In medicine or

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

, a diverticulum is an outpouching of a hollow (or a fluid-filled) 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, but in

embryology Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and ...

, the term is used for some normal structures arising from others, as for instance the

thyroid diverticulum The thyroid pouch or thyroid diverticulum is the embryological structure of the second pharyngeal arch from which thyroid follicular cells derive. It grows from the floor of the pharynx The pharynx (plural: pharynges) is the part of the throat ...

, which arises from the

tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...

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

submucosa The submucosa (or tela submucosa) is a thin layer of tissue (biology), tissue in various organ (anatomy), organs of the gastrointestinal tract, gastrointestinal, respiratory tract, respiratory, and genitourinary system, genitourinary tracts. It i ...

and

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

. *True diverticula involve all layers of the structure, including

muscularis propria The muscular layer (muscular coat, muscular fibers, muscularis propria, muscularis externa) is a region of muscle in many organs in the vertebrate body, adjacent to the submucosa. It is responsible for gut movement such as peristalsis. The Latin, ...

and

adventitia The adventitia () is the outer layer of fibrous connective tissue surrounding an organ. The outer layer of connective tissue that surrounds an artery, or vein – the tunica externa, is also called the ''tunica adventitia''. To some degree, its ...

, such as

Meckel's diverticulum A Meckel's diverticulum, a true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct or yolk stalk). It is the most common malformat ...

Embryology

*The

kidneys The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

are originally diverticula in the

development of the urinary and reproductive organs The development of the urinary system begins during prenatal development, and relates to the development of the urogenital system – both the organs of the urinary system and the sex organs of the reproductive system. The development continues as ...

. *The

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

are originally diverticula forming off of the ventral foregut. *The

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

appears in the form of two flask-shape diverticula, which arise from the third

branchial pouch In the embryonic development of vertebrates, pharyngeal pouches form on the endodermal side between the pharyngeal arches. The pharyngeal grooves (or clefts) form the lateral ectodermal surface of the neck region to separate the arches. The pou ...

(pharyngeal pouch) of the

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gast ...

. *The

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

gland develops as a diverticulum arising from a point on the tongue, demarcated as the foramen cecum. Oesophageal diverticula

Human pathology

Gastrointestinal tract diverticula

*Esophageal diverticula may occur in one of three areas of the esophagus: :#Pharyngeal ( Zenker's) diverticula usually occur in the elderly, through Killian's triangle above the

cricopharyngeal muscle The inferior pharyngeal constrictor muscle is a skeletal muscle of the neck. It is the thickest of the three outer pharyngeal muscles. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the vagus nerve ...

. :#Midesophageal diverticula :#Epiphrenic diverticula are due to dysfunction of the lower esophageal sphincter, as in

achalasia Esophageal achalasia, often referred to simply as achalasia, is a failure of smooth muscle fibers to relax, which can cause the lower esophageal sphincter to remain closed. Without a modifier, "achalasia" usually refers to achalasia of the esoph ...

. *A duodenal diverticulum can be found incidentally in 23% of normal people undergoing imaging. It can be either congenital or acquired, but the acquired form is more common and is due to the weakness of the duodenal wall, which causes protrusions. It is usually found at the second or third part of duodenum, around the ampulla of Vater. Food debris may enter the diverticular outpouchings, causing inflammation or diverticulitis. On CT or MRI imaging, it appears as a sac-like outpouching. If the diverticulum is filled with contrast agents, the wall would be thin and may contain air, fluid, contrast material, or food debris. If the food debris is broken down by bacteria, the outpouching may show "faeces sign". Inflammation of the duodenal wall shows thickening of the wall. Rarely, on barium studies in congenital duodenal diverticula, the contrast material fills up the true lumen, causing "

windsock A windsock (also called a wind cone) is a conical textile tube that resembles a giant sock. It can be used as a basic indicator of wind speed and direction, or as decoration. They are typically used at airports to show the direction and strength ...

" deformity. *A jejunal diverticulum is a congenital lesion and may be a source of bacterial overgrowth. It may also perforate or result in abscesses. *A 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, may become infected (see diverticulitis) and can perforate, requiring surgery. *Gastric diverticula are very infrequent. *

, a persistent portion of the

omphalomesenteric duct In the human embryo, the vitelline duct, also known as the vitellointestinal duct, the yolk stalk, the omphaloenteric duct, or the omphalomesenteric duct, is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus. ...

, is present in 2% of the population, making it the most common congenital gastrointestinal malformation. Histopathology of a false diverticulum of the gallbladder

Histopathology of a false diverticulum of the gallbladder

Rokitansky-Aschoff sinuses Adenomyomatosis is a benign condition characterized by hyperplastic changes of unknown cause involving the wall of the gallbladder. Adenomyomatosis is caused by an overgrowth of the mucosa, thickening of the muscular wall, and formation of intram ...

are diverticula in the

gallbladder In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although ...

due to chronic

cholecystitis Cholecystitis is inflammation of the gallbladder. Symptoms include right upper abdominal pain, pain in the right shoulder, nausea, vomiting, and occasionally fever. Often gallbladder attacks (biliary colic) precede acute cholecystitis. The pai ...

Most of these pathological types of diverticula 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.

Genito-urinary tract diverticula

*Bladder diverticula are balloon-like growths on the bladder commonly associated with chronic outflow obstruction, such as

benign prostatic hyperplasia Benign prostatic hyperplasia (BPH), also called prostate enlargement, is a noncancerous increase in size of the prostate gland. Symptoms may include frequent urination, trouble starting to urinate, weak stream, inability to urinate, or loss o ...

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. *Calyceal diverticula are usually asymptomatic, but if a stone becomes lodged in the outpouching, they may present with pain. *Urethral diverticula are usually found in women aged 30 to 70 years old, in between 1 and 6% of adult women. Since most cases are without any symptoms, the true incidence is unknown. Symptoms may vary from frequent urinary tract infections, painful sexual intercourse ( dyspareunia), or symptoms due to cancer. A urethral diverticulum is located on the anterior vaginal wall, 1 to 3 cm inside the

vaginal introitus In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen. ...

. MRI is preferred as the imaging method of choice due to its excellent soft-tissue resolution. On

T2-weighted imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wa ...

, it shows a high signal in the diverticulum due to the presence of fluid inside it.

Vaginal ultrasonography Vaginal ultrasonography is a medical ultrasonography that applies an ultrasound transducer (or "probe") in the vagina to visualize organs within the pelvic cavity. It is also called transvaginal ultrasonography because the ultrasound waves go ''a ...

is highly sensitive in diagnosing the diverticulum, but it is strongly dependent on the skills of the operator.

Other diverticula

*A diverticulum of Kommerell is an outpouching (aneurysm) 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. *Cardiac diverticulum is a very rare congenital malformation of the heart that is usually benign.

Gallery

File:Diverticule de Meckel.jpg, Meckel's diverticulum File:Diverticula, sigmoid colon.jpg, Large bowel (sigmoid colon) showing multiple diverticula: Note how the diverticula appear on either side of the longitudinal muscle bundle (taenium). File:Diverticulum of the colon.jpg, Colonic diverticulum File:Harnblasendivertikel-transversal.jpg, Diverticulum of the urinary bladder of a 59-year-old man, transverse plane File:BladderdiverticuliwithstoneMark.png, Bladder diverticula containing stones: Also note that the bladder wall is thickened due to possible

transitional cell carcinoma Transitional cell carcinoma, also called urothelial carcinoma, is a type of cancer that typically occurs in the urinary system. It is the most common type of bladder cancer and cancer of the ureter, urethra, and urachus. It accounts for 95% of ...

. File:UOTW 56 - Ultrasound of the Week 2.webm, Bladder diverticula as seen on ultrasound with doppler File:UOTW 56 - Ultrasound of the Week 1.webm, Bladder diverticula as seen on ultrasound

References

External links

{{Medical resources , DiseasesDB = , ICD10 = , ICD9 = , ICDO = , OMIM = , MedlinePlus = , eMedicineSubj = , eMedicineTopic = , MeshID = D004240 Medical terminology