In about 50-70% of patients with dyspepsia, no definite organic cause can be determined. In this case, dyspepsia is referred to as non-ulcer dyspepsia and its diagnosis is established by the presence of epigastralgia for at least 6 months, in the absence of any other cause explaining the symptoms.

In most cases, the clinical history is of limited use in distinguishing between organic causes and functional dyspepsia. A large systematic review of the literature was recently performed to evaluate the effectiveness of diagnosing organic dyspepsia by clinical opinion versus computer models in patients referred for upper endoscopy. The computer models were based on patient demographics, risk factors, historical items, and symptoms. The study showed that neither clinical impression nor computer models were able to adequately distinguish organic from functional disease.

In a recent study, patients with peptic ulcer disease were compared with patients with functional dyspepsia in an age and sex-matched study. Although the functional dyspepsia group reported more upper abdominal fullness, nausea, and overall greater distress and anxiety, almost all the same symptoms were seen in both groups.

Therefore, it is the clinician’s challenging task to separate patients who may have an organic disorder, and thus warrant further diagnostic testing, from patients who have functional dyspepsia, who are given empiric symptomatic treatment.The workup should be targeted to identify or rule out specific causes. Traditionally, people at high-risk have been identified by “alarm” features. However, the utility of these features in identifying the presence of upper cancer of the esophagus or stomach has been debated. A meta analysis looking at the sensitivity and specificity of alarm features found a range of 0–83% and 40–98%, respectively. However, there was high heterogeneity between studies.

The physical examination may elicit abdominal tenderness, but this finding is nonspecific. A positive Carnett sign, or focal tenderness that increases with abdominal wall contraction and palpation, suggests an etiology involving the abdominal wall musculature. Cutaneous dermatomal distribution of pain may suggest a thoracic polyradiculopathy. Thump tenderness over the right upper quadrant may suggest chronic cholecystitis.

Crohn's disease is an inflammatory bowel disease that can affect any part of the digestive tract, even the stomach, although it's a rare presentation. Its main feature is inflammatory ulcers that can affect the total thickness of the stomach wall and can bleed but rarely perforate.

Symptoms include abdominal pain, loss of appetite, and weight loss. Diarrhea is also a symptom that can develop, so checking stools for the appearance of blood is important. It is possible for symptoms of Crohn's disease to remain with a person for weeks or go away on their own. Reporting the symptoms to a doctor is recommended to prevent further complications.

In the stomach there is a slight balance between acid and the wall lining which is protected by mucus. When this mucus lining is disrupted for whatever reason, signs and symptoms of acidity result. This may result in upper abdominal pain, indigestion, loss of appetite, nausea, vomiting and heartburn. When the condition is allowed to progress, the pain may become continuous; blood may start to leak and be seen in the stools. If the bleeding is rapid and of adequate volume it may even result in vomiting of bright red blood (hematemesis). When the acidity is uncontrolled, it can even cause severe blood loss (anemia) or lead to perforation (hole) in the stomach which is a surgical emergency. In many individuals, the progressive bleeding from an ulcer mixes with the feces and presents as black stools. Presence of blood in stools is often the first sign that there is a problem in the stomach.

The small intestine consists of the duodenum, jejunum and ileum. Inflammation of the small intestine is called enteritis, which if localised to just part is called duodenitis, jejunitis and ileitis, respectively. Peptic ulcers are also common in the duodenum.

Chronic diseases of malabsorption may affect the small intestine, including the autoimmune coeliac disease, infective Tropical sprue, and congenital or surgical short bowel syndrome. Other rarer diseases affecting the small intestine include Curling's ulcer, blind loop syndrome, Milroy disease and Whipple's disease. Tumours of the small intestine include gastrointestinal stromal tumours, lipomas, hamartomas and carcinoid syndromes.

Diseases of the small intestine may present with symptoms such as diarrhoea, malnutrition, fatigue and weight loss. Investigations pursued may include blood tests to monitor nutrition, such as iron levels, folate and calcium, endoscopy and biopsy of the duodenum, and barium swallow. Treatments may include renutrition, and antibiotics for infections.

Gastrointestinal diseases refer to diseases involving the gastrointestinal tract, namely the esophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the liver, gallbladder, and pancreas.

Terms such as "functional colonic disease" (or "functional bowel disorder") refer in medicine to a group of bowel disorders which are characterised by chronic abdominal complaints without a structural or biochemical cause that could explain symptoms. Other "functional" disorders relate to other aspects of the process of digestion.

The consensus review process of meetings and publications organised by the Rome Foundation, known as the Rome process, has helped to define the functional gastrointestinal disorders. Successively, the Rome I, Rome II, Rome III and Rome IV proposed consensual classification system and terminology, as recommended by the Rome Coordinating Committee. These now include classifications appropriate for adults, children and neonates / toddlers.

The current Rome IV classification, published in 2016, is as follows:

A. Esophageal Disorders

- A1. Functional chest pain

- A2. Functional heartburn

- A3. Reflux hypersensitivity

- A4. Globus

- A5. Functional dysphagia

B. Gastroduodenal Disorders

- B1. Functional dyspepsia

- B1a. Postprandial distress syndrome (PDS)

- B1b. Epigastric pain syndrome (EPS)

- B2. Belching disorders

- B2a. Excessive supragastric belching

- B2b. Excessive gastric belching

- B3. Nausea and vomiting disorders

- B3a. Chronic nausea vomiting syndrome (CNVS}

- B3b. Cyclic vomiting syndrome (CVS)

- B3c. Cannabinoid hyperemesis syndrome (CHS)

- B4. Rumination syndrome

C. Bowel Disorders

- C1. Irritable bowel syndrome (IBS)

- IBS with predominant constipation (IBS-C)

- IBS with predominant diarrhea (IBS-D)

- IBS with mixed bowel habits (IBS-M)

- IBS unclassified (IBS-U)

- C2. Functional constipation

- C3. Functional diarrhea

- C4. Functional abdominal bloating/distension

- C5. Unspecified functional bowel disorder

- C6. Opioid-induced constipation

D. Centrally Mediated Disorders of Gastrointestinal Pain

- D1. Centrally mediated abdominal pain syndrome (CAPS)

- D2. Narcotic bowel syndrome (NBS)/ Opioid-induced GI hyperalgesia

E. Gallbladder and Sphincter of Oddi disorders

- E1. Biliary pain

- E1a. Functional gallbladder disorder

- E1b. Functional biliary sphincter of Oddi disorder

- E2. Functional pancreatic sphincter of Oddi disorder

F. Anorectal Disorders

- F1. Fecal incontinence

- F2. Functional anorectal pain

- F2a. Levator ani syndrome

- F2b. Unspecified functional anorectal pain

- F2c. Proctalgia fugax

- F3. Functional defecation disorders

- F3a. Inadequate defecatory propulsion

- F3b. Dyssynergic defecation

G. Childhood Functional GI Disorders: Neonate/Toddler

- G1. Infant regurgitation

- G2. Rumination syndrome

- G3. Cyclic vomiting syndrome (CVS)

- G4. Infant colic

- G5. Functional diarrhea

- G6. Infant dyschezia

- G7. Functional constipation

H. Childhood Functional GI Disorders: Child/Adolescent

- H1. Functional nausea and vomiting disorders

- H1a. Cyclic vomiting syndrome (CVS)

- H1b. Functional nausea and functional vomiting

- H1b1. Functional nausea

- H1b2. Functional vomiting

- H1c. Rumination syndrome

- H1d. Aerophagia

- H2. Functional abdominal pain disorders

- H2a. Functional dyspepsia

- H2a1. Postprandial distress syndrome

- H2a2. Epigastric pain syndrome

- H2b. Irritable bowel syndrome (IBS)

- H2c. Abdominal migraine

- H2d. Functional abdominal pain ‒ NOS

- H3. Functional defecation disorders

- H3a. Functional constipation

- H3b. Nonretentive fecal incontinence

Functional gastrointestinal disorders are very common. Globally, irritable bowel syndrome and functional dyspepsia alone may affect 16–26% of the population.

Signs and symptoms may include a sudden pain in the epigastrium to the right of the midline indicating the perforation of a duodenal ulcer. In a gastric ulcer perforation creates a history of burning pain in epigastrium, with flatulence and dyspepsia.

In intestinal perforation, pain starts from the site of perforation and spreads across the abdomen.

Gastrointestinal perforation results in severe abdominal pain intensified by movement, nausea, vomiting and hematemesis. Later symptoms include fever and or chills. In any case, the abdomen becomes rigid with tenderness and rebound tenderness. After some time the abdomen becomes silent and heart sounds can be heard all over. Patient stops passing flatus and motion, abdomen is distended.

The symptoms of esophageal rupture may include sudden onset of chest pain.

Underlying causes include gastric ulcers, duodenal ulcers, appendicitis, gastrointestinal cancer, diverticulitis, inflammatory bowel disease, superior mesenteric artery syndrome, trauma and ascariasis. Typhoid fever, non-steroidal anti-inflammatory drugs, ingestion of corrosives may also be responsible.

Postcholecystectomy syndrome describes the presence of abdominal symptoms after surgical removal of the gallbladder (cholecystectomy), 2 years after the surgery.

Symptoms of postcholecystectomy syndrome may include:

- Dyspepsia, nausea, and vomiting.

- Flatulence, bloating, and diarrhea.

- Persistent pain in the upper right abdomen.

Symptoms occur in about 5 to 40 percent of patients who undergo cholecystectomy, and can be transient, persistent or lifelong. The chronic condition is diagnosed in approximately 10% of postcholecystectomy cases.

The pain associated with postcholecystectomy syndrome is usually ascribed to either sphincter of Oddi dysfunction or to post-surgical adhesions. A recent study shows that postcholecystectomy syndrome can be caused by biliary microlithiasis.

Approximately 50% of cases are due to biliary causes such as remaining stone, biliary injury, dysmotility, and choledococyst. The remaining 50% are due to non-biliary causes. This is because upper abdominal pain and gallstones are both common but are not always related.

Chronic diarrhea in postcholecystectomy syndrome is a type of bile acid diarrhea (type 3). This can be treated with a bile acid sequestrant like cholestyramine, colestipol or colesevelam, which may be better tolerated.

Some individuals may benefit from diet modification, such as a reduced fat diet, following cholecystectomy. The liver produces bile and the gallbladder acts as reservoir. From the gallbladder, bile enters the intestine in individual portions. In the absence of gallbladder, bile enters the intestine constantly, but in small quantities. Thus, it may be insufficient for digestion of fatty foods. Postcholecystectomy syndrome treatment depends on the identified violations that led to it. Typically, the patient is recommended dietary restriction table with fatty foods, enzyme preparations, antispasmodics, sometimes cholagogue.

If the pain is caused by biliary microlithiasis, oral ursodeoxycholic acid can alleviate the condition.

A trial of bile acid sequestrant therapy is recommended for bile acid diarrhoea.

Food intolerance is more chronic, less acute, less obvious in its presentation, and often more difficult to diagnose than a food allergy.

Symptoms of food intolerance vary greatly, and can be mistaken for the symptoms of a food allergy. While true allergies are associated with fast-acting immunoglobulin IgE responses, it can be difficult to determine the offending food causing a food intolerance because the response generally takes place over a prolonged period of time. Thus, the causative agent and the response are separated in time, and may not be obviously related. Food intolerance symptoms usually begin about half an hour after eating or drinking the food in question, but sometimes symptoms may be delayed by up to 48 hours.

Food intolerance can present with symptoms affecting the skin, respiratory tract, gastrointestinal tract (GIT) either individually or in combination. On the skin may include skin rashes, urticaria (hives), angioedema, dermatitis, and eczema. Respiratory tract symptoms can include nasal congestion, sinusitis, pharyngeal irritations, asthma and an unproductive cough. GIT symptoms include mouth ulcers, abdominal cramp, nausea, gas, intermittent diarrhea, constipation, irritable bowel syndrome (IBS),

and may include anaphylaxis.

Food intolerance has been found associated with irritable bowel syndrome and inflammatory bowel disease, chronic constipation, chronic hepatitis C infection, eczema, NSAID intolerance, respiratory complaints, including asthma, rhinitis and headache, functional dyspepsia, eosinophilic esophagitis

and ENT illnesses.

A Low FODMAP diet now has an evidence base sufficiently strong to recommend its widespread application in conditions such as IBS and IBD. Restriction of Fermentable Oligo-, Di- and Mono-

saccharides and Polyols globally, rather than individually, controls the symptoms of functional gut disorders (e.g. IBS), and the majority of IBD patients respond just as well. It is more successful than restricting only Fructose and Fructans, which are also FODMAPs, as is recommended for those with Fructose malabsorption. Longer term compliance with the diet was high.

A randomised controlled trial on IBS patients found relaxing an IgG-mediated food intolerance diet led to a 24% greater deterioration in symptoms compared to those on the elimination diet and concluded food elimination based on IgG antibodies may be effective in reducing IBS symptoms and is worthy of further biomedical research.

Intestinal or bowel hyperpermeability, so called leaky gut, has been linked to food allergies and some food intolerances. Research is currently focussing on specific conditions and effects of certain food constituents. At present there are a number of ways to limit the increased permeability, but additional studies are required to assess if this approach reduces the prevalence and severity of specific conditions.

The main symptom of dysmenorrhea is pain concentrated in the lower abdomen or pelvis. It is also commonly felt in the right or left side of the abdomen. It may radiate to the thighs and lower back.

Symptoms often co-occurring with menstrual pain include nausea and vomiting, diarrhea or constipation, headache, dizziness, disorientation, hypersensitivity to sound, light, smell and touch, fainting, and fatigue. Symptoms of dysmenorrhea often begin immediately after ovulation and can last until the end of menstruation. This is because dysmenorrhea is often associated with changes in hormonal levels in the body that occur with ovulation. The use of certain types of birth control pills can prevent the symptoms of dysmenorrhea because they stop ovulation from occurring.

Functional somatic syndrome is characterized by ambiguous, non-specific symptoms that appear in otherwise-healthy populations. Overlap exists in different syndromes, including gastrointestinal issues, pain, fatigue, cognitive difficulties, and sleep difficulties. Some have proposed to group symptoms into clusters or into one general functional somatic disorder given the finding of correlations between symptoms and underlying etiologies.

Functional somatic syndrome is a term used to refer to physical symptoms that are poorly explained. It encompass disorders such as chronic fatigue syndrome, fibromyalgia, chronic widespread pain, temporomandibular disorder, irritable bowel syndrome, lower back pain, tension headache, atypical face pain, non-cardiac chest pain, insomnia, palpitation, dyspepsia, and dizziness. General overlap exists between this term, somatization, and somatoform.

Dysmenorrhea, also known as painful periods, or menstrual cramps, is pain during menstruation. Its usual onset occurs around the time that menstruation begins. Symptoms typically last less than three days. The pain is usually in the pelvis or lower abdomen. Other symptoms may include back pain, diarrhea, or nausea.

In young women painful periods often occur without an underlying problem. In older women it is more often due to an underlying issues such as uterine fibroids, adenomyosis, or endometriosis. It is more common among those with heavy periods, irregular periods, whose periods started before twelve years of age, or who have a low body weight. A pelvic exam in those who are sexually active and ultrasound may be useful to help in diagnosis. Conditions that should be ruled out include ectopic pregnancy, pelvic inflammatory disease, interstitial cystitis, and chronic pelvic pain.

Dysmenorrhea occurs less often in those who exercise regularly and those who have children early in life. Treatment may include the use of a heating pad. Medications that may help include NSAIDs such as ibuprofen, hormonal birth control, and the IUD with progestogen. Taking vitamin B or magnesium may help. Evidence for yoga, acupuncture, and massage is insufficient. Surgery may be useful if certain underlying problems are present.

Dysmenorrhea is estimated to occur in 20% to 90% of women of reproductive age. It is the most common menstrual disorder. Typically it starts within a year of the first menstrual period. When there is no underlying cause often the pain improves with age or following having a child.

The primary symptoms of hypotension are lightheadedness or dizziness.

If the blood pressure is sufficiently low, fainting may occur.

Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than effects of hypotension:

- chest pain

- shortness of breath

- irregular heartbeat

- fever higher than 38.3 °C (101 °F)

- headache

- stiff neck

- severe upper back pain

- cough with sputum

- Prolonged diarrhea or vomiting

- dyspepsia (indigestion)

- dysuria (painful urination)

- adverse effect of medications

- acute, life-threatening allergic reaction

- seizures

- loss of consciousness

- profound fatigue

- temporary blurring or loss of vision

- Black tarry stools

From 1869, neurasthenia became a "popular" diagnosis, expanding to include such symptoms as weakness, dizziness and fainting, and a common treatment was the rest cure, especially for women, who were the gender primarily diagnosed with this condition at that time. Recent analysis, however, of data from this period gleaned from the Annual Reports of Queen Square Hospital, London, indicates that the diagnosis was more evenly balanced between the sexes than is commonly thought. Virginia Woolf was known to have been forced to have rest cures, which she describes in her book "On Being Ill". Charlotte Perkins Gilman's protagonist in "The Yellow Wallpaper" also suffers under the auspices of rest cure doctors, much as Gilman herself did. Marcel Proust was said to suffer from neurasthenia. To capitalize on this epidemic, the Rexall drug company introduced a medication called 'Americanitis Elixir' which claimed to be a soother for any bouts related to Neurasthenia.

The condition was explained as being a result of exhaustion of the central nervous system's energy reserves, which Beard attributed to modern civilization. Physicians in the Beard school of thought associated neurasthenia with the stresses of urbanization and with stress suffered as a result of the increasingly competitive business environment. Typically, it was associated with upper class people and with professionals working in sedentary occupations, but really can apply to anyone who lives within the monetary system.

Freud included a variety of physical symptoms in this category, including fatigue, dyspepsia with flatulence, and indications of intra-cranial pressure and spinal irritation. In common with some other people of the time, he believed this condition to be due to "non-completed coitus" or the non-completion of the higher cultural correlate thereof, or to "infrequency of emissions" or the infrequent practice of the higher cultural correlate thereof. Later, Freud formulated that in cases of coitus interruptus as well as in cases of masturbation, there was "an insufficient libidinal discharge" that had a poisoning effect on the organism, in other words, neurasthenia was the result of (auto-)intoxication. Eventually he separated it from anxiety neurosis, though he believed that a combination of the two conditions existed in many cases.

The symptoms of pernicious anemia come on slowly. Untreated, it can lead to neurological complications, and in serious cases, death. Many of the signs and symptoms are due to anemia itself, when anemia is present. Symptoms may consist of the triad of tingling or other skin sensations (paresthesia), tongue soreness (glossitis), and fatigue and general weakness. It presents with a number of further common symptoms, including depressive mood, low-grade fevers, diarrhea, dyspepsia, weight loss, neuropathic pain, jaundice, sores at the corner of the mouth (angular cheilitis), a look of exhaustion with pale and dehydrated or cracked lips and dark circles around the eyes, as well as brittle nails, and thinning and early greying of the hair. Because PA may affect the nervous system, symptoms may also include difficulty in proprioception, memory changes, mild cognitive impairment (including difficulty concentrating and sluggish responses, colloquially referred to as brain fog), and even psychoses, impaired urination, loss of sensation in the feet, unsteady gait, difficulty in walking, muscle weakness and clumsiness. Anemia may also lead to tachycardia (rapid heartbeat), cardiac murmurs, a yellow waxy pallor, altered blood pressure (low or high), and a shortness of breath (known as "the sighs"). The deficiency also may present with thyroid disorders. In severe cases, the anemia may cause evidence of congestive heart failure. A complication of severe chronic PA is subacute combined degeneration of spinal cord, which leads to distal sensory loss (posterior column), absent ankle reflex, increased knee reflex response, and extensor plantar response. Other than anemia, hematological symptoms may include cytopenias, intramedullary hemolysis, and pseudothrombotic microangiopathy. Pernicious anemia can contribute to a delay in physical growth in children, and may also be a cause for delay in puberty for adolescents.

A normal menstrual cycle is 21–35 days in duration, with bleeding lasting an average of 5 days and total blood flow between 25 and 80 mL. Menorrhagia is defined as total menstrual flow >80ml per cycle, or soaking a pad/tampon every 2 hours or less. Deviations in terms of frequency of menses, duration of menses, or volume of menses qualifies as abnormal uterine bleeding. Bleeding in between menses is also abnormal uterine bleeding and thus requires further evaluation.

Complications of Menorrhagia could also be the initial symptoms. Excessive bleeding can lead to anemia which presents as fatigue, shortness of breath, and weakness. Anemia can be diagnosed with a blood test.

Orthostatic hypotension, also called "postural hypotension", is a common form of low blood pressure. It occurs after a change in body position, typically when a person stands up from either a seated or lying position. It is usually transient and represents a delay in the normal compensatory ability of the autonomic nervous system. It is commonly seen in hypovolemia and as a result of various medications. In addition to blood pressure-lowering medications, many psychiatric medications, in particular antidepressants, can have this side effect. Simple blood pressure and heart rate measurements while lying, seated, and standing (with a two-minute delay in between each position change) can confirm the presence of orthostatic hypotension. Orthostatic hypotension is indicated if there is a drop in 20 mmHg of systolic pressure (and a 10 mmHg drop in diastolic pressure in some facilities) and a 20 beats per minute increase in heart rate.

Vasovagal syncope is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position. Vasovagal syncope occurs as a result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system .

Another, but rarer form, is postprandial hypotension, a drastic decline in blood pressure that occurs 30 to 75 minutes after eating substantial meals. When a great deal of blood is diverted to the intestines (a kind of "splanchnic blood pooling") to facilitate digestion and absorption, the body must increase cardiac output and peripheral vasoconstriction to maintain enough blood pressure to perfuse vital organs, such as the brain. Postprandial hypotension is believed to be caused by the autonomic nervous system not compensating appropriately, because of aging or a specific disorder.

Hypotension is a feature of Flammer syndrome which is characterized by cold hands and feet and predisposes to normal tension glaucoma.

Menorrhagia is a menstrual period with excessively heavy flow and falls under the larger category of abnormal uterine bleeding (AUB).

Abnormal uterine bleeding can be caused by structural abnormalities in the reproductive tract, anovulation, bleeding disorders, hormone issues (such as hypothyroidism) or cancer of the reproductive tract. Initial evaluation aims at figuring out pregnancy status, menopausal status, and the source of bleeding.

Treatment depends on the cause, severity, and interference with quality of life. Initial treatment often involve contraceptive pills. Surgery can be an effective second line treatment for those women whose symptoms are not well-controlled. Approximately 53 in 1000 women are affected by AUB.