This investigation is used to diagnose internal intussusception, or demonstrate a suspected external prolapse that could not be produced during the examination. It is usually not necessary with obvious external rectal prolapse. Defecography may demonstrate associated conditions like cystocele, vaginal vault prolapse or enterocele.

These may reveal congestion and edema (swelling) of the distal rectal mucosa, and in 10-15% of cases there may be a solitary rectal ulcer on the anterior rectal wall. Localized inflammation or ulceration can be biopsied, and may lead to a diagnosis of SRUS or colitis cystica profunda. Rarely, a neoplasm (tumour) may form on the leading edge of the intussusceptum. In addition, patients are frequently elderly and therefore have increased incidence of colorectal cancer. Full length colonoscopy is usually carried out in adults prior to any surgical intervention. These investigations may be used with contrast media (barium enema) which may show the associated mucosal abnormalities.

Identification of the exact causes usually begins with a thorough medical history, including detailed questioning about symptoms, bowel habits, diet, medication and other medical problems. Digital rectal examination is performed to assesses resting pressure and voluntary contraction (maximum squeeze) of the sphincter complex and puborectalis. Anal sphincter defects, rectal prolapse, and abnormal perineal descent may be detected. Anorectal physiology tests assess the functioning of the anorectal anatomy. Anorectal manometry records the pressure exerted by the anal sphincters and puborectalis during rest and during contraction. The procedure is also able to assess sensitivity of the anal canal and rectum. Anal electromyography tests for nerve damage, which is often associated with obstetric injury. Pudendal nerve terminal motor latency tests for damage to the pudendal motor nerves. Proctography, also known as defecography, shows how much stool the rectum can hold, how well the rectum holds it, and how well the rectum can evacuate the stool. It will also highlight defects in the structure of the rectum such as internal rectal intussusception. Dynamic pelvic MRI, also called MRI defecography is an alternative which is better for some problems but not as good for other problems. Proctosigmoidoscopy involves the insertion of an endoscope (a long, thin, flexible tube with a camera) into the anal canal, rectum and sigmoid colon. The procedure allows for visualization of the interior of the gut, and may detect signs of disease or other problems that could be a cause, such as inflammation, tumors, or scar tissue. Endoanal ultrasound, which some consider to be the gold standard for detection of anal canal lesions, evaluates the structure of the anal sphincters, and may detect occult sphincter tears that otherwise would go unseen.

Functional FI is common. The Rome process published diagnostic criteria for functional FI, which they defined as "recurrent uncontrolled passage of fecal material in an individual with a developmental age of at least 4 years". The diagnostic criteria are, one or more of the following factors present for the last 3 months: abnormal functioning of normally innervated and structurally intact muscles, minor abnormalities of sphincter structure/innervation (nerve supply), normal or disordered bowel habits, (i.e., fecal retention or diarrhea), and psychological causes. Furthermore, exclusion criteria are given. These are factors which all must be excluded for a diagnosis of functional FI, and are abnormal innervation caused by lesion(s) within the brain (e.g., dementia), spinal cord (at or below T12), or sacral nerve roots, or mixed lesions (e.g., multiple sclerosis), or as part of a generalized peripheral or autonomic neuropathy (e.g., due to diabetes), anal sphincter abnormalities associated with a multisystem disease (e.g., scleroderma), and structural or neurogenic abnormalities that are the major cause.

Physical examination can rule out anismus (by identifying another cause) but is not sufficient to diagnose anismus.

The rectal cooling test is suggested to differentiate between rectal inertia and impaired relaxation/paradoxical contraction

Other techniques include manometry, balloon expulsion test, evacuation proctography (see defecating proctogram), and MRI defecography. Diagnostic criteria are: fulfillment of criteria for functional constipation, manometric and/or EMG and/or radiological evidence (2 out of 3), evidence of adequate expulsion force, and evidence of incomplete evacuation. Recent dynamic imaging studies have shown that in persons diagnosed with anismus the anorectal angle during attempted defecation is abnormal, and this is due to abnormal (paradoxical) movement of the puborectalis muscle.

Several severity scales exist. The Cleveland Clinic (Wexner) fecal incontinence score takes into account five parameters that are scored on a scale from zero (absent) to four (daily) frequency of incontinence to gas, liquid, solid, of need to wear pad, and of lifestyle changes. The Park's incontinence score uses four categories:

The fecal incontinence severity index is based on four types of leakage (gas, mucus, liquid stool, solid stool) and five frequencies (once to three times per month, once per week, twice per week, once per day, twice or more per day). Other severity scales include: AMS, Pescatori, Williams score, Kirwan, Miller score, Saint Mark's score and the Vaizey scale.

The two key features of obstructed defecation are:

1. An inability to voluntarily evacuate rectal contents

2. Normal colonic transit time

A 5 item questionnaire was validated for diagnosis and grading of obstructed defecation syndrome. The parameters were:

1. Excessive straining

2. Incomplete rectal evacuation

3. Use of enemas and/or laxatives

4. Vaginal-anal-perineal digitations (needing to press in the back wall of the vagina or on the perineum to aid defecation)

5. Abdominal discomfort and/or pain

Obstructed defecation has many causes, so the management in any individual case is specific to the cause of the symptom. For rectal internal intususception treatment is surgical, either STARR or rectopexy. For rectocele STARR or mesh implantation. For anismus/ pelvic floor dessynergia: biofeedback exercise.

Diagnosis is by rectal examination. A specialized tool called a "Perineocaliper" can be used to measure the descent of the perineum. A retro anal ultrasound scan may demonstrate the condition. "Anti sagging tests", whereby the abnormal descent is corrected temporarily, may help to show whether symptoms are due to descending perineum syndrome or are in fact due to another condition.

Normally, the anal margin lies just below a line drawn between the coccyx (tailbone) and the pubic symphysis. In descending perineum syndrome the anal canal is situated several cm below this imaginary line, or it descends 3–4 cm during straining.

Defecography may also demonstrate abnormal perineal descent.

Screening methods for colon cancer depend on detecting either precancerous changes such as certain kinds of polyps or on finding early and thus more treatable cancer. The extent to which screening procedures reduce the incidence of gastrointestinal cancer or mortality depends on the rate of precancerous and cancerous disease in that population. gFOBT (guaiac fecal occult blood test) and flexible sigmoidoscopy screening have each shown benefit in randomized clinical trials. Evidence for other colon cancer screening tools such as iFOBT (immunochemical fecal occult blood test) or colonoscopy is substantial and guidelines have been issued by several advisory groups but does not include randomized studies.

In 2009 the American College of Gastroenterology (ACG) suggest that colon cancer screening modalities that are also directly preventive by removing precursor lesions should be given precedence, and prefer a colonoscopy every 10 years in average-risk individuals, beginning at age 50. The ACG suggests that cancer detection tests such as any type of FOB are an alternative that is less preferred, and if a colonoscopy is declined, the FIT (fecal immunochemical test, or iFOBT) should be offered instead. Two other recent guidelines, from the US Multisociety Task Force (MSTF) and the US Preventive Services Task Force (USPSTF), while permitting immediate colonoscopy as an option, did not categorize it as preferred. The ACG and MSTF also included CT colonography every five years, and fecal DNA testing as considerations. All three recommendation panels recommended replacing any older low-sensitivity, guaiac-based fecal occult blood testing (gFOBT) with either newer high-sensitivity guaiac-based fecal occult blood testing (hs gFOBT) or fecal immunochemical testing (FIT). MSTF looked at six studies that compared high sensitivity gFOBT (Hemoccult SENSA) to FIT, and concluded that there was no clear difference in overall performance between these methods.

The American College of Gastroenterology has recommended the abandoning of gFOBT testing as a colorectal cancer screening tool, in favor of the fecal immunochemical test. Though the FIT test is preferred, even the guaiac FOB testing of average risk populations may have been sufficient to reduce the mortality associated with colon cancer by about 25%. With this lower efficacy, it was not always cost effective to screen a large population with gFOBT.

If colon cancer is suspected in an individual (such as in someone with an unexplained anemia) fecal occult blood tests may not be clinically helpful. If a doctor suspects colon cancer, more rigorous investigation is necessary, whether or not the test is positive.

In 2006, the Australian Government introduced the National Bowel Cancer Program which has been updated several times since; targeted screening will be done of all Australians aged over 50 to 74 by 2017–2018. Cancer Council Australia recommended that FOBT should be done every two years. Gradually government fund disbursement meant that some people are not yet eligible for the national program and should pay for a FOBT by themselves.

The Canadian Cancer Society recommends that men and women age 50 and over have a FOBT at least every 2 years.

In colon cancer screening, using only one sample of feces collected by a doctor performing a digital rectal examination is discouraged.

The use of the M2-PK Test is encouraged over gFOBT for routine screening as it may pick up tumors that are both bleeding and non bleeding. It is able to pick up 80 percent of colorectal cancer and 44 percent for adenoma > 1 centimeter, while gFOBT picks up 13 to 50 percent of colorectal cancers.

Doctors can diagnose proctitis by looking inside the rectum with a proctoscope or a sigmoidoscope. A biopsy is taken, in which the doctor scrapes a tiny piece of tissue from the rectum, and this tissue is then examined by microscopy. The physician may also take a stool sample to test for infections or bacteria. If the physician suspects that the patient suffers from Crohn's disease or ulcerative colitis, colonoscopy or barium enema X-rays are used to examine areas of the intestine.

An extensive literature has examined the clinical value of FOBT in iron deficiency anemia.

After diagnosing rectovaginal fistula, it is best to wait for around 3 months to allow the inflammation to subside. For low fistulae, a vaginal approach is best, while an abdominal repair would be necessary for a high fistula at the posterior fornix.

A circular incision is made around the fistula and vagina is separated from the underlying rectum with a sharp circumferential dissection. The entire fistulous tract, along with a small rim of rectal mucosa is incised. The rectal wall is then closed extramucosally.

Most rectovaginal fistuals will need surgery to fix. Medications such as antibiotics and Infliximab might be prescribed to help close the rectovaginal fistula or prepare for surgery.

Pelvic floor dysfunction can be diagnosed by history and physical exam, though it is more accurately graded by imaging. Historically, fluoroscopy with defecography and cystography were used, though modern imaging allows the usage of MRI to complement and sometimes replace fluoroscopic assessment of the disorder, allowing for less radiation exposure and increased patient comfort, though an enema is required the evening before the procedure. Instead of contrast, ultrasound gel is used during the procedure with MRI. Both methods assess the pelvic floor at rest and maximum strain using coronal and sagittal views. When grading individual organ prolapse, the rectum, bladder and uterus are individually assessed, with prolapse of the rectum referred to as a rectocele, bladder prolapse through the anterior vaginal wall a cystocele, and small bowel an enterocele.

To assess the degree of dysfunction, three measurements must be taken into account. First, an anatomic landmark known as the pubococcygeal line must be determined, which is a straight line connecting the inferior margin of the pubic symphysis at the midline with the junction of the first and second coccygeal elements on a sagittal image. After this, the location of the puborectalis muscle sling is assessed, and a perpendicular line between the pubococcygeal line and muscle sling is drawn. This provides a measurement of "pelvic floor descent", with descent greater than 2 cm being considered mild, and 6 cm being considered severe. Lastly, a line from the pubic symphysis to the puborectalis muscle sling is drawn, which is a measurement of the pelvic floor hiatus. Measurements of greater than 6 cm are considered mild, and greater than 10 cm severe. The degree of organ prolapse is assessed relative to the hiatus. The grading of "organ prolapse" relative to the hiatus is more strict, with any descent being considered abnormal, and greater than 4 cm being considered severe.

Colostomy is recommended by most surgeons, and has a good prognosis, with 90% of patients regaining normal bowel control. Since the rectal opening and anal orifice in a vestibular fistula tend to be short and narrow, a colostomy is usually performed to allow decompression of the bowel unless the orifice is wide enough to allow normal defecation. Colostomy is often followed by posterior sagittal anorectoplasty (PSARP), a surgical procedure to repair the anal orifice, at a later date. Some surgeons prefer to perform an immediate PSARP without a colostomy first, while others perform neither a colostomy nor a PSARP and instead opt for a simple dilatation of the orifice to allow stool to pass and the bowel to decompress. It has been suggested that only experienced surgeons should perform repair without an initial colostomy.

Surgical treatments may be used to treat the condition, and include retro-rectal levatorplasty, post-anal repair, retro-anal levator plate myorrhaphy.

Various modalities of diagnosis are available:

- Cystoscopy

- Colonoscopy

- Poppy seed test

- Transabdominal ultrasonography

- Abdominopelvic CT

- MRI

- Barium enema

- Bourne test

- Cystogram

A definite algorithm of tests is followed for making the diagnosis.

Pain relief is administered concomitantly to the treatment of the primary disease causing tenesmus. Methadone has been shown to be an effective pain-reliever.

Diagnosis is achieved mainly by plain and contrasted radiographical and ultrasound imaging. Colonic marker transit studies are useful to distinguish colonic inertia from functional outlet obstruction causes. In this test, the patient swallows a water-soluble bolus of radio-opaque contrast and films are obtained 1, 3 and 5 days later. Patients with colonic inertia show the marker spread throughout the large intestines, while patients with outlet obstruction exhibit slow accumulations of markers in some places. A colonoscopy can also be used to rule out mechanical obstructive causes. Anorectal manometry may help to differentiate acquired from congenital forms. Rectal biopsy is recommended to make a final diagnosis of Hirschsprung disease.

The diagnosis of a rectovestibular fistula can be made in female newborns if the vulva is stained with meconium (the earliest form of stool in an infant). The opening of the anus may be difficult to see due to its small size and position, but it may be visible as a thickening of the median perineal raphe with an obvious anal dimple. Patients with rectovestibular fistulae are commonly misdiagnosed with rectovaginal fistulae.

It is important to note that both barium enema and colonoscopy are contraindicated during acute episodes of diverticulitis, as the barium may leak out into the abdominal cavity, and colonoscopy can cause perforations of the bowel wall.

Treatment depends on the severity of the problem, and may include non-surgical methods such as changes in diet (increase in fiber and water intake), pelvic floor exercises such as Kegel exercises, use of stool softeners, hormone replacement therapy for post-menopausal women and insertion of a pessary into the vagina. A high fiber diet, consisting of 25-30 grams of fiber daily, as well as increased water intake (typically 6-8 glasses daily), help to avoid constipation and straining with bowel movements, and can relieve symptoms of rectocele.

Doctors uses a variety of tools and techniques to evaluate the type of anorectal disorder, including digital and anoscopic investigations, palpations, and palpitations. The initial examination can be painful because a gastroenterologist will need to spread the buttocks and probe the painful area, which may require a local anesthetic.

Surgery can be done to correct rectocele when symptoms continue despite the use of non-surgical management, and are significant enough to interfere with activities of daily living.

Surgery to correct the rectocele may involve the reattachment of the muscles that previously supported the pelvic floor. Another procedure is posterior colporrhaphy, which involves suturing of vaginal tissue. Surgery may also involve insertion of a supporting mesh (that is, a patch). There are also surgical techniques directed at repairing or strengthening the rectovaginal septum, rather than simple excision or plication of vaginal skin which provides no support. Both gynecologists and colorectal surgeons can address this problem. Potential complications of surgical correction of a rectocele include bleeding, infection, dyspareunia (pain during intercourse), as well as recurrence or even worsening of the rectocele symptoms. The use of synthetic or biologic grafts has been questioned.

Treatment for proctitis varies depending on severity and the cause. For example, the physician may prescribe antibiotics for proctitis caused by bacterial infection. If the proctitis is caused by Crohn's disease or ulcerative colitis, the physician may prescribe the drug 5-aminosalicyclic acid (5ASA) or corticosteroids applied directly to the area in enema or suppository form, or taken orally in pill form. Enema and suppository applications are usually more effective, but some patients may require a combination of oral and rectal applications.

Another treatment available is that of fiber supplements such as Metamucil. Taken daily these may restore regularity and reduce pain associated with proctitis.