Ileus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Ileus is defined as the temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The word ileus is derived from the Greek word “είλειν” which means to twist. There is no specific system for classification of postoperative ileus. However, based on etiology, postoperative ileus may be classified into drug induced ileus, ileus secondary to metabolic and electrolyte disturbances and ileus due to some systemic disorders. The pathogenesis of ileus is based on its multifactorial etiology. Ileus is most commonly seen during the postoperative period (usually 3 days after surgery). Commonly used analgesics such as opiates and anesthesia may also aggravate the development of ileus. Enteric and autonomic nervous system disturbances can cause a severe variety of ileus, named chronic intestinal pseudo-obstruction (CIPO), which may be related to some altered genes. Conditions commonly associated with ileus include diabetes mellitus, hypothyroidism, and hypoparathyroidism. The incidence and prevalence of ileus varies with the type of surgery performed. The incidence of ileus in patients undergoing laparotomy is approximately 9,000 per 100,000 cases worldwide, which is more common compared to other surgeries. Common risk factors in the development of ileus include older age, electrolyte abnormalities, previous history of abdominal surgery, postoperative deep venous thrombosis, diabetic ketoacidosis, history of chronic opiates use and hypothyroidism. Patients with ileus are usually presented with abdominal pain, abdominal distention, nausea and vomiting with postprandial discomfort, constipation or obstination and loss of appetite. Common complications of ileus include electrolyte imbalance, dehydration, intestinal perforation, sepsis, jaundice, Intestinal strangulation and pulmonary complications. There are no diagnostic laboratory findings associated with ileus. However, laboratory evaluations must be done to identify the severity and presence of other complications of ileus such as electrolyte abnormalities and hypovolemia. Findings on an x-ray suggestive of ileus include multiple air–fluid levels throughout the abdomen, elevated diaphragm with dilatation of both large and small intestine, slow movement of barium with a patent intestinal lumen. An abdomen and pelvis CT scan (with intravenous contrast and oral water soluble contrast) can also distinguish early postoperative ileus from mechanical obstruction. In addition, a CT scan can also identify other complications seen in the postoperative period or ileus related complications, such as perforation, strangulation and necrosis. Intravenous hydration is advised with appropriate rapid supplementation for electrolyte abnormalities. NSAIDs are used as baseline analgesic medications. Patients are put on NPO and nasogastric tube is advised to relieve recurrent vomiting or abdominal distention associated with pain. Surgical intervention is not routinely recommended for the management of ileus. However, patients with prolonged ileus, radiologic or clinical findings indicating development of ileus complication, such as intestinal perforation, strangulation or necrosis and worsening of clinical or laboratory conditions of patients may require urgent surgical intervention to identify and alleviate complications of ileus.

The word ileus is derived from the Greek word “είλειν” which means to twist. Gallstone ileus was first described by Thomas Bartholin in 1654. The effect of splanchnic nerves on intestinal peristalsis was discovered by Bayliss and Starling in 1899. Later in 1958, Robertson, Eddy and Vosseler delineated a case of ileus, complicated by cecal perforation.

There is no specific system for classification of postoperative ileus. However, based on etiology, postoperative ileus may be classified into drug induced ileus, ileus secondary to metabolic and electrolyte disturbances and ileus due to some systemic disorders.

Ileus is defined as a temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The pathogenesis of ileus is based on its multifactorial etiology. Ileus is most commonly seen during the postoperative period (usually 3 days after surgery). When a patient undergoes a surgical procedure, it often puts the body under significant stress. It is thought that ileus is the result of a surgical stress-induced inflammatory process, that leads to the release of inflammatory and neuroendocrine mediators (such as nitric oxide, VIP and substance P). Additionally, manipulation of the intestine leads to activation of afferent pathways that travel to theBrain stem, which leads to increased autonomic output to the sympathetic neurons and increased secretion of adrenergic neurotransmitters and subsequent decreased intestinal motility. Commonly used analgesics such as opiates and anesthesia may also increase the development of ileus. Enteric and autonomic nervous system disturbances can cause a severe form of ileus, named chronic intestinal pseudo-obstruction (CIPO) which may be related to some altered genes. Conditions commonly associated with ileus include diabetes mellitus, hypothyroidism, and hypoparathyroidism. On gross pathology findings of ileus include bowel contortion with a distended small and large intestine. On microscopic histopathological analysis, findings of ileus include inflammatory cells predominantly macrophages and mast cells.

Common causes of ileus include surgery (major abdominal & non-abdominal surgeries), metabolic and electrolyte disturbances (such as hyponatremia, hypokalemia, hypocalcemia and hypomagnesemia), Endocrine disorders (such as diabetes, hypoparathyroidism, hypothyroidism, and adrenal insufficiency), systemic disorders (such as myocardial infarction, pneumonia, renal failure), trauma, sepsis, and drugs (such as opiates, anticholinergic agents, autonomic blockers, tricyclic antidepressants and general anesthesia).

Ileus must be differentiated from other diseases that cause abdominal pain, constipation, nausea and vomiting such as small bowel obstruction, gastric outlet obstruction, gastroparesis, gastrointestinal perforation, acute cholecystitis, acute pancreatitis, chronic pancreatitis, liver abscess and spontaneous bacterial peritonitis.

Ileus is most commonly seen in patients undergoing surgical treatment. The incidence and prevalence of ileus varies with the type of surgery performed. Patients with large incisions are at a relatively higher risk of developing ileus as compared to patients undergoing minor surgical procedures with small incisions. The incidence of ileus in patients undergoing laparotomy is approximately 9,000 per 100,000 cases worldwide, which is more common compared to other surgeries. The prevalence of ileus is not precisely known. However, it is estimated that that around 10 percent (10,000 per 100,000) of the people undergoing surgical procedures develop ileus that lasts longer than three days. Postoperative ileus has been present in 15% of patients who had partial bowel resection, based on one study. Patients of all age groups may develop ileus but it is more commonly seen in the elderly due to underlying comorbidities. There is no racial predisposition for ileus and men and women are affected equally.

Common risk factors in the development of ileus include older age, electrolyte abnormalities, previous history of abdominal surgery, prolonged abdominal or pelvic surgery, laparotomy, lower Gastrointestinal tract procedures, delayed postoperative enteral nutrition, use of preoperative albumin, postoperative deep venous thrombosis, diabetic ketoacidosis, history of chronic opiates use and hypothyroidism. Less common risk factors include spinal cord injury (specifically thoracic cord), Severe illness like sepsis, obesity, peripheral vascular disease and development of some postoperative complications.

There is insufficient evidence to recommend routine screening for ileus.

Patients with ileus are usually presented with abdominal pain, abdominal distention, abdominal cramping, nausea and vomiting with postprandial discomfort, constipation or obstination and loss of appetite. Common complications of ileus include electrolyte imbalance, malabsorption, dehydration, intestinal perforation, renal failure, ascites, sepsis, jaundice, Intestinal strangulation and pulmonary complications. Depending on the duration of the postoperative ileus at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good. Most cases of postoperative ileus resolve spontaneously and do not require further treatment.

The diagnosis of ileus is made in the presence of positive history and physical exam findings with signs of intestinal aperistalsis on an x-ray. In patients where findings of an x-ray are equivocal, a CT scan of the abdomen should be done to rule out underlying mechanical obstruction as a cause of delayed intestinal motility.

Obtaining a history gives important information in making a diagnosis of ileus. The areas of focus should be on onset, duration, and progression of symptoms with special focus on past medical history and current medications. Previous history of surgery, constipation, hypothyroidism, diabetes and renal failure may predispose an individual to developing ileus. Common symptoms of ileus include postprandial abdominal pain, abdominal discomfort, abdominal distension, nausea and vomiting, feeding intolerance, constipation, flatulence, and belching. Less common symptoms include wound dehiscence and impaired wound healing.

Physical examination of patients with ileus is usually remarkable for abdominal distension, abdominal tenderness, and minimal or absent bowel sounds. Hypotension, fever and tachycardia are possible findings, especially in complicated ileus. Patients with ileus usually appear fatigued and in discomfort. Patients with prolonged ileus may progress to develop peritoneal signs such as rigidity, guarding and rebound tenderness.

There are no diagnostic laboratory findings associated with ileus. However, laboratory evaluations must be done to identify the severity and presence of other complications of ileus such as electrolyte abnormalities and hypovolemia. Common laboratory tests include complete blood count, liver function test, renal function test, serum electrolytes, serum lipase and amylase, arterial blood gas, lactate level, serum albumin and measurement of inflammatory markers.

An abdominal x-ray with barium meal (small bowel series) may be helpful in the diagnosis of ileus. Findings on an x-ray suggestive of ileus include multiple air–fluid levels throughout the abdomen, elevated diaphragm with dilatation of both the large and small intestine, slow movement of barium with a patent intestinal lumen. Serial x-rays may also differentiate paralytic ileus from mechanical intestinal obstruction.

An abdominal and pelvic CT scan is used to confirm the diagnosis of postoperative ileus only in cases when an x-ray is not diagnostic. An abdomen and pelvis CT scan (with intravenous contrast and oral water soluble contrast) can also distinguish early postoperative ileus from mechanical obstruction. In addition, a CT scan can also identify other complications seen in post-operative period or ileus related complications, such as perforation, strangulation and necrosis. Findings on a CT scan diagnostic of postoperative ileus include multiple air–fluid levels throughout the abdomen, an elevated diaphragm, dilation of both the large and small intestine with no evidence of mechanical obstruction.

There are no MRI findings associated with ileus.

There are no specific ultrasound findings associated with ileus. However, patients with ileus for more than seven days (prolonged ileus) may be evaluated with an abdomen and pelvic ultrasound to determine the underlying cause. Prolonged ileus is generally due to mechanical obstruction and an ultrasound can be done to determine the etiology, such as abscess, strangulated hernia and necrotic bowel.

There are no other imaging findings associated with ileus.

Other diagnostic studies for ileus include enteroclysis. An enteroclysis is done when an abdominal x-ray and CT scan are inconclusive but the patient is still suspected of ileus. In enteroclysis, water-soluble radio-opaque contrast medium such as gastrografin is used to observe the movements of intestine. Enteroclysis can also help in differentiating ileus from small bowel obstruction.

The majority of cases of ileus are resolved with correction of underlying electrolyte disorder and only require supportive care. Intravenous hydration is advised with appropriate rapid supplementation for electrolyte abnormalities. NSAIDs are used as baseline analgesic medications. In contrast, opiates and antimotility drugs (such as vagolytic agents) should be avoided generally, although opiates are sometimes used in case of severe intractable pain. Patients are put on a NPO and nasogastric tube to relieve recurrent vomiting or abdominal distention associated with the pain. Prokinetic agents such as erythromycin are not routinely recommended. In paralytic ileus certain medications such as hyoscyamine, methscopolamine bromide, oxycodone, polyethylene glycol-electrolyte solution (PEG-ES) are contraindicated.

Surgical intervention is not routinely recommended for the management of ileus. However, patients with prolonged ileus, radiologic or clinical findings indicating development of ileus complication, such as intestinal perforation, strangulation or necrosis and worsening of clinical or laboratory conditions of patients may require urgent surgical intervention to identify and alleviate complications of ileus.

Effective measures for the primary prevention of ileus include early mobilization, avoidance of Ryle’s tube (nasogastric tube), prior oral feeding with high carbohydrate solid or liquid solution, limiting parenteral fluids, avoidance of pain medications such as opiates, utilizing a minimally invasive surgical method and use of epidural anesthesia for postoperative analgesia.

Effective measures for the secondary prevention of ileus include use of local spinal anesthesia via epidural approach and intravenous (IV) ketorolac as a baseline analgesic for postoperative pain seen in patients of ileus. Ileus associated nausea and vomiting should be treated with serotonin receptor antagonist. Other measures include early mobilization and ambulation, removal of urinary catheter within 24 to 48 hours of surgery with avoidance of routine nasogastric tubes and abdominal drains.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

The word ileus is derived from the Greek word “είλειν” which means to twist. Gallstone ileus was first described by Thomas Bartholin in 1654. The effect of splanchnic nerves on intestinal peristalsis was discovered by Bayliss and Starling in 1899. Later in 1958, Robertson, Eddy and Vosseler delineated a case of ileus, complicated by cecal perforation.

• The word “ileus” is derived from the Greek word “είλειν” which means to twist. The word “είλειν” also gave rise to the section of the intestine termed as the “ileum“.
• In 1654, Thomas Bartholin was the first to describe a case of gallstone ileus in a necroscopy study.^[1]
• In 1899, Bayliss and Starling demonstrated a relationship between splanchnic nerves ablation and intestinal peristalsis improvement, in postoperative status.^[2]
• In 1958, Robertson, Eddy and Vosseler were the first to describe a case of adynamic ileus associated with cecal perforation.^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

There is no specific system for classification of postoperative ileus. However, based on etiology, postoperative ileus may be classified into drug-induced ileus, ileus secondary to metabolic and electrolyte disturbances, and ileus due to some systemic disorders.

There is no specific system for classification of postoperative ileus. However, based on etiology, postoperative ileus may be classified into drug-induced ileus, ileus secondary to metabolic and electrolyte disturbances, and ileus due to some systemic disorders.^[1][2]

Postopertive ileus

Drug-induced ileus

Ileus due to metabolic & electrolyte disturbances

ileus due to Systemic disorders

•Opiates •Anticholinergics •Autonomic blockers •Psychotropic drugs •General anaesthesia

•Hypokalemia •Hyponatremia •Hypomagnesemia •Hypophosphatemia

•Diabetes •Hypoparathyroidism •Renal failure •Sepsis •Pneumonia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Ileus is defined as a temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The pathogenesis of ileus is based on its multifactorial etiology. Ileus is most commonly seen during the postoperative period (usually 3 days after surgery). When a patient undergoes a surgical procedure, it often puts the body under significant stress. It is thought that ileus is the result of a surgical stress-induced inflammatory process, that leads to the release of inflammatory and neuroendocrine mediators (such as nitric oxide, VIP and substance P). Additionally, manipulation of the intestine leads to activation of afferent pathways that travel to the brain stem, which leads to increased autonomic output to the sympathetic neurons and increased secretion of adrenergic neurotransmitters and subsequent decreased intestinal motility. Commonly used analgesics such as opiates and anesthesia may also aggravate the development of ileus. Enteric and autonomic nervous system disturbances can cause a severe form of ilues, called chronic intestinal pseudo-obstruction (CIPO) which may be related to some altered genes. Conditions commonly associated with ileus include diabetes mellitus, hypothyroidism, and hypoparathyroidism. Gross pathology findings of ileus include bowel contortion with a distended small and large intestine. On microscopic histopathological analysis, findings of ileus include inflammatory cells predominantly macrophages and mast cells.

• The gastrointestinal tract is regulated by the enteric nervous system, autonomic nervous system and interacts with central nervous system.
• The enteric nervous system (ENS) is also known as an intrinsic neural network and consists of neurons located in the walls of Gastrointestinal tract.
  • Enteric nervous system (ENS) includes the myenteric plexus (Auerbach’s plexus) and submucosal plexuses (Meissner’s plexus).
  • The myenteric plexus is located in the muscular layer and is also known as the Auerbach’s plexus.
  • The submucosal plexuses is located in the submucosal layer and is also known as the Meissner’s plexus.
• The autonomic nervous system (ANS) is also known as the extrinsic nervous system.
  • The autonomic nervous system (ANS) consists of the sympathetic and parasympathetic nervous system, which control Gastrointestinal tract function.
  • The sympathetic nervous system is inhibitory to visceral smooth muscle activity and decreases peristalsis and Gastrointestinal tract motility.
  • The parasympathetic nervous system is stimulatory to visceral smooth muscle activity and increases peristalsis and Gastrointestinal tract motility.
  • The afferent visceral sensory system of the GI tract is part of the parasympathetic nervous system, while the efferent visceral motor system is located in both sympathetic and parasympathetic autonomic nervous system.
  • In addition, the extrinsic nervous system synapse with the enteric nervous system and relay information to the central nervous system.

• Ileus is defined as the temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The pathogenesis of ileus is based on its multifactorial etiology.^[1][2][3]
• Intestinal peristalsis is primarily regulated by the enteric nervous system, autonomic nervous system and their interactions with the central nervous system (CNS). However, certain medications and metabolic products may also alter the normal intestinal equilibrium leading to temporary dysfunction in intestinal movements. Prolonged intestinal aperistalsis results in the accumulation of air and fluid in the intestinal lumen.
• The most common cause of ileus is abdominal surgery.^[1][2][3]
  • The risk of postoperative ileus depends upon the type of surgery; laparoscopic procedures have lower risk, compared to laparotomy which have the highest risk.
  • The highest risk for postoperative ileus has been observed with colorectal surgeries.
  • In fact, postoperative ileus (due to any surgery) is so common that it is sometimes regarded as a normal sequelae of surgery.
  • Postoperative ileus that lasts longer than 3 days is termed as paralytic ileus or adynamic ileus.
  • When a patient undergoes a surgical procedure, it often puts the body under significant stress.
    • This surgical stress may lead to the release of inflammatory and neuroendocrine mediators (such as nitric oxide, VIP and substance P) that may result in the inhibition of intestinal motility and development of ileus.^[4]
    • Stress inducing conditions may lead to increased recruitment of dendritic cells, natural killer cells, monocytes, T cells, macrophages, and mast cells. The macrophages and mast cells are considered the key cells leading to the initiation and maintenance of the inflammatory process and release of chemical mediators.
    • Recent research has shown that inhibition of inflammatory mediators (such as nitric oxide & VIP) may lead to improved gastrointestinal peristalsis and function.
    • The site of the surgery is the most common affected part of the GI tract. However, recent research has shown that inflammation of the intestinal muscle may extend from the site of surgery to other parts of the intestinal tract.^[5]
    • Moreover, intestinal distention seen in ileus is contributed to serosal injury and may aggravate intestinal ischemia.
    • Prolonged ileus leads to increased contact between various segments of intestine which predispose to fibrous adhesion formation, thereby further contributing to the severity of ileus. ^[6][7]
    • Abdominal conditions such as gastroenteritis and peritonitis may also affect the intestinal motility leading to ileus.
  • Abdominal incision leads to the activation of inhibitory spinal reflex which results in decreased movements of the intestine, as a regulatory mechanism.^[8]
    • The painful stimulates the spinal afferents that synapse in the spinal cord. The prevertebral adrenergic neurons in the spinal cord activate and inhibit intestinal motility via efferent nerves (sympathetic ANS).
    • Additionally, manipulation of the intestine leads to the activation of afferent pathways that travel to the brain stem. In turn, the brain stem increases autonomic output to the sympathetic neurons located in the inter-medio-lateral column of the thoracic cord. The increased activity of sympathetic neurons results in increased secretion of adrenergic output and subsequent decreased intestinal motility.
• There is a chronic and severe form of ileus, known as chronic intestinal pseudo-obstruction (CIPO).^[9][10][11]
  • CIPO is a severe form of ileus resulting from disturbances in the enteric nervous system, autonomic nervous system and smooth muscle cell function.
  • The cause of CIPO can be idiopathic, sporadic, or secondary to metabolic, connective tissue, endocrinologic, neurologic, and paraneoplastic disorders.^[12]
  • CIPO is often due to dysfunction in innervation of smooth muscle by the interstitial cells of Cajal resulting in partial or completely ineffective intestinal propulsion. However, any condition affecting the enteric nervous system, autonomic nervous system, smooth muscle cells and neuromuscular junction may lead to development of CIPO.
  • The lack of propulsive intestinal movements may lead to increased intra-luminal pressure.
  • The enhanced intra-luminal pressure leads to malabsorption and bacterial overgrowth. Over time, it can progress to present with malnutrition and sepsis.
• The other common cause of ileus are the drugs that affect intestinal motility and alteration in electrolyte levels.
  • Drugs affecting intestinal motility primarily include antimotility agents and anesthetics.
    • Anesthetic drugs: Anesthetic agents have a direct inhibitory effect on the intestinal motility. Long-acting anesthetic agents such as bupivacaine are more frequently associated with postopertaive ileus as compared to short-acting agents such as propofol.
    • Opiates: The use of opiates for pain alleviation is not without side effects. In fact, opioid use has been associated with significant increase in the occurrence of postoperative ileus. Opioid medications that activate the µ (mu) receptors have been associated with decreased release of acetylcholine from cholinergic neurons, resulting in delayed intestinal motility. The most common opioid pain medication, morphine, initially activates the migrating myoelectric complex and later results in atony, resulting in inhibition of propulsion and delay in intestinal transit.
  • Electrolyte abnormalities such as hypokalemia, hyponatremia, hypocalcemia, hypomagnesemia, and metabolic acidosis may also lead to the development of intestinal ileus.

There is no detected genetic disorder related to ileus, nevertheless, some cases of CIPO are related to alteration in FLNA and ACTG2 genes.

• Diabetes mellitus^[13]
• Hypothyroidism^[14]
• Hypoparathyroidism^[15]
• Hirschsprung disease^[16][17]
• Orthostatic hypotension^[18]
• CNS neoplasms^[19]
• Leiomyosarcomas^[20]
• Radiation enteritis^[21]
• Chagas disease^[22]

Gross pathologic findings of ileus include:^[23]

• Bowel contortion
• Distended small and large intestine

On microscopic histopathological analysis, findings of ileus include inflammatory cells predominantly macrophage and mast cells.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Common causes of ileus include surgery (major abdominal & non-abdominal surgeries), metabolic and electrolyte disturbances (such as hyponatremia, hypokalemia, hypocalcemia and hypomagnesemia), Endocrine disorders (such as diabetes, hypoparathyroidism, hypothyroidism, and adrenal insufficiency), systemic disorders (such as myocardial infarction, pneumonia, renal failure), trauma, sepsis, and drugs (such as opiates, anticholinergic agents, autonomic blockers, tricyclic antidepressants and general anesthesia).

The common causes of ileus include:^{[1][2][3][4][5]}

• Any abdominal surgery
• Acute pancreatitis
• Hypokalemia
• Mechanical ventilation
• Morphine
• Pancreatitis
• Peritonitis
• Retroperitoneal hematoma
• Mesenteric infarction
• Uremia
• Urosepsis
• Trauma

Cardiovascular	Heart Attack
Chemical/Poisoning	Lead poisoning, Thallium
Dental	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	Anticholinergic drugs, Acetaminophen, Oxycodone, Antihistamines, Benzatropine, Ixabepilone, Ioxilan,Lanthanum carbonate, Loperamide, meclofenamate,Meropenem, Morphine, Olanzapine, Opiates, Pramipexole, Vinblastine
Ear Nose Throat	No underlying causes
Endocrine	Diabetic coma, Diabetic ketoacidosis, Hyperparathyroidism
Environmental	No underlying causes
Gastroenterologic	Adenomatous polyps, Annular pancreas, Appendicitis, Atresia, Biliary calculus, Cholecystitis, Cholecystolithiasis, Colon Cancer, Complications of intra-abdominal surgery, Congenital megacolon, Crohn’s Disease, Diverticular stricture, Diverticulitis, Gallstone ileus, Gastrointestinal bleeding, Hematoma of the bowel wall, Hemoperitoneum, Hernia, Incarcerated hernia, Intestinal ischaemia, Intrabdominal hematoma, Intussusception , Megacolon, Mesenteric infarction, Mesenteric ischemia, Multiple polyposis syndromes, Superior mesenteric artery occlusion, Ulcer perforation, Ulcerative colitis, Volvulus
Genetics	Hirschprung’s disease, Imperforate anus, Malrotation, Meckel’s Diverticulum
Hematologic	Lymphoma, Retroperitoneal hematoma
Iatrogenic	Abdominal surgery, Adhesions, Anastomotic leaks, Joint or spine surgery, Laparotomy, Postoperative, Surgery complication, Surgical anastomosis
Infectious Disease	Peritonitis , Abdominal infections, Abdominopelvic abscess, Ascariasis, Botulism, Infection, Intrabdominal abscess, intraperitoneal infection, Osteomyelitis of the Spinal cord, Pancreatitis, Perinephric abscess, Peritonitis, Pneumatosis intestinalis, Pneumonia, Psoas abscess, Sepsis, Severe generalized infections , Tuberculosis, Urosepsis
Musculoskeletal/Orthopedic	No underlying causes
Neurologic	Spinal cord inflammation, Spinal cord injury
Nutritional/Metabolic	Acute intermittent porphyria
Obstetric/	Endometriosis, Neonatal necrotizing enterocolitis, Pregnancy
Oncologic	Cancer, Peritoneal carcinomatosis, Sarcoma, lymphoma
Ophthalmologic	No underlying causes
Overdose/Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	Mechanical ventilation
Renal/Electrolyte	Acid-base imbalance disturbance, Hypokalaemia, Hypomagnesemia, Kidney diseases, Pyelonephritis, Renal colic, Uremia
Rheumatology/Immunology/Allergy	Connective tissue disease, Henoch-Schönlein purpura, Scleroderma
Sexual	No underlying causes
Trauma	Injury or trauma to abdomen , Injury to the abdominal blood supply , Penetrating wounds
Urologic	No underlying causes
Miscellaneous	Apoplexy, Burns, Cysts, Disorders that affect muscle function, foreign bodies , Radiation induced stenosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Ileus must be differentiated from other diseases that cause abdominal pain, constipation, nausea and vomiting such as small bowel obstruction, gastric outlet obstruction, gastroparesis, gastrointestinal perforation, acute cholecystitis, acute pancreatitis, chronic pancreatitis, liver abscess and spontaneous bacterial peritonitis.

Ileus must be differentiated from other diseases that cause abdominal pain, constipation, nausea and vomiting. The differentials include the following:^{[1][2][3][4][5][6][7][8][9]}

Abbreviations: RUQ= Right upper quadrant of the abdomen, LUQ= Left upper quadrant, LLQ= Left lower quadrant, RLQ= Right lower quadrant, LFT= Liver function tests, SIRS= Systemic inflammatory response syndrome, ERCP= Endoscopic retrograde cholangiopancreatography, IV= Intravenous, N= Normal, AMA= Anti mitochondrial antibodies, LDH= Lactate dehydrogenase, GI= Gastrointestinal, CXR= Chest X-ray, IgA= Immunoglobulin A, IgG= Immunoglobulin G, IgM= Immunoglobulin M, CT= Computed tomography, PMN= Polymorphonuclear cells, ESR= Erythrocyte sedimentation rate, CRP= C-reactive protein, TS= Transferrin saturation, SF= Serum Ferritin, SMA= Superior mesenteric artery, SMV= Superior mesenteric vein, ECG= Electrocardiogram, US = Ultrasound

Disease Clinical manifestations Diagnosis Comments Symptoms Signs Abdominal Pain Fever Rigors and chills Nausea or vomiting Jaundice Constipation Diarrhea Weight loss GI bleeding Hypotension Guarding Rebound Tenderness Bowel sounds Lab Findings Imaging Ileus Diffuse – – + – + – ± – + – ± Hypoactive Electrolyte abnormalities such as hypokalemia, hypomagnesemia, hyponatremia Increased WBC Multiple air–fluid levels throughout the abdomen Dilatation of both the large and small intestine Hypoactive bowel sounds Most commonly seen in the postoperative state Small bowel obstruction Diffuse + − + − + − + − + + ± Hyperactive then absent Leukocytosis with left shift indicates complications Abdominal X-ray Dilated loops of the bowel with air-fluid levels Gasless abdomen “Target sign”– , indicative of intussusception Venous cut-off sign” – suggests thrombosis Gastric outlet obstruction Epigastric − − ± − − − + − − − − Hyperactive Complete blood count Basic metabolic panel Abdominal x-ray– air-fluid level Barium upper GI studies– narrowed pylorus Succussion splash Gastroparesis Epigastric − − + − − − + − ± − − Hyperactive/hypoactive Hemoglobin Fasting plasma glucose Serum total protein, albumin, thyrotropin (TSH), and an antinuclear antibody (ANA) titer HbA1c Scintigraphic gastric emptying Succussion splash Single photon emission computed tomography (SPECT) Full thickness gastric and small intestinal biopsy Gastrointestinal perforation Diffuse + ± – ± − − − + + + ± Hyperactive/hypoactive WBC> 10,000 Air under diaphragm in upright CXR Hamman’s sign Disease Abdominal Pain Fever Rigors and chills Nausea or vomiting Jaundice Constipation Diarrhea Weight loss GI bleeding Hypotension Guarding Rebound Tenderness Bowel sounds Lab Findings Imaging Comments Acute cholecystitis RUQ + − + + − − − − − − − Hypoactive Hyperbilirubinemia Leukocytosis Ultrasound shows: Gallstone Inflammation Murphy’s sign Acute pancreatitis Epigastric + − + ± − − + − ± − − N Increased amylase / lipase Ultrasound shows evidence of inflammation CT scan shows severity of pancreatitis Pain radiation to back Chronic pancreatitis Epigastric − − ± ± − + + − − − − N Increased amylase / lipase Increased stool fat content Pancreatic function test CT scan Calcification Pseudocyst Dilation of main Pancreatic duct Predisposes to pancreatic cancer Liver abscess RUQ + + + + − ± + − + + ± Normal or hypoactive CBC Blood culture Abnormal liver function tests CT scan shows cluster sign Ultrasound is the gold standard technique for diagnosing amoebic liver abscess Both lobes are commonly involved Spontaneous bacterial peritonitis Diffuse + − − Positive in cirrhotic patients − + − − ± + + Hypoactive Ascitic fluid PMN>250 cells/mm³ Culture: Positive for single organism Ultrasound for evaluation of liver cirrhosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Ileus is most commonly seen in patients undergoing surgical treatment. The incidence and prevalence of ileus varies with the type of surgery performed. Patients with large incisions are at a relatively higher risk of developing ileus as compared to patients undergoing minor surgical procedures with small incisions. The incidence of ileus in patients undergoing laparotomy is approximately 9,000 per 100,000 cases worldwide, which is more common compared to other surgeries. The prevalence of ileus is not precisely known. However, it is estimated that that around 10 percent (10,000 per 100,000) of the people undergoing surgical procedures develop ileus that lasts longer than three days. Postoperative ileus has been present in 15% of patients who had partial bowel resection, based on one study. Patients of all age groups may develop ileus but it is more commonly seen in the elderly due to underlying comorbidities. There is no racial predisposition for ileus and both men and women are affected equally.

Ileus is most commonly seen in patients undergoing surgical treatment.^{[1][2][3][4][5]}

• The incidence of ileus in patients undergoing laparotomy is approximately 9,000 per 100,000 cases worldwide.
• The incidence of ileus in patients undergoing thoracic procedures is approximately 1,400 per 100,000 cases worldwide.
• The incidence of ileus in patients undergoing orthopaedic procedures is approximately 1,500 per 100,000 cases worldwide.

• Ileus is most commonly seen in patients undergoing surgical treatment. Ileus is a common complication in the postoperative setting and is often considered a normal sequelae of surgery and the majority of the cases are not reported. Postoperative ileus has been present in 15% of patients who had partial bowel resection, based on one study.^[5]
• Although no precise data is available regarding the prevalence of ileus, the following data gives an estimate of ileus lasting longer than 3 days in the postoperative setting. ^[2][1]
  • It is estimated that that around 10 percent of the patients (or 10,000 per 100,000 cases) undergoing surgical procedures develop ileus that lasts longer than 3 days.
  • In the United States, approximately 2.7 million patients developed postoperative ileus lasting more than 1 day.

• Patients of all age groups may develop ileus.
• Ileus is more commonly seen in elderly patients due to underlying comorbidities.

There is no racial predisposition to ileus.

Ileus affects both men and women equally.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Common risk factors in the development of ileus include older age, electrolyte abnormalities, previous history of abdominal surgery, prolonged abdominal or pelvic surgery, laparotomy, lower Gastrointestinal tract procedures, delayed postoperative enteral nutrition, use of preoperative albumin, postoperative deep venous thrombosis, diabetic ketoacidosis, history of chronic opiates use and hypothyroidism. Less common risk factors include spinal cord injury (specifically thoracic cord), severe illness like sepsis, obesity, peripheral vascular disease and development of some postoperative complications.

Common risk factors in the development of ileus include:^{[1][2][3][4][5][6]}

• Older age
• Electrolyte abnormalities
• Previous history of abdominal surgery
• Prolonged abdominal or pelvic surgery
• Laparotomy and lower GI procedures
• Delayed enteral nutrition
• Use of preoperative albumin
• Postoperative deep venous thrombosis
• Hypothyroidism
• Diabetic ketoacidosis
• Chronic use of opiates such as morphine

Less common risk factors in the development of ileus include:^[7][8][9]

• Severe illness such as sepsis
• Spinal cord injury (Thoracic cord)
• Obesity
• Peripheral vascular disease
• Any common complications arising from surgery can increase the risk of ileus. These complications include:
  • Pneumonia
  • Intra-abdominal abscess
  • Peritonitis
  • Bleeding disorder
  • Excessive use of Analgesics for postoperative pain control

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

There is insufficient evidence to recommend routine screening for ileus.

There is insufficient evidence to recommend routine screening for ileus.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]

Patients with ileus are usually presented with abdominal pain, abdominal distention, abdominal cramping, nausea and vomiting with postprandial discomfort, constipation or obstination and loss of appetite. Common complications of ileus include electrolyte imbalance, malabsorption, dehydration, intestinal perforation, renal failure, ascites, sepsis, jaundice, intestinal strangulation and pulmonary complications. Depending on the duration of the postoperative ileus at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good. Most cases of postoperative ileus resolve spontaneously and do not require further treatment.

• Patients with ileus are usually presented with:^[1][2][3][4]
  • Abdominal pain, cramping and discomfort
  • Abdominal distension
  • Nausea and vomiting and postprandial discomfort
  • Constipation or obstination
  • Loss of appetite
• Depending on duration and etiology of ileus (surgery or drugs), symptoms may range from mild to severe.
• In postoperative ileus, some patients may have symptom resolution within 1-2 days after surgery.
• In patients with no symptom resolution 1-2 days after surgery, development of more severe symptoms, such as complete cessation of intestinal motility, malabsorption, sepsis and intestinal perforation could be seen.
• Patients with sepsis and intestinal perforation require urgent medical attention and intervention. If left untreated, severe ileus may be fatal.

Complications of ileus include:^{[5][6][7][8][9][10][11][12][13][14]}

• Electrolyte imbalance
• Renal failure
• Malabsorption
• Dehydration
• Intestinal perforation
• Ascites
• Sepsis
• Jaundice
• Pulmonary complications
• Intestinal strangulation

• Depending on the duration of the postoperative ileus at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good.^[15][16][3]
• Most cases of postoperative ileus resolve spontaneously and do not require further treatment.
• In general, correction of electrolyte abnormalities, avoidance of opioids analgesics and hydration leads to rapid reversal of symptoms associated with ileus.
• Prolonged postoperative ileus (> 7 days) requires close monitoring and evaluation for underlying mechanical obstruction.

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