Special Surgery 24. Ileus: Types, Symptomatics, Diagnostics, Treatments

I. Definition, Types and Pathophysiology

Definition

Ileus = disturbed intestinal passage with accumulation of gas and fluid in the bowel
Can be functional/paralytic or mechanical obstruction
Clinical problem: dehydration + electrolyte loss + bowel distension + ischemia risk
Important exam distinction: paralytic ileus has no mechanical transition point; mechanical ileus has a physical blockage

Main Types

Paralytic ileus / adynamic ileus

Impairment of peristalsis without mechanical obstruction
Bowel is functionally silent
Usually diffuse small and large bowel dilatation
Air often reaches colon and rectum

Mechanical ileus / intestinal obstruction

Interruption of normal intestinal passage due to mechanical blockage
May be small bowel obstruction (SBO) or large bowel obstruction (LBO)
May be partial or complete
Proximal bowel dilates; distal bowel collapses

Strangulation ileus

Mechanical obstruction + compromised mesenteric blood supply
Obstruction → venous congestion → edema → arterial ischemia → necrosis → perforation
Surgical emergency
Common causes: incarcerated hernia, volvulus, closed-loop obstruction, intussusception, adhesive band

Closed-loop obstruction

Bowel obstructed at two points
Rapid distension between two obstruction points
High risk of strangulation, ischemia and perforation
Typical examples: volvulus, internal hernia, adhesive band loop

Pathophysiology

Obstruction/stasis → gas + fluid accumulation proximal to blockage
Distension → pain + vomiting + decreased venous return from bowel wall
Vomiting + third spacing → hypovolemia + electrolyte disturbance
Bowel wall edema → impaired perfusion → bacterial translocation
Ischemia → necrosis → perforation → peritonitis → sepsis

Small Bowel vs Large Bowel Obstruction

Feature	Small Bowel Obstruction	Large Bowel Obstruction
Common causes	Adhesions, hernia, Crohn stricture, tumor, gallstone ileus	Colon cancer, volvulus, diverticular stricture, fecal impaction
Pain	Early, colicky, central/periumbilical	Colicky, lower abdominal, often slower onset
Vomiting	Early, frequent; high obstruction can be bilious	Late; can become feculent
Distension	Variable; more marked in distal SBO	Usually marked
Constipation/obstipation	Later; absolute constipation in complete obstruction	Early and prominent
Surgical importance	Adhesive partial SBO can often be treated conservatively first if uncomplicated	Often needs urgent cause-specific intervention, especially complete LBO or cecal danger

II. Etiology and Clinical Features

Paralytic Ileus: Etiology

Postoperative ileus:

Most common after abdominal surgery
Due to surgical stress, bowel handling, inflammation, opioids and immobility
Usually self-limited after bowel manipulation

Electrolyte disturbances: especially hypokalemia; also hypomagnesemia
Intra-abdominal inflammation: peritonitis, pancreatitis, appendicitis, cholecystitis
Retroperitoneal trauma, hematoma or inflammation
Sepsis or severe systemic infection, including pneumonia
Neurological injury or spinal trauma
Untreated mechanical obstruction in late phase
Drugs:

Opioids
Anticholinergics
Calcium channel blockers
Tricyclic antidepressants, sedatives and other constipating drugs

Mechanical Ileus: Etiology

By Location of Obstruction

Intraluminal:

Foreign body
Gallstone ileus
Bezoar
Fecal impaction
Meconium ileus in neonates

Intramural:

Tumor
Inflammatory bowel disease, especially Crohn stricture
Diverticular stricture
Ischemic or radiation stricture
Intussusception

Extraluminal:

Adhesions: most common cause of SBO in adults
External hernia: inguinal, femoral, incisional, umbilical
Internal hernia
Volvulus
Extrinsic tumor compression
Abscess or inflammatory mass

By Common Clinical Cause

Small bowel obstruction:

Adhesions after previous abdominal surgery
Incarcerated hernia
Crohn disease stricture
Small bowel tumor or peritoneal carcinomatosis
Gallstone ileus

Large bowel obstruction:

Colon cancer: most important adult cause
Sigmoid volvulus
Cecal volvulus
Diverticular stricture
Fecal impaction

Clinical Features

Paralytic Ileus

Diffuse abdominal discomfort or mild diffuse pain
Abdominal distension
Nausea, vomiting
Constipation or inability to pass flatus
No colicky waves
Bowel sounds decreased or absent
Tympanic abdomen on percussion

Mechanical Ileus

Colicky, intermittent abdominal pain
Pain comes in waves → hyperperistalsis against obstruction
Nausea and vomiting
Constipation; obstipation in complete obstruction
Abdominal distension
Early: high-pitched metallic/tinkling bowel sounds
Late: absent bowel sounds if bowel becomes exhausted or ischemic

Strangulation / Ischemia Warning Signs

Continuous severe pain instead of intermittent colic
Localized tenderness, guarding or rebound tenderness
Fever, tachycardia, hypotension
Leukocytosis, high CRP
Metabolic acidosis or rising lactate
Peritonitis
Irreducible painful hernia
CT signs: closed loop, bowel wall hypoenhancement, pneumatosis, portal venous gas, free fluid, free air

Complications

Hypovolemia due to vomiting and third spacing
Electrolyte disorders:

Vomiting → hypochloremic metabolic alkalosis
Hypokalemia worsens ileus
Dehydration → prerenal acute kidney injury

Aspiration pneumonia
Bowel ischemia and necrosis
Perforation
Peritonitis
Sepsis and septic shock
Short bowel syndrome after extensive resection
Recurrence, especially after adhesive SBO

III. Diagnostics

Initial Assessment

Assess ABC, shock, sepsis and peritonitis first
History:

Previous abdominal surgery → adhesions
Known hernia
Cancer history
IBD, diverticular disease, radiation history
Medication history: opioids, anticholinergics, CCB
Last stool/flatus, vomiting character, pain pattern

Physical Examination

Inspection:

Abdominal distension
Surgical scars
Visible peristalsis in thin patients with mechanical obstruction

Auscultation:

Early mechanical obstruction: high-pitched metallic bowel sounds
Paralytic ileus or late ischemic obstruction: absent bowel sounds

Palpation:

Diffuse distension and tenderness
Localized tenderness suggests strangulation, ischemia or inflammatory cause
Guarding/rebound → peritonitis
Always examine hernia orifices

Percussion:

Tympanic abdomen due to gas-filled bowel

Digital rectal examination:

Rectal tumor, fecal impaction, blood
Empty rectum supports complete distal obstruction, but is not diagnostic alone

Laboratory Tests

CBC: leukocytosis, anemia
CRP, procalcitonin if sepsis/infection suspected
Electrolytes: Na+, K+, Cl-, Mg2+, Ca2+
Urea/creatinine: dehydration, AKI
Glucose
Liver tests, bilirubin, amylase/lipase if biliary/pancreatic cause possible
Blood gas + lactate if ischemia, shock or sepsis suspected
Coagulation group and type/screen if operation likely
Urinalysis and pregnancy test when relevant

Imaging

Plain Abdominal X-Ray

Fast initial test, but less accurate than CT
Mechanical SBO:

Dilated small bowel loops
Central loops with valvulae conniventes crossing full lumen
Multiple air-fluid levels
Step-ladder / ladder pattern
Collapsed distal bowel if complete obstruction

Large bowel obstruction:

Dilated colon proximal to obstruction
Peripheral colonic gas pattern
Cecal dilatation important: high perforation risk when very large

Paralytic ileus:

Diffuse small and large bowel dilatation
Gas usually present in rectum
No single transition point

Upright chest/abdominal X-ray can show free subdiaphragmatic air if perforation

CT Abdomen/Pelvis with IV Contrast

Most important imaging test when mechanical obstruction or complication is suspected
Shows level and degree of obstruction
Shows transition point
Identifies cause: adhesion pattern, hernia, tumor, volvulus, abscess, gallstone ileus
Assesses complete vs partial obstruction
Assesses complications:

Closed-loop obstruction
Bowel ischemia: poor wall enhancement, wall thickening, mesenteric edema
Free fluid
Pneumatosis intestinalis
Portal venous gas
Pneumoperitoneum

Water-Soluble Contrast Study

Useful mainly in adhesive partial small bowel obstruction without strangulation signs
Diagnostic and sometimes therapeutic
Contrast reaches colon within 24 h → high chance of non-operative resolution
No contrast in colon after 24 h → high risk of conservative failure
Do not delay operation if peritonitis, ischemia, closed loop or strangulation is suspected

Ultrasound / MRI / Endoscopy

Ultrasound:

Can show dilated loops, decreased/absent peristalsis, free fluid
Useful in children, pregnancy or limited-resource settings
Operator-dependent

MRI:

Alternative in pregnancy when CT radiation should be avoided

Colonoscopy/sigmoidoscopy:

Diagnostic and therapeutic in selected sigmoid volvulus
Stent placement in selected malignant left-sided colonic obstruction
Avoid if perforation or peritonitis is suspected

IV. Treatment

Immediate General Management

Hospital admission and surgical assessment
NPO / nil per os
Two IV lines; crystalloid fluid resuscitation
Correct electrolytes, especially K+ and Mg2+
Nasogastric tube decompression if vomiting, marked distension or SBO
Urinary catheter if severe dehydration, shock or major operation likely
Analgesia and antiemetics
Stop/reduce ileus-provoking drugs if possible: opioids, anticholinergics
Thromboprophylaxis unless contraindicated
Broad-spectrum antibiotics if strangulation, ischemia, perforation, peritonitis, fever/sepsis or operation is planned

Paralytic Ileus Treatment

Treat underlying cause
Supportive therapy:

NPO initially if vomiting or severe distension
IV fluids
Electrolyte correction
NG tube only if persistent vomiting or severe distension
Early mobilization
Reduce opioids; use multimodal analgesia
Chewing gum can stimulate gut motility after surgery

Usually resolves spontaneously within days if cause is corrected
Postoperative ileus lasting too long or worsening → exclude mechanical obstruction, leak, abscess, peritonitis
Parenteral nutrition only if prolonged ileus and enteral intake is not possible for several days

Mechanical Small Bowel Obstruction Treatment

Conservative / Non-Operative Treatment

Indicated mainly for partial adhesive SBO without ischemia, strangulation or peritonitis
Components:

NPO
IV fluids and electrolyte correction
NG decompression if vomiting/distension
Clinical observation: pain, pulse, fever, tenderness, urine output
Repeated labs: WBC, CRP, lactate, renal function, electrolytes
Water-soluble contrast protocol in selected adhesive SBO

Failure signs:

Increasing pain or tenderness
Persistent complete obstruction
No contrast reaching colon after 24 h in contrast protocol
Worsening leukocytosis, lactate, acidosis or sepsis
No clinical improvement after 48-72 h depending on local protocol and patient status

Indications for Urgent Operation

Peritonitis
Strangulation or bowel ischemia suspected
Closed-loop obstruction
Pneumoperitoneum / perforation
Incarcerated or strangulated hernia
Complete obstruction, especially if no improvement
Hemodynamic instability or septic shock
Failure of conservative treatment

Operation Principles

Approach: laparoscopy in selected stable simple adhesive obstruction; laparotomy if severe distension, ischemia, peritonitis, unclear anatomy or complex obstruction
Release obstruction:

Adhesiolysis
Hernia reduction and repair
Detorsion if volvulus and bowel viable
Removal of foreign body/gallstone when indicated

Assess bowel viability:

Color, peristalsis, mesenteric pulsation, bleeding from cut edge
Resect necrotic or perforated bowel
Anastomosis vs stoma depends on contamination, perfusion, stability and patient risk

Large Bowel Obstruction Treatment

Often needs urgent cause-specific management
Colon cancer obstruction:

Right-sided: right hemicolectomy if fit and resectable
Left-sided: resection, Hartmann procedure, primary anastomosis +/- diverting stoma, or bridge-to-surgery stent in selected stable patients
Palliative stent or diverting stoma if unresectable/metastatic or high-risk

Sigmoid volvulus:

No peritonitis/ischemia: endoscopic detorsion + rectal tube
Definitive sigmoid resection usually needed because recurrence is common
Peritonitis, ischemia, perforation or failed detorsion → emergency surgery

Cecal volvulus:

Usually surgical treatment: right hemicolectomy or cecopexy in selected viable bowel

Fecal impaction:

Enema, manual disimpaction, laxative regimen after exclusion of perforation/ischemia

Exam-Focused Treatment Algorithm

Suspect ileus/obstruction from pain + vomiting + distension + constipation/obstipation
Assess danger signs: peritonitis, shock, fever, continuous pain, hernia, high lactate
Start NPO + IV fluids + electrolyte correction +/- NG tube
CT abdomen/pelvis with IV contrast if mechanical obstruction or complication possible
If paralytic ileus: treat cause, mobilize, reduce opioids, observe
If partial adhesive SBO without danger signs: conservative treatment +/- water-soluble contrast
If complete obstruction, large bowel obstruction, strangulation, peritonitis, perforation or conservative failure: operation/source control