2514 PART 10 Disorders of the Gastrointestinal System

physical findings, and some may not have any abdominal discomfort

early in the disease process. Soliciting an appropriate history requires

detecting and evaluating symptoms that might suggest alternative

diagnoses.

What is the classic history? Nonspecific complaints occur first.

Patients may notice changes in bowel habits or malaise and vague,

perhaps intermittent, crampy abdominal pain in the epigastric or periumbilical region. The pain subsequently migrates to the right lower

quadrant over 12–24 h, where it is sharper and can be definitively localized as transmural inflammation when the appendix irritates the parietal peritoneum. Parietal peritoneal irritation may be associated with

local muscle rigidity and stiffness. Patients with appendicitis will most

often observe that their nausea, if present, followed the development of

abdominal pain, which can help distinguish them from patients with

gastroenteritis, for example, in whom nausea occurs first. Emesis, if

present, also occurs after the onset of pain and is typically mild and

scant. Thus, timing of the onset of symptoms and the characteristics

of the patient’s pain and any associated findings must be rigorously

assessed. Anorexia is so common that the diagnosis of appendicitis

should be questioned in its absence.

Arriving at the correct diagnosis is even more challenging when

the appendix is not located in the right lower quadrant, in women of

childbearing age, and in the very young or elderly. Because the differential diagnosis of appendicitis is so broad, often the key question

to answer expeditiously is whether the patient has appendicitis or

some other condition that requires immediate operative intervention.

A major concern is that the likelihood of a delay in diagnosis is greater

if the appendix is unusually positioned. All patients should undergo a

rectal examination. An inflamed appendix located behind the cecum

or below the pelvic brim may prompt very little tenderness of the anterior abdominal wall.

Patients with pelvic appendicitis are more likely to present with

dysuria, urinary frequency, diarrhea, or tenesmus. They may only

experience pain in the suprapubic region on palpation or on rectal

or pelvic examination. A pelvic examination in women is mandatory

to rule out conditions affecting urogynecologic organs that can cause

abdominal pain and mimic appendicitis such as pelvic inflammatory

disease, ectopic pregnancy, and ovarian torsion. Interest in the ability

of various clinical scoring systems to predict appendicitis or the need

for imaging studies continues. However, none of the currently available

decision tools yet appear to be able to circumvent or obviate the need

for expert clinical opinion. The relative frequencies of some presenting

signs are displayed in Table 331-3.

Patients with simple appendicitis normally only appear mildly ill

with a pulse and temperature that are usually only slightly above normal. The provider should be concerned about other disease processes

beside appendicitis or the presence of complications such as perforation, phlegmon, or abscess formation if the temperature is >38.3°C

(~101°F) and if there are rigors.

Patients with appendicitis will be found to lie quite still to avoid

peritoneal irritation caused by movement, and some will report discomfort caused by a bumpy car ride on the way to the hospital or clinic,

coughing, sneezing, or other actions that replicate a Valsalva maneuver.

The entire abdomen should be examined systematically starting in an

area where the patient does not report discomfort if possible. Classically, maximal tenderness is identified where the appendix is most

often located—in the right lower quadrant at or near McBurney’s point,

which is approximately one-third of the way along a line originating at

the anterior iliac spine and running to the umbilicus. Gentle pressure

in the left lower quadrant may elicit pain in the right lower quadrant

if the appendix is located there. This is Rovsing’s sign (Table 331-4).

Evidence of parietal peritoneal irritation is often best elicited by gentle

abdominal percussion, jiggling the patient’s gurney or bed, or mildly

bumping the feet.

FIGURE 331-2 Locations of the appendix and cecum.

TABLE 331-2 Relative Frequency of Common Presenting Symptoms

SYMPTOMS FREQUENCY

Abdominal pain >95%

Anorexia >70%

Constipation 4–16%

Diarrhea 4–16%

Fever 10–20%

Migration of pain to right lower

quadrant

50–60%

Nausea >65%

Vomiting 50–75%

TABLE 331-3 Relative Frequency of Some Presenting Signs

SIGNS FREQUENCY

Abdominal tenderness >95%

Right lower quadrant tenderness >90%

Rebound tenderness 30–70%

Rectal tenderness 30–40%

Cervical motion tenderness 30%

Rigidity ~10%

Psoas sign 3–5%

Obturator sign 5–10%

Rovsing’s sign 5%

Palpable mass <5%

TABLE 331-4 Classic Signs of Appendicitis in Patients with

Abdominal Pain

MANEUVER FINDINGS

Rovsing’s sign Palpating in the left lower quadrant causes pain in

the right lower quadrant

Obturator sign Internal rotation of the hip causes pain, suggesting

the possibility of an inflamed appendix located in

the pelvis

Iliopsoas sign Extending the right hip causes pain along

posterolateral back and hip, suggesting retrocecal

appendicitis

2515Acute Appendicitis and Peritonitis CHAPTER 331

Atypical presentation and pain patterns are common, especially in

the very old or the very young. Diagnosing appendicitis in children can

be especially challenging because they tend to respond so dramatically

to stimulation and obtaining an accurate history may be difficult. In

addition, it is important to remember that the smaller omentum found

in children may be less likely to wall off an appendiceal perforation.

Observing the child in a quiet surrounding may be helpful.

Signs and symptoms of appendicitis can be subtle in the elderly

who may not react as vigorously to appendicitis as younger people.

Pain, if noticed, may be minimal and have originated in the right lower

quadrant or, otherwise, where the appendix is located. It may never

have been noticed to be intermittent, or there may only be significant

discomfort with deep palpation. Nausea, anorexia, and emesis may be

the predominant complaints. The rare patient may even present with

signs and symptoms of distal bowel obstruction secondary to appendiceal inflammation and phlegmon or abscess formation.

■ LABORATORY TESTING

Laboratory testing does not identify patients with appendicitis. The

white blood cell count is only mildly to moderately elevated in ~70%

of patients with simple appendicitis (with a leukocytosis of 10,000–

18,000 cells/μL). A “left shift” toward immature polymorphonuclear

leukocytes is present in >95% of cases. A sickle cell preparation may

be prudent to obtain in those of African, Spanish, Mediterranean, or

Indian ancestry. Serum amylase and lipase levels should be measured.

Urinalysis is indicated to help exclude genitourinary conditions that

may mimic acute appendicitis, but a few red or white blood cells may

be present as a nonspecific finding. However, an inflamed appendix

that abuts the ureter or bladder may cause sterile pyuria or hematuria.

Every woman of childbearing age should have a pregnancy test. Cervical cultures are indicated if pelvic inflammatory disease is suspected.

Anemia and guaiac-positive stools should raise concern about the

presence of other diseases or complications such as cancer.

■ IMAGING

Plain films of the abdomen are rarely helpful and so are not routinely

obtained unless the clinician is worried about other conditions such as

intestinal obstruction, perforated viscus, or ureterolithiasis. Less than

5% of patients will present with an opaque fecalith in the right lower

quadrant. The presence of a fecalith is not diagnostic of appendicitis,

although its presence in an appropriate location where the patient complains of pain is suggestive and is associated with a greater likelihood

of complications.

The effectiveness of ultrasonography as a tool to diagnosis appendicitis is highly operator dependent. Even in very skilled hands, the

appendix may not be visualized. Its overall sensitivity is 0.86, with a

specificity of 0.81. Ultrasonography, especially intravaginal techniques,

appears to be most useful for identifying pelvic pathology in women.

Ultrasonographic findings suggesting the presence of appendicitis

include wall thickening, an increased appendiceal diameter, and the

presence of free fluid. Current practice in many institutions is to first

perform ultrasonography and progress to other imaging studies only if

the findings are equivocal.

The sensitivity and specificity of CT are at least 0.94 and 0.95,

respectively. Thus, CT imaging, given its high negative predictive value,

may be helpful if the diagnosis is in doubt, although studies performed

early in the course of disease may not have any typical radiographic

findings. In patients where the diagnosis is uncertain, delaying operation at the time of presentation to obtain CT does not appear to

increase the risk of perforation. CT scanning is a superior method for

assessing the severity of acute appendicitis in the absence of peritoneal

findings indicative of perforation, abscess, or suspicion of an associated

malignancy.

Suggestive findings on CT examination include dilatation >6 mm

with wall thickening, a lumen that does not fill with enteric contrast,

and fatty tissue stranding or air surrounding the appendix, which suggests inflammation (Figs. 331-3 and 331-4). The presence of luminal

air or contrast is not consistent with a diagnosis of appendicitis. Furthermore, nonvisualization of the appendix is a nonspecific finding

that should not be used to rule out the presence of appendiceal or

periappendiceal inflammation.

■ SPECIAL PATIENT POPULATIONS

Appendicitis is the most common extrauterine general surgical emergency observed during pregnancy. Early symptoms of appendicitis

such as nausea and anorexia may be overlooked. Diagnosing appendicitis in pregnant patients may be especially difficult because as the

uterus enlarges the appendix may be pushed higher along the right

flank even to the right upper quadrant or because the gravid uterus

may obscure typical physical findings. Ultrasonography may facilitate

early diagnosis. A high index of suspicion is required because of the

effects of unrecognized and untreated appendicitis on the fetus. For

example, the fetal mortality rate is four times greater (from 5 to 20%)

in patients with perforation.

Immunocompromised patients may present with only mild tenderness and may have many other disease processes in their differential

diagnosis, including atypical infections from mycobacteria, Cytomegalovirus, or other fungi. Enterocolitis is a concern and may be present

in patients who present with abdominal pain, fever, and neutropenia

due to chemotherapy. CT imaging may be very helpful, although it is

FIGURE 331-3 Computed tomography with oral and intravenous contrast of acute

appendicitis. There is thickening of the wall of the appendix and periappendiceal

stranding (arrow).

FIGURE 331-4 Appendiceal fecalith (arrow).

2516 PART 10 Disorders of the Gastrointestinal System

important not to be overly cautious and delay operative intervention

for those patients who are believed to have appendicitis.

TREATMENT

Acute Appendicitis

In the absence of contraindications, most patients who have

strongly suggestive medical histories and physical examinations

with supportive laboratory findings are candidates for appendectomy. In many instances, imaging studies are not required but are

often obtained before surgical consultation is requested. Certainly,

imaging and further study are appropriate in patients whose evaluations are suggestive but not convincing.

CT may accurately indicate the presence of appendicitis or other

intraabdominal processes that warrant intervention. Whenever

the diagnosis is uncertain, it is prudent to observe the patient and

repeat the abdominal examination over 6–8 h. Any evidence of

progression is an indication for operation. Narcotics can be given

to patients with severe discomfort.

All patients should be fully prepared for surgery and have any

fluid and electrolyte abnormalities corrected. Either laparoscopic

or open appendectomy is a satisfactory choice for patients with

uncomplicated appendicitis, although most procedures are now

performed in a minimally invasive fashion to the patient’s benefit

in terms of recovery time and complications. Management of those

who present with a mass representing a phlegmon or abscess can

be more difficult. Such patients are best served by treatment with

broad-spectrum antibiotics, drainage if there is an abscess >3 cm

in diameter, and parenteral fluids and bowel rest if they appear

to respond to conservative management. The appendix can then

be more safely removed 6–12 weeks later when inflammation has

diminished.

Laparoscopic appendectomy now accounts for the majority of all

appendectomies performed in Western cultures and is associated

with less postoperative pain, shorter lengths of stay, faster return to

normal activity, and likely fewer superficial wound complications,

although the risk of intraabdominal abscess formation may be

higher.

A laparoscopic approach may also be useful when the exact

diagnosis is uncertain. A laparoscopic approach may also facilitate

exposure in those who are very obese. Absent complications, most

patients can be discharged within 24–40 h of operation. The most

common postoperative complications are fever and leukocytosis.

Continuation of these findings beyond 5 days should raise concern

for the presence of an intraabdominal abscess. The mortality rate

for uncomplicated, nonperforated appendicitis is 0.1–0.5%, which

approximates the overall risk of general anesthesia. The mortality

rate for perforated appendicitis or other complicated disease is

much higher, ranging from 3% overall to as high as 15% in the

elderly.

ACUTE PERITONITIS

Acute peritonitis, or inflammation of the visceral and parietal peritoneum, is most often but not always infectious in origin, resulting from

perforation of a hollow viscus. This is called secondary peritonitis, as

opposed to primary or spontaneous peritonitis, when a specific intraabdominal source cannot be identified. In either instance, the inflammation can be localized or diffuse.

■ ETIOLOGY

Infective organisms may contaminate the peritoneal cavity after

spillage from a hollow viscus, because of a penetrating wound of the

abdominal wall, or because of the introduction of a foreign object like

a peritoneal dialysis catheter or port that becomes infected. Secondary

peritonitis most commonly results from perforation of the appendix, colonic diverticula, or the stomach and duodenum. It may also

occur as a complication of bowel infarction or incarceration, cancer,

inflammatory bowel disease, and intestinal obstruction or volvulus.

Conditions that may cause secondary bacterial peritonitis and their

mechanisms are listed in Table 331-5. Over 90% of the cases of primary

or spontaneous bacterial peritonitis occur in patients with ascites or

hypoproteinemia (<1 g/L).

Aseptic peritonitis is most commonly caused by the abnormal

presence of physiologic fluids such as gastric juice, bile, pancreatic

enzymes, blood, or urine. It can also be caused by the effects of normally sterile foreign bodies such as surgical sponges or instruments.

More rarely, it occurs as a complication of systemic diseases such as

lupus erythematosus, porphyria, and familial Mediterranean fever. The

chemical irritation caused by stomach acid and activated pancreatic

enzymes is extreme, and secondary bacterial infection may occur.

■ CLINICAL FEATURES

The cardinal signs and symptoms of peritonitis are acute, typically

severe, abdominal pain with tenderness and fever. How patients’

complaints of pain are manifested depends on their overall physical

health and whether the inflammation is diffuse or localized. Elderly

and immunosuppressed patients may not respond as aggressively to

the irritation. Diffuse, generalized peritonitis is most often recognized

as diffuse abdominal tenderness with local guarding, rigidity, and other

evidence of parietal peritoneal irritation. Physical findings may only

be identified in a specific region of the abdomen if the intraperitoneal

inflammatory process is limited or otherwise contained as may occur

in patients with uncomplicated appendicitis or diverticulitis. Bowel

sounds are usually absent to hypoactive.

Most patients present with tachycardia and signs of volume depletion with hypotension. Laboratory testing typically reveals a significant

leukocytosis, and patients may be severely acidotic. Radiographic studies may show dilatation of the bowel and associated bowel wall edema.

Free air or other evidence of leakage requires attention and could

represent a surgical emergency. In stable patients in whom ascites is

present, diagnostic paracentesis is indicated, where the fluid is tested

for protein and lactate dehydrogenase and the cell count is measured.

■ THERAPY AND PROGNOSIS

Whereas mortality rates can be <10% for reasonably healthy patients

with relatively uncomplicated, localized peritonitis, mortality rates

>40% have been reported for the elderly or immunocompromised.

Successful treatment depends on correcting any electrolyte abnormalities, restoration of fluid volume and stabilization of the cardiovascular

system, appropriate antibiotic therapy, and surgical correction of any

underlying abnormalities.

Acknowledgment

The wisdom and expertise of Dr. William Silen is gratefully acknowledged in this updated chapter on acute appendicitis and peritonitis.

TABLE 331-5 Conditions Leading to Secondary Bacterial Peritonitis

Bowel perforation

 Appendicitis trauma (blunt or

penetrating)

Anastomotic leakage

Adhesion

Diverticulitis

 Iatrogenic (including endoscopic

perforation)

Ingested foreign body

Inflammation

Intussusception

Neoplasms

Obstruction

Peptic ulcer disease

Strangulated hernia

 Vascular (including ischemia or

embolus)

Perforation or leakage of other organs

 Biliary leakage (e.g., after liver

biopsy)

Cholecystitis

Intraperitoneal bleeding

Pancreatitis

Salpingitis

 Traumatic or other rupture of urinary

bladder

Loss of peritoneal integrity

Intraperitoneal chemotherapy

 Iatrogenic (e.g., postoperative

foreign body)

Perinephric abscess

 Peritoneal dialysis or other

indwelling devices

Trauma

2517 Nutrient Requirements and Dietary Assessment CHAPTER 332

■ FURTHER READING

Andersson RE: Short-term complications and long-term morbidity

of laparoscopic and open appendicectomy in a national cohort. Br J

Surg 101:1135, 2014.

Buckius MT et al: Changing epidemiology of acute appendicitis in

the United States: Study period 1993–2008. J Surg Res 175:185, 2012.

CODA Collaborative: A randomized trial comparing antibiotics

with appendectomy for appendicitis. N Engl J Med 383:1907, 2020.

Di Saverio S et al: Diagnosis and treatment of acute appendicitis:

2020 update of the WSES Jerusalem guidelines. World J Emerg Surg

15:27, 2020.

Drake FT et al: Time to appendectomy and risk of perforation in acute

appendicitis. JAMA Surg 149:837, 2014.

Flum DR: Acute appendicitis—appendectomy of the “antibiotics first”

strategy. N Engl J Med 372:1937, 2015.

Ohle R et al: The Alvarado score for predicting acute appendicitis:

A systematic review. BMC Med 9:139, 2011.

Talan DA, DiSaverio S: Treatment of acute uncomplicated appendicitis.

N Engl J Med 385:1116, 2021.

Vons C et al: Amoxicillin plus clavulanic acid versus appendicectomy

for treatment of acute uncomplicated appendicitis: An open-label,

non-inferiority, randomised controlled trial. Lancet 377:1573, 2011.

Section 2 Nutrition

332 Nutrient Requirements

and Dietary Assessment

Johanna T. Dwyer

Nutrients are substances that are not synthesized in sufficient amounts

in the body and therefore must be supplied by the diet. Nutrient requirements for groups of healthy persons have been determined experimentally. The absence of essential nutrients leads to growth impairment,

organ dysfunction, and failure to maintain nitrogen balance or adequate

status of protein and other nutrients. For good health, we require energyproviding nutrients (protein, fat, and carbohydrate), vitamins, minerals,

and water. Requirements for organic nutrients include 9 essential amino

acids, several fatty acids, glucose, 4 fat-soluble vitamins, 10 water-soluble

vitamins, dietary fiber, and choline. Several inorganic substances, including 4 minerals, 7 trace minerals, 3 electrolytes, and the ultratrace elements,

must also be supplied by diet.

The amounts of essential nutrients required by individuals differ by

their age and physiologic state. Conditionally essential nutrients are not

required in the diet but must be supplied to certain individuals who do not

synthesize them in adequate amounts, such as those with genetic defects;

those with pathologies such as infection, disease, or trauma with nutritional implications; and developmentally immature infants. For example,

inositol, taurine, arginine, and glutamine may be needed by premature

infants. Many other organic and inorganic compounds that are present

in foods and dietary supplements, including pesticides, lead, phytochemicals, zoochemicals, and microbial products, may also have health effects.

■ ESSENTIAL NUTRIENT REQUIREMENTS

Energy For weight to remain stable, energy intake must match energy

output. The major components of energy output are resting energy

expenditure (REE) and physical activity; minor components include

the energy cost of metabolizing food (thermic effect of food, or specific

dynamic action) and shivering thermogenesis (e.g., cold-induced thermogenesis). The average energy intake is ~2600 kcal/d for American

men and ~1800 kcal/d for American women, although these estimates

vary with body size and activity level. Formulas for roughly estimating

REE are useful in assessing the energy needs of an individual whose

weight is stable. Thus, for males, REE = 900 + 10m, and for females,

REE = 700 + 7m, where m is mass in kilograms. The calculated REE is

then adjusted for physical activity level by multiplying by 1.2 for sedentary, 1.4 for moderately active, or 1.8 for very active individuals. The final

figure, the estimated energy requirement (EER), provides an approximation of total caloric needs in a state of energy balance for a person of a

certain age, sex, weight, height, and physical activity level. For further

discussion of energy balance in health and disease, see Chap. 334.

Protein Dietary protein consists of both essential and nonessential

amino acids that are required for protein synthesis. The nine essential

amino acids are histidine, isoleucine, leucine, lysine, methionine/

cystine, phenylalanine/tyrosine, threonine, tryptophan, and valine.

Certain amino acids, such as alanine, can also be used for energy and

gluconeogenesis. When energy intake is inadequate, protein intake

must be increased, because ingested amino acids are diverted into

pathways of glucose synthesis and oxidation. In extreme energy deprivation, protein-calorie malnutrition may ensue (Chap. 334).

For adults, the recommended dietary allowance (RDA) for protein

is ~0.8 g/kg desirable body mass per day, assuming that energy needs

are met and that the protein is of relatively high biologic value. Current

recommendations for a healthy diet call for at least 10–14% of calories

from protein. Most American diets provide at least those amounts. Biologic value tends to be highest for animal proteins, followed by proteins

from legumes (beans), cereals (rice, wheat, corn), and roots. Combinations of plant proteins that complement one another in their essential

amino acid profiles or combinations of animal and plant proteins can

increase biologic value and lower total protein intakes necessary to

meet requirements. In healthy people with adequate diets, the timing

of protein intake over the course of the day has little effect.

Protein needs increase during growth, pregnancy, lactation, and

rehabilitation after injury or undernutrition. Tolerance to dietary protein is decreased in renal insufficiency (with consequent uremia) and

in liver failure. Usual protein intakes can precipitate encephalopathy in

patients with cirrhosis of the liver.

Fat and Carbohydrate Fats are a concentrated source of energy

and constitute, on average, 34% of calories in U.S. diets. However, for

optimal health, fat intake should total no more than 30% of calories.

Saturated fat and trans fat should be limited to <10% of calories and

polyunsaturated fats to <10% of calories, with monounsaturated fats

accounting for the remainder of fat intake. At least 45–55% of total calories should be derived from carbohydrates. The brain requires ~100 g

of glucose per day for fuel; other tissues use ~50 g/d. Some tissues (e.g.,

brain and red blood cells) rely on glucose supplied either exogenously

or from muscle proteolysis. Over time, during hypocaloric states,

adaptations in carbohydrate needs are possible. Like fat (9 kcal/g), carbohydrate (4 kcal/g), and protein (4 kcal/g), alcohol (ethanol) provides

energy (7 kcal/g). However, it is not a nutrient.

Water For adults, 1–1.5 mL of water per kilocalorie of energy expenditure is sufficient under usual conditions to allow for normal variations

in physical activity, sweating, and solute load of the diet. Water losses

include 50–100 mL/d in the feces; 500–1000 mL/d by evaporation or

exhalation; and, depending on the renal solute load, ≥1000 mL/d in the

urine. If external losses increase, intakes must increase accordingly to

avoid underhydration. Fever increases water losses by ~200 mL/d per

°C; diarrheal losses vary but may be as great as 5 L/d in severe diarrhea.

Heavy sweating, vigorous exercise, and vomiting also increase water

losses. When renal function is normal and solute intakes are adequate,

the kidneys can adjust to increased water intake by excreting up to 18 L

of excess water per day (Chap. 381). However, obligatory urine outputs

can compromise hydration status when there is inadequate water intake

or when losses increase in disease or kidney damage.

Infants have high requirements for water because of their large surface area to volume ratios, their inability to communicate their thirst,

and the limited capacity of the immature kidney to handle high renal

2518 PART 10 Disorders of the Gastrointestinal System

solute loads. Increased water needs during pregnancy are ~30 mL/d.

During lactation, milk production increases daily water requirements so

that ~1000 mL of additional water is needed, or 1 mL for each milliliter

of milk produced. Special attention must also be paid to the water needs

of the elderly, who have reduced total-body water and blunted thirst

sensation and are more likely to be taking medications such as diuretics.

Other Nutrients See Chap. 333 for detailed descriptions of vitamins and minerals.

■ DIETARY REFERENCE INTAKES AND RDAS

Fortunately, human life and well-being can be maintained within a

fairly wide range with most nutrient intakes. However, the capacity

for adaptation is not infinite—too much, as well as too little, intake

of a nutrient can have adverse effects or alter the health benefits conferred by another nutrient. Therefore, benchmark recommendations

regarding nutrient intakes have been developed to guide clinical practice. These quantitative estimates of nutrient intakes are collectively

referred to in the United States and Canada as the dietary reference

intakes (DRIs). The DRIs supplanted the RDAs—the single reference

values used in the United States until the early 1990s. DRIs include an

estimated average requirement (EAR) for nutrients as well as other reference values used for dietary planning: the RDA, the adequate intake

(AI), the chronic disease risk reduction intake (CDRR), and the tolerable upper level (UL). The DRIs also include acceptable macronutrient

distribution ranges (AMDRs) for protein, fat, and carbohydrate. The

current DRIs for vitamins and elements are provided in Tables 332-1

and 332-2, respectively. Table 332-3 provides DRIs for water and

macronutrients. EERs are discussed in Chap. 334 on energy balance

in health and disease.

Estimated Average Requirement (EAR) When florid manifestations of the classic dietary-deficiency diseases such as rickets (deficiency of vitamin D and calcium), scurvy (deficiency of vitamin C),

xerophthalmia (deficiency of vitamin A), and protein-calorie malnutrition were common, nutrient adequacy was inferred from the absence

of their clinical deficiency signs. Later, biochemical and other changes

were used that became evident long before the deficiency was clinically apparent. Consequently, criteria of adequacy are now based on

biologic markers when they are available. Priority is given to sensitive

biochemical, physiologic, or behavioral tests that reflect early changes

in regulatory processes; maintenance of body stores of nutrients; or, if

available, the amount of a nutrient that minimizes the risk of chronic

degenerative disease. Current efforts focus on this last variable, but

relevant markers often are not available, and the long time lags between

intake and disease outcomes further complicate the picture.

The types of evidence and criteria used to establish nutrient requirements vary by nutrient, age, and physiologic group. The EAR is the

amount of a nutrient estimated to be adequate for half of the healthy

individuals of a specific age and sex. It is not an effective estimate of

nutrient adequacy in individuals because it is a median requirement for

a group; 50% of individuals in a group fall below the requirement and

50% fall above it. Thus, a person with a usual intake at the EAR has a

50% risk of inadequate intake. For these reasons, the other standards

described below are more useful for clinical purposes.

Recommended Dietary Allowances The RDA, the nutrient

intake goal for planning diets of individuals, is the average daily dietary

intake level that meets the nutrient requirements of nearly all healthy

persons of a specific sex, age, life stage, or physiologic condition (e.g.,

pregnancy or lactation). It is defined statistically as two standard deviations above the EAR to ensure that the needs of any given individual

are met. An online tool, available at https://www.nal.usda.gov/fnic/

dri-calculator/, allows health professionals to calculate individualized daily nutrient recommendations for dietary planning based on

the DRIs. The RDAs are used to formulate food guides such as the

U.S. Department of Agriculture (USDA) MyPlate Plan for individuals (https://www.choosemyplate.gov/resources/MyPlatePlan), to create

food-exchange lists for therapeutic diet planning, and as a standard

for describing the nutritional content of foods and nutrient-containing

dietary supplements on labels.

The risk of dietary inadequacy increases as one’s intake falls below

the RDA. However, the RDA is an overly generous criterion for evaluating nutrient adequacy. For example, by definition, the RDA exceeds

the actual requirements of all but ~2–3% of the population. Therefore,

many people whose intake falls below the RDA are still getting enough

of the nutrient. On food labels, the nutrient content in a food is stated

by weight or as a percentage of the daily value (DV), a variant of the

RDA used on the nutrition facts panel that, for an adult, represents the

highest RDA for an adult consuming 2000 kcal.

Adequate Intake (AI) It is not possible to set an RDA for some

nutrients that lack an established EAR. In this circumstance, the AI is

based on observed or experimentally determined approximations of

nutrient intakes in healthy people. In the DRIs, AIs rather than RDAs

are proposed for nutrients consumed by infants (up to age 1 year) as

well as for chromium, fluoride, manganese, sodium, potassium, pantothenic acid, biotin, choline, and water consumed by persons of all ages.

Tolerable Upper Levels (UL) Healthy individuals gain no established benefit from consuming nutrient levels above the RDA or AI.

In fact, excessive nutrient intake can disturb body functions and cause

acute, progressive, or permanent disabilities. The tolerable UL is the

highest level of chronic (usually daily) nutrient intake that is unlikely to

pose a risk of adverse health effects for most of the population. Data on

the adverse effects of large amounts of many nutrients are unavailable

or too limited to establish a UL. Therefore, the lack of a UL does not

mean that the risk of adverse effects from high intake is nonexistent.

Nutrient levels in commonly eaten foods rarely exceed the UL. However, very highly fortified foods and dietary supplements provide more

concentrated amounts of nutrients per serving and thus pose a potential risk of toxicity. Dietary supplements are labeled with Supplement

Facts that express the amount of nutrients present in absolute units or

as the percentage of the DV provided per recommended serving size.

Total nutrient intakes, including that in foods, supplements, and overthe-counter medications (e.g., antacids), should not exceed RDA levels.

Chronic Disease Risk Reduction Intake (CDRR) This is the

level above which a reduction in intake is expected to lower chronic

disease risk. For example, the sodium CDRR for adults is 2300 mg/d,

and this is the lowest level of intake for which there is sufficiently

strong evidence to characterize a CDRR. Three is no CDRR for potassium or other nutrients, but the AI for potassium has been reduced to

2500 mg/d from a higher prior level. At present, population recommendations for CDRR are not available for other nutrients.

Acceptable Macronutrient Distribution Ranges (AMDRs)

AMDRs are not experimentally determined; rather, they are rough

ranges for energy-providing macronutrient intakes (protein, carbohydrate, and fat) that the National Academy of Medicine’s (formerly

Institute of Medicine [IOM]) Food and Nutrition Board considers to

be healthful. These ranges are 10–35% of calories for protein, 20–35%

of calories for fat, and 45–65% of calories for carbohydrate. Alcohol,

which also provides energy, is not a nutrient; therefore, no recommendations are provided.

■ FACTORS ALTERING NUTRIENT NEEDS

The DRIs are affected by age, sex, growth rate, pregnancy, lactation,

physical activity level, concomitant diseases, drugs, and dietary composition. If requirements for nutrient sufficiency are close to intake levels

indicating excess of a nutrient, dietary planning is difficult.

Physiologic Factors Growth, strenuous physical activity, pregnancy, and lactation all increase needs for energy and several essential

nutrients. Energy needs rise during pregnancy due to fetal growth

demands and increased energy required for milk production during

lactation. Energy needs decrease with loss of lean body mass, the major

determinant of REE. The energy needs of older persons, especially

those aged >70 years, tend to be lower than those of younger persons

because lean tissue, physical activity, and health often decline with age.

Dietary Composition Dietary composition affects the biologic

availability and use of nutrients. For example, iron absorption may be

2519 Nutrient Requirements and Dietary Assessment 332 CHAPTER

TABLE 332-1 Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes for Vitamins

LIFE-STAGE GROUP

VITAMIN A

(lg/d)a

VITAMIN C

(mg/d)

VITAMIN D

(lg/d)b,c

VITAMIN E

(mg/d)d

VITAMIN K

(lg/d)

THIAMIN

(mg/d)

RIBOFLAVIN

(mg/d)

NIACIN

(mg/d)e

VITAMIN B6 (mg/d) FOLATE (lg/d)F VITAMIN B12 (lg/d) PANTOTHENIC ACID (mg/d) BIOTIN (lg/d) CHOLINE (mg/d)G

Infants

Birth to 6 mo 400* 40* 10 4* 2.0* 0.2* 0.3* 2* 0.1* 65* 0.4* 1.7* 5* 125*

6–12 mo 500* 50* 10 5* 2.5* 0.3* 0.4* 4* 0.3* 80* 0.5* 1.8* 6* 150*

Children

1–3 y 300 15 15 6 30* 0.5 0.5 6 0.5 150 0.9 2* 8* 200*

4–8 y 400 25 15 7 55* 0.6 0.6 8 0.6 200 1.2 3* 12* 250*

Males

9–13 y 600 45 15 11 60* 0.9 0.9 12 1.0 300 1.8 4* 20* 375*

14–18 y 900 75 15 15 75* 1.2 1.3 16 1.3 400 2.4 5* 25* 550*

19–30 y 900 90 15 15 120* 1.2 1.3 16 1.3 400 2.4 5* 30* 550*

31–50 y 900 90 15 15 120* 1.2 1.3 16 1.3 400 2.4 5* 30* 550*

51–70 y 900 90 15 15 120* 1.2 1.3 16 1.7 400 2.4h 5* 30* 550*

>70 y 900 90 20 15 120* 1.2 1.3 16 1.7 400 2.4h 5* 30* 550*

Females

9–13 y 600 45 15 11 60* 0.9 0.9 12 1.0 300 1.8 4* 20* 375*

14–18 y 700 65 15 15 75* 1.0 1.0 14 1.2 400i 2.4 5* 25* 400*

19–30 y 700 75 15 15 90* 1.1 1.1 14 1.3 400i 2.4 5* 30* 425*

31–50 y 700 75 15 15 90* 1.1 1.1 14 1.3 400i 2.4 5* 30* 425*

51–70 y 700 75 15 15 90* 1.1 1.1 14 1.5 400 2.4h 5* 30* 425*

>70 y 700 75 20 15 90* 1.1 1.1 14 1.5 400 2.4h 5* 30* 425*

Pregnant Women

14–18 y 750 80 15 15 75* 1.4 1.4 18 1.9 600j 2.6 6* 30* 450*

19–30 y 770 85 15 15 90* 1.4 1.4 18 1.9 600j 2.6 6* 30* 450*

31–50 y 770 85 15 15 90* 1.4 1.4 18 1.9 600j 2.6 6* 30* 450*

Lactating Women

14–18 y 1200 115 15 19 75* 1.4 1.6 17 2.0 500 2.8 7* 35* 550*

19–30 y 1300 120 15 19 90* 1.4 1.6 17 2.0 500 2.8 7* 35* 550*

31–50 y 1300 120 15 19 90* 1.4 1.6 17 2.0 500 2.8 7* 35* 550*

Note: This table (taken from the DRI reports; see www.nap.edu) presents recommended dietary allowances (RDAs) in bold type and adequate intakes (AIs) in ordinary type followed by an asterisk (*). An RDA is the average daily dietary

intake level sufficient to meet the nutrient requirements of nearly all healthy individuals (97–98%) in a group. The RDA is calculated from an estimated average requirement (EAR). If sufficient scientific evidence is not available to establish

an EAR and thus to calculate an RDA, an AI is usually developed. For healthy breast-fed infants, an AI is the mean intake. The AI for other life-stage and sex-specific groups is believed to cover the needs of all healthy individuals in those

groups, but lack of data or uncertainty in the data makes it impossible to specify with confidence the percentage of individuals covered by this intake.

aAs retinol activity equivalents (RAEs). 1 RAE = 1 μg retinol, 12 μg β-carotene, 24 μg α-carotene, or 24 μg β-cryptoxanthin. The RAE for dietary provitamin A carotenoids is twofold greater than the retinol equivalent (RE), whereas the RAE for

preformed vitamin A is the same as the RE. bAs cholecalciferol. 1 μg cholecalciferol = 40 IU vitamin D. cUnder the assumption of minimal sunlight. dAs α-tocopherol. α-Tocopherol includes RRR-α-tocopherol, the only form of α-tocopherol

that occurs naturally in foods, and the 2R-stereoisomeric forms of α-tocopherol (RRR-, RSR-, RRS-, and RSS-α-tocopherol) that occur in fortified foods and supplements. It does not include the 2S-stereoisomeric forms of α-tocopherol (SRR-,

SSR-, SRS-, and SSS-α-tocopherol) also found in fortified foods and supplements. eAs niacin equivalents (NEs). 1 mg of niacin = 60 mg of tryptophan; 0–6 months = preformed niacin (not NE). fAs dietary folate equivalents (DFEs). 1 DFE =

1 μg food folate = 0.6 μg of folic acid from fortified food or as a supplement consumed with food = 0.5 μg of a supplement taken on an empty stomach. gAlthough AIs have been set for choline, there are few data to assess whether a dietary

supply of choline is needed at all stages of the life cycle, and it may be that the choline requirement can be met by endogenous synthesis at some of these stages. hBecause 10–30% of older people may malabsorb food-bound B12, it is

advisable for those >50 years of age to meet their RDA mainly by consuming foods fortified with B12 or a supplement containing B12. iIn view of evidence linking inadequate folate intake with neural tube defects in the fetus, it is recommended

that all women capable of becoming pregnant consume 400 μg of folate from supplements or fortified foods in addition to intake of food folate from a varied diet. j It is assumed that women will continue consuming 400 μg from supplements

or fortified food until their pregnancy is confirmed and they enter prenatal care, which ordinarily occurs after the end of the periconceptional period—the critical time for formation of the neural tube.

Source: National Academies of Sciences, Engineering, and Medicine. 2019. Dietary Reference Intakes for Sodium and Potassium. https://doi.org/10.17226/25353. Adapted and reproduced with permission from the National Academy of

Sciences, Courtesy of the National Academies.

Disorders of the Gastrointestinal System PART 10

2520

TABLE 332-2 Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes for Elements

LIFE-STAGE

GROUP

CALCIUM

(mg/d)

CHROMIUM

(lg/d)

COPPER

(lg/d)

FLUORIDE

(mg/d)

IODINE

(lg/d)

IRON

(mg/d)

MAGNESIUM

(mg/d)

MANGANESE

(mg/d)

MOLYBDENUM

(lg/d)

PHOSPHORUS

(mg/d)

SELENIUM

(lg/d)

ZINC

(mg/d)

POTASSIUM

(g/d)

SODIUM

(g/d)

CHLORIDE

(g/d)

Infants

Birth to 6 mo 200* 0.2* 200* 0.01* 110* 0.27* 30* 0.003* 2* 100* 15* 2* 0.4* 0.12* 0.18*

6–12 mo 260* 5.5* 220* 0.5* 130* 11 75* 0.6* 3* 275* 20* 3 0.7* 0.37* 0.57*

Children

1–3 y 700 11* 340 0.7* 90 7 80 1.2* 17 460 20 3 3.0* 1.0* 1.5*

4–8 y 1000 15* 440 1* 90 10 130 1.5* 22 500 30 5 3.8* 1.2* 1.9*

Males

9–13 y 1300 25* 700 2* 120 8 240 1.9* 34 1250 40 8 4.5* 1.5* 2.3*

14–18 y 1300 35* 890 3* 150 11 410 2.2* 43 1250 55 11 4.7* 1.5* 2.3*

19–30 y 1000 35* 900 4* 150 8 400 2.3* 45 700 55 11 4.7* 1.5* 2.3*

31–50 y 1000 35* 900 4* 150 8 420 2.3* 45 700 55 11 4.7* 1.5* 2.3*

51–70 y 1000 30* 900 4* 150 8 420 2.3* 45 700 55 11 4.7* 1.3* 2.0*

>70 y 1200 30* 900 4* 150 8 420 2.3* 45 700 55 11 4.7* 1.2* 1.8*

Females

9–13 y 1300 21* 700 2* 120 8 240 1.6* 34 1250 40 8 4.5* 1.5* 2.3*

14–18 y 1300 24* 890 3* 150 15 360 1.6* 43 1250 55 9 4.7* 1.5* 2.3*

19–30 y 1000 25* 900 3* 150 18 310 1.8* 45 700 55 8 4.7* 1.5* 2.3*

31–50 y 1000 25* 900 3* 150 18 320 1.8* 45 700 55 8 4.7* 1.5* 2.3*

51–70 y 1200 20* 900 3* 150 8 320 1.8* 45 700 55 8 4.7* 1.3* 2.0*

>70 y 1200 20* 900 3* 150 8 320 1.8* 45 700 55 8 4.7* 1.2* 1.8*

Pregnant Women

14–18 y 1300 29* 1000 3* 220 27 400 2.0* 50 1250 60 12 4.7* 1.5* 2.3*

19–30 y 1000 30* 1000 3* 220 27 350 2.0* 50 700 60 11 4.7* 1.5* 2.3*

31–50 y 1000 30* 1000 3* 220 27 360 2.0* 50 700 60 11 4.7* 1.5* 2.3*

Lactating Women

14–18 y 1300 44* 1300 3* 290 10 360 2.6* 50 1250 70 13 5.1* 1.5* 2.3*

19–30 y 1000 45* 1300 3* 290 9 310 2.6* 50 700 70 12 5.1* 1.5* 2.3*

31–50 y 1000 45* 1300 3* 290 9 320 2.6* 50 700 70 12 5.1* 1.5* 2.3*

Note: This table (taken from the DRI reports; see www.nap.edu) presents recommended dietary allowances (RDAs) in bold type and adequate intakes (AIs) in ordinary type followed by an asterisk (*). An RDA is the average daily dietary

intake level sufficient to meet the nutrient requirements of nearly all healthy individuals (97–98%) in a group. The RDA is calculated from an estimated average requirement (EAR). If sufficient scientific evidence is not available to establish

an EAR and thus to calculate an RDA, an AI is usually developed. For healthy breast-fed infants, an AI is the mean intake. The AI for other life-stage and sex-specific groups is believed to cover the needs of all healthy individuals in those

groups, but lack of data or uncertainty in the data makes it impossible to specify with confidence the percentage of individuals covered by this intake.

Sources: National Academies of Sciences, Engineering, and Medicine. 2019. Dietary Reference Intakes for Sodium and Potassium. https://doi.org/10.17226/25353. Adapted and reproduced with permission from the National Academy of

Sciences, Courtesy of the National Academies.

2521 Nutrient Requirements and Dietary Assessment CHAPTER 332

impaired by large amounts of calcium or lead; likewise, non-heme iron

uptake may be impaired by a lack of ascorbic acid and amino acids in

the meal. Bodily protein may be decreased when essential amino acids

are not present in sufficient amounts—a rare scenario in U.S. diets.

Animal foods, such as milk, eggs, and meat, have high biologic values,

with most of the needed amino acids present in adequate amounts.

Plant proteins in corn (maize), soy, rice, and wheat have lower biologic

values and must be combined with other plant or animal proteins or

fortified with the amino acids that are deficient to achieve optimal use

by the body.

Route of Intake The RDAs apply only to oral intakes. When nutrients are administered parenterally, similar values can sometimes be

used for amino acids, glucose (carbohydrate), fats, sodium, chloride,

potassium, and most vitamins because their intestinal absorption rate

is nearly 100%. However, the oral bioavailability of most mineral elements may be only half that obtained by parenteral administration. For

some nutrients that are not readily stored in the body or that cannot be

stored in large amounts, timing of administration may also be important. For example, amino acids cannot be used for protein synthesis if

they are not supplied together; instead, they will be used for energy

production, although in healthy individuals eating adequate diets, the

distribution of protein intake over the course of the day has little effect

on health.

Disease Dietary deficiency diseases include protein-calorie malnutrition, iron-deficiency anemia, goiter (due to iodine deficiency),

rickets and osteomalacia (vitamin D deficiency), xeropthalmia

(vitamin A deficiency), megaloblastic anemia (vitamin B12 or folic

acid deficiency), scurvy (vitamin C/ascorbic acid deficiency), beriberi

(thiamin deficiency), and pellagra (niacin and tryptophan deficiency)

(Chaps. 333 and 334). Each deficiency disease is characterized by

imbalances at the cellular level between the supply of nutrients or

energy and the body’s nutritional needs for growth, maintenance, and

other functions. Imbalances and excesses in nutrient intakes are recognized as risk factors for certain chronic degenerative diseases, such

as saturated fat and cholesterol in coronary artery disease; sodium in

hypertension; obesity in hormone-dependent cancers (endometrial

and breast); and ethanol in alcoholism. Diet is only one of many risk

factors because the etiology and pathogenesis of these disorders are

multifactorial. Osteoporosis, for example, is associated with calcium

deficiency, sometimes secondary to vitamin D deficiency, as well as

TABLE 332-3 Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes for Total Water and Macronutrients

LIFE-STAGE

GROUP

TOTAL WATERa

(L/d)

CARBOHYDRATE

(g/d) TOTAL FIBER (g/d) FAT (g/d)

LINOLEIC ACID

(g/d)

`-LINOLENIC ACID

(g/d) PROTEINb

 (g/d)

Infants

Birth to 6 mo 0.7* 60* NDc 31* 4.4* 0.5* 9.1*

6–12 mo 0.8* 95* ND 30* 4.6* 0.5* 11.0

Children

1–3 y 1.3* 130 19* ND 7* 0.7* 13

4–8 y 1.7* 130 25* ND 10* 0.9* 19

Males

9–13 y 2.4* 130 31* ND 12* 1.2* 34

14–18 y 3.3* 130 38* ND 16* 1.6* 52

19–30 y 3.7* 130 38* ND 17* 1.6* 56

31–50 y 3.7* 130 38* ND 17* 1.6* 56

51–70 y 3.7* 130 30* ND 14* 1.6* 56

>70 y 3.7* 130 30* ND 14* 1.6* 56

Females

9–13 y 2.1* 130 26* ND 10* 1.0* 34

14–18 y 2.3* 130 26* ND 11* 1.1* 46

19–30 y 2.7* 130 25* ND 12* 1.1* 46

31–50 y 2.7* 130 25* ND 12* 1.1* 46

51–70 y 2.7* 130 21* ND 11* 1.1* 46

>70 y 2.7* 130 21* ND 11* 1.1* 46

Pregnant Women

14–18 y 3.0* 175 28* ND 13* 1.4* 71

19–30 y 3.0* 175 28* ND 13* 1.4* 71

31–50 y 3.0* 175 28* ND 13* 1.4* 71

Lactating Women

14–18 3.8* 210 29* ND 13* 1.3* 71

19–30 y 3.8* 210 29* ND 13* 1.3* 71

31–50 y 3.8* 210 29* ND 13* 1.3* 71

Note: This table (taken from the DRI reports; see www.nap.edu) presents recommended dietary allowances (RDAs) in bold type and adequate intakes (AIs) in ordinary type

followed by an asterisk (*

). An RDA is the average daily dietary intake level sufficient to meet the nutrient requirements of nearly all healthy individuals (97–98%) in a group.

The RDA is calculated from an estimated average requirement (EAR). If sufficient scientific evidence is not available to establish an EAR and thus to calculate an RDA, an AI

is usually developed. For healthy breast-fed infants, an AI is the mean intake. The AI for other life-stage and sex-specific groups is believed to cover the needs of all healthy

individuals in those groups, but lack of data or uncertainty in the data make it impossible to specify with confidence the percentage of individuals covered by this intake.

a

Total water includes all water contained in food, beverages, and drinking water. b

Based on grams of protein per kilogram of body weight for the reference body weight

(e.g., for adults: 0.8 g/kg body weight for the reference body weight). c

Not determined.

Source: National Academies of Sciences, Engineering, and Medicine. 2019. Dietary Reference Intakes for Sodium and Potassium. https://doi.org/10.17226/25353. Adapted

and reproduced with permission from the National Academy of Sciences, Courtesy of the National Academies.

2522 PART 10 Disorders of the Gastrointestinal System

with environment-related risk factors (e.g., smoking, sedentary lifestyle), physiology (e.g., estrogen deficiency), genetic determinants (e.g.,

defects in collagen metabolism), and drug use (chronic steroids and

aromatase inhibitors) (Chap. 411).

■ DIETARY ASSESSMENT

Nutrition assessment in clinical situations is an iterative process that

involves (1) screening for malnutrition, (2) assessing the diet and other

data to establish either the absence or the presence of malnutrition and

its possible causes, (3) planning and implementing the most appropriate nutritional therapy, and (4) reassessing intakes to make sure that

they have been consumed. Some disease states affect the bioavailability,

requirements, use, or excretion of specific nutrients. In these circumstances, specific measurements of various nutrients or their biomarkers

may be required to ensure adequate replacement (Chap. 333).

Most health care facilities have nutrition-screening processes in

place for identifying possible malnutrition after hospital admission.

Nutritional screening is required by The Joint Commission, which

accredits and certifies health care organizations in the United States.

However, no universally recognized or validated standards exist. The

factors that are usually assessed include abnormal weight for height

or body mass index (e.g., BMI <19 or >25); reported weight change

(involuntary loss or gain of >5 kg in the past 6 months) (Chap. 47);

diagnoses with known nutritional implications (e.g., metabolic disease,

any disease affecting the gastrointestinal tract, alcoholism); present

therapeutic dietary prescription; chronic poor appetite; presence of

chewing and swallowing problems or major food intolerances; need for

assistance with preparing or shopping for food, eating, or other aspects

of self-care; and social isolation. The nutritional status of hospitalized

patients should be reassessed periodically—at least once every week.

A more complete dietary assessment is indicated for patients who

exhibit a high risk of or frank malnutrition on nutritional screening.

The type of assessment varies with the clinical setting, the severity of

the patient’s illness, and the stability of the patient’s condition.

Acute-Care Settings In acute-care settings, anorexia, various

other diseases, test procedures, and medications can compromise

dietary intake. Under such circumstances, the goal is to identify

and avoid inadequate intake and to assure appropriate alimentation.

Dietary assessment focuses on what patients are currently eating,

whether or not they are able and willing to eat, and whether or not

they experience any problems with eating. Dietary intake assessment is

based on information from observed intakes; medical records; history;

clinical examination; and anthropometric, biochemical, and functional

status evaluations. The objective is to gather enough information to

establish the likelihood of malnutrition due to poor dietary intake or

other causes in order to assess whether nutritional therapy is indicated

(Chap. 335).

Simple observations may suffice to suggest inadequate oral intake.

These include dietitians’ and nurses’ notes; observation of a patient’s

frequent refusal to eat or the amount of food eaten on trays; the frequent performance of tests and procedures that are likely to cause

meals to be skipped; adherence to nutritionally inadequate diet orders

(e.g., clear liquids or full liquids) for more than a few days; the occurrence of fever, gastrointestinal distress, vomiting, diarrhea, or a comatose state; and the presence of diseases or use of treatments that involve

any part of the alimentary tract. Acutely ill patients with diet-related

diseases such as diabetes need assessment because an inappropriate

diet may exacerbate these conditions and adversely affect other therapies. Abnormal biochemical values (serum albumin levels <35 g/L

[<3.5 mg/dL]; serum cholesterol levels <3.9 mmol/L [<150 mg/dL]) are

nonspecific but may indicate a need for further nutritional assessment.

Most therapeutic diets offered in hospitals are calculated to meet

individual nutrient requirements and the RDA if they are eaten. Exceptions include clear liquids, some full-liquid diets, and test diets (such as

those adhered to in preparation for gastrointestinal procedures), which

are inadequate for several nutrients and should not be used, if possible,

for >24 h. However, because as much as half of the food served to hospitalized patients is not eaten, it cannot be assumed that the intakes of

hospitalized patients are adequate. Dietary assessment should compare

how much and what kinds of food the patient has consumed with the

diet that has been provided. Major deviations in intakes of energy, protein, fluids, or other nutrients of special concern for the patient’s illness

should be noted and corrected, especially for long-staying patients.

Nutritional monitoring is especially important for patients who are

very ill and who have extended lengths of hospital stay. Patients who

are fed by enteral and parenteral routes also require special nutritional

assessment and monitoring by physicians and/or dietitians with certification in nutritional support (Chap. 335).

Ambulatory Settings The aim of dietary assessment in the

outpatient setting is to determine whether or not the patient’s usual

diet is a health risk in itself or if it contributes to existing chronic

disease–related problems. Dietary assessment also provides the basis

for planning a diet that fulfills therapeutic goals while ensuring patient

adherence. The outpatient’s dietary assessment should review the

adequacy of present and usual food intakes, including vitamin and

mineral supplements, oral nutritional supplements, medical foods,

other dietary supplements, medications, and alcohol, because all of

these may affect the patient’s nutritional status. The assessment should

focus on the dietary constituents that are most likely to be involved or

compromised by a specific diagnosis as well as on any comorbidities

that are present. More than 1 day’s intake should be reviewed to provide a better representation of the usual diet, upon which personalized

dietary recommendations can be based.

There are many ways to assess the adequacy of a patient’s habitual

diet. These include use of a food guide, a food-exchange list, a diet history, or a food-frequency questionnaire. A commonly used food guide

for healthy persons is the USDA’s Choose My Plate, which is useful as

a rough guide for avoiding inadequate intakes of essential nutrients as

well as likely excesses in the amounts of fat (especially saturated and

trans fats), sodium, sugar, and alcohol consumed (Table 332-4). The

Choose My Plate graphic emphasizes a balance between calories and

TABLE 332-4 Choose My Plate: A Guide to Individualized

Dietary Planning

EXAMPLES OF STANDARD PORTION SIZES AT

INDICATED ENERGY LEVEL

DIETARY FACTOR, UNIT

OF MEASURE (ADVICE)

LOWER:

1600 kcal

MODERATE:

2200 kcal

HIGHER:

2800 kcal

Fruits, cups (Focus on

fruits.)

1.5 2 2.5

Vegetables, cups (Vary

vegetables.)

2 3 3.5

Grains, oz eq (Make

at least half of grains

whole.)a

5 7 10

Protein foods, oz eq

(Go lean with protein.)b

5 6 7

Dairy, cups or ozc

 (Choose

calcium-rich foods.)

3 3 3

“Empty” calories, kcald 120 260 400

Sodium, mg <2300 at all

energy levels

Physical activity, min At least 150 min vigorous physical activity per week

at all energy levels

Note: Oils (formerly listed with portions of 5, 6, and 8 teaspoons for the lower,

moderate, and higher energy levels, respectively) are no longer singled out in

Choose My Plate, but rather are included in the empty calories/added sugar

category with SOFAS (calories from solid fats and added sugars). The limit is

the remaining number of calories in each food pattern above after intake of the

recommended amounts of the nutrient-dense foods.

a

For example, 1 serving equals 1 slice bread, 1 cup ready-to-eat cereal, or 0.5 cup

cooked rice, pasta, or cooked cereal. b

For example, 1 serving equals 1 oz lean meat,

poultry, or fish; 1 egg; 1 tablespoon peanut butter; 0.25 cup cooked dry beans; or

0.5 oz nuts or seeds. c

For example, 1 serving equals 1 cup milk or yogurt, 1.5 oz

natural cheese, or 2 oz processed cheese. d

Formerly called “discretionary calorie

allowance.” Portions are calculated as the number of calories remaining after all of

the above allotments are accounted for.

Abbreviation: oz eq, ounce equivalent.

Source: Data from U.S. Department of Agriculture (http://www.Choosemyplate.gov).