Diverticulitis overview

# Overview
Diverticulitis is a common disease of the digestive tract that affects the colon. Diverticulitis develops from diverticulosis, which involves the formation of pouches (diverticula) on the outside of the colon. Diverticulitis results when one of these diverticula becomes inflamed or infected. The colon can become infected with pieces of food stuck inside, leading to abdominal pain. Diverticulitis can be classified into asymptomatic, symptomatic, complicated, uncomplicated, acute and recurrent. The prevalence of diverticulitis is 20,000 individuals at age 40 and 60,000 at age 60. The highest incidence is in patients between 18 to 44 years old. Men and women are equally affected by diverticulitis between 50-70. Risk factors of diverticulitis are multiple diverticula and intraperitoneal abscess.  Diverticulitis can cause many complications as abscess, perforation, peritonitis, and fistula formation. Symptoms of diverticulitis include left lower abdominal pain, fever, cramps, and constipation. Common physical examination findings include tachycardia, fever, abdominal tenderness, guarding and rebound tenderness, and presence of a palpable mass. The mainstay of therapy for acute diverticulitis is usually conservative medical management, including bowel rest, intravenous fluid resuscitation, and broad-spectrum antimicrobial therapy that covers anaerobic bacteria and gram-negative rods.

# Historical Perspective
Diverticulitis was first described by Dr. Lavater in the 1700s. In the 18th century, Dr. Littre was the first person to describe the diverticular disease. Dr. Meckel gave a full description of the diverticulum in 1812.

# Classification
Diverticulitis may be classified according to the 2014 guidelines by the German Societies of Gastroenterology (DGVS) and of Visceral Surgery (DGAV). They unanimously agreed on a classification system (Classification of Diverticular Disease (CDD)), that takes practical algorithms (symptomatic, asymptomatic, complicated, uncomplicated, acute, recurrent), ongoing surgical aspects (purulent versus fecal peritonitis), and contemporary diagnostic standards in clinical practice into account. As a result, this classification comprises the entire spectrum of diverticular disease.

# Pathophysiology
Diverticula are protrusions of the mucosal and serosal intestinal layers and occur more often on the left side than the right side. Diverticulitis is the inflammation of these protrusions. The first steps in the pathogenesis of diverticulitis are an increase in intraluminal pressure, change in intestinal motility, and bacterial colonization. The inflammation is caused by histamine, tumor necrosis factor, and metalloproteinases, which have been found in diverticulitis patients' tissue biopsies. Obstruction of the diverticula leads to bacterial colonization, which causes inflammation.

# Causes
Common causes of diverticulitis include diverticulosis, a low-fiber diet, constipation, abdominal distension, and Meckel's diverticulum.

# Differentiating Diverticulitis from Other Diseases
Diverticulitis must be differentiated from other diseases that cause lower abdominal pain and fever, such as appendicitis, inflammatory bowel disease, colon cancer, cystitis, and endometritis. Diverticulitis must be also differentiated from diseases causing peritonitis.

# Epidemiology and Demographics
The prevalence of diverticulitis is 20,000 individuals at age 40 and 60,000 at age 60. The highest incidence is in patients between 18 to 44 years old. Men and women are equally affected by diverticulitis between 50-70, but men above 70 are more commonly affected than women. The prevalence of diverticulitis has increased in developed countries. In the United States, approximately 312,000 cases are admitted to the hospitals. In Japan, more cases of right side diverticulitis have been reported than cases of left side diverticulitis.

# Risk Factors
The most potent risk factors for disease recurrence include multiple diverticula, intraperitoneal abscess, family history of diverticulitis, and having a large portion of the colon involved in the disease.

# Screening
There is insufficient evidence to recommend routine screening for diverticulitis.

# Natural History, Complications, and Prognosis
Diverticulitis natural history is not well understood. Diverticulitis can cause many complications that can be fatal in some cases. These complications include abscess, perforation, peritonitis, and fistula formation. Prognosis of diverticulitis is excellent and conservative treatment is successful in 70 to 100 percent of patients.

# Diagnosis

## History and Symptoms
The most common symptoms of diverticulitis include left lower abdominal pain, fever, cramps, and constipation. A positive history of change in bowel habits is suggestive of diverticulitis. Less common symptoms include flatulence, nausea, and vomiting.

## Physical Examination
Patients with diverticulitis usually appear toxic due to pain. Common physical examination findings include tachycardia, fever, abdominal tenderness, guarding and rebound tenderness, and presence of a palpable mass. Diverticulitis diagnosis depends on taking a proper history and performing a physical examination. The known diagnostic criteria for diverticulitis include abdominal tenderness, especially in the left lower quadrant, and leukocytosis. CT scan findings help in disease confirmation.

## Laboratory Findings
Diverticulitis diagnosis starts by taking history precisely and performing a physical examination. Lab tests are important in excluding other causes of abdominal pain and any other gastrointestinal disease. These lab tests include CBC, CRP, urinalysis, and liver tests. Imaging procedures including CT scan and colonoscopy are important measures in diagnosing diverticulitis.

## CT scan
Abdominal CT scan is helpful in the diagnosis of diverticulitis. CT is not only important in the diagnosis of diverticulitis but is also necessary to exclude the possibility of cancer in patients. CT may also identify patients with complicated diverticulitis, such as those with an associated abscess. CT also allows for radiologically guided drainage of associated abscesses, possibly sparing a patient from immediate surgical intervention.

## MRI
On abdominal MRI, diverticulitis is characterized by thickening of the colon wall, the presence of the diverticula, and exudates from the colon. It may also show the presence of multiple abscesses. MRI is a good imaging modality that can be used in the diagnosis of diverticulitis since it has the advantage that it doesn't involve exposure to radiation and rules out other abdominal causes of acute abdomen. However, MRI is not the best diagnostic procedure for diverticulitis; CT scan is preferred.

## Ultrasound
On abdominal ultrasonography, diverticulitis is characterized by abscess formation, gas bubbles, the presence of diverticula, and thickening of the colon segments. Extra diverticular exudates and fluids can be also observed.

## X-ray
On abdominal X-ray, diverticulitis is characterized by multiple air and fluid levels if there is an intestinal perforation. Chest X-ray should be done in patients with diverticulitis to investigate for pneumoperitoneum, which is a harbinger of a critical illness and will lead to a change in the management plan for the case. X-ray can be used if CT is not available and in uncomplicated cases.

## Other imaging findings
There are no other specific imaging findings for diverticulitis. Other studies such as barium enema and colonoscopy are contraindicated in the acute phase of diverticulitis due to the risk of perforation.

## Other diagnostic studies
There are no other specific diagnostic studies for diverticulitis. Other studies such as barium enema and colonoscopy are contraindicated in the acute phase of diverticulitis due to the risk of perforation.

# Treatment

## Medical Therapy
The mainstay of therapy for acute diverticulitis is usually conservative medical management, including bowel rest, intravenous fluid resuscitation, and broad-spectrum antimicrobial therapy that covers anaerobic bacteria and gram-negative rods. Patients who have recurring acute attacks or who develop diverticulitis-associated complications, such as peritonitis, abscess, or fistula, require surgery either immediately or on an elective basis.

## Surgery
Surgery is not the first-line treatment option for patients with diverticulitis. Emergency or urgent surgery is usually reserved for patients complicated with peritonitis, who are unresponsive to treatment, who have intestinal obstruction, or with abscess formation. Elective surgery may be performed and it depends on many factors like the age of the patient, severity score, and persistence of symptoms.

## Prevention
Primary prevention of diverticulitis follows the prevention of constipation by using osmotic agents like lactulose, polyethylene glycol, or magnesium salts. A high fiber diet should be given until constipation improves. Using laxatives and drinking plenty of fluids daily will be helpful.