Diverticula are described as being true or false depending upon the layers involved:

- True diverticula involve all layers of the structure, including muscularis propria and adventitia, such as Meckel's diverticulum.

- False diverticula (also known as "pseudodiverticula") do not involve muscular layers or adventitia. False diverticula, in the GI tract for instance, involve only the submucosa and mucosa.

The majority of people with a Meckel's diverticulum are asymptomatic. An asymptomatic Meckel's diverticulum is called a "silent" Meckel's diverticulum. If symptoms do occur, they typically appear before the age of two years.

The most common presenting symptom is painless rectal bleeding such as melaena-like black offensive stools, followed by intestinal obstruction, volvulus and intussusception. Occasionally, Meckel's diverticulitis may present with all the features of acute appendicitis. Also, severe pain in the epigastric region is experienced by the patient along with bloating in the epigastric and umbilical regions. At times, the symptoms are so painful that they may cause sleepless nights with acute pain felt in the foregut region, specifically in the epigastric and umbilical regions.

In some cases, bleeding occurs without warning and may stop spontaneously. The symptoms can be extremely painful, often mistaken as just stomach pain resulting from not eating or constipation.

Rarely, a Meckel's diverticulum containing ectopic pancreatic tissue can present with abdominal pain and increased serum amylase levels, mimicking acute pancreatitis.

Early symptoms can include periodic abdominal pain, nausea, vomiting (sometimes green in color from bile), pulling legs to the chest area, and intermittent moderate to severe cramping abdominal pain. Pain is intermittent—not because the intussusception temporarily resolves, but because the intussuscepted bowel segment transiently stops contracting. Later signs include rectal bleeding, often with "red currant jelly" stool (stool mixed with blood and mucus), and lethargy. Physical examination may reveal a "sausage-shaped" mass, felt upon palpating the abdomen. Children, or those unable to communicate symptoms verbally, may cry, draw their knees up to their chest, or experience dyspnea (difficult or painful breathing) with paroxysms of pain.

Fever is not a symptom of intussusception. However, intussusception can cause a loop of bowel to become necrotic, secondary to ischemia due to compression to arterial blood supply. This leads to perforation and sepsis, which causes fever.

In rare cases, intussusception may be a complication of Henoch-Schönlein purpura (HSP), an immune-mediated vasculitis disease in children. Such patients who develop intussusception often present with severe abdominal pain in addition to the classic signs and symptoms of HSP.

Diverticula may occur in one of the three areas of the esophagus - the pharyngoesophageal, the midesophageal area or the epiphrenic area of esophagus. Zenker's diverticulum is found three times more frequently in men than in women. It occurs posteriorly through the cricopharyngeal muscle in the midline of the neck. Usually seen in people older than 60 years of age.

- Gastric diverticula - "Although usually asymptomatic, they may cause vague epigastric pain. These lesions may be confused radiologically for gastric ulcers or cancers. Endoscopically, they may be confused for paraesophageal hernias."

- Killian-Jamieson diverticulum

- Meckel's diverticulum: a persistent portion of the omphalomesenteric duct present in 2% of the population

- Rokitansky-Aschoff sinuses: in the gallbladder due to chronic cholecystitis

- Traction esophageal diverticulum: due to scarring from mediastinal or pulmonary tuberculosis

- Urethral diverticulum: congenital in males, post-infectious in females

- Zenker's diverticulum: a diverticulum of the mucosa of the pharynx affecting adults

Most of these pathological types of diverticulum are capable of harboring an enterolith. If the enterolith stays in place, it may cause no problems, but a large enterolith expelled from a diverticulum into the lumen can cause obstruction.

In simple words, when there is excessive pressure within the lower pharynx, the weakest portion of the pharyngeal wall balloons out, forming a diverticulum which may reach several centimetres in diameter.

More precisely, while traction and pulsion mechanisms have long been deemed the main factors promoting development of a Zenker's diverticulum, current consensus considers occlusive mechanisms to be most important: uncoordinated swallowing, impaired relaxation and spasm of the cricopharyngeus muscle lead to an increase in pressure within the distal pharynx, so that its wall herniates through the point of least resistance (known as Killian's triangle, located superior to the cricopharyngeus muscle and inferior to the Thyropharyngeus muscle. Thyropharyngeus and Laryngopharyngeus are the superior and inferior parts of inferior constrictor muscle of pharynx respectively). The result is an outpouching of the posterior pharyngeal wall, just above the esophagus.

While it may be asymptomatic, Zenker diverticulum can present with the following symptoms:

- Dysphagia (difficulty swallowing), and sense of a lump in the throat

- Food might get trapped in the outpouching, leading to:

- Regurgitation, reappearance of ingested food in the mouth

- Cough, due to food regurgitated into the airway

- Halitosis, smelly breath, as stagnant food is digested by microorganisms

- Infection

It rarely, if ever, causes any pain.

Cervical webs are seen associated in 50% of patients with this condition.

Rarer forms of cervical esophageal diverticula are the Killian's diverticulum and the Laimer's diverticulum. Killian's diverticulum is formed in the Killian-Jamiseon triangle (located inferior to the cricopharyngeus on both sides of this muscle's insertion into the cricoid cartilage). Laimer's diverticulum is formed in Laimer's triangle (located inferior to the cricopharyngeus in the posterior midline above the confluence of the longitudinal layer of esophageal muscle). Laimer's triangle is covered only by the circular layer of esophageal muscle.

Diverticular disease can present with painless rectal bleeding as bright red blood per rectum. Diverticular bleeding is the most common cause of acute lower gastrointestinal bleeding. However, it is estimated that 80% of these cases are self-limiting and require no specific therapy.

The lifetime risk for a person with Meckel's diverticulum to develop certain complications is about 4–6%. Gastrointestinal bleeding, peritonitis or intestinal obstruction may occur in 15–30% of symptomatic patients (Table 1). Only 6.4% of all complications requires surgical treatment; and untreated Meckel's diverticulum has a mortality rate of 2.5–15%.

Table 1 – Complications of Meckel's Diverticulum:

A Zenker's diverticulum, also pharyngoesophageal diverticulum, also pharyngeal pouch, also hypopharyngeal diverticulum, is a diverticulum of the mucosa of the pharynx, just above the cricopharyngeal muscle (i.e. above the upper sphincter of the esophagus). It is a pseudo diverticulum (not involving all layers of the esophageal wall).

It was named in 1877 by German pathologist Friedrich Albert von Zenker.

Some people with diverticulosis complain of symptoms such as cramping, bloating, flatulence, and irregular defecation. However, it is unclear if these symptoms are attributable to the underlying diverticulosis or to coexistent irritable bowel syndrome.

Diverticular disease was found associated with a higher risk of left sided colon cancer.

A Killian–Jamieson diverticulum is an outpouching of the esophagus just below the upper esophageal sphincter.

The physicians that first discovered the diverticulum were Gustav Killian and James Jamieson. Diverticula are seldom larger than 1.5 cm, and are less frequent than the similar Zenker's diverticula. As opposed to a Zenker's, which is typically a posterior and inferior outpouching from the esophagus, a Killian–Jamieson diverticulum is typically an anterolateral outpouching at the level of the C5-C6 vertebral bodies, due to a congenital weakness in the cervical esophagus just below the cricopharyngeal muscle. It is usually smaller in size than a Zenker's diverticulum, and typically asymptomatic. Although congenital, it is more commonly seen in elderly patients.

Intussusception is a medical condition in which a part of the intestine folds into the section next to it. It typically involves the small bowel and less commonly the large bowel. Symptoms include abdominal pain which may come and go, vomiting, abdominal bloating, and bloody stool. It often results in a small bowel obstruction. Other complications may include peritonitis or bowel perforation.

The cause in children is typically unknown while in adults a lead point is often present. Risk factors in children include certain infections, diseases like cystic fibrosis, and intestinal polyps. Risk factors in adults include endometriosis, bowel adhesions, and intestinal tumors. Diagnosis is often supported by medical imaging. In children, ultrasound is preferred while in adults a CT scan is preferred.

Intussusception is an emergency requiring rapid treatment. Treatment in children is typically by an enema with surgery used if this is not successful. Dexamethasone may decrease the risk of another episode. In adults, surgical removal of part of the bowel is more often required. Intussusception occurs more commonly in children than adults. In children, males are more often affected than females. The usual age of occurrence is six to eighteen months old.

Diverticulitis typically presents with left lower quadrant abdominal pain of sudden onset. There may also be fever, nausea, diarrhea or constipation, and blood in the stool.

Urethral diverticula are often asymptomatic and symptoms that are present tend to be nonspecific. They can co-occur with cancer, in approximately 6-9% of cases, most commonly adenocarcinoma, but also including squamous cell carcinoma and transitional cell carcinoma. Approximately 10% of cases co-occur with kidney stones.

There are 2 types of urethral diverticulums. Congenital and acquired. In infancy usually the urethral diverticulum is congenital but in rare instances acquired urethral diverticulum can be seen in infancy specially following traumatic catheterization.

Common symptoms of urethral diverticulum include incontinence, urinary frequency and urgency, pain during sex, and pain during urination. Other symptoms include pain localized to the urethra or pelvis and frequent urinary tract infection.

When urethral diverticulum becomes severe, a painful mass can sometimes be felt inside the introitus of the vagina, which can discharge pus. If the mass is hard or bleeds, complications like cancer or kidney stones may be present.

In complicated diverticulitis, an inflamed diverticulum can rupture, allowing bacteria to subsequently infect externally from the colon. If the infection spreads to the lining of the abdominal cavity (the peritoneum), peritonitis results. Sometimes, inflamed diverticula can cause narrowing of the bowel, leading to an obstruction. In some cases, the affected part of the colon adheres to the bladder or other organs in the pelvic cavity, causing a , or creating an abnormal connection between an organ and adjacent structure or other organ (in the case of diverticulitis, the colon and an adjacent organ).

Related pathologies may include:

- Bowel obstruction

- Peritonitis

- Abscess

- Bleeding

- Strictures

A urethral diverticulum is a condition where the urethra or the periurethral glands push into the connective tissue layers (fascia) that surround it.

An enterolith is a mineral concretion or calculus formed anywhere in the gastrointestinal system. Enteroliths are uncommon and usually incidental findings but, once found, they require at a minimum watchful waiting. If there is evidence of complications, they must be removed.

An enterolith may form around a "nidus", a small foreign object such as a seed, pebble, or piece of twine, that serves as an irritant. In this respect, an enterolith forms by a process similar to the creation of a pearl.

An enterolith is not to be confused with a gastrolith, which helps digestion.

Anorectal anomalies and spinal cord defects may be a cause in children. These are usually picked up and operated upon during early life, but continence is often imperfect thereafter.

Functional disorders of the gallbladder, bile duct and pancreas have been defined and classified by the Rome criteria for functional gastrointestinal disorders. The criteria outline three variants of functional disorders of the gallbladder, bile duct and pancreas, termed "functional gallbladder disorder", "functional biliary sphincter of Oddi disorder" and "functional pancreatic sphincter of Oddi disorder". All of the following criteria need to be met for as part of the definition of a functional disorder of the gallbladder:

- the pain must be located in the upper part of the abdomen and/or the right upper quadrant of the abdomen

- episodes of pain must last at least 30 minutes

- the symptoms must be recurrent, and occur at differing intervals

- the pain must incrementally increase to a "steady level"

- the pain must be severe enough the patient's daily activities are affected, or that the patient must attend the emergency department

- the pain must not be relieved by any of bowel movements, change in posture, or antacids; and,

- other structural disorders that could explain the symptoms must be excluded.

Individuals are classified as having a functional gallbladder disorder if the above criteria are met, if the gallbladder is present, and if the testing of liver enzymes, conjugated bilirubin, and pancreatic enzymes (amylase and lipase) are normal.

FI affects virtually all aspects of peoples' lives, greatly diminishing physical and mental health, and affect personal, social and professional life. Emotional effects may include stress, fearfulness, anxiety, exhaustion, fear of public humiliation, feeling dirty, poor body-image, reduced desire for sex, anger, humiliation, depression, isolation, secrecy, frustration and embarrassment. Some people may need to be in control of life outside of FI as means of compensation. The physical symptoms such as skin soreness, pain and odor may also affect quality of life. Physical activity such as shopping or exercise is often affected. Travel may be affected, requiring careful planning. Working is also affected for most. Relationships, social activities and self-image likewise often suffer. Symptoms may worsen over time.

In humans, enteroliths are rare and may be difficult to distinguish from gall stones. Their chemical composition is diverse, and rarely can a nidus be found. A differential diagnosis of an enterolith requires the enterolith, a normal gallbladder, and a diverticulum.

An enterolith typically forms within a diverticulum. An enterolith formed in a Meckel's diverticulum sometimes is known as a Meckel's enterolith. Improper use of magnesium oxide as a "long-term" laxative has been reported to cause enteroliths and/or medication bezoars.

Most enteroliths are not apparent and cause no complications. However, any complications that do occur are likely to be severe. Of these, bowel obstruction is most common, followed by ileus and perforation. Bowel obstruction and ileus typically occur when a large enterolith is expelled from a diverticulum into the lumen. Perforation typically occurs within the diverticulum.

Most human enteroliths are radiolucent on plain X-rays. They sometimes can be visualized on CT scans without contrast; presence of contrast in the lumen may reveal the enterolith as a void. Most often, they are visualized using ultrasound.

Although recent surveys of enterolith composition are lacking, one early review notes struvite (as in equines), calcium phosphate, and calcium carbonate and reports choleic acid. Deoxycholic acid and cholic acid have also been reported.

By far the most common hernias develop in the abdomen, when a weakness in the abdominal wall evolves into a localized hole, or "defect", through which adipose tissue, or abdominal organs covered with peritoneum, may protrude. Another common hernia involves the spinal discs and causes "sciatica". A hiatus hernia occurs when the stomach protrudes into the "mediastinum" through the esophageal opening in the diaphragm.

Hernias may or may not present with either pain at the site, a visible or palpable lump, or in some cases more vague symptoms resulting from pressure on an organ which has become "stuck" in the hernia, sometimes leading to organ dysfunction. Fatty tissue usually enters a hernia first, but it may be followed or accompanied by an organ.

Hernias are caused by a disruption or opening in the fascia, or fibrous tissue, which forms the abdominal wall. It is possible for the bulge associated with a hernia to come and go, but the defect in the tissue will persist.

Symptoms and signs vary depending on the type of hernia. Symptoms may or may not be present in some inguinal hernias. In the case of reducible hernias, a bulge in the groin or in another abdominal area can often be seen and felt. When standing, such a bulge becomes more obvious. Besides the bulge, other symptoms include pain in the groin that may also include a heavy or dragging sensation, and in men, there is sometimes pain and swelling in the scrotum around the testicular area.

Irreducible abdominal hernias or incarcerated hernias may be painful, but their most relevant symptom is that they cannot return to the abdominal cavity when pushed in. They may be chronic, although painless, and can lead to strangulation (loss of blood supply), obstruction (kinking of intestine), or both. Strangulated hernias are always painful and pain is followed by tenderness. Nausea, vomiting, or fever may occur in these cases due to bowel obstruction. Also, the hernia bulge in this case may turn red, purple or dark and pink.

In the diagnosis of abdominal hernias, imaging is the principal means of detecting internal diaphragmatic and other nonpalpable or unsuspected hernias. Multidetector CT (MDCT) can show with precision the anatomic site of the hernia sac, the contents of the sac, and any complications. MDCT also offers clear detail of the abdominal wall allowing wall hernias to be identified accurately.

Hernias present as bulges in the groin area that can become more prominent when coughing, straining, or standing up. They are rarely painful, and the bulge commonly disappears on lying down. Mild discomfort can develop over time. The inability to "reduce", or place the bulge back into the abdomen usually means the hernia is 'incarcerated' which requires emergency surgery.

Significant pain is suggestive of strangulated bowel (an incarcerated indirect inguinal hernia).

As the hernia progresses, contents of the abdominal cavity, such as the intestines, liver, can descend into the hernia and run the risk of being pinched within the hernia, causing an intestinal obstruction. If the blood supply of the portion of the intestine caught in the hernia is compromised, the hernia is deemed "strangulated" and gut ischemia and gangrene can result, with potentially fatal consequences. The timing of complications is not predictable.

The upper GI tract is defined as the organs involved in digestion above the ligament of Treitz and comprises the esophagus, stomach, and duodenum. Upper gastrointestinal bleeding is typically characterized by melena (black stool). Bright red blood may be seen with active, rapid bleeding.

Complications may arise post-operation, including rejection of the mesh that is used to repair the hernia. In the event of a mesh rejection, the mesh will very likely need to be removed. Mesh rejection can be detected by obvious, sometimes localized swelling and pain around the mesh area. Continuous discharge from the scar is likely for a while after the mesh has been removed.

A surgically treated hernia can lead to complications such as inguinodynia, while an untreated hernia may be complicated by:

- Inflammation

- Obstruction of any lumen, such as bowel obstruction in intestinal hernias

- Strangulation

- Hydrocele of the hernial sac

- Hemorrhage

- Autoimmune problems

- Irreducibility or Incarceration, in which it cannot be reduced, or pushed back into place, at least not without very much external effort. In intestinal hernias, this also substantially increases the risk of bowel obstruction and strangulation.