Rectal tenesmus (Latin, from Greek teinesmos, from teinein to stretch, strain) is a feeling of incomplete defecation. It is the sensation of inability or difficulty to empty the bowel at defecation, even if the bowel contents have already been evacuated. Tenesmus indicates the feeling of a residue, and is not always correlated with the actual presence of residual fecal matter in the rectum. It is frequently painful and may be accompanied by involuntary straining and other gastrointestinal symptoms.

Tenesmus has both a nociceptive and a neuropathic component.

Vesical tenesmus is a similar condition, experienced as a feeling of incomplete voiding despite the bladder being empty.

Often, rectal tenesmus is simply called tenesmus. The term rectal tenesmus is a retronym to distinguish defecation-related tenesmus from vesical tenesmus.

Tenesmus is a closely related topic to obstructed defecation.

There are many different types of rectal discharge, but the most common presentation of a discharge is passage of mucus or pus wrapped around an otherwise normal bowel movement.

Rectal discharge has many causes, and may present with other symptoms:

- Staining of undergarments

- Constant feeling of dampness around anus

- Frequent urge to open bowels, but passage of only small amounts of mucus or pus-like liquid rather than normal feces

- Rectal pain

- Rectal malodor, when the discharge is foul-smelling, e.g. associated with certain infections

- Pruritus ani

- Rectal bleeding

- Perianal erythema, swelling and tenderness

Different types of discharge are described. Generally "rectal discharge" refers to either a mucous or purulent discharge, but, depending upon what definition of rectal discharge is used, the following could be included:

- Purulent rectal discharge

- Mucous rectal discharge

- Watery rectal discharge

- Steatorrhoea ("fatty diarrhea" caused by excess fat in stools, or an oily anal leakage)

- Keriorrhea (orange oily anal leakage caused by high levels of escolar and oilfish in the diet)

- Rectal bleeding, melena and hematochezia

- Feculent rectal discharge (fecal rectal discharge), e.g. fecal leakage, encopresis and incontinence of liquid stool elements

- Diarrhea

Fecal incontinence to gas, liquid, solid stool, or mucus in the presence of obstructed defecation symptoms may indicate occult rectal prolapse (i.e. rectal intussusception), internal/external anal sphincter dysfunction, or descending perineum syndrome.

A common symptom is a continual urge to have a bowel movement—the rectum could feel full or have constipation. Another is tenderness and mild irritation in the rectum and anal region. A serious symptom is pus and blood in the discharge, accompanied by cramps and pain during the bowel movement. If there is severe bleeding, anemia can result, showing symptoms such as pale skin, irritability, weakness, dizziness, brittle nails, and shortness of breath.

Symptoms are ineffectual straining to empty the bowels, diarrhea, rectal bleeding and possible discharge, a feeling of not having adequately emptied the bowels, involuntary spasms and cramping during bowel movements, left-sided abdominal pain, passage of mucus through the rectum, and anorectal pain.

Obstructed defecation, is "difficulty in evacuation or emptying the rectum [which] may occur even with frequent visits to the toilet and even with passing soft motions". The conditions that can create the symptom are sometimes grouped together as defecation disorders. The symptom tenesmus is a closely related topic.

Another source defines evacuatory dysfunction as "a constellation of symptoms such as prolonged repeated straining at bowel movements, sensation of incomplete evacuation, and the need for digital manipulation".

Some describe an "obstructed defecation syndrome", defining it loosely as "difficulty in evacuation, which may or may not be associated with constipation"

Others inappropriately equate obstructed defecation with anismus. Although anismus is a type of obstructed defecation, obstructed defecation has many other possible causes other than anismus.

Tenesmus is characterized by a sensation of needing to pass stool, accompanied by pain, cramping, and straining. Despite straining, little stool is passed. Tenesmus is generally associated with inflammatory diseases of the bowel, which may be caused by either infectious or noninfectious conditions. Conditions associated with tenesmus include:

- Amebiasis

- Coeliac disease

- Chronic arsenic poisoning

- Colorectal cancer

- Anal melanoma

- Cytomegalovirus (in immunocompromised patients)

- Diverticular disease

- Hemorrhoid, which are prolapsed

- Inflammatory bowel disease

- Irritable bowel syndrome

- Ischemic colitis

- Kidney stones, when a stone is lodged in the lower ureter

- Pelvic floor dysfunction

- Radiation proctitis

- Rectal gonorrhoea

- Rectal lymphogranuloma venereum

- Rectal lower gastrointestinal parasitic infection, particularly "Trichuris trichiura" (whipworm)

- Shigellosis

- Ulcerative colitis

Tenesmus (rectal) is also associated with the installation of either a reversible or non reversible stoma where rectal disease may or may not be present. Patients who experience tenesmus as a result of stoma installation can experience the symptoms of tenesmus for the duration of the stoma presence. Long term pain management may need to be considered as a result.

Symptoms include:

- Straining during defecation

- Mucous rectal discharge

- Rectal bleeding

- Sensation of incomplete evacuation (tenesmus)

- constipation, or more rarely diarrhea

- fecal incontinence (rarely)

The condition, along with complete rectal prolapse and internal rectal intussusception, is thought to be related to chronic straining during defecation and constipation.

Mucosal prolapse occurs when the results from loosening of the submucosal attachments (between the mucosal layer and the muscularis propria) of the distal rectum. The section of prolapsed rectal mucosa can become ulcerated, leading to bleeding.

Depending on the level of obstruction, bowel obstruction can present with abdominal pain, swollen abdomen, abdominal distension, vomiting, fecal vomiting, and constipation.

Bowel obstruction may be complicated by dehydration and electrolyte abnormalities due to vomiting; respiratory compromise from pressure on the diaphragm by a distended abdomen, or aspiration of vomitus; bowel ischemia or perforation from prolonged distension or pressure from a foreign body.

In small bowel obstruction, the pain tends to be colicky (cramping and intermittent) in nature, with spasms lasting a few minutes. The pain tends to be central and mid-abdominal. Vomiting may occur before constipation.

In large bowel obstruction, the pain is felt lower in the abdomen and the spasms last longer. Constipation occurs earlier and vomiting may be less prominent. Proximal obstruction of the large bowel may present as small bowel obstruction.

Constipation is a symptom, not a disease. Most commonly, constipation is thought of as infrequent bowel movements, usually less than 3 stools per week. However, people may have other complaints as well including:

- Straining with bowel movements

- Excessive time needed to pass a bowel movement

- Hard stools

- Pain with bowel movements secondary to straining

- Abdominal pain

- Abdominal bloating.

- the sensation of incomplete bowel evacuation.

The Rome Criteria are a set of symptoms that help standardize the diagnosis of constipation in various age groups. These criteria help physicians to better define constipation in a standardized manner.

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.

The rectum needs to be of a sufficient volume to store stool until defecation. The rectal walls need to be "compliant" i.e. able to distend to an extent to accommodate stool. Rectal sensation is required to detect the presence, nature and amount of rectal contents. The rectum must also be able to evacuate its contents fully. There must also be efficient co-ordination of rectal sensation and relaxation of the anal canal. If the sensory nerves are damaged, detection of stool in the rectum is dulled or absent, and the person will not feel the need to defecate until too late. Rectal hyposensitivity may manifest as constipation, FI, or both. Rectal hyposensitivty was reported to be present in 10% of people with FI. Pudendal neuropathy is one cause of rectal hyposensitivity, and may lead to fecal loading/impaction, megarectum and overflow FI. Normal evacuation of rectal contents is 90-100%. If there is incomplete evacuation during defecation, residual stool will be left in the rectum and threaten continence once defecation is finished. This is a feature of people with soiling secondary to obstructed defecation. Obstructed defecation is often due to anismus (paradoxical contraction or relaxation failure of the puborectalis). Whilst anismus is largely a functional disorder, organic pathologic lesions may mechanically interfere with rectal evacuation. Other causes of incomplete evacuation include non-emptying defects like a rectocele. Straining to defecate pushes stool into the rectocele, which acts like a diverticulum and causes stool sequestration. Once the voluntary attempt to defecate, albeit dysfunctional, is finished, the voluntary muscles relax, and residual rectal contents are then able to descend into the anal canal and cause leaking.

Proctitis is an inflammation of the anus and the lining of the rectum, affecting only the last 6 inches of the rectum.

Causes of small bowel obstruction include:

- Adhesions from previous abdominal surgery (most common cause)

- Barbed sutures.

- Pseudoobstruction

- Hernias containing bowel

- Crohn's disease causing adhesions or inflammatory strictures

- Neoplasms, benign or malignant

- Intussusception

- Volvulus

- Superior mesenteric artery syndrome, a compression of the duodenum by the superior mesenteric artery and the abdominal aorta

- Ischemic strictures

- Foreign bodies (e.g. gallstones in gallstone ileus, swallowed objects)

- Intestinal atresia

After abdominal surgery, the incidence of small bowel obstruction from any cause is 9%. In those where the cause of the obstruction was clear, adhesions are the single most common cause (more than half).

Symptoms include:

- Straining to pass fecal material

- Tenesmus (a feeling of incomplete evacuation)

- Feeling of anorectal obstruction/blockage

- Digital maneuvers needed to aid defecation

- Difficulty initiating and completing bowel movements

Constipation refers to bowel movements that are infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement. Complications from constipation may include hemorrhoids, anal fissure or fecal impaction. The normal frequency of bowel movements in adults is between three per day and three per week. Babies often have three to four bowel movements per day while young children typically have two to three per day.

Constipation has many causes. Common causes include slow movement of stool within the colon, irritable bowel syndrome, and pelvic floor disorders. Underlying associated diseases include hypothyroidism, diabetes, Parkinson's disease, celiac disease, non-celiac gluten sensitivity, colon cancer, diverticulitis, and inflammatory bowel disease. Medications associated with constipation include opioids, certain antacids, calcium channel blockers, and anticholinergics. Of those taking opioids about 90% develop constipation. Constipation is more concerning when there is weight loss or anemia, blood is present in the stool, there is a history of inflammatory bowel disease or colon cancer in a person's family, or it is of new onset in someone who is older.

Treatment of constipation depends on the underlying cause and the duration that it has been present. Measures that may help include drinking enough fluids, eating more fiber, and exercise. If this is not effective, laxatives of the bulk forming agent, osmotic agent, stool softener, or lubricant type may be recommended. Stimulant laxatives are generally reserved for when other types are not effective. Other treatments may include biofeedback or in rare cases surgery.

In the general population rates of constipation are 2–30 percent. Among elderly people living in a care home the rate of constipation is 50–75 percent. People spend, in the United States, more than on medications for constipation a year.

There is no globally accepted definition, but fecal incontinence is generally defined as the recurrent inability to voluntarily control the passage of bowel contents through the anal canal and expel it at a socially acceptable location and time, occurring in individuals over the age of four. "Social continence" has been given various precise definitions for the purposes of research, however generally it refers to symptoms being controlled to an extent that is acceptable to the individual in question, with no significant effect on their life. There is no consensus about the best way to classify FI, and several methods are used.

Symptoms can be directly or indirectly related to the loss of bowel control. The direct (primary) symptom is a lack of control over bowel contents which tends to worsen without treatment. Indirect (secondary) symptoms, which are the result of leakage, include pruritus ani (an intense itching sensation from the anus), perianal dermatitis (irritation and inflammation of the skin around the anus), and urinary tract infections. Due to embarrassment, people may only mention secondary symptoms rather than acknowledge incontinence. Any major underlying cause will produce additional signs and symptoms, such as protrusion of mucosa in external rectal prolapse. Symptoms of fecal leakage (FL) are similar, and may occur after defecation. There may be loss of small amounts of brown fluid and staining of the underwear.

Anismus is classified as a functional defecation disorder. It is also a type of rectal outlet obstruction (a functional outlet obstruction). Where anismus causes constipation, it is an example of functional constipation. Some authors describe an "obstructed defecation syndrome", of which anismus is a cause.

The Rome classification subdivides functional defecation disorders into 3 types, however the symptoms the patient experiences are identical.

- Type I: paradoxical contraction of the pelvic floor muscles during attempted defecation

- Type II: inadequate propulsive forces during attempted defecation (inadequate defecatory propulsion)

- Type III: impaired relaxation with adequate propulsion

It can be seen from the above classification that many of the terms that have been used interchangeably with anismus are inappropriately specific and neglect the concept of impaired propulsion. Similarly, some of the definitions that have been offered are also too restrictive.

An intussusception has two main differential diagnoses: acute gastroenteritis and rectal prolapse. Abdominal pain, vomiting, and stool with mucus and blood are present in acute gastroenteritis, but diarrhea is the leading symptom. Rectal prolapse can be differentiated by projecting mucosa that can be felt in continuity with the perianal skin, whereas in intussusception the finger may pass indefinitely into the depth of the sulcus.

Microscopic colitis causes chronic watery diarrhea with greater than 10 bowel movements per day. Some patients report nocturnal diarrhea, abdominal pain, urgency, fecal incontinence, fatigue, dehydration and weight loss. Patients report a significantly diminished quality of life.

The diagnosis is suspected based on polyhydramnios in uteru, bilious vomiting, failure to pass meconium in the first day of life, and abdominal distension. The presentations of NBO may vary. It may be subtle and easily overlooked on physical examination or can involve massive abdominal distension, respiratory distress and cardiovascular collapse. Unlike older children, neonates with unrecognized intestinal obstruction deteriorate rapidly.

Colic can be divided broadly into several categories:

1. excessive gas accumulation in the intestine (gas colic)

2. simple obstruction

3. strangulating obstruction

4. non-strangulating infarction

5. inflammation of the gastrointestinal tract (enteritis, colitis) or the peritoneum (peritonitis)

6. ulceration of the gastrointestinal mucosa

These categories can be further differentiated based on location of the lesion and underlying cause (See Types of colic).

Megarectum is a large rectum as a result of underlying nerve supply abnormalities or muscle dysfunction, which remains after disimpaction of the rectum. The Principles of Surgery textbook describes any rectum that can hold more than 1500cc of fluid as a megarectum. The term megarectum is also used for a large rectal mass on rectal examination, a wide rectum on an abdominal x-ray, the presence of impaired rectal sensation or the finding of large maximal rectal volumes on anorectal manometry. In addition, can be the bloating of the colon due to infection, also called megacolon. On defecography, megarectum is suggested by a rectal width of >9 cm at the level of the distal sacrum.

Neonatal bowel obstruction (NBO) or neonatal intestinal obstruction is the most common surgical emergency in the neonatal period. It may occur due to a variety of conditions and has an excellent outcome based on timely diagnosis and appropriate intervention.