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Large Animal Surgery > Food Animal Urolithiasis > Flashcards

Food Animal Urolithiasis Flashcards

1
Q

What large animals have a higher incidence of urolithiasis? In wgat species is it rare?

A

goats and sheep +/- horses, pigs, cattle

South American camelids and Old-World camels

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2
Q

What is the pathogenesis of urolithiasis in food animals like?

A
  • nutritional disease (mineral imbalances, altered water intake) causes the production of alkaline urine
  • this results in the formation of supersaturated urine, which acts as a matrix for crystal precipitation
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3
Q

What are 5 objects in supersaturated urine that act as a matrix for crystal precipitation?

A
  1. debris
  2. casts
  3. cells
  4. bacteria
  5. mucoproteins
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4
Q

What are 3 causes of mucoprotein increase in the urine of food animals?

A
  1. estrogen
  2. low vitamin A
  3. high concentrate feed
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5
Q

What are the 5 most common types of uroliths in food animals?

A
  1. magnesium ammonium phosphate (struvite)
  2. calcium hydrogen phosphate
  3. calcium carbonate
  4. calcium oxalate
  5. silicate
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6
Q

What are the 2 classes of phosphatic calculi in food animal urine?

A
  1. struvite (magnesium ammonium phosphate)
  2. apatite (calcium phosphate)
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7
Q

What are 2 dietary risk factors that causes the development of phosphatic calculi? How?

A
  1. high concentrate - increased P and Mg, low Ca increases pH and P absorption and excretion
  2. low roughage - decreased salivation and GIT P loss results in increased urinary excretion
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8
Q

What are the 2 major dietary risks for the development of calcium carbonate uroliths? What may also play a role?

A
  1. high calcium diets
  2. clover and alfalfa - high in Ca and oxalate, low in P and Mg

water hardness

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9
Q

Although it is unclear what factors influence the formation of calcium oxalate uroliths, what has been hypothesized to contribute?

A
  • low solubility of urine
  • oxalate containing plants
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10
Q

Oxalate is normal to find in the urine. Why?

A

result of glycine and ascorbic acid metabolism

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11
Q

What is the typical presentation of silicate calculi? What causes its formation? Where is this especially common?

A

singular stones

ration with high Ca:P ratios (2.8:1) —> grasses of western North America and Canada

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12
Q

What is not correlated to the development of silicate calculi?

A

urine pH

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13
Q

What gender has higher incidence of urolithiasis? Why? What are the 4 most common sites of obstruction?

A

males —> smaller, longer urethra

  1. urethral process
  2. sigmoid flexure
  3. ischial arch
  4. bladder neck
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14
Q

What history is especially important to collect when diagnosing urolthiasis?

A
  • diet - low roughage, high concentrate (common in feedlot cattle!)
  • premature castration - hypoplastic urethra = smaller lumen
  • purpose
  • urination history
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15
Q

What are some common behaviors indicative of pain or discomfort caused by urolithiasis?

A
  • depression
  • vocalization
  • bruxism - grinding teeth
  • tail flagging - erect, quivering
  • stranguria, pollakiuria, dysuria
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16
Q

What are important aspects of the physical exam in cases of urolithiasis?

A
  • TPR - tachycardia, pyrexia with urethral rupture
  • abdominal distention and contour - uroabdomen, ruminal stasis
  • abdomen palpation - fluid ballottement, distended bladder, “water belly” of SQ urine
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17
Q

What is the abdomen of this goat like?

A

normal!

  • fat pad common in the inguinal area, does not extend up to the abdomen
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18
Q

What is the abdominal contour of the goat and calf like?

A

swollen around prepuce and inguinal area —> uroabdomen

  • more extended than the normal goat fat pad
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19
Q

What is the abdominal contour of the sheep and cow like?

A

SQ swelling and edema —> water belly

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20
Q

What is the abdominal contour of this sheep like?

A

ventral/para-sheath edema

  • not uroabdomen, extends too far cranial
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21
Q

What can be observed in the perineal area indicative of urolthiasis?

A

urethral pulse seen ventral to the anus due to increased pressure —> not in sync with HR

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22
Q

How are the bladder, peritoneum, and kidneys affected by urolithiasis on ultrasound?

A

distended —> can do transabdominal in small ruminants, must be transrectal in cattle

hypo/anechoic fluid in abdomen

hydronephrosis = dilated renal pelvis (chronic)

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23
Q

What views are preferred for radiographing the urinary system for diagnosing urolithiasis? Which uroliths can be seen?

A

two LM views with legs cranial and caudal —> need to catch all of the urethra in males, can observe location and number

calcium oxalate and calcium carbonate

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24
Q

What are 4 things seen on serum biochemistry indicative of urolithiasis?

A
  1. azotemia - BUN (> 30 mg/dL), CREA (> 3 mg/dL)
  2. electrolytes - high K, low Na and Cl
  3. hemoconcentration
  4. hyperlactatemia
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25
Q

What development caused by urolithiasis commonly leads to salvage procedures?

A

uremia

26
Q

When is medical treatment recommended for urolithiasis? What are 4 components of this procedure? What commonly happens after treatment?

A

if obstruction is not complete

  1. catheterization and retrograde flushing (unrewarding)
  2. Acepromazine - decrease urethral spasms
  3. NSAIDs - careful with renal toxicity
  4. urinary acidifiers - dissolves stones

re-obstruction —> not all uroliths will likely be dissolved

27
Q

What is the purpose of performing a urethral process amputation in cases of urolithiasis? In what animals is this most commonly done? What is required?

A

removal of the narrow vermiform appendage

small ruminants

  • SEDATION - Valium, Midazolam, Xylazine, Acepromazine
  • LOCAL ANESTHESIA - lumbosacral epidural with Lidocaine (toxicity seen > 8 mg/kg)
28
Q

How is a urethral process amputate performed? What is observed for following surgery?

A

exteriorize the penis and aputate the vermiform appendage to allow urine flow

urine passage —> resoration is commonly temporary

29
Q

What are the 3 major anatomic challenges of passing a retrograde catheter through the urethra to treat uroliths? What can happen with aggressive placement?

A
  1. urethral fossa
  2. sigmoid flexure difficult to traverse
  3. urethral diverticulum blind end)

tears or ruptures result in stricture formation and contributes to further/worse obstruction

30
Q

What are 5 preoperative considerations important when surgically correcting urolithiasis?

A
  1. correct electrolyte/biochemistry abnormalities due to anesthetic risk - azotemia, dehydration, hyperkalemia
  2. antibiotics (cephalosporins, penicillin) - likely not a clean surgery
  3. NSAIDs (Flunixin)
  4. fluid therapy - 0.9% NaCl, 0.45% NaCl + 5% dextrose, calcium, insulin
  5. drainage of uroperitoneum - blocks reabsorption of K
31
Q

What is the purpose of half-strength saline, calcium, and insulin fluids prior to surgically correcting urolithiasis?

A

half-strength saline contains dextrose, which provides energy to the ATPase to move K into the cell and out of the serum

cardioprotective in the face of hyperkalemia

shuttles K into cells

32
Q

What is the purpose of performing a tube cystotomy in treating urolithiasis? In what animals is this recommended? What is required?

A

allows for urinary diversion out of the tube by gravity, which should resolve inflammation

breeding animals, buys time to dissolve uroliths

proper, sterile facilities and general anesthesia

33
Q

What approach is preferred for tube cystotomies?

A

patient in dorsal recumbency with parapreputial incision (midline celiotomy)

  • allows for peritoneal suction if needed
34
Q

Once the bladder is exteriorized, what happens in the process of a tube cystotomy?

A
  • cystotomy near the apex to remove uroliths and flush the bladder, then closed
  • repair any ruptures (common in dorsal wall)
  • place a Foley catheter through skin, abdomen, then ventral bladder wall via an incision lateral to the primary skin incision
35
Q

Tube cystotomy:

A

gravity = passive leakage

36
Q

How are patients treated following a tube cystotomy? When can the catheter be removed?

A
  • continued antibiotics and NSAIDs
  • leave catheter open for 3-5 days
  • after 5 days, clamp the catheter and monitor for urine from prepuce (dry, unbedded stall)

24 hours of normal urination with a tubed clamp

37
Q

What are 3 advantages to tube cystotomies? 2 disadvantages?

A
  1. allows for direct bladder evaluation
  2. breeding ability maintained
  3. allows for contrast radiography

higher cost, complications associated with a 70% success rate

38
Q

What are some positive prognostic factors for tube cystotomies?

A
  • goats > sheep
  • no uroabdomen > uroabdomen
  • urination within 7 days > urination longer than 7 days
39
Q

In what animals is bladder marsupialization recommended? What equipment is required?

A

breeding bucks and rams

proper, sterile facilities and general anesthesia

40
Q

How is bladder marsupialization performed?

A
  • paramedian celiotomy
  • cystotomy and flush bladder
  • incorporate the bladder into the caudal aspect of the skin incision
  • perform a second skin incision the size of the cystotomy and position the bladder as cranial as possible
41
Q

What are 3 advantages to performing bladder marsupialization? A disadvantage?

A
  1. allows direct evaluation of bladder
  2. relatively simple procedure
  3. reduced hospitalization and recurrence (don’t need to wait for restoration of urine flow)

cystitis and urine scald dermatitis common due to permanent opening communicating with the environment

42
Q

When is perineal urethrostomy recommended? When is it not performed? What is prognosis like?

A

urethral ruptures

breeding animals

  • short term = 64%
  • long term = 11% (strictures form very commonly post-op)
43
Q

What are the 2 options of positions of perineal urethrostomies? Which one is preferred?

A
  1. high PU at the level of the tuber ischii
  2. low PU at the distal bend of the sigmoid flexure

LOW —> less tension on penis to allow for easier exteriorization, option for a PU revision at the higher position if a structure occurs (gives another option before salvage!)

44
Q

What is the main procedure recommended for cattles with urolithiasis/obstructions? Some longer term option?

A

SALVAGE penectomy, or perineal/ischial urethrostomy with uremia resolution to reach carcass weight for slaughter

preserve breeding bull with ischial urethrostomy or tube cystotomy

45
Q

What is the purpose of performing a penectomy for urolithaisis/obstructions?

A

amputate penis and open it up to the outside as a short-term salvage procedure to reach carcass weight for slaughter

  • especially important for urethral rupture
46
Q

What is the purpose of performing a perineal or ischial urethrostomy in cattle with urolithiasis/obstructions? How is it performed?

A

provides time to resolve azotemia and reach slaughter weight

standing with caudal epidural

47
Q

In what cattle is an ischial urethrotomy preferred? How is it performed?

A

breeding bulls

  • similar approach as an ischial perineal urethrostomy
  • remove urolith through opening and place a Foley catheter
  • primary closure following tube removal
48
Q

In what cattle are tube cystotomies performed? What is required?

A

breeding bulls

  • proper, sterile environment
  • general anesthesia
  • standing laparotomy
49
Q

What is preferred for surgically treating urethral ruptures?

A

stab incisions to relieve urine and cause leakage into SQ space + antibiotics

50
Q

What are the 4 ways of preventing urolithiasis?

A
  1. increase urine volume and dilution
  2. decrease matric components (calculogenic minerals, mucoproteins)
  3. manage minerals
  4. improve design of urinary tract
51
Q

What are 3 options for increasing urine volume?

A
  1. increase water intake
  2. regular anions
  3. feed more forage and increase meal feedings to 30 min BID to increase ADH
52
Q

How are diets altered to regulate anions? What 2 things does this result in?

A

addition of dietary salt —> 5 lbs per 100 lbs of feed

  1. increases water intake increased urine production and more dilute ions
  2. MgCl is found in the urine instead of MgPO4, which will bind to mucoproteins to inhibit silicate and PO4 binding
53
Q

How can water consumption be increased?

A
  • ensure its palatability
  • manage temperature - warm in winter, cool in summer
  • multiple sources available
  • short distances for access
54
Q

What are 2 options for decreasing matrix content of urine?

A
  1. forage over concentrate
  2. mineral supplementation and balance - no calcuhenic feeds!
55
Q

How are minerals managed to avoid urolithiasis development?

A
  • proper Ca:P ratio of 2:1
  • magnesium should make up <0.6% of diet

(avoids struvite and calcium stone formation)

56
Q

What are the 5 most important dietary management strategies to prevent urolithiasis?

A
  1. vitamin A to decrease cell sloughing
  2. iron to inhibit crystalization
  3. make sure minerals are available to all animals of the herd
  4. Ca:P = 2:1
  5. magnesium <0.6% of diet
57
Q

What is the normal urine pH of food animals on pasture/hay? What is the target pH to dissolve struvite and apatite?

A

7.0-8.0

< 6.5

  • STRUVITE = 6.6-7.8
  • APATITE = 7.2-9
58
Q

What are 2 options for urine acidifying agents?

A
  1. ammonium chloride - weak anion with Cl acidifying action (toxicity possible!) —> 200-300 mg/kg/day PO SID, 3 days on 4 days off
  2. DL methionine - increased palatability —> 200 mg/kg SID
59
Q

What are the 2 best ways to alter urinary tract design to avoid urolithiasis?

A
  1. remove urethral process
  2. delay castration = avoids hypoplastic urethra
60
Q

What overall plan is recommended for preventing/treating urolithiasis?

A
  • identify stone
  • decrease grain, offer free choice minerals, add salt
  • clean, palatable water
  • maintain Ca:P of 2:1 with normal pH and Mg < 0.6%
  • DCAD + anion salt

Large Animal Surgery (32 decks)

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