Constipation

Question 1

define constipation, obstipation, tenesmus, dyschezia

Answer 1

constipation: infrequent or difficult fecal elimination

obstipation: intractable constipation
-inability to evacuate feces, can result in impaction

tenesmus: ineffectual or painful straining at defecation

dyschezia: difficult or painful defecation that arises exclusively from disease of the anal and perianal tissues

Question 2

describe the primary functions of the large intestine

Answer 2

proximal half: absorb water and electrolytes
distal half: storage of fecal material

Question 3

how do contents move through the large intestine?

Answer 3

1. haustral contractions serve to mix the contents in the LI
   -allows for maximal absorption of water and electrolytes
   -slowly propel contents from cecum through ascending colon
   -occur continuously throughout the day
2. mass movements move material from transverse colon to rectum
   -only a few occur per day, esp after eating
   -conducted through extrinsic nerves of ANS

Question 4

describe defecation

Answer 4

1. stimulated by movement of feces into the rectum
2. continence maintained by internal and external anal sphincters
   -ANS: internal
   -voluntary control via pudendal nerve: external

3, peristaltic waves initiate defecation but will stop if voluntary relaxation of the external anal sphincter does not occur

Question 5

describe extraintestinal causes of constipation

Answer 5

1. may inhibit normal neural impulses or muscular function
2. can interfere with the parasympathetic defecation reflex due to weakness, pain, or dyspnea
3. may affect fecal consistency due to dehydration or cause mechanical obstruction due to compression
4. examples:
   -hypothyroidism
   -hypercalcemia
   -hypokalemia
   -chronic renal failure
   -myopathies
   -thoracic cavity disease
   -neurologic disease
   -pelvic fractures

Question 6

describe intestinal and anorectal diseases causing constipation

Answer 6

1. obstruction
2. inhibition of the defecation reflex because of pain
3. loss of motility
4. examples:
   -atresia ani
   -perineal hernia
   -prostatic disease
   -perianal fistula

Question 7

describe specific history questions for constipation

Answer 7

1. is the patient straining to defecate?
   -NEED to see this to know it is constipation
2. when was the last time the patient defecated?
3. how did the feces appear (color, ribbon-like, soft vs hard, etc.)
4. any known history of trauma (recent or chronic) or recent surgery?
5. any known concurrent diseases?
6. any ingestion of indigestible material? (bone, hair, plastic, sticks, etc.)

Question 8

what are the signs of constipation?

Answer 8

1. pain during defecation
2. arching back
3. vocalization during defecation
4. stiff gait
5. reluctance to move
6. decreased fecal output
7. frequent attempts to have a bowel movement

Question 9

describe how signalment can help narrow differentials down for constipation

Answer 9

1. cats:
   -most commonly idiopathic megacolon!!!!!
   -or sacral spinal deformities in manx cats
2. intact male dogs:
   -prostatic disease
   -perineal hernia
3. large breed dogs:
   -orthopedic diseases such as hip dysplasia
4. young dogs and cats:
   -atresia ani
5. german shepherd: higher risk for perianal fistulas
6. dysautonomia:
   -dogs from Kansas and Missouri, cats from the UK

Question 10

describe physical exam for constipation

Answer 10

1. visual inspection of perineal/anal area:
   -perianal fistula
   -tumors
   -atresia ani
2. digital rectal exam: should ALWAYS perform
   -perineal hernia
   -masses
   -prostatic disease
   -stricture
   -pain

Question 11

describe diagnostics for constipation

Answer 11

1. baseline bloodwork and urinalysis
   -CBC, biochem, panel
   -eval for extraintestinal causes and underlying disease
2. abdominal radiographs:
   -contrast may be beneficial
3. abdominal ultrasound or CT
4. colonoscopy if no apparent answer on other diagnostics

Question 12

describe the diagnostic tree for constipation

Answer 12

1. present with no fecal production: rectal exam, abd palpation, radiographs
2. if colon is full:
   -constipation or obstipation, so check for rectoanal disease

-if rectoanal disease present: perianal fistula, perineal hernia, neoplasia, prostatic disease, atresia ani

-if no rectoanal disease: megacolon, metabolic disorders (hypothyroid, hypercalcemia, hypokalemia)

3. if colon is empty:
   -inflammatory disease
   -neurogenic disease: dysautonomia
4. if presented with small volume feces or ribbon-like stools:
   -rectal exam, rads, US, colonoscopy
   -luminal narrowing, neoplasia, rectal and anal stricture, prostatomegaly, pelvic fractures

Question 13

describe atresia ani

Answer 13

1. most commonly reported congenital anorectal anomaly in dogs
2. 4 types:
   -type 1: congenital stenosis of the anus without imperforate anus

-type 2: imperforate anus (just a dimple), distance to blind rectal pouch <1.5cm

-type 3: imperforate anus, distance to blind rectal pouch >1.5cm

-type 4: normal terminal rectal and anal development but cranial rectum ends as a blind pouch

3. may also have rectovaginal or rectourethral fistula
   -not completely obstructed, but pooping out vulva or urethral = still very wrong

Question 14

describe clinical signs/physical exam of atresia ani

Answer 14

type 1:
-normal until weaning, then constipation/tenesmus
-may have stenosis at anal opening

type 2-4:
-normal for 1st 2-4 weeks
-anorexia, abdominal enlargement, restless
-absent defecation
-may develop vomiting and dehydration
-type 2 and 3 have imperforate anus and dimple where opening should be

Question 15

describe diagnosis and treatment of atresia ani

Answer 15

diagnosis:
1. PE for exterior anal anomalies (rectal if you can but usually puppies so not super possible)
2. abd radiographs

treatment:
-type 1: balloon dilation or bougienage

-type 2 and 3:
–incision through skin at dimple
–rectum from cranial to the end of blind pouch pulled caudally
–sutured to skin

Question 16

describe megacolon

Answer 16

1. enlargement of colon leading to constipation and eventually obstipation
2. characterized by colonic hypomotility and a permanent increase in colonic diameter
3. most commonly occur in cats
   -can occur in dogs more rarely
4. 2 categories: acquired and idiopathic

Question 17

describe acquired megacolon

Answer 17

1. mechanical causes:
   -extraluminal compression: pelvic fractures, prostatomegaly, pelvic masses

-intraluminal compression: intraluminal stricture, neoplasia, FB

2. functional causes:
   -neuromuscular dysfunction: spinal cord disease, dysautonomia, pelvic nerve injury, sacral spinal abnormalities (manx cats)
   -metabolic disease: hypothyroid, hypokalemia

Question 18

describe megacolon in cats

Answer 18

1. idiopathic in 62%
   -23% pelvic fractures
   -6% neuro dysfunction
   -5% manx
2. middle aged, male cats most affected
3. pathophysiology poorly understood
   -generalized dysfunction in longitudinal and circular smooth muscle
   -disturbance in activation of smooth muscle myofilaments

Question 19

describe clinical signs of megacolon in cats

Answer 19

1. constipation or obstipation
2. fecal tenesmus
3. +/- abd enlargement
4. +/- vomiting:
   -may be due to vagal stimulation of CRTZ from intestinal dilation
5. +/- paradoxical diarrhea: liquid feces may pass around fecoliths

Question 20

describe PE for megacolon in cats

Answer 20

1. can palpate enlarged colon via abdominal palpation
2. digital rectal exam:
   -rule out physical causes of obstruction (atresia ani, pelvic stenosis, prostatomegaly, masses)
3. full neuro exam to eval for any muscular weakness or spinal cord dysfunction

Question 21

describe diagnostics of megacolon in cats

Answer 21

1. abd rads:
   -colonic diameter >1.5x length of L7 vertebral body on lateral projection
   -eval for evidence of pelvic fractures/pelvic stenosis
2. bloodwork:
   -rule out systemic causes of neuromuscular dysfunction
   -thyroid panel, electrolytes

Question 22

describe medical treatment of megacolon in cats

Answer 22

1. medical management for idiopathic
   -removal of fecal material:
   –warm water or lactulose enemas: mild cases
   –deobstipation (more severe): manual removal of feces under general anesthesia
   -NO fleet enemas!!
2. IV/SQ fluids to correct dehydration
3. diet change: royal canine fibre response diet
4. laxative: lactulose, miralax, docusate, dolculax
5. prokinetic: cisapride

Question 23

describe surgical treatment of megacolon in cats

Answer 23

1. performed if medical management fails in idiopathic or if caused by old pelvic fractures with >6 months of constipation
2. subtotal colectomy:
   -removal of intra-abdominal portion of the colon
   -may also have to remove the ileocecocolic junction to decrease tension on the anastomosis site
3. if pelvic fractures and less than 6 months of constipation
   -can consider procedures to open pelvic canal such as pelvic osteotomy

Question 24

describe perineal hernias

Answer 24

1. most common in intact older male dogs
   -SHOULD tell owners who choose not to castrate
2. caused by weakness and separation of pelvic diaphragm
3. likely multifactorial cause:
   -hormonal imbalance
   -prostatic enlargement
   -short or docked tail

Question 25

describe clinical signs of perineal hernia

Answer 25

1. uni or bilateral perineal swelling 2. constipation 3. tenesmus 4. straining to urinate or urinary obstruction: can be an emergency 5. organs that can become entrapped: urinary bladder, prostate, small intestine

Question 26

describe diagnosis of perineal hernias

Answer 26

1. digital rectal exam: can palpate rectal sacculation due to weakness and disruption of muscular wall -go in and point finger back at you = very wrong 2. abdominal radiographs (including hernia) recommended: -eval for prostatomegaly -determine what organs may be entrapped in hernia

Question 27

describe treatment of perineal hernia

Answer 27

1. medical management: -laxatives: lactulose -removal of fecal material from hernia if needed -urinary catheter if urinary obstruction 2. surgical treatment: -primary repair of hernia: herniorraphy -may recommend cystopexy, colopexy, vasopexy -castration recommended

Question 28

describe rectal prolapse

Answer 28

1. often secondary to GI parasites 2. most common in young cats and dogs 3. diagnosis: -PE -must differentiate from prolapsed intussusception! --blunt instrument or finger between prolapse and anus: if can insert easily between them = intussusception --should NOT be able to insert anything with rectal prolapse

Question 29

describe treatment of rectal prolapse

Answer 29

1. reduce prolapse if tissue viable -apply lube; may need to apply 50% dextrose or furosemide to reduce swelling first 2. place pursestring suture that will allow fecal material to pass but not allow the prolapse to recur -leave for 3-5 days 3. treat underlying cause in the meantime 4. if prolapse occurs after pursestring, colopexy may be necessary 5. if tissue is not viable or has been traumatized: R&A may be necessary