Megacolon

Megacolon is a severe, abnormal dilatation of the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix, and is classified as acute or chronic. There are many etiologies of megacolon, including neuropathic and dysmotility conditions, severe infections, ischemia, and inflammatory bowel disease. Toxic megacolon is an acute form of megacolon with systemic toxicity, and carries the highest morbidity and mortality. Common symptoms include abdominal distention, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, bloody diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea, or obstipation. Diagnosis depends on the underlying cause, and is usually established with a combination of the patient’s history, laboratory findings, and imaging studies. Patients with chronic megacolon may require laxatives Laxatives Laxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient. Laxatives, enemas, and bowel training. Management for acute megacolon includes supportive care, decompression, and potential surgery.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition and classification

Megacolon is a severe dilatation of the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix secondary to impaired motility or an inflammatory process. The condition is classified based on the time course and duration:

  • Acute megacolon
  • Chronic megacolon

Epidemiology

  • Exact incidence is unknown.
  • All ages may be affected.
  • Incidence depends on the underlying disease:
    • Congenital aganglionic megacolon: 
      • 1 in 5,000 live births
      • Men > women
    • Toxic megacolon:
      • 4.3% in patients with Clostridioides difficile, previously known as Clostridium difficile, colitis
      • 1%–10% in inflammatory bowel disease (IBD)

Etiology of acute megacolon

  • Toxic megacolon (non-obstructive colonic dilation with systemic toxicity)
    • IBD
      • Ulcerative colitis Ulcerative colitis Ulcerative colitis (UC) is an idiopathic inflammatory condition that involves the mucosal surface of the colon. It is a type of inflammatory bowel disease (IBD), along with Crohn's disease (CD). The rectum is always involved, and inflammation may extend proximally through the colon. Ulcerative Colitis
      • Crohn’s disease
    • Ischemic colitis
    • Infectious colitis
      • C. difficile colitis (most common)
      • Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella
      • Shigella Shigella Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir. Shigella
      • Campylobacter Campylobacter Campylobacter ("curved bacteria") is a genus of thermophilic, S-shaped, gram-negative bacilli. There are many species of Campylobacter, with C. jejuni and C. coli most commonly implicated in human disease. Campylobacter
      • Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli O157
      • Cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus (CMV) colitis (usually in immunodeficient patients)
      • Entamoeba histolytica
  • Acute colonic pseudo-obstruction (Ogilvie’s syndrome)
    • Severe systemic illness
    • Surgery (most commonly from cesarean section or hip surgery)
    • Trauma
    • Spinal anesthesia Anesthesia Anesthesiology is the field of medicine that focuses on interventions that bring a state of anesthesia upon an individual. General anesthesia is characterized by a reversible loss of consciousness along with analgesia, amnesia, and muscle relaxation. Anesthesiology: History and Basic Concepts
    • Medications
      • Opiates
      • Anticholinergics
      • Calcium channel blockers Calcium Channel Blockers Calcium channel blockers (CCBs) are a class of medications that inhibit voltage-dependent L-type calcium channels of cardiac and vascular smooth muscle cells. The inhibition of these channels produces vasodilation and myocardial depression. There are 2 major classes of CCBs: dihydropyridines and non-dihydropyridines. Class 4 Antiarrhythmic Drugs (Calcium Channel Blockers)

Etiology of chronic megacolon

  • Congenital aganglionic megacolon (Hirschsprung’s disease)
    • Most cases associated with mutations in the RET proto-oncogene
    • Sometimes associated with other genetic syndromes: 
      • Down’s syndrome
      • Multiple endocrine neoplasia Multiple endocrine neoplasia Multiple endocrine neoplasia syndromes are autosomal dominant inherited conditions characterized by 2 or more hormone-producing tumors involving the endocrine organs. There are different types of MEN, namely MEN1-4. Multiple Endocrine Neoplasia (MEN) type 2A or 2B
      • Waardenburg syndrome
  • Acquired 
    • Chronic idiopathic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation (most common)
    • Neuropathies 
      • Diabetic
      • Spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord injury
      • Parkinson’s disease
      • Chagas disease Chagas disease Chagas disease is an infection caused by the American trypanosome Trypanosoma cruzi. This parasitic protozoan is transmitted in the feces of reduviid bugs in South and Central America. Acute infection may present with inflammation at the inoculation site (chagoma), fever, and lymphadenopathy. Untreated, chronic infection can progress to severe complications. Trypanosoma cruzi/Chagas disease (through destruction of enteric neurons)
    • Myopathies: Duchenne muscular dystrophy Duchenne muscular dystrophy Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder that is caused by a mutation in the DMD gene. The mutation leads to the production of abnormal dystrophin, resulting in muscle-fiber destruction and replacement with fatty or fibrous tissue. Duchenne Muscular Dystrophy
    • Rheumatologic disorders 
      • Scleroderma Scleroderma Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs. Scleroderma
      • Systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus
      • Dermatomyositis and polymyositis Polymyositis Polymyositis (PM) is an autoimmune inflammatory myopathy caused by T cell-mediated muscle injury. The etiology of PM is unclear, but there are several genetic and environmental associations. Polymyositis is most common in middle-aged women and rarely affects children. Polymyositis

Pathophysiology

Toxic megacolon

  • Mucosal inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation:
    • Causes the release of inflammatory mediators → induction of nitric oxide synthase → nitric oxide generation by macrophages and smooth muscle cells → smooth muscle relaxation → colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix dilation
    • Extends to the smooth muscle layer → paralysis of smooth muscle → colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix dilation
  • Potential precipitating factors:
    • Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia
    • Medications:
      • Opiates
      • Anticholinergics
      • Antidepressants
      • Bowel preparation solutions or barium
    • Abrupt discontinuation of steroids or mesalamine in IBD

Acute colonic pseudo-obstruction

  • Exact mechanism is unknown.
  • Impairment of parasympathetic fibers S2–S4 has been implicated.
  • Progressive distention and ↑ tension on the colonic wall

Congenital aganglionic megacolon

  • Failure of neural crest cell migration during the embryonic intestinal development → distal colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix is aganglionic and nonfunctioning → distension of the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix proximal to the aganglionic segment
  • Nerve plexuses affected: 
    • Meissner (submucosal plexus)
    • Auerbach (myenteric plexus)
  • The amount of colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix affected varies.

Chronic acquired megacolon

  • Incompletely understood
  • Neurologic or muscular dysfunction → disruption in normal peristalsis → progressive colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix dilation
  • Megacolon and megarectum from chronic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation is associated with:
    • ↑ rectal compliance and elasticity
    • Blunted rectal sensation
    • ↑ threshold of anal sphincter relaxation

Clinical Presentation

Symptoms

  • Common symptoms:
    • Abdominal distention
    • Obstipation
  • Toxic megacolon:
    • Bloody diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea (most common)
    • Sudden cessation of diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea should also be concerning.
    • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Malaise
  • Congenital aganglionic megacolon:
    • Majority will present in the neonatal period.
    • Bilious emesis
    • Failure to pass meconium or stool
    • Feeding intolerance and failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive

Physical exam

  • Common findings:
    • Abdominal distension
    • Tympanic abdomen
  • Toxic megacolon:
    • Tachycardia
    • Fever 
    • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
    • Altered mental status
    • Abdominal distension
    • Lower abdominal tenderness
    • Possible evidence of peritonitis
      • Diffuse abdominal tenderness
      • Rebound tenderness
      • Rigidity
  • Congenital aganglionic megacolon:
    • Tight anal sphincter
    • Release of stool and gas with digital examination

Diagnosis

Laboratory evaluation

These studies help evaluate the severity of the disease, complications, and potential causes.

  • General findings:
    • Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia (gastrointestinal loss)
    • Metabolic alkalosis Metabolic alkalosis The renal system is responsible for eliminating the daily load of non-volatile acids, which is approximately 70 millimoles per day. Metabolic alkalosis also occurs when there is an increased loss of acid, either renally or through the upper GI tract (e.g., vomiting), increased intake of HCO3-, or a reduced ability to secrete HCO3- when needed. Metabolic Alkalosis ( dehydration Dehydration Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Dehydration is primarily caused by decreased water intake and presents with increased thirst and can progress to altered mental status and low blood pressure if severe. Volume Depletion and Dehydration)
    • Metabolic acidosis Metabolic acidosis The renal system is responsible for eliminating the daily load of non-volatile acids, which is approximately 70 millimoles per day. Metabolic acidosis occurs when there is an increase in the levels of new non-volatile acids (e.g., lactic acid), renal loss of HCO3-, or ingestion of toxic alcohols. Metabolic Acidosis and ↑ lactic acid are concerning for colonic ischemia.
    • ↑ blood urea nitrogen (BUN):creatinine ratio ( dehydration Dehydration Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Dehydration is primarily caused by decreased water intake and presents with increased thirst and can progress to altered mental status and low blood pressure if severe. Volume Depletion and Dehydration)
  • Findings in toxic megacolon:
    • Complete blood count (CBC):
      • Leukocytosis with left shift
      • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview (due to gastrointestinal blood loss)
    • ↑ erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
    • Stool studies:
      • Culture for bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview and parasites
      • C. difficile toxin

Imaging

  • Abdominal X-ray 
    • Colon dilatation (> 6 cm)
    • Significant stool retention may be seen.
    • May show transition zone between dilated colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix and narrow rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal in Hirschsprung’s disease
    • Air-fluid levels can be present.
    • Toxic megacolon findings:
      • Right and transverse colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix dilation are the most prominent.
      • Loss of normal haustral pattern
      • Mucosal ulcerations
  • Computed tomography (CT) with oral and intravenous (IV) contrast
    • Colonic dilatation (> 6 cm)
    • Free air indicates perforation.
    • May show fecal impaction or stool burden in cases associated with chronic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation
    • Toxic megacolon:
      • Loss of haustral pattern
      • Segmental colonic wall thinning
      • Nodular pseudopolyps (deep mucosal ulcerations)
      • Ischemia (if present)
  • Colonic transit studies
    • Assesses colonic motility in chronic megacolon
    • Options:
      • Radiopaque marker study
      • Wireless motility capsule

Other studies

  • Endoscopy 
    • For toxic megacolon:
      • Complete colonoscopy is avoided due to the high risk of perforation
      • Limited sigmoidoscopy may help establish an underlying etiology (C. difficile CMV, IBD)
    • For chronic megacolon:
      • Colonoscopy can rule out obstruction.
      • Biopsy can be performed if the etiology is unknown.
  • Studies for Hirschsprung’s disease:
    • Rectal biopsy
      • Gold standard
      • Absence of ganglion cells
    • Anorectal manometry
      • Lack of internal anal sphincter relaxation with rectal balloon dilation
      • Less accurate in neonates and people with chronic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation
    • Contrast enema: transition zone between narrowed rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal and proximal dilated colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix

Diagnostic criteria for toxic megacolon

  • Radiographic evidence of colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix distension
  • And ≥ 3 of the following:
    • Fever
    • Tachycardia
    • Leukocytosis
    • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview
  • And ≥ 1 of the following:
    • Dehydration
    • Altered mental status
    • Electrolyte abnormalities
    • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension

Management

Toxic megacolon

  • General management:
    • Patients should be monitored in an intensive care unit (ICU).
    • Serial abdominal exams
    • Laboratory studies and abdominal X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays every 12 hours 
    • NPO (nothing by mouth)
    • IV hydration and electrolyte replacement
    • Nasogastric decompression, if vomiting or small bowel dilatation is present
    • Discontinue any antimotility, opiates, or anticholinergic Anticholinergic Anticholinergic drugs block the effect of the neurotransmitter acetylcholine at the muscarinic receptors in the central and peripheral nervous systems. Anticholinergic agents inhibit the parasympathetic nervous system, resulting in effects on the smooth muscle in the respiratory tract, vascular system, urinary tract, GI tract, and pupils of the eyes. Anticholinergic Drugs medications.
    • IV broad-spectrum antibiotics
      • Reduce septic complications
      • Cover for potential peritonitis from perforation
  • Address the specific cause:
    • C. difficile colitis:
      • Oral vancomycin + metronidazole (oral or intravenous)
      • Vancomycin enemas (can cause perforation)
      • Fecal transplant
    • IBD:
      • Intravenous glucocorticoids Glucocorticoids Glucocorticoids are a class within the corticosteroid family. Glucocorticoids are chemically and functionally similar to endogenous cortisol. There are a wide array of indications, which primarily benefit from the antiinflammatory and immunosuppressive effects of this class of drugs. Glucocorticoids
      • Infliximab or cyclosporine (2nd-line)
  • Surgical management:
    • Indications:
      • If no clinical improvement within 48–72 hours
      • Perforation
      • Peritonitis or worsening abdominal exam
      • Worsening colonic distention
      • Ischemia or necrosis
      • Massive colonic hemorrhage
      • Worsening systemic toxicity ( fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, hemodynamics, or mental status)
      • Abdominal compartment syndrome Compartment Syndrome Compartment syndrome is a surgical emergency usually occurring secondary to trauma. The condition is marked by increased pressure within a compartment that compromises the circulation and function of the tissues within that space. Compartment Syndrome or abdominal hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
    • Procedures:
      • Preferred in IBD: subtotal colectomy with end-ileostomy
      • Preferred in C. difficile:
        • Total abdominal colectomy
        • Diverting loop ileostomy with colonic lavage
Toxic megacolon in operation

Surgical findings for toxic megacolon related to C. difficile colitis

Image: “Toxic megacolon” by University of Pittsburgh Department of Pathology. License: CC BY 3.0

Acute colonic pseudo-obstruction

  • Initial management (for stable patients without peritonitis in 1st 48–72 hours and a cecal diameter < 12 cm):
    • Rectal tube for decompression
    • Stop offending medications (opiates, anticholinergics, calcium channel blockers).
    • Treat underlying illness.
    • Follow with serial physical exams and X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays every 12–24 hours.
  • Pharmacologic interventions:
    • Indications:
      • No improvement in 72 hours
      • Cecal diameter > 12 cm
    • IV neostigmine (acetylcholinesterase inhibitor):
      • Bolus dosing or continuous infusion
      • 89% respond to a single dose.
      • Patients need to be in a monitored setting.
    • Methylnaltrexone: if the obstruction is precipitated by opiates
  • Colonoscopic decompression:
    • Indications:
      • No response to neostigmine
      • Contraindications to neostigmine
    • Has a 3% perforation rate
  • Surgery:
    • Indications: 
      • Failure of non-surgical management
      • Peritonitis (ischemia or perforation)
    • Procedures:
      • Primary anastomosis (stable patients)
      • Total abdominal colectomy with end ileostomy (ischemia or perforation)

Chronic megacolon

  • General management:
    • Supportive treatment as needed (hydration, electrolyte correction)
    • Stop offending medications (opiates, anticholinergics).
    • Nasogastric or rectal tube decompression, if requiring hospitalization
    • Empty the bowel.
      • Manual disimpaction may be required for fecal impaction.
      • Osmotic laxatives Laxatives Laxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient. Laxatives
      • Suppositories
      • Enemas 
    • Strict bowel retraining program
      • Scheduled defecation times
      • Increase physical activity.
      • Consume bulking agents (high fiber).
  • Surgical management:
    • For severe cases that are unresponsive to medical management
    • Hirschsprung’s disease:
      • Definitive therapy
      • Resection of aganglionic segment with primary anastomosis

Differential Diagnosis

  • Mechanical large bowel obstruction Large Bowel Obstruction Large bowel obstruction is an interruption in the normal flow of intestinal contents through the colon and rectum. This obstruction may be mechanical (due to the actual physical occlusion of the lumen) or functional (due to a loss of normal peristalsis, also known as pseudo-obstruction). Malignancy and volvulus are the most common causes of mechanical large bowel obstruction. Large Bowel Obstruction: interruption in the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of intraluminal contents caused by intrinsic or extrinsic compression of the colonic lumen. Common etiologies include colorectal cancer Colorectal cancer Colorectal cancer (CRC) is the 2nd leading cause of cancer-related deaths in the United States. Colorectal cancer is a heterogeneous disease that arises from genetic and epigenetic abnormalities, with influence from environmental factors. Colorectal Cancer and volvulus Volvulus A volvulus is the twisting or axial rotation of a portion of the bowel around its mesentery. The most common site of volvulus in adults is the colon; most frequently the sigmoid volvulus. Patients typically present with symptoms of bowel obstruction such as abdominal pain, distension, vomiting, and constipation/obstipation. Volvulus. Patients present with abdominal distention, obstipation, nausea, and vomiting. The diagnosis is established with imaging. Management includes bowel rest, decompression, and surgery.
  • Small bowel obstruction Small Bowel Obstruction Small bowel obstruction (SBO) is an interruption of the flow of the intraluminal contents through the small intestine, and is classified as mechanical (due to physical blockage) or functional (due to disruption of normal motility). The most common cause of SBO in the Western countries is post-surgical adhesions. Small bowel obstruction typically presents with nausea, vomiting, abdominal pain, distention, constipation, and/or obstipation. Small Bowel Obstruction: an interruption of intraluminal contents through the small bowel due to a mechanical or functional problem. Patients present with abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, distention, nausea, and vomiting. Imaging will show involvement of the small bowel, although the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix may also be distended in functional obstruction. Most cases will resolve with supportive care.
  • Appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the appendix. Early appendicitis can present with diffuse colicky pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, but pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and tenderness eventually localize to the right lower quadrant. Diagnosis is established by CT scan. Treatment includes antibiotics and surgery.
  • Diverticulitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the colonic diverticula. Patients present with crampy lower abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, and may have constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation. Diverticulitis is frequently associated with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and leukocytosis. A CT scan shows the characteristic inflammatory findings. Treatment includes bowel rest, antibiotics, and occasionally surgery.

References

  1. Sheth S.G., Lamont T. (2020). Toxic megacolon. Retrieved 13 December 2020, from https://www.uptodate.com/contents/toxic-megacolon
  2. Wald A. (2020). Etiology and evaluation of chronic constipation in adults. Retrieved 13 December 2020, from https://www.uptodate.com/contents/etiology-and-evaluation-of-chronic-constipation-in-adults 
  3. Wesson D.E., Esperanza Lopez M. (2019). Congenital aganglionic megacolon (Hirschsprung disease). Retrieved 13 December 2020, from https://www.uptodate.com/contents/congenital-aganglionic-megacolon-hirschsprung-disease
  4. Cochran, W.J. (2019). Hirschsprung disease. [online] MSD Manual Professional Version. Retrieved December 19, 2020, from https://www.msdmanuals.com/professional/pediatrics/congenital-gastrointestinal-anomalies/hirschsprung-disease
  5. Manuel, D. and Piper, M.H. (2019). Chronic megacolon. In Anand, B.S. (Ed.), Medscape. Retrieved December 19, 2020, from https://emedicine.medscape.com/article/180955-overview
  6. Lin, B., and Wu, G.Y. (2018). Toxic megacolon. In Cagir, B. (Ed.), Medscape. Retrieved December 19, 2020, from https://emedicine.medscape.com/article/181054-overview

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