Distal Tract Pathologies

Functions of the appendix

immunoprotective and lymphatic functions

maturation of B lymphocytes and the production of IgA

storage for useful bacteria present in the colon

What causes appendicitis and how?

fecoliths or obstructions like hypertrophy of lymphatic tissue

Obstruction prevents drainage of mucus. → mucus fills lumen → limited expansion→ increased intraluminal pressure

Amplified by appendiceal microbiota (toxins).

Distension stimulates visceral afferent fibers → diffuse dull pain

signs and symptoms of appendicitis 

Acute abdominal pain starting in the mid-abdomen and later localising to the right lower quadrant.

Fever (low-grade), anorexia, nausea, vomiting, and elevation of the neutrophil count.

Diarrhoea / constipation

Reduced bowel sounds = sign of perforated appendix

What can appendicitis lead to and what are the symptoms?

Peritonitis/sepsis

• Signs of infection increase

• diffuse pain

• Rigidity/guarding

How do you diagnose appendicitis?

Physical exam

Rebound tenderness - (when you let go it hurts worse than when you press down)

Psoas sign (passive extension of the right hip causes pain) / Obturator sign (passive internal rotation of the flexed right hip causes pain)

Rovsings sign (press on LLQ and they feel rebound pain in the RLQ when pressure is released)

Bloods – WBC/CRP

CT/ ultrasound 

What landmark do you need to find to check for appendicitis?

Mcburneys point

one-third of the way from the right anterior superior iliac spine to the navel (umbillicus)

What are Diverticula?

Diverticula - sac-like protrusions/ pouches of mucosa through the muscular wall of the colon

Occurs where vasa recta penetrate the bowel wall

Diverticulosis vs diverticulitis

Diverticulosis - presence of diverticula

Diverticulitis - inflammation of a diverticulum

Risk factor of diverticular disease

• Increased risk with age

• Increased risk in men <50yrs, and women >50yrs

• Dietary risk factors: low dietary fibre, high salt, meat, and sugar intake

• Obesity (BMI >30)

• Smoking.

• Medications – Corticosteroids/NSAIDs

• Immunosuppression

What is complicated diverticulitis?

diverticulitis with abscess, perforation, stricture, obstruction, and/or fistula

Causes of diverticular formation

unknown

thought to occur due to abnormal colonic motility ↑ intraluminal pressure

Symptoms of diverticular disease

• Intermittent pain

• Change in bowel habit

• Painless bleeding

Symptoms of acute diverticulitis

• Acute abdominal pain

• Localised abdominal tenderness (site of inflammation)

• Signs of infection (fever, ↑ WBC)

complications of diverticular disease

Bleeding can lead to substantial blood loss

Stricture/Bowel obstruction

→ Signs: colicky abdominal pain, absolute constipation (passage of no flatus or stool), vomiting or abdominal distention

Perforation and peritonitis/sepsis

fistulae

Abscess

→ Signs: abdominal mass on examination / peri-rectal fullness on D

Diagnosis of diverticular disease

Abdominal examination:
– Tenderness on palpation
– Abdominal mass
– Guarding

 Pelvic examination – women

Full blood count, CRP, faecal occult blood test, urinalysis

Imaging/endoscopy – confirm and exclude

Treatment if diverticular disease

Depends on severity

diet change, liquid diet, antibiotics, surgery

What is the function of the rectum and at what vertebral level does it start?

Function: temporary storage of faeces and control of faecal excretion

the Rectal ampulla relaxes to accumulate and temporarily store faeces

begins at level of S3

Name the flexures in the rectum

anteroposterior flexures:

• Sacral flexure: follows the natural concavity of the sacrum

• Anorectal flexure: puborectalis muscle pulling rectum anteriorly (important for faecal continence)

lateral:

• superior

• intermediate

• inferior 

When does the rectum become the anal canal?

As rectum passes through hiatus in levator ani it transitions to anal canal

Where are the valves in the rectum?

Superior rectal valve - upper convexity on the left side of the rectum

Middle rectal valve - intermediate convexity on the right side

Inferior rectal valve - lower convexity on the left side of the intestine

** help reduce direct pressure on anal canal

What part of the rectum in retro/intra peritoneal

proximal 1/3 intraperitoneal (but only covers anterior and lateral surface)

Middle 1/3 predominantly retroperitoneal (only anterior surface covered).

distal 1/3 sub-peritoneal (below pelvic diaphragm)

rectouterine pouch = pouch of Douglas

What is the anal sphincter complex made up of?

Internal anal sphincter (IAS) → tonically contracted at rest (autonomic control)

Conjoint longitudinal muscle layer

External anal sphincter (EAS) → tonically contracted at rest (conscious control)

Where are faeces held in the anal canal

held around pectinate line by EAS (and small contribution from IAS)

Where is the pectinate/ dentate line and how is the anal canal different below and above it?

Junction of hindgut and proctodaeum (ectoderm)

Above the pectinate line
• ANS innervation
• Columnar epithelium

Below the pectinate line
• Somatic innervation
• Stratified squamous epithelia

Function of Anal cushions/Hemorrhoidal plexus

maintaining fecal continence by engorging with blood and closing the anal canal and by protecting the anal sphincter during defecation

Blood supply to the rectum

Superior rectal artery – terminal continuation of the inferior mesenteric artery.

Middle rectal artery – branch of the internal iliac artery.

Inferior rectal artery – branch of the internal pudendal artery

Venous drainage of the rectum

superior rectal vein → empties into the portal venous system

middle and inferior rectal veins → empty into the systemic venous system The superior rectal vein empties into the portal venous system,

Anastomoses between the portal and systemic veins are located in the wall of anal canal, making this a site of portocaval anastomosis

Nerve supply to the rectum

Sympathetic nerves: lumbar splanchnic nerves, superior and inferior hypogastric plexuses

Parasympathetic nerves: from S2-4 via the pelvic splanchnic nerves and inferior hypogastric plexuses

External anal sphincter: Somatic innervation –inferior rectal nerve (branch of pudendal nerve)

Lymphatic drainage of the rectum

Proximal 2/3: pararectal lymph nodes → drain into the inferior mesenteric nodes.

Distal 1/3: drains directly into the internal iliac lymph nodes

Process of defecation

stimulus: distension in rectum 

response: 

• contraction in rectum and sigmoid colon

• relaxation of internal anal sphincter

• contraction of external anal sphincter

then:

• relaxation of external anal sphincter

• relaxation of puborectalis muscle

• peristalsis + Valsalva manoeuvre (increased abdominal pressure)

What is diarrhoea?

↑ in stool frequency, liquidity, or volume.

WHO - three or more loose or liquid stools per day (or more frequent passage than is normal for the individual)

Properties of osmotic diarrhoea

Excess osmotically active particles in the gut lumen.

Variable volume, watery or loose consistency.

Osmotic gap >100mOsm/kg

Stops when the patient is fasted

underlying cause of osmotic diarrhoea

Osmotic laxatives (lactulose)

Excessive solutes within the lumen (e.g. lactose intolerance)

Inflammation within the mucosa (e.g. IBD, coeliac disease).

Motility disorders (e.g. IBS)

properties of secretory diarrhoea

Bowel mucosa secretes excess ions (chloride) into the lumen – water follows

Large volume, watery stool

Osmotic gap <100mOsm/kg

Continues when the patient is fasted

Underlying causes of secretory diarrhoea

Infections (cholera, E.coli, rotavirus)

Specific electrolyte transport defects (e.g. congenital chloride-losing diarrhoea

Management of diarrhoea

Determine the onset, duration, frequency, and severity of symptoms.

Enquire about the presence of red flag symptoms (e.g. blood in stool, weight loss)

fix dehydration 

What is constipation?

unsatisfactory defecation characterized by infrequent stools, difficult stool passage or both

Risk factors of constipation

More common in elderly

More common in women (very common in pregnancy)

relatively common in children <5y

Dehydration/low fibre intake ↑ risk

Physical activity ↓ risk of constipation

Causes of constipation

Management of constipation

Lifestyle advice:

• healthy, balanced diet (increased sorbitol, fruit and veg intake)

• Ensure adequate fluid intake

Ascertain/Exclude other causes

Laxatives if above fails – bulk forming first, followed by osmotic, gradually reduce once symptoms subside

Bristol stool chart

What is a common cause or rectal bleeding and why?

Haemorrhoids

Caused by loss of connective tissue support

** pregnancy only risk factor

internal vs external haemorrhoids 

internal haemorrhoids (most common):

• Above dentate line (relatively painless)

• Enlarge and prolapse through anal canal (Graded by degree of prolapse (i-iv))

• Haematochezia (bright red blood)/pruritis ani

• Can lead to “leakage”

External haemorrhoids

• Below dentate line (very painful)

• Less likely to bleed

• More likely to thrombose.

What is an anal fissure and why does it happen?

Tear or ulcer in the lining of the anal canal which causes pain on defecation

Linked to local trauma (e.g. passing of hard stool).

Underlying causation
– High internal anal sphincter tone
– Reduced blood flow to anal mucosa

Causes of Haematochezia

• Diverticular disease

• Haemorrhoids

• Anal fissure

• IBD

• Colorectal cancer

What is Melaena and what is it a sign of?

Passage of black, tarry stools (haemoglobin digested into haematin)

associated with upper GI bleed, Peptic ulcer disease, Variceal bleeds (oesophagus),Upper GI malignancy (e.g. Oesophageal/gastric cancer)