Colonic Infections: Etiology, Clinical Features

Common Bacterial Causes of Colonic Infections

1. Campylobacter jejuni

• Spiral, microaerophilic gram-negative rod.
• Typically acquired from improperly prepared chicken or beef.
• Present with watery diarrhea, fever, and abdominal pain.
• It affects the cecum and terminal ileum, mimicking appendicitis or Crohn's disease.

2. Yersinia enterocolitica

• Gram-negative coccus.
• Exposure to contaminated food or water.
• Manifests with abdominal pain and bloody diarrhea, mimicking appendicitis or Crohn's disease.

3. Shigella

• Gram-negative facultative anaerobic bacterium.
• Common cause of dysentery in developing countries.
• Affects the rectum and sigmoid colon.

4. Salmonella Typhi or Salmonella Enterica Serotypes Paratyphi

• Gram-negative facultative anaerobic bacilli.
• Associated with enteric fever.
• Patients develop high-grade fever with or without diarrhea, abdominal pain, cramping, and vomiting.
• History of travel to endemic areas or consumption of foods prepared by travelers from endemic areas.

Cytomegalovirus (CMV) Colitis in Immunocompromised Patients

Etiology of Cytomegalovirus (CMV) Colitis

Important etiology for acute diarrhea and colitis in immunocompromised patients. It is commonly seen in HIV-positive patients, transplant recipients (receiving immunosuppressive agents), patients with inflammatory bowel disease (due to steroid use), and those receiving chemotherapy.

Clinical Features of Cytomegalovirus (CMV) Colitis

• Watery or bloody diarrhea.
• Fever.
• Abdominal pain.

Diagnosis of Cytomegalovirus (CMV) Colitis

• Serology: Serological tests or determination of viral load in the blood.
• Endoscopy: Patchy mucosal erythema in the colon.
• Biopsy: Presence of inclusion bodies, which are pathognomonic for CMV infection.

Complications of Cytomegalovirus (CMV) Colitis

• Sepsis.
• Toxic megacolon.
• Colonic perforation.

Treatment of Cytomegalovirus (CMV) Colitis

• Supportive Treatment: Mainly supportive, with the addition of ganciclovir.
• Surgery: Required in severe complicated cases.

Ischemic Colitis

Ischemic colitis is the most common form of gastrointestinal ischemia, varying in severity from mild self-limiting disease to life-threatening colonic ischemia.

Factors and Risks Associated with Ischemic Colitis

1. Demographic and Comorbid Factors: Ischemic colitis is more prevalent in elderly individuals, particularly elderly females and those with multiple comorbidities.
2. Low Flow States: Conditions such as septic shock, congestive heart failure, hemorrhagic shock, or hypotension lead to low flow states, compromising bowel perfusion and contributing to ischemic colitis.
3. Atherosclerosis-related Conditions: Patients with ischemic heart disease, cerebrovascular diseases, or peripheral vascular diseases, which lead to compromised blood flow, are at increased risk of ischemic colitis.
4. Gastrointestinal Conditions: Constipation, diarrhea, and irritable bowel syndrome can increase intra-luminal pressure or fluid loss, impacting bowel perfusion and predisposing individuals to ischemic colitis.
5. Surgical and Invasive Interventions: Abdominal surgeries, aortic reconstructive surgeries, endovascular abdominal manipulations, chemoembolization, and even post-colonoscopy insufflation can lead to ischemic colitis due to altered blood flow or increased colon pressure.
6. Cardiovascular and Pulmonary Diseases: Conditions such as COPD, atrial fibrillation, or hypertension may reduce cardiac output, further compromising bowel perfusion.
7. Metabolic and Rheumatoid Disorders: Diabetes mellitus, dyslipidemia, obesity, or rheumatoid arthritis can increase the risk of atherosclerosis, contributing to ischemic colitis.
8. Miscellaneous Conditions: Hypercoagulable states, sickle cell disease, or activities like long-distance running pose an increased risk of thrombogenesis and subsequent embolic occlusion, leading to ischemic colitis.

Drugs Associated with Ischemic Colitis

1. Constipation-Inducing Drugs: Opioids, antipsychotics, and other medications causing constipation can reduce blood flow to the colon due to increased intraluminal pressure.
2. Illicit Drugs: Cocaine and methamphetamine can induce vasoconstriction, hypercoagulation, or direct endothelial injury, leading to ischemic colitis.
3. Immunomodulatory Drugs: Agents like TNF-alpha inhibitors, interferon-alpha, or interferon-beta can induce thrombogenesis, increasing the risk of ischemic colitis.
4. Chemotherapy Agents: Drugs such as Taxanes and OCPs can induce a hypercoagulable state, predisposing individuals to ischemic colitis.
5. Decongestants and Serotonergic Drugs: The usage of decongestants like pseudoephedrine or serotonergic drugs like alosetron and sumatriptan can also increase the risk of ischemic colitis.

Clinical Features of Ischaemic Colitis

Partial Thickness Ischemia

• Patients with partial thickness ischemia may present with nonspecific signs and symptoms.
• Initial presentation often includes severe abdominal pain preceding bleeding.
• Patients commonly complain of severe abdominal pain, cramping, tenesmus, and bloody diarrhea or hematochezia.
• Pain precedes bleeding, with minor bleeding being the most common presentation, rarely requiring blood transfusion.
• Up to 50% of patients may experience a combination of these symptoms.

Full Thickness Ischemia

• Patients with full-thickness ischemia may appear sicker and present with fever, leukocytosis, acidosis, or peritonitis.
• Full-thickness ischemia often necessitates surgery and is associated with poor prognosis.

Laboratory Investigations of Ischaemic Colitis

• Laboratory findings indicating severe disease include leukocytosis, elevated blood urea nitrogen, increased LDH, decreased hemoglobin, decreased albumin, and acidosis with low bicarbonate and increased lactate levels.

Imaging Findings of Ischaemic Colitis

1. Plain Films
   Plain films may show bowel distension and thumbprinting, indicative of submucosal edema. Thumbprinting represents rounded opacities along the sides of gas-filled bowel loops.
2. Barium Enema
   Thumbprinting can also be observed on barium enema studies, indicating submucosal edema, although it is a nonspecific sign and can be seen in other colonic inflammatory conditions.
3. Water-Soluble Contrast Enema
   Water-soluble contrast enema is obsolete for diagnosing ischemic colitis but can be useful for detecting ischemic strictures that may develop in some patients post-ischemic colitis.
4. Computed Tomography Angiography (CTA):

• CTA with both IV and oral contrast is the primary non-invasive modality for initial diagnosis.
• Determines location, assesses severity, identifies complications, and excludes other diseases.
• Segmental bowel thickening, pericolonic fat stranding, and thumbprinting, although nonspecific, are suggestive of ischemic colitis.

Indications for Immediate Surgical Intervention in Ischemic Colitis

Presence of pneumatosis intestinalis, gas in the portal venous system, or absence of large bowel enhancement on CT suggest severe transmural disease, necessitating immediate surgical intervention.

Endoscopic Findings  of Ischaemic Colitis

• Edematous, friable mucosa, erythema, petechial hemorrhages, and mucosal ulcerations are characteristic findings of ischemic colitis.
• The single strip sign, a single linear ulcer along the longitudinal axis of the colon, is considered specific for ischemic colitis but is rare.
• Differentiating Ischemia vs. Inflammatory Bowel Disease: Segmental distribution, abrupt transition between injured and non-injured mucosa, and sparing of the rectum support ischemia.
• Diagnostic endoscopy cannot distinguish between partial and full-thickness ischemia.

Treatment of Ischaemic Colitis

• Conservative Management
  • Up to 80% of patients respond to conservative management, showing significant improvement within days.
  • Mainstay:
    • Bowel rest
    • IV fluids
    • Broad-spectrum antibiotics
    • Nasogastric tube insertion if ileus is present
• Aggressive Fluid Resuscitation: Patients with low-flow states like hypotension should undergo aggressive fluid resuscitation.
• Optimal Treatment of Associated Conditions: Aggressively treat underlying conditions such as heart failure or sepsis to address the root cause.
• Antibiotic Therapy
• Colonic ischemia leads to failure of the intestinal epithelial barrier, causing bacterial translocation and subsequent sepsis.
• Broad-spectrum antibiotics covering both aerobes and anaerobes are administered.
• Avoidance of Cathartics: Cathartics are contraindicated as they may cause colonic perforation.
• Avoidance of Glucocorticoids
  • Glucocorticoids are avoided except in patients with pre-existing disorders like lupus or rheumatoid arthritis due to the increased risk of sepsis.

Surgical Intervention for Chronic Colitis

• Surgical resection of the involved segment is often necessary due to the high risk of complications associated with chronic colitis

Emergency Surgical Exploration for Colonic Ischemia

• Patients presenting with colonic ischemia and signs of transmural ischemia or perforation require emergency surgical exploration.
• Free peritoneal air or portal venous gas indicate unstable patients and necessitate emergency intervention.

Risk Factors for Perioperative Mortality of Colonic Ischemia

• Factors increasing the risk of perioperative mortality after colectomy in ischemic colitis patients include:
  • Elderly age
  • Poor functional status
  • Multiple comorbidities
  • Preoperative septic shock
  • Requirement of blood transfusion
  • Acute renal failure
  • Delay from hospital admission to surgery

Also Read: Mesentery and Omentum: Surgical POV

Frequently Asked Questions:

Q: What is the most common type of gastrointestinal ischemia?

Answer: Ischemic colitis is the most common form of gastrointestinal ischemia.

Q: What is a “thumbprinting sign”?

Answer: A thumbprint sign or thumbprinting sign is a non-specific sign. It shows the presence of submucosal edema.

Q: What is colitis?

Answer: Colitis is the inflammation of the colon.

Hope you found this blog helpful for your GIT, Hepatobiliary and Pancreatic Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.