Diverticular Disease: Diverticulitis vs Diverticulosis
Diverticular Disease: This lecture will review diverticulitis vs diverticulosis of the colon including their definitions, pain location, symptoms, causes, treatment, pathophysiology, diet, and more!
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Guest Author: Charlotte Watson
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Diverticular Disease
This lecture will discuss diverticular disease, including diverticulitis vs diverticulosis and their:
Definitions
Symptoms
Causes
Examination Findings
Differential Diagnosis
Risk Factors
Pathophysiology
Diagnosis
Treatment
Possible Complications
This lecture will also review the anatomy of the colon.
In order to gain a full understanding of the conditions, it is recommended you read the lecture in chronological order.
Diverticular Disease: Diverticulitis vs diverticulosis of the colon including definitions, symptoms, pain location, diet, pathophysiology, treatment, and more!
Diverticular Disease: Definitions
The terms diverticulum, diverticula, diverticular disease, diverticulosis, and diverticulitis can cause confusion due to their similarities.
So let’s first define them below!
Diverticulum
A diverticulum is a small, sac-like outpouching along the wall of a hollow structure.
The term diverticulum typically refers to an outpouching along the wall of the gastrointestinal tract, most commonly the colon (large intestine).
Therefore, you can think of a diverticulum as a single bulge of tissue ballooning out of the colon wall.
More specifically, the mucosa and submucosa lining of the colon protrude through the outer colon wall to create a sac-like outpouching.
Diverticula
Diverticula is the plural of diverticulum and is used to describe multiple outpouchings.
Diverticular Disease
Diverticular disease is an umbrella term for the conditions involving the presence or formation of diverticula in the colon.
Examples of diverticular disease include diverticulosis, diverticulitis, and diverticular hemorrhage.
Study Note – Some textbooks may use the term diverticular disease to describe symptomatic diverticula only. However, the umbrella definition provided above is more widely accepted and will be used throughout this lecture.
Diverticulosis
Diverticulosis is simply the presence of diverticula in the colon, usually without any related complications or symptoms.
Diverticulosis carries a risk of progressing to other forms of diverticular disease, such as diverticulitis, diverticular hemorrhage, etc.
The different manifestations and complications of diverticular disease will be discussed in more detail below.
Diverticulitis
Diverticulitis is inflammation of a diverticulum.
The definition is easy to remember as it can be identified by the suffix “-itis”, which means inflammation.
Diverticulitis can be categorized into simple (uncomplicated) vs complicated based on the presence or absence of complications - more on this later!
Diverticular Hemorrhage
A diverticular bleed or hemorrhage occurs when a diverticulum bleeds.
This typically occurs when a small blood vessel within the diverticulum ruptures and bleeds - more on this later!
Diverticular Disease Definitions: Diverticulosis vs diverticulitis vs diverticular hemorrhage definitions - including simple vs complicated diverticulitis
Summary of Definitions
Diverticulum: A small, sac-like outpouching along the wall of a hollow structure, typically the colon (large intestine), that protrudes through the outer wall
Diverticula: Plural of diverticulum; Multiple outpouchings
Diverticular Disease: Umbrella term for conditions involving the formation or presence of diverticula
Diverticulosis: The presence of diverticula (typically in the colon)
Diverticulitis: Inflammation of a diverticulum
Diverticular Hemorrhage: Diverticular bleeding
Diverticular Disease: Definitions of diverticulum vs diverticula vs diverticular disease vs diverticulosis vs diverticulitis
Anatomy of the Colon
Anatomy can be an overwhelming topic, so let’s focus on the basics and background features required to understand diverticular disease.
The terms colon, large bowel, and large intestine can be used interchangeably to describe this organ.
Parts of the Colon
The colon stretches from the cecum to the rectum in 4 parts:
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
The cecum is a pouch that forms the first part of the colon and connects the small intestine and large intestine.
The rectum forms the last part of the colon and connects to the anus.
The colon sits around the periphery of the abdominal organs.
On average the colon is 1.5m (5 feet) long.
The ascending and descending colon are retroperitoneal, meaning they are found in a space between the peritoneum of the abdomen and the posterior abdominal wall.
The rectum is also retroperitoneal.
The transverse and sigmoid colon are intraperitoneal structures, and are attached to the posterior abdominal wall by mesenteries; the transverse and sigmoid mesocolon respectively.
The cecum is also intraperitoneal.
Anatomy of the Colon: The colon or large intestine consists of the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
Embryology of the Colon
It may also be helpful to remind yourself that the colon embryologically is both a midgut and hindgut structure.
The cecum, ascending colon, and proximal 2/3rd of the transverse colon develop from the midgut.
The distal 1/3rd of the transverse colon, the descending colon, the sigmoid colon, and the rectum are all derived from the hindgut.
Embryology of the Colon: Review of the large intestine structures that develop from the midgut and hindgut, along with their retroperitoneal or intraperitoneal location
Walls of the Colon
The walls of the bowel consist of 4 layers listed below (outermost to innermost):
Serosa (outermost layer)
Muscular Layers
Outer Longitudinal
Inner Circular
Submucosa
Mucosa (inner lining)
The outer layer of longitudinal muscle forms 3 long strips along the colon, called taeniae coli, which contract to produce “sacks” of the colon, called haustra.
It is important to note that haustra are not diverticula.
The colon is also decorated by small fat sacs of serosa called epiploic appendages.
These are all hallmarks of the large bowel.
Layers of the Colon Wall: Mucosa, submucosa, inner circular muscle, outer longitudinal muscle, serosa (innermost to outermost)
Anatomy of the Colon: Labeled diagram of taenia coli, haustra, and epiploic appendage
Colon Blood Supply
The blood supply to the colon is split.
Branches of the superior mesenteric artery (SMA) supply the ascending colon and most of the transverse colon.
These branches include the middle colic, right colic and ileocolic arteries.
Branches of the inferior mesenteric artery (IMA) supply the descending and sigmoid colon.
These branches include the left colic and sigmoid arteries.
There is an anastomosis of the terminal branches of the SMA and IMA at the left colic flexure, called the marginal artery, where both the SMA and IMA supply the colon.
The rectum is supplied by 3 main arteries: Superior, Middle, and Inferior rectal arteries.
The superior rectal artery arises from the IMA.
The middle rectal artery arises from the internal iliac artery.
The inferior rectal artery arises from the internal iliac branches of the internal pudendal arteries.
Blood Supply of the Colon: Ascending, transverse, descending, sigmoid, and rectum blood supply review including the superior mesenteric artery (SMA), inferior mesenteric artery (IMA), ileocolic, right colic, middle colic, left colic, sigmoid, and rectal arteries.
Function of the Colon
The function of the colon is to absorb water and electrolytes from the small intestine output, and convert it into solid feces.
The majority of the large intestine water and electrolyte absorption occurs at the ascending and transverse colon.
However, it’s important to remember that the majority (80%) of water has already been absorbed by the time it reaches the large intestine – the majority of this occurring in the small intestine.
Function of the Colon: The large intestine absorbs final amounts of water and electrolytes from solid waste to form feces.
Pathophysiology of Diverticula
Let’s review the location and pathophysiology of diverticula.
Location
Diverticula predominantly occur in the left side of the colon, particularly the sigmoid and descending colon.
Other areas may be affected as well, although this is less common.
Diverticular Location: A diverticulum is most commonly located in the descending colon or sigmoid colon
Pathophysiology
A diverticulum occurs where the mucosa and submucosa of the bowel wall herniate through points of weakness in the circular muscular layer of the colon.
These areas of weakness are located at points where small branches of blood vessels (the vasa recta) horizontally penetrate through the colonic muscle wall to supply the bowel with blood.
The pathophysiology as to why diverticula form is not fully understood.
However, it is believed that increased colonic pressure causes weak spots in the colon to bulge out.
The increased pressure generated by muscle contractions in the colon causes the mucosa and submucosa layers to herniate through the path of small blood vessels within the colon wall.
This creates a sac-like outpouching called a diverticulum.
Diverticula do not continue past the sigmoid colon into the rectum.
Although the exact pathology of why the rectum is not involved is not well understood, researchers suggest that it could be a result of longitudinal muscle completely surrounding the rectum, or due to the lower peristaltic activity of the rectum compared to the colon.
Diverticular Disease Causes and Pathophysiology: Increased pressure in the colon can cause the mucosa and submucosa layers to balloon out, creating a sac-like outpouching called a diverticulum
Causes and Risk Factors
As previously mentioned, the exact cause of diverticular disease remains unknown.
One theory is that increased pressure in the colon (such as from straining or constipation) can cause weak spots in the colon to balloon out (see previous section).
This creates sac-like outpouchings called diverticula.
There are also potential risk factors for developing diverticular disease.
The risk factors of diverticular disease include:
Increasing Age
A Low-Fiber Diet
Obesity (clinically defined as a BMI over 30)
Lack of Exercise
Genetic Predisposition
Smoking
Alcohol Use
Certain Medications (steroids, NSAIDS)
A low-fiber diet can lead to hard stools and constipation, which can increase the pressure in the colon thereby increasing the risk of diverticular formation as described above.
Diverticular Disease: Risk factors such as a low-fiber diet can cause diverticulosis or the formation of diverticulum, among other risk factors.
Diverticulosis
As previously mentioned, diverticular disease is the umbrella term for conditions involving the presence of diverticula.
The first of these conditions we will discuss is diverticulosis, which is simply the presence of diverticula.
Let’s review diverticulosis below.
Symptoms
Diverticulosis does not normally present with symptoms.
Remember this form of diverticular disease is usually asymptomatic, unless it progresses to another form of diverticular disease or complications develop - More on this later!
If minor symptoms occur with diverticulosis, they typically include non-specific abdominal issues such as bloating, constipation, diarrhea, and abdominal pain (typically left-sided).
Diverticulosis Symptoms: Diverticulosis is typically asymptomatic (no symptoms) unless it progresses to another diverticular disease or complications develop
On Examination
An asymptomatic patient may have no findings on physical exam, with the normality of their abdomen being documented in the notes as “SNT” – meaning that the abdomen is soft and non-tender.
Patients with minor symptoms associated with their diverticulosis (again diverticulosis is typically asymptomatic) may experience slight tenderness to palpation of their abdomen.
In particular, they may experience pain to palpation in the left iliac fossa (left lower region of the abdomen), as well as rebound tenderness and guarding.
Diverticulosis: Physical exam findings are usually normal given diverticulosis is typically asymptomatic, but may include abdominal pain to palpation, rebound tenderness, and guarding
Diagnosis and Investigation
Diverticulosis may be discovered incidentally, such as from imaging for another medical issue, or routine colonoscopy for colorectal cancer screening, etc.
Diverticulosis: Diagnosis is typically made incidentally when testing for something else as diverticulosis is usually asymptomatic
Treatment
Given the lack of symptoms, diverticulosis is not treated unless there is progression of disease, such as diverticulitis or diverticular hemorrhage (see below), or if complications develop (see below).
If diverticulosis is incidentally diagnosed, then lifestyle modifications may be recommended including a high-fiber diet, smoking/alcohol cessation, exercise, weight loss, etc.
Diverticulosis: Treatment is typically not necessary given the asymptomatic presentation but may include lifestyle modifications such as diet, exercise, smoking/alcohol cessation, etc.
Diverticulitis
As discussed above, diverticulosis is the presence of diverticula.
Diverticula can progress to other forms of diverticular disease and/or complications may develop.
Occasionally diverticula become inflamed, a condition known as diverticulitis.
Remember, diverticulitis is inflammation of a diverticulum/diverticula.
Diverticulitis is another example of a diverticular disease.
Let’s review diverticulitis below.
Pathophysiology
The pathophysiology of diverticulitis is not yet understood.
One theory suggests that it is caused by stool entering a diverticulum and becoming entrapped.
The fecal stasis creates a build-up of pressure and bacteria, which can lead to inflammation along with possible infection, subsequent ischemia, and further risk of perforation.
However, other theories suggest that it may be caused by the gastrointestinal tract existing in a state of chronic inflammation, potentially as a result of obesity, cardiovascular disease or diabetes.
Diverticulitis: The cause and pathophysiology is thought to be from fecal obstruction that leads to inflammation of the diverticulum
Symptoms
An acute diverticulitis patient may present with infection-related symptoms of fever, tachycardia (increased heart rate), nausea, vomiting, fatigue, as well as abdominal symptoms.
Abdominal symptoms may include bloating, constipation, diarrhea, and left lower quadrant abdominal pain which may be constant or a colicky pattern (pain appears to come and go in waves).
The left lower quadrant abdominal pain may be in the left iliac fossa.
Some patients report the pain is exacerbated by eating, but may be relieved by defecation or passing wind (flatus).
There may also be blood in the stool from rectal bleeding.
Diverticulitis: Symptoms include left lower abdominal pain, nausea, vomiting, bloating, constipation, diarrhea, bloody stools, fever, etc.
On Examination
The examination findings will be consistent with reported symptoms; pyrexia (raised body temperature/fever), tachycardia (increased heart rate), and left lower quadrant abdominal tenderness and/or guarding.
There may be tenderness in the left iliac fossa on palpation, as well as rebound tenderness and guarding.
Blood in the stool may be identified with a positive fecal occult blood test (FOBT).
It is important to be aware that some patients may instead present with right lower quadrant pain.
This presentation is rare and seen most in patient’s of Asian heritage.
In some cases, a mass may be felt on palpation of the abdomen.
If there are absent bowel sounds on auscultation of the patient’s abdomen, then this may indicate perforation of the inflamed diverticula which would require urgent medical treatment.
Diverticulitis: Physical exam findings may include left lower quadrant pain to palpation, bloody stools with positive fecal occult blood test (FOBT), fever, tachycardia, etc.
Differential Diagnosis
Given the above symptoms, other conditions to consider include inflammatory bowel disease (Crohn’s disease and ulcerative colitis), irritable bowel syndrome, ischemic colitis, mesenteric ischemia, gastroenteritis, infective colitis, malignancy, among others.
All of these conditions will need to be excluded and considered during the investigation phase.
Diagnosis and Investigation
When a patient presents with the above symptoms, vital signs will be taken and a complete history and physical examination will be performed.
Next, the patient will likely have routine blood tests which may include a complete blood count (CBC), chemistry (urea and electrolytes - U&Es), liver function tests (LFTs), lipase, lactate, blood cultures, c-reactive protein (CRP), fecal calprotectin, etc.
**Blood tests order will vary depending on the facility, protocols, and the patient’s presentation.
Diverticulitis may cause the following blood test results:
Diverticulitis, being an inflammatory process with a potential for infection, may cause elevated inflammatory markers such as CRP and leukocytes.
U&Es will be vital in patients with vomiting and diarrhea to ensure the patient has the correct electrolyte balance. It is also useful for assessing renal function.
Liver function tests may help exclude hepatic and biliary causes of abdominal pain
Lipase may help exclude pancreatic causes of abdominal pain
Lactate can be useful if there is concern for ischemia, sepsis/infection, etc.
Blood cultures may also be useful if there is concern for bacteremia/sepsis, etc.
A urine sample may be sent to assess for a possible urinary tract infection (UTI) cause of the symptoms.
Stool studies may also be sent.
Important: A pregnancy test must be performed on a female of childbearing age presenting with abdominal pain. This is also important to prevent possible harm from ionizing imaging techniques to an unknown pregnancy.
A flexible sigmoidoscopy may be used to look for diverticula, although other imaging modalities such as a contrast CT scan can also be used to visualize the diverticula.
These modalities will also be used to exclude other causes of the patient’s symptoms such as malignancy.
A contrast CT with positive findings for diverticulosis will show fluid-filled diverticula with thickened colonic walls.
Diverticulitis: Diagnosis includes blood tests, imaging (CT scan), colonoscopy, stool studies, etc.
Classification
Acute diverticulitis can be classified as simple (uncomplicated) or complicated.
Simple diverticulitis refers to localized inflammation without associated complications.
Simple diverticulitis may have milder symptoms than complicated, with milder pain and some thickening of the diverticula wall on CT.
Simple diverticulitis typically responds to medical treatment without surgery.
Complicated diverticulitis refers to diverticulitis associated with complications and usually requires surgery or more immediate management.
Complications associated with diverticulitis include abscess, perforation, fistula, obstruction, sepsis, peritonitis, hemorrhage, etc.
Diverticulitis Classification: Acute diverticulitis can be classified as simple or complicated depending on the presence of absence of complications
Treatment
Typical treatment is with oral antibiotics, or IV antibiotics in more severe presentations.
The type of antibiotic will depend on local guidelines.
Fluid resuscitation with IV fluids may be required to treat and/or prevent dehydration, as well as in the management of sepsis if applicable.
Analgesia may also be required for symptomatic pain relief.
Patients with conservative-type management will be advised to avoid NSAID use, as it increases the risk of diverticular hemorrhage.
Patients with uncomplicated diverticulitis may be able to be treated outpatient if stable, tolerating feeds, etc.
Patients with complicated diverticulitis may require a hospital admission and inpatient treatment.
Management will ultimately depend on the complication present.
Examples include percutaneous drainage of abscesses or surgery.
Removal of the affected bowel may be required in extreme situations, particularly if there is perforation or obstruction.
This operation is known as Hartmann’s procedure, whereby the sigmoid colon is removed and an end colostomy is formed.
All patients will be recommended to make lifestyle adjustments such as a high-fiber diet and sufficient fluid intake.
Bulk-forming laxatives may be effective in treating constipation secondary to diverticular disease.
Diverticulitis: Treatment and management options include antibiotics, pain and symptom control, fluids, lifestyle modifications (high-fiber diet, etc), possible surgery if complications are present, etc.
Diverticular Hemorrhage
As previously mentioned, diverticulosis can progress to other forms of diverticular disease and/or complications may develop.
We discussed how diverticulitis (inflammation of a diverticulum) is one example of that.
Another example is diverticular hemorrhage or bleeding.
Diverticular hemorrhage is another form of diverticular disease.
Patient’s with diverticulosis may develop a diverticular bleed, which is indicated by large-volume painless rectal bleeding.
A diverticular bleed is typically caused by a rupture of the vasa recta in the diverticulum.
Diverticular hemorrhage may also present as an acute complication of diverticulitis.
This requires IV resuscitation and, in some cases, may require hemodynamic stabilization with packed red blood cells.
Diverticular hemorrhage may be self-limiting in some patients but will still require a colonoscopy to identify the source.
Treatment by epinephrine injection or electrocauterization can be delivered to stop ongoing bleeding.
Interestingly, right-sided diverticular disease is much more likely to present acutely as a diverticular bleed than left-sided disease.
Diverticular Bleeding: Diverticular hemorrhage symptoms, causes, pathophysiology, treatment and management.
Complications
The most common conditions of diverticular disease are diverticulosis, diverticulitis, and diverticular hemorrhage.
You can think of diverticulitis (inflammation of the diverticula) and diverticular hemorrhage (diverticular bleeding) as being complications of diverticulosis.
Moreover, there are other complications of diverticular disease that can develop.
These complications are typically associated with diverticulitis and include abscess formation, bowel perforation, peritonitis, sepsis, colonic obstruction and fistula formation.
Diverticular Disease: Complications include diverticulitis (inflammation), hemorrhage (bleeding), abscess formation, fistula formation, obstruction, bowel perforation, peritonitis, sepsis, etc.
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