JC60 (Surgery) - Intestinal Obstruction Flashcards
Difference in presentation between small bowel and large bowel obstruction*
□ Small bowel obstruction (SBO):
→ High: early, profuse vomiting with rapid dehydration and minimal distension
→ Low: predominant pain with central distension, colics
□ Large bowel obstruction (LBO): early, pronounced distension with mild pain and minimal vomiting
Differentiate simple, closed loop and strangulated obstructions *
□ Simple: one obstructive point w/o vascular compromise
□ Strangulated: viability of bowel is threatened due to compromised blood supply
□ Closed loop: ≥2 obstructive points
Define causes of dynamic/ mechanical intestinal obstruction *
Intraluminal
Stool impaction in bed-ridden patients
Gallstone ileus
Trycho- (hairs) and phytobezoars (vegetable)
Foreign bodies
Intramural
Inflammatory strictures, eg. Crohn’s, radiation, ischaemic, anastomotic, drug-induced, endometriotic
Tumours and malignant strictures
Intussusception
Extramural
Adhesions
Incarcerated hernia
Volvulus
Diverticular disease
Other external compression, eg. LNs, peritoneal carcinomatosis, SMA syndrome
Define causes of adynamic/ functional intestinal obstruction (/)
Paralytic ileus (absent peristalsis)
- Post-operative
- Infectious, i.e. intra-abdominal sepsis
- Reflex ileus due to intra-abdominal inflammatory process
- Metabolic, eg. hypoK, uraemia commonest
Pseudo-obstruction (dysfunctional peristalsis)
- Small intestinal: idiopathic, familial visceral myopathy
- Acute colonic: toxic megacolon, Ogilvie syndrome
- (Chronic colonic:)
□ Degenerative, eg. MSA, DM
□ Paraneoplastic, eg. SCLC, carcinoids, thymoma
□ Autoimmune, eg. scleroderma, dermatomyositis, SLE
□ Infectious, eg. Chagas’ disease
□ Genetic, eg. mitochondrial ds
Explain the pathophysiology of proximal dilatation and distal collapse in intestinal obstruction
Distal collapse:
- Bowel exhibits normal peristalsis and absorption distal to obstruction, collapses after emptying contents
Proximal dilatation:
- Increased peristalsis and progressive dilatation, result in flaccidity and paralysis later
- Accumulation of bacteria overgrowth in gut, causing transmural spread and gas accumulation
- Fluid accumulation due to bowel wall edema and low absorption
Causes of bowel strangulation **
Complications of bowel strangulation
Features of strangulation
Causes:
→ External pressure, eg. hernia orifices, adhesions or bands
→ Interrupted mesenteric blood flow, eg. volvulus, intussusception
→ High intraluminal pressure esp in closed loop obstruction
Consequences:
→ Haemorrhagic infarction occurs in ischaemic segment
→ Peritonitis and septicaemia due to ↑permeability to luminal bacteria and toxins
→ Hypovolemic shock due to sequestration of blood if long-segment strangulation
Causes of closed loop bowel obstruction
Consequence of prolonged obstruction
Closed loop obstruction: ≥1 obstruction points
Causes:
→ Volvulus
→ Incarcerated hernia
→ Lower bowel obstruction + competent ileocaecal valve (occurs in 1/3)
Consequences: cannot decompress into prox. bowels
- High risk of strangulation + perforation
Causes of small bowel obstruction **
Intra-luminal
Intra-mural
Extra-mural
Intra-luminal:
- Foreign body
- Gallstones
- Bezoars
- Worms
Intra-mural
- Tumor
- Strictures: Crohn’s, radiation, anastomotic, drug
- Intussusception
Extra-mural
- Adhesions**
- Hernia
- Volvulus
- Intraperitoneal malignancy
Causes of large bowel obstruction **
CA colon (commonest, 50-60%)
Colonic diverticulitis
Caecal and sigmoid volvulus
External tumour compression: metastasis, pelvic/ extraperitoneal tumors
Strictures (ischaemic, anastomotic, radiation, endometriotic)
Faecal impaction
Causes of intestinal adhesions **
Pathogenesis
Complications
Causes:
→ Congenital adhesions
→ Post-inflammatory: following severe peritonitis (eg. appendicitis, cholecystitis, PID)
→ Post-operative: ↑risk if open surgery
Pathology:
peritoneal irritation → local fibrin production → early fibrinous adhesions
→ late vascularization and replacement by fibrous adhesions
Complications:
→ IO affecting lower SB
→ Chronic abdominal/pelvic pain with dyspareunia
→ Infertility due to tubal blockage
Prevention of intestinal adhesions **
Prevention in surgery: commonest in appendicectomy and gynaecological procedures
→ Good surgical technique with gentle handling of bowel and laparoscopic surgery
→ Less contact with irritants, eg. removal of powder from gloves, ↓contact with gauze
→ Barriers to keep damaged peritoneal surfaces separated, eg. solid (sodium hyaluronate, oxidized cellulose), liquid (PEG, icodextrin, hyaluronate)
→ Saline lavage
Intestinal adhesion
Classical imaging sign
Management
CT: ‘fat-bridging’ sign showing cord-like mesenteric fat bridging across peritoneum
Mx of adhesive IO:
Supportive management: ‘drip and suck’
□ ABCs: resuscitation if unstable
□ Nil per oral until resolution
□ NG tube suction
□ IV fluid/electrolytes:
→ Secure large bore IV access
→ Give Ringer’s lactate/NS ± K+ supplements and correct acidosis
□ ± others: monitor UO, prophylactic broad-spectrum Abx, CVP monitoring for resuscitation
Adhesiolysis if refractory to conservative Tx or features of strangulation
Gallstone ileus
Pathogenesis
Imaging sign
Management options
Pathogenesis:
erosion of gallstone into bowel through cholecystoenteric fistula
→ gallstone (usu >2cm) impacts at small bowel → ‘ball-valve’ effect causing recurrent SBO attacks
Imaging sign: Rigler’s triad (pneumobilia, SB IO, obstructing gallstone)
Management: crush stone intraluminally → milk fragment into caecum to for removal
- Enterolithotomy
- ± cholecystectomy and closure of cholecystoenteric fistula
Intussusception **
Causes in children and adults
Pathogenesis
Major sites in GIT
S/S
Imaging signs
Management
Causes:
Children: 90% idiopathic but may be a/w previous URTI/GE (?due to hypertrophic Peyer patches)
Adults: ALWAYS a/w pathological lead-points (usu intraluminal lesions in SB), eg. polyp, submucosal lipoma, Meckel’s diverticulum, GIST, carcinoma
Pathology: occurs when proximal gut (intussusceptum) invaginates into distal segment (intussusceptiens)
Site: majority ileocolic (90%) in children vs colocolic in adults
S/S: classically IO with currant jelly stools
Intussusception **
Imaging sign
Management
CT: characteristic target (donut) lesions
Mx:
→ Children: hydrostatic or pneumatic pressure by enema
→ Adults: bowel resection to r/o CA
Volvulus **
Pathogenesis
3 main types
Pathology: twisting of a portion of bowel about its mesentery
→ >180o torsion → obstruction to lumen
→ >360o torsion → mesenteric vascular occlusion
Sigmoid volvulus (60%)
Caecal volvulus (30%)
Small bowel volvulus (rare)
Sigmoid volvulus /
Risk factors
Pathogenesis
S/S
→ RFs: Asians, elderly institutionalized pt with Hx of constipation or chronic psychotropic drug use
→ Pathology: narrow mesentery + long sigmoid colon with fecal loading → predispose to twisting of sigmoid colon
→ S/S: usu insidious onset of LBO Sx but may be fulminant (17%) in younger pt
Sigmoid volvulus **
Imaging signs
Management options
Ix:
Plain AXR shows coffee bean sign
Barium enema shows bird’s beak or ace-of-spade sign
(NOT done usually due to risk of perforation)
Mx:
- Sigmoidoscopic decompression by applying pressure at apex of volvulus (75-95% successful rate but 50% recurrence rate)
- Sigmoid resection/ sigmoidectomy with primary anastomosis or Hartmann’s procedure
Caecal volvulus /
Risk factors
S/S
Imaging signs
RFs: more common in middle-aged female with congenitally mobile caecum
S/S: classical IO Sx w/ midline/Lt-sided palpable tympanic swelling (25%) ± Sx of ischaemia
Dx: AXR (coffee bean caecum) and CT scan (‘whirl sign’)
Management of caecal volvulus **
Mx: surgical detorsion + caecopexy ± caecostomy (if unstable)
ileocecal resection/R hemicolectomy with 1o anastomosis (if stable
Small bowel volvulus /
Pathogenesis
Risk factors
Section of bowel invovled
Most caused by adhesions to abdominal wall and female pelvic organs
RFs:
- malrotation of gut (both DJ junction and ileocaecal valve at RUQ → short mesenteric attachment),
- Meckel’s diverticulum (fibrous band as axis)
Pathology: usu involve midgut (D2 to transverse) and rotate about SMA as axis
Cardinal features of IO
(1) Colicky abdominal pain
(2) Abdominal distension
(3) Nausea/vomiting
(4) Constipation/obstipation
(5) Increased bowel sounds
Describe onset, character and site of abdominal pain in IO
□ Onset: usually sudden and severe
□ Nature: initially colicky (initial hyperperistalsis) and gradually becomes a mild and more constant diffuse pain (distension with hypoperistalsis)
□ Site: periumbilical (SBO) or lower abdomen (LBO), usu poorly localized
Difference in abdominal distention between small vs large bowel obstruction
□ SBO: usu at centre of abdomen, ↑ for distal obstruction ± visible peristalsis (‘ladder-like’)
□ LBO: usually a late feature, RLQ hyperresonant bulge if closed loop
Differentiate content of vomitus in different types of intestinal obstruction
Vomitus: digested food (GOO) vs bilious (high SB) vs feculent (low SB) vs none (LB)
Associated Signs of IO (apart from 4 cardinal features) **
Bowel sounds: initially hyperactive (high-pitched tingling if SBO), later absent
Dehydration: usu in SBO due to ↑↑vomiting and fluid sequestration
Pyrexia: rare and may indicate ischaemia, perforation or underlying inflammation/abscess
Tenderness: indicates impending/established ischaemia
Peritoneal signs: indicates impending/overt infarction or perforation
Clinical features of bowel strangulation
how is it different from normal, uncomplicated IO?
- Constant, severe pain (cf colicky abdominal pain)
- Tenderness: severe (cf no/mild)
- Peritoneal signs: guarding, rigidity
- Blood in vomitus
- Fever and shock
Outline history taking for IO
□ Cardinal features: pain, vomiting, abd distension, constipation/obstipation
□ Features of strangulation: constant, severe pain with peritoneal signs and shock
□ Other associating symptoms suggestive of underlying aetiology
□ Previous Hx of IO
□ Past abdominal Hx:
→ abd/pelvic surgery for adhesive IO
→ severe abd inflammation for adhesive IO
→ CA or abd/pelvic irradiation
□ RFs for underlying aetiology:
→ RFs for ischaemic bowel: atherosclerotic RFs, CVD, stroke
→ RFs for malignancy: LOW, LOA, prev CA, FHx
Outline P/E for suspected IO
□ General:
→ Vitals and features of dehydration for haemodynamic instability
→ LNs for malignant obstruction
□ Abdomen:
→ Inspection: distension, scars (prev surgery), visible peristalsis
→ Palpation: peritoneal signs, masses, hernia (must be checked esp femoral, easily strangulated)
→ Auscultation: BS, succession splash (GOO)
→ DRE: rectal masses, impacted stools
Surgical treatment options for uncomplicated IO**
Adhesion
Strictures
Hernia
Bolus/ Foriegn body
Intussusception
Uncomplicated IO:
- Operative decompression
- Bowel resection if non-viable bowels
Specific causes:
- Adhesiolysis (enterolysis) for adhesive IO
- Stricturoplasty for Astrictures
- Hernia repair for incarcerated hernia
- Bolus removal by breaking down, pushing to colon then removal with enterotomy
- Surgical reduction of intussusception
Monitoring methods for resolution of IO **
↓abdominal distension
↓ Nasogastric output
Passage of flatus and bowel movement
Resolution on AXR
Surgical treatment of large bowel obstruction **
Factors for surgery
Patient condition
IC valve competence
Heavy bacterial and fecal load
Edematous proximal colon
Poor patient condition - Cancer, Malnutrition
Compare mechanical SBO and paralytic ileus /
- Abdominal distention
- Bowel sounds
- Constipations
- Pain character
- Vomiting
- Peritoneal signs
- Fever
- AXR signs
Indications for urgent bowel surgery
