DMN: practice questions (week 11)

CA GI surgery + splenectomy, PA abdominal surgeries, LA hernias, hindgut, CA colon + rectum diseases

Experimental studies of dogs with intestinal obstruction showed selective intestinal mucosal ischemia when intraluminal pressure was ______.

Higher than 40 mmHg

Vomiting in a dog with distal intestinal obstruction may result in _____________.

Metabolic acidosis

Which antibiotic is recommended for prophylactic use in surgery on the distal small + large intestine surgery?

Cefoxitin (second-generation cephalosporins)

-may also add a penicillin + a beta-lactamase inhibitor (ex: ampicillin + sublactam)

Which antibiotic is recommended for prophylactic use in surgery on the proximal (upper) + midintestinal surgery?

Cefazolin (first-generation cephalosporins)

What characteristic is not used for assessment of intestinal viability?

Wall thickness

___________ may increase the possibility of dehiscence after enterotomy closure.

Excessive mucosal eversion

Cats with linear FB ingestion may be managed conservatively if they _______.

Present soon after ingestion + have no signs of peritonitis

What suture approach is recommended for enterotomy closure?

Simple continuous or interrupted approximating suture pattern

-could also utilize skin staples (but NOT wound glue)

What is a condition that can mimic constipation due to the appearance of tenesmus in companion animals?

Urethral obstruction

What are some of the main causes of constipation in companion animals?

-Dehydration secondary to other disease → CKD

-Narrowing of colonic lumen​

-Intraluminal → stricture, mass, FB

-Extraluminal → pelvic narrowing, LNs, masses​

-Idiopathic megacolon​

-Neurogenic → spinal cord or lower motor neuron disease​

What are the main diagnostics that should be considered in a case of constipation in companion animals?

1. CBC/Chem/UA/T4 → looking for diseases that cause dehydration​

2. Extraluminal + neurogenic evaluation → full neuro + rectal exam, spinal + pelvic radiographs, abdominal US

3. Intraluminal evaluation → abdominal US, positive/negative contrast radiographs, ± colonoscopy

What condition must be ruled out as a cause of constipation in kittens/young cats?

Congenital hypothyroidism

What are the factors that have been shown to be associated with an increased risk of constipation in cats?

Older​, Overweight​, CKD, Previous episodes of constipation, Higher iCa levels

What is the severe, complete inability to pass any stool due to a solid, immovable fecal blockage + absent motility patterns of the large intestine eventually leading to megacolon?

Obstipation

What is the infrequent, difficult passage of hard, dry stool while some level of colonic motility remains?

Constipation

It is preferred for biopsies of the small intestine to be taken during what procedure, as it allows for a full thickness, more sizable sample?

Laparotomy

What are the instruments you should use when obtaining an intestinal biopsy sample?

#11 scalpel blade + Metzenbaum scissors

What happens to the intestine oral (in front of) to a complete intra-luminal obstruction?

Distends with gas → swallowed air, CO2 formed by bicarb neutralization, organic gases from fermentation

Distends with fluid → rentention of ingested fluids, secretion of salivary glands/biliary/gastric/pancreatic glands

A Basenji mix presents with persistent vomiting, loss of gastric secretions, electrolyte imbalances, hypovolemia, & dehydration for 3 days. Upon bloodwork, the dog also shows hypochloremia, hypokalemia, & metabolic alkalosis. On radiography, there are no significant findings. You suspect an obstruction. Where is the obstruction most likely located?

Duodenum or proximal jejunum

A Shetland Sheepdog presents with intermittent anorexia, lethargy, diarrhea, & occasional vomiting for several weeks. He appears to be malnourished as well. Upon bloodwork, the dog shows metabolic acidosis. You suspect an obstruction. Where is the obstruction most likely located?

Distal jejunum, ileum, or ileo-cecal junction

What is typically the cause of death for dogs with untreated distal/low intestinal obstruction?

Fluid loss + toxemia related to bacterial proliferation

How should you close the intestine post-enterotomy?

Simple interrupted appositional sutures → closer to incision on mucosal side (lumen), further from incision on serosal side (outside)

When performing an enterotomy to remove a foreign body, the incision into the intestine should ideally be made at what location?

Aboral (distal) to the foreign body

When performing an intestinal resection + anastomosis, what are the major vessels that must be occluded &/or transected during the procedure?

-Arcadial mesenteric vessels from the cranial mesenteric artery for that segment of intestine

-Terminal arcade vessels + vasa recta vessels within mesenteric fat at points of proposed intestinal transection

If you use an oblique incision when performing intestinal resection + anastomosis, which end should be the shorter end?

Antimesenteric → lacks blood supply that mesenteric side has

When closing the small intestine, or any section of the GI tract, what is the holding layer?

Submucosa

What occurs during the lag phase (days 0-4) of intestinal healing following intestinal resection + anastomosis?

Inflammation + edema

What occurs during the proliferative phase (days 3-14) of intestinal healing following intestinal resection + anastomosis?

Rapid gain in wound strength

What occurs during the maturation phase (days 10-180) of intestinal healing following intestinal resection + anastomosis?

Collagen is reorganized

Following an intestinal resection + anastomosis procedure, when is the most likely time for intestinal dehiscence?

Days 3-5 → most inflammation + edema at this time, little actual healing

What are the most common locations for intussusception in small animals?

Ileocolic + Jejunojejunal

What causes intussusception in small animals?

Hypermobility associated with enteritis (parasites, infection, diet, FB, masses)

Roughly what percentage of splenic tumors in dogs that present with hemoabdomen are malignant (hemangiosarcoma)?

70%

Roughly what percentage of splenic tumors in dogs that are found incidentally are benign?

70%

What should you tell a client that asks you to determine their dog’s splenic tumor type prior to surgery so that they may better decide which treatment to choose?

I cannot tell you the tumor type w/o surgically removing the spleen + sending it out for histopathologic evaluation

What is the one year survival rate for dogs with hemangiosarcoma that have surgery alone?

6-7%

What is the benign incidental finding on the spleen that is comprised of harmless deposits of iron, calcium, & bile pigments?

Siderodic plaques (Gamna-Gandy bodies)

What concurrent emergency disorder does splenic torsion most often occur with?

GDV

A Great Dane presents suddenly collapsed with pale MM, tachycardia, & abdominal distension. What is the most likely differential that will need to be immediately corrected?

Acute splenic torsion

What is the gold standard for diagnosing splenic torsion in small animals?

Abdominal ultrasound → classic “twisted pedicle”, enlarged + poorly positioned spleen, altered tissue textures, absent blood flow

What is the treatment of choice for dogs with splenic torsion?

Splenectomy → good prognosis

What are the 3 most common splenic tumors found in small animals?

1. Hemangiosarcoma

2. Hematoma

3. Hemangioma

Most dogs with hemangiosarcoma (HSA) have gross evidence of metastatic disease upon initial presentation. Where do HSAs most frequently metastasize to?

Liver, omentum, mesentery, brain

What would you be looking for if performing an echocardiogram on a dog that has a splenic tumor?

Signs of metastasis in the right atrium → pericardial effusion, cardiac masses, myocardial function, chamber changes

What vessels should you attempt to preserve when performing a splenectomy in small animals?

Short gastric branches + Pancreatic branch of splenic artery

Why do we rarely perform a partial splenectomy in small animals?

Disease is typically diffuse + risk of hemorrhage is high

What will help you determine if splenic disease is a surgical emergency?

-Hemoabdomen present

-Patient stability/status (MM, CVR, mentation)

If a patient with splenic disease does not have a hemoabdomen, when should it be seen?

Later this week or next week → not an emergency

If a patient with splenic disease previously had a hemoabdomen but is now stable, when should it be seen?

Surgery within the day or next day

If a patient with splenic disease currently has a hemoabdomen & is not responding to stabilization efforts, when should it be seen?

Emergency surgery right now → try to stabilize as much as possible first

Why might an animal having splenectomy surgery develop pancreatitis?

Damage to blood supply to the stomach or pancreas

What disease state where surgery would be contraindicated can mimic splenic disease in small animals?

Coagulopathies (rodenticide poisoning, vWD, DIC)

What are the classic surgical intestinal disorders in large animals?

Intussusception, SI volvulus, Mesenteric torsion, Intestinal strangulation, FB obstruction

A 4yo Holstein cow in early lactation is presented with the following sudden onset of clinical signs: acute anorexia, sudden milk drop, distended painful abdomen, little manure production, pale MM.

What intestinal disease is most likely?

What diagnostics would confirm this diagnosis?

Why is the prognosis often poor?

-Dx: Hemorrhagic Bowel Syndrome (HBS, jejunal hemorrhage syndrome)

-Diagnostics: Clinical signs + Rectal exam + Exploratory surgery (r/o other causes via US or abdominocentesis)

-Poor prognosis: Usually start bleeding somewhere else, most cows die or are euthanized

What are the risk factors associated with Hemorrhagic Bowel Syndrome (HBS, jejunal hemorrhage syndrome)?

-High production cows (<100 days in milk, >2nd lactation)

-Fall + winter months

-Aggressive eaters

-Recent feed change

-Cows sorting TMR

-Rumen acidosis

-Excessive rumen fill with high soluble protein + CHOs

-Feeding corn silage ensiled <1 week

How can we attempt to treat Hemorrhagic Bowel Syndrome (HBS, jejunal hemorrhage syndrome) in dairy cattle?

Supportive care → IV fluids, NSAIDs/morphine, Calcium products, Abx, C. perfringens Type C/D antitoxin, Laxative (MgOH), Transfaunation

In a dairy cow with Hemorrhagic Bowel Syndrome (HBS, jejunal hemorrhage syndrome), they often have a sudden onset of clinical signs. Why does this sudden onset usually occur?

Blood clots from hemorrhage into the intestine lead to intestinal obstruction

What are the risk factors for cecal dilatation + torsion, mainly seen in dairy cattle?

-Atony + gas production

-Hypocalcemia

-Concurrent disease

-Acid/base disturbances affect cecal motility

How can we attempt to medically manage a cecal dilatation before it becomes a volvulus/torsion?

Give calcium, fluids, laxatives, + transfaunate

Which infectious cause of diarrhea in production animals is established early in life at the ileo-cecal region from colostrum, milk, or feces contamination, leading to granulomatous enterocolitis & a chronic infection that sheds in the feces but leaves the animal looking clinically normal for several years until the enteritis is severe enough to lead to wasting disease + diarrhea?

Johne’s Disease (Mycobacterium avium sp. paratuberculosis)

A 3yo cow presents with diarrhea, protein losing enteropathy (PLE), weight loss, & peripheral edema, but no fever + still has a good appetite. What is your top differential diagnosis?

Johne’s Disease (MAP)

What is the most common clinical sign noted in small ruminants with Johne’s Disease (MAP)?

Wasting disease (ill thrift, low BCS)

-few show diarrhea

How can we diagnose Johne’s Disease (MAP) in ruminants?

Fecal culture or PCR

-could also utilize serological testing (AGID or ELISA)

How can grain overload lead to diarrhea in ruminants?

Excess VFA production in rumen → VFAs draw water into gut → diarrhea 12-24hrs later

-can be good as it is flushing toxins out

Soils with what elevated elements can lead to secondary copper deficiency (absorption interference)?

Molybdenum, sulfates, zinc

A cow presents with diarrhea, poor weight gain, lightening hair coat color, musculoskeletal issues (fractures), & anemia. What is your top differential diagnosis?

Copper deficiency

How can we obtain a diagnosis for copper deficiency in ruminants as serum copper does not decrease unless they are severely deficient?

Liver copper concentrations

What are the general diarrhea treatment guidelines for ruminants?

-Fluids

-Antibiotics

-NSAIDs

-Anthelmintics

-Antitoxin

-GI protectants

What is the maintenance fluid therapy amount per day for ruminants?

50mL/kg/day

-use 12-14G catheter for adult cattle, 14-16G adult SR/camelids/calves, 16-18G for SR/camelid neonates

What kind of fluids would you choose to use in a cow with proximal GI disease that causes metabolic alkalosis, hypochloremia, & hypokalemia?

0.9% NaCl

What is the maximum IV flow rate for KCl supplementation in ruminants receiving fluids therapy?

0.5mEqK/kg/hr

When would you utilize dextrose supplementation in ruminants?

Hypoglycemic calves + Ketotic cows

How can we minimize infection during the dehorning/disbudding process in cattle?

Don’t enter frontal sinus (disbud>dehorn), maintain cleanliness

Where should local anesthesia be administered for a dehorning procedure in cattle?

½ way between lateral canthus of eye + base of horn (over frontal crest)

Why is disbudding neonates the preferred method of horn removal over dehorning adults in ruminants?

No hemorrhage + no frontal sinus involvement

When is the oldest you can perform disbudding before having to resort to dehorning in ruminants?

2 months old

After performing a dehorning procedure in a cow, you may encounter hemorrhaging. What should you avoid using to stop the hemorrhage as it could get into the sinus & cause issues?

Hemostatic powders → instead pull/ligate artery or use cautery to stop bleeding

When should you perform a disbudding on goats in order to minimize bleeding, stress, & pain?

<2 weeks old

What anesthesia should you administer in goats prior to disbudding?

Dilute lidocaine @ cornual branches of the lacrimal + infratrochlear nerve

How should goats be handled post-disbudding procedure?

-Isolation until completely healed

-NSAIDs

-Tetanus

-Bandage to prevent contamination

-± antibiotics

What is the most common congenital defect in cattle, especially in Holstein-Friesians?

Umbilical hernia

What do the umbilical arteries turn into after birth in animals?

Round ligaments of the bladder

What are some of the other differential diagnoses for an umbilical hernia in large animals?

Umbilical abscess, Local omphalitis, Ventral hernia

In equine patients with a simple umbilical hernia that is <5cm, how should it be repaired?

Spontaneous closure → digital irritation of the ring

In equine patients with a simple umbilical hernia that is >10cm, how should it be repaired?

Surgical repair → risk of strangulation

In bovine patients with a simple umbilical hernia that is <5cm, how should it be repaired?

Hernia clamp, elastrator bands, abdominal support bandage, irritation of ring (digital palpation, injection of irritants)

In bovine patients with a simple umbilical hernia that is >5cm or has GI pathology, how should it be repaired?

Surgical repair

How is an open herniorrhaphy performed to repair a simple hernia in large animals?

Excision of hernial sac (peritoneum) → evaluation of contents (remove infection) → closure of freshly debrided abdominal wall (simple interrupted, inverted cruciate, or simple continuous)

How is a closed herniorrhaphy performed to repair a simple hernia in large animals?

Hernial sac inverted into abdomen → all SQ tissue removed → simple interrupted or inverted cruciate pattern used to close

When do we use mesh herniorrhaphy to repair hernias in large animals?

Large hernias (excessive tension)

-close via simple interrupted pattern

What are the main complications seen post-hernia repair surgery, especially in calves?

Edema, suture abscess, seroma, hematoma, dehiscence, adhesions, peritonitis

A 4mo old calf presents with acute unthriftiness as well as a warm, painful, non-reducible mass around the umbilical area, but no hernial ring palpated. What is your top differential diagnosis?

Omphalitis (cellulitis of umbilical cord stump)

How should you treat an umbilical abscess in a calf?

-If no hernia → drain + lavage ± systemic abx

-If also hernia → open herniorrhaphy + remove infected material + resect any adhesions

A horse presents with a large, broad-based painful mass near the umbilicus, unthriftiness, as well as a purulent discharge coming from the umbilicus. What is your top differential diagnosis & what do you expect to find on CBC?

Ddx: Umbilical cord remnant infection (A. pyogenes, E. coli, Proteus, Strep, Staph)

CBC: Hyperfibrinogenemia, Hyperproteinemia, Neutro-lympho reversal, Mild anemia

Why might producers want to dock the tails of their lambs?

Prevention of myiasis + Breeding efficiency (ram)

What may happen if you dock a lamb’s tail too short (past the distal level of the caudal tail fold)?

Rectal prolapse

Which production animal most commonly gets rectal prolapse?

Pigs

What are the methods of surgically repairing a rectal prolapse in pigs?

1. Prolapse ring → insert with ½ way point at anus, tight ligature close to anus, should necrose + fall out in 5-7 days

2. Blade amputation → insert rubber tube into rectum, cross pin fixation, circumferential removal of damaged mucosa → suture