Hindgut Flashcards
1
Q
What constitutes the hindgut
A
Distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum
2
Q
Length of the large bowel
A
1.5m
3
Q
Distinguishing features of the large bowel
A
- Omental appendices
- Teniae coli
- Haustra
- Greater calibre
4
Q
List the 3 tenia coli
A
- Mesocolic tenia - to which the transverse and sigmoid mesocolons attach
- Omental tenia - to which the omental appendices attach
- Free tenia - to which neither mesocolons or appendices attach
5
Q
Blood supply of the caecum
A
Ileocolic artery (terminal branch of SMA)
6
Q
Venous drainage of the caecum
A
Ileocolic vein (tributary of the SMV)
7
Q
Lymphatic drainage of the caecum
A
Nodes of the mesoappendix and ileocolic nodes
8
Q
Origin of the appendix
A
Posteromedial aspect of the caecum about 2.5cm below the ileocaecal valve
9
Q
Typical position of the appendix
A
Retrocaecal
10
Q
Blood supply to the appendix
A
- Appendicular artery within the mesoappendix
11
Q
Peritoneal covering of the ascending colon
A
- Retroperitoneal
- Covered on the anterior and lateral aspects
12
Q
Posterior relations of the ascending colon
A
- Iliacus
- Quadratus lumborum
- Perirenal fascia over the lateral aspect of the right kidney
13
Q
What separates the ascending colon from the anterolateral abdominal wall
A
Right paracolic gutter
14
Q
Arterial supply of the ascending colon
A
- Ileocolic
- Middle colic
15
Q
Lymphatic drainage of the ascending colon
A
In order:
- Epicolic and paracolic nodes
- Ileocolic and intermediate right colic nodes
- Superior mesenteric nodes
16
Q
Attachments of the transverse colon
A
- Anterior border of the pancreas by the transverse mesocolon
- Diaphragm via phrenicocolic ligament
17
Q
Superior relations of transverse colon
A
- Liver
- GB
- Greater curvature of the stomach
- Spleen
18
Q
Anterior relations of the transverse colon
A
Anterior layers of the greater omentum
19
Q
Posterior relations of the transverse colon
A
- Right kidney
- Second part of duodenum
- Pancreas
- Small bowel
- Left kidney
20
Q
Arterial supply of the transverse colon
A
Mainly via the middle colic artery (branch of the SMA)
21
Q
Lymphatic drainage of transverse colon
A
Middle colic nodes which drain into the superior mesenteric nodes
22
Q
Peritoneal covering of the descending colon
A
- Retroperitoneal
- Covered on its anterior and lateral aspects
23
Q
Posterior relations of the descending colon
A
- Left kidney
- Quadratus lumborum
- Iliacus
24
Q
Course of the sigmoid colon
A
Commences at the pelvic brim and continue to the rectosigmoid junction
25
Significance of the sigmoid mesocolon
Extensive and may precipitate volvulus
26
Male and female relations of the sigmoid colon
- Male = bladder
| - Female = uterus and posterior fornix of vagina
27
Arterial supply of the sigmoid colon
Left colic and sigmoid arteries (branches of the IMA)
28
Venous drainage of the sigmoid
IMV (drains into splenic vein)
29
Lymphatic drainage of the sigmoid
1. Epicolic and paracolic nodes
2. Intermediate colic nodes
3. Inferior mesenteric nodes
30
Describe the course of the rectum
- Commences anterior to 3rd segment of sacrum
| - Ends 2.5cm in front ot the coccyx where it bends backwards to become the anal canal
31
What happens to the tenia coli at the rectum
Form a continuous outer longitudinal layer of smooth muscle
32
Outline the peritoneal coverings of the rectum
- Posterior = extraperitoneal
- Upper 1/3 = covered on front and sides
- Middle 1/3 = covered anteriorly
- Inferior 1/3 = completely extraperitoneal
33
Describe the 3 lateral flexures of the rectum
- Superior and inferior on the left side
- Intermediate on the right
(Correspond to the internal transverse rectal folds)
34
Male anterior relations of the rectum
- Rectovesical pouch
- Base of bladder
- Seminal vesicles
- Prostate
- Denonvilliers fascia separates it from the prostate
35
Female anterior relations of the rectum
- Rectouterine pouch (of Douglas)
| - Posterior wall of vagina
36
Posterior relations of the rectum
Waldeyers fascia lies between recut and sacrum
37
Lateral relations of rectum
Below peritoneal reflection lies the levator ani and coccygeus muscles
38
Outline the blood supply of the rectum
- Proximal = superior rectal (IMA)
- Middle and inferior = middle rectal (anterior division of internal iliac)
- Anorectal junction = inferior rectal (internal pudendal)
39
Blood supply of the anal canal
Inferior rectal artery (branch of internal pudendal)
40
Venous drainage of the rectum
- Superior rectal (drains into portal system via IMV)
- Middle and inferior rectal (drain into systemic system via internal iliac vein)
The walls of the rectum are a site of portosystemic anastomosis
41
Length of the anal canal
4cm
42
Structure of the anal canal
2 layers of circular muscle form the wall:
- Internal sphincter of smooth muscle
- External sphincter of skeletal muscle
43
Columns of Morgani
Columns at the midpoint of the anal canal containing the anal valves of Ball
44
Anal valves of Ball
Contain the sinuses that open the anal glands
45
Histological change at the Dentate line
- Above = columnar
| - Below = squamous
46
Developmental significance of the Dentate line
- Above = endoderm
| - Below = ectoderm
47
Lymphatic drainage of the rectum and anal canal
- Above dentate line = internal iliac nodes
| - Below dentate line = palpable superficial inguinal nodes
48
Innervation of the external anal sphincter
Inferior branches of the pudendal nerve (S2)
49
Mechanism of water absorption in the colon
Na+ is transported from the lumen under the influence of aldosterone and water follows along osmotic gradient
50
Volume of water absorbed in the colon per day
1L
51
3 roles of colonic flora
1. Fermentation of indigestible carbohydrates
2. Degradation of bilirubin
3. Synthesis of vitamin K, B12, thiamine, riboflavin
52
Speed of small bowel transit
5 hours
53
Speed of large bowel transit
20 hours
54
Region of peristalsis and mass movement in the colon
Transverse and distal colon
55
Stimulator of colonic motility
Vagal stimulation
56
How does the colon manipulate gastric motility
Releases Enteroglucagon in response to fat in the ileum/colon which inhibits gastric and small bowel motility
57
Four mechanisms of diarrhoea
1. Osmotic
2. Secretory
3. Inflammatory
4. Abnormal motility
58
8 essential amino acids
1. Isoleucine
2. Leucine
3. Lysine
4. Methionine
5. Phenylalanine
6. Threonmine
7. Tryptophan
8. Valine
59
Roles of fats
- Support of other tissues (e.g. perirenal)
- Stores fat-soluble vitamins
- Nerve sheaths
- Cell membranes
60
Where is the hunger/feeding centre
Lateral hypothalamus
61
Where is the satiety centre
Ventromedial hypothalamus
62
How is the satiety centre activated
By high blood glucose levels post-meal and gastric distension
63
Define Crohn's disease
Transmural inflammatory bowel disease
64
Define UC
Mucosal inflammatory bowel disease
65
What percentage of UC cases spread beyond the splenic flexure
15%
66
Most common site of CD
Terminal ileum
67
Histological features of CD
- Whole thickness of bowel
- Chronic = hosepipe thickening with fibrosis
- Cobblestone
- Deep fissuring ulcers
68
Histological features of UC
- Limited to mucosa (not affecting muscularis propria)
- Pseudo-polyps
- Small shallow ulcers
69
Microscopic features of CD
- Non-caseating epitheloid granulomas
- Transmural
- Lymphoid follicles
- Mucosal crypt distortion
70
Microscopic features of UC
- Inflammatory infiltrate confined to lamina propria
- Crypt abscesses
- Crypt distortion
- Metaplasia and dysplasia
71
Sexual distribution of IBD
- CD more common in women
| - UC equal
72
Percentage of CD patients with perianal disease
75%
73
Extra-intestinal manifestations of CD
- Gallstones
| - Oxalate renal stones
74
Extra-intestinal manifestations of UC
- PSC
75
General extra-intestinal features of IBD related to disease severity
- Skin = pyoderma gangrenosum, erythema nodosum
- Mucous membranes = apthous ulcers of mouth and vagina
- Eyes = iritis
- Joints = activity-related arthritis
76
CD Barium enema features
- Skip lesions
- Rectal sparing is common
- Cobblestone appearance
- Rose-thorn ulcers
- Fistulas
- Strictures
77
UC Barium enema features
- Hosepipe colon
- Decreased haustrae
- Affects rectum and spreads proximally
- Mucosal distortion
- Pseudo polyps
- Shortened colon
78
Medical management of severe UC
- Topical and oral mesalazine
- Oral steroids
- IV steroids
- Ciclosporin and infliximab
79
Medical management of severe CD
- IV hydrocortisone
- PR hydrocortisone
- Metronidazole
- Infliximab/Adalimumab
80
Mechanism of action of Ciclosporin
Interferes with lymphocyte activation
81
What needs to be checked before commencing Azathioprine
TPMT
82
Principles of CD surgery
- As limited as possible
| - Bowel-preserving procedures wherever possible (e.g. stricturoplasty)
83
Principles of UC surgery
- Radical
| - Removal of diseased segment should provide cure
84
What is the typical operation for UC (middle-aged and elderly patients)
Proctocolectomy with ileostomy
85
Best operation for UC in younger patients
Sphincter-preserving proctocolectomy with ileal pouch
86
Site of pouch anastomosis in sphincter-preserving proctocolectomy
Dentate line
87
Procedure for toxic megacolon
Subtotal colectomy with ileostomy +/- mucous fistula
88
Complications of UC
- Toxic megacolon
- Perforation
- Haemorrhage
- Malignant change
89
Complications of CD
- Small-bowel strictures
- Fistulation
- Perianal sepsis
- Perforation
90
Of patients with UC for 20 years, what proportion will develop malignancy
12%
91
Investigation to identify strictures in CD
Contrast studies
92
Medication used for prophylaxis of perianal disease in CD
Metronidazole
93
What percentage of colon cancers are distal to the splenic flexure
75%
94
Three characteristics of colonic adenomas that correlate with malignant change
1. Size
2. Villious architecture
3. Dysplasia
95
Most common site of colon cancer
Sigmoid colon
96
What proportion of colorectal cancers are associated with genetic factors
24%
97
Proportion of colorectal cancer patients with synchronous tumours
3-5%
98
Incidence of metachronous colorectal tumours
3% at 10-years post-treatment of the first tumour
99
Outline the 5 methods of colorectal cancer spread
1. Direct
2. Lymphatic
3. Blood-borne
4. Transcoelomic
5. Implantation
100
Necessary resection margin for colorectal cancer
2cm
101
How does colorectal cancer spread to the liver
- Blood-borne
| - Via the portal vein
102
Dukes A
Tumour confined to the mucosa
103
Dukes B1
Tumour growth into muscularis propria
104
Dukes B2
Full thickness tumour growth
105
Dukes C1
1-4 regional lymph nodes
106
Dukes C2
More than 4 regional lymph nodes
107
Dukes D
Distant metastasis (lung, liver, bone)
108
R1 resection
Shows tumour at the resection margin = residual local disease (uncurable)
109
R0 resection
Curative operation
110
Non-genetic risk factors for colorectal cancer
- Lack of fibre
- High-fat diet
- High level of bile acid
- Previous cholecystectomy
111
Procedure for obstructing colonic tumours
De-functioning loop colostomy
112
Adenoma with greatest malignant potential
Villous adenomas (40%)
113
Cause of pseudopolyps
Inflammatory - associated with UC
114
FAP inheritance pattern
Autosomal dominant
115
Site and name of gene responsible for FAP
- Long arm of chromosome 5
| - APC
116
Features of Gardner's syndrome
- FAP related
- Desmoid tumours
- Osteomas of the mandible (extra teeth)
- Sebaceous cysts
117
HNPCC inheritance pattern
Autosomal dominant
118
Genes implicated in HNPCC
- hMSH 2
- hMLH 1
- hPMS 1 and hPMS 2
119
Average age of diagnosis of HNPCC
45 years
120
HNPCC extra-colonic associated cancers
- Endometrial - 20-40%
- Ovarian - 10%
- Gastric - 6%
- Biliary tract - 4%
- Brain - 1%
- Small bowel - 1%
121
Most likely site of HNPCC
Proximal colon
122
Outline the Amsterdam criteria for HNPCC
- 3 or more family members with colorectal cancer
- Colorectal cancer extending over 2 generations
- One or more affected by 45
- One affected relative is a first-degree of the other two
- Exclusion of FAP
123
Bowel preparation for colonic resections
- 1 day of liquid diet
| - 2 sachets of sodium picosulphate beforehand
124
Curable procedure for non-obstructed right colon tumours
Right hemicolectomy and primary anastomosis sparing the middle colic arteries
125
Curable procedure for non-obstructed transverse/splenic flexure tumours
Extended right hemicolectomy taking the middle colic arteries
126
Curable procedure for non-obstructed sigmoid, middle/upper rectal tumours
Anterior resection taking the IMA and its sigmoid and upper rectal branches
127
Curable procedure for low rectal and anorectal tumours
AP resection and end colostomy taking the IMA and meticulous dissection of the mesorectal fat and lymph nodes
128
What does ELAPE entail
Rectum, anus, sphincter, and levator muscles are taken en block with AP resection
129
Which rectal cancers can proceed straight to surgery
T1-3/N0
130
Management of T4 rectal cancer
- Neoadjuvant long course chemoradiotherapy
| - Resection
131
Most common site of distal mets in colorectal cancer
Liver (sometimes lungs)
132
Management of liver metastases in rectal cancer
Solitary lesions can be resected
133
Management of FAP
1. Genetic testing if at risk
2. Annual flexi sig from 15
3. If no polyps - 5 yearly colonoscopy from 20
4. Polyps found = prophylactic panproctocolectomy
134
Management of HNPCC
1. Colonoscopy every 1-2 years from 25
2. Consider panproctocolectomy
3. Extra-colonic surveillance
135
Colonoscopy high risk polyp findings
- More than 2 premalignant polyps including 1 or more advanced polyps, OR
- More than 5 pre-malignant polyps
136
Follow-up plan if high risk polyps identified at colonoscopy
One off surveillance scope at 3 years
137
Post-operative antibiotics after colonic resection
3 doses of cef and met
138
Features of anastomotic leak
- Occurs 7-10 days post-op
- Risk is higher in low anastamosis
- Results in pelvic abscess, fistulation, death
139
What cardiac condition is associated with angiodysplasia
Aortic stenosis
140
How is angiodysplasia investigated
1. Colonoscopy
| 2. Mesenteric angiography if acutely bleeding
141
How is angiodysplasia managed
1. Endoscopic cautery or argon plasma coagulation
| 2. TXA and oestrogens
142
What is the most common causes of mesenteric ischaemia
Embolus
143
How does acute mesenteric ischaemia present
- Sudden onset abdominal pain
- Followed by profuse diarrhoea
- Rapid clinical deterioration
144
How does chronic mesenteric ischaemia present
Post-prandial abdominal pain and weight loss dominate
145
What is the GOLD standard investigation for arterial and venous mesenteric disease
CT angiogram in the arterial phase (with thin slices <5mm)
146
How is mesenteric vein thrombosis managed
If no peritonism - IV heparin
147
Define haemorrhoids
Enlargement and distal displacement of the normal arteriovenous anal cushions
148
Where are the vascular cushions of the rectum located
- 3 o'clock
- 7 o'clock
- 11 o'clock
149
What supplies the cushions of the rectum
Superior rectal artery branches
150
What predisposes to haemorrhoids
- Pregnancy
- Cardiac failure
- Excessive use of purgatives
- Chronic constipation
- Portal hypertension
151
Outline the classification of haemorrhoids
- 1st degree = confined to anal canal
- 2nd degree = prolapse on defaecation, spontaneously reduce
- 3rd degree = prolapse spontaneously, digitally reduced
- 4th degree = irreducible
152
How may 1st degree haemorrhoids be managed
Conservatively with increasing fibre content of diet or use of bulking agents
153
When is banding or injection sclerotherapy indicated
- 1st/2nd degree resistant to medical intervention
| - 3rd/4th in those reluctant to undergo surgery
154
In who is haemorrhoid banding contraindicated
- Warfarin
- Clotting disorder
- Immunosuppressed
155
Where does the injection/banding take place with respect to the dentate line
Above
156
How many haemorrhoids should be treated in one go
No more than 3
157
How should 3rd degree haemorrhoids that straddle the dentate line or that are too large to band be treated
Milligan-Morgan Haemorrhoidectomy
158
Describe fissure in ano
Longitudinal tear of the squamous-lined lower half of the anal canal from the anal verge towards the dentate line
159
Where is the most common site of fissure in ano
In the midline posteriorly
160
Presentation of fissure in ano
- Pain on defaecation
- Bright-red rectal bleeding
- Constipation secondary to pain
- Pruritus
- Watery discharge
161
When does a sentinel pile form
When the skin at the base of the fissure becomes oedematous and hypertrophied
162
Outline the management of fissure in ano
- 1st line = GTN paste OR diltiazem cream
- EUA to exclude cancer is a must
- Lateral-sphincterotomy
163
What typically causes an anorectal abscess
Infection of one of the 10-12 anal glands that lie in the intersphincteric space
164
How are anorectal abscesses managed
I+D under GA
165
Describe I+D of anorectal abscess
- Incise at point of maximum tenderness
- Explore cavity with finger
- Excise corners of cruciate excision and de-roof cavity
- Pack with ribbon gauze soaked in betadine
- Do NOT probe suspected fistulas
166
What conditions are associated with anal fissures
- STI
- CD
- Leukaemia
- TB
- Previous anal surgery
167
Describe chronic intersphincteric abscess
- Intersphincteric abscess is walled off by fibrosis and does not track to the exterior
- Bouts of anal pain without discharge
- Internal opening lies posteriorly in the midline
168
What is the most common type of anorectal fistula
Intersphincteric
169
What percentage of recurrent anorectal abscesses are associated with a fistula
80%
170
What causes anorectal fistulas
- Anorectal abscesses
- CD
- TB
- Trauma
- Radiotherapy
- Carcinoma
171
Where does the internal opening of an anorectal fistula most commonly lie
Posteriorly in the midline
172
Describe Goodsall's rule
* External opening posterior to the transverse anal line – fistula tract will follow a curved course to the posterior midline
* External opening anterior to the transverse anal line – fistula tract will follow a straight radial course to the dentate line
173
How are anal fistulas investigated
- Proctoscopy
| - MRI
174
How are suprasphincteric and high trans-sphincteric fistulas managed
Seton suture
175
How are low anorectal fistulas managed
Fistulotomy - laying open the tract by cutting through the skin and subcutaneous tissue allowing it to heal by secondary intention
176
Describe pilonidal sinus
A subcutaneous sinus that contains hair, and is most commonly found in the natal cleft associated with chronic inflammation and acute abscess formation
177
Definitive treatment for pilonidal sinus
Bascom procedure with excision of the pits and obliteration of the underlying cavity (definitive treatment should never be undertaken whilst acute infection or abscess is present)
178
How should acute pilonidal sinuses be managed
Incision and drainage
179
Describe the 3 types of rectal prolapse
1. Complete prolapse - full thickness of the rectum prolapses through the anus (prolapse contains two layers of rectum with intervening peritoneal sac)
2. Incomplete prolapse - the prolapse is limited to two layers of mucosa, often associated with haemorrhoids
3. Concealed prolapse - internal intussusception of the upper rectum into the lower rectum
180
List the risk factors for rectal prolapse
- Multiparity
- Pelvic floor trauma
- Connective tissue disorders
181
How are internal rectal prolapses diagnosed
Defecating proctography and EUA
182
How is rectal prolapse managed
- Delormes operation (perineal approach)
| - Rectopexy (abdominal procedure)
183
Most common type of anal cancer
SCC
184
Lymphatic spread of anal cancer
- Below dentate line (anal margin cancer) = inguinal nodes
| - Above dentate line (anal canal cancer) = internal iliac nodes
185
Who is predisposed to anal cancer
- Male homosexuals
- People who practice anal sex
- People with a history of genital warts (HPV 16)
186
1st line management of anal cancer
Chemoradiotherapy
187
2nd line management of anal cancer
Salvage radical AP resection of anus and rectum
188
Level of the IMA
L3
189
Formation of the IVC level
L5
190
Where do the teniae coli converge
Base of the appendix
191
How is the caecum mobilised in appendicectomy
By division of the lateral peritoneal attachments
192
Eponymous name for pseudo-obstruction
Ogilvies syndrome
193
How should appendix mass be managed
Conservatively unless perforated
194
What part of the large bowel is spared from diverticulosis
Rectum
195
What causes Rovsing's sign
Any progressed RIF pathology
196
Where are colonic tumours most likely found in HNPCC Lynch syndrome
Right-sided
197
How is nodal disease in colorectal Ca managed
Chemotherapy
198
What colonic disorder is caused by laxative abuse
Melanosis coli
199
What vascular condition can complicate major abdominal sepsis causing bowel necrosis
Mesenteric vein thrombosis
200
Characteristics of mesenteric cyst
Mobile RIF mass in children
201
When can you eat after uncomplicated bowel anastomosis
Within 24 hours
202
Describe Cowden disease
PTEN mutation causing hamartomatous polyps
203
Lynch syndrome inheritance
Autosomal dominant
204
Earliest complication of ileostomy
Necrosis
