Term
| What are the roles of the large bowel? |
|
Definition
Modification, storage and evacuation of faeces.
Extraction of water, electrolytes and short chain fatty acids from ileal fluid contents.
Maintenance of bacterial flora and absorption of nutrients derived from bacterial degradation. |
|
|
Term
| What neuronal connections does the myenteric plexus have? |
|
Definition
| Sympathetic and parasympathetic connections, motor connections to longitudinal and circular muscle and secretomotor to mucosa. |
|
|
Term
| What neuronal connections does the submucous plexus have? |
|
Definition
| Parays,pathetic nervous system only, motor to muscularis mucosae and to mucosal receptors |
|
|
Term
| What happens if a n area of colon is aganglionic? |
|
Definition
| Hirschprungs diseas, absent peristalsis. |
|
|
Term
| What is the role of the proximal colon in particular? |
|
Definition
| Fluids and electrolytes absorption and bacterial fermentation. |
|
|
Term
| What is the role of the distal colon in particular? |
|
Definition
|
|
Term
| What factors regulate colonic motility? |
|
Definition
| Myogenic, neurogenic and hormonal factors. |
|
|
Term
| What is the normal colonic transit time? |
|
Definition
|
|
Term
| Where in the colon does non-propulsive segmentation occur? |
|
Definition
| Proximal and distal colon |
|
|
Term
| Which transmitters are stimulatory in colonic motility? |
|
Definition
| Acetylcholine and substance P |
|
|
Term
| Which transmitters are inhibitory in colonic motility? |
|
Definition
|
|
Term
| What is the role of intramural plexi in colonic motility? |
|
Definition
| Directly control contractile behavior. |
|
|
Term
| What is the role of extramural plexi in colonic motility? |
|
Definition
|
|
Term
| In the circular muscle of the colon what electrophysiological signals do interstitial cells produce? |
|
Definition
Interstitial cells (outer border circular muscle) – produce myenteric
potential oscillations – low amplitude but high frequency.
Interstitial cells (inner border of circular muscle) – produce regular
slow waves (3 cycles/min). |
|
|
Term
| What is the role of acetylcholine in the elctrophysiology of the colon? |
|
Definition
| Enhances contractions by increasing the duration of slow waves. |
|
|
Term
| Define constipation and describe the two most common functional changes which cause it? |
|
Definition
Infrequent passage of small amounts of faeces leading two symptoms.
Two mechanisms
-Insufficient luminal residue
-Neuromuscular abnormalities. |
|
|
Term
| What metabolic changes can cause chronic constipation? |
|
Definition
Hypothyroidism
Hypercalcaemia
Hypokalaemia
Uraemia |
|
|
Term
| What idiopathic bowel disorders can cause chronic constipation? |
|
Definition
IBS
Slow transit
Megacolon/rectum |
|
|
Term
| What drugs may cause chronic constipation? |
|
Definition
Opiates
Iron
Ganglion-blockers
Anticholinergics |
|
|
Term
| Stimulation resulting from food results in what colonic function responses? |
|
Definition
Gastro ileal reflex- Caecal and ICV relaxation
Dleyed gastro-colic reflex- gastric distension-> desire to defecate 70-180 minutes after a meal (gastrin)
Neural and hormonal
Food-fat in duodenum |
|
|
Term
| What colonic functional abnormalities may result in diarrhoea? |
|
Definition
Excess liquid due to decrease absorption in small bowel.
Abnormal constituents of faeces.
Abnormal colonic funtion |
|
|
Term
| What two muscle types make up the anal sphincters? |
|
Definition
|
|
Term
| What is the involuntary function of the internal sphincter? |
|
Definition
| Relaxes upon rectal distension in order to aid defecation |
|
|
Term
| Describe the autonomic innervation of the internal sphincter? |
|
Definition
Sympathetic excitatory
Para sympathetic inhibitory |
|
|
Term
| What nerve supplies the striated muscle in the external sphincter? |
|
Definition
|
|
Term
| What six steps result in defecation? |
|
Definition
Cortical perception of rectal filling, probably receptors within the muscles
Voluntary decision
Straining
decreased tone in pelvic floor and sphincters
decreased anorectal angle
increased tone in abdominal musculature |
|
|
Term
| What are the causes of incontinence? |
|
Definition
Neonatal
Cerebral (old age and psychiatric illnes)
Degenerative (Autonomic neuropathy and wasting diseases)
Trauma (Obstetric, surgical and accidents)
Idiopathic
Disease (Anorectal sepsis and IBD) |
|
|
Term
| What four techniques can be used to asses anorectal physiology? |
|
Definition
| Manometry, baloon inflation, pudendal nerve terminal motor latency and EMG (electromyography). |
|
|
Term
| What is manometry and how can it be used to assess anorectal physiology? |
|
Definition
| Pressure transducer, measures resting pressure of internal sphincter and maximum squeeze of external sphincter. |
|
|
Term
| What is a rectocele and how may it cause obstructive defecation? |
|
Definition
Protrusion of anterior rectal/posterior vaginal wall, commonly follows childbirth.
Herniation may lead to obstructed defeacation wiht peak incidence in 40s/50s. |
|
|
Term
| What is rectal intussusception and how may it present? |
|
Definition
Internal rectal prolapse, potentially preliminary to prolapse.
Presents with incomplete evacuation, feeling of rectal fullness, tenesmus and perineal pain. |
|
|
Term
|
Definition
| Idiopathic slow transit constipation. |
|
|
Term
| How does ISTC classically present? |
|
Definition
| Young females, absence of call to stool, abdominal discomfort, family history, bowels open once between 1-2/3 weeks and abnormal motility. |
|
|
Term
| What are the surgical treatments for ISTC? |
|
Definition
Total colectomy & Ileorectal anastomoses
Total colectomy & IS?? |
|
|
Term
| What autoimmine causes are there for large bowel disease? |
|
Definition
| Microscopic colitis (collagneous or lymphocytic colitis) |
|
|
Term
| Describe the epidemiology, presentation and investigations for Microscopic collitis |
|
Definition
Approx 2:100,000, M:F= 1:9, middle aged female
Watery diarrhoea
Histological examination-
- Collagenous: thickened subepithelial collagenous band.
-:Lymphocytic: Increased lymphocyte #. |
|
|
Term
| What idiopathic causes are there of bowel disease? |
|
Definition
|
|
Term
| Decribe the epidemiology, presentation and investigations for UC |
|
Definition
Approx. 11:100,000, young adults, M=F.
Malaise anorexa, weightloss, bloody diarhhoea.
Colonoscopy, histological examination. |
|
|
Term
| Describe the pathology of UC |
|
Definition
Continuous distal to proximal distribution.
Mucosa velvety, congested and bleeds easily.
Superficial ulcers limited to mucosa/submucosa. Can involve muscle and cause perforation in fulminant UC. |
|
|
Term
| Decribe the epidemiology, presentation and investigations for Chrons |
|
Definition
7-8:100,00, Young adults.
Vague pain and mild diahorrea, can develop intestinal obstruction.
Colonoscopy, histological examination. |
|
|
Term
| Decsribe the pathology of chrons |
|
Definition
Segmental (skip lesions)
Initial shallow apthoid ulcers and later longitudinal ulcers and fissures. Full wall thickness involvement.
Transmural inflammation.
Granulomas |
|
|
Term
| What may cause acute ischeamia of the bowel? |
|
Definition
Hernia- strangulation
Volvulus- loop of bowel twists around itself.
Chronic ischaemia |
|
|
Term
| How does chronic colon ischaemia present and where would you normally expect to find it? |
|
Definition
Presents with pain and sometimes diarrhoea.
Splenic flexure at water shed between vascular supply of sup. and inf. mesenteric arteries. |
|
|
Term
| Which colonic infections result in inflammation of the colonic mucosa? |
|
Definition
| Campylobacter, Salmonella and shigella |
|
|
Term
| What infection results in pseudomembranous colitis? |
|
Definition
| Clostridium difficile. Normal commensal affecting 20% of hospitalised patients. |
|
|
Term
| Name a viral cause of colonic inflammation |
|
Definition
|
|
Term
| Name a protazoal cause of colonic infection |
|
Definition
Amoebiasis (Entamoeba histiolytica)
Diarrhoea and dysentry, can develop strictures. |
|
|
Term
| What metabolic causes can result in colonic disease? |
|
Definition
| Diabetes mellitus- disturbed colonic motility, metformin GI disturbance and sugar free sweets containing sorbitol act as a laxative. |
|
|
Term
|
Definition
| Pigmentation of large bowel mucosa due to chronic laxative abuse. |
|
|
Term
| Name a benign neoplastic pathology of the colon |
|
Definition
|
|
Term
| Describe the adenoma -> carcinoma sequence. |
|
Definition
Normal epithelium
Adenoma (low-grade dysplasia)
Adenoma (high-grade dysplasia)
Adenocarcinoma |
|
|
Term
| Describe 2 ways a benign adenoma may present microscopically |
|
Definition
| Tubular, tubulovillous and villous. |
|
|
Term
| Name a malignant neoplastic condition of the colon and what is the most common cause? |
|
Definition
| Adenocarcinoma- 90% develop from adenomas. |
|
|
Term
| What staging system is used to describe colorectal cancer? |
|
Definition
|
|
Term
| Describe dukes stages A-D of bowel cancer. |
|
Definition
Stage A- cancer only on inner lining.
Stage B- Inner layer and muscle lining
Stage C- At least one lymph node involved
Stage D- Spread to at least one more organ. |
|
|
Term
| Name a neoplastic anal malignancy |
|
Definition
|
|
Term
| Name a congenital colonic disease |
|
Definition
Hirschprungs disease
Intestinal atresia
Imperforate anus |
|
|
Term
| Name a degenerative disease of the colon |
|
Definition
|
|
Term
| What is diverticular disease? |
|
Definition
| Herniatation of the mucosa through the bowel wall. This can become inflamed and fibrosed with stricture formation. |
|
|
Term
| Name an endocrine dysfunction which can result in colonic disease? |
|
Definition
Thyrotoxicosis- increased gut motility.
Hypothyroidism- Constipation |
|
|
Term
| Describe the epidemiology, presentation and investigation of IBS |
|
Definition
M:F= 1:4, 20-40YO.
Intermittent long standing consitpation/diarrhoea, abdominal pain/cramps.
Diagnosis of exclusion. |
|
|
Term
| What is familial adenomatous polposis? |
|
Definition
Autosomal dominant condition most commonly due to APC gene mutation.
Develop 100+ adenomas resulting in adenocarcinoma of colon.
Usually have colectomy before 25YO. |
|
|
Term
| What surgical options are there for the treatment of dysmotility? |
|
Definition
| Colectomy &Ileo Rectal Anastomosis, sacral nerve stimulation and antegrade colonic enema |
|
|
Term
| What surgical options are there for the treatment of rectal prolapse? |
|
Definition
| Open rectopexy, perineal procedure and laparoscopic rectopexy |
|
|
Term
| What surgical options are there for the treatment of a rectocele? |
|
Definition
| Transperineal or transvaginal rectocele repair. |
|
|
Term
| Where may evidence of faecal loading/impaction be palpable? |
|
Definition
| Abdomen, internal rectal exam and external anal palpation. |
|
|
Term
| How does a colonic transit study assess constipation. |
|
Definition
Ingestion of capsule containing plastic rings. After 5 days an x-ray is taken. Almost all rings gone= gorssly normal.
Most rings scattered around colon= hypomotility or chronic inertia.
Most rings gathered in rectosigmoid= functional outlet obstruction. |
|
|
Term
| How do bulk-forming laxatives work? |
|
Definition
| Retain fluid in the stool, increase faecal mass and stimulate peristalsis. E.g. ispaghula husk, methylcellulose and sterculia |
|
|
Term
| How do osmotic laxatives work? |
|
Definition
| Increase fluid in large bowel, causes distension, stimulates peristalsis. E.g lactulose, macrogols |
|
|
Term
| How do stimulant laxatives work? |
|
Definition
| Induce peristalsis by stimulating colonic nerves (senna) or colonic and rectal nerves (bisacodyl or sodium picosulfate) |
|
|
Term
| How do surface wetting agents as a laxative work? |
|
Definition
| Reduce surface tension of stool allowing water to soften. E.g. docusate and poloxamer. |
|
|
Term
| Why may an anticholonergic agent such as dicyclomin or hyoscine be used in constipation? |
|
Definition
| Anti-spasmodic smooth muscle relaxant. May however aggravate constipation. |
|
|
Term
| Other than anticholonergics, what other pharmacological agents may be used as antispasmodics in pain management of constipation? |
|
Definition
Antimuscarinic e.g mebeverine, alverine citrate
Peppermint oil- colpermin |
|
|
Term
| Which anti-depressant is the most effective in pain management with constipation? |
|
Definition
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