Flashcards in Gastroenterology - Disorders of the colon and rectum Deck (54):
What is the main function of the large intestine?
The main role of the colon is absorption of water and electrolytes and propulsion of contents from the ceacum to the anorectal region. About 9000ml of water containing electrolytes enters the GIT each day; the majority from gastrointestinal secretions (stomach, pancreas, bile, intestinal secretion) and only a small amount from the diet. Most is absorbed in the small intestine and only about 1500ml passes through the ileocaecal valve into the colon, of which about 1350ml is normally absorbed.
What is constipation?
This is a consistent difficulty in defecation. It is common in the elderly (associated with immobility and poor diet) and in young women (associated with slow transit or post partum pelvic floor abnormalities).
Specific definitions are infrequent passage of stools (<3/week - Rome criteria), straining, passage of hard stools, incomplete evacuation and sensation of anorectal blockage. In many patients it is part of IBS.
In the elderly, constipation can present as:
- overflow diarrhoea
- abdominal pain
- urinary incontinence
What is functional constipation?
This is chronic constipation without a known cause. It is also known as primary constipation or idiopathic constipation.
What is secondary constipation?
This is constipation caused by drugs or other medical conditions. It is also known as "organic constipation".
What is faecal loading, or impaction?
This is retention of faeces to the point that spotaneous evacuation is unlikely. Retained faeces are usually palpable on abdominal examination, and may be felt on internal rectal examination.
What is meant by the term overflow incontinence?
This is the leakage of loose stools around impacted faeces. Small quantities of stool are passed frequently and without sensation. It is also known as "bypass soiling"
What is a normal frequency of bowel movements in adults?
Bowel movements occurring less than 3 times per week is one of the Rome criteria for constipation
What causes of secondary constipation should I consider in adults?
What drugs are associated with constipation?
Many drugs are constipating, some of the most common are:
Antimuscarinics (e.g. procyclidine)
Antidepressants (most commonly TCAs)
Some antiepileptics (e.g. carbamazepine, gabapentin)
What factors predispose to constipation in adults?
- mild pyrexia, dehydration, immobility
- position for defecation
- eating disorders
- low fibre diet
- lack of exercise or reduced mobility
What organic causes of secondary constipation should I consider in adults?
In adults with no drug causes for their constipation, consider:
1) Endocrine and metabolic - diabetes, hypercalcaemia, hypokalaemia, uraemia, hyperparathyroidism
2) Myopathic conditions - amyloidosis, myotonic dystrophy
3) Neurological disease - autonomic neuropathy, CVA, MS, Hirschsprungs disease, PD
4) Structural problems - anal fissures, strictures, haemorrhoids, colonic strictures (following diverticulitis surgery), cancer, IBD
How do I know my patient has constipation?
Constipation is diagnosed in adults when defecation is unsatisfactory because of infrequent stools, difficult stool passage, or seemingly incomplete defecation.
In the elderly constipation may present as confusion, overflow diarrhoea, abdominal pain, urinary retention.
Functional constipation is diagnosed by ruling out drug or organic causes of constipation.
How is faecal loading/ impaction diagnosed?
On history. The person reports:
- passing hard, lumpy stools, either large and infrequent (for example every 7–10 days), or small and relatively frequent (for example every 2–3 days).
- having to use manual methods to extract faeces.
- overflow faecal incontinence, or loose stool
- faecal masses are palpable abdominally or peri-anally, or on internal rectal examination
What investigations should I make to diagnose constipation?
Initial evaluation is with history and examination, include DRE during which the patient should be asked to strain. A patient with a defecatory disorder has paradoxical contraction rather than normal relaxation of the puborectalis and external anal sphincter during straining, which may prevent defecation.
Routine blood tests, radiography and endoscopy are not usually indicated in the evaluation of patients with constipation without alarm symptoms: these include
- rectal bleeding
- recent onset constipation in middle aged (>55), esp if associated with sense of incomplete evacuation
How should I manage short term constipation in adults?
Adjust any constipation causing medication
Dietary advice about increasing fibre and adequate fluid intake
Oral laxatives if dietary measures are ineffective:
- start treatment with bulk forming laxative (adequate hydration is necessary)
- if stools remain hard, switch to osmotic laxative
- if stools are soft but patient still finds it hard to pass, add a stimulant laxative
If a person has opioid induced constipation:
- avoid bulk forming laxatives
- use an osmotic laxative and a stimulant laxative
Advise the patient that laxatives can be stopped once stools become soft and are easily passed.
How should I manage chronic constipation in adults?
Laxatives are indicated if:
- lifestyle measures are insufficient
- for people taking a constipating drug that cannot be stopped
- for people with secondary causes of constipation
- as "rescue" medications in patients with faecal loading
Start treatment with a bulk forming laxative (maintain hydration).
If stools remain hard, switch to osmotic laxative, macrogol is first line, lactulose second.
If stools are soft but the person is still finding them difficult to pass, then add a stimulant laxative.
The dose of laxative can be up or down titrated to achieve 1-2 soft stools per day.
What agent can be considered If at least two laxatives (from different classes) have been tried at the highest tolerated recommended doses for at least 6 months?
Prucalopride (women only)
- invasive methods should be considered
- reassess if no result after 4 weeks
- invasive methods should be considered
- reassess if no result after 2 weeks
Both have NICE prescribing criteria.
How should I manage faecal loading/ impaction in adults?
For hard stools consider using high doses of oral macrogols.
For soft stools or hard stools that persist after a few days of macrogol therapy, consider adding a stimulant laxative.
If response to oral agents is insufficient, consider:
- a suppository - e.g. bisacodyl
- a mini enema - e.g. docusate
If response is still insufficient consider using an enema (sodium phosphate), needs to be repeated multiple times
When and how should I stop treatment for chronic constipation in adults?
Laxatives can be slowly withdrawn when regular bowel movements occur without difficulty (for example, 2–4 weeks after defecation has become comfortable and a regular bowel pattern with soft, formed stools has been established).
The rate at which doses are reduced should be guided by the frequency and consistency of the stools. Weaning should be gradual in order to minimize the risk of requiring 'rescue therapy' for recurrent faecal loading. Laxative medication should not be suddenly stopped.
If a combination of laxatives has been used, reduce and stop one laxative at a time. Begin by reducing stimulant laxatives first, if possible. However, it may be necessary to also adjust the dose of the osmotic laxative to compensate.
What is faecal incontinence?
This is recurrent, uncontrolled passage of stool or flatus. continence depends on a number of factors, including mental function, stool volume, and consistency, structural and functional integrity of the anal sphincters, puborectalis muscle, pudendal nerve function, and anorectal sensation.
Faecal impaction is a common cause of faecal incontinence in the elderly. Anal sphincter tears or trauma to the pudendal nerve can occur after childbirth or anal surgery (e.g. for haemorrhoids). Impaired rectal sensation occurs with diabetes mellitus, multiple sclerosis, dementia and spinal cord injuries.
Detailed investigations are needed to confirm the underlying cause.
What is diverticular disease?
Pouches of mucosa extrude through the colonic muscular wall via weakened areas near blood vessels to form diverticula. The term diverticulosis means the presence of diverticula. Diverticular disease is a condition where diverticula cause intermittent lower abdominal pain, without inflammation and infection. Diverticulitis refers to inflammation, which occurs when faeces obstruct the neck of the diverticulum. Diverticula are common, affecting 50% of the population over 50 years of age.
What is the aetiology of diverticular disease?
The aetiology is unknown, although it appears to be related to a low fibre diet eaten in Western populations. Insufficient dietary fibre leads to increased intracolonic pressure, which causes herniation of the mucosa at sites of weakness.
What are the clinical features of diverticular disease?
Diverticulosis is asymptomatic and in most people remains undiagnosed. It may present with a large, painless rectal bleed, or be revealed by investigations for other problems.
Diverticular disease is characterised by intermittent pain in the lower abdomen, usually in the left lower quadrant, which is tender on examination. Pain may be brought on by eating, and may be relieved by the passage of stool or flatus.
Constipation, diarrhoea, or occasional large rectal bleeds.
Bloating and the passage of mucus rectally.
Diverticulitis presents with left iliac fossa pain, fever and nausea and may result in perforation (leading to abscess formation or peritonitis), fistula formation into the bladder or vagina or intestinal obstruction.
How is diverticular disease diagnosed?
Diverticular disease is confirmed in the presence of characteristic symptoms by CT, barium enema or colonoscopy once other causes of abdominal pain are excluded. Frequent, small bleeds are unlikely to be diverticular and require investigation for other causes.
Acute diverticulitis is diagnosed by CT or in some cases ultrasound.
What is the differential diagnosis for diverticular disease?
For people with lower abdominal pain enquire about other symptoms, and examine and investigate if necessary to exclude other causes.
Other abdominal causes include:
- Irritable bowel syndrome.
- Bowel cancer.
Gynaecological causes include:
- Pelvic inflammatory disease.
- Ovarian cyst.
- Ovarian torsion.
- Ectopic pregnancy.
Urological causes include:
- Urinary tract infection, including pyelonephritis.
- Urinary tract obstruction, including ureteric stone.
For people with alteration of bowel habit or rectal bleeding enquire about other symptoms, and examine and investigate if necessary to exclude:
- Bowel cancer.
How do I manage diverticulosis?
Asymptomatic diverticulosis that is an incidental finding does not require any further investigation.
Advise a high fibre diet to reduce the risk of developing symptomatic diverticular disease.
No further follow up or treatment is needed.
How do I manage diverticular disease?
Arrange admission for patients with significant blood loss, as transfusion may be required.
Advise a high fibre diet if tolerated, with adequate fluid intake. It may take up to 4 weeks for effect to be noticed. Consider bulk forming laxatives if a high fibre diet is insufficient.
Prescribe paracetamol for the pain. AVOID opiates or NSAIDs as these increase the likelihood of diverticular perforation.
Review if symptoms persist after one month and:
- review compliance with dietary advice
- reconsider the diagnosis
- trial of therapy for IBS if this has not been previously undertaken
How do I manage patients with diverticulitis at home?
People with mild, uncomplicated diverticulitis can be managed at home with paracetamol, clear fluids and oral antibiotics.
Antibiotics include co amoxiclav or a combination of metronidazole and ciprofloxacin (if penicillin allergic) for 7 days.
Paracetamol is preferred for pain relief.
Recommend clear fluids only, solids can be reintroduced after 2-3 days.
Review within 48 hours.
When should I admit someone with diverticulitis?
Pain cannot be managed with paracetamol.
Hydration cannot be easily maintained with oral fluids, or oral antibiotics cannot be tolerated.
The person is frail or has a significant comorbidity that is likely to complicate their recovery, particularly if they are immunocompromised (for example severe infection; diabetes mellitus; renal failure; malignancy; cirrhosis; or the use of oral corticosteroids, chemotherapy, or immunosuppressive drugs).
The person has any of the following suspected complications:
- Rectal bleeding that may require transfusion.
- Perforation and peritonitis.
- Intra-abdominal abscess.
Symptoms persist after 48 hours despite conservative management at home.
How is acute diverticulitis managed in secondary care?
Initial treatment is with oral antibiotics (amoxicillin + metronidazole for 7-10 days).
This can progress to a pericolic abscess (Hinchey Ia). The patient has a swinging fever and is tachycardic. There may also be a palpable mass in the LIF. Treatment is with antibiotics and CT to confirm.
This can then progress to a paracolic abscess (Hinchey Ib), where the pulse is swinging and the patient remains tachycardic. Treatment is with antibiotics and drainage, either surgically or guided. Surgical treatment involves laproscopic peritoneal lavage and drainage or resect the disease segment and primary anastomosis with defunctioning proximal stoma.
The paracolic abscess can perforate leading to purulent peritonitis (Hinchey III) or faecal peritonitis (Hinchey IV). A upright CXR is needed and treatment is Hartmanns procedure in both cases.
What is megacolon?
This term describes a number of conditions in which the colon is dilated. The most common cause is chronic constipation. Other causes are Chagas’ disease and Hirschsprung’s disease (congenital aganglionic segment in the rectum). Treatment is with laxatives, although Hirschsprung’s disease responds to surgical resection.
What is the definition of bowel obstruction?
Complete intestinal obstruction indicates total blockage of the intestinal lumen, whereas incomplete denotes only partial blockage.
Obstruction may be acute (hours) or chronic (weeks), simple (mechanical - i.e. blood supply is not complicated) or strangulated (i.e. blood supply is compromised). A closed loop obstruction indicates that both the inlet and outlet portion of bowel is closed off. A volvulus is an abnormal twisting of a segment of bowel causing intestinal obstruction and possible ischaemia and gangrene of the twisted segment.
What are the causes of bowel obstruction?
Causes due to pathology in the wall, within the bowel or without.
1) Wall - tumour, stricture, diverticular, ischaemia, Crohn's intussusception
2) Within - gall stone, faces, bezoar, foreign body, meconium
3) Without - adhesions, hernia, volvulus (caecal, sigmoid, small bowel), lymphoma/ nodes
Small bowel obstruction is often rapid in onset and commonly due to adhesions or hernia.
Large bowel obstruction may be gradual or intermittent in onset, is often due to carcinoma or strictures and never due to adhesions alone.
What is the pathophysiology of bowel obstruction?
Bowel distal to the obstruction collapses.
Bowel proximal to the obstruction distends and becomes hyperactive. Distension is due to swallowed air and accumulating intestinal secretions.
The bowel wall becomes oedematous. Fluid and electrolytes accumulate in the wall and lumen (third space loss).
Bacteria proliferate in the obstructed bowel.
As the bowel distends, the intramural vessels become stretched and the blood supply is compromised, leading to ischaemia, necrosis and perforation.
Patients may also be acidotic and hypokalaemic.
What are the clinical features of bowel obstruction?
4 key features are:
2) Colicky abdominal pain
3) Abdominal distension
4) Absolute constipation
These do not all need to be present at once. There may also be abdominal distension and increased bowel sounds, dehydration and loss of skin turgor, hypotension and tachycardia.
Vomiting can be a useful indicator of the location, as it occurs early in high (upper GI) obstructions and later in lower GI obstructions. It also tends to be fecculent in lower GI obstruction.
How should I investigate bowel obstruction?
FBC - PCV due to dehydration, WCC normal or raised
U+E - urea elevated, Na+ and Cl- low
CXR - elevated diaphragm due to abdominal distension
Abdominal supine X ray
- small bowel: meandering, central, contains gas/fluid, distended >3cm, valvulae conniventes visible
- large bowel: straight, peripheral/ central, contains gas/faeces, distended >6cm, haustral folds
Contrast CT is the 1st line investigation for ALL suspected bowel obstruction - site and cause
How do I manage a large bowel obstruction?
Decompress the obstructed gut - pass nasogastric tube
Replace fluid and electrolyte loss - Ringer's lactate or NaCl with K+ supplementation
Give IV antibiotics if ischaemia suspected
Monitor the patient - fluid balance, urinary catheter, regular TPR chart
Request investigations most appropriate to likely cause
Relieve the obstruction surgically, if:
- underlying cause needs surgical treatment (e.g. hernia, colonic carcinoma)
- patient does not improve with conservative treatment (e.g. adhesion obsruction)
- signs of strangulation or peritonitis
What is a functional bowel obstruction?
This occurs with a paralytic ileus, which is often seen in the post-operative stage of peritonitis or of major abdominal surgery, or in association with opiate treatment (acute colonic pseudo-obstruction, Ogilvie’s syndrome). It also occurs when the nerves or muscles of the intestine are damaged, causing intestinal pseudo-obstruction. Unlike mechanical obstruction, pain is often not present and bowel sounds may be decreased. Gas is seen throughout the bowel on a plain abdominal X-ray. Management is conservative.
What distinguishes a small from a large bowel obstruction?
In small bowel obstruction, vomiting occurs earlier, distension is less and pain is higher in the abdomen. The AXR plays a key role in diagnosis. In small bowel obstruction, AXR shows central gas shadows with valvulae conniventes that completely cross the lumen and no gas in the large bowel. In large bowel obstruction pain is more constant. AXR shows peripheral gas shadows proximal to the blockage but not in the rectum. ALWAYS DO A PR! Large bowel haustra do not cross the lumens width.
What is an ileus? How can it be distinguished from pseudo obstruction?
Paralytic Ileus is a functional obstruction from reduced bowel motility. There is no pain and the bowel sounds are present. Contributing factors include abdominal surgery, pancreatitis (or any localised peritonitis) spinal injury, hypokalaemia, hyponatraemia, uraemia and drugs (e.g. TCAs).
Pseudo-obstruction is like mechanical GI obstruction but with no cause found. Acute colonic pseudo-obstruction is called Ogilvie's syndrome and clinical features are similar to that of mechanical obstruction. Treatment is with neostigmine or colonoscopic decompression.
What is the difference between simple, closed loop and strangulated obstruction?
Simple = one obstructing point and no vascular compromise
Closed loop = obstruction at two points (e.g. sigmoid volvulus) forming a loop of grossly distended bowel at risk of perforation, if >12 cm requires urgent decompression
Strangulated = blood supply is compromised and the patient is more ill than you would expect. There is sharper, more constant and localised pain. Peritonism is the cardinal feature
Outline the general management of bowel obstruction.
Cause, site, speed of onset and completeness of obstruction determine definitive therapy: strangulation and large bowel obstruction require surgery, ileus and incomplete small bowel obstruction can be managed more conservatively.
Immediate action - "drip and such" - NGT and i.v. fluids to rehydrate and correct electrolyte imbalance. Also: analgesia, blood tests (inc. amylase, FBC, U&E) AXR, erect CXR, catheterise to monitor fluid status
Further imaging. Consider early CT if clinical and radiographic findings are inconclusive. It finds the cause and level of obstruction
When is surgery needed for bowel obstruction?
Strangulation needs emergency surgery, as does "closed loop obstruction:. Stents may be used for obstructing large bowel malginancies either in palliation or as a bridge to surgery in acute obstruction. Small bowel obstruction secondary to adhesions should rarely lead to surgery.
What are the risk factors for gastric volvulus?
Gastric volvulus is rare. Rotation is typically 180 degrees about a line joining the pylorus and oesophagus. This creates a closed loop obstruction leading to incarceration and strangulation. A triad of vomiting, pain and failed attempts to pass an NG tube follow. Regurgitation of saliva also occur.
Risk factors are:
- congenital: paraoesophageal hernia, congenital bands, bowel malformations, pyloric stenosis
- acquired: gastric/ oesophageal surgery
What causes pruritis ani? How is it treated?
This is anal itch and can be caused by a number of things, including moisture/ soiling; incontinence; fissures; poor hygeine; threadworn; fistula; dermatoses; lichen sclerosis etc. Cause is often unknown. Treatment is with careful hygiene, anaesthetics cream, and moist wipe post defacation. No antibiotic or steroid creams are needed.
What is a fissure-in-ano?
This is a painful tearing in the squamous lining of the lower anal canal. If it is chronic there can be a "sentinal pile" or mucosal tag at the external aspect. It happens in men more than women and 90% are posterior.
Most are caused by hard faeces. Rare causes (multiple and lateral) are syphilis, herpes, trauma, Crohn's, anal cancer, psoriasis.
How is a fissure-in-ano treated?
Treatment is 5% lidocaine ointment + GTN ointment or topical diltiazam. Patients should be advised to increase dietary fibre, take fluids and stool softeners. Botulinum toxin and topic diltiazem are at least as effective as GTN and have fewer side effects. If conservative measures fail, surgical options include lateral partial internal sphincterotomy.
What is a fistula-in-ano? What is Goodsall's rule?
A fistula-in-ano is a track that communicates between the skin and the anal canal/ rectum. Blockage of deep intramuscular gland ducts is thought to predipose to the formation of abscesses, which discharge to form a fistula. Causes include perianal sepsis, Crohn's disease, TB, diverticular disease, and immunocompromise.
Goodsall's rule determines the path of the fistula track: if anterior the track is in a straight line (radial), if posterior the internal opening is always at the 6 o'clock position. Treatment is fistulotomy and excision.
What causes an anorectal abscess?
These are usually caused by gut organisms (rarely staphs or TB). They are associated with DM, Crohns, malignancy and fistulae. Peri-anal is most common. Treatment is incision and drainage under GA.
Wha is a perianal haematoma?
This is a thrombosed external haemarrhoid. Strictly it is actually a clotted venous saccule. It appears as a 2-4mm dark blueberry under the skin at the anal margin. It can be removed under local or left to resolve spontaneously.
What is a pilonidal sinus? How is it treated?
This is obstruction of natal cleft hair follicles 6cm above the anus. Ingrowing of hair excites a foreign body reaction and may cause secondary tracks to open laterally and abscess with foul smelling discharge. Treatment is with excision of the sinus tract and primary closure. Pre op antibiotics can be considered.
What are the different types of rectal prolapse?
The mucosa (partial/ type I) or all layers (complete/ type 2 - more common) may protrude through the anus. Incontinence occurs in 75%. It is caused by a lax sphincter, prolonged straining and related chronic neurological and pscyhological disorders. Treatment is surgery and can be from either an abdominal approach or a perineal approach. In the abdominal approach the rectum is fixed to the sacrum. In the perineal approach (called Delorme's procedure) the prolapse is resected close to the dentate line and the mucosal boundaries are sutured.
How are anal warts treated?
Anal warts or condylomata acuminata are treated with podophyllotoxin or imiquimod or cryotherapy. Giant condylomata acuminata of Bushke and Loewenstein may evolve into verrucous cancers.