Intestinal Obstruction Flashcards
What is the epidemiology of bowel obstruction?
Small intestinal = significantly more common than large intestinal obstruction
What are the risk factors/causes of small bowel obstruction?
Adhesions
- 75% of SBO, mostly from prior abdo surgery
- Fibrous strands that form between tissues and organs
Strangulated hernia
- Most commonly femoral; inguinal = less common
Malignancy
- Often tumour of the caecum - obstruction of the ileo-caecal valve and thus the small intestine
- Other SB malignancy = rare
Volvulus - caecal
- Often elderly, with floppy/redundant mesentery
Crohn’s:
- Chronic inflammation can lead to fibrosis and subsequent obstruction
Gallstone ileus:
- Large gallstone passed into gut and blocks it
Bezoars:
- Medication bezoars = tablets/semi-liquid masses of medications, often following overdose of sustained release medications
- trichobezoars = ball of swallowed hair
Body packers:
- Packet of illicit drugs swallowed in a condom gets lodged
What are the risk factors for large bowel obstruction?
Most commonly due to colorectal malignancy
- Patients are often >70yrs
- Tumours are often advanced, metastatic disease is likely
- Perforation can occur
The risk of obstruction is more likely the further down the bowl
- As the contents become more solid
Sigmoid volvulus
- 5% of LBO
- Usually seen in the elderly and those with psychiatric illness and neurological disease (Alzheimer’s, PD, MS, quadriplegia)
- Most common cause of obstruction in Africa and Asia
What is paralytic ileus?
Describes a condition in which the bowel ceases to function and there is an absence of peristalsis
- Due to disordered neuromuscular transmission in the myenteric plexus
Often occurs after abdominal surgery
- Due to bowel handling
- Different part of the bowel take different times to ‘wake up’ e.g. small bowel <24hrs; large bowel 24-48hrs
Can also be due to:
- Intra-abdominal infection
- Metabolic disorders
What is the pathophysiology of BO?
Dilation of proximal bowel:
- Increased secretions + air leads to distension, decreased absorption, mucosal wall oedema, compression of vessels, ischaemia
Collapse of distal bowel:
- Impairment of normal secretory and digestive functions of the bowel
Types:
- Simple = one point of obstruction, no vascular compromise
- Closed loop = obstruction at two points forming a distended loop of bowl that is at risk of perforation
- Strangulated = blood supply to obstructed region becomes impaired (venous before arterial) leading to ischaemia and gangrene; perforation is more common
What is a pseudo-obstruction? How does it present?
When there is an autonomic imbalance resulting in sympathetic overactivity of a specific part of the colon
Can be acute or chronic:
- Acute colonic pseudo-obstruction = Ogilvie’s syndrome
Primary or secondary:
- Primary = direct injury to smooth muscle or nervous system (e.g. surgery/trauma)
- Secondary = Parkinson’s, Hirschprungs, endocrine disorders, medications etc
Patients are often elderly with multiple morbidities
Presents like LBO but other medical Hx may indicate true nature
How does SBO present?
Pain:
- Colicky abdo pain
- Often felt around umbilicus; higher compared to LBO
- If ileus - may be little/no pain
Distension:
- Increases as time elapses
- Less than LBO
Vomiting:
- Often provides some pain relief
- Presents sooner compared to LBO
Constipation:
- Obstipation/complete constipation (no stool or flatus) = a late sign
Oliguria:
- A late sign
Tinkling bowel sounds on auscultation
- Absent in ileus = a key distinction
Dilated loops of bowel palpable
Strangulation/perforation:
- Peritonism
Sepsis, shock (late)
How does LBO present?
Pain:
- Again colicky, lower than SBO
Distension:
- More significant the lower the level of the obstruction
Vomiting:
- May occur later
- Faeculant vomiting = vomiting faeces (in various stages of digestion) - a late sign of a lower obstruction
Constipation:
- Obstipation = earlier sign in LBO
- Rectum usually empty
Oliguria:
- A late sign
Tinkling bowel sounds on auscultation
Dilated loops of bowel palpable
Strangulation/perforation:
- Peritonism
Sepsis, shock (late)
How do you investigate obstruction?
Fluid chart + catheter:
- To monitor input/output
Bloods:
- FBC - aneamia in caecal carcinoma
- U+E
- Creatinine, Xmatch + group and save
- Glucose - slightly elevated by stress but very high levels might be a cause for concern
- Amylase - often raised, but not as high as pancreatitis
Plain AXR:
- Supine and erect films
- Water soluble contrast enema may also be helpful
CT:
- Non-contrast
- If peritoneal fluid level evident then 3x more likely to require surgery than those without
USS and MRI:
- Also possibly useful but variable availability or sensitivity
What are the findings of an AXR in obstruction?
Multiple fluid levels + bowel distension = abnormal
SBO/proximal colon:
- Ladder-like series of small bowel loops
- Fluid levels in upright views
- Distension; but may be absent if obstruction above upper jejunum
LBO:
- Distension much more marked
Paralytic ileus:
- Fluid levels
- SBO distension
Volvulus:
- ‘Coffee bean’ sign - classically associated with sigmoid volvulus, but just check which side its coming from
- Haustra (lines not crossing whole bowel) - become absent in LBO due to dilatation
- Valvulae conniventes/plique circularis (lines crossing whole bowel) - only present in lower duodenum + jejunum, and tend to remain defined in obstruction
Perforation:
- Gas under the diaphragm on an erect AXR
How do you manage BO?
Conservative management:
- If incomplete obstruction, previous surgery suggesting adhesions, advanced malignancy or pseudo-obstruction
Nil by mouth = bowel rest
Fluids:
- IV resus often required
- Electrolyte imbalance correction
- Urine output will be the best indicator of hydration
Analgesia - IV
Abx - IV
NG tube:
- Aspiration of contents + decompression
Endoscopy:
- For bowel decompression, dilatation of strictures, placement of self-expanding stents as final treatment or delaying until surgery
Surgery:
- Indications = strangulation/ischaemia, closed loop obstruction, perforation, peritonitis, cancer (if fit enough, otherwise stenting)
- Laparotomy +/- stoma
What other specific treatment might be used in pseudo-obstruction?
Neostigmine
- May aid in recovery
But correction of electrolyte imbalances are the most important as this might resolve the underlying pathology
