Surgical Diseases of the Colon, Rectum, Perineum, and Anus (RPA) Flashcards
(86 cards)
1
Q
4 Differential diagnoses for chronic constipation
A
A. Nerve damage
B. Metabolic disease such as severe dehydration, hypercalcemia, hypokalemia, hypothryoidism
C. Colonic obstruction which could be due to an intraluminal mass, stricture, or extraluminal compression
D. Idiopathic megacolon
2
Q
What diagnostics can you do to sort out the differential diagnoses for chronic constipation?
A
- Neuro exam
- CBC/Chem
- Ultrasound
3
Q
Treatment of megacolon
A
A. Resolve cause if possible - whether or not colonic function returns depends on the duration of chronic colonic distension and atony
B. Medical Management
C. Colectomy if non-responsive to either of the above
4
Q
What is the pathophysiology of megacolon (see diagram on page 128 of notes)
A
- Prolonged fecal retention and dehydrated fecal concretions lead to constipation
- Constipation may resolve on its own or with treatment
- If constipation doesn’t resolve, there can be permanent loss of function leading to obstipation
5
Q
Obstipation signs
A
- Recurring episodes with increasing frequency
- Blood, mucus, diarrhea
- Absorb toxins; vagal stimulation
- Depression, anorexia, weakness, vomiting
6
Q
Medical management of megacolon (4 main aspects)
A
- Diet to increase moisture and fiber
- Laxatives and stool softeners
- Enemas, manual evacuation
- Prokinetics (after reliving obstruction)
7
Q
Colectomy - who should perform?
A
- Experienced surgeon
8
Q
How do cats do with removal of entire colon?
A
- They do well
- Small bowel undergoes changes and takes on some of hte functions of the colon
9
Q
How do dogs do with removal of the colon?
A
- Not well with removal of more than 70% of the colon
- Small intestine does not adapt
- Fortunately megacolon is very uncommon in the colon
10
Q
What size can the colon be on radiographs to be consistent with megacolon?
A
Colon diameter 1.5x the length of L7 is consistent
11
Q
How long after colectomy might you expect a cat to have diarrhea?
A
- Several weeks to several months
- Advise client of this before surgery
12
Q
What might be combined with postop diarrhea that you should advise the client of before colectomy?
A
- Cat may have developed an aversion to the litterbox (with chronic constipation, litterbox becomes associated with pain) and need to be retrained to use the litterbox
- Thus, you could have a postop cat with diarrhea and a litterbox aversion for a period of time
13
Q
Stool consistency after colectomy
A
- Immediately after will likely be diarrhea
- May never get back to normal but will become at least semi-formed usually
- Frequency of defecation may always be increased post-op
14
Q
Prognosis for idiopathic megacolon that is non-responsive to medical management and not treated?
A
- Poor prognosis
- Dehydration
- Depression
- Anorexia
- Vomiting
15
Q
Prognosis for idiopathic megacolon treated with subtotal colectomy
A
- > 90% survival at 4 years
- Good to excellent quality of life
- Clients report happier, more active cats
16
Q
What are 8 things you can evaluate on rectal examination (may depend on the sex of the patient)?
A
- Anal sphincter
- Anal sacs
- Rectum
- Pelvic canal
- Pelvic diaphragm
- Urethra
- Prostate/vagina
- Sumblumbar lymph nodes
17
Q
What are the 7 P’s of Preoperative Preparation for Perianal/Perineal surgery?
A
- Prophylactic or therapeutic antibiotics
- Purge feces (digital vs enema)
- Enema x 24 hours
- Pack rectum with gauze (COUNT!)
- Pursestring suture in anus
- Place urinary catheter
- Patient positioning - padding
18
Q
Review: what types of bacteria should you target when choosing antibiotics for a patient with disease of the perineum, rectum, or anus?
A
- Review it because I forgot
19
Q
Review: How would you describe the blood supply to the descending colon? To the rectum?
A
- Segmental
20
Q
Describe the factors that influence healing in the colon/rectum
A
- See the chart discussing healing of different parts of the GIT
21
Q
What happens with a perineal hernia?
A
- Abdominal contents herniate between atrophied pelvic diaphragm muscles
22
Q
-Name the muscles that make up the pelvic diaphragm
A
- Coccygeus and levator ani muscle
23
Q
What are the origin, insertion, and function the coccygeus and levator ani muscles?
A
- Review it if you want
24
Q
What are the functions of the coccygeus and levator ani muscles?
A
- Provide lateral support
- Also create a barrier between abdominal cavity and pelvic canal
25
Where can a perineal hernia occur?
1. between levator ani and rectum (skin is still intact so don't see herniated tissues on PE)
2. between coccygeus and levator ani (skin is still intact so don't see herniated tissues on PE)
26
Predisposing factors for perineal hernia
- What sex are most dogs with perineal hernias?
- 83% of affected dogs are intact males suggesting a hormonal cause
- Weak pelvic diaphragm muscles due to atrophy, neuropathy, hormonal influence, trauma
- Straining and tenesmus
27
How is perineal hernia most commonly diagnosed?
- Via rectal exam by feeling a LACK of sturdy pelvic diaphragm muscles (these muscles normally support the rectum and prevent it from deviating laterally)
28
What sign on rectal exam is strongly suggestive of perineal hernia?
- You can bring your finger back around caudally to point at yourself through the perineal skin
29
In your work-up for PH patient, what causes of straining or tenesmus should you look for?
- Prostatomegaly
- Sublumbar lymphadenopathy
- Perianal mass
- Constipation
- Diarrhea
- Cystitis
30
Why should you repair PH early?
- While it's not an emergency unless you have entrapped intestine or urinary bladder, ideally want to do surgery within a few days to maybe a week or two of diagnosis
- Sometimes hard to convince the client of the urgency because clinically the only sign may be a slight bulge in the perineum
31
What info can you provide the owner to help them understand why it is important to do surgery sooner rather than later for a perineal hernia (3)?
- Progressive increase in size; becomes bilateral and/or ventral
- Continued muscle atrophy --> harder to repair
- Risk of life-threatening complications: bladder retroflexion and intestinal herniation
32
What are the three components of perineal hernia repair?
- Herniorrhaphy
- Castration (83% are intact males)
- Address cause of straining if present
33
Who typically does a perineal hernia repair?
- Surgeons usually
34
What two muscles are the anal sacs located between?
1. Internal anal sphincter
| 2. External anal sphincter
35
What muscle do you cut to allow view of the anal sac?
- External anal sphincter
36
When is anal sacculectomy indicated?
- For recurrent anal sac disease
37
What should you do before anal sacculectomy?
- If an anal sac abscess or infection is present, clear up infection 1st (e.g. with antibiotics, flushing, drainage) before doing an anal sacculectomy
- Infection and associated swelling distorts anatomy, increases risk for leaving sac remnants behind, and compromises healing of the surgery site
38
Which is preferred: closed or open anal sacculectomy?
Why?
- Closed is preferred because it is less disruptive to the anal sphincters
- Commonly done in general practice
39
How much of the external anal sphincter is cut to expose to the anal sac?
- Just a tiny bit to identify the apex of the anal sac
- After the sac is found, dissection is done to free it from between the internal and external anal sphincters without cutting these muscles
40
Describe the 5 steps of a closed anal sacculectomy?
A. Put instrument into the anal sac via the duct
B. Incise skin, SQ, and external anal sphincter muscles to reach anal sac. Use the instrument in the sac to help find it.
C. Dissect anal sac from between the external and internal anal sphincters
D. Ligate and transect the duct.
E. Suture each layer closed
41
What are potential complications of anal sacculectomy?
- If you leave in a part of the anal sac lining (which is secretory epithelium), patient will develop a draining tract that won't resolve until the source is surgically removed
- Fecal incontinence - higher risk if bilateral surgery
42
What % of anal sphincter function is required to maintain fecal continence?
- 50%
43
Ddx for perianal masses (7)
- Perianal adenoma
- Perianal adenocarcinoma
- Anal sac adenocarcinoma
- Anal sac abscess
- Mast cell tumor
- Other neoplasia
- Perianal fistula (this is an ulcer or draining tract
- no mass), but associated swelling may make it seem like an ulcerated mass
44
What should you do on rectal exam with perianal masses?
- On rectal exam, assess how far cranially the mass extends - may be much larger than what you see on the surface
45
What is a good start for workup of a perianal?
- FNA (cheap/easy/fasty start)
- If you see characteristic cells, you can make a diagnosis
- If you don't see characteristic cells, it doesn't mean they aren't there, it just means you did not get them in your sample
- Hard to distinguish between perianal adenoma and perianal adenocarcinoma with cytology
46
What is a next step if FNA is non-diagnostic?
- Biopsy
47
Who tends to get perianal adenomas?
- Intact males
48
What will cause most perianal adenomas to regress? Over what time period?
- Castration over 4-6 weeks
49
Are perianal adenomas hormonally responsive or not?
- They are
| - This is why castration resolves them
50
What should you assess to decide whether or not to remove the adenoma at the time of castration?
- size, location, and number of masses (may be one, or 10+)
- Ulceration (even if it will regress, having a persistent ulcerated perianal mass in an area prime for bacterial contamination for 4-6 weeks or more may not make much sense)
- Degree bothering dog (if it is bothering hte dog, waiting that long may not make sense)
51
What should you do if you do remove a perianal adenoma? What about if you don't remove it?
- Submit for histopath to be sure the original diagnosis was correct
- If mass wasn't removed, take an incisional biopsy and submit for histopath to confirm the diagnosis
52
If you see recurrent perianal "adenomas" in a castrated male, or perianal adenoma in a female dog, what three things should you look for?
1. Residual testicular tissue (e.g. dog is cryptorchid, so client just thought that he had been neutered?)
2. Perianal adenocarcinoma (biopsy for confirmation)
3. Hyperadrenocorticism (steroid ring metabolism leads to increased androgen levels which could stimulate adenoma formation)
53
Are perianal adenocarcinomas hormonally responsive or not?
- NOT
54
Treatment for perianal adenocarcinoma
- Excise with wide margins (+/- sublumbar lymph nodectomy
55
Prognosis for perianal adenocarcinoma
- Good (if tumor <5 cm) to fair (larger tumor) prognosis
56
Recurrence for perianal adenocarcinoma
- Common but may take many months
57
Sex distribution for anal sac adenocarcinoma
- Males = females
58
Paraneoplastic syndrome for anal sac adenocarcinoma
- Seen in 27% of dogs due to tumor expression of PTHrp, which results in hypercalcemia, as seen on serum chemistry
- Always do a rectal examination in a patient with hypercalcemia - you may just find an anal sac adenocarcinoma
59
Where do anal sac adenocarcinomas tend to metastasize?
- Sublumbar lymph nodes first
- Then liver
- Then lungs
60
Options of treatment for anal sac adenocarcinoma?
- Wide surgical excision, lymph nodectomy, radiation, chemotherapy
61
Prognosis for anal sac adenocarcinoma
- Survival decreases from ~20 months to ~20 months if the mass is greater than 10 cm squared, pulmonary metastasis, hypercalcemia, or ulcerated perianal tracts
62
Which breeds tend to get perianal fistulae?
- German shepherds
| - Irish setters
63
Appearance of perianal fistulae
- Ulcerated draining perianal tracts cause licking, hematochezia, odor, pain, anorexia, weight loss
- Often need to sedate the dog and clip hair to see full extent
- Fistulae range from pinpoint to coalesced ulcerations - draw a diagram in the record or take a photo with a ruler to help monitor over time
64
What treatment is first choice for perianal fistulae?
- Medical treatment is first choice as it's an immunologic condition
- Treatment may include cyclosporine, azathioprine, or pred; typically treat for 4 or more months
- Surgery if anal sacs are involved or if not responding to medical management
65
What is most important for management of perianal fistulae?
- Recognize them so you can treat with appropriate meds rather than surgery; typically diagnosed by their appearance on physical examination
66
Complications after rectal, anal, or perianal surgery?
- Dehiscence
- Infection
- Stricture
- Fecal incontinence
- Fistula
- Rectal prolapse
- Urethral damage
67
How do you diagnose a rectal prolapse?
- Insert a probe between the prolapsed tissue and wall of the anus
68
What are results from the probe test if it's an intussusception?
- If you can get the probe really far in, that's intussusception
69
What are the results from the probe test if rectal prolapse?
- Cannot insert the probe very far
70
Who gets rectal prolapse?
- Most common in young animals with a heavy parasite load
- Can be secondary to any cause of tenesmus
- Manx cats are predisposed, presumably due to neurological compromise
71
Treatment options for rectal prolapse with healthy tissue
- Reduce and pursestring x 3-5 days
| - ALWAYS TREAT UNDERLYING CAUSE
72
Treatment option for rectal prolapse with necrotic tissue
- Resection and anastomosis
| - TREAT UNDERLYING CAUSE
73
Treatment for chronic recurrence of rectal prolapse
- Descending colon is pexied to the body wall
- If this happens 3+ times
- You incise into the muscle of the body wall and abrade serosa of descending colon with a 15 blade
- Suture abraded colon to the body wall incision
74
Which body wall is the colon pexied to?
- Left (side the descending colon is normally on) via celiotomy
75
Treatment for anal sac abscess
- Clear up infection 1st!
- Express or lance
- Flush/lavage (saline, chlorhexidine, povidone-iodine)
- warm compress
- Antibiotics (topical and/or oral)
- High fiber diet
- Anal sacculectomy if recurrent disease
76
Prognosis for rectal prolapse repair
- Good with surgical reduction and resolution of initiating cause
77
Rectal neoplasia progression
- Can progress from inflammatory polyp to adenomato adenocarcinoma
78
Invasion and metastatic potential of rectal adenocarcinoma
- Invade locally but slow to metastasize
79
Clinical signs of rectal neoplasia
- Tenesmus, hematochezia, rectal prolapse, weight loss, lethargy, inappetence
80
Primary treatment for rectal neoplasi
- Surgical resection
81
How can rectal neoplasia be accessed often?
- Manually prolapsing the rectal mucosa with stay sutures
- The mass and surrounding mucosa are then cut out and the mucosa sutured closed, or a stapler can be used to remove the mass
82
Antibiotics for rectal neoplasia repair?
- Prophylactic antibiotics are given but not continued unless actual infection or compromised patient
83
Prognosis for a single pedunculated rectal mass?
- Resected and cured often
84
Prognosis for multiple "cobblestone" nodules (i.e. not pedunculated, wider base of attachment)
Harder to remove with good margins, so recurrence is more likely
85
Prognosis for annular tumors (360° around rectum)
- Can have a stricture like effect
| - very challenging to remove (need R&A)
86
Postop plan for rectal, perineal, and anal surgery?
- Monitor for rectal prolapse (may occur secondary to straining due to irritation from surgery)
- Take temperature via thermometer placed in axilla (good idea after all perianal/perineal surgery) rather than rectally
- FOllow-up includes rectal exam 10-14 days post-op to assess healing, serial rectal exams thereafter to monitor for recurrence (frequency will depend on tumor type) and possibly other oncologic therapy as per tumor type
- Review the other post-op pplans to make sure you're thinking about everything
