CHAPTER 11 Diarrhea

Next to respiratory disease, acute gastroenteritis is the most common illness in families in the United States. Most cases are of viral origin and are self-limiting. In children, 50% are of viral origin, approximately 25% are of bacterial origin, and approximately 25% are of undetermined cause. Diarrhea can be classified according to its pathophysiological pattern (osmotic, secretory, exudative, or motile), its cause (infectious or noninfectious), or its duration (acute or chronic).

Osmotic or malabsorptive diarrhea occurs when nonabsorbable water-soluble solutes remain in the bowel and retain water. This can occur through damage to the intestinal microvillus membrane. The result is malabsorption of luminal solutes with osmotic loss of free water into the gut lumen. This is the most common cause of chronic diarrhea in children. Lactose intolerance is an example of this kind of diarrhea. Ingestion of large amounts of sugar substitutes in diet foods, drinks, candies, and chewing gum can cause osmotic diarrhea through a combination of slow absorption and rapid small bowel motility.

Secretory diarrhea occurs when the balance between fluid secretion and absorption across the intestinal mucosa is altered. When there is a change in this balance produced by physiological causes, diarrhea occurs. The loss of water and electrolytes can be rapid and massive. Traveler’s diarrhea and diarrhea caused by Vibrio cholerae are examples.

Exudative diarrhea occurs in the presence of mucosal inflammation or ulceration, which results in an outpouring of plasma, serum proteins, blood, and mucus. The consequence is an increase in fecal bulk and fluidity. Many mucosal diseases, such as regional enteritis, ulcerative colitis, and carcinoma, can cause this exudative enteropathy.

Diarrhea from abnormal intestinal motility (either increased or decreased) results in an alteration in contact between the luminal contents and the mucosal surface. Examples include irritable bowel syndrome (IBS) and laxative use.

Infectious bacteria can be caused by viral, bacterial, or parasitic agents.

Diagnostic reasoning: focused history

What does this patient mean by “diarrhea”?

Key questions

How frequent are the stools?

What is the volume of stools?

Are the stools formed or liquid?

At what intervals does the diarrhea occur?

Frequency of stools

In the United States, typical bowel frequency ranges from 1 to 3 times a day to 2 or 3 times per week and varies considerably from person to person. Changes in stool frequency, consistency, or volume can indicate disease.

Stool volume and consistency

Processes involving the small bowel tend to produce large-volume watery stools that are relatively infrequent. Large bowel involvement, usually resulting from a bacterially induced inflammatory process, tends to produce more frequent and less watery stools.

Intervals

A history of acute diarrhea followed by continuous or intermittent episodes of loose stools suggests malabsorption commonly caused by lactase deficiency exacerbated by the ingestion of lactose in milk or milk products. Intermittent diarrhea alternating with constipation suggests IBS.

Proximal colon symptoms

Proximal colon symptoms include large-volume, less-frequent, more-homogeneous stools, without urgency or tenesmus (painful defecation), and suggest food intolerance or infectious or inflammatory disease.

Distal colon symptoms

Symptoms of small volume, frequency, urgency, tenesmus, incontinence, and mucus suggest proctocolitis, colon cancer, diverticular disease, or IBS.

If this is an infant, is there a risk of dehydration?

Key questions

How many wet diapers has the infant produced in the past 24 hours?

Does the infant seem thirsty?

Does the infant have tears when crying?

Wet diapers

Dehydration in infants and young children can occur quickly and with fatal consequences, especially in infants. Diagnosis and treatment must be done in a timely manner. A general rule of thumb to determine signs of dehydration in infants is fewer than six wet diapers per 24 hours or a period of longer than 4 hours without urination.

Thirst

Infants demonstrate their thirst with irritability, crying, and eagerness to drink fluid that is offered to them. Test for thirst by offering fluids either in a bottle or on a spoon. The child with mild dehydration will exhibit increased thirst; the moderately dehydrated child will be very thirsty; and, with severe dehydration, the child will continue to be very thirsty. If left untreated, a child can become stuporous and unresponsive and therefore unable to manifest thirst.

Tears

In mild dehydration, tears are present; in moderate dehydration, tears are or are not present; and in severe dehydration, no tears are present.

If this is an adult, is there risk for dehydration?

Key questions

How many times have you urinated in the past 24 hours?

Are you thirsty?

Do you have a dry mouth or dry eyes?

Dehydration

Symptoms of dehydration in an adult are more related to the rate of fluid loss than to the absolute degree of fluid loss. The degree of dehydration can be estimated by symptoms of thirst, dry mouth, or dry eyes, and by frequency and volume of urination. Patients can also experience weakness.

Is this an acute or chronic problem?

Key questions

How long have you had diarrhea?

Have you had this problem before?

Acute diarrhea in adults

An acute onset of diarrhea in a previously healthy patient without signs or symptoms of other organ involvement suggests an infectious cause. Acute diarrhea in adults is commonly viral in origin. The viral illnesses are self-limited, and an aggressive diagnostic workup is not indicated. Acute diarrhea in adults usually has an abrupt onset and lasts less than 2 weeks. Most of the disorders cause some combination of abdominal pain, diarrhea, nausea, vomiting, fever, and tenesmus.

Acute diarrhea in children

Acute diarrhea in children is characterized by loose or liquid stools. A large quantity of fluid and electrolytes that become pooled in the intestinal lumen is lost as stool is expelled. The number of stools is usually increased, but this is not an essential manifestation. Severe or protracted diarrhea can lead to metabolic acidosis, dehydration, azotemia, and oliguria. Diarrhea in the neonate and young infant is considered more serious than that in the older child because of lower tolerance to associated fluid shifts and the greater likelihood of associated infection or congenital anomaly.

Chronic diarrhea in adults

Diarrhea is chronic when it lasts more than 2 weeks. Unless the diarrhea is bloody or the patient has a systemic illness, the most common causes of chronic diarrhea are parasites, medications, IBS, lactose intolerance, and inflammatory bowel disease.

Chronic diarrhea in children

Chronic diarrhea in children is defined as diarrhea for longer than 3 weeks. The major causes of diarrhea change with age. In the infant, formula protein intolerance is the most common cause. Toddler’s diarrhea (irritable colon of infancy), protracted enteritis following a viral infection, and Giardia are the common causes in the toddler. In children and adolescents, malabsorption disorders are the most common causes. The diarrhea is the result of the ingestion of solutes that cannot be digested or absorbed, such as lactose products or excessive intake of sorbitol. Another cause of diarrhea in this age-group is inflammatory bowel disease (ulcerative colitis and Crohn disease).

Does the presence or absence of blood help me narrow the cause?

Key questions

Is there any noticeable blood in the stool or tissue? How much?

What color is the blood?

What color are the stools?

Blood in the stools

Bright red blood limited to small spots on the toilet tissue suggests that the source of bleeding is from hemorrhoids and not from a diarrheal process higher in the gastrointestinal (GI) tract. Because diarrhea and repeated cleansing of the rectum produce local irritation, minor bleeding from hemorrhoids is not uncommon and must be distinguished from true blood in the stool. Reports of blood in the stool in acute diarrhea are suggestive of a bacterial pathogen, notably Shigella. The blood is red.

In infants and children, blood in the stool is most commonly caused by cow’s milk intolerance or anal fissures. In the newborn, blood in stools can be a result of hemorrhagic disease of the newborn, thought to be caused by a lack of vitamin K. Premature infants or infants who are of low birth weight are at risk for necrotizing enterocolitis presenting with red or maroon stools (hematochezia) as well as vomiting and abdominal distention.

In adults and children, chronic bloody diarrhea can indicate inflammatory bowel disease, dysentery, colitis, or an invasive organism. Blood that is red usually indicates lower GI tract bleeding, whereas dark or black, tarry stools (melena) typically indicate upper GI tract bleeding. However, bleeding from the small bowel or right colon can also produce melena.

Color of stools

Some patients believe they have blood in their stool based on stool color. Sources of black stools are blood, iron, charcoal, bismuth, licorice, huckleberries, and lead. Sources of red or pink stools include blood, food (beets, cranberries, tomatoes, peppers), food coloring (breakfast cereals, Jell-O), and drugs (anticoagulants, salicylates, rifampin, pyridium pamoate, diazepam syrup, phenolphthalein in alkaline stool). Green-black stools can be caused by grape-flavored drinks and iron. Dark gray stools occur with cocoa and chocolate ingestion. Pale gray or white stools can be caused by cholestasis, obstructive jaundice, malabsorption, excessive milk ingestion, and antacid ingestion. Green stools are produced by bile salts and chlorophyll-containing vegetables, such as spinach.

What does the presence or absence of pain tell me?

Key questions

Are you having any pain or gas with the diarrhea?

Where is the pain?

What does the pain feel like?

Is the pain constant or does it come and go?

Does the pain awaken you at night?

Does the pain interfere with your activities (e.g., working, sleeping, eating)?

Occurrence of pain

Diarrhea with abdominal pain and flatulent stools is characteristic of a malabsorptive process. Most self-limiting viral diarrheas cause some combination of abdominal pain, diarrhea, nausea, vomiting, fever, and tenesmus.

Abdominal pain is common when diarrhea is caused by infective bacteria in the colon, such as ingestion associated with food poisoning. Giardia lamblia, introduced through the ingestion of contaminated water or by the orofecal route, produces crampy abdominal pain and is frequently seen in children and diapered infants in day care where handwashing is not done between diapering.

Location of pain

Generalized abdominal pain is produced by diffuse inflammation of the GI tract as occurs with inflammatory bowel disease or abdominal cramping from infective diarrhea. The pain from ulcerative colitis can be perceived over the entire abdomen or localized to the lower quadrants. The pain associated with IBS is usually confined to the lower quadrants or over the sigmoid colon. Large intestine pain is felt in the lower abdominal quadrants, whereas small intestine pain is felt in the epigastric and umbilical areas.

Severity of pain

Self-limited diarrhea usually presents with cramping but not severe abdominal pain. Other causes of abdominal pain should be investigated (see Chapter 2).

Sleep-related pain

Persistent diarrhea that awakens the patient from sleep usually indicates a serious organic disease, such as diabetes enteropathy or human immunodeficiency virus (HIV) enteropathy. The symptoms associated with IBS occur during the waking hours.

What do associated symptoms tell me?

Key questions

Do you have any fever? Did you take your temperature?

Do you have any vomiting?

What occurred first: the diarrhea or the vomiting?

Fever

Patients often report having a “fever” when they have such symptoms as facial flushing, shaking chills, headache, malaise or muscle aches, or a sensation of warmth. These symptoms are usually not validated by measuring body temperature with a thermometer. Fever is a cardinal manifestation of disease. GI tract and respiratory tract infections are responsible for 80% of febrile illnesses.

Vomiting

Vomiting is often present early in the course of viral gastroenteritis (especially the Norwalk virus), food poisoning, and food-borne bacterial infection. Vomiting is one of the main causes of dehydration in acute diarrhea. Also, small bowel processes commonly associated with viral agents cause delayed gastric emptying and luminal distention, which often induces vomiting before the onset of diarrhea.

Occurrence of vomiting and diarrhea

When diarrhea occurs before the vomiting, suspect a bacterial etiology.

Could this be caused by exposure to others or to contaminated food?

Key questions

If a child: Does the child attend day care?

If a child: Are any of the other children in day care ill?

Have you been around others who have similar symptoms?

Day care attendance

Children who attend day care are at greater risk of acquiring many bacterial infections transmitted through orofecal contamination and diapering.

Others with similar symptoms

It is common for food-borne infections to be acquired at social gatherings in which food is served; in this case, others at the gathering can become ill with similar symptoms. However, patients do not always know if others became ill, especially when the onset of diarrhea occurs 1 to 2 hours after food ingestion.

Could this be the result of exposure to animals?

Key questions

What pets do you have?

Have you had contact with or have you handled dogs, cats, or turtles?

Exposure to infectious agents through animal contact

Campylobacter jejuni infection can be acquired from infected dogs or cats. Infected turtles are a source of Salmonella.

Could this be caused by exposure to contaminated water?

Key question

Have you traveled recently? Where?

Recent travel

Travel outside of the United States carries the potential to acquire enterotoxigenic Escherichia coli or, less commonly, G. lamblia, Salmonella, Shigella, C. jejuni, or Entamoeba histolytica. Camping exposes individuals to Giardia and Campylobacter through untreated water. Outbreaks of diarrhea caused by Cryptosporidium have been linked to contaminated water in urban areas of the U.S.

Could sexual activities explain the diarrhea?

Key question

Do your sexual practices include anal sex?

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