In medicine or biology, a diverticulum is an outpouching of a hollow structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, the term usually implies the structure is not normally present. However, in embryology the term is used for some normal structures arising from others, as for instance the thyroid diverticulum, which arises from the tongue. The word comes from Latin dīverticulum, "bypath" or "byway."
Classification
Diverticula are described as being true or false depending upon the layers involved:
False diverticula do not involve muscular layers or adventitia. False diverticula, in the gastrointestinal tract for instance, involve only the submucosa and mucosa.
Meckel's diverticulum: a persistent portion of the omphalomesenteric duct present in 2% of the population, making it the most common congenital gastrointestinal malformation.
Esophageal diverticula may occur in one of three areas of the esophagus:
Killian-Jamieson diverticulum- is very similar to a pharyngeal esophageal diverticulum, differing in the fact that the pouching is below the cricopharyngeal muscle.
Colonic diverticula: Although found incidentally during colonoscopy, these diverticula may become infected and can perforate, requiring surgery.
Duodenal divertiula: Such condition can be found incidentally in 23% of the normal people underwent imaging. It can be either congenital or acquired but the acquired form is more common. It is due to the weakness of the duodenal wall which causes protusions. It is usually found at the 2nd or 3rd part of duodenum, around the Ampulla of Vater. Food debris may enter the diverticula outpouchings, causing inflammation or diverticulitis. On CT or MRI imaging, they appear as sac-like outpouchings. If the diverticula are filled with contrast agents, the wall would be thin, which may contain air, fluid, contrast material or food debris. If the food debris is broken down by bacteria, the outpouchings may show "faeces sign". Inflammation of the duodenal wall will show thickening of the wall. Rarely, on barium studies in congenital duodenal diverticula, the contrast material fill-up the true lumen, causing "windsock deformity.
Jejunal diverticul: are congenital lesions and may be a source of bacterial overgrowth. They may also perforate or result in abscesses.
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.
Calyceal diverticulum: usually asymptomatic, but if a stone becomes lodged in the outpouching they may present with pain.
Bladder diverticulum: Balloon-like growths on the bladder commonly associated with a chronic outflow obstruction, such as benign prostatic hyperplasia in older males. Usually found in pairs on opposite sides of the bladder, bladder diverticula are often surgically removed to prevent infection, rupture, or even cancer.
Urethral diverticulum: Urethral diverticula are usually found in women aged 30 to 70 years old, between 1% to 6% of adult women. Since majority of cases are without any symptoms, the true incidence is unknown. Symptoms may vary from frequent urinary tract infections, painful sexual intercourse, or symptoms due to cancer. Urethral diverticulum is located on the anterior vaginal wall, 1 to 3 cm inside the vaginal introitus. MRI is preferred as the imaging of choice due to its excellent soft-tissue resolution. On T2 weighted imaging, it will show high signal in the diverticulum due to the presence of fluid inside it. Vaginal ultrasonography is highly sensitive in diagnosing the diverticulum but it is strongly dependent on the skills of the operator.
Other diverticula
Cardiac diverticulum: A very rare congenital malformation of the heart that is usually benign
Diverticulum of Kommerell: is an out-pouching of the aorta where an aberrant right subclavian artery is located. It is unusual nomenclature, in that focal dilatations of a blood vessel are properly referred to as aneurysms.
