Chronic diarrhea overview

# Overview
Chronic diarrhea is a common symptom of many conditions and has an estimated prevalence of 5%. Although chronic diarrhea has multiple definitions, a current working definition is the production of loose stools for longer than 4 weeks. Frequent defecation with normal consistency is termed psuedodiarrhea. There are 3 basic categories of chronic diarrhea: watery, fatty (malabsorption), and inflammatory (with blood and pus). The fundamental pathophysiology of all diarrhea is altered intestinal water and electrolyte transport caused by several factors majorly dependent on the socioeconomic status of the population. If left untreated, patients with chronic diarrhea may progress to develop symptoms of altered sensorium due to electrolyte imbalance, dehydration, and malnutrition. Common complications of chronic diarrhea include confusion, perforated bowels, sepsis, and death. Prognosis is generally good when the underlying cause is identified and treated early. The laboratory findings in chronic diarrhea include complete blood count to evaluate for anemia and abnormal white blood cell count, electrolytes, thyroid function tests, serology testing for celiac disease, and stool analysis for fecal leukocytes, fecal lactoferrin, and fecal occult blood. Treatment is targeted at treating the underlying cause of the diarrhea.

# Historical Perspective
The word "diarrhea" was coined by Hippocrates. Diarrhea is derived from the Greek term "to flow through." Diarrhea is a common manifestation of gastrointestinal disease.

# Classification
Chronic diarrhea may be classified into 3 basic categories: watery, fatty (malabsorption), and inflammatory (with blood and pus). It is important to note that not all chronic diarrhea falls into one category alone. Classifying a patient's chronic diarrhea into a subcategory helps to direct the diagnostic workup.

# Pathophysiology
The fundamental pathophysiology of all diarrhea is incomplete absorption of water from the lumen because of either a reduced rate of net water absorption or osmotic retention of water intraluminally. The causes of chronic diarrhea include inflammatory, osmotic, secretory, iatrogenic, motility, and functional diseases. Osmotic chronic diarrhea involves an unabsorbed substance that draws water from the plasma into the intestinal lumen along osmotic gradients. If excessive amounts of unabsorbed substance are retained in the intestinal lumen, water will not be absorbed and diarrhea will result. Secretory chronic diarrhea on the other hand, results from disordered electrolyte transport and, despite the term, is more commonly caused by decreased absorption rather than net secretion. A disruption of the normal colonic epithelial barrier by microorganisms is mainly responsible for inflammatory chronic diarrhea. This disruption can lead to exudative, secretory, or malabsorptive components of inflammatory chronic diarrhea. Both rapid transit time and slow transit time are associated with motility disorders causing chronic diarrhea. Some iatrogenic causes of chronic diarrhea are seen after abdominal surgeries such as cholecystectomy, where about 5%10% of patients develop chronic diarrhea. In general, the causes of chronic diarrhea are multifactorial.

# Causes
Depending on the socioeconomic status of the population, chronic diarrhea can be caused by several factors. In a developing nation, the most likely causes of chronic diarrhea are mycobacterial and parasitic infections, while functional disorders such as malabsorption and inflammatory bowel diseases are less likely causes. In a developed nation, however, the most likely causes of diarrhea are irritable bowel syndrome (IBS), inflammatory bowel disease, malabsorption syndromes (such as lactose intolerance and celiac disease), and chronic infections (particularly in patients who are immunocompromised).

# Differentiating Chronic Diarrhea from other Conditions
The differential diagnosis for chronic diarrhea is enormous, with a large number of diagnostic tests available that can be used to evaluate these patients. Classifying a patient's chronic diarrhea into a subcategory such as watery, fatty, and inflammatory helps to direct the diagnostic workup. Some watery causes of chronic diarrhea which should be differentiated from one another include Crohn's disease, hyperthyroidism, VIPoma, lactose intolerance, celiac disease, and irritable bowel syndrome (IBS). The causes of fatty diarrhea that should be differentiated from one another include celiac sprue, pancreatic insufficiency, bacterial overgrowth, and maldigestion problems which results from pancreatic exocrine insufficiencyy. Finally, the inflammatory causes of chronic diarrhea such as diverticulitis, ulcerative colitis, and entamoeba histolytica must also be differentiated.

# Epidemiology and Demographics
In developed countries, the prevalence of chronic diarrhea is estimated to be about 300-500 per 100,000 persons. In any given year, about 35% of the population has diarrhea lasting more than 1 month.

# Risk Factors
The risk factors of chronic diarrhea can be assessed based on epidemiological associations and the patient's characteristics. Some of these factors can be classified based on travel history, epidemics and outbreaks, patients with acquired immune deficiency syndrome, and whether the patients are institutionalized or hospitalized.

# Natural History, Complications, and Prognosis
If left untreated, patients with chronic diarrhea may progress to develop symptoms of altered sensorium due to electrolyte imbalance, dehydration, and malnutrition. Common complications of chronic diarrhea include confusion, perforated bowels, sepsis, and death. Prognosis is generally good when the underlying cause is identified and treated early.

# Diagnosis
There are no criteria for the diagnosis of chronic diarrhea. However, in order to make an accurate diagnosis, it is important to take a detailed history and a physical exam from an expert's opinion and from experience in individual clinical centers. The use of these methods is subject to bias; however, a specific diagnosis can be achieved in more than 90% of patients.

## History and Symptoms
Obtaining the history of a patient is the most important aspect of making a diagnosis of chronic diarrhea. Specific histories about the symptoms (duration, onset, progression), associated symptoms, and drug usage have to be obtained. The hallmark of chronic diarrhea is loose stools lasting for 4 weeks or more. A positive history of foul smelling stools that are difficult to flush, bloody loose bowel movements, and cramping abdominal pain are suggestive of chronic diarrhea. The most common symptoms of chronic diarrhea include cramping abdominal pain, elevation in body temperature, and increased frequency of bowel movements.

## Physical Examination
Some of the physical findings of chronic diarrhea are orthostatic hypotension, dehydration, neuropathy, muscle wasting, edema, malnutrition, urticaria pigmentosa, dermatographism, pinch purpura, macroglossia, hyperpigmentation, Addison's disease, and migratory necrotizing erythema.

## Laboratory Findings
The laboratory findings in chronic diarrhea include complete blood count to evaluate for anemia and abnormal white blood cell count, electrolytes, thyroid function tests, serology testing for celiac disease, and stool analysis for fecal leukocytes, fecal lactoferrin, and fecal occult blood. Some other diagnostic studies that have been adopted in the diagnosis of chronic diarrhea include flexible sigmoidoscopy, colonoscopy, esophagogastroduodenoscopy, and capsule endoscopy.

## Electrocardiogram
There are no electrocardiogram findings associated with chronic diarrhea.

## Chest X-Ray
There are no chest x-ray findings associated with chronic diarrhea.

## CT Scan
There are no CT findings associated with chronic diarrhea.

## Other Imaging Findings
There are no additional imaging findings for chronic diarrhea.

# Treatment

## Medical Therapy
Medications are the mainstay of treatment; the treatment of chronic diarrhea is targeted at treating the underlying cause. Antidiarrheal drugs, which act by improving stool consistency, reducing stool frequency, or reducing stool weight, are mainly employed for symptomatic treatment.

## Surgery
Surgery is not the first-line treatment option for patients with chronic diarrhea. Surgical intervention is usually reserved for patients who have failed all medical therapy and when malignancy is suspected on biopsy as the cause of the chronic diarrhea.

## Prevention
The primary and secondary prevention methods of chronic diarrhea are the same.