- Q. What are the 3 main types of intestinal obstruction? Give an example of each
A. Intraluminal Obstruction
a. Tumour of the bowel (carcinoma, lymphoma)
b. Diaphragm disease: limits diameter of small bowel, caused by NSAIDS (fibrosis)
c. Meconium ileum
d. Gall stone ileus (inflamed gall bladder pushes on bowel, stone passes from gall bladder into small bowel and blocks it)
B. Intramural Obstruction
a. Inflammatory: Crohn’s (small bowel), diverticulitis (outpouching in sigmoid colon, faecal peritonitis can occur, low fibre diet)
b. Tumours
c. Neural: Hirschsprung’s disease (no dilation of colon in rectum – poor faecal movement – can lead to enterocolitis, presentation at birth)
C. Extra luminal Obstruction
a. Adhesions: between loops of bowel, often due to prev surgery (silica gloves), leads to fibrous adhesions – scar tissue
b. Volvulus: sigmoid colon, long mesentery can twist causing obstruction and occasionally tissue necrosis
c. Tumour: peritoneal deposits, often related to final stages of metastatic cancer
- Q. What comprise the embryological foregut, midgut and hindgut? Describe the nerve and blood supply of each.
a. Foregut = oesophagus, 2/3 duodenum, liver, gall bladder, pancreas, spleen
i. Blood supply: coeliac trunk
ii. Nerve supply: greater splanchnic nerve which arises from T5-T9, pain is usually felt anteriorly in the midline at this level i.e epigastrium
b. Midgut = 1/3 duodenum, jejunum, ileum, caecum, appendix, ascending colon, 2/3 transverse
i. Blood supply: superior mesenteric artery
ii. Nerve supply: lesser splanchnic nerve (T10 and T11) – referred to the periumbilical area
c. Hind gut = 1/3 transverse, rectum, upper anal canal
i. Blood supply: inferior mesenteric artery
ii. Nerve supply: lowest splanchnic nerve, T12 – referred to suprapubic area
- Q. Which parts of the GI tract are retroperitoneal?
A. Retroperitoneal organs are organs that are only covered by peritoneum on their anterior side (retro are more firmly attached than mesentery)
B. SAD PUCKER = suprarenal glands, aorta, duodenum last 2/3, pancreas, urethra, colon, kidney, (o)oesophagus, rectum
- Q. What is a volvus, where does this usually occur in the bowel?
A. A twist/rotation of a segment of the bowel – often occurs in sigmoid colon (then caecum)
a. A 360° twist -a closed loop obstruction is produced.
b. Fluid and electrolyte shifts into the closed loo
c. Increase in pressure and tension - impaired colonic blood flow
d. Ischaemia, necrosis, and perforation of the loop of bowel
- Q. What mechanisms of intestinal obstruction can occur?
A. Volvus: twisting – usually sigmoid
B. Adhesions: when abdominal structures stick to each other, (bowel loops of omentum, other solid organs, abdo wall)
C. Intussusception: telescoping one hollow structure into its distal hollow structure (small bowel into large bowel)
D. Atresia: absence of opening or failing of development of hollow structure
- Q. What occurs due to small bowel obstruction (pathophysiology and symptoms)?
A. Dilation - Increased secretions and swallowed air
B. More dilation – decreased absorption – mucosal wall oedema
C. Increased pressure – compression of intramural vessels
D. Ischaemia – perforation
E. Symptoms: anorexia, nausea, vomiting/distension with pain, fluid and electrolyte imbalance, hypovolemia, bacterial overgrowth faeculent vomiting
- Q. What occurs due to large bowel obstruction (pathophysiology and symptoms)?
A. Colon proximal to obstruction dilates, leads to increased pressure and decreased mesenteric blood flow
B. Mucosal oedema – transudation of fluid and electrolytes
C. Arterial blood supply is comprised – mucosal ulceration – full thickness necrosis – perforation – bacteria translocation – Sepsis
- Q. What can occur due to colonic volvulus?
A. Axial rotation at mesenteric attachments – 360 degree twist = closed lope obstruction
B. Fluid and electrolyte shifts into the closed loop: increase in pressure and tension: impaired colonic blood flow
C. Ischaemia, necrosis and perforation of loop in the bowel
- Q. Who is at a higher risk of small bowel obstruction?
o Adults – Adhesions (developed world)- previous surgery – Hernia ( developing world) – Crohns – Malignancy
o Children – Appendicitis – Intesussuption – Volvulus – Atresia – Hypertrophic pyloric stenosis
o Uncommon Causes – Radiation – Gall stones – Diverticulitis, appendicitis – Sealed small perforation, intra abdominal collection / abscess – Foreign Bodies ( Bezoars)
- Q. Who is at a higher risk of large bowel obstruction?
A. 90% colorectal maliganancy, (30% of colorectal malignanys present as LBO), » 5% Volvulus » 3% strictures Ischaemic, radiation, inflammatory, gynaecological other malignancy » 2% rare causes –FB, hernia, abscess » Functional obstruction - faecal impaction
B. Paeds: anatomical development, imperforate anus, hirshsprung’s disease
- Q. What is a hernia? How does it present? Describe four types of hernia – who do they most commonly affect?
A. An abnormal protrusion of viscus through normal or abnormal defects of body cavity
B. Presents as lump(appears and disappears), pain, discomfort
C. Inguinal hernia: mostly men, age-related
D. Femoral hernia: less common than inguinal, women
E. Umbilical hernia: young children
F. Incisional hernia: occurs when tissue protrudes through a surgical scar that is weak
- Q. Describe the anatomical location of the deep inguinal ring and the superficial inguinal ring
A. Deep inguinal ring: just above midpoint of the inguinal ligament
B. Superficial inguinal ring: just above and medial to pubic tubercle
- Q. Name two types of inguinal hernia
A. Direct: caused by weakness in posterior wall of the inguinal canal
a. Contents move through defect in posterior wall along the inguinal canal and through to superficial ring
B. Indirect: abdominal contents pass through deep inguinal ring, through inguinal canal and exit via superficial ring – more common
C. Both types exit superficial ring and emerge within the testes
D. Causes: increased intra-abdominal pressure, weakness of abdominal muscles - chronic cough, constipation, heavy lifting, advanced age, obesity
E. Present (GP): painless swelling in groin, often asymptomatic, lump may come and go, pain, change in bowel habit, constipation, burning sensation in groin, scrotal swelling (males)
- Q. Where are femoral hernias located? What are they prone to?
A. Comes through femoral canal below inguinal ligament
B. Appears below and lateral to pubic tubercle
C. Prone to incarceration and strangulation
- Q. How do umbilical hernias occur?
A. Occurs when tissue protrudes around the umbilicus: common in very young children, in most cases under 6m resolution will occur as the child grows older.
B. Risk factors in adulthood: obesity, heavy lifting, persistent coughing, multiple pregnancies
- Q. What is an incisional hernia?
A. This occurs when tissue protrudes through a surgical scar that is weak
B. Complication of abdominal surgery
C. Risk factors: emergency surgery, would infection post op, persistant coughing, poor nutrition, heavy lifting, having another pre-existing health condition (e.g. diabetes, HIV/AIDS – slows down healing)
- Q. What is absolute constipation?
A. Obstipation: failure to pass stools or gas
- Q. How may acute/chronic large bowel obstruction present?
A. Acute: av 5/7, abdo distension and discomfort, pain and vomiting later
B. Chronic: progressive change in bowel habits
C. General S&S: adbo discomfort, fullness/bloating/nausea, altered bowel habit (difficulties opening bowels, blood in stools, constipation – obstipation), abdo pain (colicky), late vomiting, weight loss, (Volvulus: sudden pain, localised tenderness and distension)
- Q. Describe clinical examination of LBO
A. Abdominal distension – Resonance? – Tenderness? – diffuse; RIF – bowel sounds normal –increased- quiet later
B. Palpable mass – Hernia, caecum, distended bowel loop – Inflammatory mass omentum & bowel (phlegmon)
C. Rigidity, peritonitis late sign
D. Digital rectal examination
a. Empty rectum, Hard stools, Blood
E. Proctoscopy / Sigmoidoscopy
- How may SBO present? - small bowel obstruction
A. Vomiting (projectile? May indicate location – faeculent), pain (colicky progress to constant – diffuse), constipation (late (one more motion after onset of pain not uncommon), Obstipation – absence of faeces or flatus, distension, tenderness, nausea/anorexia, distension
Q. Describe the clinical findings of SBO
- small bowel obstruction
A. Difficult to distinguish on clinical examination – Simple, incomplete, early strangulated obstruction
B. Vital signs
a. Tachycardia –response to pain- altered Heamodynamic status
b. Hypotension altered fluid status
c. Temperature –on going systemic inflammation, ischemia, perforation
C. Tenderness
a. Localised – maximal –over the site of distension or impending perforation
b. Diffuse - perforation
D. Swelling
a. Discrete lump – abdominal wall – hernia
b. Diffuse – common
E. Resonance
a. Tympanic – gas filled
b. Dull - fluid
F. Bowel sounds
a. Increased early
b. Absent late
- Q. Describe the management of SBO
A. All cases – Aggressive fluid resuscitation, – bowel decompression – Analgesia and antiemetic – early surgical consultation – Antibiotics
B. Non operative
a. Adhesive obstruction » If no peritonitis » Atleast 72 h (60 to 85% resolve)
b. Inflammatory obstruction / active Crohns disease / diverticulitis
c. Intra abdominal abscess (drainage radiological)
d. Radiation enteritis
e. Metastatic malignancy
f. Acute post operative obstruction – paralytic ileus
- Q. What is the ileocecal valve, what does it do? How does this determine mechanism in large bowel obstruction?
o The ileocecal valve is a sphincter between the small and large bowel, limits movement of large colon contents back into small intestine
o In large bowel obstruction dilation occurs:
o If ileocaecal valve competent (gas and fluid can flow back through) – The caecum - usual site of perforation
o If ileocaecal valve incompetent – faeculent vomiting
- Q. Where are colorectal tumours most likely to occur? What could occur due to perforation at the point of obstruction?
A. Large bowel – distal to transverse colon
B. Flexure: least common
C. Tumours of left side = obstructive symptoms
D. Perforation = local tumour invasion, inflammatory reaction
