Intestinal Obstruction (Ileus): Causes

Pathogenesis (development of disease)

In mechanical ileus, there are several causes of obstruction (closure):

  • Extraluminal: lumen obstruction/compression from the outside (postoperative adhesions (adhesions), bride/scar strand in the abdominal cavity; hernia/intestinal hernia).
  • Intraluminal: lumen obstruction (foreign bodies (bezoars), gallstones, coprostasis/fecal impaction, meconium (infantile saliva), intussusception/invagination of a segment of the intestine, tumors)
  • Intramural: change in the intestinal wall (inflammation, gastrointestinal stromal tumors, GIST).

A distinction is made between the type of mechanical obstruction:

  • Incarceration (pinching of tissue).
  • Invagination (invagination of a section of intestine).
  • Strangulation (strangulation of the intestine)
  • Volvulus (twisting of the intestine)
  • foreign body-induced stenosis (narrowing; e.g. gallstone).
  • Tumor stenosis (tumor-related narrowing).

Mechanical obstruction may result in restricted (subileus or incomplete ileus) or abolished (complete ileus) food passage. 70-80% of all ilei are found in the small intestine and 20-30% in the colon (large intestine; here usually a malignancy/malignant tumor (70% of cases)). The stoppage of the intestinal passage leads to a stretching of the intestinal wall, which in turn leads to a reduction in blood flow. This in turn leads to functional impairment. In addition, penetration of intestinal bacteria into the intestinal wall occurs, leading to bacteremia or toxicemia (blood poisoning caused by bacterial toxins). Furthermore, a state of shock with hypovolemia (decrease in circulating blood volume) develops due to edema (“swelling” or “water retention”) affecting the intestinal wall and fluid leakage into the intestine. If left untreated, systemic inflammatory response syndrome (SIRS) progresses to full-blown septic shock with consecutive multiorgan failure (MOV; MODS or MOF).

Etiology (Causes)

Disease-related causes.

Liver, gallbladder, and bile ducts – Pancreas (pancreas) (K70-K77; K80-K87).

  • Cholelithiasis (gallstones) → intraenteric gallstone ileus.

Mouth, esophagus (esophagus), stomach, and intestines (K00-K67; K90-K93).

  • Bezoar (hairball)
  • Bridenileus – intestinal obstruction due to adhesions (adhesions).
  • Intestinal stenosis/constriction (here: colon stenosis/constriction of the large intestine) – due to:
    • Neoplasms (neoplasms): colonic and rectal stenosis/constriction of colon and rectum by malignancy (malignant tumor): 70% of cases).
    • CED stenosis (narrowing due to chronic inflammatory bowel disease).
    • Diverticulitic stenoses (-10%).
    • Ischemic colonopathy (e.g., due to intermittent atrial fibrillation, atherosclerosis/atherosclerosis/arteriosclerosis)
    • Coprostasis (fecal stasis)
    • NSAID colitis (intestinal inflammation caused by non-steroidal anti-inflammatory drugs).
    • Pancreatitis (inflammation of the pancreas).
    • Peritoneal carcinomatosis (e.g., due toascites, gastric carcinoma, ovarian carcinoma, malignant melanoma).
    • Postinfectious stenosis (e.g., due toEnterohemorrhagic Escherichia coli infection).
    • Postoperative stenosis (due toprevious operations, partial colon resection).
    • Foreign body, etc.
  • Gallstone ileus – intestinal obstruction caused by a gallstone in the intestinal lumen.
  • Hernias (hernia of the intestine caused by a weak point in the abdominal wall) → small bowel ileus (15% of cases); large bowel ileus (5% of cases).
  • Invagination (synonym: intussusception) – invagination of a portion of the intestine into the aborally following segment of the intestine: ileocolic invagination occurs most frequently (ileum/rum or hip (part of the small intestine) into the colon/colon); occurs preferentially in infants/children up to 2 years of age; highest relative risk is 1 – 7 days after 1st dose of rotavirus vaccination
  • Meconium ileus – intestinal obstruction of a newborn due to the meconium (“infant saliva“).
  • Volvulus – rotation of a section of the digestive tract about its mesenteric axis (small bowel volvulus, DV); symptoms: abdominal swelling that develops over two, three days; typical complications are mechanical ileus (intestinal obstruction) or intestinal gangrene (death of a section of the intestine due to insufficient oxygen supply)

Neoplasms (C00-D48)

  • Colon and rectal stenosis/narrowing of the colon and rectum due to a malignancy (malignant tumor): 70% of cases).
  • Peritoneal carcinomatosis/surface infestation of the peritoneum with malignant tumor cells (e.g., due toascites (abdominal dropsy), gastric carcinoma (stomach cancer), ovarian carcinoma (ovarian cancer), malignant melanoma)

Operations

  • Brides (connective tissue adhesions (brides) in the peritoneal cavity (abdominal cavity)) due to previous surgery → small bowel ileus (65% of cases).

Operations

The transition from mechanical ileus to paralytic ileus is always fluid. In the further progression of a mechanical ileus, intestinal paralysis always occurs. In the transitional stage, a mixed ileus is present. The final stage of untreated mechanical ileus is paralytic ileus.

Pathogenesis (disease development)

In functional ileus, there is decreased contraction of the smooth muscle of the intestinal wall

In paralytic ileus (synonym: atonic ileus), intestinal paralysis occurs. This is due to activation of α- and ß-receptors, which lead to inhibition of intestinal peristalsis. The intestinal paralysis is then accompanied by transit peritonitis. Very rare is spastic ileus (e.g., due to lead poisoning). The stoppage of intestinal transit leads to a stretching of the intestinal wall, which in turn leads to a reduction in blood flow. This in turn leads to a restriction of function.In addition, there is penetration of intestinal bacteria into the intestinal wall, which leads to bacteremia or toxicemia (blood poisoning by bacterial toxins). Furthermore, a state of shock with hypovolemia (decrease in circulating blood volume) develops due to edema (“swelling” or “water retention”) affecting the intestinal wall and fluid leakage into the intestine. If left untreated, systemic inflammatory response syndrome (SIRS) progresses to full-blown septic shock with consecutive multiorgan failure (MOV; MODS or MOF).

Etiology (Causes)

Disease-related causes.

Congenital malformations, deformities, and chromosomal abnormalities (Q00-Q99).

  • Hirschsprung’s disease (MH; synonym: megacolon congenitum) – genetic disorder with both autosomal recessive inheritance and sporadic occurrence; disorder that in most cases is affects the last third of the colon (sigmoid and rectum) of the large intestine; belongs to the group of aganglionoses; lack of ganglion cells (“aganglionosis”) in the submucosal plexus or myentericus (Auerbach’s plexus) leads to hyperplasia of the upstream nerve cells, resulting in increased acetylcholine release. Due to the permanent stimulation of the ring muscles, it thus comes to a permanent contraction of the affected section of the intestine.The MH is relatively common with 1: 3,000 – 1: 5,000 births, boys are up to four times more often affected than girls.

Endocrine, nutritional and metabolic diseases (E00-E90).

  • Diabetic ketoacidosis – form of metabolic acidosis that occurs particularly frequently as a complication of diabetes mellitus in the presence of absolute insulin deficiency; the cause is an excessively high concentration of ketone bodies in the blood.
  • Diabetes mellitus
  • Hypokalemia (potassium deficiency)
  • Porphyria or acute intermittent porphyria (AIP); genetic disease with autosomal dominant inheritance; patients with this disease have a 50 percent reduction in the activity of the enzyme porphobilinogen deaminase (PBG-D), which is sufficient for porphyrin synthesis. Triggers of a porphyria attack, which can last a few days but also months, are infections, drugs or alcohol. The clinical picture of these attacks presents as acute abdomen or neurological deficits, which can take a lethal course. The leading symptoms of acute porphyria are intermittent neurologic and psychiatric disturbances. Autonomic neuropathy is often in the foreground, causing abdominal colic (acute abdomen), nausea (nausea), vomiting or constipation (constipation), as well as tachycardia (heartbeat too fast: > 100 beats per minute) and labile hypertension (high blood pressure).

Infectious and parasitic diseases (A00-B99).

  • Bacterial infections (peritonitis/peritonitis, abscess).
  • Herpes zoster (shingles)
  • Parasitoses (parasites)
  • Tabes dorsalis – neurological symptoms that occur in the setting of untreated syphilis infection.

Circulatory system (I00-I99)

  • Vascular disease leading to reduced perfusion of the intestine.

Mouth, esophagus (food pipe), stomach, and intestines (K00-K67; K90-K93).

  • Claudication abdominalis – abdominal pain attacks caused by transient decreased blood flow to the intestine.
  • Inflammatory processes in the abdomen such as:
    • Appendicitis (appendicitis).
    • Cholecystitis (gallbladder inflammation)
    • Pancreatitis (inflammation of the pancreas)
    • Peritonitis (inflammation of the peritoneum)
  • Mechanical ileus
  • Meconium ileus (obstruction of a segment of intestine by a thickened first stool called puerperal feces (meconium); usually the first sign of cystic fibrosis)
  • Occlusive vs. non-occlusive mesenteric ischemia/mesenteric infarction – acute inferior supply to a portion of the intestine due to arterial occlusion.
  • Toxic megacolon – usually occurring as a result of Crohn’s disease, ulcerative colitis, or Hirschsprung’s disease, dilatation of the colon above a Dirck intestine level.

Neoplasms (C00-D48)

Psyche – Nervous System (F00-F99; G00-G99).

  • Myopathies – muscle diseases
  • Neuropathies – diseases of the peripheral nerves that do not have a traumatic cause.
  • Syringomyelia – disease of the spinal cord as a result of a developmental disorder.

Symptoms and abnormal clinical and laboratory findings not elsewhere classified (R00-R99).

  • Uremia (occurrence of urinary substances in the blood above normal levels).

Genitourinary system (kidneys, urinary tract – reproductive organs) (N00-N99).

  • Renal colic
  • Ureteral stone (ureteral stone)

Injuries, poisoning, and other consequences of external causes (S00-T98).

  • Postoperative intestinal atony after abdominal surgery (abdominal procedures)/postoperative ileus (= temporary arrest of coordinated intestinal peristalsis after surgical procedures (> 72 h pathologic).
  • Injuries to the abdominal organs
  • Vertebral body, pelvic fractures

Medication

Operations

  • Postoperative: abdominal or retroperitoneal procedures (spinal surgeries) → reflex functional/paralytic ileus; manifestation usually on day 3 to 5 after surgery; clinical symptoms: nausea (nausea)/vomiting, stool and wind retention, and distended abdomen with scanty or absent peristalsis

Environmental stress – intoxications (poisonings).

  • Alcohol intoxication

Other causes

  • Gravidity (pregnancy)
  • Retroperitoneal causes (hematoma/bruise, spinal trauma).