriosus is at risk for which long-term complication if the defect is not corrected?

  1. Pulmonic stenosis
  2. Systemic hypertension
  3. Eisenmenger syndrome with reversal of shunt flow Correct answer.
  4. Aortic dissection

Explanation

Chronic left-to-right shunting increases pulmonary blood flow and can lead to pulmonary vascular disease and pulmonary hypertension, eventually causing reversal of shunt flow (Eisenmenger syndrome). Systemic hypertension, aortic dissection, and pulmonic stenosis are not typical long-term consequences.

Question 34Cardiology

A dog is receiving digoxin for management of heart failure. Which electrolyte abnormality most increases the risk of digoxin toxicity?

  1. Hypochloremia
  2. Hypernatremia
  3. Hyperkalemia
  4. Hypokalemia Correct answer.

Explanation

Hypokalemia enhances the binding of digoxin to the sodium-potassium ATPase and increases the risk of toxicity. Hyperkalemia, hypernatremia, and hypochloremia do not have this effect.

Question 35Large Animal Internal Medicine (LAIM)

A 6-year-old Quarter Horse gelding presents with lethargy, ventral edema, and weight loss. On auscultation there is a grade 4/6 holosystolic murmur over the mitral valve area. Which of the following findings is most consistent with left-sided congestive heart failure in this horse?

  1. Increased serum creatinine with oliguria
  2. Pulmonary crackles and frothy nasal discharge Correct answer.
  3. Hepatomegaly with a positive jugular pulsation test
  4. Jugular venous distension and pulsation

Explanation

In horses, left-sided congestive heart failure leads to pulmonary edema, which produces crackles and, in severe cases, frothy nasal discharge. Jugular distension, hepatomegaly, and ventral edema are features of right-sided failure. Renal azotemia is a consequence of reduced cardiac output rather than a specific marker of left-sided congestion.

Question 36Large Animal Internal Medicine (LAIM)

Which of the following best describes the mechanism by which hypocalcemia causes clinical signs in a periparturient dairy cow with milk fever?

  1. Reduced acetylcholine release at neuromuscular junctions and decreased muscle membrane excitability Correct answer.
  2. Increased sodium conductance across neuronal membranes causing hyperexcitability
  3. Competitive antagonism of calcium at the ryanodine receptor
  4. Direct inhibition of the sodium-potassium ATPase pump in skeletal muscle

Explanation

Ionized calcium is required for neurotransmitter release and normal membrane stability; hypocalcemia reduces acetylcholine release and lowers the threshold for tetany while also causing flaccid paresis in the classic recumbent presentation. The net clinical picture in milk fever is weakness and recumbency rather than hyperexcitability. The other options describe mechanisms not attributable to hypocalcemia.

Question 37Large Animal Internal Medicine (LAIM)

A dairy cow is suspected of having subacute ruminal acidosis. Which of the following is the most appropriate diagnostic indicator?

  1. Fecal pH above 7.0
  2. Urine pH above 8.0
  3. Ruminal pH below 6.5 on rumen fluid from a stomach tube
  4. Ruminal pH below 5.8 on rumenocentesis Correct answer.

Explanation

Subacute ruminal acidosis is defined by a ruminal pH below approximately 5.8, and rumenocentesis provides the most reliable sample because orogastric tubing can be contaminated by saliva and alter pH. Fecal and urine pH are not diagnostic for SARA. Sampling via stomach tube tends to yield higher, less representative pH values.

Question 38Large Animal Internal Medicine (LAIM)

Which of the following is the most common cause of acute bovine laminitis?

  1. Prolonged grazing on lush pasture in winter
  2. Chronic selenium deficiency
  3. Infection with bovine viral diarrhea virus
  4. Grain overload with rapid production of lactic acid Correct answer.

Explanation

Carbohydrate overload from grain ingestion leads to ruminal lactic acidosis, which triggers systemic events including endotoxemia and vasoactive mediator release that result in laminitis. Selenium deficiency causes white muscle disease, not acute laminitis. BVDV and winter pasture grazing are not primary causes of acute laminitis.

Question 39Large Animal Internal Medicine (LAIM)

A horse presents with a swollen, painful parotid region and purulent nasal discharge. Endoscopy reveals purulent drainage from the pharyngeal orifice of the guttural pouch. Which of the following is the most likely diagnosis?

  1. Guttural pouch empyema Correct answer.
  2. Guttural pouch tympany
  3. Guttural pouch mycosis
  4. Ethmoid hematoma

Explanation

Guttural pouch empyema is characterized by accumulation of purulent exudate, often following strangles, and presents with parotid swelling and purulent nasal discharge. Tympany causes nonpainful swelling and respiratory noise in foals. Mycosis typically presents with epistaxis from the internal carotid artery. Ethmoid hematoma causes epistaxis without parotid swelling.

Question 40Large Animal Internal Medicine (LAIM)

A 3-day-old foal presents with lethargy, icterus, and hemoglobinuria. The foal is nursing well and the dam is healthy. Which of the following is the most likely diagnosis?

  1. Neonatal septicemia
  2. Equine herpesvirus-1 infection
  3. Neonatal isoerythrolysis Correct answer.
  4. Physiologic icterus of the newborn

Explanation

Neonatal isoerythrolysis results from ingestion of colostral antibodies directed against foal red blood cell antigens, causing immune-mediated hemolysis with icterus and hemoglobinuria. Septicemia typically produces fever, weakness, and other signs. EHV-1 in neonates causes severe respiratory and neurologic disease. Physiologic icterus is mild and does not cause hemoglobinuria.

Question 41Large Animal Internal Medicine (LAIM)

Which of the following is the treatment of choice for a horse with suspected botulism?

  1. Penicillin G at high doses
  2. Hyperimmune plasma transfusion
  3. Polyvalent botulinum antitoxin administration Correct answer.
  4. Corticosteroid therapy

Explanation

Botulism is treated with polyvalent antitoxin to neutralize circulating toxin before it binds to neuromuscular junctions. Antibiotics such as penicillin do not neutralize preformed toxin and may worsen toxin release. Hyperimmune plasma and corticosteroids are not established treatments for botulism.

Question 42Large Animal Internal Medicine (LAIM)

A cow is presented with a 'ping' on simultaneous auscultation and percussion over the left flank at the level of the paralumbar fossa. Which of the following is the most likely diagnosis?

  1. Right displaced abomasum
  2. Cecal dilatation
  3. Traumatic reticuloperitonitis
  4. Left displaced abomasum Correct answer.

Explanation

A ping over the left flank between the 9th and 13th ribs is characteristic of left displaced abomasum. Right displaced abomasum produces a ping on the right side. Cecal dilatation produces a ping in the right paralumbar fossa. Traumatic reticuloperitonitis produces pain and systemic signs without a left flank ping.

Question 43Large Animal Internal Medicine (LAIM)

A sheep flock has several animals with acute neurologic signs including circling, head pressing, and blindness. Postmortem examination reveals multifocal necrosis of the cerebral cortex with eosinophilic plaques. Which of the following is the most likely diagnosis?

  1. Polioencephalomalacia Correct answer.
  2. Pregnancy toxemia
  3. Listeriosis
  4. Coenurosis

Explanation

Polioencephalomalacia, often due to thiamine deficiency, causes cerebrocortical necrosis with characteristic laminar necrosis and eosinophilic plaques. Listeriosis typically causes microabscesses and cranial nerve deficits. Coenurosis causes space-occupying cysts. Pregnancy toxemia causes ketosis and hepatic lipidosis.

Question 44Large Animal Internal Medicine (LAIM)

Which of the following is the most appropriate initial treatment for a horse with acute equine grass sickness presenting with dysphagia and ileus?

  1. Immediate exploratory laparotomy
  2. High-dose corticosteroid therapy
  3. Supportive care with fluids, analgesia, and nutritional support Correct answer.
  4. Oral administration of prokinetics

Explanation

Equine grass sickness has no specific cure; treatment is supportive and prognosis is poor, so many cases are euthanized. Surgery is not therapeutic. Corticosteroids have not been shown to improve outcomes. Oral prokinetics are ineffective in the face of ileus and dysphagia.

Question 45Large Animal Internal Medicine (LAIM)

A cow with a history of chronic weight loss, diarrhea, and a 'pear-shaped' udder has a positive fecal culture for Mycobacterium avium subspecies paratuberculosis. Which of the following best describes the pathogenesis of Johne's disease?

  1. Acute hemorrhagic enteritis with toxin production
  2. Viral-induced villous blunting with crypt hyperplasia
  3. Chronic granulomatous enteritis with progressive villous atrophy and malabsorption Correct answer.
  4. Lymphoproliferative disease with neoplastic infiltration of the bowel

Explanation

Johne's disease causes chronic granulomatous enteritis with thickening of the ileum and villous atrophy, leading to malabsorption and protein-losing enteropathy. The other options describe acute enteritis, neoplasia, and viral enteropathy, none of which match the chronic granulomatous pattern of paratuberculosis.

Question 46Large Animal Internal Medicine (LAIM)

Which of the following findings is most consistent with a diagnosis of equine Cushing's disease (PPID)?

  1. Polyuria with low urine specific gravity and hypernatremia
  2. Hirsutism with delayed shedding and recurrent laminitis Correct answer.
  3. Weight loss with polyphagia and exophthalmos
  4. Hypertension with retinal detachment

Explanation

Equine PPID is characterized by hirsutism, delayed shedding, and laminitis in older horses, driven by hyperplasia of the pars intermedia. Weight loss with polyphagia and exophthalmos is more consistent with hyperthyroidism. Polyuria with dilute urine is more consistent with diabetes insipidus or renal disease. Hypertension with retinal detachment is not typical of PPID.

Question 47Large Animal Internal Medicine (LAIM)

A goat presents with acute onset of tremors, ataxia, and recumbency. The herd recently received a new batch of feed. Which of the following is the most likely diagnosis?

  1. Caprine arthritis-encephalitis
  2. Polioencephalomalacia
  3. Lead poisoning Correct answer.
  4. Listeriosis

Explanation

Lead poisoning causes acute neurologic signs including tremors, ataxia, blindness, and recumbency, and is often associated with contaminated feed or environmental exposure. Polioencephalomalacia is also a differential but typically responds to thiamine. CAE causes chronic arthritis and encephalitis in kids. Listeriosis causes cranial nerve deficits and circling.

Question 48Large Animal Internal Medicine (LAIM)

Which of the following is the most reliable method for diagnosing pregnancy in a mare at 14 days post-ovulation?

  1. Urine estrogen measurement
  2. Transabdominal palpation
  3. Serum progesterone measurement
  4. Transrectal ultrasonography Correct answer.

Explanation

Transrectal ultrasonography can detect the embryonic vesicle as early as 10-14 days post-ovulation and is the most reliable early pregnancy diagnostic. Serum progesterone is not reliable because the corpus luteum is maintained in both pregnant and nonpregnant mares. Urine estrogens are not useful at this stage. Transabdominal palpation is not feasible at 14 days.

Question 49Large Animal Internal Medicine (LAIM)

A dairy herd experiences an outbreak of acute mastitis with a 'hot' quarter, systemic signs, and a high somatic cell count. Culture reveals Gram-positive cocci in clusters. Which of the following is the most likely pathogen?

  1. Streptococcus agalactiae
  2. Klebsiella pneumoniae
  3. Escherichia coli
  4. Staphylococcus aureus Correct answer.

Explanation

Staphylococcus aureus is a Gram-positive coccus in clusters and a common cause of contagious mastitis with systemic signs. Streptococcus agalactiae is a Gram-positive coccus in chains and is also contagious but typically causes chronic subclinical mastitis. Escherichia coli and Klebsiella pneumoniae are Gram-negative organisms associated with environmental mastitis.

Question 50Large Animal Internal Medicine (LAIM)

A horse presents with a large, nonpainful swelling in the pectoral region that has been present for months. Fine-needle aspirate reveals adipocytes. Which of the following is the most likely diagnosis?

  1. Lipoma Correct answer.
  2. Sarcoma
  3. Melanoma
  4. Squamous cell carcinoma

Explanation

Lipomas are benign tumors of adipocytes and can occur in the pectoral region, though they are more commonly found in the mesentery. Melanomas are pigmented and typically occur in gray horses. Squamous cell carcinoma and sarcomas have different cytologic features. Fine-needle aspirate showing adipocytes supports lipoma.